首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   203031篇
  免费   1285篇
  国内免费   428篇
化学   104707篇
晶体学   3391篇
力学   10271篇
综合类   10篇
数学   21843篇
物理学   64522篇
  2021年   1970篇
  2020年   2008篇
  2019年   2567篇
  2018年   3657篇
  2017年   3670篇
  2016年   4810篇
  2015年   2342篇
  2014年   4297篇
  2013年   8579篇
  2012年   6829篇
  2011年   8040篇
  2010年   6456篇
  2009年   6640篇
  2008年   7638篇
  2007年   7595篇
  2006年   6697篇
  2005年   5918篇
  2004年   5639篇
  2003年   5160篇
  2002年   5152篇
  2001年   5604篇
  2000年   4135篇
  1999年   3132篇
  1998年   2698篇
  1997年   2757篇
  1996年   2541篇
  1995年   2210篇
  1994年   2327篇
  1993年   2225篇
  1992年   2523篇
  1991年   2644篇
  1990年   2553篇
  1989年   2623篇
  1988年   2531篇
  1987年   2551篇
  1986年   2412篇
  1985年   3034篇
  1984年   3105篇
  1983年   2596篇
  1982年   2563篇
  1981年   2529篇
  1980年   2336篇
  1979年   2709篇
  1978年   2674篇
  1977年   2872篇
  1976年   2873篇
  1975年   2664篇
  1974年   2603篇
  1973年   2711篇
  1972年   2087篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A method of calculating the partial characteristics of radiation absorption by the components of light-scattering disperse layers is proposed. This method is based on statistical modeling (the Monte Carlo method). The absorptivities of photographic gelatin and silver bromide microcrystals and the corresponding distributions of the absorbed energy over the layer thickness are calculated using the example of an interaction between actinic radiation and silver halide photographic layers in the wavelength range λ=200–440 nm. The following structural parameters of the photographic layer are used in the calculation: the mean size of emulsion crystals d=0.5 μm; the polydispersity C V =25%; the volume concentrations C V =10, 20, and 30%; and the thickness of the emulsion layer H=10 μm.  相似文献   
62.
An unusually high mobility of atoms under intensive impulse reactions is explained by the behavior of point defects at the shock wave front. It is shown that either a shock wave front or moving dislocations can capture the interstitials, or they can be thermally activated in the direction of the shock wave propagation.  相似文献   
63.
64.
The buffer extracts (3S) of sclerotia of Sclerotinia sclerotiorum IFO 9395 contained mitogenic substance(s) to murine splenocytes (Shinohara et al. Chem. Pharm. Bull., 38, 2219 (1990)). Although the native 3S was slightly mitogenic, heating of 3S induced significant mitogenic activity. To isolate the mitogen, we separated 3S by ion-exchange and gel filtration chromatographies. The isolated mitogen, named sclerogen, has a molecular mass of 32 kilodaltons (kDa) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the isoelectric point (pI) of 5.9 by chromatofocusing. Sclerogen was significantly mitogenic in vitro against murine splenocytes after heat denaturation, and also showed the augmentation of the primary mixed lymphocyte reaction (MLR) in vitro. However, sclerogen did not show the activation of an alternative pathway of complement and hemagglutination activity. These results suggest that sclerogen is a unique mitogen which differs from lectins and shows mitogenicity after heat denaturation.  相似文献   
65.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 478–484, September, 1991.  相似文献   
66.
Large fault-tolerant interconnection networks   总被引:5,自引:0,他引:5  
This paper deals with reliability and fault-tolerant properties of networks. We first survey general reliability properties of networks, in particular those concerning diameter vulnerability. Then we study in details reliability properties of some families of networks in particular de Bruijn and Kautz networks and their generalizations which appear as very good fault-tolerant networks.  相似文献   
67.
68.
69.
70.
Photoisomerization of provitamin D 3 (7-dehydrocholesterol) in a nematic liquid crystal (ZLI-1695, Merck) is investigated in detail by UV absorption spectroscopy. It is found that dissolution of chiral molecules of provitamin D 3 induces the cholesteric phase in a nematic. The spectral kinetics of photoisomerization in this phase changes significantly from that in an ethanol solution. A sharp nonmonotonic dependence of the increase in accumulation of trans isomer tachysterol in a liquid crystal matrix with a decrease in the induced cholesteric pitch from 2200 to 25 μm is revealed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号