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   263878篇
  免费   3261篇
  国内免费   1002篇
化学   144361篇
晶体学   3694篇
力学   10448篇
综合类   3篇
数学   31026篇
物理学   78609篇
  2020年   1942篇
  2019年   2272篇
  2018年   2676篇
  2017年   2581篇
  2016年   4202篇
  2015年   2886篇
  2014年   4281篇
  2013年   12271篇
  2012年   9063篇
  2011年   11250篇
  2010年   7219篇
  2009年   6989篇
  2008年   10129篇
  2007年   10312篇
  2006年   9558篇
  2005年   8977篇
  2004年   8026篇
  2003年   7084篇
  2002年   6987篇
  2001年   7515篇
  2000年   5607篇
  1999年   4429篇
  1998年   3788篇
  1997年   3832篇
  1996年   3623篇
  1995年   3391篇
  1994年   3188篇
  1993年   3246篇
  1992年   3530篇
  1991年   3534篇
  1990年   3337篇
  1989年   3307篇
  1988年   3395篇
  1987年   3247篇
  1986年   3144篇
  1985年   4316篇
  1984年   4518篇
  1983年   3682篇
  1982年   4115篇
  1981年   3973篇
  1980年   3814篇
  1979年   3835篇
  1978年   4033篇
  1977年   3854篇
  1976年   4022篇
  1975年   3596篇
  1974年   3709篇
  1973年   3993篇
  1972年   2427篇
  1971年   1861篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
21.
Chen  R. J.  Chen  W.  Kong  F. L. 《Analysis Mathematica》2022,48(1):19-28

Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.

  相似文献   
22.
Physics of Particles and Nuclei Letters - When creating accelerators and storage-ring installations in a compact space, there is not always enough space for all the necessary magnet elements. In...  相似文献   
23.
24.
The growth-fragmentation equation describes a system of growing and dividing particles, and arises in models of cell division, protein polymerisation and even telecommunications protocols. Several important questions about the equation concern the asymptotic behaviour of solutions at large times: at what rate do they converge to zero or infinity, and what does the asymptotic profile of the solutions look like? Does the rescaled solution converge to its asymptotic profile at an exponential speed? These questions have traditionally been studied using analytic techniques such as entropy methods or splitting of operators. In this work, we present a probabilistic approach: we use a Feynman–Kac formula to relate the solution of the growth-fragmentation equation to the semigroup of a Markov process, and characterise the rate of decay or growth in terms of this process. We then identify the Malthus exponent and the asymptotic profile in terms of a related Markov process, and give a spectral interpretation in terms of the growth-fragmentation operator and its dual.  相似文献   
25.
26.
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
27.
28.
29.
30.
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   
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