全文获取类型
收费全文 | 97068篇 |
免费 | 8619篇 |
国内免费 | 7599篇 |
专业分类
化学 | 28163篇 |
晶体学 | 364篇 |
力学 | 6936篇 |
综合类 | 1272篇 |
数学 | 25129篇 |
物理学 | 26874篇 |
无线电 | 24548篇 |
出版年
2024年 | 165篇 |
2023年 | 899篇 |
2022年 | 1558篇 |
2021年 | 1887篇 |
2020年 | 2045篇 |
2019年 | 2041篇 |
2018年 | 1796篇 |
2017年 | 2298篇 |
2016年 | 2672篇 |
2015年 | 2684篇 |
2014年 | 4268篇 |
2013年 | 6016篇 |
2012年 | 4623篇 |
2011年 | 4960篇 |
2010年 | 4070篇 |
2009年 | 5237篇 |
2008年 | 5919篇 |
2007年 | 6208篇 |
2006年 | 5884篇 |
2005年 | 5137篇 |
2004年 | 4697篇 |
2003年 | 4642篇 |
2002年 | 4107篇 |
2001年 | 3484篇 |
2000年 | 3263篇 |
1999年 | 2848篇 |
1998年 | 2550篇 |
1997年 | 2168篇 |
1996年 | 1954篇 |
1995年 | 1732篇 |
1994年 | 1559篇 |
1993年 | 1333篇 |
1992年 | 1255篇 |
1991年 | 1003篇 |
1990年 | 814篇 |
1989年 | 673篇 |
1988年 | 574篇 |
1987年 | 444篇 |
1986年 | 371篇 |
1985年 | 438篇 |
1984年 | 439篇 |
1983年 | 217篇 |
1982年 | 343篇 |
1981年 | 406篇 |
1980年 | 305篇 |
1979年 | 294篇 |
1978年 | 221篇 |
1977年 | 207篇 |
1976年 | 155篇 |
1974年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
841.
LI Ya-feng~ ** ZHANG Li-mei~ WU Lei-lei~ WANG Sheng-hai~ WANG Hai-lian~ SHANG Xuan-xuan~ . College of Chemistry Molecular Engineering . College of Mathematics Physics Qingdao University of Science & Technology Qingdao P. R. China 《高等学校化学研究》2006,(6)
IntroductionThe interest in polyoxometalates that are widelyused in medical chemistry, catalyst reactions, and ma-terial sciences stems from their complicated aggregatesformed by means of corner-, edge- and face-sha-ring[1—4]. The exploitation of new str… 相似文献
842.
“Optimization of aircraft maintenance/support infrastructure using genetic algorithms—level of repair analysis” 总被引:4,自引:0,他引:4
Level of repair analysis (LORA) is an approach used during the design stage of complex equipment for analysis of the cost
effectiveness of competing maintenance strategies. LORA is carried as a part of the life cycle cost and cost of ownership
analysis and plays a significant role in minimizing the life cycle cost and cost of ownership of the capital equipment. Since
many purchasing decisions of complex equipment are based on cost of ownership, it has become essential to carry out LORA to
compete in the market. In this paper, we develop a mathematical model for LORA and propose a solution methodology based on
genetic algorithms. The concept is illustrated using a hypothetical aircraft engine. 相似文献
843.
Given a constant of motion for the one-dimensional harmonic oscillator with linear dissipation in the velocity, the problem to get the Hamiltonian for this system is pointed out, and the quantization up to second order in the perturbation approach is used to determine the modification on the eigenvalues when dissipation is taken into consideration. This quantization is realized using the constant of motion instead of the Hamiltonian.
PACS: 03.20.+i, 03.30.+p, 03.65.−w,03.65.Ca 相似文献
844.
By introducing a four-layer step-index waveguide modeling, the characteristics of long-period fiber grating (LPFG) with an nm-thick film overlay, which has higher refractive index than that of fiber cladding are investigated in detail. The influence of both the overlay thickness and refractive index on the tuning ability of LPFG is analyzed. The numerical results demonstrate that spectral response of LPFG is divided into three distinct regions as the overlay deposition increases and the shift of resonant wavelength is drastic in some special thickness range. In conjunction with higher-order cladding mode coupling and fiber cladding etching, the sensitivity of LPFG to the overlay refractive index is enhanced significantly and over 120 nm resonant wavelength tunable range is achieved. 相似文献
845.
846.
847.
Alexandra Shlapentokh 《Compositio Mathematica》2002,132(1):99-120
Let F be a function field of characteristic p > 2, finitely generated over a field C algebraic over a finite field C
p
and such that it has an extension of degree p. Then Hilbert's Tenth Problem is not decidable over F. 相似文献
848.
849.
A. S. Belenky 《Mathematical and Computer Modelling》2002,36(11-13)
Two games of interacting between a coalition of players in a marketplace and the residual players acting there are discussed, along with two approaches to fair imputation of gains of coalitions in cooperative games that are based on the concepts of the Shapley vector and core of a cooperative game. In the first game, which is an antagonistic one, the residual players try to minimize the coalition's gain, whereas in the second game, which is a noncooperative one, they try to maximize their own gain as a coalition. A meaningful interpretation of possible relations between gains and Nash equilibrium strategies in both games considered as those played between a coalition of firms and its surrounding in a particular marketplace in the framework of two classes of n-person games is presented. A particular class of games of choosing partners and forming coalitions in which models of firms operating in the marketplace are those with linear constraints and utility functions being sums of linear and bilinear functions of two corresponding vector arguments is analyzed, and a set of maximin problems on polyhedral sets of connected strategies which the problem of choosing a coalition for a particular firm is reducible to are formulated based on the firm models of the considered kind. 相似文献
850.