全文获取类型
收费全文 | 22641篇 |
免费 | 3032篇 |
国内免费 | 1699篇 |
专业分类
化学 | 5942篇 |
晶体学 | 141篇 |
力学 | 1109篇 |
综合类 | 141篇 |
数学 | 1421篇 |
物理学 | 8673篇 |
无线电 | 9945篇 |
出版年
2024年 | 35篇 |
2023年 | 148篇 |
2022年 | 318篇 |
2021年 | 405篇 |
2020年 | 509篇 |
2019年 | 379篇 |
2018年 | 423篇 |
2017年 | 603篇 |
2016年 | 726篇 |
2015年 | 756篇 |
2014年 | 1289篇 |
2013年 | 1437篇 |
2012年 | 1458篇 |
2011年 | 1509篇 |
2010年 | 1118篇 |
2009年 | 1386篇 |
2008年 | 1578篇 |
2007年 | 1539篇 |
2006年 | 1442篇 |
2005年 | 1409篇 |
2004年 | 1333篇 |
2003年 | 1163篇 |
2002年 | 933篇 |
2001年 | 887篇 |
2000年 | 704篇 |
1999年 | 612篇 |
1998年 | 513篇 |
1997年 | 468篇 |
1996年 | 397篇 |
1995年 | 370篇 |
1994年 | 301篇 |
1993年 | 226篇 |
1992年 | 203篇 |
1991年 | 180篇 |
1990年 | 125篇 |
1989年 | 94篇 |
1988年 | 69篇 |
1987年 | 53篇 |
1986年 | 48篇 |
1985年 | 35篇 |
1984年 | 38篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
A. S. Belenky 《Mathematical and Computer Modelling》2002,36(11-13)
Two games of interacting between a coalition of players in a marketplace and the residual players acting there are discussed, along with two approaches to fair imputation of gains of coalitions in cooperative games that are based on the concepts of the Shapley vector and core of a cooperative game. In the first game, which is an antagonistic one, the residual players try to minimize the coalition's gain, whereas in the second game, which is a noncooperative one, they try to maximize their own gain as a coalition. A meaningful interpretation of possible relations between gains and Nash equilibrium strategies in both games considered as those played between a coalition of firms and its surrounding in a particular marketplace in the framework of two classes of n-person games is presented. A particular class of games of choosing partners and forming coalitions in which models of firms operating in the marketplace are those with linear constraints and utility functions being sums of linear and bilinear functions of two corresponding vector arguments is analyzed, and a set of maximin problems on polyhedral sets of connected strategies which the problem of choosing a coalition for a particular firm is reducible to are formulated based on the firm models of the considered kind. 相似文献
182.
Dieter Petrak 《Particle & Particle Systems Characterization》2002,19(6):391-400
The objective of this study was to compare the measuring results of a fiber‐optical probe based on a modified spatial filtering technique with given size distributions of different test powders and also with particle velocity values of laser Doppler measurements. Fiber‐optical spatial filtering velocimetry was modified by fiber‐optical spot scanning in order to determine simultaneously the size and the velocity of particles. The fiber‐optical probe system can be used as an in‐line measuring device for sizing of particles in different technical applications. Spherical test particles were narrow‐sized glass beads in the range 30–100 μm and irregularly shaped test particles were limestone particles in the range 10–600 μm. Particles were dispersed by a brush disperser and the measurements were carried out at a fixed position in a free particle‐laden air stream. Owing to the measurement of chord lengths and to the influence of diffraction and divergent angle, the probe results show differences from the given test particle sizes. Owing to the particle‐probe collisions, the mean velocity determined by the probe is smaller than the laser Doppler mean velocity. 相似文献
183.
184.
采用反应射频磁控溅射方法,在Si (100) 基片上制备了具有高c轴择优取向的ZnO薄膜.利用 原子力显微镜、透射电子显微镜、X射线衍射分析、拉曼光谱等表征技术,研究了沉积温度 对ZnO薄膜的表面形貌、晶粒尺度、应力状态等结晶性能的影响;通过沉积温度对透射光谱 和光致荧光光谱的影响,探讨了ZnO薄膜的结晶特性与光学性能之间的关系.研究结果显示, 在室温至500℃的范围内,ZnO薄膜的晶粒尺寸随沉积温度的增加而增加,在沉积温度为500 ℃时达到最大;当沉积温度为750℃时,ZnO薄膜的晶粒尺度有所减小;在室温至750℃的范 围内,薄膜中ZnO晶粒与Si基体之间均存在着相对固定的外延关系;在沉积温度低于500℃时 ,制备的ZnO薄膜处于压应变状态,而750℃时沉积的薄膜表现为张应变状态.沉积温度的不 同导致ZnO薄膜的折射率、消光系数、光学禁带宽度以及光致荧光特性的变化,沉积温度对 紫外光致荧光特性起着决定性的作用.此外,探讨了影响薄膜近紫外光致荧光发射的可能因 素.
关键词:
ZnO薄膜
表面形貌
微观结构
光学常数 相似文献
185.
The elastic constants of dilute alloys based on bcc metals have been calculated using the Green’s function method obtaining
explicit expressions for change in elastic constants in terms oft-matrix. The crystal impurity problem is discussed within an impurity model containing central and non-central force constant
changes extended up to second neighbours of the impurity. The effect of volume change on elastic constants and a contribution
from electron pressure term are considered. Numerical results for changes in three elastic moduli have been presented for
a number of dilute alloys based on Mo, Nb, W, Ta and V. 相似文献
186.
We investigate the change in the calculated value of asymptotic normalization constant (ANC) by the hyperspherical harmonics
expansion method with the inclusion of three nucleon force (3BF) in addition to two nucleon force. We see that ANC does not
change very much with the inclusion of 3BF indicating that the 3BF does not alter the asymptotic behaviours of HHE wavefunction
significantly. 相似文献
187.
1IntroductionAtpresent,astheerbiumdopedamplifiershavesucesfulybeenappliedtoopticalfiberlinks,thelonghaulhighbitrateofoptic... 相似文献
188.
本文研究Kerr型介质界面上弱非线性TM表面波的性质。数值计算表明了沿线性与非线性介质界面传播的TM表面波的自散焦特性。 相似文献
189.
YAG激光熔覆的研究现状与发展趋势 总被引:1,自引:1,他引:0
本文介绍了YAG激光熔覆的特点,并与CO2激光进行了比较,显示了YAG激光熔覆的优势和潜力。叙述了YAG激光熔覆的研究进展及其应用前景。 相似文献
190.
在重点说明影响传输光纤设计的主要问题的同时,简要介绍了各种升级方式所面临的主要技术挑战,并详细说明这些挑战对传输光纤提出的技术要求。 相似文献