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   423755篇
  免费   5406篇
  国内免费   2133篇
化学   231501篇
晶体学   6343篇
力学   17588篇
综合类   63篇
数学   49283篇
物理学   126516篇
  2020年   3282篇
  2019年   3654篇
  2018年   4529篇
  2017年   4554篇
  2016年   6912篇
  2015年   4662篇
  2014年   6863篇
  2013年   18598篇
  2012年   14438篇
  2011年   17731篇
  2010年   12138篇
  2009年   11881篇
  2008年   16190篇
  2007年   16484篇
  2006年   15268篇
  2005年   14094篇
  2004年   12592篇
  2003年   11174篇
  2002年   11033篇
  2001年   12367篇
  2000年   9303篇
  1999年   7170篇
  1998年   6005篇
  1997年   5978篇
  1996年   5775篇
  1995年   5268篇
  1994年   5190篇
  1993年   5121篇
  1992年   5571篇
  1991年   5661篇
  1990年   5317篇
  1989年   5254篇
  1988年   5240篇
  1987年   5111篇
  1986年   4974篇
  1985年   6720篇
  1984年   6917篇
  1983年   5716篇
  1982年   6259篇
  1981年   5905篇
  1980年   5666篇
  1979年   5836篇
  1978年   6201篇
  1977年   6115篇
  1976年   6305篇
  1975年   5711篇
  1974年   5888篇
  1973年   6201篇
  1972年   4305篇
  1971年   3404篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
131.
132.
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557  相似文献   
133.
Russian Journal of Organic Chemistry - The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)­azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave...  相似文献   
134.
135.
136.
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics.  相似文献   
137.
Journal of Thermal Analysis and Calorimetry - The operating temperature of Li-ion batteries used in modern electric vehicles should be maintained within an allowable range to avoid thermal runaway...  相似文献   
138.
ABSTRACT

A new density functional for the study of associating inhomogeneous fluids based on Wertheim's first-order thermodynamic perturbation theory is presented and compared to the most currently used associating density functionals. This functional is developed using the weighted density approximation in the range of association of hard spheres. We implement this functional within the framework of classical density functional theory together with modified fundamental measure theory to account for volume exclusion of hard spheres. This approach is tested against molecular simulations from literature of pure associating hard spheres and mixtures of non-associationg and associating hard spheres with different number of bonding sites close to a hard uniform wall. Furthermore, we compare and review our results with the performance of associating functionals from literature, one based on fundamental measure theory and the inhomogeneous version of Wertheim's perturbation theory. Results obtained with classical DFT and the three functionals show excellent agreement with molecular simulations in systems with one hard wall. For the cases of small pores where only one or two layers of fluid are allowed discrepancies between results with classical DFT and molecular simulations were found.  相似文献   
139.
140.
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