全文获取类型
收费全文 | 92705篇 |
免费 | 568篇 |
国内免费 | 408篇 |
专业分类
化学 | 27444篇 |
晶体学 | 809篇 |
力学 | 6879篇 |
数学 | 32976篇 |
物理学 | 15940篇 |
无线电 | 9633篇 |
出版年
2023年 | 66篇 |
2022年 | 139篇 |
2021年 | 196篇 |
2020年 | 176篇 |
2019年 | 171篇 |
2018年 | 11900篇 |
2017年 | 11513篇 |
2016年 | 7179篇 |
2015年 | 1118篇 |
2014年 | 594篇 |
2013年 | 672篇 |
2012年 | 4558篇 |
2011年 | 12052篇 |
2010年 | 7068篇 |
2009年 | 6994篇 |
2008年 | 7504篇 |
2007年 | 9918篇 |
2006年 | 531篇 |
2005年 | 1838篇 |
2004年 | 1965篇 |
2003年 | 2324篇 |
2002年 | 1247篇 |
2001年 | 320篇 |
2000年 | 335篇 |
1999年 | 220篇 |
1998年 | 240篇 |
1997年 | 210篇 |
1996年 | 243篇 |
1995年 | 163篇 |
1994年 | 121篇 |
1993年 | 128篇 |
1992年 | 81篇 |
1991年 | 91篇 |
1990年 | 71篇 |
1989年 | 78篇 |
1988年 | 80篇 |
1987年 | 82篇 |
1986年 | 76篇 |
1985年 | 72篇 |
1984年 | 65篇 |
1983年 | 51篇 |
1982年 | 63篇 |
1981年 | 50篇 |
1980年 | 60篇 |
1979年 | 58篇 |
1978年 | 50篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Chris Quigg 《EPJ direct》2002,4(1):1-15
We study the branching ratio, CP-violating asymmetry, forward-backward asymmetry and the CP-violating asymmetry in the forward-backward asymmetry for the exclusive decay B → Kτ+τ− in the two Higgs doublet model with tree level flavor changing neutral currents (model III). We analyse the dependencies of these quantities on the neutral Higgs boson contributions and the CP parameter sinθ in the model III. We observe that to determine the neutral Higgs boson effects, the measurements of the forward-backward asymmetry and the CP-violating asymmetry in the forward-backward asymmetry for the decay B → Kτ+τ− are promising. 相似文献
72.
73.
74.
Anindya Datta 《Pramana》2003,60(2):363-368
We propose a novel method for the search of supersymmetry, especially for the electroweak gauginos at the large hadron collider
(LHC). Gauge boson fusion technique was shown to be useful for heavy and intermediate mass Higgs bosons. In this article,
we have shown that this method can also be applied to find the signals of EW gauginos in supersymmetric theories where the
canonical search strategies for these particles fail. 相似文献
75.
A group of machines for processing a set of jobs in a manufacturing system is often located in a serial line. An efficient strategy for locating these machines such that the total travel distance or the cost of transporting the jobs is minimized is desired. In this research, the assumption of a linear line with equally spaced machine location is relaxed. This research addressed problems of locating unique machines. It is found that the machine distances possess unique properties in this type of a problem. Utilizing these properties, heuristic strategies are proposed to obtain efficient solution where optimal methods are expected to be computationally prohibitive. A lower bound for the optimum solution is also proposed. Results are encouraging. 相似文献
76.
We derive the Kramers equation, namely, the Fokker-Planck equation for an oscillator, from a completely deterministic picture. The oscillator is coupled to a “booster”, i.e., a deterministic system in a fully chaotic state, wherein diffusion is derived from the sensitive dependence of chaos on initial conditions and friction is a consequence of the linear response of the booster to the action exerted on it by the oscillator. To deal with the Hamiltonian nature of the system of interest and of its coupling to the booster, we extend the earlier theoretical derivation of macroscopic transport coefficients from deterministic dynamics. We show that the frequency of the oscillator can be tuned to the microscopic frequencies of the booster without affecting the canonical nature of the “macroscopic” statistics. The theoretical predictions are supported by numerical simulations. 相似文献
77.
Cornelis Van de Panne 《The Journal of the Operational Research Society》1992,43(12):1159-1171
The paper deals with the appropriate form of interaction between two refineries with different demand patterns. This problem can be formulated as finding a decentralized solution of linear programming problems linked by buying and selling activities. The complete problem is first solved for central values of product demands and costs and revenues. The structure of the basis then determines the organization of the interaction in terms of which unit sets quantities and which prices, or whether centralized decisions should be made. If, for expected values of product demand and costs, the structure of the basis is the same then the related organization of trading can be used for day-to-day transactions. For a well-known oil refinery model it is found that, for fairly large demand variations, decentralized interaction is effective, but that the structure of the basis changes easily with crude price variations, and that simulations did not converge for these variations. 相似文献
78.
79.
James Tanton 《Mathematical Intelligencer》2007,29(3):55-59
This column is a place for those bits of contagious mathematics that travel from person to person in the community, because
they are so elegant, suprising, or appealing that one has an urge to pass them on.
Contributions are most welcome. 相似文献
80.
MuShanxiang JiXiaoli LiMing LiXingguo 《电子科学学刊(英文版)》2003,20(6):407-413
Linear Modulated Frequency (LMF) Costas Stepped Frequency Radar (SFR) signal is introduced. Its ambiguity function is derived and analyzed in detail and its feasibility is validated in theory. The scheme of the proposed signal processing is also presented. The results of theoretic analysis and simulation show that, by using the proposed signal and increasing the bandwidth of the total stepped frequency, the ambiguity sidelobe is well suppressed and the range-velocity coupling in the stepped frequency radar is also greatly weakened. 相似文献