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   154972篇
  免费   1657篇
  国内免费   410篇
化学   83531篇
晶体学   2037篇
力学   6704篇
综合类   7篇
数学   15696篇
物理学   49064篇
  2020年   1147篇
  2019年   1200篇
  2018年   1505篇
  2017年   1491篇
  2016年   2530篇
  2015年   1606篇
  2014年   2489篇
  2013年   6441篇
  2012年   5119篇
  2011年   6439篇
  2010年   4405篇
  2009年   4402篇
  2008年   5856篇
  2007年   5947篇
  2006年   5582篇
  2005年   5197篇
  2004年   4552篇
  2003年   3975篇
  2002年   4000篇
  2001年   4352篇
  2000年   3343篇
  1999年   2590篇
  1998年   2259篇
  1997年   2202篇
  1996年   2017篇
  1995年   1917篇
  1994年   1903篇
  1993年   1745篇
  1992年   2005篇
  1991年   2123篇
  1990年   1925篇
  1989年   1928篇
  1988年   1862篇
  1987年   1760篇
  1986年   1699篇
  1985年   2205篇
  1984年   2338篇
  1983年   1908篇
  1982年   2088篇
  1981年   1975篇
  1980年   1894篇
  1979年   2037篇
  1978年   2201篇
  1977年   2073篇
  1976年   2119篇
  1975年   2023篇
  1974年   2074篇
  1973年   2066篇
  1972年   1360篇
  1971年   1211篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed.  相似文献   
43.
44.
Krabbe disease is a devastating neurodegenerative disorder characterized by rapid demyelination of nerve fibers. This disease is caused by defects in the lysosomal enzyme β-galactocerebrosidase (GALC), which hydrolyzes the terminal galactose from glycosphingolipids. These lipids are essential components of eukaryotic cell membranes: substrates of GALC include galactocerebroside, the primary lipid component of myelin, and psychosine, a cytotoxic metabolite. Mutations of GALC that cause misfolding of the protein may be responsive to pharmacological chaperone therapy (PCT), whereby small molecules are used to stabilize these mutant proteins, thus correcting trafficking defects and increasing residual catabolic activity in cells. Here we describe a new approach for the synthesis of galacto-configured azasugars and the characterization of their interaction with GALC using biophysical, biochemical and crystallographic methods. We identify that the global stabilization of GALC conferred by azasugar derivatives, measured by fluorescence-based thermal shift assays, is directly related to their binding affinity, measured by enzyme inhibition. X-ray crystal structures of these molecules bound in the GALC active site reveal which residues participate in stabilizing interactions, show how potency is achieved and illustrate the penalties of aza/iminosugar ring distortion. The structure–activity relationships described here identify the key physical properties required of pharmacological chaperones for Krabbe disease and highlight the potential of azasugars as stabilizing agents for future enzyme replacement therapies. This work lays the foundation for new drug-based treatments of Krabbe disease.  相似文献   
45.
Kim  F. H.  Moylan  S. P.  Phan  T. Q.  Garboczi  E. J. 《Experimental Mechanics》2020,60(7):987-1004
Experimental Mechanics - Insufficient data are available to fully understand the effects of metal additive manufacturing (AM) defects for widespread adoption of the emerging technology....  相似文献   
46.
47.
Nonlinear Dynamics - Introduction of stiffness nonlinearities to broaden the frequency bandwidth of vibratory energy harvesters has the adverse influence of complicating the response behavior of...  相似文献   
48.
We report on the first examples of isolated silanol–silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol–silanolate anions are postulated intermediates in the hydroxide‐mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization.  相似文献   
49.
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs).  相似文献   
50.
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