全文获取类型
收费全文 | 277228篇 |
免费 | 4076篇 |
国内免费 | 846篇 |
专业分类
化学 | 146034篇 |
晶体学 | 4214篇 |
力学 | 12224篇 |
综合类 | 1篇 |
数学 | 32922篇 |
物理学 | 86755篇 |
出版年
2021年 | 2134篇 |
2020年 | 2454篇 |
2019年 | 2696篇 |
2018年 | 3657篇 |
2017年 | 3428篇 |
2016年 | 5388篇 |
2015年 | 3723篇 |
2014年 | 5276篇 |
2013年 | 12877篇 |
2012年 | 10773篇 |
2011年 | 12730篇 |
2010年 | 8634篇 |
2009年 | 8236篇 |
2008年 | 11440篇 |
2007年 | 11467篇 |
2006年 | 10675篇 |
2005年 | 9851篇 |
2004年 | 8870篇 |
2003年 | 7691篇 |
2002年 | 7438篇 |
2001年 | 7734篇 |
2000年 | 5931篇 |
1999年 | 4637篇 |
1998年 | 3900篇 |
1997年 | 3770篇 |
1996年 | 3735篇 |
1995年 | 3263篇 |
1994年 | 3256篇 |
1993年 | 3361篇 |
1992年 | 3477篇 |
1991年 | 3616篇 |
1990年 | 3357篇 |
1989年 | 3300篇 |
1988年 | 3290篇 |
1987年 | 3175篇 |
1986年 | 2974篇 |
1985年 | 4127篇 |
1984年 | 4290篇 |
1983年 | 3387篇 |
1982年 | 3681篇 |
1981年 | 3582篇 |
1980年 | 3453篇 |
1979年 | 3551篇 |
1978年 | 3627篇 |
1977年 | 3525篇 |
1976年 | 3665篇 |
1975年 | 3315篇 |
1974年 | 3349篇 |
1973年 | 3377篇 |
1972年 | 2320篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
881.
A Finite Element Galerkin Method for a Unidimensional Single-Phase Nonlinear Stefan Problem with Dirichlet Boundary Conditions 总被引:1,自引:0,他引:1
Based on straightening the free boundary, an H1-Galerkin methodis proposed and analysed for a single-phase nonlinear Stefanproblem with Dirichlet boundary conditions. Optimal H1 estimatesfor continuous-time Galerkin approximations are derived. 相似文献
882.
883.
884.
While in the companion paper (Tonani, C. & Righetti, P. G., Electrophoresis 1991, 12, 1011-1021) we gave the general outline of our new computer program, immobilized pH gradients (IPG) simulator, able to simulate and optimize linear pH gradients for isoelectric focusing in immobilized pH gradients, in the present report we extend the application of such a program to: (i) convex exponential gradients, (ii) logarithmic and (iii) polynomial gradients. Such gradients are meant to give equal space to protein spots in complex protein mixtures (e.g., cell lysates, biological fluids) and follow the statistical distribution of protein pI values along the pH axis. They will prove of fundamental importance in two-dimensional maps, both because they optimize the spreading of spots in the two-dimensional plane and because of the excellent reproducibility of immobilized pH gradients. The following concave exponential recipes are given: pH 3-8, pH 3-9, pH 3-10, pH 3-11, pH 4-7, pH 4-8, pH 4-9, pH 4-10, pH 4-11, pH 5-8, pH 5-9, and pH 5-10, as well as the most extended pH 2.5-11 interval. Two interesting logarithmic gradients are described: pH 3-6 and pH 3-7 and one sigmoidal (derived with a polynomial of 5th degree): pH 3-11. 相似文献
885.
E. S. Moskalenko M. Larsson K. F. Karlsson P. O. Holtz B. Monemar W. V. Schoenfeld P. M. Petroff 《Physics of the Solid State》2007,49(10):1995-1998
We report on low-temperature microphotoluminescence (μ-PL) measurements of InAs/GaAs quantum dots (QDs) exposed to a lateral
external electric field. It is demonstrated that the QDs’ PL signal could be increased severalfold by altering the external
and/or the internal electric field, which could be changed by an additional infrared laser. A model which accounts for a substantially
faster lateral transport of the photoexcited carriers achieved in an external electric field is employed to explain the observed
effects. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity
measured in our experiment—a finding which could be used to tailor the properties of QD-based optoelectronic applications.
The text was submitted by the authors in English. 相似文献
886.
N. B. Voznesensky E. V. Gavrilov A. P. Zhevlakov V. K. Kirillovskiĭ P. V. Orlov 《Technical Physics》2007,52(2):271-275
Methods and schemes to inspect the EUV mirror shape are developed on the basis of a point diffraction interferometer with computer processing of interferograms. A measurement accuracy to within 0.001 of a wavelength in the visual range is achieved. 相似文献
887.
In this note we make a correction in the paper [1] by two of the authors. Specifically we modify an auxiliary localization
result and prove that the applications to the saturation theory of some outstanding conservative operators remain valid. Moreover,
we enrich a corollary dealing with the well-known Szász-Mirakjan operators.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
888.
José A. Anquela Teresa Cortés Miguel Gómez-Lozano Mercedes Siles-Molina 《Acta Mathematica Hungarica》2004,103(3):177-196
We investigate the basic properties of the different socles that can be considered in not necessarily semiprime associative
systems. Among other things, we show that the socle defined as the sum of minimal (or minimal and trivial) inner ideals is
always an ideal. When trivial inner ideals are included, this inner socle contains the socles defined in terms of minimal
left or right ideals.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
889.
P. Danchev 《Lithuanian Mathematical Journal》2007,47(2):129-134
We prove the following theorem: Any abelian p-group is an n-Σ-group which is a strong ω-elongation of a totally projective group by a p
ω+n
-projective group precisely when it is totally projective. In particular, each p-torsion p
ω+n
-projective n-Σ-group is a direct sum of countable p-groups of length not exceeding ω + n and vice versa. These two claims generalize our recent results in [6] and [7].
Published in Lietuvos Matematikos Rinkinys, Vol. 47, No. 2, pp. 155–162, April–June, 2007. 相似文献
890.
The steady-state two-phase flow non-linear equation is considered in the case when one of phases has low effective permeability in some periodic set, while on the complementary set it is high; the second phase has no contrast of permeabilities in different zones. A homogenization procedure gives the homogenized model with macroscopic effective permeability of the second phase depending on the gradient and on the second order derivatives of the macroscopic pressure of the first phase. This effect cannot be obtained by classical (one small parameter) homogenization. To cite this article: G.P. Panasenko, G. Virnovsky, C. R. Mecanique 331 (2003). 相似文献