全文获取类型
收费全文 | 5785篇 |
免费 | 251篇 |
国内免费 | 32篇 |
专业分类
化学 | 3600篇 |
晶体学 | 23篇 |
力学 | 199篇 |
数学 | 1208篇 |
物理学 | 1038篇 |
出版年
2023年 | 54篇 |
2022年 | 77篇 |
2021年 | 182篇 |
2020年 | 156篇 |
2019年 | 154篇 |
2018年 | 130篇 |
2017年 | 117篇 |
2016年 | 243篇 |
2015年 | 229篇 |
2014年 | 241篇 |
2013年 | 335篇 |
2012年 | 412篇 |
2011年 | 465篇 |
2010年 | 273篇 |
2009年 | 250篇 |
2008年 | 373篇 |
2007年 | 340篇 |
2006年 | 309篇 |
2005年 | 296篇 |
2004年 | 232篇 |
2003年 | 181篇 |
2002年 | 191篇 |
2001年 | 70篇 |
2000年 | 46篇 |
1999年 | 63篇 |
1998年 | 51篇 |
1997年 | 64篇 |
1996年 | 48篇 |
1995年 | 47篇 |
1994年 | 45篇 |
1993年 | 33篇 |
1992年 | 25篇 |
1991年 | 28篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 22篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 7篇 |
1972年 | 5篇 |
排序方式: 共有6068条查询结果,搜索用时 62 毫秒
21.
Marco Andreatta Elena Chierici Gianluca Occhetta 《Central European Journal of Mathematics》2004,2(2):272-293
Let X be a Fano variety of dimension n, pseudoindex i
X
and Picard number ρX. A generalization of a conjecture of Mukai says that ρX(i
X
−1)≤n. We prove that the conjecture holds for a variety X of pseudoindex i
X
≥n+3/3 if X admits an unsplit covering family of rational curves; we also prove that this condition is satisfied if ρX> and either X has a fiber type extremal contraction or has not small extremal contractions. Finally we prove that the conjecture holds
if X has dimension five. 相似文献
22.
Andrea Grosso Marco Locatelli Fabio Schoen 《Computational Optimization and Applications》2007,38(3):351-370
In this paper we perform a computational analysis of a population based approach for global optimization, Population Basin
Hopping (PBH), which was proven to be very efficient on very challenging global optimization problems by the authors (see
). The experimental analysis aims at understanding more deeply how the approach works and why it is successful on challenging
problems. 相似文献
23.
A time-dependent model corresponding to an Oldroyd-B viscoelastic fluid is considered, the convective terms being disregarded.
Global existence in time is proved in Banach spaces provided the data are small enough, using the implicit function theorem
and a maximum regularity property for a three fields Stokes problem. A finite element discretization in space is then proposed.
Existence of the numerical solution is proved for small data, so as a priori error estimates, using again an implicit function
theorem.
Supported by the Swiss National Science Foundation. Fellowship PBEL2–114311. 相似文献
24.
Some authors claim that reporting the best result obtained by a stochastic algorithm in a number of runs is more meaningful
than reporting some central statistic. In this short note, we analyze and refute the main argument brought in favor of this
statement. 相似文献
25.
Marco Marletta 《Advances in Computational Mathematics》1994,2(2):155-184
This paper discusses the numerical solution of eigenvalue problems for Hamiltonian systems of ordinary differential equations.
Two new codes are presented which incorporate the algorithms described here; to the best of the author’s knowledge, these
are the first codes capable of solving numerically such general eigenvalue problems. One of these implements a new new method
of solving a differential equation whose solution is a unitary matrix. Both codes are fully documented and are written inPfort-verifiedFortran 77, and will be available in netlib/aicm/sl11f and netlib/aicm/sl12f. 相似文献
26.
27.
Marco Merkli 《Journal of Mathematical Analysis and Applications》2007,327(1):376-399
Level shift operators describe the second-order displacement of eigenvalues under perturbation. They play a central role in resonance theory and ergodic theory of open quantum systems at positive temperatures. We exhibit intrinsic properties of level shift operators, properties which stem from the structure of open quantum systems at positive temperatures and which are common to all such systems. They determine the geometry of resonances bifurcating from eigenvalues of positive temperature Hamiltonians and they relate the Gibbs state, the kernel of level shift operators, and zero energy resonances. We show that degeneracy of energy levels of the small part of the open quantum system causes the Fermi Golden Rule Condition to be violated and we analyze ergodic properties of such systems. 相似文献
28.
We study the asymptotic behaviour of non-negative solutions of Yamabe type equations on a complete Riemannian manifold. Then we provide a comparison result, based on a form of the weak maximum principle at infinity, which together with the “a priori” estimates previously obtained, yields uniqueness under very general Ricci assumptions. The paper ends with an existence result and an application to the non-compact Yamabe problem. 相似文献
29.
The differential systems satisfied by orthogonal polynomials with arbitrary semiclassical measures supported on contours in
the complex plane are derived, as well as the compatible systems of deformation equations obtained from varying such measures.
These are shown to preserve the generalized monodromy of the associated rank-2 rational covariant derivative operators. The
corresponding matrix models, consisting of unitarily diagonalizable matrices with spectra supported on these contours are
analyzed, and it is shown that all coefficients of the associated spectral curves are given by logarithmic derivatives of
the partition function or, more generally, the gap probabilities. The associated isomonodromic tau functions are shown to
coincide, within an explicitly computed factor, with these partition functions.
Research supported in part by the Natural Sciences and Engineering Research Council of Canada, the Fonds FCAR du Québec and
EC ITH Network HPRN-CT-1999-000161. 相似文献
30.
Slug velocity profiles in horizontal gas–liquid flow 总被引:1,自引:0,他引:1
V. Bertola 《Experiments in fluids》2002,32(6):722-727