全文获取类型
收费全文 | 30971篇 |
免费 | 4318篇 |
国内免费 | 2550篇 |
专业分类
化学 | 6870篇 |
晶体学 | 146篇 |
力学 | 5510篇 |
综合类 | 558篇 |
数学 | 12023篇 |
物理学 | 12732篇 |
出版年
2024年 | 62篇 |
2023年 | 292篇 |
2022年 | 827篇 |
2021年 | 834篇 |
2020年 | 980篇 |
2019年 | 858篇 |
2018年 | 812篇 |
2017年 | 1150篇 |
2016年 | 1310篇 |
2015年 | 982篇 |
2014年 | 1652篇 |
2013年 | 2436篇 |
2012年 | 1749篇 |
2011年 | 2023篇 |
2010年 | 1701篇 |
2009年 | 2036篇 |
2008年 | 1885篇 |
2007年 | 1940篇 |
2006年 | 1631篇 |
2005年 | 1494篇 |
2004年 | 1414篇 |
2003年 | 1200篇 |
2002年 | 1128篇 |
2001年 | 883篇 |
2000年 | 860篇 |
1999年 | 771篇 |
1998年 | 696篇 |
1997年 | 548篇 |
1996年 | 446篇 |
1995年 | 429篇 |
1994年 | 393篇 |
1993年 | 317篇 |
1992年 | 292篇 |
1991年 | 227篇 |
1990年 | 201篇 |
1989年 | 143篇 |
1988年 | 147篇 |
1987年 | 153篇 |
1986年 | 133篇 |
1985年 | 142篇 |
1984年 | 144篇 |
1983年 | 75篇 |
1982年 | 109篇 |
1981年 | 67篇 |
1980年 | 37篇 |
1979年 | 48篇 |
1978年 | 39篇 |
1977年 | 37篇 |
1976年 | 20篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Ekatherina A. Karatsuba 《Numerical Algorithms》2007,45(1-4):127-137
A new approach to the study of the Jaynes–Cummings sum, which determines the atomic inversion in quantum model of a single
two-level atom interacting with a single mode of the quantized radiation field, based on the number theory theorems on approximation
of trigonometric sums is presented.
相似文献
182.
魏立平 《数学的实践与认识》2004,34(4):1-4
综合运用国内外多种测量量表对大学生的心理素质进行诊断与测试 ,并应用多元统计分析方法对其心理素质结构主因素进行定量分析 ,在此基础上建立了心理素质诊断模型 ,并运用该模型对实际问题进行了分析 . 相似文献
183.
We consider two classes of integrable nonlinear hyperbolic systems on Lie algebras. These systems generalize the principal chiral model. Each system is related to a pair of compatible Lie brackets and has a Lax representation, which is determined by the direct sum decomposition of the Lie algebra of Laurent series into the subalgebra of Taylor series and the complementary subalgebra corresponding to the pair. New examples of compatible Lie brackets are given. 相似文献
184.
Piotr Biler 《Reports on Mathematical Physics》2003,52(2):205-225
We study asymptotic properties of solutions to an extension to arbitrary dimensions of the astrophysical model proposed by Chavanis et al. to explain phenomena of gravitational collapse in clouds of self-gravitating particles. In particular, we show that in the two-dimensional case the solutions can be continued to global ones, while in three space dimensions large data of negative energy blow up in a finite time. Relations between isothermal, Streater's energy-transport and the present models are also studied. 相似文献
185.
Jilly James Chidambaram Ramalechume Asit Baran Mandal 《Journal of Polymer Science.Polymer Physics》2007,45(17):2410-2420
The shape, size, aggregation, hydration, and correlation times of water insoluble PEO‐PPO‐PEO triblock copolymer micelles with sodium dodecylsulfate (SDS) micelles were investigated using transport studies and dynamic light scattering technique. From the conductance of micellar solutions of the polymer in 25 mM SDS and 5 mM NaCl, the hydration of polymer micelles were determined using the principle of obstruction of electrolyte migration by the polymer. The asymmetry of the micellar particles of polymer and polymer‐SDS mixed micellar systems in 5 mM NaCl and their average axial ratios were calculated using intrinsic viscosity and hydration data obeying Simha–Einstein equation. Hydration number and micellar sizes were variable with temperature. The shape of the polymer micelles has been ellipsoidal rather than spherical. The micellar volume, hydrodynamic radius, radius of gyration, diffusional coefficients as well as translational, rotational and effective correlation times have been calculated from the absolute values of the axes. The partial molal volume of polymer micelles has also been determined and its comparison with the molar volume of pure polymer suggested a volume contraction due to immobilization of the water phase by the hydrophilic head groups of the polymer. The thermodynamic activation parameters for viscous flow favor a more ordered water structure around polymer micelles at higher temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2410–2420, 2007 相似文献
186.
根据广义Laguerre多项式的数学性质,导出了较为简单的三维各向同性谐振子径向矩阵元的普遍公式,并在这基础上计算了一些重要特殊情形的径向矩阵元: 矢径r整数次幂的平均值,电偶极跃迁矩阵元和电四极跃迁矩阵元.
关键词:
三维各向同性谐振子
径向矩阵元
广义Laguerre多项式
偶极跃迁
四极跃迁 相似文献
187.
This paper proposes a method for estimation of a class of partially linear single-index models with randomly censored samples. The method provides a flexible way for modelling the association between a response and a set of predictor variables when the response variable is randomly censored. It presents a technique for “dimension reduction” in semiparametric censored regression models and generalizes the existing accelerated failure-time models for survival analysis. The estimation procedure involves three stages: first, transform the censored data into synthetic data or pseudo-responses unbiasedly; second, obtain quasi-likelihood estimates of the regression coefficients in both linear and single-index components by an iteratively algorithm; finally, estimate the unknown nonparametric regression function using techniques for univariate censored nonparametric regression. The estimators for the regression coefficients are shown to be jointly root-n consistent and asymptotically normal. In addition, the estimator for the unknown regression function is a local linear kernel regression estimator and can be estimated with the same efficiency as all the parameters are known. Monte Carlo simulations are conducted to illustrate the proposed methodology. 相似文献
188.
Lubomír Kubáček 《Mathematica Slovaca》2007,57(6):571-588
The multivariate model, where not only parameters of the mean value of the observation matrix, but also some other parameters
occur in constraints, is considered in the paper. Some basic inference is presented under the condition that the covariance
matrix is either unknown, or partially unknown, or known.
Supported by the grant of the Council of Czech Republic MSM 6 198 959 214. 相似文献
189.
190.
本文首先对回报率与交易量之间的关系进行了研究,发现并不存在非对称的数量关系,但存在双向的葛兰杰因果关系;同时将交易量对波动率的解释能力进行了研究,发现在沪市交易量对波动率具有解释力,而在深市交易量对波动率没有解释力。 相似文献