全文获取类型
收费全文 | 7107篇 |
免费 | 860篇 |
国内免费 | 587篇 |
专业分类
化学 | 3420篇 |
晶体学 | 39篇 |
力学 | 148篇 |
综合类 | 118篇 |
数学 | 3930篇 |
物理学 | 899篇 |
出版年
2024年 | 8篇 |
2023年 | 36篇 |
2022年 | 145篇 |
2021年 | 196篇 |
2020年 | 182篇 |
2019年 | 219篇 |
2018年 | 162篇 |
2017年 | 269篇 |
2016年 | 303篇 |
2015年 | 248篇 |
2014年 | 416篇 |
2013年 | 601篇 |
2012年 | 455篇 |
2011年 | 455篇 |
2010年 | 452篇 |
2009年 | 492篇 |
2008年 | 536篇 |
2007年 | 546篇 |
2006年 | 374篇 |
2005年 | 345篇 |
2004年 | 230篇 |
2003年 | 238篇 |
2002年 | 197篇 |
2001年 | 223篇 |
2000年 | 176篇 |
1999年 | 156篇 |
1998年 | 117篇 |
1997年 | 105篇 |
1996年 | 95篇 |
1995年 | 94篇 |
1994年 | 69篇 |
1993年 | 73篇 |
1992年 | 70篇 |
1991年 | 48篇 |
1990年 | 20篇 |
1989年 | 26篇 |
1988年 | 35篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 31篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1975年 | 2篇 |
1973年 | 6篇 |
1972年 | 2篇 |
排序方式: 共有8554条查询结果,搜索用时 46 毫秒
31.
D. Baleanu 《Czechoslovak Journal of Physics》2003,53(11):971-976
The variational formulation of the Schrödinger field was investigated and the applicability of the chain method was analyzed. Using Batalin-Fradkin-Tyutin formalism a gauge invariant theory was constructed. 相似文献
32.
Xuyuan GuScott Cowell Jinfa YingXuejun Tang Victor J. Hruby 《Tetrahedron letters》2003,44(31):5863-5866
(2S,3S)- and (2R,3R)-2-amino-3-phenyl-5-hexenoic acids have been synthesized in large scale by using Ni(II)-complexes as a template. The amino acids were used in the synthesis of [4,3,0]-bicyclic β-turn mimetics by a convergent methodology. The unique advantage of this strategy is the convenience of introducing side chain groups with predetermined chiralities on both the five- and six-membered heterocyclic rings. 相似文献
33.
Capacity Constrained Transit Assignment with Common Lines 总被引:1,自引:0,他引:1
Fumitaka Kurauchi Michael G. H. Bell Jan-Dirk Schmöcker 《Journal of Mathematical Modelling and Algorithms》2003,2(4):309-327
This paper proposes the use of absorbing Markov chains to solve the capacity constrained transit network loading problem taking
common lines into account. The approach handles congested transit networks, where some passengers will not be able to board
because of the absence of sufficient space. The model also handles the common lines problem, where choice of route depends
on frequency of arrivals. The mathematical formulation of the problem is presented together with a numerical example.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
34.
35.
In this paper, we investigate the exact distribution of the waiting time for ther-th ℓ-overlapping occurrence of success-runs of a specified length in a sequence of two state Markov dependent trials. The
probability generating functions are derived explicitly, and as asymptotic results, relationships of a negative binomial distribution
of orderk and an extended Poisson distribution of orderk are discussed. We provide further insights into the run-related problems from the viewpoint of the ℓ-overlapping enumeration
scheme. We also study the exact distribution of the number of ℓ-overlapping occurrences of success-runs in a fixed number
of trials and derive the probability generating functions. The present work extends several properties of distributions of
orderk and leads us a new type of geneses of the discrete distributions. 相似文献
36.
37.
38.
By Hückel molecular orbital (HMO) theory, the calculation of the total energy of all π-electrons in conjugated hydrocarbons can be reduced to that of E(G)=|λ1|+|λ2|+?+|λn|, where λi are the eigenvalues of the corresponding graph G. Denote by Ψn the set of all fully-angular polyhex chains with n hexagons. In this paper, we show that Hn has the minimum total π-electron energy among chains in Ψn, where Hn is the helicene chain. 相似文献
39.
Richard O. LaMaire 《Queueing Systems》1992,11(4):357-375
We define and analyze anM/G/1/N vacation model that uses a service discipline that we call theE-limited with limit variation discipline. According to this discipline, the server provides service until either the system is emptied (i.e. exhausted) or a randomly chosen limit ofl customers has been served. The server then goes on a vacation before returning to service the queue again. The queue length distribution and the Laplace-Stieltjes transforms of the waiting time, busy period and cycle time distributions are found. Further, an expression for the mean waiting time is developed. Several previously analyzed service disciplines, including Bernoulli scheduling, nonexhaustive service and limited service, are special cases of the general varying limit discipline that is analyzed in this paper. 相似文献
40.
Multi-objective optimization using evolutionary algorithms identifies Pareto-optimal alternatives or their close approximation by means of a sequence of successive local improvement moves. While several successful applications to combinatorial optimization problems are known, studies of underlying problem structures are still scarce. 相似文献