全文获取类型
收费全文 | 749774篇 |
免费 | 8460篇 |
国内免费 | 1682篇 |
专业分类
电工技术 | 13672篇 |
综合类 | 602篇 |
化学工业 | 118234篇 |
金属工艺 | 30627篇 |
机械仪表 | 23443篇 |
建筑科学 | 17501篇 |
矿业工程 | 5252篇 |
能源动力 | 19173篇 |
轻工业 | 62472篇 |
水利工程 | 8738篇 |
石油天然气 | 18161篇 |
武器工业 | 48篇 |
无线电 | 80488篇 |
一般工业技术 | 151097篇 |
冶金工业 | 130735篇 |
原子能技术 | 18223篇 |
自动化技术 | 61450篇 |
出版年
2021年 | 6699篇 |
2019年 | 6360篇 |
2018年 | 11153篇 |
2017年 | 11258篇 |
2016年 | 11901篇 |
2015年 | 7539篇 |
2014年 | 12701篇 |
2013年 | 34139篇 |
2012年 | 19770篇 |
2011年 | 26675篇 |
2010年 | 21568篇 |
2009年 | 24063篇 |
2008年 | 24543篇 |
2007年 | 24161篇 |
2006年 | 21043篇 |
2005年 | 19297篇 |
2004年 | 18285篇 |
2003年 | 17842篇 |
2002年 | 17447篇 |
2001年 | 16976篇 |
2000年 | 16229篇 |
1999年 | 16106篇 |
1998年 | 37785篇 |
1997年 | 27600篇 |
1996年 | 21481篇 |
1995年 | 16497篇 |
1994年 | 14922篇 |
1993年 | 14555篇 |
1992年 | 11246篇 |
1991年 | 10973篇 |
1990年 | 10780篇 |
1989年 | 10577篇 |
1988年 | 10167篇 |
1987年 | 9071篇 |
1986年 | 8851篇 |
1985年 | 10132篇 |
1984年 | 9355篇 |
1983年 | 8898篇 |
1982年 | 8031篇 |
1981年 | 8277篇 |
1980年 | 7866篇 |
1979年 | 7925篇 |
1978年 | 7816篇 |
1977年 | 8866篇 |
1976年 | 11241篇 |
1975年 | 7080篇 |
1974年 | 6789篇 |
1973年 | 6876篇 |
1972年 | 5902篇 |
1971年 | 5523篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
992.
Guha A. Pavan A. Liu J. Rastogi A. Steeves T. 《Selected Areas in Communications, IEEE Journal on》1995,13(4):749-763
This paper describes the distributed system, network and software architecture, the application development environment, the performance, and the early lessons learned on the ATM LAN testbed Mercuri established at the Honeywell Technology Center, to develop distributed multimedia technologies for real-time control applications. We have developed a client-server-based software architecture on Sun Sparcstation-2s connected by a Fore Systems' ASX-100 ATM switch, with video processing handled by Parallax's X Video cards. The architecture enables network-transparent applications and provides simple primitives for multimedia capture, display, transmission, storage, and retrieval. A real-time multimedia-in-the-loop control application was developed as the vehicle for testing the capabilities and performance of the network. Our test measurements focus on the end-user-level performance metrics such as message throughput and round-trip delay as well as video-frame jitter under no-load and load conditions. Our results show that the maximum burst throughput that can be supported at the user level is 48 Mb/s using AAL 5, while round-trip delays for 4-kbyte messages are about 3 ms. Our experience reveals a number of performance bottlenecks and open issues in using commercial ATM switches for practical applications. Our conclusions are outlined 相似文献
993.
994.
We describe the sensitivity of sub-micron via integrity to high-temperature processing following via etch. It has been observed that thermal expansion of Al into the via hole, before tungsten deposition, may result in the fabrication of a deformed tungsten plug. Our results indicate that relaxation of the Al can give rise to stress-void formation under the tungsten plug. This may manifest itself either during electromigration stress or high-temperature storage. This mechanism represents a new reliability hazard for a tungsten-plug interconnect system 相似文献
995.
Eynard C. Lenti M. Lombardo A. Marengo O. Palazzo S. 《Selected Areas in Communications, IEEE Journal on》1995,13(5):893-907
The anticipated emergence of third-generation mobile systems, referred to as universal mobile telecommunication systems (UMTS), raises the problem of reconsidering the design of the databases destined to contain the user information. In particular, it is expected that the key concepts of the new database architectures will be high distribution and fast updating of information. So far, the problem of determining the most appropriate distributed database (DDB) architectures for third-generation mobile systems has not been widely dealt with in literature. This paper presents a methodology for evaluating hierarchical DDB architectures by means of an analytical model of the data querying operation. This methodology allows for structural alternatives, differing on account of the number of levels and branches in the hierarchy, to be evaluated in terms of query loads and mean response times, according to a given user mobility characterization and a given search protocol operation. By way of illustration, the paper discusses a case study, concerning a query operation arising from a location updating procedure and applied to a hierarchical tree-like DDB in which some structural alternatives are considered 相似文献
996.
G. B. Kainer 《Measurement Techniques》1996,39(4):366-368
This article presents a fundamentally new method for controlling the position of an object in three-dimensional space by using
a microinterferometer. This method assures high accuracy and efficiency. The method can be used for verifying accuracy of
contact gauges in position-measuring machinery.
Translated from Izmeritel'naya Tekhnika, No. 4, pp. 17–18, April, 1996. 相似文献
997.
The Warehouse Scheduling Problem is a deterministic multi-item inventory problem with a restriction on warehouse floor space available. We formulate a mixed integer nonlinear programming problem for the objective of minimizing long run inventory holding and order costs per unit of time. We integrate algorithms for staggering orders, described in companion papers, with a heuristic to choose the order sequences. The result is called Sequenced Staggering. We describe a new algorithm to generate order frequencies, called the powers-of-two-factor-of-three technique, as a generalization of Roundy's roundoff technique for powers-of-two policies. We report on a computational study of four hybrid algorithms for solving the warehouse scheduling problem, including the competing algorithm of Gallego, Queyranne, and Simchi-Levi. Based on these results, we recommend the combination of powers-of-two frequencies with Sequenced Staggering. 相似文献
998.
A. N. Atanov 《Measurement Techniques》1994,37(11):1320-1321
Translated from Izmeritel'naya Tekhnika, No. 11, pp. 66–67, November, 1994. 相似文献
999.
1000.
Continuing our work on the immunosuppressive activity of cyclolinopeptide A (CLA), a cyclic nonapeptide of the sequence: c-(-Leu-Ile-Ile-Leu-Val-Pro-Pro-Phe-Phe), we synthesized a series of 6 linear analogs of CLA, successively shortened at the N-terminus of the peptide chain. Immunosuppressive activity of acetates as well as trifluoroacetates of these peptides was investigated using PFC (humoral immunity) and DTH (cellular immunity) tests. It was found that the immunosuppressive potency of the peptides examined diminishes with shortening of the peptide chain. Octapeptide I with the sequence Ile-Ile-Leu-Val-Pro-Pro-Phe-Phe was found to be the most active of the whole series. The immunosuppressive activity increased again for a tripeptide fragment of CLA of the sequence Pro-Phe-Phe. The immunosuppressive activity of octapeptide probably depends on the suppression of IL-1, IL-6 and TNF production by the cells involved in immune and inflammatory response. 相似文献