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   277165篇
  免费   4132篇
  国内免费   1303篇
电工技术   5174篇
综合类   292篇
化学工业   41991篇
金属工艺   11550篇
机械仪表   7747篇
建筑科学   8116篇
矿业工程   593篇
能源动力   7276篇
轻工业   26795篇
水利工程   2239篇
石油天然气   1445篇
武器工业   8篇
无线电   33306篇
一般工业技术   50532篇
冶金工业   56125篇
原子能技术   4105篇
自动化技术   25306篇
  2021年   2198篇
  2020年   1497篇
  2019年   2009篇
  2018年   3057篇
  2017年   2872篇
  2016年   3228篇
  2015年   2615篇
  2014年   4136篇
  2013年   12998篇
  2012年   7019篇
  2011年   9730篇
  2010年   7818篇
  2009年   8410篇
  2008年   9215篇
  2007年   9290篇
  2006年   8512篇
  2005年   7852篇
  2004年   7337篇
  2003年   7300篇
  2002年   7207篇
  2001年   7025篇
  2000年   6318篇
  1999年   6971篇
  1998年   17094篇
  1997年   12131篇
  1996年   9458篇
  1995年   7229篇
  1994年   6387篇
  1993年   6197篇
  1992年   4490篇
  1991年   4260篇
  1990年   3951篇
  1989年   3857篇
  1988年   3733篇
  1987年   3239篇
  1986年   3121篇
  1985年   3795篇
  1984年   3436篇
  1983年   3028篇
  1982年   2818篇
  1981年   2823篇
  1980年   2676篇
  1979年   2515篇
  1978年   2466篇
  1977年   3016篇
  1976年   4356篇
  1975年   2080篇
  1974年   1950篇
  1973年   1937篇
  1972年   1569篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
A technique for measuring optical dot gain, i.e. the relative difference between the actual screen dot and the optically perceived one, is presented. By combining measurements from the non-optical nuclear microprobe with data from image analyzing technique the optical dot gain can be determined. The procedure to reach pixel by pixel correlation on a micrometer scale is discussed. In the newsprint sample studied in this investigation a typical optical dot gain between 15 and 20% was deduced. The variation in the optical dot gain was correlated with other characteristic parameters of the print and newsprint and especially a positive correlation to the mass density of the newsprint was observed.  相似文献   
952.
953.
954.
Taking into consideration the knock-on cascade mechanism and the free volume theory, the cooling condition dependentR s (ion etching rate) is investigated for a liquid-quenched Fe-10at%Si-15at%B alloy glass. A highR s is found in a slow cooled glass.  相似文献   
955.
Despite its empirical and normative strengths, the underlying conceptual base of the Comprehensive Rorschach System at times lacks clarity and an overarching theory of personality that can help psychodiagnosticians make more clinically relevant inferences. After reviewing the functions provided by an integral theory of personality, the author focuses on the Experience Actual:Experienced Stimulation (EA:es) index as a way of demonstrating how mechanistic jargon and lack of a guiding theory and conceptual clarity can lead to misleading and contradictory inferences. Case examples are provided, and some of the empirical foundations of the EA:es index are reviewed. The author concludes by offering recommendations on ways in which the Comprehensive System can become more sensitive in its appearance to capturing the complexities of personality functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
956.
The demand for anticoagulation services is rising. Warfarin anticoagulation has been shown to reduce the risk of stroke in patients with non-valvular atrial fibrillation by 68%. This raises issues about how services are best organized to initiate and monitor anticoagulation in this potentially large group of patients. We report the results of a regional postal survey undertaken to describe the views of general practitioners and consultants regarding warfarin anticoagulation in light of this potentially high increase in demand.  相似文献   
957.
958.
The paper describes the development of a software design aid for use at the conceptual stage of engineering design. It is intended for use in the design of mechatronic products but has wider potential uses. Early approaches were based on function structures and tables of options and the system that evolved allows the assembly of schemes linked by matching their input and output ports. A database of components is provided which can be accessed via different indexes and the designer can easily create and compare alternative schemes at the concept stage.A bond graph approach is used to define the interconnections between components. This allows correct port matching but also provides for future development such as constraint propagation through the design and links to simulation tools.  相似文献   
959.
960.
In crack detection and sizing by the alternating current field measurement technique, U-shaped wires or coils excited by a high-frequency AC current source can be used to induce the surface field in the workpiece. The authors present a modeling technique for the interaction of a fatigue crack in a ferromagnetic metal with the surface field resulting from an inducer with two U-shaped wires. This work is an extension of a previous modeling technique to have developed for infinitely long (one-dimensional) cracks. In the present technique, the boundary of the fatigue crack is approximated by a circular arc, leading to a formulation for an efficient computation of the field-flaw interaction. Various numerical and experimental results supporting the modeling and illustrating the behavior of the magnetic field and electric potential at the metal surface around circular-arc cracks are presented  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