全文获取类型
收费全文 | 95155篇 |
免费 | 3608篇 |
国内免费 | 2048篇 |
专业分类
化学 | 36393篇 |
晶体学 | 950篇 |
力学 | 7652篇 |
综合类 | 67篇 |
数学 | 33772篇 |
物理学 | 21977篇 |
出版年
2023年 | 391篇 |
2022年 | 556篇 |
2021年 | 671篇 |
2020年 | 731篇 |
2019年 | 735篇 |
2018年 | 10956篇 |
2017年 | 10663篇 |
2016年 | 6899篇 |
2015年 | 1634篇 |
2014年 | 1322篇 |
2013年 | 1669篇 |
2012年 | 5414篇 |
2011年 | 12104篇 |
2010年 | 6708篇 |
2009年 | 7032篇 |
2008年 | 7688篇 |
2007年 | 9698篇 |
2006年 | 1186篇 |
2005年 | 2063篇 |
2004年 | 2098篇 |
2003年 | 2366篇 |
2002年 | 1426篇 |
2001年 | 572篇 |
2000年 | 557篇 |
1999年 | 538篇 |
1998年 | 464篇 |
1997年 | 434篇 |
1996年 | 478篇 |
1995年 | 359篇 |
1994年 | 283篇 |
1993年 | 307篇 |
1992年 | 195篇 |
1991年 | 221篇 |
1990年 | 178篇 |
1989年 | 157篇 |
1988年 | 146篇 |
1987年 | 128篇 |
1986年 | 125篇 |
1985年 | 100篇 |
1984年 | 99篇 |
1983年 | 66篇 |
1982年 | 73篇 |
1981年 | 61篇 |
1980年 | 72篇 |
1979年 | 54篇 |
1978年 | 47篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
A new method is introduced to generate a elliptical hollow beam inside a cavity. Using a matrix eigenvalue method, the laser resonator with optical diffraction elements is theoretically analyzed and simulated. A elliptical hollow beam of good quality is realized experimentally. The interaction between linearly polarized elliptical hollow beam and a two-level atom is investigated theoretically. Although the linearly polarized elliptical hollow beam does not carry angular momentum, it can produce very high torque. The atoms initially at rest and located at off-beam- axis positions will rotate under the drive of the torque of the beam. The atomic motion trajectory in the field of elliptical hollow beam has been demonstrated. The study shows that the elliptical hollow beam might be a useful tool in the study of vortex property of Bose-Einstein condensate or ultra cold atom media. 相似文献
52.
53.
Dual fractional cutting plane algorithms, in which cutting planes are used to iteratively tighten a linear relaxation of an integer program,
are well-known and form the basis of the highly successful branch-and-cut method. It is rather less well-known that various primal cutting plane algorithms were developed in the 1960s, for example by Young. In a primal algorithm, the main role of the cutting
planes is to enable a feasible solution to the original problem to be improved. Research on these algorithms has been almost
non-existent.
In this paper we argue for a re-examination of these primal methods. We describe a new primal algorithm for pure 0-1 problems based on strong valid inequalities and give some encouraging computational results. Possible extensions to the case of general
mixed-integer programs are also discussed. 相似文献
54.
Yasuyuki Kawahigashi 《Communications in Mathematical Physics》2002,226(2):269-287
We study the recent construction of subfactors by Rehren which generalizes the Longo–Rehren subfactors. We prove that if
we apply this construction to a non-degenerately braided subfactor N⊂M and α±-induction, then the resulting subfactor is dual to the Longo–Rehren subfactor M⊗M
opp⊂R arising from the entire system of irreducible endomorphisms of M resulting from αplusmn;-induction. As a corollary, we solve a problem on existence of braiding raised by Rehren negatively. Furthermore, we generalize
our previous study with Longo and Müger on multi-interval subfactors arising from a completely rational conformal net of factors
on S
1 to a net of subfactors and show that the (generalized) Longo–Rehren subfactors and α-induction naturally appear in this context.
Received: 11 September 2001 / Accepted: 7 October 2001 相似文献
55.
Julio Castellanos 《Mathematische Zeitschrift》2002,239(4):777-802
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions
greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type
of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples
are presented.
Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002 相似文献
56.
57.
58.
给出了线和n-2的n阶(0,1)-矩阵的最大积和式的积分表达式,并证明了该积分表达式与[1]得到的组合表达式等价。 相似文献
59.
Alexander Krasnosel'skii Dmitrii Rachinskii 《NoDEA : Nonlinear Differential Equations and Applications》2002,9(1):93-115
We consider autonomous systems with a nonlinear part depending on a parameter and study Hopf bifurcations at infinity. The
nonlinear part consists of the nonlinear functional term and the Prandtl--Ishlinskii hysteresis term. The linear part of the
system has a special form such that the close-loop system can be considered as a hysteresis perturbation of a quasilinear
Hamiltonian system. The Hamiltonian system has a continuum of arbitrarily large cycles for each value of the parameter. We
present sufficient conditions for the existence of bifurcation points for the non-Hamiltonian system with hysteresis. These
bifurcation points are determined by simple characteristics of the hysteresis nonlinearity. 相似文献
60.
According to an induced-matter approach, Liu and Wesson obtained the rest mass of a typical particle from the reduction of a 5D Klein–Gordon equation to a 4D one. Introducing an extra-dimension momentum operator identified with the rest mass eigenvalue operator, we consider a way to generalize the 4D Dirac equation to 5D. An analogous normal Dirac equation is gained when the generalization reduces to 4D. We find the rest mass of a particle in curved space varies with spacetime coordinates and check this for the case of exact solitonic and cosmological solution of the 5D vacuum gravitational field equations. 相似文献