首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   488366篇
  免费   7512篇
  国内免费   2515篇
电工技术   9468篇
技术理论   4篇
综合类   1391篇
化学工业   71895篇
金属工艺   17308篇
机械仪表   14759篇
建筑科学   13273篇
矿业工程   1902篇
能源动力   13856篇
轻工业   46736篇
水利工程   4296篇
石油天然气   6099篇
武器工业   147篇
无线电   64036篇
一般工业技术   90951篇
冶金工业   91379篇
原子能技术   8030篇
自动化技术   42863篇
  2022年   2848篇
  2021年   4455篇
  2020年   3290篇
  2019年   3830篇
  2018年   6028篇
  2017年   6104篇
  2016年   6409篇
  2015年   4771篇
  2014年   7937篇
  2013年   22994篇
  2012年   13047篇
  2011年   18018篇
  2010年   14214篇
  2009年   16002篇
  2008年   16841篇
  2007年   16662篇
  2006年   15213篇
  2005年   13641篇
  2004年   12949篇
  2003年   13063篇
  2002年   11993篇
  2001年   12694篇
  2000年   11744篇
  1999年   12743篇
  1998年   31334篇
  1997年   21808篇
  1996年   16607篇
  1995年   12539篇
  1994年   11065篇
  1993年   10860篇
  1992年   7673篇
  1991年   7298篇
  1990年   7007篇
  1989年   6626篇
  1988年   6444篇
  1987年   5303篇
  1986年   5154篇
  1985年   5994篇
  1984年   5379篇
  1983年   5115篇
  1982年   4696篇
  1981年   4694篇
  1980年   4446篇
  1979年   4112篇
  1978年   3801篇
  1977年   4561篇
  1976年   6088篇
  1975年   3179篇
  1974年   3060篇
  1973年   3074篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Gate oxide damage by plasma processing was evaluated using structures with various antenna lengths. The gate oxide damage by plasma processing was found to be monitored quantitatively by measuring the charge to breakdown, QBD. From the QBD measurements, we have confirmed that the degradation occurs during overetching, not in main etching. Plasma current was calculated from the decrease of QBD during the etching. The breakdown spot in the gate oxide was detected by photon emission and TEM. The LOCOS structure plays an important role for the degradation by plasma damage. In this paper, it is demonstrated that the QBD method is effective for realizing a highly reliable process against plasma damage  相似文献   
952.
Marshman  C. 《IEE Review》1994,40(4):SUPL3-SUPL8
Surveys show that, although there is generally high awareness of the legal requirement to conform with the EMC Directive, confusion and uncertainty remain with regard to both the legal and technical issues. The EMC Directive will be fully implemented in all member states of the EU from 1 January 1996. It is imperative to recognise that after this date it will be a criminal offence to market electrical/electronic products that do not conform with its protection requirements. The precise details of how enforcement will be carried out in each member state are unclear. The guidance given to the; enforcement bodies from the DTI is to help companies to conform rather than to prosecute. The overriding issue is that, whatever the level of enforcement, manufacturers have a duty in law to demonstrate conformance for their products. The process of demonstrating conformance also requires clarification. It is how to demonstrate that products conform that is the stumbling block for many companies. The author discusses the routes to compliance and planning for it. Case studies are briefly outlined and the growth areas in EMC compliance are discussed. A sample showing suggested contents for a technical construction file is also given  相似文献   
953.
Introduces the basic technologies that are associated with measurements of monolithic microwave integrated circuits. The use of test fixtures and wafer probe stations at ambient room temperature is reviewed and their role at thermal and cryogenic temperatures is discussed. With the increasing need for performing non-invasive measurements, advances in experimental field probing techniques are explored  相似文献   
954.
This paper looks first at the background to the development of intelligent networking concepts and then tracks this development to the advanced intelligent networks (AINs) of today. The network architecture and basic nodal functions are explained, and a brief review given of the essential intelligent network building blocks, namely the IN (intelligent network) call model and the enhanced CCITT No.7 signalling system. Typical intelligent network services are examined and the tutorial finishes with a review of the latest IN standards  相似文献   
955.
26 previously treated patients with progressive recurrent small cell lung cancer (SCLC) were given vinorelbine (Navelbine), 30 mg/m2 weekly. All patients had responded to first-line chemotherapy and were off therapy for at least 3 months. Partial response was observed in 4 out of 25 eligible patients (16%; 95% confidence interval 4-36%), stable disease in 7 patients and progression in 12 patients. The limiting toxicity was a non-cumulative leucopenia (80%, 32% WHO grade 3-4). Reaction at the site of injection was observed in 5 patients, causing treatment discontinuation in 2 cases. Other non-haematological toxicities were moderate. These results suggest acceptable toxicity and some antitumour activity of vinorelbine in pretreated SCLC patients.  相似文献   
956.
957.
Using ion exchange chromatography and an ATP-dependent actin precipitation step, we have isolated three myosin-I isozymes that, together, account for most of the K+EDTA-ATPase activity recovered from extracts of Dictyostelium. The two major myosin-I isozymes, present in approximately equal amounts, had apparent molecular masses of 125 kDa on SDS gels and have been identified by amino acid sequence analysis as the products of the Dictyostelium myosin-IB (DMIB) and myosin-ID (DMID) genes. DMIB, with a specific K+EDTA-ATPase activity 10-fold higher than DMID, was responsible for most of the activity in cell extracts. The third isozyme, present in low amounts, had an apparent molecular mass of 137 kDa on SDS gels and is too large to be the product of any of the known myosin-I genes. DMIB eluted from DE53 cellulose columns as two distinct peaks (II and III). Addition of the phosphatase inhibitor okadaic acid to the extraction buffer increased the fraction of DMIB recovered from growth phase cells in peak III from 35 to 70%. DMIB isolated from peak III, but not from peak II, displayed a significant level of actin-activated MgATPase activity. These results indicate that peak III represents a phosphorylated, actin-activatable form of DMIB.  相似文献   
958.
959.
Fracture toughness and fatigue crack propagation (FCP) of plain and modified anhydride-cured epoxy resin (EP) were studied at ambient temperature. Liquid carboxyl-terminated acrylonitrile-butadiene (CTBN) and silicon (SI) rubber dispersions were used as tougheners for the EP. The morphology of the modified EP was characterized by dynamic mechanical analysis (DMA) and by scanning electron microscopy (SEM). The fracture toughness, Kc, of the compositions decreased with increasing deformation rate. Kc of the EP was slightly improved by CTBN addition and practically unaffected by incorporation of the SI dispersion when tests were performed at low cross-head speed, v. Both modifiers improved Kc at high v, and also the resistance to FCP, by shifting the curves to higher stress intensity factor ranges, ΔK, by comparison with the plain EP. It was established that both fracture and fatigue performance rely on the compliance, JR, at the rubbery plateau, and thus on the apparent molecular mass between crosslinks, Mc. The failure mechanisms were less dependent upon the loading mode (fracture, fatigue), but differed basically for the various modifiers. Rubber-induced cavitation and shear yielding of the EP were dominant for CTBN, whereas crack bifurcation and branching controlled the cracking in SI-modified EP. The simultaneous use of both modifiers resulted in a synergistic effect for both the fracture toughness at high deformation rate and the FCP behavior.  相似文献   
960.
This article describes a test piece that minimizes the spread of the results of testing of composite materials on a metal base by extension in the direction of a reinforcing fiber and, from the results, determines the mechanical properties of intermediate and finished products made of these materials.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 39–40, October, 1993.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号