全文获取类型
收费全文 | 5780篇 |
免费 | 622篇 |
国内免费 | 439篇 |
专业分类
化学 | 995篇 |
晶体学 | 38篇 |
力学 | 422篇 |
综合类 | 45篇 |
数学 | 1807篇 |
物理学 | 1178篇 |
综合类 | 2356篇 |
出版年
2024年 | 16篇 |
2023年 | 61篇 |
2022年 | 95篇 |
2021年 | 123篇 |
2020年 | 107篇 |
2019年 | 157篇 |
2018年 | 145篇 |
2017年 | 160篇 |
2016年 | 172篇 |
2015年 | 188篇 |
2014年 | 292篇 |
2013年 | 478篇 |
2012年 | 288篇 |
2011年 | 345篇 |
2010年 | 279篇 |
2009年 | 364篇 |
2008年 | 322篇 |
2007年 | 401篇 |
2006年 | 349篇 |
2005年 | 325篇 |
2004年 | 253篇 |
2003年 | 294篇 |
2002年 | 255篇 |
2001年 | 223篇 |
2000年 | 174篇 |
1999年 | 131篇 |
1998年 | 131篇 |
1997年 | 126篇 |
1996年 | 107篇 |
1995年 | 87篇 |
1994年 | 65篇 |
1993年 | 48篇 |
1992年 | 60篇 |
1991年 | 47篇 |
1990年 | 40篇 |
1989年 | 34篇 |
1988年 | 28篇 |
1987年 | 23篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1971年 | 1篇 |
1957年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有6841条查询结果,搜索用时 15 毫秒
1.
ON A PAIR OF NON-ISOMETRIC ISOSPECTRAL DOMAINS WITH FRACTAL BOUNDARIES AND THE WEYL-BERRY CONJECTURE
ONAPAIROFNONISOMETRICISOSPECTRALDOMAINSWITHFRACTALBOUNDARIESANDTHEWEYLBERRYCONJECTURESLEEMAN,B.D.CHENHUAManuscriptrec... 相似文献
2.
李林功 《河南师范大学学报(自然科学版)》1995,23(3):92-93
本文着重描述在数据转换过程中如何把数据信息按区域进行细分,以弄清数据信息的性质,进而确定一个最优数据通路,建立高效应用系统。 相似文献
3.
This paper gives some global and uniform convergence estimates for a class of subspace correction (based on space decomposition) iterative methods applied to some unconstrained convex optimization problems. Some multigrid and domain decomposition methods are also discussed as special examples for solving some nonlinear elliptic boundary value problems.
4.
YBa2Cu3O7-x (YBCO) bulk is one of the most important high temperature superconducting materials for magnetic levitation applications, because it has a high magnetic irreversibility field Hirr at liquid nitrogen temperature, and can grow into large grains. The levitation force of YBCO bulk is proportional to the critical current density (Jc) and grain radius (r)[1], so higher Jc and r are appreciated for YBCO bulks to achieve higher levitation force. Now single-domain YBCO bulks up to s… 相似文献
5.
Keye Martin 《Applied Categorical Structures》2003,11(1):27-40
We introduce the triangle inequality for measurement. This is a property that when satisfied by a measurement enables one to construct a metric on the set of elements with measure zero that yields the relative Scott topology. The naturality of this construction permits a categorical solution to the model problem in domain theory for locally compact metric spaces. The first time such a solution has been achieved. 相似文献
6.
Substructuring preconditioners for saddle-point problems arising from Maxwell's equations in three dimensions 总被引:1,自引:0,他引:1
This paper is concerned with the saddle-point problems arising from edge element discretizations of Maxwell's equations in a general three dimensional nonconvex polyhedral domain. A new augmented technique is first introduced to transform the problems into equivalent augmented saddle-point systems so that they can be solved by some existing preconditioned iterative methods. Then some substructuring preconditioners are proposed, with very simple coarse solvers, for the augmented saddle-point systems. With the preconditioners, the condition numbers of the preconditioned systems are nearly optimal; namely, they grow only as the logarithm of the ratio between the subdomain diameter and the finite element mesh size.
7.
8.
详细介绍了双光头同步控制原理.对采集的伺服模块聚焦误差跟踪信号及共焦模块读写光头的聚焦线圈驱动信号进行了频域分析,并以此两路信号作为系统输入输出,分别对三种参数模型进行参数优化.根据3种模型的频率响应及阶跃响应,选择双光头同步控制过程的参数模型为[450]阶的ARX模型.实测曲线与模型仿真结果符合度(fit)为78.0259%. 相似文献
9.
A synthetic form of the mineral hewettite was prepared via a new route in aqueous medium, starting either from the crystalline compound Li1.1V3O8, or from its amorphous precursor. The anhydrous, crystalline derivative Ca0.5V3O8 was obtained by heating the synthetic hewettite at 250°C under dynamic vacuum. The diffraction studies show that the 2D structure of Ca0.5V3O8 involves the same V3O8 layers as in the hewettite or in Li1+αV3O8. The stacking of the layers is similar to that in the metahewettite. A structural model is proposed, where the Ca2+ ions occupy octahedral sites in the interlayer space. The electrochemical behavior of Ca0.5V3O8 vs. lithium insertion is presented. It is original and reveals particularly good performances in terms of stability during cycling at C/5 rate. The homologues obtained with Mg or Ba, instead of Ca, are briefly presented. 相似文献
10.
Tae Young Kim Dong Myung Kim Won Jung Kim Tae Hee Lee Kwang S. Suh 《Journal of Polymer Science.Polymer Physics》2004,42(15):2813-2820
The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004 相似文献