全文获取类型
收费全文 | 4537篇 |
免费 | 162篇 |
国内免费 | 52篇 |
专业分类
化学 | 2921篇 |
晶体学 | 31篇 |
力学 | 154篇 |
综合类 | 2篇 |
数学 | 727篇 |
物理学 | 916篇 |
出版年
2023年 | 27篇 |
2022年 | 47篇 |
2021年 | 54篇 |
2020年 | 58篇 |
2019年 | 58篇 |
2018年 | 59篇 |
2017年 | 34篇 |
2016年 | 98篇 |
2015年 | 80篇 |
2014年 | 118篇 |
2013年 | 227篇 |
2012年 | 299篇 |
2011年 | 326篇 |
2010年 | 174篇 |
2009年 | 163篇 |
2008年 | 272篇 |
2007年 | 258篇 |
2006年 | 257篇 |
2005年 | 222篇 |
2004年 | 201篇 |
2003年 | 171篇 |
2002年 | 128篇 |
2001年 | 113篇 |
2000年 | 101篇 |
1999年 | 70篇 |
1998年 | 61篇 |
1997年 | 41篇 |
1996年 | 78篇 |
1995年 | 57篇 |
1994年 | 51篇 |
1993年 | 57篇 |
1992年 | 49篇 |
1991年 | 43篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 35篇 |
1987年 | 28篇 |
1986年 | 29篇 |
1985年 | 54篇 |
1984年 | 37篇 |
1983年 | 37篇 |
1982年 | 29篇 |
1981年 | 41篇 |
1980年 | 33篇 |
1979年 | 32篇 |
1978年 | 35篇 |
1977年 | 35篇 |
1975年 | 28篇 |
1974年 | 41篇 |
1973年 | 27篇 |
排序方式: 共有4751条查询结果,搜索用时 15 毫秒
11.
12.
We prove that directly reducible lattices and selfdual subdirectly irreducible lattices of locally finite length are determined by their sublattice-lattices. As a corollary we obtain that splitting varieties are closed under the isomorphism of sublattice-lattices iff they are selfdual. A class of selfdual non-closed varieties is given too. 相似文献
13.
A new method of using time-averaged digital speckle pattern interferometry for the quantitative measurement of vibration amplitude was developed. Signal processing techniques especially the Hilbert transformation for quantitative evaluation of the Bessel fringes obtained in time-averaged digital speckle pattern interferometry were explored. The quadrature signal after Hilbert transformation is equivalent to a 90° phase-shifted interferogram for a monotonically increasing or decreasing phase function. An algorithm was developed for Bessel fringe contrast enhancement and phase extraction. The techniques were tested numerically and experimentally. Sub-fringe quantification of the time-averaged vibration fringes is realised with the proposed method. Compared with the commonly used phase shift method which requires a minimum of two images for image processing, this method requires only one fringe pattern for data extraction. 相似文献
14.
Oblatum 4-VI-1990 &; 5-III-1991 相似文献
15.
In apparel industry, manufacturers developed standard allowed minutes (SAMs) databases on various manufacturing operations in order to facilitate better scheduling, while effective production schedules ensure smoothness of downstream operations. As apparel manufacturing environment is fuzzy and dynamic, rigid production schedules based on SAMs become futile in the presence of any uncertainty. In this paper, a fuzzification scheme is proposed to fuzzify the static standard time so as to incorporate some uncertainties, in terms of both job-specific and human related factors, into the fabric-cutting scheduling problem. A genetic optimisation procedure is also proposed to search for fault-tolerant schedules using genetic algorithms, such that makespan and scheduling uncertainties are minimised. Two sets of real production data were collected to validate the proposed method. Experimental results indicate that the genetically optimised fault-tolerant schedules not only improve the operation performance but also minimise the scheduling risks. 相似文献
16.
Wing-Sum Cheung Patricia J.Y. Wong 《Journal of Mathematical Analysis and Applications》2007,329(2):851-869
We consider a system of focal boundary value problems where the nonlinearities may be singular in the independent variable and may also be singular in the dependent arguments. Using Schauder fixed point theorem, we establish criteria such that the system of boundary value problems has at least one fixed-sign solution. 相似文献
17.
18.
19.
A polarization-insensitive 40-Gb/s time-division demultiplexer was demonstrated in a polarization-diversity loop configuration. The power penalty was measured to be 2.3 dB at a bit error rates of 10-9 for 10 Gb/s output signals. 相似文献
20.
This paper outlines the results of a study undertaken to investigate the nature of Community Operational Research (COR). The objective was to contact the people involved in COR through a series of personal interviews and a questionnaire survey, in order to clarify many of the issues that have emerged within the profession relating to the practice of OR within the community and voluntary sector. A total of 20 individuals were successfully contacted, and they have been responsible for at least two-thirds of the projects in the COR area. 相似文献