全文获取类型
收费全文 | 3520篇 |
免费 | 216篇 |
国内免费 | 235篇 |
专业分类
化学 | 1721篇 |
晶体学 | 43篇 |
力学 | 193篇 |
综合类 | 13篇 |
数学 | 867篇 |
物理学 | 695篇 |
无线电 | 439篇 |
出版年
2024年 | 3篇 |
2023年 | 33篇 |
2022年 | 84篇 |
2021年 | 85篇 |
2020年 | 75篇 |
2019年 | 74篇 |
2018年 | 72篇 |
2017年 | 76篇 |
2016年 | 73篇 |
2015年 | 79篇 |
2014年 | 91篇 |
2013年 | 161篇 |
2012年 | 161篇 |
2011年 | 245篇 |
2010年 | 234篇 |
2009年 | 363篇 |
2008年 | 312篇 |
2007年 | 190篇 |
2006年 | 239篇 |
2005年 | 185篇 |
2004年 | 188篇 |
2003年 | 150篇 |
2002年 | 166篇 |
2001年 | 87篇 |
2000年 | 63篇 |
1999年 | 66篇 |
1998年 | 61篇 |
1997年 | 50篇 |
1996年 | 38篇 |
1995年 | 38篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 36篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有3971条查询结果,搜索用时 15 毫秒
1.
Mark Webber 《Mathematical Methods in the Applied Sciences》2006,29(7):819-838
We investigate the influence of slip boundary conditions on the onset of Bénard convection in an infinite fluid layer. It is shown that the critical Rayleigh number is a decreasing function of the slip length, and therefore boundary slip is seen to have a destabilizing effect. Chebyshev‐tau and compound matrix formulations for solving the eigenvalue problem are presented. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
2.
Oracle9i数据库安全管理机制剖析 总被引:4,自引:0,他引:4
数据库安全和数据安全机制是数据库开发设计者目前必须考虑的问题之一。Oracle9i数据库管理系统在数据库安全方面为数据库管理员和应用开发者提供了很好的安全机制。文章从不同侧面和角度讨论Oracle9i数据库系统的安全管理机制,为实施更安全更灵活的数据库安全策略提出了全方位的技术思路。 相似文献
3.
Fundamental processes in long air gap discharges 总被引:2,自引:0,他引:2
I. Gallimberti G. Bacchiega Anne Bondiou-Clergerie Philippe Lalande 《Comptes Rendus Physique》2002,3(10):854
The development of atmospheric lightning is initiated and sustained by the formation in virgin air of ‘streamer corona’ and ‘leader’ discharges, very similar to those observed in laboratory long sparks. Therefore, the experimental and theoretical investigations of these laboratory discharges have become of large interest to improve the physical knowledge of the lightning process and to develop self-consistent models that could be applied to new protection concepts.In the present paper the fundamental processes of the subsequent phases of long air gap discharges are analyzed, from the first corona inception and development to the leader channel formation and propagation. For all these processes simulations models are discussed that have been essentially derived and simplified by the authors, in order to develop sequential time-dependent simulation of the laboratory breakdown, with both positive and negative voltages. The possibility of extending these models to the case of natural lightning is discussed in the companion paper, presented in this same volume. To cite this article: I. Gallimberti et al., C. R. Physique 3 (2002) 1335–1359. 相似文献
4.
5.
6.
The object of the present investigation is to introduce a new trigonometric method of summation which is both regular and
Fourier effective and determine its status with reference to other methods of summation (see §2-§4) and also give an application
of this method to determine the degree of approximation in a new Banach space of functions conceived as a generalized Holder
metric (see §5). 相似文献
7.
8.
Rong-Seng Chang Jin-Yi Sheu Ching-Huang Lin He-Chiang Liu 《Optics & Laser Technology》2003,35(1):43-47
A new approach based on the moiré theory and wavelet transform (WT) is proposed for measuring the micro-range distance between a charge-couple-device (CCD) camera and a two-dimensional reference grating. The micro-range distance is determined by measuring the pitch of the moiré pattern image, which is digitized by a CCD camera. A one-dimensional WT algorithm is applied to estimate the pitch of the moiré pattern. Experimental results prove that this technique is very efficient and highly accurate. The moiré range finder is an economic technique for measuring a micro-range distance. 相似文献
9.
We present a general risk model where the aggregate claims, as well as the premium function, evolve by jumps. This is achieved by incorporating a Lévy process into the model. This seeks to account for the discrete nature of claims and asset prices. We give several explicit examples of Lévy processes that can be used to drive a risk model. This allows us to incorporate aggregate claims and premium fluctuations in the same process. We discuss important features of such processes and their relevance to risk modeling. We also extend classical results on ruin probabilities to this model. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
10.
Huimin Xie Biao Li Robert Geer Bai Xu James Castracane 《Optics and Lasers in Engineering》2003,40(3):163-177
A focused ion beam (FIB) Moiré method is proposed to measure the in-plane deformation of object in a micrometer scale. The FIB Moiré is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of the FIB Moiré is described. The sensitivity and accuracy of deformation measurement are discussed in detail. Several specimen gratings with 0.14 and 0.20 μm spacing are used to generate FIB Moiré patterns. The FIB Moiré method is successfully used to measure the residual deformation in a micro-electro-mechanical system structure after removing the SiO2 sacrificial layer with a 5000 lines/mm grating. The results demonstrate the feasibility of this method. 相似文献