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   98829篇
  免费   1152篇
  国内免费   390篇
化学   38201篇
晶体学   931篇
力学   7048篇
数学   35296篇
物理学   18895篇
  2023年   147篇
  2022年   127篇
  2021年   228篇
  2020年   345篇
  2019年   337篇
  2018年   10733篇
  2017年   10513篇
  2016年   6790篇
  2015年   1477篇
  2014年   979篇
  2013年   1782篇
  2012年   5125篇
  2011年   11675篇
  2010年   6374篇
  2009年   6712篇
  2008年   7695篇
  2007年   9872篇
  2006年   1340篇
  2005年   2334篇
  2004年   2467篇
  2003年   2689篇
  2002年   1644篇
  2001年   746篇
  2000年   745篇
  1999年   490篇
  1998年   421篇
  1997年   365篇
  1996年   482篇
  1995年   322篇
  1994年   312篇
  1993年   287篇
  1992年   248篇
  1991年   246篇
  1990年   233篇
  1989年   214篇
  1988年   211篇
  1987年   200篇
  1986年   198篇
  1985年   247篇
  1984年   246篇
  1983年   163篇
  1982年   174篇
  1981年   183篇
  1980年   188篇
  1979年   142篇
  1978年   132篇
  1977年   122篇
  1976年   102篇
  1975年   103篇
  1973年   98篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within...  相似文献   
2.
Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of...  相似文献   
3.
Set-Valued and Variational Analysis - In a Hilbert framework ℌ, we study the convergence properties of a Newton-like inertial dynamical system governed by a general maximally monotone...  相似文献   
4.
5.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
6.
7.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
8.
9.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
10.
A sensitive, specific and reproducible HPLC method has been developed and validated for the quantitative determination of 6‐methylcoumarin (6MC) in plasma and other tissues in Wistar rats. A C18 column was used with UV detection at 321 nm and a gradient system consisting of methanol‐deionized water was used as mobile phase. The retention time for 6MC was 14.921 min and no interfering peaks were observed for any of the matrices. Linear relationships (r2 > 0.997) were obtained between the peak height ratios and the corresponding biological sample concentrations over the range 0.4–12.8 µg/mL. Precision and accuracy were evaluated; the coefficient of variation and the relative error for all of the organs were <2 and 7%, respectively. The limit of quantitation was 0.20 µg/mL for the heart and 0.30 µg/mL for the other tissues evaluated. This HPLC method was successfully used in the determination of 6MC in the biodistribution study after administration of 200 mg/kg of both 6MC‐free and 6MC‐loaded polymeric microparticles. In this study, extensive 6MC was found, in both free and microencapsulated forms, in all the organs tested. The 6MC‐free showed a range of between 1.7 and 11.5 µg/g, while the microencapsulated 6MC showed concentrations of between 6.35 and 17.7 µg/g, suggesting that 6MC improved absorption rate. Copyright © 2014 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