全文获取类型
收费全文 | 791篇 |
免费 | 31篇 |
国内免费 | 17篇 |
专业分类
化学 | 462篇 |
晶体学 | 20篇 |
力学 | 24篇 |
数学 | 173篇 |
物理学 | 160篇 |
出版年
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 12篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 31篇 |
2012年 | 42篇 |
2011年 | 57篇 |
2010年 | 28篇 |
2009年 | 36篇 |
2008年 | 35篇 |
2007年 | 40篇 |
2006年 | 36篇 |
2005年 | 40篇 |
2004年 | 22篇 |
2003年 | 27篇 |
2002年 | 39篇 |
2001年 | 8篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 15篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有839条查询结果,搜索用时 109 毫秒
1.
Queueing Systems - We study a quantum switch that distributes tripartite entangled states to sets of users. The entanglement switching process requires two steps: First, each user attempts to... 相似文献
2.
3.
Algorithm for Optimal Triangulations in Scattered Data Representation and Implementation 总被引:2,自引:0,他引:2
Scattered data collected at sample points may be used to determine simple functions to best fit the data. An ideal choice for these simple functions is bivariate splines. Triangulation of the sample points creates partitions over which the bivariate splines may be defined. But the optimality of the approximation is dependent on the choice of triangulation. An algorithm, referred to as an Edge Swapping Algorithm, has been developed to transform an arbitrary triangulation of the sample points into an optimal triangulation for representation of the scattered data. A Matlab package has been completed that implements this algorithm for any triangulation on a given set of sample points. 相似文献
4.
Don Hadwin K. J. Harrison J. A. Ward 《Proceedings of the American Mathematical Society》2006,134(8):2169-2178
We obtain necessary and sufficient conditions for the existence and the uniqueness of rank-one completions of a partial matrix, and we verify a conjecture of Hadwin and Larson concerning the nature of completely rank-nonincreasing linear functionals defined on pattern subspaces.
5.
Real-time liquid crystal television-based technique for simulating optical wavefront distortion due to atmospheric turbulence is presented and demonstrated. A liquid crystal television (LCTV) operating in the “phase mostly” mode was used as an array of spatially correlated phase delays. A movie of the arrays in motion was then generated and displayed on the LCTV. The turbulence simulation system was verified by passing a collimated and doubled diode pumped Nd:YVO4 laser beam (532 nm) through the transparent LCTV screen. The beam was then passed through a lens and the power spectra of the turbulence information carrying beam was detected as a measure of the far-field distribution. The same collimated laser beam, without the LCTV, was also transmitted down an open-air range and the power spectra detected as a measure of a real far-field distribution. Accepted turbulence parameters were measured for both arrangements and then compared. 相似文献
6.
A review of immiscibility data in binary borate and germanate systems was performed in order to compare miscibility gap consolute temperatures with ionic potentials and radii of their associated cations. The trends obtained demonstrate that a selective solution mechanism similar to the one identified for the binary silicate systems is present in the borate and germanate binaries. More importantly, the borate and germanate immiscibility data permitted the identification of a new group of cations depicting an immiscibility behaviour different from the ones identified in binary silicate systems. The new group involves highly polarizable cations possessing a lone pair of electrons. This lone pair of electrons together with oxygen bonded by strong covalent bonds to modifier cations provides efficient shielding to the cations' nuclei which considerably reduces the coulombic repulsions and produces miscibility gaps with very low consolute temperatures. A new group of cations having an homogenizing effect on melts (i.e. a capacity to make immiscible melts single phase) is thus reported. Experimental and spectroscopic data suggest that miscibility gaps associated with cations having a lone pair of electrons exist in binary silicate systems such as TlO1/2-SiO2, PbO-SiO2, SnO-SiO2 and Bi2O3-SiO2. The consolute temperature of their miscibility gaps is expected to be relatively low and metastable. 相似文献
7.
8.
An investigation has been carried out on the influence of degradation on various properties of commercial polyoxymethylene (POM) copolymer fittings in chlorinated cold water service lines. Scanning electron microscope (SEM) was used to document interior bulk morphological changes and typical defects. The various types of irregular cracks and pits were observed at the innerface of the samples. DSC and intrinsic viscosity determination were carried out for investigation of crystallinity and molecular weight changes. It was seen that the crystallinity of the POM increases at a much higher rate at the inner surface layers than the outer layer in the used samples. The FT-IR spectra of the new and used samples indicate the extent of degradation of the samples. 相似文献
9.
A universal cover is a set K with the property that each set of unit diameter is a subset of a congruent copy of K. It is shown that the smallest regular n-gon, for fixed n 4, which serves as an universal cover in R
2 is the smallest regular n-gon covering a Reuleaux triangle of unit width. 相似文献
10.
Gupta Rajinder K. Deobald Lee A. Crawford Don L. 《Applied biochemistry and biotechnology》1990,24(1):899-911
Applied Biochemistry and Biotechnology - Coal metabolizingPseudomonas cepacia DLC-07 was isolated from soil and shown to use soluble lignite coal as a carbon/energy source.Pseudomonas modified coal... 相似文献