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   16632篇
  免费   723篇
  国内免费   66篇
化学   11417篇
晶体学   47篇
力学   350篇
综合类   1篇
数学   2348篇
物理学   3258篇
  2023年   106篇
  2022年   115篇
  2021年   225篇
  2020年   341篇
  2019年   340篇
  2018年   182篇
  2017年   178篇
  2016年   487篇
  2015年   526篇
  2014年   545篇
  2013年   741篇
  2012年   1028篇
  2011年   1071篇
  2010年   668篇
  2009年   566篇
  2008年   866篇
  2007年   869篇
  2006年   808篇
  2005年   776篇
  2004年   643篇
  2003年   536篇
  2002年   505篇
  2001年   297篇
  2000年   243篇
  1999年   227篇
  1998年   223篇
  1997年   214篇
  1996年   200篇
  1995年   180篇
  1994年   183篇
  1993年   190篇
  1992年   180篇
  1991年   142篇
  1990年   117篇
  1989年   125篇
  1988年   121篇
  1987年   106篇
  1986年   103篇
  1985年   123篇
  1984年   108篇
  1983年   98篇
  1982年   119篇
  1981年   116篇
  1980年   95篇
  1979年   98篇
  1978年   98篇
  1977年   94篇
  1976年   92篇
  1975年   89篇
  1973年   94篇
排序方式: 共有10000条查询结果,搜索用时 921 毫秒
991.
A mathematical study via variational convergence of a periodic distribution of classical linearly elastic thin plates softly abutted together shows that it is not necessary to use a different continuum model nor to make constitutive symmetry hypothesis as starting points to deduce the Reissner–Mindlin plate model.  相似文献   
992.
A facile click chemistry method of immobilizing surface‐functionalized polymer vesicles on casted polymeric PAN substrates is described. Microporous PAN membranes were subjected to hydrochloric acid hydrolysis to obtain surface carboxylates. The carboxylic groups were activated with EDC/NHS‐solution and were then reacted with propargylamine to introduce alkyne groups for CuAAC reactions. The alkyne functionality of the modified membrane surface was verified by reaction with an azide functional click dye both before and after the immobilization of azide‐functionalized ABA vesicles. The efficient postfunctionalization of the membrane with alkyne allowed quantitative coverage of the membrane surface with a polymersome monolayer, as confirmed by immobilization of polymerzomes loaded with a fluorescent dye. Polymersome monolayers immobilized on alkyne functionalized PAN‐membranes were characterized by cryo‐SEM and monolayers were confirmed by atom force microscopy. These methods opens up new avenues for preparing membrane based filtration and sensor technologies. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2032–2039  相似文献   
993.
994.
Models of eye movements of an observer searching for human targets are helpful in developing accurate models of target acquisition times and false positive detections. We develop a new model describing the distribution of gaze positions for an observer which includes both bottom-up (salience) and top-down (task dependent) factors. We validate the combined model against a bottom-up model from the literature and against the bottom up and top down parts alone using human performance data on stationary targets. The new model is shown to be significantly better. The new model requires a large amount of data about the terrain and the target that is obtained directly from the 3D simulation through an automated process.  相似文献   
995.
The authors propose a method for the extraction of material parameter and thickness information from sub-100-μm thin samples using non-differential transmission terahertz time domain spectroscopy. The approach relies on an additional Fourier transform of the frequency dependent material parameters to a quasi space regime. In this quasi space, periodic Fabry-Perot oscillations from the frequency domain, which originate from multiple reflections inside the sample, correspond to discrete peaks. By iterative minimization of these peaks, the highly precise thickness information along with the refractive index and absorption coefficient of the sample can be determined. Experimental verification of the approach is also provided.  相似文献   
996.
An individual’s optimal behavior in a continuous-time sequential job search model with savings and CARA preferences is characterized analytically. I isolate the effects of limited borrowing and nonnegative consumption as well as risk aversion on the reservation wage by using a system of ordinary differential equations.  相似文献   
997.
We describe elementary transformations between minimal models of rational surfaces in terms of unprojections. These do not fit into the framework of Kustin–Miller unprojections as introduced by Papadakis and Reid, since we have to leave the world of projectively Gorenstein varieties. Also, our unprojections do not depend on the choice of the unprojection locus only, but need extra data corresponding to the choice of a divisor on this unprojection locus.  相似文献   
998.
999.
We proved in an earlier work that any existence variety of regular algebras is generated by its simple unital Artinian members, while any existence variety of Arguesian sectionally complemented lattices is generated by its simple members of finite length. A characterization of the class of simple unital Artinian members [members of finite length, respectively] of such varieties is given in the present paper.  相似文献   
1000.
Childhood malnutrition is highly prevalent and associated with high mortality risk. In observational and interventional studies among malnourished children, body composition is increasingly recognised as a key outcome. The deuterium dilution technique has generated high-quality data on body composition in studies of infants and young children in several settings, but its feasibility and accuracy in children suffering from moderate acute malnutrition requires further study. Prior to a large nutritional intervention trial among children with moderate acute malnutrition, we conducted pilot work to develop and adapt the deuterium dilution technique. We refined procedures for administration of isotope doses and collection of saliva. Furthermore, we established that equilibration time in local context is 3?h. These findings and the resulting standard operating procedures are important to improve data quality when using the deuterium dilution technique in malnutrition studies in field conditions, and may encourage a wider use of isotope techniques.  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