全文获取类型
收费全文 | 3009篇 |
免费 | 96篇 |
国内免费 | 21篇 |
专业分类
化学 | 2038篇 |
晶体学 | 20篇 |
力学 | 116篇 |
数学 | 524篇 |
物理学 | 428篇 |
出版年
2023年 | 27篇 |
2022年 | 48篇 |
2021年 | 45篇 |
2020年 | 50篇 |
2019年 | 77篇 |
2018年 | 44篇 |
2017年 | 28篇 |
2016年 | 85篇 |
2015年 | 95篇 |
2014年 | 109篇 |
2013年 | 155篇 |
2012年 | 214篇 |
2011年 | 247篇 |
2010年 | 157篇 |
2009年 | 133篇 |
2008年 | 170篇 |
2007年 | 185篇 |
2006年 | 190篇 |
2005年 | 187篇 |
2004年 | 176篇 |
2003年 | 112篇 |
2002年 | 115篇 |
2001年 | 43篇 |
2000年 | 40篇 |
1999年 | 24篇 |
1998年 | 27篇 |
1997年 | 26篇 |
1996年 | 24篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 23篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 21篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有3126条查询结果,搜索用时 15 毫秒
21.
The synthesis of novel symmetrical liquid crystalline compounds based on 5-methyl-5-[2-(4-alkyloxyphenyl)-2-hydroxyethyl]-2,2-bipyridines is reported, together with some physical properties. Although the chelating head-groups are connected via a chiral sp3 carbon atom, all the materials are mesomorphic. Intermolecular hydrogen bonding between pyridino and hydroxy fragments in the mesophases is made apparent by FTIR spectroscopy. 相似文献
22.
Laurent Chupin 《Journal of Mathematical Fluid Mechanics》2013,15(4):783-806
We consider the flows of viscoelastic fluid which obey a constitutive law of integral type. Some theoretical results are proved: local existence, global existence with small data and uniqueness results for the initial boundary value problem. 相似文献
23.
24.
Laurent François Joël Dupays Dmitry Davidenko Marc Massot 《Combustion Theory and Modelling》2020,24(5):775-809
We investigate a model of solid propellant combustion involving surface pyrolysis coupled to finite activation energy gas-phase combustion. Existence and uniqueness of a travelling wave solution are established by extending dynamical system tools classically used for premixed flames, dealing with the additional difficulty arising from the surface regression and pyrolysis. An efficient shooting method allows to solve the problem in phase space without resorting to space discretisation nor fixed-point Newton iterations. The results are compared to solutions from a CFD code developed at ONERA, assessing the efficiency and potential of the method, and the impact of the modelling assumptions is evaluated through parametric studies. 相似文献
25.
Laurent Decreusefond Hélène Halconruy 《Stochastic Processes and their Applications》2019,129(8):2611-2653
On any denumerable product of probability spaces, we construct a Malliavin gradient and then a divergence and a number operator. This yields a Dirichlet structure which can be shown to approach the usual structures for Poisson and Brownian processes. We obtain versions of almost all the classical functional inequalities in discrete settings which show that the Efron–Stein inequality can be interpreted as a Poincaré inequality or that the Hoeffding decomposition of -statistics can be interpreted as an avatar of the Clark representation formula. Thanks to our framework, we obtain a bound for the distance between the distribution of any functional of independent variables and the Gaussian and Gamma distributions. 相似文献
26.
27.
28.
We report the operation of a 50 mW continuous-wave quantum cascade laser (QCL) in the 9.2 microm range, phase locked to a single-mode CO(2) laser with a tunable frequency offset. The wide free-running emission spectrum of the QCL (3-5 MHz) is strongly narrowed down to the kilohertz range, making it suitable for high-resolution molecular spectroscopy. 相似文献
29.
30.
The numerical approximation of one-dimensional relativistic Dirac wave equations is considered within the recent framework consisting in deriving local scattering matrices at each interface of the uniform Cartesian computational grid. For a Courant number equal to unity, it is rigorously shown that such a discretization preserves exactly the \(L^2\) norm despite being explicit in time. This construction is well-suited for particles for which the reference velocity is of the order of \(c\), the speed of light. Moreover, when \(c\) diverges, that is to say, for slow particles (the characteristic scale of the motion is non-relativistic), Dirac equations are naturally written so as to let a “diffusive limit” emerge numerically, like for discrete 2-velocity kinetic models. It is shown that an asymptotic-preserving scheme can be deduced from the aforementioned well-balanced one, with the following properties: it yields unconditionally a classical Schrödinger equation for free particles, but it handles the more intricate case with an external potential only conditionally (the grid should be such that \(c \Delta x\rightarrow 0\)). Such a stringent restriction on the computational grid can be circumvented easily in order to derive a seemingly original Schrödinger scheme still containing tiny relativistic features. Numerical tests (on both linear and nonlinear equations) are displayed. 相似文献