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   382302篇
  免费   3967篇
  国内免费   1288篇
化学   192987篇
晶体学   6087篇
力学   18857篇
综合类   16篇
数学   61217篇
物理学   108393篇
  2019年   2476篇
  2018年   12833篇
  2017年   12692篇
  2016年   10463篇
  2015年   3867篇
  2014年   4974篇
  2013年   13575篇
  2012年   12943篇
  2011年   21662篇
  2010年   13361篇
  2009年   13528篇
  2008年   16671篇
  2007年   18688篇
  2006年   10213篇
  2005年   10560篇
  2004年   9819篇
  2003年   9576篇
  2002年   8359篇
  2001年   9163篇
  2000年   7055篇
  1999年   5506篇
  1998年   4492篇
  1997年   4381篇
  1996年   4345篇
  1995年   4062篇
  1994年   3699篇
  1993年   3567篇
  1992年   4368篇
  1991年   4259篇
  1990年   4114篇
  1989年   4163篇
  1988年   4173篇
  1987年   4208篇
  1986年   4003篇
  1985年   5219篇
  1984年   5276篇
  1983年   4255篇
  1982年   4629篇
  1981年   4536篇
  1980年   4365篇
  1979年   4690篇
  1978年   4787篇
  1977年   4793篇
  1976年   4666篇
  1975年   4361篇
  1974年   4173篇
  1973年   4365篇
  1972年   2876篇
  1968年   2661篇
  1967年   2614篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
91.
Optics and Spectroscopy - 10.1134/S0030400X17050095  相似文献   
92.
Copper oxide decorated multi‐walled carbon nanotube (MWCNT) modified glassy carbon electrode (GCE) was prepared for determination of isoniazid (INZ) in various matrices. The electrochemical behavior of INZ was tested with the aid of Cyclic Voltammetry (CV) and quantitative experiments were performed by using Linear Sweep Voltammetry (LSV). Morphological and structural characterization of the modified electrode was performed by utilizing Scanning Electron Microscopy (SEM), X‐Ray Photoelectron Spectroscopy (XPS) while electrochemical characterization was performed by using CV and Electrochemical Impedance spectroscopy (EIS). The proposed sensor exhibited well defined anodic peak at 0.30 V for INZ at pH 6.0 medium. Under the optimum conditions, a linear relation between INZ concentration and peak current was observed in the range of 2.0×10?7 to 5.0×10?5 M. Limit of detection was calculated as 1.0×10?8 M and repeatability and accuracy was found as 5.60 % and 91.0 % for 5.0 10?7 M INZ by using 3 successive measurement, respectively. Then, the analytic performance of the electrode developed was tested by analyzing commercial tablets, artificial human serum and urine samples. The results indicated that satisfactory recoveries was observed for all issue.  相似文献   
93.
94.
95.
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   
96.
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting.  相似文献   
97.
98.
99.
100.
Krabbe disease is a devastating neurodegenerative disorder characterized by rapid demyelination of nerve fibers. This disease is caused by defects in the lysosomal enzyme β-galactocerebrosidase (GALC), which hydrolyzes the terminal galactose from glycosphingolipids. These lipids are essential components of eukaryotic cell membranes: substrates of GALC include galactocerebroside, the primary lipid component of myelin, and psychosine, a cytotoxic metabolite. Mutations of GALC that cause misfolding of the protein may be responsive to pharmacological chaperone therapy (PCT), whereby small molecules are used to stabilize these mutant proteins, thus correcting trafficking defects and increasing residual catabolic activity in cells. Here we describe a new approach for the synthesis of galacto-configured azasugars and the characterization of their interaction with GALC using biophysical, biochemical and crystallographic methods. We identify that the global stabilization of GALC conferred by azasugar derivatives, measured by fluorescence-based thermal shift assays, is directly related to their binding affinity, measured by enzyme inhibition. X-ray crystal structures of these molecules bound in the GALC active site reveal which residues participate in stabilizing interactions, show how potency is achieved and illustrate the penalties of aza/iminosugar ring distortion. The structure–activity relationships described here identify the key physical properties required of pharmacological chaperones for Krabbe disease and highlight the potential of azasugars as stabilizing agents for future enzyme replacement therapies. This work lays the foundation for new drug-based treatments of Krabbe disease.  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