全文获取类型
收费全文 | 90605篇 |
免费 | 2618篇 |
国内免费 | 2340篇 |
专业分类
化学 | 34027篇 |
晶体学 | 983篇 |
力学 | 7530篇 |
综合类 | 142篇 |
数学 | 33219篇 |
物理学 | 19662篇 |
出版年
2024年 | 42篇 |
2023年 | 293篇 |
2022年 | 486篇 |
2021年 | 565篇 |
2020年 | 704篇 |
2019年 | 666篇 |
2018年 | 10849篇 |
2017年 | 10699篇 |
2016年 | 6672篇 |
2015年 | 1535篇 |
2014年 | 1120篇 |
2013年 | 1359篇 |
2012年 | 4933篇 |
2011年 | 11699篇 |
2010年 | 6476篇 |
2009年 | 6820篇 |
2008年 | 7429篇 |
2007年 | 9395篇 |
2006年 | 840篇 |
2005年 | 1840篇 |
2004年 | 1960篇 |
2003年 | 2337篇 |
2002年 | 1425篇 |
2001年 | 594篇 |
2000年 | 551篇 |
1999年 | 391篇 |
1998年 | 379篇 |
1997年 | 306篇 |
1996年 | 375篇 |
1995年 | 264篇 |
1994年 | 230篇 |
1993年 | 207篇 |
1992年 | 131篇 |
1991年 | 134篇 |
1990年 | 110篇 |
1989年 | 120篇 |
1988年 | 102篇 |
1987年 | 90篇 |
1986年 | 97篇 |
1985年 | 89篇 |
1984年 | 63篇 |
1983年 | 55篇 |
1982年 | 59篇 |
1981年 | 50篇 |
1980年 | 53篇 |
1979年 | 46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
91.
Pascal Noble 《Archive for Rational Mechanics and Analysis》2007,186(1):53-76
The phenomenon of roll-waves occurs when shallow water flows down open inclined channels. This flow is described by the Saint
Venant’s equations with a friction term due to Chezy. In the case of a flat bottom, their existence (as entropic and periodic
travelling waves) follows from a classical work due to DRESSLER [6].
The aim of this paper is to prove the existence of roll-waves when the bottom is modulated by a small periodic perturbation.
Following JIN and KATSOULAKIS [15], we first compute a Burgers-type equation which possesses “pulsating” roll-waves (the wave
speed oscillates around an average velocity). We prove, in a mathematically rigorous fashion, the existence of these solutions. 相似文献
92.
93.
Michael Struwe 《Calculus of Variations and Partial Differential Equations》2003,16(4):431-437
Extending our previous work [5] on this subject we show global existence of smooth solutions to the Cauchy problem for wave
maps from the (1 + 2)-dimensional Minkowski space to an arbitrary smooth, compact Riemannian manifold without boundary, for
arbitrary smooth, radially symmetric data.
Received: 14 December 2001 / Accepted: 1 March 2002 / Published online: 6 August 2002 相似文献
94.
We consider the differential operators Ψ
k
, defined by Ψ1(y) =y and Ψ
k+1(y)=yΨ
k
y+d/dz(Ψ
k
(y)) fork ∈ ℕ fork∈ ℕ. We show that ifF is meromorphic in ℂ and Ψ
k
F has no zeros for somek≥3, and if the residues at the simple poles ofF are not positive integers, thenF has the formF(z)=((k-1)z+a)/(z
2+β
z+γ) orF(z)=1/(az+β) where α, β, γ ∈ ℂ. If the residues at the simple poles ofF are bounded away from zero, then this also holds fork=2. We further show that, under suitable additional conditions, a family of meromorphic functionsF is normal if each Ψ
k
(F) has no zeros. These conditions are satisfied, in particular, if there exists δ>0 such that Re (Res(F, a)) <−δ for all polea of eachF in the family. Using the fact that Ψ
k
(f
′/f) =f
(k)/f, we deduce in particular that iff andf
(k) have no zeros for allf in some familyF of meromorphic functions, wherek≥2, then {f
′/f :f ∈F} is normal.
The first author is supported by the German-Israeli Foundation for Scientific Research and Development G.I.F., G-643-117.6/1999,
and INTAS-99-00089. The second author thanks the DAAD for supporting a visit to Kiel in June–July 2002. Both authors thank
Günter Frank for helpful discussions. 相似文献
95.
For ϕ a δ-subharmonic function, sharp results are obtained that connectA(r, ϕ), B(r, ϕ) andT(r, ϕ), whereA(r, ϕ)=inf|z|=r
ϕ(z),B(r, ϕ)=sup|z|=r
ϕ(z), andT(r, ϕ) is the Nevanlinna characteristics. 相似文献
96.
Lihong Wang 《Annals of the Institute of Statistical Mathematics》2004,56(2):251-264
The purpose of this paper is to investigate the asymptotic properties of the least squares estimates (L
2-estimates) and the least absolute deviation estimates (L
1-estimates) of the parameters of a nonlinear regression model subject to a set of equality and inequality restrictions, which
has a long-range dependent stationary process as its stochastic errors. Then we will compare the asymptotic relative efficiencies
of the above estimators. 相似文献
97.
98.
一种小波域音频信息隐藏方法 总被引:1,自引:0,他引:1
提出了一种基于量化的小波域音频隐藏算法,将保密语音隐藏到载体音频中.为提高隐藏重和保密语音传输的安全性,对保密语音进行了小波域压缩编码和m序列的扩频调制,生成待隐藏的比特序列;通过量化方法,将编码和调制后的保密语音隐藏到载体音频的小波系数中;保密语音的恢复过程不需要使用原始音频、仿真结果表明,隐藏有保密语音的载体音频听觉质量没有明显下降,提取的保密语音感知质量较好;该算法对重量化、加噪、低通滤波等攻击均有良好的鲁棒性. 相似文献
99.
100.