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   1673篇
  免费   300篇
  国内免费   157篇
化学   1310篇
晶体学   20篇
力学   88篇
综合类   5篇
数学   132篇
物理学   575篇
  2024年   2篇
  2023年   36篇
  2022年   25篇
  2021年   64篇
  2020年   68篇
  2019年   67篇
  2018年   67篇
  2017年   40篇
  2016年   83篇
  2015年   79篇
  2014年   84篇
  2013年   109篇
  2012年   161篇
  2011年   164篇
  2010年   104篇
  2009年   86篇
  2008年   118篇
  2007年   101篇
  2006年   99篇
  2005年   100篇
  2004年   59篇
  2003年   40篇
  2002年   44篇
  2001年   31篇
  2000年   26篇
  1999年   31篇
  1998年   26篇
  1997年   28篇
  1996年   23篇
  1995年   23篇
  1994年   22篇
  1993年   13篇
  1992年   17篇
  1991年   21篇
  1990年   18篇
  1989年   3篇
  1988年   7篇
  1987年   10篇
  1986年   5篇
  1985年   5篇
  1983年   6篇
  1982年   2篇
  1981年   1篇
  1980年   4篇
  1979年   1篇
  1978年   1篇
  1976年   2篇
  1974年   1篇
  1947年   1篇
  1946年   1篇
排序方式: 共有2130条查询结果,搜索用时 125 毫秒
91.
A series of strongly phosphorescent copper(I) halide complexes, namely [Cu(μ-X)POP]2 (X = Cl (1), Br (2), I (3), Br0.5Cl0.5 (4), POP = bis[2-(diphenylphosphino)phenyl]ether), have been synthesized by reacting CuX with the diphosphine ligand in 1:1 molar ratio. All complexes were characterized by spectroscopic analysis (IR, UV–Vis), elemental analysis, and photoluminescence study. Single-crystal X-ray diffraction revealed that complex 2 is a dinuclear structure which is constructed by two μ-X bridges and two POP ligands as μ2 bridges. Other complexes were determined as isologues of complex 2 by powder X-ray diffraction and elemental analysis. All complexes exhibit intense blue-green phosphorescence with a lifetime of ~1 μs in the solid state. The halogen-mixed complex presents a lightly change in the luminescence comparing to that of parent complexes. The excited states of all complexes have been assigned as halide-to-ligand charge transfer state mixed metal-to-ligand charge transfer character based on the time-dependent density functional theory calculations. All complexes are thermally stable according to thermogravimetric analysis so that they are suitable for applying in luminescent devices.  相似文献   
92.
The weighted essentially nonoscillatory scheme is improved by introducing new smoothness indicators that evaluate the interactions among the classical smoothness indicators suggested by Jiang and Shu. The effect of the key parameters in the new smoothness indicators on the scheme is systematically investigated. The improved scheme has smaller dissipation with larger weight assignment to the discontinuous stencils and higher numerical accuracy with weights closer to the ideal weights. To verify the theory, benchmark problems governed by the linear transport equation, the 1‐dimensional nonlinear Burgers equation, and the Euler equations are conducted and analyzed, respectively. Better computational performances both on numerical resolution and accuracy are shown in the comparisons with other classical weighted essentially nonoscillatory schemes.  相似文献   
93.
Intact chloroplasts were isolated from mesophyll protoplasts of Brassia napus. Concentrations of 8 rare earth elements (REEs) in the chloroplasts were determined by instrumental neutron activation analysis (INAA). The results showed that there were trace amounts of REEs in the chloroplasts, which corresponded to 1 atom of REEs per 2000 chlorophyll molecules. About 30% of the total REEs in the leaves are localized in the chloroplasts and the light REEs were enriched with respect to the heavy elements of the series.  相似文献   
94.
In this paper,a semlparametrie resresaion model in which errors are i. i. d random variables from an unknown density f( ) is considered. Based on Hall et al. (1995),a nonlinear wavelet estimation of f( ) without restrictions of continuity everywhere on f( ) is given,and the convergence rate of the estimators in L2 is obtained.  相似文献   
95.
A Si-substituted rhodamine based water-soluble fluorescent probe bearing a tetrathia-azacrown was designed for fluorescence imaging of Cu+ with substantial affinity and selectivity.In physiological condition,the developed probe with outstanding water-solubility exhibits ultrahigh sensitivity to Cu+,ensuring the reliable fluorescence imaging in vivo.  相似文献   
96.
Preface     
Owing to the fast economic growing and the concern over greenhouse gases and air pollution,the development of nuclear energy is one important option to meet the expanded energy consumption in our future.To achieve that goal,continuing and reliable supplies of uranium are critical to future nuclear power projects.As is well known,global terrestrial reserves of uranium are limited and the deposits in China are relatively small.Given the projected big growth in nuclear power in the future,reliable supply of uranium at a reasonable price is essential for China.  相似文献   
97.
TMSCl was shown to be an efficient reagent for selective deprotection of the anomeric position protected as N,O-dimethylhydroxylamine glycoside. This deprotection condition was proved to be compatible with a number of protecting groups, such as the TBDPS, acetyl, benzyl, benzylidene, and benzoyl groups.  相似文献   
98.
99.
Disulfides have been synthesized by oxidation of thiols using air as oxidant catalyzed by Co-Salophen with high yields,mild and neutral conditions,and easy procedures of the catalyst.The products were confirmed by ~1H NMR and IR.  相似文献   
100.
This study presents an efficient strategy based on microwave‐assisted extraction (MAE), HPLC‐DAD‐MS/MS and high‐speed counter‐current chromatography (HSCCC) for the rapid extraction, identification, separation and purification of active components from the traditional Chinese medicine Fructus Aurantii Immaturus. An LC‐DAD‐MS/MS method was applied for the screening and structural identification of main components in crude extract, and five components were preliminarily identified as neoeriocitrin, narirutin, naringin, hesperidin and neohesperidin according to their UV and mass spectra. An efficient MAE method for the extraction of the three most abundant components (narirutin, naringin and neohesperidin) was optimized by the combination of univariate and multivariate approaches. The crude extract was then separated and purified by HSCCC and a total of 61.6 mg of narirutin, 207.3 mg of naringin and 159.5 mg of neohesperidin at high purities of 98.1, 97.2 and 99.5%, respectively, were obtained from 1.42 g of crude extract. The recoveries of these compounds were 86, 93 and 89%, respectively. Copyright © 2009 John Wiley & Sons, Ltd.  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