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   2361篇
  免费   54篇
  国内免费   27篇
化学   1235篇
晶体学   13篇
力学   82篇
数学   462篇
物理学   650篇
  2023年   6篇
  2022年   27篇
  2021年   63篇
  2020年   38篇
  2019年   47篇
  2018年   66篇
  2017年   52篇
  2016年   79篇
  2015年   59篇
  2014年   79篇
  2013年   109篇
  2012年   152篇
  2011年   144篇
  2010年   105篇
  2009年   102篇
  2008年   161篇
  2007年   153篇
  2006年   127篇
  2005年   133篇
  2004年   138篇
  2003年   75篇
  2002年   80篇
  2001年   56篇
  2000年   37篇
  1999年   37篇
  1998年   45篇
  1997年   33篇
  1996年   22篇
  1995年   26篇
  1994年   21篇
  1993年   14篇
  1992年   12篇
  1991年   7篇
  1990年   12篇
  1989年   8篇
  1988年   7篇
  1985年   6篇
  1984年   5篇
  1983年   4篇
  1981年   7篇
  1980年   8篇
  1979年   4篇
  1978年   5篇
  1977年   6篇
  1976年   4篇
  1975年   7篇
  1972年   4篇
  1971年   7篇
  1970年   9篇
  1968年   7篇
排序方式: 共有2442条查询结果,搜索用时 31 毫秒
131.
132.
Let be an oriented Jordan smooth curve and a diffeomorphism of onto itself which has an arbitrary nonempty set of periodic points. We prove criteria for one-sided invertibility of the binomial functional operator
wherea andb are continuous functions,I is the identity operator,W is the shift operator,Wf=fo, on a reflexive rearrangement-invariant spaceX() with Boyd indices X , X and Zippin indicesp x,q x satisfying inequalities
Partially supported by F.C.T. (Portugal) grant PRAXIS XXI/BPD/22006/99.Partially supported by CONCACYT (México) grant, Cátedra Patrimonial, No. 990017-EX., nivel II.  相似文献   
133.
An iterative method for the minimization of convex functions f :n , called a Newton Bracketing (NB) method, is presented. The NB method proceeds by using Newton iterations to improve upper and lower bounds on the minimum value. The NB method is valid for n = 1, and in some cases for n > 1 (sufficient conditions given here). The NB method is applied to large scale Fermat–Weber location problems.  相似文献   
134.
A room temperature sonochemical method for the preparation of GaSb nanoparticles using less hazardous Ga and antimony chloride (SbCl(3)) as the precursors has been described. The formation of GaSb has been confirmed by means of XRD, EDAX, and XPS characterization. TEM and SAED results show that the as-prepared solid consists of nanosized GaSb crystals with sizes in the range 20-30 nm. The photoacoustic spectrum result reveals that the GaSb nanoparticles have a direct band gap of about 1.21 eV. On the basis of the control experiments and the extreme conditions produced by ultrasound, an ultrasound-assisted in-situ reduction/combination mechanism has been proposed to explain the reaction.  相似文献   
135.
[reaction: see text] The reduction of benzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) 1 with Na(2)S(2)O(4) or SnCl(2) is suggested to proceed via intermediate N-nitrosobenzotriazoles 3 to afford benzotriazoles 2. The (15)N-labeling experiments exhibit that the N-3 atom of the tetrazine ring is incorporated into the nitroso group of 3 that is ultimately released into solution. It is possible that the biological activity of BTDOs is due to their ability to release nitrosating species, i.e., N-nitrosotriazol 3 or HNO(2), in the course of reduction.  相似文献   
136.
We present experimental evidence that pressure solution creep does not establish a steady-state interface microstructure as previously thought. Conversely, pressure solution controlled strain and the characteristic length scale of interface microstructures grow as the cubic root of time. Transient creep with the same scaling is known in metallurgy (Andrade creep). The apparent universal scaling of pressure solution transient creep is explained using an analogy with spinodal dewetting.  相似文献   
137.
The phase diagram of a polydisperse mixture of uniaxial rodlike and platelike hard parallelepipeds is determined for aspect ratios kappa=5 and 15. All particles have equal volume, and polydispersity is introduced in a highly symmetric way. The corresponding binary mixture is known to have a biaxial phase for kappa=15, but to be unstable against demixing into two uniaxial nematics for kappa=5. The phase diagram for kappa=15 is qualitatively similar to that of the binary mixture, regardless of the amount of polydispersity, while for kappa=5 a sufficient amount of polydispersity stabilizes the biaxial phase. This provides clues for designing an experiment to observe this long searched biaxial phase.  相似文献   
138.
Self-written waveguides in photopolymerizable resins   总被引:2,自引:0,他引:2  
We study the optically induced growth and interaction of self-written waveguides in a photopolymerizable resin. We investigate experimentally how the interaction depends on the mutual coherence and the relative power of the input beams and suggest an improved analytical model that describes the growth of single waveguides and the main features of their interaction in photosensitive materials.  相似文献   
139.
140.
Models of quantum and classical particles on a lattice d are considered. The classical model is obtained from the corresponding quantum model when the reduced mass of the particle m = / #x210F;2 tends to infinity. For these models, the convergence of the Euclidean Gibbs states, when m + , is described in terms of the weak convergence of local Gibbs specifications, determined by conditional Gibbs measures. In fact, it is shown that all conditional Gibbs measures of the quantum model weakly converge to the conditional Gibbs measures of the classical model. A similar convergence of the periodic Gibbs measures and, as a result, of the order parameters, for such models with pair interactions possessing the translation invariance, has also been shown.  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