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   62202篇
  免费   17981篇
  国内免费   2028篇
化学   66833篇
晶体学   235篇
力学   3236篇
综合类   135篇
数学   4704篇
物理学   7068篇
  2024年   419篇
  2023年   4294篇
  2022年   1967篇
  2021年   3057篇
  2020年   5158篇
  2019年   2948篇
  2018年   2721篇
  2017年   1120篇
  2016年   6199篇
  2015年   6165篇
  2014年   5811篇
  2013年   6199篇
  2012年   4643篇
  2011年   2556篇
  2010年   4412篇
  2009年   4244篇
  2008年   2083篇
  2007年   1716篇
  2006年   1077篇
  2005年   861篇
  2004年   653篇
  2003年   586篇
  2002年   583篇
  2001年   497篇
  2000年   372篇
  1999年   397篇
  1998年   313篇
  1997年   357篇
  1996年   380篇
  1995年   377篇
  1994年   291篇
  1993年   370篇
  1992年   266篇
  1991年   239篇
  1989年   198篇
  1988年   195篇
  1981年   185篇
  1980年   223篇
  1979年   204篇
  1978年   213篇
  1977年   334篇
  1976年   383篇
  1975年   473篇
  1974年   491篇
  1973年   309篇
  1972年   381篇
  1971年   361篇
  1970年   551篇
  1969年   418篇
  1968年   462篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Two-function upward-downward minimax theorems are derived which contain Simons upward-downward minimax theorem as well as Domokos minimax theorem as special cases. Here the convexity assumptions on two functions are given by mixing up their values as means proposed by Lin and Quan.  相似文献   
52.
The field of medicinal inorganic chemistry is rapidly advancing. In particular organometallic complexes have much potential as therapeutic and diagnostic agents. The carbon‐bound and other ligands allow the thermodynamic and kinetic reactivity of the metal ion to be controlled and also provide a scaffold for functionalization. The establishment of structure–activity relationships and elucidation of the speciation of complexes under conditions relevant to drug testing and formulation are crucial for the further development of promising medicinal applications of organometallic complexes. Specific examples involving the design of ruthenium and osmium arene complexes as anticancer agents are discussed.  相似文献   
53.
In this study, a genetically encoded bioluminescent indicator for ERK2 dimer was developed with the split Renilla luciferase complementation method, in which the formation of ERK2 dimer induces a spontaneous emission of bioluminescence in living cells. In response to extracellular stimuli, such as epidermal growth factor (EGF) or 17β‐estradiol (E2), extracellular signal‐regulated kinase 2 (ERK2) is phosphorylated by its upstream kinase MEK, and also phosphorylates its substrates in various regions of the cell, including the nucleus. Phosphorylated ERK2 is led to form its dimer, thereby transporting itself into the nucleus. We demonstrated with the indicator that stimulation with EGF or E2 induces the formation of ERK2 dimer in living MCF‐7 cells. The dynamics of this dimer formation was examined and discussed.  相似文献   
54.
The notion of weak attractive ligand–polymer interactions is introduced, and its potential application, importance, and conceptual links with “cooperative” ligand–substrate interactions are discussed. Synthetic models of weak attractive ligand–polymer interactions are described, in which intramolecular weak C? H???F? C interactions (the existence of which remains contentious) have been detected by NMR spectroscopy and neutron and X‐ray diffraction experiments. These C? H???F? C interactions carry important implications for the design of catalysts for olefin polymerization, because they provide support for the practical feasibility of ortho‐F???Hβ ligand–polymer contacts proposed for living Group 4 fluorinated phenoxyimine catalysts. The notion of weak attractive noncovalent interactions between an “active” ligand and the growing polymer chain is a novel concept in polyolefin catalysis.  相似文献   
55.
56.
57.
Gallin Peter Prof. Dr. 《ZDM》2003,35(3):110-119
In order to emphasize functional thinking in mathematical education, arguments are brought forward for an early and frequent use of tree diagrams in teaching stochastics. Since set and tree diagrams can be regarded as two sides of the same matter, Bayes’ theorem, which is strongly associated with predicative set diagrams, need not be dealt with explicitly any longer. Set diagrams are replaced by tree diagrams that are labelled in detail and by tree inversion as a functional instrument of dealing with conditioned probabilities. This technique is demonstrated by three typical problems in the context of conditioned probability. Finally, two letters by Pascal to Fermat are analysed in order to illustrate that predicative and functional approaches were already pursued in the early stages of probability calculus in the 17th century.  相似文献   
58.
59.
This paper is concerned with a class of nonlinear delay partial difference equations with variable coefficients, which may change sign. By making use of frequency measures, some new oscillatory criteria are established. This is the first time oscillation of these partial difference equations is discussed by employing frequency measures.   相似文献   
60.
This paper presents the preliminary results obtained using an Electron Paramagnetic Resonance imaging apparatus operating at 280 MHz. The acquisition technique and the procedure used to obtain the spin density spatial localization are presented and specimen images of extended samples are given. The accuracy of the images and the spatial resolution are also discussed.  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