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   355821篇
  免费   7033篇
  国内免费   4912篇
化学   172379篇
晶体学   5303篇
力学   20739篇
综合类   325篇
数学   50805篇
物理学   118215篇
  2021年   4514篇
  2020年   5120篇
  2019年   5892篇
  2018年   7864篇
  2017年   7909篇
  2016年   10004篇
  2015年   5309篇
  2014年   9210篇
  2013年   15399篇
  2012年   13719篇
  2011年   15496篇
  2010年   12758篇
  2009年   12867篇
  2008年   14344篇
  2007年   13871篇
  2006年   12519篇
  2005年   10808篇
  2004年   10260篇
  2003年   9410篇
  2002年   9736篇
  2001年   9214篇
  2000年   7291篇
  1999年   5599篇
  1998年   5281篇
  1997年   4961篇
  1996年   4568篇
  1995年   4004篇
  1994年   4099篇
  1993年   4081篇
  1992年   4001篇
  1991年   4403篇
  1990年   4386篇
  1989年   4314篇
  1988年   4031篇
  1987年   4082篇
  1986年   3747篇
  1985年   4309篇
  1984年   4515篇
  1983年   3892篇
  1982年   4058篇
  1981年   3699篇
  1980年   3456篇
  1979年   3997篇
  1978年   4075篇
  1977年   4203篇
  1976年   4362篇
  1975年   4059篇
  1974年   3963篇
  1973年   4085篇
  1972年   3544篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
81.
Theoretical and Computational Fluid Dynamics - The present study aims to simulate a collision of two droplets containing immiscible liquids by employing a three- dimensional incompressible smoothed...  相似文献   
82.
Seven new copper(II) complexes of type [Cu(A)(L)]?H2O (A = sparfloxacin, ciprofloxacin, levofloxacin, gatifloxacin, pefloxacin, ofloxacin, norfloxacin; L = 5‐[(3‐chlorophenyl)diazenyl]‐4‐hydroxy‐1,3‐thiazole‐2(3H)‐thione) were synthesized and characterized using elemental and thermogravimetric analyses, and electronic, electron paramagnetic resonance (EPR), Fourier transform infrared and liquid chromatography–mass spectroscopies. Tetrahedral geometry around copper is assigned in all complexes using EPR and electronic spectral analyses. All complexes were investigated for their interaction with herring sperm DNA utilizing absorption titration (Kb = 1.27–3.13 × 105 M?1) and hydrodynamic volume measurement studies. The studies suggest the classical intercalative mode of DNA binding. The cleavage reaction on pUC19 DNA was monitored by agarose gel electrophoresis. The results indicate that the Cu(II) complexes can more effectively promote the cleavage of plasmid DNA. The superoxide dismutase mimic activity of the complexes was evaluated by nitroblue tetrazolium assay, and the complexes catalysed the dismutation of superoxide at pH = 7.8 with IC50 values in the range 0.597–0.900 μM. The complexes were screened for their in vitro antibacterial activity against five pathogenic bacteria. All the complexes are good cytotoxic agents and show LC50 values ranging from 5.559 to 11.912 µg ml?1. All newly synthesized Cu(II) complexes were also evaluated for their in vitro antimalarial activity against Plasmodium falciparum strain (IC50 = 0.62–2.0 µg ml?1). Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
83.
84.
85.
This study was aimed at the development of a conductometric biosensor based on acetylcholinesterase considering the feasibility of its application for the inhibitory analysis of various toxicants. In this paper, the optimum conditions for enzyme immobilization on the transducer surface are selected as well as the optimum concentration of substrate for inhibitory analysis. Sensitivity of the developed biosensor to different classes of toxic compounds (organophosphorus pesticides, heavy metal ions, surfactants, aflatoxin, glycoalkaloids) was tested. It is shown that the developed biosensor can be successfully used for the analysis of pesticides and mycotoxins, as well as for determination of total toxicity of the samples. A new method of biosensor analysis of toxic substances of different classes in complex multicomponent aqueous samples is proposed.  相似文献   
86.
87.
88.
Russian Journal of General Chemistry - The main sources of emissions of industrial nitrogen oxides have been reviewed. A promising method for the absorption of nitrogen monoxide by a reusable...  相似文献   
89.
90.
Hierarchically porous metal–organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.  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