全文获取类型
收费全文 | 13046篇 |
免费 | 1174篇 |
国内免费 | 1518篇 |
专业分类
化学 | 795篇 |
晶体学 | 16篇 |
力学 | 800篇 |
综合类 | 338篇 |
数学 | 11462篇 |
物理学 | 2327篇 |
出版年
2024年 | 20篇 |
2023年 | 143篇 |
2022年 | 182篇 |
2021年 | 235篇 |
2020年 | 267篇 |
2019年 | 330篇 |
2018年 | 298篇 |
2017年 | 361篇 |
2016年 | 388篇 |
2015年 | 301篇 |
2014年 | 600篇 |
2013年 | 961篇 |
2012年 | 533篇 |
2011年 | 749篇 |
2010年 | 690篇 |
2009年 | 921篇 |
2008年 | 1002篇 |
2007年 | 1031篇 |
2006年 | 831篇 |
2005年 | 754篇 |
2004年 | 578篇 |
2003年 | 646篇 |
2002年 | 570篇 |
2001年 | 457篇 |
2000年 | 500篇 |
1999年 | 447篇 |
1998年 | 405篇 |
1997年 | 340篇 |
1996年 | 255篇 |
1995年 | 149篇 |
1994年 | 149篇 |
1993年 | 88篇 |
1992年 | 67篇 |
1991年 | 63篇 |
1990年 | 53篇 |
1989年 | 38篇 |
1988年 | 32篇 |
1987年 | 29篇 |
1986年 | 15篇 |
1985年 | 48篇 |
1984年 | 39篇 |
1983年 | 19篇 |
1982年 | 30篇 |
1981年 | 19篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
131.
132.
在混凝土层析成像中,为了提高反演的准确性和计算效率,针对共轭梯度算法提出一种加权算法——概率加权共轭梯度算法.新算法不同于常规的加权算法,权重是加在成像单元上而不是方程上.为取得较好的权重因子和较好的迭代初始值,采用IART算法的权重和迭代初始值的选取方法.模拟算例和混凝土试验均表明这种加权算法的可行性. 相似文献
133.
Ambar Sengupta 《Journal of Geometry and Physics》1998,28(3-4):209-254
All the connected components of the moduli space of flat connections on SU (2) and SO (3) (trivial and non-trivial) bundles over closed oriented surfaces are determined. The symplectic structure and volumes of the non-maximal strata of the moduli space are also determined. 相似文献
134.
According to the concept of the recognized visual space of illumination (RVSI) the lightness of an object surface is perceived in relation to its conceptualized size. To prove this proposition the lightness of gray test patches was judged when they were located at various positions inside an illuminated space composed of two rooms in the depth direction from a subject. No retinal image arrangement was changed in the test patch and its immediate surroundings, but the front room had walls, floors and furniture lower in lightness by the amount of N1.5 than the back room to make the RVSI of the former smaller despite the illuminance in the entire space being the same. The results showed that the apparent lightness of the patches was perceived higher by amount of about 13 in L units for the N4 test patch and about 20 for N6 when the patches were located in the front room, in accordance with the prediction. It was stressed that the experiment of lightness judgment should be conducted in a three dimensional space rather than two dimensional plane as done by several investigators. 相似文献
135.
微重力条件下晶体生长过程的实时观察 总被引:1,自引:0,他引:1
从材料科学的微重力效应和晶体生长基本过程等两个方面出发,阐明了一种新的生长技术(晶体生长过程的光学实时观察法)的必要性,并介绍了空间高温实时观察装置的基本特性.在我国的科学技术探测卫星上,该装置进行了搭载实验,并首次清楚地观察到了空间溶质扩散效应和高温溶液的表面张力对流图像. 相似文献
136.
137.
We investigate finite lattice approximations to the Wilson renormalization group in models of unconstrained spins. We discuss first the properties of the renormalization group transformation (RGT) that control the accuracy of this type of approximation and explain different methods and techniques to practically identify them. We also discuss how to determine the anomalous dimension of the field. We apply our considerations to a linear sigma model in two dimensions in the domain of attraction of the Ising fixed point using a Bell–Wilson RGT. We are able to identify optimal RGTs which allow accurate computations of quantities such as critical exponents, fixed-point couplings and eigenvectors with modest statistics. We finally discuss the advantages and limitations of this type of approach. 相似文献
138.
A recent analysis of the experimental data on some physical phenomena ruled by the four fundamental interactions (electromagnetic, weak, strong and gravitational) seems to show the possibility of describing such interactions in terms of a deformation of the usual Minkowski spacetime, with a metric whose coefficients do depend on the energy of the process considered. In this paper, we show that such results can be accounted for in terms of a Kaluza-Klein-like scheme, based on a five-dimensional Riemannian space in which energy plays the role of the fifth dimension. The corresponding five-dimensional Einstein equations in vacuum are solved in some cases of physical relevance and it is shown that all the phenomenological metrics describing the four fundamental forces are recovered as special cases of the classes of solutions found. Possible developments of the formalism are also briefly outlined. 相似文献
139.
A passive neutron dosemeter based on nuclear track detectors and TLD's was used in 1995 and 1997 on the MIR station and in Space Shuttle flights to MIR. As it is equipped with neutron converters and shieldings of different types the track detector system allows the neutron dose equivalent to be determined in rough energy intervals. The results of the measurements on the MIR station and in the Space Shuttle flights are presented and the influence of charged particles in the complex mixed radiation field in space is discussed. Improvements are possible by means of a new active neutron dosemeter which is under development at the PTB. First measurements with a prototype in the high-energy reference fields at CERN are presented and discussed. 相似文献
140.
The globally supported order 0 irreducible unitary representations of gauge groups are known as multiplicative integrals, and arise as cocycle representations. We generalize them to the setting of gauge supergroups. 相似文献