全文获取类型
收费全文 | 333088篇 |
免费 | 24022篇 |
国内免费 | 12554篇 |
专业分类
电工技术 | 17913篇 |
技术理论 | 56篇 |
综合类 | 19688篇 |
化学工业 | 56548篇 |
金属工艺 | 18546篇 |
机械仪表 | 21177篇 |
建筑科学 | 25728篇 |
矿业工程 | 10964篇 |
能源动力 | 9766篇 |
轻工业 | 18648篇 |
水利工程 | 5254篇 |
石油天然气 | 22986篇 |
武器工业 | 2602篇 |
无线电 | 36647篇 |
一般工业技术 | 39803篇 |
冶金工业 | 18380篇 |
原子能技术 | 3216篇 |
自动化技术 | 41742篇 |
出版年
2024年 | 1290篇 |
2023年 | 5212篇 |
2022年 | 8878篇 |
2021年 | 12552篇 |
2020年 | 9824篇 |
2019年 | 8013篇 |
2018年 | 9203篇 |
2017年 | 10377篇 |
2016年 | 9280篇 |
2015年 | 12219篇 |
2014年 | 15874篇 |
2013年 | 19187篇 |
2012年 | 20171篇 |
2011年 | 22446篇 |
2010年 | 19205篇 |
2009年 | 18330篇 |
2008年 | 17980篇 |
2007年 | 17399篇 |
2006年 | 18283篇 |
2005年 | 16130篇 |
2004年 | 10346篇 |
2003年 | 9131篇 |
2002年 | 8135篇 |
2001年 | 7474篇 |
2000年 | 8006篇 |
1999年 | 9657篇 |
1998年 | 8156篇 |
1997年 | 6770篇 |
1996年 | 6363篇 |
1995年 | 5340篇 |
1994年 | 4380篇 |
1993年 | 3089篇 |
1992年 | 2493篇 |
1991年 | 1962篇 |
1990年 | 1504篇 |
1989年 | 1232篇 |
1988年 | 1019篇 |
1987年 | 681篇 |
1986年 | 535篇 |
1985年 | 342篇 |
1984年 | 243篇 |
1983年 | 204篇 |
1982年 | 196篇 |
1981年 | 129篇 |
1980年 | 130篇 |
1979年 | 67篇 |
1978年 | 33篇 |
1977年 | 38篇 |
1976年 | 55篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
On chaotic simulated annealing 总被引:25,自引:0,他引:25
Chen and Aihara (1995) proposed a chaotic simulated annealing approach to solving optimization problems. By adding a negative self coupling to a network model proposed earlier by Aihara et al. and gradually removing this negative self-coupling, they used the transient chaos for searching and self-organizing, thereby achieving great improvement over other neural-network approaches to optimization problems with or without simulated annealing. In this paper we suggest a new approach to chaotic simulated annealing with guaranteed convergence and minimization of the energy function by gradually reducing the time step in the Euler approximation of the differential equations that describe the continuous Hopfield neural network. This approach eliminates the need to carefully select other system parameters. We also generalize the convergence theorems of Chen and Aihara to arbitrarily increasing neuronal input-output functions and to less restrictive and yet more compact forms. 相似文献
992.
Quanbo Zou Zhimin Tan Zhenfeng Wang Jiangtao Pang Xin Qian Qingxin Zhang Rongming Lin Sung Yi Haiqing Gong Litian Liu Zhijian Li 《Journal of microelectromechanical systems》1998,7(2):224-234
A novel principle “electret” microphone, i.e., floating electrode electret microphone, is proposed and implemented in this study. Single-chip fabrication and corrugation technique are used in the design and fabrication of the microphone. The floating electrode is encapsulated by highly insulated materials to ensure that there is no electric-leakage passage between the floating electrode and the electrodes of the microphone. Net-free electronic charges (not “bonded” charges as in traditional electret) in the floating electrode can excite the electric field, which is similar to that of the traditional electret. The floating electrode can be easily charged by use of the “hot” electron technique, available using the avalanche breakdown of the p+-n junction. Therefore, the electret microphone is rechargeable, which can greatly increase the lifetime of the device. The preamplifier has been on-chip integrated in a junction-field-effect transistor (JFET) source-follower type with resistors by use of ion implantation. Electret charges are banded in a deep potential trap, thus, this microphone can operate at a high temperature (as high as 300°C) and has high stability and reliability. Experiments show that the prototype has a 3-mV/Pa sensitivity and a larger than 21-kHz frequency bandwidth in a 1 mm ×1-mm diaphragm area. Microphone performance can be further improved by optimized process and design. The fabrication is completely integrated-circuit (IC) compatible, hence, the microphone shows promise in integrated acoustic systems 相似文献
993.
本文介绍了IC卡处理系统的基本组成,详述了一种IC卡处理系统的软硬件实现方法,说明了I^2C总线在系统中的应用。 相似文献
994.
本文将虚拟仪器技术与光频转换器件TSL230B相结合,设计新型浑浊度数字化测试仪.阐述该系统的工作原理、硬件构成及软件设计方案;实现浑浊度的自动在线测量.实验结果表明,该仪器数据处理能力强,图形化显示直观,保存与打印结果方便,测量的重复性好,精确度高. 相似文献
995.
本文分析了发电企业生产项目招标的现状、特点以及存在的问题,提出了完善和改进发电企业生产项目招标管理的一些措施,从而建立科学合理、规范的监督制度与运作程序,保证项目质量,提高经济效益。 相似文献
996.
The problem of stabilizing multiple independent linear systems sharing one conmmon network cable is presented and solved. Both the quanfization and time sequencing are studied in the field of control over networks by providing the formulated stabilizing sufficient condition which illustrates the relationship between the system instability, quanfization and time sequencing, and the data rate is also presented in temps of the quanfization and time sequencing. A numerical example is given to illustrate the result. 相似文献
997.
998.
999.
The Internet and World Wide Web offer an additional channel for consumers to find, select, and buy products. However, unlike shopping in the traditional store, consumers have no direct contact with human clerks to get the required information in the electronic store. The objective of this paper is to propose a fuzzy constraint satisfaction approach to help buyers find fully satisfactory or replacement products in electronic shopping. For the buyer who can give precise product requirements, the proposed approach can generate product-ranking lists based on the satisfaction degrees of each product to the given requirements. For the buyer who may not input accurate requirements, a similarity analysis approach is proposed to assess buyer requirements automatically during his browsing process. The proposed approach could help buyers find the preferred products on the top of the ranking list without further searching the remaining pages. The experimental results show the applicability of the proposed approach for electronic shopping assistance. 相似文献
1000.
Fei-Yue Wang Mingkuan Liu 《Robotics & Automation Magazine, IEEE》2004,11(1):59-69
Chip scale packaging (CSP) is emerging as a major player within the semiconductor packaging market. Processing in the back-end requires optimizing the use of intermediate carrier configurations such as tape-in-carrier and strip-based substrates. This optimization of carrier configurations must occur in all processes related to CSP assembly, including die attach, wire bond, encapsulation, ball attach, laser mark, singulate, inspect, and test. CSP is considered an SMT and, as such, can be processed using existing lines. However, CSP is different from SMT and has its own assembly problems. One of the critical problems is that, with thinner package profile requirement, thinner substrate is necessary. Another important problem that should be considered is the failure of solder joints because of the coefficient of thermal expansion mismatch among the substrate, lead packages, and the board when the thermal load is severe. To address this point, several studies using moire interferometry have been conducted to measure thermal deformations that accumulate during thermal cycles. 相似文献