全文获取类型
收费全文 | 6171篇 |
免费 | 127篇 |
国内免费 | 16篇 |
专业分类
化学 | 4478篇 |
晶体学 | 42篇 |
力学 | 78篇 |
数学 | 808篇 |
物理学 | 908篇 |
出版年
2020年 | 40篇 |
2019年 | 47篇 |
2017年 | 38篇 |
2016年 | 90篇 |
2015年 | 89篇 |
2014年 | 82篇 |
2013年 | 252篇 |
2012年 | 204篇 |
2011年 | 251篇 |
2010年 | 163篇 |
2009年 | 154篇 |
2008年 | 228篇 |
2007年 | 233篇 |
2006年 | 260篇 |
2005年 | 252篇 |
2004年 | 272篇 |
2003年 | 189篇 |
2002年 | 191篇 |
2001年 | 133篇 |
2000年 | 110篇 |
1999年 | 103篇 |
1998年 | 73篇 |
1997年 | 90篇 |
1996年 | 106篇 |
1995年 | 91篇 |
1994年 | 86篇 |
1993年 | 78篇 |
1992年 | 102篇 |
1991年 | 79篇 |
1990年 | 69篇 |
1989年 | 66篇 |
1988年 | 84篇 |
1987年 | 65篇 |
1986年 | 86篇 |
1985年 | 101篇 |
1984年 | 122篇 |
1983年 | 98篇 |
1982年 | 85篇 |
1981年 | 108篇 |
1980年 | 101篇 |
1979年 | 97篇 |
1978年 | 106篇 |
1977年 | 80篇 |
1976年 | 92篇 |
1975年 | 75篇 |
1974年 | 62篇 |
1973年 | 70篇 |
1972年 | 46篇 |
1971年 | 47篇 |
1970年 | 42篇 |
排序方式: 共有6314条查询结果,搜索用时 15 毫秒
1.
2.
3.
Bernard Chazelle Herbert Edelsbrunner Leonidas J. Guibas 《Discrete and Computational Geometry》1989,4(1):139-181
This paper investigates the combinatorial and computational aspects of certain extremal geometric problems in two and three dimensions. Specifically, we examine the problem of intersecting a convex subdivision with a line in order to maximize the number of intersections. A similar problem is to maximize the number of intersected facets in a cross-section of a three-dimensional convex polytope. Related problems concern maximum chains in certain families of posets defined over the regions of a convex subdivision. In most cases we are able to prove sharp bounds on the asymptotic behavior of the corresponding extremal functions. We also describe polynomial algorithms for all the problems discussed.Bernard Chazelle wishes to acknowledge the National Science Foundation for supporting this research in part under Grant No. MCS83-03925. Herbert Edelsbrunner is pleased to acknowledge the support of Amoco Fnd. Fac. Dev. Comput. Sci. 1-6-44862. 相似文献
4.
5.
We consider a spinning charge coupled to the Maxwell field. Through the appropriate symmetry in the initial conditions the charge remains at rest. We establish that any time-dependent finite energy solution converges to a sum of a soliton wave and an outgoing free wave. The convergence holds in global energy norm. Under a small constant external magnetic field the soliton manifold is stable in local energy seminorms and the evolution of the angular velocity is guided by an effective finite-dimensional dynamics. The proof uses a non-autonomous integral inequality method. 相似文献
6.
7.
8.
Given a1,a2,...,an ∈ ℤ^d$, we examine the set, G, of all non-negative integer combinations of these ai. In particular, we examine the generating function f(z) = ∑b ∈ Gzb. We prove that one can write this generating function as a rational function using the neighborhood complex (sometimes called
the complex of maximal lattice-free bodies or the Scarf complex) on a particular lattice in ℤn. In the generic case, this follows from algebraic results of Bayer and Sturmfels. Here we prove it geometrically in all
cases, and we examine a generalization involving the neighborhood complex on an arbitrary lattice. 相似文献
9.
A. Noda S. Nakamura Y. Iwashita S. Sakabe M. Hashida T. Shirai S. Shimizu H. Tongu H. Ito H. Souda A. Yamazaki M. Tanabe H. Daido M. Mori M. Kado A. Sagisaka K. Ogura M. Nishiuchi S. Orimo Y. Hayashi A. Yogo S. Bulanov T. Esirkepov A. Nagashima T. Kimura T. Tajima T. Takeuchi K. Matsukado A. Fukumi Z. Li 《Laser Physics》2006,16(4):647-653
In order to widely spread out particle beams utilized in cancer therapy, laser-produced ions are developed as the injection beam for an ion synchrotron dedicated for cancer therapy. Such a laser ion source is expected to contribute largely to the realization of compactness of the size and low cost of the cancer therapy accelerator. The energy spectrum of the laser-produced ions, however, has no peak, but their intensities decrease exponentially according to the increase of the energy. For the purpose of modifying such a situation, we have proposed a scheme to rotate the beam in the longitudinal phase space with the use of the RF electric field, which is phase-adjusted with the pulse laser. We aim for a reduction of the energy spread of ± 5% selected by an energy analyzer and slits to ±1% by such phase rotation. For this purpose, a quarter wavelength resonator with two gaps with the same resonant frequency as the source laser has already been fabricated, together with its RF power source. The above phase rotation system and its recent experimental realization are presented. 相似文献
10.
方永得 张玉虎 M.Oshima Y.Toh 周小红 M.Koizumi A.Osa A.Kimura Y.Hatsukawa T.Morikawa M.Nakamura M.Sugawara H.Kusakari 《中国物理 C》2006,30(2):99-104
利用在束γ谱学实验技术, 通过173Yb(19F,4nγ)反应
布居了188Au的高自旋态, 并对其准粒子带结构进行了研究. 基于实验测量结果, 对原有的双奇核188Au能级纲图做了较大的修改. 通过系统性比较, 对15+以上的能级结构进行了讨论. 相似文献