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   147270篇
  免费   1471篇
  国内免费   394篇
化学   80375篇
晶体学   2399篇
力学   6066篇
综合类   3篇
数学   13618篇
物理学   46674篇
  2021年   1030篇
  2020年   1185篇
  2019年   1252篇
  2018年   1640篇
  2017年   1695篇
  2016年   2551篇
  2015年   1564篇
  2014年   2355篇
  2013年   6047篇
  2012年   4864篇
  2011年   5943篇
  2010年   4195篇
  2009年   4228篇
  2008年   5744篇
  2007年   5514篇
  2006年   5391篇
  2005年   4955篇
  2004年   4457篇
  2003年   4121篇
  2002年   4018篇
  2001年   5549篇
  2000年   3982篇
  1999年   3081篇
  1998年   2112篇
  1997年   2212篇
  1996年   2081篇
  1995年   1917篇
  1994年   1922篇
  1993年   1732篇
  1992年   2221篇
  1991年   2305篇
  1990年   2143篇
  1989年   2110篇
  1988年   2083篇
  1987年   2089篇
  1986年   1914篇
  1985年   2377篇
  1984年   2396篇
  1983年   1914篇
  1982年   1922篇
  1981年   1756篇
  1980年   1746篇
  1979年   2033篇
  1978年   2110篇
  1977年   2051篇
  1976年   1978篇
  1975年   1865篇
  1974年   1849篇
  1973年   1880篇
  1972年   1239篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Analytical formulas are derived that describe the dependences of the transition probabilities in vibrational-rotational spectra of XY3-type molecules with C 3v symmetry on the rotational quantum numbers.  相似文献   
102.
103.
104.
105.
A three-dimensional molecular dynamics (MD) model is utilized to investigate the effect of tool geometry on the deformation process of the workpiece and the nature of deformation process at the atomic-scale. Results show that different states exist between the atomic force microscope (AFM) pin tool and the workpiece surface, i.e. the non-wear state, the ploughing state, the state in which ploughing is dominant and the state in which cutting plays a key role. A relationship between the deformation process of the workpiece and the potential energy variation is presented. The potential energy variation of atoms in different deformed regions in the workpiece such as plastically deformed region, elastically deformed region and the mixed deformation region is different. The features of variations of potential energy are discussed.  相似文献   
106.
A systematic study on the electrochemical behavior of diosmin in Britton-Robinson buffer (pH 2.0-10.0) at a glassy carbon electrode (GCE) was made. The oxidation process of the drug was found to be quasi-reversible with an adsorption-controlled step. The adsorption stripping response was evaluated with respect to various experimental conditions, such as the pH of the supporting electrolyte, the accumulation potential and the accumulation time. The observed anodic peak current at +0.73 V vs. Ag/AgCl reference electrode increased linearly over two orders of magnitude from 5.0x10(-8) M to 9.0x10(-6) M. A limit of detection down to 3.5x10(-8) M of diosmin at the GCE was achieved with a mean recovery of 97+/-2.1%. Based on the electrochemical data, an open-circuit accumulation step in a stirred sample solution of BR at pH 3.0 was developed. The proposed method was successfully applied to the determination of the drug in pharmaceutical formulations. The results compared favorably with the data obtained via spectrophotometric and HPLC methods.  相似文献   
107.
108.
GAMMA 10 experiments have advanced in high density experiments after the last EPS Workshop where we reported high density plasma production by using an ion cyclotron range of frequency heating at a high harmonic frequency and neutral beam injection in the central cell. Recently a high density plasma was obtained with much improved reproducibility than before and without degradation of diamagnetic signal. The high density plasma was attained by adjusting the spacing of the conducting plates installed in the anchor transition regions. Dependencies of particle confinement time, ion energy confinement time and plasma confining potential on plasma density were obtained for the first time in the high density region. Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreus, Switzerland, June 23–24, 2002.  相似文献   
109.
 The development of a tool for calculating resonances and bound states in three-body systems described by a single-potential energy surface is reported. The method has been applied to the antiprotonic helium, doubly excited states in helium, the 11Li nuclear halo, the NeICl van der Waals molecule, and the recently found FHD reaction complex. Received November 26, 2001; accepted for publication November 28, 2001  相似文献   
110.
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   
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