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   56904篇
  免费   3167篇
  国内免费   747篇
化学   36886篇
晶体学   316篇
力学   2106篇
综合类   41篇
数学   8486篇
物理学   12983篇
  2023年   529篇
  2022年   408篇
  2021年   679篇
  2020年   977篇
  2019年   896篇
  2018年   1232篇
  2017年   1019篇
  2016年   1854篇
  2015年   1730篇
  2014年   1835篇
  2013年   3448篇
  2012年   4051篇
  2011年   4166篇
  2010年   2563篇
  2009年   2194篇
  2008年   3486篇
  2007年   3441篇
  2006年   3088篇
  2005年   2943篇
  2004年   2530篇
  2003年   2019篇
  2002年   1809篇
  2001年   1083篇
  2000年   940篇
  1999年   718篇
  1998年   534篇
  1997年   502篇
  1996年   640篇
  1995年   416篇
  1994年   472篇
  1993年   473篇
  1992年   485篇
  1991年   411篇
  1990年   378篇
  1989年   388篇
  1988年   301篇
  1987年   302篇
  1986年   262篇
  1985年   418篇
  1984年   368篇
  1983年   259篇
  1982年   347篇
  1981年   331篇
  1980年   289篇
  1979年   277篇
  1978年   253篇
  1976年   270篇
  1975年   243篇
  1974年   253篇
  1973年   239篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
Optical and Quantum Electronics - In the past few decades, the academic research and industrial synergy is dramatically accelerating to conceptualize high data rate services. The congestion in the...  相似文献   
3.
Fuzzy Optimization and Decision Making - Cost-allocation problems in a fixed network are concerned with distributing the costs for use by a group of clients who cooperate in order to reduce such...  相似文献   
4.
Journal of Optimization Theory and Applications - We consider the problem of maximization of metabolite production in bacterial cells formulated as a dynamical optimal control problem (DOCP)....  相似文献   
5.
顾顺心  姜琴  施鹏飞 《化学进展》2022,34(9):1957-1971
铱(Ⅲ)配合物因其发光量子产率高且波长易调控、发光寿命长和光稳定性好的特点,在发光材料领域备受关注。铱(Ⅲ)配合物细胞渗透能力强,能靶向多种细胞组织并影响其结构和功能,表现出独特的抗肿瘤活性,是目前金属抗肿瘤药物特别是PDT光敏剂方向的研究热点。本文重点关注铱(Ⅲ)配合物的结构对其发光性能与抗肿瘤性能的影响,综述了近期铱(Ⅲ)配合物在生物成像、探针与传感、抗肿瘤诊疗等领域的研究进展,并对目前研究中存在的问题及其应用前景进行探讨和展望。  相似文献   
6.
Mathematical Programming - Minimizing a convex function of a measure with a sparsity-inducing penalty is a typical problem arising, e.g., in sparse spikes deconvolution or two-layer neural networks...  相似文献   
7.

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   
8.
9.
Algebras and Representation Theory - For a smooth irreducible affine algebraic variety we study a class of gauge modules admitting compatible actions of both the algebra $\mathcal {A}$ of functions...  相似文献   
10.
Although tuning band structure of optoelectronic semiconductor-based materials by means of doping single defect is an important approach for potential photocatalysis application,C-doping or oxygen vacancy(Vo)as a single defect in ZnO still has limitations for photocatalytic activity.Meanwhile,the influence of co-existence of various defects in ZnO still lacks sufficient studies.Therefore,we investigate the photocatalytic properties of ZnOx C0.0625(x=0.9375,0.875,0.8125),confirming that the co-effect of various defects has a greater enhancement for photocatalytic activity driven by visible-light than the single defect in ZnO.To clarify the underlying mechanism of co-existence of various defects in ZnO,we perform systematically the electronic properties calculations using density functional theory.It is found that the coeffect of C-doping and Vo in ZnO can achieve a more controllable band gap than doping solely in ZnO.Moreover,the impact of the effective masses of ZnOxC0.0625(x=0.9375,0.875,0.8125)is also taken into account.In comparison with heavy Vo concentrations,the light Vo concentration(x=0.875)as the optimal component together with C-doping in ZnO,can significantly improve the visible-light absorption and benefit photocatalytic activity.  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