全文获取类型
收费全文 | 77844篇 |
免费 | 339篇 |
国内免费 | 374篇 |
专业分类
化学 | 24093篇 |
晶体学 | 787篇 |
力学 | 6721篇 |
数学 | 31948篇 |
物理学 | 15008篇 |
出版年
2021年 | 25篇 |
2018年 | 10436篇 |
2017年 | 10262篇 |
2016年 | 6068篇 |
2015年 | 847篇 |
2014年 | 299篇 |
2013年 | 308篇 |
2012年 | 3768篇 |
2011年 | 10488篇 |
2010年 | 5622篇 |
2009年 | 6031篇 |
2008年 | 6576篇 |
2007年 | 8741篇 |
2006年 | 212篇 |
2005年 | 1289篇 |
2004年 | 1513篇 |
2003年 | 1955篇 |
2002年 | 1000篇 |
2001年 | 239篇 |
2000年 | 284篇 |
1999年 | 149篇 |
1998年 | 188篇 |
1997年 | 142篇 |
1996年 | 194篇 |
1995年 | 114篇 |
1994年 | 74篇 |
1993年 | 92篇 |
1992年 | 52篇 |
1991年 | 62篇 |
1990年 | 49篇 |
1989年 | 58篇 |
1988年 | 58篇 |
1987年 | 57篇 |
1986年 | 57篇 |
1985年 | 46篇 |
1984年 | 42篇 |
1983年 | 36篇 |
1982年 | 41篇 |
1981年 | 38篇 |
1980年 | 46篇 |
1979年 | 44篇 |
1978年 | 34篇 |
1973年 | 25篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
1907年 | 32篇 |
1904年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Karlheinz Gröchenig 《Journal of Fourier Analysis and Applications》2014,20(4):865-895
This is a survey about the theory of Gabor frames. We review the structural results about Gabor frames over a lattice and then discuss the few known results about the fine structure of Gabor frames. We add a new result about the relation between properties of the window and properties of the frame set and conclude with a vision of how a more complete theory of the fine structure might look like. 相似文献
992.
993.
994.
995.
We prove a version of a small index property theorem for strong amalgamation classes. Our result builds on an earlier theorem by Lascar and Shelah (in their case, for saturated models of uncountable first-order theories). We then study versions of the small index property for various non-elementary classes. In particular, we obtain the small index property for quasiminimal pregeometry structures. 相似文献
996.
997.
This paper focuses on a machine scheduling problem having applications in truck scheduling at transshipment terminals. Jobs increase and decrease, respectively, the level of a central inventory. Naturally, jobs decreasing the inventory level can be processed only if the level of the inventory is high enough not to drop below zero. We consider the problem to find a schedule for jobs such that the maximum lateness among all jobs is minimized. We develop properties of optimal solutions, lower bounds, and heuristic methods in order to find upper bounds. These are incorporated in four branch and bound algorithms that are based on fixing sequences of jobs in forward or backward direction in two different types of representations. By means of a computational study, we compare these approaches with each other in order to show their efficiency. 相似文献
998.
M Gallego M Laguna R Martí A Duarte 《The Journal of the Operational Research Society》2013,64(5):724-734
We propose new heuristic procedures for the maximally diverse grouping problem (MDGP). This NP-hard problem consists of forming maximally diverse groups—of equal or different size—from a given set of elements. The most general formulation, which we address, allows for the size of each group to fall within specified limits. The MDGP has applications in academics, such as creating diverse teams of students, or in training settings where it may be desired to create groups that are as diverse as possible. Search mechanisms, based on the tabu search methodology, are developed for the MDGP, including a strategic oscillation that enables search paths to cross a feasibility boundary. We evaluate construction and improvement mechanisms to configure a solution procedure that is then compared to state-of-the-art solvers for the MDGP. Extensive computational experiments with medium and large instances show the advantages of a solution method that includes strategic oscillation. 相似文献
999.
1000.
We develop the wave-optics approach for calculating the diffraction distribution of gradient refractiveindex lenses and observing the diffraction pattern of gradient refractive-index lenses in the experiments. The results of our calculation are in good agreement with the experimental results obtained. We show that the diffraction can be regarded as a method to check the quality of the refractive-index distributions of gradient refractive-index lenses. 相似文献