全文获取类型
收费全文 | 6052篇 |
免费 | 590篇 |
国内免费 | 485篇 |
专业分类
化学 | 952篇 |
晶体学 | 22篇 |
力学 | 460篇 |
综合类 | 160篇 |
数学 | 3650篇 |
物理学 | 1883篇 |
出版年
2024年 | 5篇 |
2023年 | 72篇 |
2022年 | 105篇 |
2021年 | 135篇 |
2020年 | 161篇 |
2019年 | 176篇 |
2018年 | 156篇 |
2017年 | 226篇 |
2016年 | 236篇 |
2015年 | 144篇 |
2014年 | 341篇 |
2013年 | 444篇 |
2012年 | 351篇 |
2011年 | 314篇 |
2010年 | 295篇 |
2009年 | 406篇 |
2008年 | 407篇 |
2007年 | 375篇 |
2006年 | 324篇 |
2005年 | 288篇 |
2004年 | 263篇 |
2003年 | 241篇 |
2002年 | 234篇 |
2001年 | 193篇 |
2000年 | 161篇 |
1999年 | 163篇 |
1998年 | 133篇 |
1997年 | 121篇 |
1996年 | 104篇 |
1995年 | 71篇 |
1994年 | 73篇 |
1993年 | 53篇 |
1992年 | 35篇 |
1991年 | 41篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 27篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1936年 | 3篇 |
排序方式: 共有7127条查询结果,搜索用时 687 毫秒
61.
Mark A. S. Aarons 《Calculus of Variations and Partial Differential Equations》2006,25(2):205-246
We study the forced mean curvature flow of graphs in Minkowski space and prove longtime existence of solutions. When the forcing
term is a constant, we prove convergence to either a constant mean curvature hypersurface or a translating soliton – depending
on the boundary conditions at infinity.
It is a pleasure to thank my PhD advisors Klaus Ecker and Gerhard Huisken for their assistance and encouragement. I also thank
Maria Athanassenas, Oliver Schnürrer and Marty Ross for their interest and useful comments, and the Max Planck Gesellschaft
for financial support. 相似文献
62.
Valuations of dense near polygons were introduced in 16 . In the present paper, we classify all valuations of the near hexagons ??1 and ??2, which are related to the respective Witt designs S(5,6,12) and S(5,8,24). Using these classifications, we prove that if a dense near polygon S contains a hex H isomorphic to ??1 or ??2, then H is classical in S. We will use this result to determine all dense near octagons that contain a hex isomorphic to ??1 or ??2. As a by‐product, we obtain a purely geometrical proof for the nonexistence of regular near 2d‐gons, d ≥ 4, whose parameters s, t, ti (0 ≤ i ≤ d) satisfy (s, t2, t3) = (2, 1, 11) or (2, 2, 14). The nonexistence of these regular near polygons can also be shown with the aid of eigenvalue techniques. © 2005 Wiley Periodicals, Inc. J Combin Designs 14: 214–228, 2006 相似文献
63.
64.
CRT显示器稳定性实验研究 总被引:4,自引:1,他引:3
用屏幕色度计对一台SONY-G520显示器的显色特性进行了测量,研究了其开机稳定性和短、中、长期内的色差及色度偏差。实验结果表明,开机后,显示器的亮度Y和色度x,y分别可在2h,30min和1h达到相对稳定状态,且在达到相对稳定后,在短、中、长期内的平均色差分别为0.0611,0.1469和1.2536CIELAB色差单位;在中期内,Y,x,y,L,a,b的平均偏差分别为0.0663,0.0008,0.0015,0.0695,0.4740和0.1766。通过对显示器稳定性的测量,为在对比度敏感测量和色貌模型、图像质量、图像感知模型评价等研究领域中用显示器进行实验研究奠定了基础。 相似文献
65.
J. Freudenberger 《Discrete Applied Mathematics》2006,154(2):294-304
We consider bounded distance list decoding, such that the decoder calculates the list of all codewords within a sphere around the received vector. We analyze the performance and the complexity of this suboptimum list decoding scheme for the binary symmetric channel. The reliability function of the list decoding scheme is equivalent to the sphere-packing bound, where the decoding complexity is asymptotically bounded by 2nR(1-R). Furthermore, we investigate a decision feedback strategy that is based on bounded distance list decoding. Here, any output with zero or many codewords will call for a repeated transmission. In this case the decoding complexity will be of the order 2nR(1-C), where C denotes the channel capacity. The reliability function is close to Forney's feedback exponent. 相似文献
66.
Andreas Spillner 《Mathematical Logic Quarterly》2006,52(1):29-36
We study the problem of tiling a polyomino P with as few squares as possible such that every square in the tiling has a non‐empty intersection with the boundary of P . Our main result is an algorithm which given a simply connected polyomino P computes such a tiling of P . We indicate how one can improve the running time of this algorithm for the more restricted row‐column‐convex polyominoes. Finally we show that a related decision problem is in NP for rectangular polyominoes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
67.
We generalize a variational principle for the mean spherical approximation for a system of charged hard spheres in 3D to arbitrary
dimensions. We first construct a free energy variational trial function from the Debye-Hückel excess charging internal energy
at a finite concentration and an entropy obtained at the zero-concentration limit by thermodynamic integration. In three dimensions
the minimization of this expression with respect to the screening parameter leads to the mean spherical approximation, usually
obtained by solution of the Ornstein-Zernike equation. This procedure, which interpolates naturally between the zero concentration/coupling
limit and the high-concentration/ coupling limit, is extended to arbitrary dimensions. We conjecture that this result is also
equivalent to the MSA as originally defined, although a technical proof of this point is left for the future. The Onsager
limitT ΔS
MSA
/ΔE
MSA
→ 0 for infinite concentration/coupling is satisfied for all d ≠ 2, while ford=2 this limit is 1.
On leave from Department of Physics, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico, 00681. 相似文献
68.
Two extensions of the univariate Gini index are considered:RD, based on expected distance between two independent vectors from the same distribution with finite meanμ
d; andRV, related to the expected volume of the simplex formed fromd+1 independent such vectors. A new characterization ofRDas proportional to a univariate Gini index for a particular linear combination of attributes relates it to the Lorenz zonoid. TheLorenz zonoidwas suggested as a multivariate generalization of the Lorenz curve.RVis, up to scaling, the volume of the Lorenz zonoid plus a unit cube of full dimension. Whend=1, bothRDandRVequal twice the area between the usual Lorenz curve and the line of zero disparity. Whend>1, they are different, but inherit properties of the univariate Gini index and are related via the Lorenz zonoid:RDis proportional to the average of the areas of some two-dimensioned projections of the lift zonoid, whileRVis the average of the volumes of projections of the Lorenz zonoid over all coordinate subspaces. 相似文献
69.
利用可积系统的思想,借助三维Minkowski空间L3的矩阵模型,研究了L3中具有调和逆平均曲率的类空曲面和洛伦兹调和逆平均曲率类时曲面的可积性及其形变. 相似文献
70.