全文获取类型
收费全文 | 147514篇 |
免费 | 13107篇 |
国内免费 | 7627篇 |
专业分类
化学 | 73080篇 |
晶体学 | 1385篇 |
力学 | 11033篇 |
综合类 | 310篇 |
数学 | 39413篇 |
物理学 | 43027篇 |
出版年
2024年 | 279篇 |
2023年 | 1601篇 |
2022年 | 2716篇 |
2021年 | 2834篇 |
2020年 | 3105篇 |
2019年 | 2907篇 |
2018年 | 12306篇 |
2017年 | 11953篇 |
2016年 | 9237篇 |
2015年 | 4271篇 |
2014年 | 4409篇 |
2013年 | 5592篇 |
2012年 | 10302篇 |
2011年 | 16734篇 |
2010年 | 9857篇 |
2009年 | 9982篇 |
2008年 | 10887篇 |
2007年 | 12546篇 |
2006年 | 3950篇 |
2005年 | 4386篇 |
2004年 | 3887篇 |
2003年 | 3819篇 |
2002年 | 2719篇 |
2001年 | 1705篇 |
2000年 | 1641篇 |
1999年 | 1681篇 |
1998年 | 1490篇 |
1997年 | 1432篇 |
1996年 | 1483篇 |
1995年 | 1164篇 |
1994年 | 994篇 |
1993年 | 855篇 |
1992年 | 726篇 |
1991年 | 641篇 |
1990年 | 550篇 |
1989年 | 442篇 |
1988年 | 393篇 |
1987年 | 331篇 |
1986年 | 306篇 |
1985年 | 250篇 |
1984年 | 185篇 |
1983年 | 138篇 |
1982年 | 121篇 |
1981年 | 105篇 |
1980年 | 111篇 |
1979年 | 77篇 |
1978年 | 64篇 |
1977年 | 58篇 |
1976年 | 46篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
This paper considers a receiver set partitioning and sequencing problem in a wavelength division multiplexing single-hop lightwave network for multicasting traffic. The problem is analysed in the approach of uncapacitated single batch-processing machine scheduling. In the analysis, several solution properties are characterized with respect to a mean flow time measure, based upon which two heuristic algorithms are developed, along with a dynamic programming algorithm. Several numerical experiments show that the heuristic algorithms generate good schedules. The problem is extended to consider two measures simultaneously including the mean flow time and the number of transmissions, for which the proposed algorithms also perform well. 相似文献
122.
Pengbo Jiang Tiexin Cheng Yan Liu Xianghao Cui Yingli Bi Kaiji Zhen 《Reaction Kinetics and Catalysis Letters》2004,82(1):49-56
The novel phase transfer catalysts S-8 [4-(dimethyloctylammonium) propansultan] and DB-X [1,4-bis(triethylmethylammonium)benzene dibromide] were synthesized and employed for high conversion synthesis of dichlorocyclopropane from various olefins.This revised version was published online in December 2005 with corrections to the Cover Date. 相似文献
123.
稀疏过程在破产问题中的应用 总被引:5,自引:0,他引:5
本讨论一类人寿保险的风险过程,其中保单到达服从齐次Poisson过程。而描述退保及索赔发生的计数过程分别为这一过程的q-稀疏与p-稀疏.对此模型给出其破产概率的具体上界,并与其它一类风险模型进行比较. 相似文献
124.
Jiří Herec 《Czechoslovak Journal of Physics》2004,54(12):1473-1481
In this paper the quantum-statistical properties of light beams propagating in a directional nonlinear coupler are investigated.
This device is composed of a pair of linearly coupled nonlinear waveguides operating by means of degenerate parametric downconversion.
The possibility of generation of nonclassical states of light in single and compound modes, using the short-length approximation,
is discussed. Influence of linear and nonlinear mismatches for generation of nonclassical light is taken into account.
This work was supported by Project LN00A015, Research Project No. CEZ: J14/98 and the COST project OC P11.003 of the Czech
Ministry of Education. 相似文献
125.
C Guéret N Jussien O Lhomme C Pavageau C Prins 《The Journal of the Operational Research Society》2003,54(5):458-465
In this paper, we describe an aircraft loading problem submitted by the French military agency (DGA) as part of a more general military airlift planning problem. It can be viewed as a kind of bi-dimensional bin-packing problem, with heterogeneous bins and several additional constraints. We introduce two-phase methods for solving this NP-hard problem. The first phase consists in building good initial solutions, thanks to two fast algorithms: a list-based heuristic and a loading pattern generation method. Both algorithms call a constraint-based subroutine, able to determine quickly if the items already loaded can be reshuffled to accommodate a new object. The second phase improves these preliminary solutions using local search techniques. Results obtained on real data sets are presented. 相似文献
126.
YaoKui ChenZhixiang 《分析论及其应用》2003,19(2):115-120
This paper gives the weighted Lp convergence rate estimations of the Gruenwald interpolatory polynomials based on the zeros of Chebyshev polymomials of the first kind,and proves that the order of the estimations is optimal for p≥1. 相似文献
127.
The title compound, [Cd(SeCN)2(pyCN)2]∞, adopts an extended one‐dimensional chain structure in which the neighboring cadmium atoms are bridged by two selenocyanate ions. The central cadmium atom has a distorted octahedral geometry defined by two isonicotinonitrile and four selenocyanate ions in a 4N2Se fashion. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
128.
129.
In mononuclear HgI2[(C5H4N)3N], mercury is tetrahedrally coordinated by two nitrogen atoms of a tris(2‐pyridyl)amine ligand and two iodides. The coordination moieties are connected by weak intermolecular Hg(II)···I interactions to give a one‐dimensional structure. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
130.