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   153364篇
  免费   1851篇
  国内免费   584篇
化学   84215篇
晶体学   2459篇
力学   6346篇
综合类   28篇
数学   14579篇
物理学   48172篇
  2021年   1204篇
  2020年   1359篇
  2019年   1428篇
  2018年   1802篇
  2017年   1829篇
  2016年   2752篇
  2015年   1772篇
  2014年   2586篇
  2013年   6497篇
  2012年   5255篇
  2011年   6395篇
  2010年   4473篇
  2009年   4466篇
  2008年   6048篇
  2007年   5783篇
  2006年   5659篇
  2005年   5191篇
  2004年   4625篇
  2003年   4306篇
  2002年   4163篇
  2001年   5680篇
  2000年   4094篇
  1999年   3169篇
  1998年   2167篇
  1997年   2268篇
  1996年   2138篇
  1995年   1964篇
  1994年   1995篇
  1993年   1784篇
  1992年   2286篇
  1991年   2349篇
  1990年   2189篇
  1989年   2137篇
  1988年   2118篇
  1987年   2121篇
  1986年   1947篇
  1985年   2431篇
  1984年   2450篇
  1983年   1947篇
  1982年   1972篇
  1981年   1800篇
  1980年   1794篇
  1979年   2075篇
  1978年   2154篇
  1977年   2097篇
  1976年   2021篇
  1975年   1895篇
  1974年   1875篇
  1973年   1910篇
  1972年   1244篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
The aggregate error locator is defined and a computation method is given. The aggregate error locator is then used in a type of Forney algorithm to compute the error values in the received words of a Ca,b algebraic geometry code.  相似文献   
72.
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   
73.
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   
74.
75.
 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   
76.
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   
77.
78.
We study matter-wave solitons in Bose-Einstein condensates of ultracold gaseous atoms with spin degrees of freedom and present a class of exact solutions based on the inverse scattering method. The one-soliton solutions are classified with respect to the spin states. We analyze collisional effects between solitons in the same or different spin state(s), which reveals a very interesting possibility: we can manipulate the spin dynamics by controlling the parameters of colliding solitons.  相似文献   
79.
80.
The occurrence and formation of black spots areas in PolyLED devices has been studied by time-of-flight SIMS (TOFSIMS). The composition, shape and position of the black spots is visualised by three-dimensional (3D)-TOFSIMS depth-profiling. It has been established that the formation of non-emissive spots is due to the growth of aluminium oxide clusters at the AlBa/polymer interface. Electron injection in the black spots is lost by the resulting local increase of the resistivity of the cathode.  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