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   4722篇
  免费   142篇
  国内免费   16篇
化学   2963篇
晶体学   14篇
力学   241篇
数学   823篇
物理学   839篇
  2023年   40篇
  2022年   140篇
  2021年   135篇
  2020年   112篇
  2019年   99篇
  2018年   86篇
  2017年   91篇
  2016年   194篇
  2015年   150篇
  2014年   144篇
  2013年   252篇
  2012年   264篇
  2011年   291篇
  2010年   177篇
  2009年   156篇
  2008年   289篇
  2007年   278篇
  2006年   230篇
  2005年   247篇
  2004年   170篇
  2003年   163篇
  2002年   123篇
  2001年   54篇
  2000年   54篇
  1999年   45篇
  1998年   35篇
  1997年   33篇
  1996年   57篇
  1995年   48篇
  1994年   39篇
  1993年   38篇
  1992年   29篇
  1991年   30篇
  1990年   30篇
  1989年   32篇
  1988年   30篇
  1987年   41篇
  1986年   26篇
  1985年   40篇
  1984年   40篇
  1983年   20篇
  1982年   22篇
  1981年   27篇
  1980年   27篇
  1979年   19篇
  1978年   17篇
  1977年   29篇
  1975年   14篇
  1974年   13篇
  1858年   11篇
排序方式: 共有4880条查询结果,搜索用时 31 毫秒
1.
Journal of Optimization Theory and Applications - Pollution management models of Shallow Lake type identify a well-known class of infinite horizon optimal control problems, characterized by the...  相似文献   
2.
3.
Numerical Algorithms - We introduce a modulus-based formulation for vertical linear complementarity problems (VLCPs) with an arbitrary number ? of matrices. This formulation can be used to...  相似文献   
4.
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains.  相似文献   
5.
The development of biodegradable materials for tailored applications, particularly in the field of polymeric films and sheets, is a challenging technological goal as well as a contribution to help protect the environment. Poly(lactic) acid (PLA) is a promising substitute for several oil-based polymers; however, to overcome its thermal and mechanical drawbacks, researchers have developed solutions such as blending PLA with polybutylene adipate terephthalate (PBAT), which is capable of increasing the ductility of the final material. In this study, PLA/PBAT binary blends, with minimum possible content of nonrenewable materials, were examined from processing, thermal, morphological, and rheological perspective. An optimized PLA/PBAT ratio was chosen as the polymeric basis to obtain a biodegradable formulation by adding a biobased plasticizer and appropriate fillers to produce a micrometer film with tailored flexibility and tear resistance. The processing technology involved flat-die extrusion, followed by calendering. The tearing resistance of the produced film was investigated, and the results were compared with literature data. A study on the essential work of fracture was implemented to explore the mode III out-of-plane fracture resistance starting from a trouser tear test.  相似文献   
6.
7.
We prove that the arithmetic degree of a graded or local ring A is bounded above by the arithmetic degree of any of its associated graded rings with respect to ideal I in A. In particular, if Spec(A) is equidimensional and has an embedded component (i.e., A has an embedded associated prime ideal), then the normal cone of Spec(A) along V(I) has an embedded component too. This extends a result of W. M. Ruppert about embedded components of the tangent cone.Mathematics Subject Classification (2000): Primary 13H15, 13A30; Secondary 13D45, 14Q99  相似文献   
8.
In view of the growing interest for non-destructive tests of materials, geodynamical monitoring and in general remote sensing, there is a great effort to bring practical optical sensors from research labs to industrial and environmental applications. In this paper, we employ digital holographic technique as an efficient tool for evaluating the strain measurement capability of fiber Bragg gratings (FBG). A cantilever beam has been employed as a test structure under loading test. The strain measurements results obtained by fiber-based sensors have been compared to those obtained by using full-field digital holographic technique and point-wise strain gauge sensors glued on the same cantilever beam. A simple theoretical model is also presented to interpret and compare the experimental results coming from different techniques.  相似文献   
9.
The concept of strong interactions need not be limited to the sector of physics taken by QCD. While this domain is investigated by RHIC, LHC will be able to probe potential new strong interactions simultaneously: Finding the precise mechanism for electroweak symmetry breaking is one of the prime problems of physics. Intricately linked to this point is the question after the true nature or even the existence of the Higgs boson. Here, we present stronly interacting theories providing an explanation for the hierarchy problem and leading to a light composite Higgs boson, favoured by experimental data. Our variation of the standard model is consistent with precision data. We achieve this accordance by using technifermions in a higher representation of their gauge group. Anomaly conditions require at least one extra lepton family for some of the theories whereby they contain a natural dark matter candidate. We can accurately determine the masses of said leptons from experimental data.  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