全文获取类型
收费全文 | 9017篇 |
免费 | 1252篇 |
国内免费 | 556篇 |
专业分类
化学 | 1534篇 |
晶体学 | 50篇 |
力学 | 837篇 |
综合类 | 161篇 |
数学 | 2815篇 |
物理学 | 2416篇 |
无线电 | 3012篇 |
出版年
2024年 | 34篇 |
2023年 | 93篇 |
2022年 | 189篇 |
2021年 | 223篇 |
2020年 | 288篇 |
2019年 | 251篇 |
2018年 | 241篇 |
2017年 | 282篇 |
2016年 | 361篇 |
2015年 | 346篇 |
2014年 | 504篇 |
2013年 | 730篇 |
2012年 | 560篇 |
2011年 | 584篇 |
2010年 | 468篇 |
2009年 | 539篇 |
2008年 | 546篇 |
2007年 | 588篇 |
2006年 | 525篇 |
2005年 | 465篇 |
2004年 | 404篇 |
2003年 | 375篇 |
2002年 | 329篇 |
2001年 | 277篇 |
2000年 | 275篇 |
1999年 | 202篇 |
1998年 | 179篇 |
1997年 | 196篇 |
1996年 | 122篇 |
1995年 | 110篇 |
1994年 | 104篇 |
1993年 | 67篇 |
1992年 | 66篇 |
1991年 | 54篇 |
1990年 | 46篇 |
1989年 | 31篇 |
1988年 | 30篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Profiling engineered data with robust mining methods continues attracting attention in knowledge engineering systems. The purpose of this article is to propose a simple technique that deals with non-linear multi-factorial multi-characteristic screening suitable for knowledge discovery studies. The method is designed to proactively seek and quantify significant information content in engineered mini-datasets. This is achieved by deploying replicated fractional-factorial sampling schemes. Compiled multi-response data are converted to a single master-response effectuated by a series of distribution-free transformations and multi-compressed data fusions. The resulting amalgamated master response is deciphered by non-linear multi-factorial stealth stochastics intended for saturated schemes. The stealth properties of our method target processing datasets which might be overwhelmed by a lack of knowledge about the nature of reference distributions at play. Stealth features are triggered to overcome restrictions regarding the data normality conformance, the effect sparsity assumption and the inherent collapse of the ‘unexplainable error’ connotation in saturated arrays. The technique is showcased by profiling four ordinary controlling factors that influence webpage content performance by collecting data from a commercial browser monitoring service on a large scale web host. The examined effects are: (1) the number of Cascading Style Sheets files, (2) the number of JavaScript files, (3) the number of Image files, and (4) the Domain Name System Aliasing. The webpage performance level was screened against three popular characteristics: (1) the time to first visual, (2) the total loading time, and (3) the customer satisfaction. Our robust multi-response data mining technique is elucidated for a ten-replicate run study dictated by an L9(34) orthogonal array scheme where any uncontrolled noise embedded contribution has not been necessarily excluded. 相似文献
3.
V. V. Sagaradze N. V. Kataeva V. A. Zavalishin K. A. Kozlov V. V. Makarov A. R. Kuznetsov 《哲学杂志》2020,100(14):1868-1879
ABSTRACT The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti. 相似文献
4.
5.
6.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
7.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献
8.
在社会转型期,面对日益激烈的市场竞争环境,如何制定民办高效发战战略,引导民办高效的可持续发展,是关系到民办高校兴衰的关键。本文主要从民办高校品牌战略入手,对社会转型及高等教育转型进行论述,并对如何加强民办高校品牌建设进行探讨。 相似文献
9.
Namyong Kim 《ETRI Journal》2006,28(2):155-161
In this paper, we introduce an escalator (ESC) algorithm based on the least squares (LS) criterion. The proposed algorithm is relatively insensitive to the eigenvalue spread ratio (ESR) of an input signal and has a faster convergence speed than the conventional ESC algorithms. This algorithm exploits the fast adaptation ability of least squares methods and the orthogonalization property of the ESC structure. From the simulation results, the proposed algorithm shows superior convergence performance. 相似文献
10.