全文获取类型
收费全文 | 33557篇 |
免费 | 1143篇 |
国内免费 | 1010篇 |
专业分类
化学 | 7867篇 |
晶体学 | 888篇 |
力学 | 782篇 |
综合类 | 77篇 |
数学 | 22269篇 |
物理学 | 3827篇 |
出版年
2023年 | 223篇 |
2022年 | 298篇 |
2021年 | 275篇 |
2020年 | 441篇 |
2019年 | 875篇 |
2018年 | 862篇 |
2017年 | 723篇 |
2016年 | 674篇 |
2015年 | 613篇 |
2014年 | 1002篇 |
2013年 | 2813篇 |
2012年 | 1273篇 |
2011年 | 2026篇 |
2010年 | 1901篇 |
2009年 | 2229篇 |
2008年 | 2385篇 |
2007年 | 2352篇 |
2006年 | 1838篇 |
2005年 | 1372篇 |
2004年 | 1269篇 |
2003年 | 1077篇 |
2002年 | 817篇 |
2001年 | 644篇 |
2000年 | 540篇 |
1999年 | 614篇 |
1998年 | 541篇 |
1997年 | 494篇 |
1996年 | 623篇 |
1995年 | 560篇 |
1994年 | 548篇 |
1993年 | 469篇 |
1992年 | 388篇 |
1991年 | 233篇 |
1990年 | 230篇 |
1989年 | 228篇 |
1988年 | 171篇 |
1987年 | 190篇 |
1986年 | 184篇 |
1985年 | 270篇 |
1984年 | 201篇 |
1983年 | 137篇 |
1982年 | 197篇 |
1981年 | 183篇 |
1980年 | 157篇 |
1979年 | 95篇 |
1978年 | 132篇 |
1977年 | 130篇 |
1976年 | 108篇 |
1975年 | 27篇 |
1974年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
12.
《Journal of separation science》2018,41(6):1319-1337
The present review discusses the theory and application of van't Hoff analysis in chiral chromatography, with main focus on liquid chromatography. The topics considered include the physical meaning of van't Hoff equation's parameters, interpretation of thermodynamic data in terms of retention and enantioseparation mechanisms, abnormal behavior of van't Hoff plots, and best practices to avoid biased results. 相似文献
13.
14.
Nonclassical light states are important for both conceptual and practical reasons: they are basic ingredients in testing and exploring quantum foundations, and are crucial resources in quantum technologies. Various useful criteria have been developed to detect nonclassicality in the literature, and several meaningful measures of nonclassicality have been introduced and measured experimentally. In this work, by use of a non-Hermitian generalization of the Wigner-Yanase-Dyson skew information and playing with operator ordering in evaluating average photon number, we develop a novel family of criteria for detecting nonclassicality of light based on Lieb's concavity, which is a deep and powerful result concerning interaction between quantum states and observables. We elucidate the information-theoretic as well as the physical meaning of the criteria, and illustrate their effectiveness in capturing and quantifying nonclassicality of various important light states. 相似文献
15.
This paper deals with the Cauchy–Dirichlet problem for the fractional Cahn–Hilliard equation. The main results consist of global (in time) existence of weak solutions, characterization of parabolic smoothing effects (implying under proper condition eventual boundedness of trajectories), and convergence of each solution to a (single) equilibrium. In particular, to prove the convergence result, a variant of the so-called ?ojasiewicz–Simon inequality is provided for the fractional Dirichlet Laplacian and (possibly) non-analytic (but ) nonlinearities. 相似文献
16.
It is believed that there are more fundamental gauge symmetries beyond those described by the Standard Model of particle physics. The scales of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose considering the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
in the space-based interferometer detectors. Our study demonstrates that the GW energy spectrum is reachable by the LISA, Tianqin, Taiji, BBO, and DECIGO experiments only for the case where the spontaneous breaking of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
is triggered by at least two electroweak singlet scalars. 相似文献
17.
We prove that to most of the known hypercyclic operators A on separable Banach spaces there exist compact (compact convex, compact connected) subsets K of E such that each compact (compact convex, compact connected) subset of E can be approximated with respect to Hausdorff's distance by for suitable .
Received July 8, 1997, in final form October 17, 1997 相似文献
18.
We investigate congruence classes and direct congruence classes of m-tuples in the complex projective space ℂP
n
. For direct congruence one allows only isometries which are induced by linear (instead of semilinear) mappings. We establish
a canonical bijection between the set of direct congruence classes of m-tuples of points in ℂP
n
and the set of equivalence classes of positive semidefinite Hermitean m×m-matrices of rank at most n+1 with 1's on the diagonal. As a corollary we get that the direct congruence class of an m-tuple is uniquely determined by the direct congruence classes of all of its triangles, provided that no pair of points of
the m-tuple has distance π/2. Examples show that the situation changes drastically if one replaces direct congruence classes by
congruence classes or if distances π/2 are allowed. Finally we do the same
kind of investigation also for the complex hyperbolic space ℂH
n
. Most of the results are completely analogous, however, there are also some interesting differences.
Received: 15 January 1996 相似文献
19.
Summary. We generalise and apply a refinement indicator of the type originally designed by Mackenzie, Süli and Warnecke in [15] and
[16] for linear Friedrichs systems to the Euler equations of inviscid, compressible fluid flow. The Euler equations are symmetrized
by means of entropy variables and locally linearized about a constant state to obtain a symmetric hyperbolic system to which
an a posteriori error analysis of the type introduced in [15] can be applied. We discuss the details of the implementation of the refinement
indicator into the DLR--Code which is based on a finite volume method of box type on an unstructured grid and present numerical results.
Received May 15, 1995 / Revised version received April 17, 1996 相似文献
20.
Andrea Blunck 《Monatshefte für Mathematik》1997,123(2):93-107
In this note we show that the chain space belonging to a quadric can be embedded into the chain geometry over a Clifford algebra via a generalized stereographic projection. 相似文献