全文获取类型
收费全文 | 1764篇 |
免费 | 256篇 |
国内免费 | 175篇 |
专业分类
化学 | 136篇 |
晶体学 | 3篇 |
力学 | 161篇 |
综合类 | 48篇 |
数学 | 1278篇 |
物理学 | 569篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 16篇 |
2021年 | 41篇 |
2020年 | 40篇 |
2019年 | 46篇 |
2018年 | 47篇 |
2017年 | 50篇 |
2016年 | 66篇 |
2015年 | 52篇 |
2014年 | 92篇 |
2013年 | 106篇 |
2012年 | 82篇 |
2011年 | 91篇 |
2010年 | 80篇 |
2009年 | 109篇 |
2008年 | 127篇 |
2007年 | 106篇 |
2006年 | 121篇 |
2005年 | 92篇 |
2004年 | 77篇 |
2003年 | 87篇 |
2002年 | 88篇 |
2001年 | 79篇 |
2000年 | 74篇 |
1999年 | 68篇 |
1998年 | 67篇 |
1997年 | 48篇 |
1996年 | 43篇 |
1995年 | 34篇 |
1994年 | 17篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1970年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有2195条查询结果,搜索用时 15 毫秒
91.
Ronny Nahum 《Proceedings of the American Mathematical Society》2001,129(7):1995-1999
For every normed space , we note its closed unit ball and unit sphere by and , respectively. Let and be normed spaces such that is Lipschitz homeomorphic to , and is Lipschitz homeomorphic to .
We prove that the following are equivalent:
1. is Lipschitz homeomorphic to .
2. is Lipschitz homeomorphic to .
3. is Lipschitz homeomorphic to .
This result holds also in the uniform category, except (2 or 3) 1 which is known to be false.
92.
A set X of boundary points of a (possibly unbounded) convex body KE
d illuminating K from within is called primitive if no proper subset of X still illuminates K from within. We prove that for such a primitive set X of an unbounded, convex set KE
d (distinct from a cone) one has X=2 if d=2, X6 if d=3, and that there is no upper bound for X if d4. 相似文献
93.
M. M. Cavalcanti V. N. Domingos Cavalcanti J. A. Soriano L. A. Medeiros 《Southeast Asian Bulletin of Mathematics》2000,24(2):183-199
In this paper, we study a hyperbolic model based on the equation
with nonlinear boundary conditions given by
.We prove the existence and the uniqueness of global solutions. Also, we obtain the uniform decay of the energy without control of its derivative sign.AMS Subject Classification (2000), 35L05, 35L70, 35B40 相似文献
94.
Random orders on
invariant under permutations are called exchangeable. The compact and convex set of all random total orders is shown to be a Bauer simplex whose set of extreme points, the socalled totally ordered paintbox processes, is homeomorphically parametrized by almost uniform distributions on the unit interval, i.e. by probability measures w on [0, 1] whose distribution functions are w-almost surely the identity. 相似文献
95.
M. G. Charalambous 《Applied Categorical Structures》2000,8(4):639-648
We prove results establishing sufficient conditions for the sum of two nearness frames to have enough Cauchy filters. From these results and the fact that, in the category of strong nearness frames having enough Cauchy filters and uniform frame maps, complete spatial frames form a coreflective subcategory, follow a variety of results where the open-sets contravariant functor from topological spaces to frames transforms products into sums and inverse limits into direct limits. 相似文献
96.
Gerhard Preuß 《Applied Categorical Structures》2000,8(3):463-474
Semiuniform convergence spaces form a common generalization of filter spaces (including symmetric convergence spaces [and thus symmetric topological spaces] as well as Cauchy spaces) and uniform limit spaces (including uniform spaces) with many convenient properties such as cartesian closedness, hereditariness and the fact that products of quotients are quotients. Here, for each semiuniform convergence space a completion is constructed, called the simple completion. This one generalizes Császár's -completion of filter spaces. Thus, filter spaces are characterized as subspaces of convergence spaces. Furthermore, Wyler's completion of separated uniform limit spaces can be easily derived from the simple completion. 相似文献
97.
采用同时具有三角函数良好逼近特性和小波多分辨率与局部特性的Hermite插值型三角小波,基于二维张量积三角小波,推导了求解各种不同边界条件下的矩形弹性薄板的弯曲、振动和屈曲问题的统一列式,同时给出了两种提高计算精度的方法一升阶法和多分辨率法。数值算例表明,三角小波法求解弹性薄板的弯曲、振动和屈曲问题时,能方便地处理各类边界条件,计算效果良好;自振特性分析更具优势,升阶法和多分辨率法能有效地提高分析精度。 相似文献
98.
我们考虑平行机排序问题中的这样一类:机器两台,类型一样,但效率不同.其中n个工件在第一台机器上的加工时间分别为p1,p2,…,Pn,在第二台机器上的加工时间分别为αρ1,αρ2,…,αρn,其中0<α≤1.每台机器上的工件总数不受限制.n个工件的权分别为w1,w2,…,wn,我们的目标是如何在这两台机器上安排这n个工件以及如何确定每台机器上工件加工的先后顺序,使得这n个工件的完工时间的总权和 达到最小.该问题记为 .对于这个问题,我们给出一个1.1755近似算法. 相似文献
99.
以苯胺二聚体(N-phenyl-p-phenylenediamine)为起始单体,在1 mol·L-1高氯酸水-乙腈混合液中,玻碳电极表面电化学制备聚苯胺. 实验结果表明,苯胺二聚体单体的聚合电位比苯胺单体的低约0.2 V,并且其聚合物具有更高的形貌可控性. 苯胺二聚体单体浓度分别为1、5和10 mmol·L-1时,采用分步恒电流法可分别制备出形貌均一的聚苯胺纳米粒子(粒径30 nm)、超长的纳米线(> 5 μm 直径50 nm)和大面积纳米片(4 μm × 2 μm × 30 nm). 相似文献
100.
Using spatially modulated illumination (SMI) light microscopy it is possible to measure the sizes of fluorescent structures that have an extension far below the conventional optical resolution limit (“subresolution size”). Presently, the sizes are determined as the object extension along the optical axis of the SMI microscope. For this, however, “a priori” assumptions on the fluorochrome distribution (“shape”) within the examined fluorescent structure have to be made. Usually it is assumed that the fluorochrome follows a Gauss-distribution or a spherical distribution. In this report we overcome the necessity to make an assumption on the shape of the fluorochrome distribution. We introduce two new experimentally obtained parameters which allow the determination of a shape measure to describe the spatial distribution of the fluorescent dye. This becomes possible by independent measurements with different excitation wavelengths. As an example, we present shape parameter measurements on individual fluorescent microspheres with a nominal geometrical diameter (“size”) of 190 nm. In the case investigated, the experimental shape correlated well with a homogeneous fluorochrome distribution (“spherical shape”) but not with a variety of other “shapes”. 相似文献