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   16844篇
  免费   623篇
  国内免费   125篇
化学   11357篇
晶体学   76篇
力学   499篇
数学   2963篇
物理学   2697篇
  2023年   108篇
  2022年   278篇
  2021年   471篇
  2020年   352篇
  2019年   388篇
  2018年   342篇
  2017年   294篇
  2016年   649篇
  2015年   536篇
  2014年   586篇
  2013年   1015篇
  2012年   1127篇
  2011年   1331篇
  2010年   799篇
  2009年   731篇
  2008年   1123篇
  2007年   1036篇
  2006年   1009篇
  2005年   859篇
  2004年   711篇
  2003年   572篇
  2002年   549篇
  2001年   208篇
  2000年   179篇
  1999年   147篇
  1998年   170篇
  1997年   159篇
  1996年   181篇
  1995年   111篇
  1994年   136篇
  1993年   113篇
  1992年   112篇
  1991年   94篇
  1990年   78篇
  1989年   73篇
  1988年   59篇
  1987年   63篇
  1986年   51篇
  1985年   75篇
  1984年   101篇
  1983年   62篇
  1982年   72篇
  1981年   59篇
  1980年   63篇
  1979年   47篇
  1978年   51篇
  1977年   50篇
  1976年   29篇
  1974年   23篇
  1973年   24篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
Journal of Dynamics and Differential Equations - In this paper we focus on a class of symmetric vector fields in the context of singularly perturbed fast-slow dynamical systems. Our main question...  相似文献   
2.
Annals of Global Analysis and Geometry - In this paper, we characterize round spheres in the Euclidean space under some suitable conditions on the r-mean curvature.  相似文献   
3.
The aim of this work was to determine the parameters that have decisive roles in microwave-assisted reactions and to develop a model, using computational chemistry, to predict a priori the type of reactions that can be improved under microwaves. For this purpose, a computational study was carried out on a variety of reactions, which have been reported to be improved under microwave irradiation. This comprises six types of reactions. The outcomes obtained in this study indicate that the most influential parameters are activation energy, enthalpy, and the polarity of all the species that participate. In addition to this, in most cases, slower reacting systems observe a much greater improvement under microwave irradiation. Furthermore, for these reactions, the presence of a polar component in the reaction (solvent, reagent, susceptor, etc.) is necessary for strong coupling with the electromagnetic radiation. We also quantified that an activation energy of 20–30 kcal mol−1 and a polarity (μ) between 7–20 D of the species involved in the process is required to obtain significant improvements under microwave irradiation.  相似文献   
4.
A generic strategy based on the use of CdSe/ZnS Quantum Dots (QDs) as elemental labels for protein quantification, using immunoassays with elemental mass spectrometry (ICP-MS), detection is presented. In this strategy, streptavidin modified QDs (QDs-SA) are bioconjugated to a biotinylated secondary antibody (b-Ab2). After a multi-technique characterization of the synthesized generic platform (QDs-SA-b-Ab2) it was applied to the sequential quantification of five proteins (transferrin, complement C3, apolipoprotein A1, transthyretin and apolipoprotein A4) at different concentration levels in human serum samples. It is shown how this generic strategy does only require the appropriate unlabeled primary antibody for each protein to be detected. Therefore, it introduces a way out to the need for the cumbersome and specific bioconjugation of the QDs to the corresponding specific recognition antibody for every target analyte (protein). Results obtained were validated with those obtained using UV–vis spectrophotometry and commercial ELISA Kits.  相似文献   
5.
Journal of Thermal Analysis and Calorimetry - The aim of this work is to synthesize and characterize a new structured silver–clay dried, calcined or sintered at different temperatures...  相似文献   
6.
7.
8.
Meccanica - Fiber reinforced materials are used in assorted engineering application and for this reason, new additive manufacturing technologies have been developed for this type of materials. With...  相似文献   
9.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
10.
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