全文获取类型
收费全文 | 31201篇 |
免费 | 973篇 |
国内免费 | 386篇 |
专业分类
化学 | 21827篇 |
晶体学 | 188篇 |
力学 | 732篇 |
综合类 | 30篇 |
数学 | 4231篇 |
物理学 | 5552篇 |
出版年
2023年 | 198篇 |
2022年 | 640篇 |
2021年 | 735篇 |
2020年 | 519篇 |
2019年 | 576篇 |
2018年 | 477篇 |
2017年 | 393篇 |
2016年 | 848篇 |
2015年 | 807篇 |
2014年 | 867篇 |
2013年 | 1732篇 |
2012年 | 1643篇 |
2011年 | 1933篇 |
2010年 | 1244篇 |
2009年 | 1207篇 |
2008年 | 1653篇 |
2007年 | 1667篇 |
2006年 | 1408篇 |
2005年 | 1332篇 |
2004年 | 1214篇 |
2003年 | 1124篇 |
2002年 | 1149篇 |
2001年 | 646篇 |
2000年 | 564篇 |
1999年 | 448篇 |
1998年 | 359篇 |
1997年 | 338篇 |
1996年 | 399篇 |
1995年 | 353篇 |
1994年 | 352篇 |
1993年 | 286篇 |
1992年 | 258篇 |
1991年 | 278篇 |
1990年 | 269篇 |
1989年 | 246篇 |
1988年 | 224篇 |
1987年 | 204篇 |
1986年 | 202篇 |
1985年 | 329篇 |
1984年 | 364篇 |
1983年 | 237篇 |
1982年 | 275篇 |
1981年 | 243篇 |
1980年 | 248篇 |
1979年 | 231篇 |
1978年 | 190篇 |
1977年 | 214篇 |
1976年 | 194篇 |
1975年 | 151篇 |
1974年 | 143篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
Paolo De Lucia J. D. Maitland Wright 《Rendiconti del Circolo Matematico di Palermo》1991,40(3):442-452
Dopo aver dato una definizione di parte convessa di un gruppo topologico, si stabilisce una condizione affinchè il condominio
di una misura sia convesso. 相似文献
83.
84.
Jaime E. Muñoz Rivera Maria Grazia Naso 《Journal of Mathematical Analysis and Applications》2007,326(1):691-707
We study the asymptotic behavior of the solutions of a class of linear dissipative integral differential equations. We show in the abstract setting a necessary and sufficient condition to get an exponential decay of the solution. In the case of the lack of exponential decay, we find the polynomial rate of decay of the solution. Some examples are given. 相似文献
85.
文章讨论无界区域上GBBM方程的Cauchy问题,对方程的解进行了先验估计,并证明了在H1弱拓扑中整体吸引子的存在性. 相似文献
86.
87.
Giovanni Tartarini Alessandra Lena Davide Passaro Lorenzo Rosa Stefano Selleri Pier Faccin Enrico Maria Fabbri 《Optical and Quantum Electronics》2006,38(9-11):869-876
A comprehensive numerical tool has been developed for the evaluation of the performances of Radio over Fiber (RoF) links intended for wireless signal distribution.At the transmitter end an appropriate set of rate equations allows to model the optical source as a solitary laser or as an appropriately injection locked laser. The optical channel is modeled putting into account the combined effect of fiber dispersion, laser source non ideal performances (e.g. non-linear effects, frequency chirp), and quadratic detection of the receiving photodiode. The simulation model developed can be a useful tool at the design stage allowing a preliminary evaluation of the characteristics of real RoF links. 相似文献
88.
Bart De Bruyn 《Journal of Algebraic Combinatorics》2006,24(1):23-29
Brouwer and Wilbrink [3] showed the nonexistence of regular near octagons whose parameters s, t2, t3 and t satisfy s ≥ 2, t2 ≥ 2 and t3 ≠ t2(t2+1). Later an arithmetical error was discovered in the proof. Because of this error, the existence problem was still open
for the near octagons corresponding with certain values of s, t2 and t3. In the present paper, we will also show the nonexistence of these remaining regular near octagons.
MSC2000 05B25, 05E30, 51E12
Postdoctoral Fellow of the Research Foundation - Flanders 相似文献
89.
De Ming ZHU Ying SUN 《数学学报(英文版)》2007,23(8):1495-1504
In this paper, we study the dynamical behavior for a 4-dimensional reversible system near its heteroclinic loop connecting a saddle-focus and a saddle. The existence of infinitely many reversible 1-homoclinic orbits to the saddle and 2-homoclinic orbits to the saddle-focus is shown. And it is also proved that, corresponding to each 1-homoclinic (resp. 2-homoclinic) orbit F, there is a spiral segment such that the associated orbits starting from the segment are all reversible 1-periodic (resp. 2-periodic) and accumulate onto F. Moreover, each 2-homoclinic orbit may be also accumulated by a sequence of reversible 4-homoclinic orbits. 相似文献
90.
S. O. Olabanji O. R. Omobuwajo D. Ceccato M. C. Buoso M. De Poli G. Moschini 《Journal of Radioanalytical and Nuclear Chemistry》2006,270(3):515-521
Summary Analysis of thirteen medicinal plants of various biological activities commonly used in South-western Nigeria was carried
out using PIXE technique. Nine of these plants are anti-cancer while four are antimicrobial. PIXE measurements were carried
out using collimated proton beams delivered by the 2. 5 MV AN 2000 Van de Graaff accelerator at the Istituto Nazionale di
Fisica Nucleare (INFN), (LNL) Legnaro, (Padova), Italy. The results showed the presence of twenty three different elements
in the plants and none of them contains any toxic heavy metals. Only Chenopodium ambrosioides showed detectable levels of selenium which is considered important in cancer prevention. 相似文献