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   240214篇
  免费   2755篇
  国内免费   860篇
化学   128753篇
晶体学   2967篇
力学   9868篇
综合类   2篇
数学   27051篇
物理学   75188篇
  2020年   1770篇
  2019年   2037篇
  2018年   2469篇
  2017年   2399篇
  2016年   3817篇
  2015年   2586篇
  2014年   3894篇
  2013年   11148篇
  2012年   8074篇
  2011年   10003篇
  2010年   6570篇
  2009年   6462篇
  2008年   8986篇
  2007年   9137篇
  2006年   8374篇
  2005年   7831篇
  2004年   6984篇
  2003年   6201篇
  2002年   6131篇
  2001年   7200篇
  2000年   5361篇
  1999年   4219篇
  1998年   3549篇
  1997年   3507篇
  1996年   2982篇
  1995年   3049篇
  1994年   2873篇
  1993年   2911篇
  1992年   3226篇
  1991年   3243篇
  1990年   3056篇
  1989年   3023篇
  1988年   3082篇
  1987年   2946篇
  1986年   2849篇
  1985年   3923篇
  1984年   4091篇
  1983年   3327篇
  1982年   3699篇
  1981年   3588篇
  1980年   3471篇
  1979年   3511篇
  1978年   3740篇
  1977年   3575篇
  1976年   3788篇
  1975年   3361篇
  1974年   3487篇
  1973年   3793篇
  1972年   2301篇
  1971年   1758篇
排序方式: 共有10000条查询结果,搜索用时 15 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