全文获取类型
收费全文 | 405565篇 |
免费 | 8059篇 |
国内免费 | 3828篇 |
专业分类
化学 | 206401篇 |
晶体学 | 5312篇 |
力学 | 20787篇 |
综合类 | 203篇 |
数学 | 68465篇 |
物理学 | 116284篇 |
出版年
2021年 | 2467篇 |
2020年 | 2798篇 |
2019年 | 2737篇 |
2018年 | 12523篇 |
2017年 | 12210篇 |
2016年 | 10492篇 |
2015年 | 5015篇 |
2014年 | 5804篇 |
2013年 | 15690篇 |
2012年 | 15908篇 |
2011年 | 24886篇 |
2010年 | 14648篇 |
2009年 | 14918篇 |
2008年 | 19532篇 |
2007年 | 21680篇 |
2006年 | 13396篇 |
2005年 | 13193篇 |
2004年 | 12193篇 |
2003年 | 11252篇 |
2002年 | 10123篇 |
2001年 | 10736篇 |
2000年 | 8362篇 |
1999年 | 6618篇 |
1998年 | 5392篇 |
1997年 | 5142篇 |
1996年 | 5271篇 |
1995年 | 4783篇 |
1994年 | 4475篇 |
1993年 | 4252篇 |
1992年 | 4720篇 |
1991年 | 4552篇 |
1990年 | 4232篇 |
1989年 | 4030篇 |
1988年 | 4266篇 |
1987年 | 3925篇 |
1986年 | 3805篇 |
1985年 | 5436篇 |
1984年 | 5473篇 |
1983年 | 4452篇 |
1982年 | 4824篇 |
1981年 | 4849篇 |
1980年 | 4604篇 |
1979年 | 4712篇 |
1978年 | 4701篇 |
1977年 | 4667篇 |
1976年 | 4613篇 |
1975年 | 4527篇 |
1974年 | 4367篇 |
1973年 | 4550篇 |
1972年 | 2584篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
Eiji Yanagida 《Journal of Dynamics and Differential Equations》2007,19(4):895-914
This paper is concerned with the irregular behavior of solutions for Fisher’s equation when initial data do not decay in a
regular way at the spatial infinity. In the one-dimensional case, we show the existence of a solution whose profile and average
speed are not convergent. In the higher-dimensional case, we show the existence of expanding fronts with arbitrarily prescribed
profiles. We also show the existence of irregularly expanding fronts whose profile varies in time. Proofs are based on some
estimate of the difference of two distinct solutions and a comparison technique.
Dedicated to Professor Pavol Brunovsky on his 70th birthday. 相似文献
902.
Lubomír Kubáček 《Mathematica Slovaca》2007,57(6):571-588
The multivariate model, where not only parameters of the mean value of the observation matrix, but also some other parameters
occur in constraints, is considered in the paper. Some basic inference is presented under the condition that the covariance
matrix is either unknown, or partially unknown, or known.
Supported by the grant of the Council of Czech Republic MSM 6 198 959 214. 相似文献
903.
Adam B. Levy 《Mathematical Programming》2007,110(3):615-639
Numerical methods for solving constrained optimization problems need to incorporate the constraints in a manner that satisfies
essentially competing interests; the incorporation needs to be simple enough that the solution method is tractable, yet complex
enough to ensure the validity of the ultimate solution. We introduce a framework for constraint incorporation that identifies
a minimal acceptable level of complexity and defines two basic types of constraint incorporation which (with combinations)
cover nearly all popular numerical methods for constrained optimization, including trust region methods, penalty methods,
barrier methods, penalty-multiplier methods, and sequential quadratic programming methods. The broad application of our framework
relies on addition and chain rules for constraint incorporation which we develop here. 相似文献
904.
We prove that a locally compact ANR-space X is a Q-manifold if and only if it has the Disjoint Disk Property (DDP), all points of X are homological Z
∞-points and X has the countable-dimensional approximation property (cd-AP), which means that each map f: K → X of a compact polyhedron can be approximated by a map with the countable-dimensional image. As an application we prove that
a space X with DDP and cd-AP is a Q-manifold if some finite power of X is a Q-manifold. If some finite power of a space X with cd-AP is a Q-manifold, then X
2 and X × [0, 1] are Q-manifolds as well. We construct a countable family χ of spaces with DDP and cd-AP such that no space X ∈ χ is homeomorphic to the Hilbert cube Q whereas the product X × Y of any different spaces X, Y ∈ χ is homeomorphic to Q. We also show that no uncountable family χ with such properties exists.
This work was supported by the Slovenian-Ukrainian (Grant No. SLO-UKR 04-06/07) 相似文献
905.
Sylvain Maillot 《Geometric And Functional Analysis》2007,17(3):839-851
We show that open 3-manifolds that have a locally finite decomposition along 2-spheres are characterized by the existence
of a Riemannian metric with respect to which the second homotopy group of the manifold is generated by small elements.
Received: November 2005 Revision: February 2006 Accepted: May 2006 相似文献
906.
Michèle Audin 《manuscripta mathematica》2007,124(4):533-550
In this paper, we investigate symplectic manifolds endowed with a Morse–Bott function with only two critical submanifolds,
one of which is Lagrangian while the other one is symplectic. 相似文献
907.
For a general K3 surface S of genus g, with 2 ≤ g ≤ 10, we prove that the intermediate Jacobians of the family of prime Fano threefolds of genus g containing S as a hyperplane section, form generically an algebraic completely integrable Hamiltonian system.
The first author is partially supported by grant MI1503/2005 of the Bulgarian Foundation for Scientific Research. 相似文献
908.
In this paper, we establish a theorem on the distribution of primes in quadratic progressions on average. 相似文献
909.
910.
A model proposed in the literature for fish schools of relatively large size is studied for mathematical and qualitative properties. Existence, uniqueness and positivity of solutions are established and bifurcation properties relative to diffusion and alignment parameters are studied. 相似文献