全文获取类型
收费全文 | 6376篇 |
免费 | 521篇 |
国内免费 | 145篇 |
专业分类
化学 | 953篇 |
晶体学 | 35篇 |
力学 | 142篇 |
综合类 | 121篇 |
数学 | 297篇 |
物理学 | 1042篇 |
无线电 | 4452篇 |
出版年
2024年 | 6篇 |
2023年 | 41篇 |
2022年 | 75篇 |
2021年 | 173篇 |
2020年 | 194篇 |
2019年 | 79篇 |
2018年 | 81篇 |
2017年 | 189篇 |
2016年 | 223篇 |
2015年 | 234篇 |
2014年 | 367篇 |
2013年 | 383篇 |
2012年 | 360篇 |
2011年 | 357篇 |
2010年 | 250篇 |
2009年 | 262篇 |
2008年 | 362篇 |
2007年 | 388篇 |
2006年 | 366篇 |
2005年 | 350篇 |
2004年 | 343篇 |
2003年 | 325篇 |
2002年 | 259篇 |
2001年 | 233篇 |
2000年 | 201篇 |
1999年 | 131篇 |
1998年 | 142篇 |
1997年 | 117篇 |
1996年 | 126篇 |
1995年 | 90篇 |
1994年 | 81篇 |
1993年 | 51篇 |
1992年 | 29篇 |
1991年 | 32篇 |
1990年 | 21篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1976年 | 4篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有7042条查询结果,搜索用时 20 毫秒
31.
32.
两个非线性方程的准确解 总被引:3,自引:0,他引:3
借助于计算机代数系统Mathematica利用直接代数方法获得了两个有数学物理意义的非线性耗散-色散方程的准确解,这种方法也适用于高维非线性方程。 相似文献
33.
34.
微机在应变测量中的应用,采用上位机和下位机组合方式.上位机为一台IBM-PC/XT微机,用于对数据进行后处理.下位机以Z80-CPU为控制器,由传感器、转换器、接口及外设等组成数据采集器,实施对应变、压力和位移等参数的采集、显示和打印(即数据的预处理).上位机和下位机之间的数据传输,采用串行的方式,通过RS-232接口完成.本文主要以应变的采集处理为例,介绍系统功能、硬件配置及软件设计. 相似文献
35.
36.
To provide responsive information services in a ubiquitous computing environment, service software and system development are indispensable. A component-based ubiquitous information system with a JAIN (Java APIs for Integrated Networks) platform to achieve seamless transmissions and reach-everywhere communications was designed in our research. In this development, numerous ubiquitous service modules were identified: location management, roaming, mobile IP and WAP networking. These component-based network modules were constructed using a component composition language with component specification and interface definition, running on top of a distributed service architecture using a JAIN platform to distribute the ubiquitous information services to mobile users. Two applications, Wireless-Application-Protocol (WAP) Mail and Video-on-Demand (VoD) services, show that the JAIN-like platform with the developed networking components effectively fills the gap for application developers between mobile appliances and various kinds of ubiquitous information services. 相似文献
37.
38.
An implementation for a fast public-key cryptosystem 总被引:9,自引:0,他引:9
In this paper we examine the development of a high-speed implementation of a system to perform exponentiation in fields of the form GF(2
n
). For sufficiently large n, this device has applications in public-key cryptography. The selection of representation and observations on the structure of multiplication have led to the development of an architecture which is of low complexity and high speed. A VLSI implementation has being fabricated with measured throughput for exponentiation for cryptographic purposes of approximately 300 kilobits per second. 相似文献
39.
Andrzej Kaim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(2):232-241
The competitiveness of the combination and disproportionation reactions between a 1‐phenylpropyl radical, standing for a growing polystyryl macroradical, and a 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) radical in the nitroxide‐mediated free‐radical polymerization of styrene was quantitatively evaluated by the study of the transition geometry and the potential energy profiles for the competing reactions with the use of quantum‐mechanical calculations at the density functional theory (DFT) UB3‐LYP/6‐311+G(3df, 2p)//(unrestricted) Austin Model 1 level of theory. The search for transition geometries resulted in six and two transition structures for the radical combination and disproportionation reactions, respectively. The former transition structures, mainly differing in the out‐of‐plane angle of the N? O bond in the transition structure TEMPO molecule, were correlated with the activation energy, which was determined to be in the range of 8.4–19.4 kcal mol?1 from a single‐point calculation at the DFT UB3‐LYP/6‐311+G(3df, 2p)//unrestricted Austin Model 1 level. The calculated activation energy for the disproportionation reaction was less favorable by a value of more than 30 kcal mol?1 in comparison with that for the combination reaction. The approximate barrier difference for the TEMPO addition and disproportionation reaction was slightly smaller for the styrene polymerization system than for the acrylonitrile polymerization system, thus indicating that a β‐proton abstraction through a TEMPO radical from the polymer backbone could diminish control over the radical polymerization of styrene with the nitroxide even more than in the latter system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 232–241, 2007 相似文献
40.
宁波城市设计的若干思考与建议 总被引:1,自引:0,他引:1
张柳燕 《宁波大学学报(理工版)》2004,17(2):166-169
通过探讨城市设计概念的形成过程和历史积淀,阐明其在城市建设中的意义,并运用城市设计的理论与分析方法,针对目前宁波城市大规模的规划、设计、改造现象,提出若干思考与建议. 相似文献