全文获取类型
收费全文 | 144489篇 |
免费 | 33358篇 |
国内免费 | 12906篇 |
专业分类
化学 | 124509篇 |
晶体学 | 1261篇 |
力学 | 8046篇 |
综合类 | 792篇 |
数学 | 15861篇 |
物理学 | 40284篇 |
出版年
2024年 | 380篇 |
2023年 | 5305篇 |
2022年 | 4485篇 |
2021年 | 5954篇 |
2020年 | 8235篇 |
2019年 | 6168篇 |
2018年 | 5615篇 |
2017年 | 3909篇 |
2016年 | 9976篇 |
2015年 | 9847篇 |
2014年 | 10488篇 |
2013年 | 12485篇 |
2012年 | 12330篇 |
2011年 | 10807篇 |
2010年 | 10028篇 |
2009年 | 9777篇 |
2008年 | 7935篇 |
2007年 | 6927篇 |
2006年 | 5934篇 |
2005年 | 4948篇 |
2004年 | 3866篇 |
2003年 | 3150篇 |
2002年 | 2916篇 |
2001年 | 2462篇 |
2000年 | 2097篇 |
1999年 | 2200篇 |
1998年 | 1814篇 |
1997年 | 1675篇 |
1996年 | 1679篇 |
1995年 | 1558篇 |
1994年 | 1375篇 |
1993年 | 1249篇 |
1992年 | 1020篇 |
1991年 | 857篇 |
1990年 | 728篇 |
1989年 | 590篇 |
1988年 | 497篇 |
1987年 | 450篇 |
1986年 | 428篇 |
1985年 | 363篇 |
1977年 | 326篇 |
1976年 | 384篇 |
1975年 | 479篇 |
1974年 | 478篇 |
1973年 | 302篇 |
1972年 | 375篇 |
1971年 | 360篇 |
1970年 | 547篇 |
1969年 | 419篇 |
1968年 | 463篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
971.
李永昆 《纯粹数学与应用数学》1998,14(2):23-27
讨论了时滞Duffing系统x+Cx+gradG「x(t-τ(t))」=P(t)=P(t+2π)的2π周期解的存在性。 相似文献
972.
Bingzheng Li 《应用数学学报(英文版)》1997,13(2):209-220
We modify Szász-Durrmeyer operators by means of three-diagonal generalized matrix which overcomes a difficulty in extending a Berens-Lorentz result to the Szász-Durrmeyer operators for second order of smoothness. The direct and converse theorems for these operators inL
p
are also presented by Ditzian-Totik modulus of smoothness.This project is supported by Zhejiang Provincial Foundation of China. 相似文献
973.
LetB1:
n×
N1→
m1,B2:
n×
N2→
m2andQ:
m2→
m1be bilinear forms which are related as follows: ifμandνsatisfyB1(ξ, μ)=0 andB2(ξ, ν)=0 for someξ≠0, thenμτQν=0. Supposep−1+q−1=1. Coifman, Lions, Meyer and Semmes proved that, ifuLp(
n) andvLq(
n), and the first order systemsB1(D, u)=0,B2(D, v)=0 hold, thenuτQvbelongs to the Hardy spaceH1(
n), provided that both (i)p=q=2, and (ii) the ranks of the linear mapsBj(ξ, ·) :
Nj→
m1are constant. We apply the theory of paracommutators to show that this result remains valid when only one of the hypotheses (i), (ii) is postulated. The removal of the constant-rank condition whenp=q=2 involves the use of a deep result of Lojasiewicz from singularity theory. 相似文献
974.
In this Letter, structural properties of liquid Ni20Al80 have been studied through molecular dynamics (MD) simulations, and results agree well with X-ray experiments. The prepeak in the structure factor manifests the existence of medium-range structural order (MRSO) in liquid Ni20Al80. Analyses in MRSO reveal the dominance of ideal icosahedra and defective icosahedra which, furthermore, form clusters and share common atoms. 相似文献
975.
976.
Li Chen Ling Hsiao Gerald Warnecke 《应用数学学报(英文版)》2007,23(1):9-28
This paper considers a kind of strongly coupled cross diffusion parabolic system,which can be usedas the multi-dimensional Lyumkis energy transport model in semiconductor science.The global existence andlarge time behavior are obtained for smooth solution to the initial boundary value problem.When the initialdata are a small perturbation of an isothermal stationary solution,the smooth solution of the problem under theinsulating boundary condition,converges to that stationary solution exponentially fast as time goes to infinity. 相似文献
977.
The segregation of P at grain boundaries is believed to be an important cause of temper embrittlement in steels. As an alloy element, Mo may reduce the embrittlement. However, the concentration measured by Auger electron spectroscopy at the grain boundary in 2.25Cr1MoV and 12Cr1MoV showed that the concentration of P increased with that of Mo, which indicates that Mo and P cosegregated to the grain boundary in Cr-Mo steels. 相似文献
978.
M K Parida Nita Sinha B Adhikary B Allanach A Alok K S Babu B Brahmachari D Choudhury E J Chun P K Das A Ghosal D Hitlin W S Hou S Kumar H N Li E Ma S K Majee G Majumdar B Mishra G Mohanty S Nandi H Pas M K Parida S D Rindani J P Saha N Sahu Y Sakai S Sen C Sharma C D Sharma S Shalgar N N Singh S Uma Sankar N Sinha R Sinha F Simonetto R Srikanth R Vaidya 《Pramana》2006,67(5):849-860
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been
mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions
carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently. 相似文献
979.
黎勇 《数学物理学报(B辑英文版)》2007,27(2):437-448
In this article, two relaxation time limits, namely, the momentum relaxation time limit and the energy relaxation time limit are considered. By the compactness argument, it is obtained that the smooth solutions of the multidimensional nonisentropic Euler-Poisson problem converge to the solutions of an energy transport model or a drift diffusion model, respectively, with respect to different time scales. 相似文献
980.
The duplication and divergence process is ubiquitous in nature and man-made networks. Motivated by the duplication-divergence mechanism which depicts the growth of protein networks, we propose a weighted network model in which topological evolution is coupled with weight dynamics. Large scale numerical results indicate that our model can naturally generate networks with power-law-like distributions of degree, strength and weight. The degree-strength correlation is illustrated as well. These properties are in agreement well with empirical data observed in real-world systems. Furthermore, by altering the retention probability δ, weighted, structured exponential networks are realized. 相似文献