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   556730篇
  免费   48497篇
  国内免费   21032篇
电工技术   29611篇
技术理论   44篇
综合类   33569篇
化学工业   102044篇
金属工艺   28886篇
机械仪表   33219篇
建筑科学   43362篇
矿业工程   15209篇
能源动力   15258篇
轻工业   39187篇
水利工程   9227篇
石油天然气   31464篇
武器工业   3880篇
无线电   65121篇
一般工业技术   70051篇
冶金工业   28018篇
原子能技术   5464篇
自动化技术   72645篇
  2024年   2019篇
  2023年   7490篇
  2022年   13515篇
  2021年   19261篇
  2020年   15277篇
  2019年   14279篇
  2018年   15747篇
  2017年   18126篇
  2016年   16990篇
  2015年   22176篇
  2014年   27465篇
  2013年   34146篇
  2012年   34145篇
  2011年   37515篇
  2010年   33136篇
  2009年   31952篇
  2008年   30785篇
  2007年   29924篇
  2006年   30768篇
  2005年   27130篇
  2004年   18738篇
  2003年   16764篇
  2002年   16214篇
  2001年   14450篇
  2000年   14158篇
  1999年   15137篇
  1998年   12400篇
  1997年   10407篇
  1996年   9567篇
  1995年   7992篇
  1994年   6644篇
  1993年   4923篇
  1992年   3898篇
  1991年   2938篇
  1990年   2261篇
  1989年   1834篇
  1988年   1488篇
  1987年   1049篇
  1986年   787篇
  1985年   624篇
  1984年   414篇
  1983年   333篇
  1982年   295篇
  1981年   243篇
  1980年   210篇
  1979年   132篇
  1978年   74篇
  1977年   76篇
  1976年   92篇
  1975年   44篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Ceria-zirconia solid particles have been recognized as a key material of the automotive exhaust catalysts since they can release and uptake oxygen owing to the rapid reversible oxidation states of cerium between Ce3+ and Ce4+. Several methods have recently been described to prepare the CeO2-ZrO2 solid particles used in the catalysts. In this paper, a new coprecipitation method is used to prepare the CeO2-ZrO2 solid particles. The Ce-Zr alcogel is dried and calcined in flowing N2 not in flowing air under atmospheric pressure. The results show that the ceria-zirconia sample calcined at 650 °C has high surface area over 90 m2g−1, which drops to 40 m2g−1 following treatment at 900°C.  相似文献   
102.
103.
徐州地区采暖教室内CO2污染影响因素分析   总被引:1,自引:1,他引:0  
在徐州市采暖季节期间,实测3所高校3栋教学楼典型教室的室内CO2浓度、室内人员密度、室外空气流速等参数,分析不同状态的教室、不同的人员密度和不同的室外空气流速对室内CO2浓度的影响,提出改善采暖教室内CO2浓度的措施。  相似文献   
104.
The fault-state detection approach for blackbox testing consists of two phases. The first is to bring the system under test (SUT) from its initial state to a targeted state t and the second is to check various specified properties of the SUT at t. This paper investigates the first phase for testing systems specified as observable nondeterministic finite-state machines with probabilistic and weighted transitions. This phase involves two steps. The first step transfers the SUT to some state t' and the second step identifies whether t' is indeed the targeted state t or not. State transfer is achieved by moving the SUT along one of the paths of a transfer tree (TT) and state identification is realized by using diagnosis trees (DT). A theoretical foundation for the existence and characterization of TT and DT with minimum weighted height or minimum average weight is presented. Algorithms for their computation are proposed.  相似文献   
105.
大门小品建筑属多项目综合性工程。本文作者从管理者的角度 ,通过对公司大门及附属工程施工质量控制的总结 ,说明了质量控制应贯穿于工程施工的全过程  相似文献   
106.
He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
107.
磷矿中七种金属元素的光谱法测定   总被引:2,自引:0,他引:2  
陈名樑 《山西冶金》2004,27(1):36-37
研究了磷矿样品中7种金属元素锰、钴、镍,锌、铬、钼及铋的分析方法,选择了灵敏度高干扰少的谱线,绘制出工作曲线,对样品进行了科学处理,不必进行化学分离即可对七种元素同时测定,经合成样分析、回收实验及样品测定,证明此方法精确可靠,其回收率在98%-102%之间。  相似文献   
108.
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007.  相似文献   
109.
110.
A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry  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