全文获取类型
收费全文 | 20498篇 |
免费 | 704篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 215篇 |
综合类 | 20篇 |
化学工业 | 3766篇 |
金属工艺 | 322篇 |
机械仪表 | 404篇 |
建筑科学 | 1005篇 |
矿业工程 | 49篇 |
能源动力 | 501篇 |
轻工业 | 1675篇 |
水利工程 | 120篇 |
石油天然气 | 57篇 |
武器工业 | 1篇 |
无线电 | 1584篇 |
一般工业技术 | 3057篇 |
冶金工业 | 5416篇 |
原子能技术 | 188篇 |
自动化技术 | 2843篇 |
出版年
2023年 | 157篇 |
2022年 | 297篇 |
2021年 | 460篇 |
2020年 | 341篇 |
2019年 | 366篇 |
2018年 | 426篇 |
2017年 | 389篇 |
2016年 | 492篇 |
2015年 | 423篇 |
2014年 | 520篇 |
2013年 | 1072篇 |
2012年 | 856篇 |
2011年 | 1115篇 |
2010年 | 765篇 |
2009年 | 822篇 |
2008年 | 861篇 |
2007年 | 757篇 |
2006年 | 701篇 |
2005年 | 590篇 |
2004年 | 484篇 |
2003年 | 439篇 |
2002年 | 420篇 |
2001年 | 295篇 |
2000年 | 318篇 |
1999年 | 415篇 |
1998年 | 1465篇 |
1997年 | 882篇 |
1996年 | 685篇 |
1995年 | 434篇 |
1994年 | 396篇 |
1993年 | 408篇 |
1992年 | 195篇 |
1991年 | 177篇 |
1990年 | 160篇 |
1989年 | 156篇 |
1988年 | 145篇 |
1987年 | 136篇 |
1986年 | 128篇 |
1985年 | 151篇 |
1984年 | 133篇 |
1983年 | 122篇 |
1982年 | 103篇 |
1981年 | 115篇 |
1980年 | 108篇 |
1979年 | 99篇 |
1978年 | 96篇 |
1977年 | 176篇 |
1976年 | 313篇 |
1975年 | 83篇 |
1974年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The typical inventory routing problem deals with the repeated distribution of a single product from a single facility with an unlimited supply to a set of customers that can all be reached with out-and-back trips. Unfortunately, this is not always the reality. We introduce the inventory routing problem with continuous moves to study two important real-life complexities: limited product availabilities at facilities and customers that cannot be served using out-and-back tours. We need to design delivery tours spanning several days, covering huge geographic areas, and involving product pickups at different facilities. We develop an innovative randomized greedy algorithm, which includes linear programming based postprocessing technology, and we demonstrate its effectiveness in an extensive computational study. 相似文献
62.
Dr. Martin Meints 《Datenschutz und Datensicherheit - DuD》2006,30(1):13-16
Datenschutzmanagement ist eine gesetzlich verankerte Aufgabe, muss sich aber unter Wirtschaftlichkeitsgesichtspunkten in der betrieblichen und zunehmend auch der behördlichen Praxis in andere, bereits etablierte Prozessmanagementstrukturen wie ITIL oder Informationssicherheits-management Systeme (ISMS) einordnen. In diesem Beitrag werden die Möglichkeiten untersucht, die IT-Grundschutz als ein zukünftiges, ISO 27001-kompatibles ISMS bietet. Unter dem Gesichtspunkt der Normierung scheint eine Aktualisierung des Bausteins 3.5 “Datenschutz” dringend. 相似文献
63.
64.
Outage in digital microwave radio systems during multipath fading is highly correlated with the channel amplitude dispersion. This characteristic is exploited in a new digital microwave radio system measurement technique which yields dispersion signatures. These dispersion signatures can be readily applied to assess the effects of time varying channels on digital radio equipment. Thus, dispersion signatures can be used for in-service monitoring of equipment operation during actual fading. Routine maintenance assessment and laboratory evaluation of digital microwave radio equipment can also be readily carried out. The laboratory evaluation results can be used for system design both with and without diversity. 相似文献
65.
XML hat sich als Sprache zur Definition von Dokumenten für den universellen Datenaustausch etabliert. XML-Schema erm?glicht
ausgefeilte Definitionen für XML-Dokumente und hat beste Chancen, die bisher eingesetzte DTD abzul?sen. Neben einer allgemeinen
Einführung geht dieser Beitrag auch auf verfügbare Produkte und neue M?glichkeiten der objektorientierten Softwareentwicklung
mit XML-Schema ein.
Vorschl?ge an Prof. Dr. Frank Puppe <puppe@informatik.uni-wuerzburg.de> oder Dieter Steinbauer <dieter.steinbauer@schufa.de>
Alle „Aktuellen Schlagw?rter” seit 1988 finden Sie unter: www.ai-wuerzburg.de/as 相似文献
66.
Henry T. Y. Yang Martin Heinstein J.-M. Shih 《International journal for numerical methods in engineering》1989,28(6):1409-1428
The development and integration of available current methods and the development of new methods for an adaptive finite element analysis of metal forming processes are presented. The analysis includes large-strain, elastic–plastic, and thermal effects. Many numerical methods such as mesh generation, simulation of the contact between the workpiece and tool and die, and optimization of the finite element mesh are integrated and incorporated. In addition, an algorithm is developed which can detect certain severely distorted elements where the area of integration is approaching zero. The advantage of correcting these regions of locally distorted elements is demonstrated. These numerical methods are implemented in a finite element program developed for simulating metal forming processes, with the emphasis on automating the analysis. Examples include an axisymmetric stress simulation of a coldheading process, a plane strain simulation of an extrusion process and a plane strain simulation of orthogonal metal cutting, all with noticeable thermal effects. The orthogonal cutting forces and feed forces calculated are compared with two sets of experimental data, with good agreement. 相似文献
67.
68.
SA Syed KS Zahir JR Zink O Saglaam RJ Restifo JG Thomson 《Canadian Metallurgical Quarterly》1997,38(4):396-403
Reinstatement and spontaneous recovery of previously extinguished nicotine-taking behavior were examined in rats. Male subjects were trained to self-administer nicotine (30 microg/kg per infusion, IV; one 60-min session per day for 3 weeks). Extinction sessions were then given for 5-10 days during which saline was substituted for nicotine. Subsequently, in the first set of tests for nicotine seeking, the reinstatement of lever presses that previously delivered nicotine was examined after priming injections of saline and nicotine (75, 150 and 300 microg/kg, SC; and 30 and 60 microg/kg, IV). In the second set of tests for nicotine-seeking, rats were tested after an additional 21-day drug-free period during which they were not exposed to the self-administration chambers (a test for the spontaneous recovery of drug seeking), and after priming injections of nicotine (150 and 300 microg/kg, SC). Reinstatement of extinguished food-reinforced behavior after exposure to nicotine was also determined. Priming injections of nicotine reinstated nicotine seeking regardless of the route of administration. In addition, previously extinguished nicotine seeking recovered spontaneously after a 21-day period during which rats were not exposed to the drug-taking environment. Nicotine also reinstated extinguished food-reinforced behavior in rats with a history of nicotine self-administration, but not in drug-naive rats. The present results extend previous work with opioid and stimulant drugs on reinstatement of drug seeking by the self-administered drug. It also appears that, as with other positive reinforcers, the mere passage of time is a sufficient condition for the spontaneous recovery of extinguished nicotine seeking. 相似文献
69.
70.
Thomas Stieglitz Martin Schuettler Klaus Peter Koch 《IEEE engineering in medicine and biology magazine》2005,24(5):58-65
In the following article, the technologies to fabricate polyimide-based thin and flexible substrates with monolithically integrated electrode arrays and printed circuit boards (PCB) for hybrid electronic assemblies as well as an assembling technique that connects bare electronic dice with flexible PCBs are presented. The concept of modular, flexible biomedical microsystems as neural prostheses is introduced in general and described in detail in three examples. A cuff electrode with integrated multiplexer circuitry and standard implantable cables represents the combination of microtechnology with precision mechanics; a sieve electrode used as an implant in peripheral nerve regeneration studies demonstrates the next level of integration density but still uses a cable connection; and last, joint effort to fabricate the demonstrator of a vision prosthesis that is completely implantable in the eye with a wireless link for energy supply and data transmission is presented. System design, hybrid assembling technology, and flexible multilayer encapsulation using parylene and silicone rubber are the key components for creating a new generation of neural prostheses for complex and challenging new applications. 相似文献