全文获取类型
收费全文 | 16713篇 |
免费 | 1647篇 |
国内免费 | 1235篇 |
专业分类
化学 | 2987篇 |
晶体学 | 113篇 |
力学 | 1580篇 |
综合类 | 444篇 |
数学 | 9632篇 |
物理学 | 4839篇 |
出版年
2023年 | 151篇 |
2022年 | 243篇 |
2021年 | 311篇 |
2020年 | 338篇 |
2019年 | 340篇 |
2018年 | 354篇 |
2017年 | 443篇 |
2016年 | 509篇 |
2015年 | 413篇 |
2014年 | 678篇 |
2013年 | 1134篇 |
2012年 | 745篇 |
2011年 | 983篇 |
2010年 | 978篇 |
2009年 | 1228篇 |
2008年 | 1165篇 |
2007年 | 1146篇 |
2006年 | 1073篇 |
2005年 | 826篇 |
2004年 | 725篇 |
2003年 | 721篇 |
2002年 | 668篇 |
2001年 | 562篇 |
2000年 | 488篇 |
1999年 | 449篇 |
1998年 | 405篇 |
1997年 | 342篇 |
1996年 | 303篇 |
1995年 | 222篇 |
1994年 | 193篇 |
1993年 | 166篇 |
1992年 | 183篇 |
1991年 | 130篇 |
1990年 | 112篇 |
1989年 | 94篇 |
1988年 | 78篇 |
1987年 | 79篇 |
1986年 | 41篇 |
1985年 | 74篇 |
1984年 | 68篇 |
1983年 | 39篇 |
1982年 | 71篇 |
1981年 | 44篇 |
1980年 | 45篇 |
1979年 | 61篇 |
1978年 | 42篇 |
1977年 | 35篇 |
1976年 | 23篇 |
1974年 | 21篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
H. Hussain B. H. Tan C. S. Gudipati Y. Liu C. B. He T. P. Davis 《Journal of polymer science. Part A, Polymer chemistry》2008,46(16):5604-5615
Amphiphilic diblock copolymers of polystyrene (PS) and poly(N‐vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well‐defined PS with bromine end group was synthesized by ATRP in bulk at 110 °C using (1‐bromoethyl) benzene as an initiator. The Br‐ end group was then converted to xanthate as verified by 1H NMR spectroscopy, elemental analysis, and UV‐spectroscopy. PS‐b‐PNVP copolymers were produced by MADIX of NVP in bulk at 60 °C using PS‐xanthate as a macro‐chain transfer agent and the kinetics of polymerization were investigated. The structures of PS‐b‐PNVP were characterized using GPC and 1H NMR. Amphiphilic PS‐b‐PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by 1H NMR and laser light scattering (LLS). The values of critical micelle concentration of PS‐b‐PNVP and the average aggregation number of PS‐b‐PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10–50 °C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5604–5615, 2008 相似文献
992.
多光子J-C模型的场熵的演化 总被引:5,自引:0,他引:5
研究了一个二能级原子与相干光场多光子相互作用下场熵演化的动力学特性 相似文献
993.
两同心球间旋转流动类Lorenz方程组的静态分歧 总被引:3,自引:0,他引:3
对同心球间旋转流动的N av ier-S tokes方程谱展开后进行三模态截断,讨论了所得到的类Lorenz型方程组的分歧问题.给出了静态奇异点的条件,并计算出解分支.首先,简要介绍了Lorenz方程组以及用Lorenz截断法讨论非线性问题的意义,其次,推导同心球间旋转流动N av ier-S tokes方程的流函数-涡度形式,最后,讨论同心球间旋转流动的类Lorenz型方程组的分歧问题. 相似文献
994.
本针对系统为受控AR模型,其参数估计采用随机梯度算法时,用鞅收敛定理的推广形式分析了它的收敛性,得到了参数估计误差一致有界的结果. 相似文献
995.
In this work,the well-known problem put forward by S N Bernstein in 1930 is studied in a deep step.An operator is constructed by revising double interpolation nodes.It is proved that the operator converges to arbitrary continuous functions uniformly and the convergence order is the best. 相似文献
996.
采用构造相容分布与非负上鞅的方法研究任意信源随机和相对熵密度的强极限定理,并由此得出若干任意信源,m阶马氏信源,无记忆信源的随机Shannon-Mcmillan定理.将已有的关于离散信源的结果加以推广. 相似文献
997.
A new numerical method called high accuracy time and space transform method (TSTM) is introduced to solve the advection–diffusion equation in an unbounded domain. By a spatial transform, the advection–diffusion equation in the unbounded domain Rn is converted to one on the bounded domain [?1, 1]n, and the Laplace transform is applied to eliminate time dependency. The consequent boundary value problem is solved by collocation on Chebyshev points. To face the well‐known computational challenge represented by the numerical inversion of the Laplace transform, Talbot's method is applied, consisting of numerically integrating the Bromwich integral on a special contour by means of trapezoidal or midpoint rules. Numerical experiments illustrate that TSTM has exponential rate in time and space. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
998.
In this paper, we present an existence result for weak efficient solution for the vector optimization problem. The result is stated for invex strongly compactly Lipschitz functions. 相似文献
999.
David A. Croydon 《Probability Theory and Related Fields》2008,140(1-2):207-238
In this article, we prove global and local (point-wise) volume and heat kernel bounds for the continuum random tree. We demonstrate
that there are almost–surely logarithmic global fluctuations and log–logarithmic local fluctuations in the volume of balls
of radius r about the leading order polynomial term as r → 0. We also show that the on-diagonal part of the heat kernel exhibits corresponding global and local fluctuations as t → 0 almost–surely. Finally, we prove that this quenched (almost–sure) behaviour contrasts with the local annealed (averaged
over all realisations of the tree) volume and heat kernel behaviour, which is smooth.
相似文献
1000.
A. I. Gerasimov V. N. Razzhevaikin 《Computational Mathematics and Mathematical Physics》2008,48(8):1406-1417
Mathematical parasite-host models are generalized to the case when the population members differ in susceptibility and contagiousness, there is an external source of infection, and the model parameters depend periodically (seasonally) on time. The model is proved to have a periodic solution that is unique and exponentially stable for sufficiently small periodic oscillations of the coefficients. 相似文献