全文获取类型
收费全文 | 84904篇 |
免费 | 1885篇 |
国内免费 | 155篇 |
专业分类
化学 | 47658篇 |
晶体学 | 914篇 |
力学 | 2406篇 |
综合类 | 3篇 |
数学 | 12872篇 |
物理学 | 23091篇 |
出版年
2022年 | 591篇 |
2021年 | 808篇 |
2020年 | 988篇 |
2019年 | 935篇 |
2018年 | 1493篇 |
2017年 | 1328篇 |
2016年 | 2379篇 |
2015年 | 1812篇 |
2014年 | 2067篇 |
2013年 | 4634篇 |
2012年 | 4363篇 |
2011年 | 4583篇 |
2010年 | 3144篇 |
2009年 | 2864篇 |
2008年 | 3899篇 |
2007年 | 3667篇 |
2006年 | 3272篇 |
2005年 | 3151篇 |
2004年 | 2830篇 |
2003年 | 2380篇 |
2002年 | 2132篇 |
2001年 | 2254篇 |
2000年 | 1902篇 |
1999年 | 1451篇 |
1998年 | 1113篇 |
1997年 | 1022篇 |
1996年 | 1079篇 |
1995年 | 888篇 |
1994年 | 927篇 |
1993年 | 847篇 |
1992年 | 934篇 |
1991年 | 859篇 |
1990年 | 906篇 |
1989年 | 785篇 |
1988年 | 805篇 |
1987年 | 754篇 |
1986年 | 701篇 |
1985年 | 879篇 |
1984年 | 890篇 |
1983年 | 693篇 |
1982年 | 730篇 |
1981年 | 724篇 |
1980年 | 616篇 |
1979年 | 685篇 |
1978年 | 660篇 |
1977年 | 650篇 |
1976年 | 677篇 |
1975年 | 580篇 |
1974年 | 575篇 |
1973年 | 610篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
31.
Supposa that f(x) is a quasidifferentiable function, defined on S(?)R~n where S is an open set, with a -equivalent bounded quasidifferential subfam ily. Lenma I 相似文献
32.
In the study of the behaviors of barriers in an enclosed field, one should take into account such phenomena as sound energy reflection, absorption, scattering and diffraction. Therefore, the study is much more difficult than that in free field. In this paper, sound barriers are classified into four kinds according to their size, number and shape. Each kind of barriers is modelled by a corresponding method based on a computer program—SOFIS. The program combines the ray-tracing technique and statistical method. The impulse response and some acoustical parameters such as sound pressure level at different positions can be calculated by the program, no matter there are a certain kind of barriers in the field or the field is empty. The ray-tracing program and the algorithms for various barriers are validated by the comparison between measurement and prediction of the reverberation room and the anechoic room of the Northwestern Polytechnic University. 相似文献
33.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
34.
35.
Lubomír Kubáček 《Applications of Mathematics》2006,51(6):565-582
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate
regression model.
This work was supported by the Council of Czech Government J14/98:153100011. 相似文献
36.
Lithium (10–150 ng ml?1) in wine is determined by atomic absorption spectrometry by direct nebulization and after digestion with mixed acids. The results of methods are similar. Thirty-four wines from various Spanish provinces are analysed. 相似文献
37.
Gábor Dörnyei Marietta Bárczai-Beke Gábor Blaskó Péter Péchy Csaba Szántay 《Tetrahedron letters》1982,23(28):2913-2916
Regioselective demethylation of 3,4-dihydropapaveraldine (a) at 7 and 3' positions affords a properly substituted diphenolic key intermidiate (d) for the synthesis of reticuline and N-norreticuline. 相似文献
38.
V. Čápek 《Czechoslovak Journal of Physics》1991,41(10):975-989
A review of ideas leading to full rejection of any finite or partially-infinite order kinetic equation linearized in external field is given on grounds of the time-convolution Generalized Master Equations (GME). By two examples (two-level and band conduction problem), it is shown how standard kinetic equations result from GME in the lowest order approximations which obscure, however, a direct correspondence with the Kubo linear response theory. Without approximations, on the other hand, the rigorous approach is shown to be fully equivalent with the Kubo results. It is argued and illustrated that usual technical simplicity and seeming physical lucidity of standard theories (connected with the presence of field-independent transfer or scattering rates in the fielddependent linearized theory) are just owing to structural features which are solely due to the lowest order approximations involved. These features (i.e. also the possibility of standard physical interpretation of kinetic phenomena) are proved to disappear completely as far as the theory goes properly to higher orders. 相似文献
39.
High-temperature series expansions of the susceptibility and second moment to 15th order are calculated for zero external field on the linear chain (LC), plane square (PSQ), simple cubic (SC), and body-centered cubic (BCC) lattices. Checks for specific models against pertinent work in the literature are detailed. 相似文献
40.
A Modified Quasi-Newton Method for Structured Optimization with Partial Information on the Hessian 总被引:2,自引:0,他引:2
This paper develops a modified quasi-Newton method for structured unconstrained optimization with partial information on the
Hessian, based on a better approximation to the Hessian in current search direction. The new approximation is decided by both
function values and gradients at the last two iterations unlike the original one which only uses the gradients at the last
two iterations. The modified method owns local and superlinear convergence. Numerical experiments show that the proposed method
is encouraging comparing with the methods proposed in [4] for structured unconstrained optimization
Presented at the 6th International Conference on Optimization: Techniques and Applications, Ballarat, Australia, December
9–11, 2004 相似文献