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   37169篇
  免费   440篇
  国内免费   327篇
化学   16164篇
晶体学   314篇
力学   1611篇
综合类   12篇
数学   10414篇
物理学   9421篇
  2022年   86篇
  2021年   179篇
  2020年   202篇
  2019年   202篇
  2018年   1360篇
  2017年   1615篇
  2016年   1005篇
  2015年   835篇
  2014年   771篇
  2013年   1229篇
  2012年   3676篇
  2011年   2922篇
  2010年   2173篇
  2009年   1847篇
  2008年   1048篇
  2007年   1097篇
  2006年   1042篇
  2005年   4810篇
  2004年   4243篇
  2003年   2573篇
  2002年   714篇
  2001年   423篇
  2000年   182篇
  1999年   244篇
  1998年   164篇
  1997年   121篇
  1996年   111篇
  1995年   91篇
  1994年   108篇
  1993年   70篇
  1992年   219篇
  1991年   213篇
  1990年   196篇
  1989年   164篇
  1988年   146篇
  1987年   104篇
  1986年   69篇
  1985年   92篇
  1984年   105篇
  1983年   62篇
  1982年   67篇
  1980年   64篇
  1979年   68篇
  1978年   67篇
  1977年   70篇
  1976年   113篇
  1975年   77篇
  1974年   75篇
  1973年   87篇
  1972年   67篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
Massoumi  Sina  Challamel  Noël  Lerbet  Jean  Wautier  Antoine  Nicot  François  Darve  Félix 《Meccanica》2022,57(8):2043-2066
Meccanica - This study is an attempt towards a better understanding of the length scale effects on the bending response of the granular beams. To this aim, a unidimensional discrete granular chain...  相似文献   
2.

Organisations are concerned about measuring the performance of the product/service they deliver to their customers. In all types of organisations, if a proper performance assessment is to be developed, it should be measured in different dimensions. At University, the new study programs include the development and assessment of transversal competences due to their importance in enhancing the abilities and improving the employability of students. The achievement of transversal competences can be assessed in different levels/stages; for example, the 1st and 2nd years of a Bachelor’s degree; the 3rd and 4th years of a Bachelor’s degree and at Master’s level. The purpose of this paper is to integrate the research into performance management in organisations to develop an approach consisting of four components (a methodology, a solid and integrated performance management framework, graphical diagrams and quantitative techniques) to assess and manage the achievement of transversal competences through the different levels of study using a consolidated approach. The proposal uses the Analytic Network Process (ANP) to model dependences and feedback among the elements of the competences.

  相似文献   
3.
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   
4.
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,...  相似文献   
5.
6.
7.
8.
Maleimide chemistry stands out in the bioconjugation toolbox by virtue of its synthetic accessibility, excellent reactivity, and practicability. The second-generation of clinically approved antibody–drug conjugates (ADC) and much of the current ADC pipeline in clinical trials contain the maleimide linkage. However, thiosuccinimide linkages are now known to be less robust than once thought, and ergo, are correlated with suboptimal pharmacodynamics, pharmacokinetics, and safety profiles in some ADC constructs. Rational design of novel generations of maleimides and maleimide-type reagents have been reported to address the shortcomings of classical maleimides, allowing for the formation of robust bioconjugate linkages. This review highlights the main strategies for rational reagent design that have allowed irreversible bioconjugations in cysteines, reversible labelling strategies and disulfide re-bridging.  相似文献   
9.
The reaction of N,C,N-chelated stibinidene ArSb ( 1 ) (Ar=C6H3-2,6-(CH=NtBu)2) with selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by an antimony(I) compound.  相似文献   
10.
The design and synthesis of two families of molecular-gear prototypes is reported, with the aim of assembling them into trains of gears on a surface and ultimately achieving controlled intermolecular gearing motion. These piano-stool ruthenium complexes incorporate a hydrotris(indazolyl)borate moiety as tripodal rotation axle and a pentaarylcyclopentadienyl ligand as star-shaped cogwheel, equipped with five teeth ranging from pseudo-1D aryl groups to large planar 2D paddles. A divergent synthetic approach was followed, starting from a pentakis(p-bromophenyl)cyclopentadienyl ruthenium(II) complex as key precursor or from its iodinated counterpart, obtained by copper-catalyzed aromatic Br/I exchange. Subsequent fivefold cross-coupling reactions with various partners allowed high structural diversity to be reached and yielded molecular-gear prototypes with aryl-, carbazole-, BODIPY- and porphyrin-derived teeth of increasing size and length.  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