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   4245篇
  免费   180篇
  国内免费   37篇
化学   2827篇
晶体学   27篇
力学   139篇
综合类   1篇
数学   765篇
物理学   703篇
  2023年   27篇
  2022年   37篇
  2021年   119篇
  2020年   106篇
  2019年   99篇
  2018年   111篇
  2017年   75篇
  2016年   161篇
  2015年   153篇
  2014年   167篇
  2013年   291篇
  2012年   350篇
  2011年   369篇
  2010年   233篇
  2009年   228篇
  2008年   315篇
  2007年   281篇
  2006年   250篇
  2005年   192篇
  2004年   168篇
  2003年   142篇
  2002年   105篇
  2001年   45篇
  2000年   41篇
  1999年   31篇
  1998年   22篇
  1997年   19篇
  1996年   36篇
  1995年   32篇
  1994年   25篇
  1993年   29篇
  1992年   28篇
  1991年   18篇
  1990年   15篇
  1989年   8篇
  1988年   14篇
  1986年   10篇
  1985年   9篇
  1984年   9篇
  1983年   5篇
  1982年   9篇
  1981年   5篇
  1980年   6篇
  1979年   8篇
  1978年   7篇
  1977年   6篇
  1976年   6篇
  1975年   6篇
  1974年   10篇
  1970年   4篇
排序方式: 共有4462条查询结果,搜索用时 187 毫秒
1.
Statistical Inference for Stochastic Processes - The class of autoregressive (AR) processes is extensively used to model temporal dependence in observed time series. Such models are easily...  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.
4.
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   
5.
Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct...  相似文献   
6.
Journal of Thermal Analysis and Calorimetry - Due to the huge variety of therapeutic properties found in plant leaves, many of these are widely used in traditional medicine. Among these plants,...  相似文献   
7.
The emergence of untreatable drug-resistant strains of Mycobacterium tuberculosis is a major public health problem worldwide, and the identification of new efficient treatments is urgently needed. Mycobacterium tuberculosis cytochrome P450 CYP121A1 is a promising drug target for the treatment of tuberculosis owing to its essential role in mycobacterial growth. Using a rational approach, which includes molecular modelling studies, three series of azole pyrazole derivatives were designed through two synthetic pathways. The synthesized compounds were biologically evaluated for their inhibitory activity towards M. tuberculosis and their protein binding affinity (KD). Series 3 biarylpyrazole imidazole derivatives were the most effective with the isobutyl ( 10 f ) and tert-butyl ( 10 g ) compounds displaying optimal activity (MIC 1.562 μg/mL, KD 0.22 μM ( 10 f ) and 4.81 μM ( 10 g )). The spectroscopic data showed that all the synthesised compounds produced a type II red shift of the heme Soret band indicating either direct binding to heme iron or (where less extensive Soret shifts are observed) putative indirect binding via an interstitial water molecule. Evaluation of biological and physicochemical properties identified the following as requirements for activity: LogP >4, H-bond acceptors/H-bond donors 4/0, number of rotatable bonds 5–6, molecular volume >340 Å3, topological polar surface area <40 Å2.  相似文献   
8.
Analytical and Bioanalytical Chemistry - This study aimed to determine simultaneously five major street cocaine adulterants (caffeine, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human...  相似文献   
9.
Metal–organic frameworks (MOFs) have shown great potential in gas separation and storage, and the design of MOFs for these purposes is an on-going field of research. Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a valuable technique for characterizing these functional materials. It can provide a wide range of structural and motional insights that are complementary to and/or difficult to access with alternative methods. In this Concept article, the recent advances made in SSNMR investigations of small gas molecules (i.e., carbon dioxide, carbon monoxide, hydrogen gas and light hydrocarbons) adsorbed in MOFs are discussed. These studies demonstrate the breadth of information that can be obtained by SSNMR spectroscopy, such as the number and location of guest adsorption sites, host–guest binding strengths and guest mobility. The knowledge acquired from these experiments yields a powerful tool for progress in MOF development.  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