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   295293篇
  免费   27185篇
  国内免费   14040篇
电工技术   20736篇
技术理论   30篇
综合类   27506篇
化学工业   46024篇
金属工艺   19313篇
机械仪表   14843篇
建筑科学   37682篇
矿业工程   14286篇
能源动力   12984篇
轻工业   20523篇
水利工程   11773篇
石油天然气   14466篇
武器工业   4135篇
无线电   19909篇
一般工业技术   26704篇
冶金工业   14664篇
原子能技术   2594篇
自动化技术   28346篇
  2024年   1460篇
  2023年   4460篇
  2022年   8168篇
  2021年   10378篇
  2020年   10158篇
  2019年   7962篇
  2018年   7428篇
  2017年   9469篇
  2016年   10655篇
  2015年   11321篇
  2014年   19210篇
  2013年   17828篇
  2012年   20872篇
  2011年   22925篇
  2010年   16764篇
  2009年   17427篇
  2008年   15634篇
  2007年   19116篇
  2006年   17626篇
  2005年   15078篇
  2004年   12613篇
  2003年   10816篇
  2002年   9018篇
  2001年   7488篇
  2000年   6433篇
  1999年   5115篇
  1998年   3807篇
  1997年   3349篇
  1996年   2705篇
  1995年   2284篇
  1994年   1901篇
  1993年   1378篇
  1992年   1162篇
  1991年   888篇
  1990年   735篇
  1989年   659篇
  1988年   400篇
  1987年   292篇
  1986年   246篇
  1985年   260篇
  1984年   205篇
  1983年   167篇
  1982年   123篇
  1981年   105篇
  1980年   110篇
  1979年   48篇
  1978年   24篇
  1977年   24篇
  1975年   23篇
  1959年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
美国钢铁企业的并购浪潮及特点分析   总被引:3,自引:0,他引:3  
介绍了最近美国大型钢铁企业发生的主要并购活动。并对这些并购活动的特点进行了分析。  相似文献   
102.
建立垂直管吸收器管内泡式吸收过程中传热传质的数学物理模型,对其泡式吸收过程进行数值研究,获得泡式吸收方式的一些传热传质特性,为吸收器的优化设计提供一定理论指导。  相似文献   
103.
Comments on the article "A house divided? The psychology of red and blue America" by D. C. Seyle and M. L. Newman (see record 2006-11202-001). Seyle and Newman concluded that the red and blue metaphor is inaccurate and proposed a purple America strategy to better convey that the majority of people do not align themselves with political extremes. There is interdisciplinary agreement on this. Although not cited by Seyle and Newman, the findings by Professor Fiorina of Stanford University were reported by the APA Monitor on Psychology in its coverage of the 2005 APA State Leadership Conference (Murray Law, 2005). In contrast to their social psychological analysis, Seyle and Newman were incorrect in concluding that "[a]s psychologists, we are not in a position to change either the elements of the American political system that may spur this conflict or even the decisions made by pundits, politicians, and reporters about the terms they choose to use in political discussion" (p. 579). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
104.
In this paper, AssetCollector is presented, which is a system for managing collections of cultural assets. AssetCollector covers the needs of collection curators towards defining, populating and searching a collection in a flexible way, while supporting them in generating reports based on the collection’s assets and reusing them in order to build web sites and CD-ROMs. In order to support the above functionality, the system provides the content structuring subsystem, the content input subsystem, the search subsystem and the report subsystem. The use of the subsystems is straightforward and requires no technical skills from the curators. AssetCollector has been successfully applied for organizing various collections of cultural assets in Greece, such as archaeological sites, museums and published books. In the future, an evaluation procedure is planned in order to further refine the use of the system according to the targeted users’ needs. Furthermore, more import and export facilities will be provided, which will make the system compliant with widely accepted standards.  相似文献   
105.
常减压蒸馏装置换热网络的节能优化   总被引:4,自引:0,他引:4  
利用夹点技术理论对耗能严重的某炼油厂常减压蒸馏装置进行用能诊断分析;并结合热力学原理得到两种优化换热网络,节能效果显著。  相似文献   
106.
There has been considerable recent progress in II-VI semiconductor material and in methods for improving performance of the associated radiation detectors. New high resistivity CdZnTe material, new contact technologies, new detector structures, new electronic correction methods have opened the field of nuclear and x-ray imaging for industrial and medical applications. The purpose of this paper is to review new developments in several of these fields. In addition, we will present some recent results at LETI concerning first the CdTe 2-D imaging system (20 × 30 mm2 with 400 × 600 pixels) for dental radiology and second the CdZnTe fast pulse correction method applied to a 5 × 5 × 5 mm3 CdZnTe detector (energy resolution = 5% for detection efficiency of 85% at 122 keV) for medical imaging.  相似文献   
107.
Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion.  相似文献   
108.
A remarkable nonlinearity has been observed for electric transport in K-TCNQ (potassium tetracyanoquinodimethane) quasi-one-dimensional conductor. The negative differential resistance region appears afterV m (turn over voltage), beyond which voltage goes down with increase of current. A possible mechanism is discussed in terms of dynamics of charged solitons and domain walls in one-dimensional molecular stacks of these types of crystals.  相似文献   
109.
ETRⅠ-30调速器是瑞士爱舍维斯工厂生产的具有PID调节规律的电液调速器。本文对其液压控制系统作了较详细的介绍,供有关人员参考。  相似文献   
110.
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