全文获取类型
收费全文 | 38397篇 |
免费 | 356篇 |
国内免费 | 141篇 |
专业分类
化学 | 19682篇 |
晶体学 | 682篇 |
力学 | 1614篇 |
综合类 | 2篇 |
数学 | 3594篇 |
物理学 | 13320篇 |
出版年
2022年 | 293篇 |
2021年 | 341篇 |
2020年 | 315篇 |
2019年 | 313篇 |
2018年 | 518篇 |
2017年 | 448篇 |
2016年 | 715篇 |
2015年 | 408篇 |
2014年 | 717篇 |
2013年 | 1597篇 |
2012年 | 1592篇 |
2011年 | 2091篇 |
2010年 | 1403篇 |
2009年 | 1358篇 |
2008年 | 1712篇 |
2007年 | 1700篇 |
2006年 | 1579篇 |
2005年 | 1381篇 |
2004年 | 1261篇 |
2003年 | 1098篇 |
2002年 | 1025篇 |
2001年 | 1398篇 |
2000年 | 1026篇 |
1999年 | 815篇 |
1998年 | 620篇 |
1997年 | 589篇 |
1996年 | 519篇 |
1995年 | 479篇 |
1994年 | 455篇 |
1993年 | 400篇 |
1992年 | 469篇 |
1991年 | 477篇 |
1990年 | 461篇 |
1989年 | 427篇 |
1988年 | 450篇 |
1987年 | 433篇 |
1986年 | 378篇 |
1985年 | 444篇 |
1984年 | 472篇 |
1983年 | 346篇 |
1982年 | 386篇 |
1981年 | 377篇 |
1980年 | 320篇 |
1979年 | 400篇 |
1978年 | 379篇 |
1977年 | 396篇 |
1976年 | 393篇 |
1975年 | 344篇 |
1974年 | 326篇 |
1973年 | 339篇 |
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
1.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling. 相似文献
2.
3.
Saleh Z. M. Nasser H. Özkol E. Günöven M. Abak K. Canli S. Bek A. Turan R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting... 相似文献
4.
5.
6.
In view of immense importance of silylenes and the fact that their properties undergo significant changes on substitution with halogens, here, we have used B3LYP/6-311++G** level of theory to access the effects of 1–4 halogens (X = F, Cl, Br, and I) on four unprecedented sets of cyclopentasilylene-2,4-dienes; with the following formulas: SiC4H3X ( 1 X ), SiC4H2X2 ( 2 X ), SiC4HX3 ( 3 X ), and SiC4X4 ( 4 X ). In going down from F to I, the singlet (s)-triplet (t) energy gap (ΔEs-t, a possible indication of stability), and band gap (ΔEH-L) decrease while nucleophilicity (N), chemical potential (μ), and proton affinity (PA) increase. The overall order of N, μ, and PA for each X is 2 X > 1 X > 3 X > 4 X . Precedence of 2 X over 1 X is attributed to the symmetric cross conjugation in the former. The highest and lowest N are shown by 2 I and 4 F . The trend of divalent angle () for each X is 4 X > 1 X > 3 X > 2 X . The results show that in going from electron withdrawing groups (EWGs) to electron donating groups (EDGs), the ΔEs-t and ΔEH-L decrease while N, μ, and PA increase. Also, rather high N of our scrutinized silylenes may suggest new promising ligands in organometallic chemistry. 相似文献
7.
Palladium and molybdenum polycrystalline layers (clusters) have been deposited in a stainless steel UHV system onto a layer of alumina (Al2O3). This layer has been prepared by high temperature oxidation of an aluminium layer. The interaction of this system with nitrogen has been investigated at room temperature by an FEM technique. Under these conditions nitrogen spillover from molybdenum to palladium has been observed. 相似文献
8.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献
9.
10.