全文获取类型
收费全文 | 528616篇 |
免费 | 4156篇 |
国内免费 | 1281篇 |
专业分类
化学 | 269048篇 |
晶体学 | 7645篇 |
力学 | 25990篇 |
综合类 | 17篇 |
数学 | 67779篇 |
物理学 | 163574篇 |
出版年
2021年 | 5035篇 |
2020年 | 5477篇 |
2019年 | 6221篇 |
2018年 | 8413篇 |
2017年 | 8560篇 |
2016年 | 11625篇 |
2015年 | 6176篇 |
2014年 | 10437篇 |
2013年 | 23485篇 |
2012年 | 18336篇 |
2011年 | 21790篇 |
2010年 | 16420篇 |
2009年 | 16279篇 |
2008年 | 20657篇 |
2007年 | 20508篇 |
2006年 | 18612篇 |
2005年 | 16620篇 |
2004年 | 15468篇 |
2003年 | 13955篇 |
2002年 | 13847篇 |
2001年 | 14728篇 |
2000年 | 11343篇 |
1999年 | 8752篇 |
1998年 | 7600篇 |
1997年 | 7470篇 |
1996年 | 6928篇 |
1995年 | 6257篇 |
1994年 | 6264篇 |
1993年 | 6017篇 |
1992年 | 6375篇 |
1991年 | 6865篇 |
1990年 | 6577篇 |
1989年 | 6486篇 |
1988年 | 6321篇 |
1987年 | 6132篇 |
1986年 | 5871篇 |
1985年 | 7408篇 |
1984年 | 7769篇 |
1983年 | 6532篇 |
1982年 | 6817篇 |
1981年 | 6326篇 |
1980年 | 6003篇 |
1979年 | 6504篇 |
1978年 | 6741篇 |
1977年 | 6629篇 |
1976年 | 6586篇 |
1975年 | 6302篇 |
1974年 | 6129篇 |
1973年 | 6424篇 |
1972年 | 4706篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
901.
This is a write-up on the foundation of the Sobolev Institute of Mathematics in 1957. 相似文献
902.
903.
904.
A nonlinear pulse systems with a time-variant continuous linear part is considered. A method for synthesizing an output-feedback robust stabilizing control is suggested. 相似文献
905.
A. Puiu G. Giubileo G. Addolorato L. Revelli G. Gasbarrini R. Bellantone A. D’Amore C. P. Lombardi C. Carrozza 《Laser Physics》2007,17(4):448-452
Nowadays, there is high demand for sensitive gas sensors both for human and environmental monitoring. This paper deals with a high-resolution (0.2 ppb) laser-based photoacoustic spectroscopic system realized at ENEA Frascati, Italy, applied for monitoring stress in scuba divers during sustained immersion by analyzing breath samples. Blood tests and psychometric tests for scuba divers were performed at Catholic University in Rome. Results will be reported and discussed. 相似文献
906.
907.
908.
The use of liquid fuels such as kerosene is of interest for the pulse detonation engine (PDE). Within this context, the aim
of this work, which is a preliminary study, was to show the feasibility to initiate a detonation in air with liquid-fuel pyrolysis
products, using energies and dimensions of test facility similars to those of PDEs. Therefore, two liquids fuels have been
compared, JP10, which is a synthesis fuel generally used in the field of missile applications, and decane, which is one of
the major components of standard kerosenes (F-34, Jet A1, ...). The thermal degradation of these fuels was studied with two
pyrolysis processes, a batch reactor and a flow reactor. The temperatures varied from 600°C to 1,000°C and residence times
for the batch reactor and the flow reactor were, respectively, between 10–30 s and 0.1–2 s. Subsequently, the detonability
of synthetic gaseous mixtures, which was a schematisation of the decomposition state after the pyrolysis process, has been
studied. The detonability study, regarding nitrogen dilution and equivalence ratio, was investigated in a 50 mm-diameter,
2.5 m-long detonation tube. These dimensions are compatible with applications in the aircraft industry and, more particularly,
in PDEs. Therefore, JP10 and decane were compared to choose the best candidate for liquid-fuel PDE studies.
This paper was based on work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Montreal, Canada, July 31 – August 5, 2005. 相似文献
909.
Based on the results of fracture in polymethyl methacrylate and a spheroplastic using a magnetic-pulse setup, the specific work of the formation of a new surface is estimated, which is similar to Griffith’s surface energy for quasi-static tests. The value obtained is greater than the corresponding value determined from the quasi-static tests by an order of magnitude and tends to increase as the loading time decreases. 相似文献
910.
Studies in the field of radical copolymerization of N-vinylsuccinimide were summarized, theeffect of the reaction medium on the process kinetics was examined. Factors governing the relative activity ofthe monomers were revealed, and ways to control the reactivity of N-vinylsuccinimide in binary copolymerizations were suggested. 相似文献