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   331627篇
  免费   3076篇
  国内免费   937篇
化学   165992篇
晶体学   5377篇
力学   15584篇
综合类   7篇
数学   38706篇
物理学   109974篇
  2021年   3143篇
  2020年   3356篇
  2019年   3780篇
  2018年   5213篇
  2017年   5455篇
  2016年   7403篇
  2015年   4162篇
  2014年   7055篇
  2013年   15952篇
  2012年   12453篇
  2011年   14902篇
  2010年   11057篇
  2009年   10961篇
  2008年   13294篇
  2007年   13253篇
  2006年   12195篇
  2005年   10578篇
  2004年   9892篇
  2003年   8726篇
  2002年   8712篇
  2001年   10417篇
  2000年   7681篇
  1999年   5985篇
  1998年   4988篇
  1997年   4833篇
  1996年   4503篇
  1995年   3888篇
  1994年   3843篇
  1993年   3712篇
  1992年   4115篇
  1991年   4324篇
  1990年   4107篇
  1989年   4020篇
  1988年   3790篇
  1987年   3935篇
  1986年   3692篇
  1985年   4645篇
  1984年   4695篇
  1983年   3890篇
  1982年   3985篇
  1981年   3701篇
  1980年   3657篇
  1979年   3931篇
  1978年   3914篇
  1977年   3918篇
  1976年   3893篇
  1975年   3688篇
  1974年   3635篇
  1973年   3658篇
  1972年   2614篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
151.
152.
For two types of qutrits specified by the dynamical symmetry SU(3) and SU(2), we consider the difference in entanglement caused by the lack of quantum observables in the latter case. In particular, we show that the SU(2) qutrits can have specific separable entanglement caused by quantum correlations of intrinsic degrees of freedom in a single party without interparty correlations.  相似文献   
153.
The following areal objects are considered: an ether thread contracting two material points and a multidimensional ether fibre in the pseudo-Euclidean world of events. An ether space-time model with an arbitrarily determined Riemannian metric is constructed and the problem of the λ term in Einstein equations is discussed in this regard.  相似文献   
154.
The supersymetric path integrals in solving the problem of relativistic spinning particle interacting with pseudoscalar potentials is examined. The relative propagator is presented by means of path integral, where the spin degrees of freedom are described by odd Grassmannian variables and the gauge invariant part of the effective action has a form similar to the standard pseudoclassical action given by Berezin and Marinov. After integrating over fermionic variables (Grassmannian variables), the problem is reduced to a nonrelativistic one with an effective supersymetric potential. Some explicit examples are considered, where we have extracted the energy spectrum of the electron and the wave functions. PACS numbers: 03.65. Ca-Formalism, 03.65. Db-Functional analytical methods, 03.65. Pm-Relativistic wave equations.  相似文献   
155.
156.
The author proves the existence and uniqueness of a generalized solution of a nonlocal problem with an integral condition for a hyperbolic equation with n spatial variables. This work is a continuation of the studies started in [3–5], where the solvability problem of nonlocal problems with an integral condition was studied for hyperbolic equations on the plane. __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 33, Suzdal Conference-2004, Part 1, 2005.  相似文献   
157.
158.
159.
Phytochemical investigation of the aerial parts of three Baccharis species (Asteraceae family) was performed using HPLC and chemometric methods, with the objective of distinguishing between three morphologically very similar species: Baccharis genistelloides Persoon var. trimera (Less.) DC, B. milleflora (Less.) DC and B. articulata (Lam.) Persoon. With the help of Principal Component Analysis (PCA) and variance weights, it was possible to characterize the chromatographic profiles of the alcoholic extracts of the three species. Application of Soft Independent Modeling of Class Analogy (SIMCA) and K-Nearest Neighbor (KNN) methods on a training set of 74 extracts resulted in models that correctly classified all eight samples in an independent test set.  相似文献   
160.
Diffuse x-ray scattering (DXS) is used to study the formation of microdefects (MDs) in heat-treated dislocation-free large-diameter silicon wafers with vacancies. The DXS method is shown to be efficient for investigating MDs in silicon single crystals. Specific defects, such as impurity clouds, are found to form in the silicon wafers during low-temperature annealing at 450°C. These defects are oxygen-rich regions in the solid solution with diffuse coherent interfaces. In the following stages of decomposition of the supersaturated solid solution, oxide precipitates form inside these regions and the impurity clouds disappear. As a result of the decomposition of the supersaturated solid solution of oxygen, interstitial MDs form in the silicon wafers during multistep heat treatment. These MDs lie in the {110} planes and have nonspherical displacement fields. The volume density and size of MDs forming in the silicon wafers at various stages of the decomposition are determined.  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