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   30523篇
  免费   164篇
  国内免费   277篇
化学   11527篇
晶体学   273篇
力学   1414篇
综合类   12篇
数学   9112篇
物理学   8626篇
  2021年   44篇
  2020年   45篇
  2019年   35篇
  2018年   1196篇
  2017年   1464篇
  2016年   756篇
  2015年   585篇
  2014年   498篇
  2013年   733篇
  2012年   3198篇
  2011年   2410篇
  2010年   1852篇
  2009年   1590篇
  2008年   660篇
  2007年   714篇
  2006年   690篇
  2005年   4522篇
  2004年   3985篇
  2003年   2346篇
  2002年   543篇
  2001年   314篇
  2000年   137篇
  1999年   198篇
  1998年   136篇
  1997年   92篇
  1996年   74篇
  1995年   69篇
  1994年   76篇
  1993年   54篇
  1992年   202篇
  1991年   180篇
  1990年   161篇
  1989年   138篇
  1988年   120篇
  1987年   80篇
  1986年   58篇
  1985年   60篇
  1984年   45篇
  1983年   37篇
  1982年   45篇
  1979年   41篇
  1978年   35篇
  1976年   89篇
  1975年   47篇
  1974年   45篇
  1973年   59篇
  1972年   43篇
  1969年   38篇
  1968年   36篇
  1966年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Germline and somatic instability of the human genome was studied, using synthetic oligonucleotides specific for simple repeat motifs. The following probes were used: (GTG)5, (GACA)4, (GATA)4, (CT)8, (TTAGGG)3, (GT)8, (GAA)6 and (GGAT)4. Each of them is unique with respect to the target regions recognized in the genome. Thus compilation of the various fingerprint data provides a complex map of the genome (and its deviations). While the fingerprints of differentiated somatic tissues never showed any alterations, in tumor tissues (namely gliomas) many changes could be detected. Most of the latter reflect secondary karyological aberrations. In nearly one third of the gliomas, drastically amplified and apparently monomorphic DNA fragments were identified. This marker should make it possible to deal with causal pathogenetic mechanisms as well as novel diagnostic strategies.  相似文献   
52.
53.
We investigate the origin of the attraction in theK¯K channel around the threshold by introducing an additional channel to theππ andK¯K channels in a separable potential formalism assuming, in general, no direct interaction in theK¯K channel. To reproduce the features of the data, we find that the threshold of the additional channel is much above thef 0(975) meson position. We show that this three-channel problem can be reduced to an effective two-channel problem where thef 0(975) behaves as if it were aK¯K molecule bound by the coupling to the exotic channel. This picture is also supported by the fact that a single pole only, in the complexK¯K momentum plane, is associated to thef 0(975) meson. Various physical observables, like the decay branching ratio and theK¯K scattering length, are then discussed in an effective two-channel framework.  相似文献   
54.
The invariance of the geometric mean G with respect to the Lagrangian mean-type mapping (Lf,Lg), i.e. the equation G○(Lf,Lg)=G, is considered. We show that the functions f and g must be of high class regularity. This fact allows to reduce the problem to a differential equation and determine the second derivatives of the generators f and g.  相似文献   
55.
In the paper we indicate an error made in the proof of the main result of the paper [M.A. Darwish, On quadratic integral equation of fractional orders, J. Math. Anal. Appl. 311 (2005) 112-119]. Moreover, we provide correct proof of a slightly modified version of the mentioned result. The main tool used in our proof is the technique associated with the Hausdorff measure of noncompactness.  相似文献   
56.
The strong suppression of high-pT hadrons observed in heavy ion collisions at RHIC indicates the interaction of high energy partons with a dense colored medium prior to hadronization. We review the main results from the high-pT hadron analysis at RHIC and what they tell us about the medium. We then concentrate on the new possibilities that the wider kinematic range at the LHC will offer and how they will help us to better characterize the medium produced in these collisions.  相似文献   
57.
In this paper we deal with nonlinear second-order boundary value problems with impulses. The impulsive functions depend implicitly on the different considered variables and the boundary value conditions are nonlinear. In both cases functional dependence on the solution is allowed. The existence results follow from the existence of a pair of well-ordered lower and upper solutions.  相似文献   
58.
We study linear dynamical systems with multidimensional time in Banach spaces. Using Taylor functional calculus we prove that under additional assumptions hyperbolic systems have shadowing property.  相似文献   
59.
A Fubini theorem     
Let I0 be the σ-ideal of subsets of a Polish group generated by Borel sets which have perfectly many pairwise disjoint translates. We prove that a Fubini-type theorem holds between I0 and the σ-ideals of Haar measure zero sets and of meager sets. We use this result to give a simple proof of a generalization of a theorem of Balcerzak-Ros?anowski-Shelah stating that I0 on N2 strongly violates the countable chain condition.  相似文献   
60.
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