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   77347篇
  免费   562篇
  国内免费   111篇
化学   41141篇
晶体学   1114篇
力学   3276篇
综合类   1篇
数学   7827篇
物理学   24661篇
  2021年   871篇
  2020年   969篇
  2019年   1111篇
  2018年   1596篇
  2017年   1687篇
  2016年   2149篇
  2015年   1026篇
  2014年   1719篇
  2013年   3270篇
  2012年   2902篇
  2011年   3277篇
  2010年   2640篇
  2009年   2639篇
  2008年   3004篇
  2007年   2876篇
  2006年   2771篇
  2005年   2439篇
  2004年   2240篇
  2003年   2074篇
  2002年   2137篇
  2001年   2239篇
  2000年   1627篇
  1999年   1254篇
  1998年   1126篇
  1997年   1036篇
  1996年   891篇
  1995年   831篇
  1994年   811篇
  1993年   811篇
  1992年   864篇
  1991年   933篇
  1990年   877篇
  1989年   905篇
  1988年   794篇
  1987年   763篇
  1986年   721篇
  1985年   851篇
  1984年   945篇
  1983年   799篇
  1982年   822篇
  1981年   736篇
  1980年   686篇
  1979年   753篇
  1978年   876篇
  1977年   903篇
  1976年   797篇
  1975年   761篇
  1974年   778篇
  1973年   750篇
  1972年   550篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
31.
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.  相似文献   
32.
The density functional theory calculation of 1H and 13C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated 1H and 13C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases.  相似文献   
33.
Sukhorukova  O. S.  Tarasenko  A. S.  Tarasenko  S. V.  Shavrov  V. G. 《JETP Letters》2020,112(7):420-427
JETP Letters - At the resonant passage of a plane elastic shear wave through an acoustically continuous heterostructure consisting of magnetic and nonmagnetic layers in a symmetric nonmagnetic...  相似文献   
34.
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method.  相似文献   
35.
Russian Chemical Bulletin - Terminal disaccharide fragment of phenolic glycolipid from Mycobacterium leprae (PGL-I) was synthesized as a glycoside with 4-(2-aminoethoxy)phenyl aglycon. The obtained...  相似文献   
36.
37.
38.
Colloid Journal - It has been found that the addition of ammonia water to a gold sol obtained by the Duff method induces the growth of the gold particles. The growth kinetics of such particles in...  相似文献   
39.
40.
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics.  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