全文获取类型
收费全文 | 1706篇 |
免费 | 190篇 |
国内免费 | 86篇 |
专业分类
航空 | 982篇 |
航天技术 | 253篇 |
综合类 | 113篇 |
航天 | 634篇 |
出版年
2024年 | 14篇 |
2023年 | 43篇 |
2022年 | 44篇 |
2021年 | 48篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 36篇 |
2017年 | 29篇 |
2016年 | 37篇 |
2015年 | 23篇 |
2014年 | 65篇 |
2013年 | 34篇 |
2012年 | 58篇 |
2011年 | 56篇 |
2010年 | 59篇 |
2009年 | 42篇 |
2008年 | 55篇 |
2007年 | 78篇 |
2006年 | 70篇 |
2005年 | 102篇 |
2004年 | 69篇 |
2003年 | 61篇 |
2002年 | 45篇 |
2001年 | 53篇 |
2000年 | 57篇 |
1999年 | 50篇 |
1998年 | 67篇 |
1997年 | 46篇 |
1996年 | 49篇 |
1995年 | 74篇 |
1994年 | 52篇 |
1993年 | 37篇 |
1992年 | 40篇 |
1991年 | 45篇 |
1990年 | 25篇 |
1989年 | 35篇 |
1988年 | 29篇 |
1987年 | 29篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1983年 | 30篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有1982条查询结果,搜索用时 78 毫秒
231.
分析研究企业安全管理工作的法则与效应、运行模式和影响因素,提出企业安全管理工作的系统建设思路,并对安全管理工作中经验与体会作了说明。 相似文献
232.
A380之大对其起落架控制系统设计提出了很高的要求。本文在分析了A380飞机起落架的转弯控制、刹车控制、收放控制、胎压和油压监控等子系统的基础上,对我国大飞机起落架控制系统的研制提出了自己的看法。 相似文献
233.
234.
235.
236.
孙义生 《西安航空技术高等专科学校学报》1982,(2)
我是六九年到航校,七八年春调做学生辅导员工作的,在踏入教育战线四年多的时间里,由于党组织的培养、教育,同志们的热情帮助和大力支持,以及学生的紧密配合,自己在工作中取得了一定的成绩,使所带的班级成为学校比较先进的集体,使大部分同学在德、智、体三方面得到了发展。实践使我深深懂得了加强学生政治思想工作的重要意义及积极作用,下面就我做学生政治思想工作的点滴体会作以汇报。 相似文献
237.
We provide a scientific rationale for the astrobiological investigation of Mars. We suggest that, given practical constraints, the most promising locations for the search for former life on Mars are palaeolake craters and the evaporite deposits that may reside within them. We suggest that Raman spectroscopy offers a promising tool for the detection of evidence of former (or extant) biota on Mars. In particular, we highlight the detection of hopanoids as long-lived bacterial cell wall products and photosynthetic pigments as the most promising targets. We further suggest that Raman spectroscopy as a fibre optic-based instrument lends itself to flexible planetary deployment. 相似文献
238.
A commonly accepted view is that life began in a marine environment, which would imply the presence of inorganic ions such as Na+, Cl-, Mg2+, Ca2+, and Fe2+. We have investigated two processes relevant to the origin of life--membrane self-assembly and RNA polymerization--and established that both are adversely affected by ionic solute concentrations much lower than those of contemporary oceans. In particular, monocarboxylic acid vesicles, which are plausible models of primitive membrane systems, are completely disrupted by low concentrations of divalent cations, such as magnesium and calcium, and by high sodium chloride concentrations as well. Similarly, a nonenzymatic, nontemplated polymerization of activated RNA monomers in ice/eutectic phases (in a solution of low initial ionic strength) yields oligomers with > 80% of the original monomers incorporated, but polymerization in initially higher ionic strength aqueous solutions is markedly inhibited. These observations suggest that cellular life may not have begun in a marine environment because the abundance of ionic inorganic solutes would have significantly inhibited the chemical and physical processes that lead to self-assembly of more complex molecular systems. 相似文献
239.
Avdeev S Bidoli V Casolino M De Grandis E Furano G Morselli A Narici L De Pascale MP Picozza P Reali E Sparvoli R Boezio M Carlson P Bonvicini W Vacchi A Zampa N Castellini G Fuglesang C Galper A Khodarovich A Ozerov Y Popov A Vavilov N Mazzenga G Ricci M Sannita WG Spillantini P 《Acta Astronautica》2002,50(8):511-525
The phenomenon of light flashes (LF) in eyes for people in space has been investigated onboard Mir. Data on particles hitting the eye have been collected with the SilEye detectors, and correlated with human observations. It is found that a nucleus in the radiation environment of Mir has roughly a 1% probability to cause an LF, whereas the proton probability is almost three orders of magnitude less. As a function of LET, the LF probability increases above 10 keV/micrometer, reaching about 5% at around 50 keV/micrometer. 相似文献
240.
This new multi-disciplinary medical experimentation center provides the ideal scientific, medical and technical environment required for research programs and to prepare international space station Alpha (ISSA) missions, where space and healthcare industries can share their expertise. Different models are available to simulate space flight effects (bed-rest, confinement,...). This is of particular interest for research in Human psychology, physiology, physiopathology and ergonomics, validation of biomedical materials and procedures, testing of drugs, and other healthcare related products. This clinical research facility (CRF) provides valuable services in various fields of Human research requiring healthy volunteers. CRF is widely accessible to national and international, scientific, medical and industrial organisations. Furthermore, users have at their disposal the multi-disciplinary skills of MEDES staff and all MEDES partners on a single site. 相似文献