全文获取类型
收费全文 | 14709篇 |
免费 | 1107篇 |
国内免费 | 1074篇 |
专业分类
化学 | 478篇 |
晶体学 | 13篇 |
力学 | 1481篇 |
综合类 | 122篇 |
数学 | 5800篇 |
物理学 | 2148篇 |
综合类 | 6848篇 |
出版年
2024年 | 32篇 |
2023年 | 140篇 |
2022年 | 173篇 |
2021年 | 193篇 |
2020年 | 314篇 |
2019年 | 302篇 |
2018年 | 282篇 |
2017年 | 375篇 |
2016年 | 357篇 |
2015年 | 363篇 |
2014年 | 672篇 |
2013年 | 1055篇 |
2012年 | 710篇 |
2011年 | 857篇 |
2010年 | 679篇 |
2009年 | 891篇 |
2008年 | 826篇 |
2007年 | 1042篇 |
2006年 | 969篇 |
2005年 | 864篇 |
2004年 | 737篇 |
2003年 | 719篇 |
2002年 | 573篇 |
2001年 | 523篇 |
2000年 | 489篇 |
1999年 | 465篇 |
1998年 | 358篇 |
1997年 | 295篇 |
1996年 | 289篇 |
1995年 | 196篇 |
1994年 | 223篇 |
1993年 | 154篇 |
1992年 | 146篇 |
1991年 | 137篇 |
1990年 | 94篇 |
1989年 | 87篇 |
1988年 | 68篇 |
1987年 | 61篇 |
1986年 | 26篇 |
1985年 | 36篇 |
1984年 | 30篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
11.
钟怀杰 《福建师范大学学报(自然科学版)》1993,9(3):10-14
讨论一般巴拿赫空间上非紧的黎斯算子存在问题,说明各经典巴拿赫空间上确有这种非平凡的黎斯算子,给出一类空间,其上的根算子理想与严格奇异算子理想是不重合的。 相似文献
12.
The estimation-valued property of B-valued asymptotic martingale 总被引:2,自引:0,他引:2
KONG Fanliang 《自然科学进展(英文版)》2006,16(7):773-776
In this paper, with the Doob decomposition of B-valued asymptotic martingale, we study the estimation-valued property of B-valued asymptotic martingale in Banach space B,which has the Radon-Nikodym Property and is dual-separable, and give a series of result and proof. 相似文献
13.
《厦门大学学报(自然科学版)》2002,(Z1)
This paper puts forward a new integrated design met ho d based on fuzzy matter-element optimization.On the based of analyzing the mod el of multi-objective fuzzy matter-element , the paper defines the m atter-element weightily and changes solving multi-objective fuzzy optimization into solving dependent function K(x) of the single-objective optimization according to the optimization criterion. The paper particularly describes the realization approach of GA process of multi -objective fuzzy matter-eleme... 相似文献
14.
基于广义混沌同步的数字图像隐藏方案 总被引:6,自引:3,他引:3
基于广义混沌同步理论,提出了一种适于网络图像传输的隐藏数字图像的安全通讯方案.构造了一个六维广义混沌同步系统作为新方案的加密器,理论分析和计算机模拟说明本方案具有较高的保真度和较强的抗破译能力. 相似文献
15.
Arthur W. Apter 《Mathematical Logic Quarterly》2006,52(5):457-463
We construct models for the level by level equivalence between strong compactness and supercompactness in which for κ the least supercompact cardinal and δ ≤ κ any cardinal which is either a strong cardinal or a measurable limit of strong cardinals, 2δ > δ + and δ is < 2δ supercompact. In these models, the structure of the class of supercompact cardinals can be arbitrary, and the size of the power set of κ can essentially be made as large as desired. This extends and generalizes [5, Theorem 2] and [4, Theorem 4]. We also sketch how our techniques can be used to establish a weak indestructibility result. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
A stage structured host-parasitoid model is derived and the equilibria studied. It is shown under what conditions the parasitoid controls an exponentially growing host in the sense that a coexistence equilibrium exists. Furthermore, for host populations whose inherent growth rate is not too large it is proved that in order to minimize the adult host equilibrium level it is necessary that the parasitoids attack only one of the larval stages. It is also proved in this case that the minimum adult host equilibrium level is attained when the parasitoids attack that larval stage which also maximizes the expected number of emerging adult parasitoid per larva at equilibrium. Numerical simulations tentatively indicate that the first conclusion remains in general valid for the model. However, numerical studies also show that it is not true in general that the optimal strategy will maximize the number of emerging adult parasitoid per larva at equilibrium. 相似文献
17.
程金发 《厦门大学学报(自然科学版)》2002,41(4):423-426
得到一阶差分方程:An 1-An+m∑i=1piAn-ki i∑j=1qjAn-lj=0解振动的充分必要条件,这里pi∈R,ki∈Z,qj∈R,ri∈{-1,0},i=1,2,…,m;j=1,2,…,l。这些结果包含并推广了相关文献的定理,而且更系统化。 相似文献
18.
颜晓敏 《西南民族学院学报(自然科学版)》1994,20(1):49-52
介绍用TP_(801)微机控制凝固点降低法测定分子量的有关原理和技术,与传统的用贝克曼温度计测△T方法相比,扩大了测量范围,提高了精密度,工作条件得到改善. 相似文献
19.
J. I. Ramos 《国际流体数值方法杂志》1991,12(9):881-894
Two domain-adaptive finite difference methods are presented and applied to study the dynamic response of incompressible, inviscid, axisymmetric liquid membranes subject to imposed sinusoidal pressure oscillations. Both finite difference methods map the time-dependent physical domain whose downstream boundary is unknown onto a fixed computational domain. The location of the unknown time-dependent downstream boundary of the physical domain is determined from the continuity equation and results in an integrodifferential equation which is non-linearly coupled with the partial differential equations which govern the conservation of mass and linear momentum and the radius of the liquid membrane. One of the finite difference methods solves the non-conservative form of the governing equations by means of a block implicit iterative method. This method possesses the property that the Jacobian matrix of the convection fluxes has an eigenvalue of algebraic multiplicity equal to four and of geometric multiplicity equal to one. The second finite difference procedure also uses a block implicit iterative method, but the governing equations are written in conservation law form and contain an axial velocity which is the difference between the physical axial velocity and the grid speed. It is shown that these methods yield almost identical results and are more accurate than the non-adaptive techniques presented in Part I. It is also shown that the actual value of the pressure coefficient determined from linear analyses can be exceeded without affecting the stability and convergence of liquid membranes if the liquid membranes are subjected to sinusoidal pressure variations of sufficiently high frequencies. 相似文献
20.
本文介绍了在水电工程规划设计时,如何利用三次自然样条插值函数在有限个方案的基础上自动生成无限多个方案,然后采用多目标综合决策模型在其中选择最优方案的一种方法.文中还给出了程序流程,并以某水电站正常蓄水位选择作为实例,对方法进行了验证,结果与专家决策完全吻合. 相似文献