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   78723篇
  免费   6670篇
  国内免费   3547篇
电工技术   4115篇
技术理论   5篇
综合类   5906篇
化学工业   16367篇
金属工艺   7351篇
机械仪表   5181篇
建筑科学   5131篇
矿业工程   2982篇
能源动力   1925篇
轻工业   7357篇
水利工程   1382篇
石油天然气   3339篇
武器工业   633篇
无线电   4101篇
一般工业技术   7105篇
冶金工业   6461篇
原子能技术   470篇
自动化技术   9129篇
  2024年   351篇
  2023年   958篇
  2022年   1802篇
  2021年   2222篇
  2020年   2529篇
  2019年   1907篇
  2018年   1683篇
  2017年   2121篇
  2016年   2492篇
  2015年   2674篇
  2014年   4762篇
  2013年   4983篇
  2012年   5690篇
  2011年   6007篇
  2010年   4355篇
  2009年   4483篇
  2008年   3952篇
  2007年   5073篇
  2006年   4816篇
  2005年   4194篇
  2004年   3580篇
  2003年   3185篇
  2002年   2793篇
  2001年   2379篇
  2000年   1980篇
  1999年   1637篇
  1998年   1240篇
  1997年   985篇
  1996年   899篇
  1995年   709篇
  1994年   593篇
  1993年   377篇
  1992年   349篇
  1991年   271篇
  1990年   189篇
  1989年   150篇
  1988年   118篇
  1987年   77篇
  1986年   60篇
  1985年   43篇
  1984年   44篇
  1983年   32篇
  1982年   19篇
  1981年   17篇
  1980年   25篇
  1979年   14篇
  1977年   15篇
  1964年   8篇
  1959年   9篇
  1951年   18篇
排序方式: 共有10000条查询结果,搜索用时 3 毫秒
11.
Variation exists in all processes. Significant work has been done to identify and remove sources of variation in manufacturing processes resulting in large returns for companies. However, business process optimization is an area that has a large potential return for a company. Business processes can be difficult to optimize due to the nature of the output variables associated with them. Business processes tend to have output variables that are binary, nominal or ordinal. Examples of these types of output include whether a particular event occurred, a customer's color preference for a new product and survey questions that assess the extent of the survey respondent's agreement with a particular statement. Output variables that are binary, nominal or ordinal cannot be modeled using ordinary least‐squares regression. Logistic regression is a method used to model data where the output is binary, nominal or ordinal. This article provides a review of logistic regression and demonstrates its use in modeling data from a business process involving customer feedback. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
12.
13.
This paper presents an efficient method which provides the optimal generation mix and the optimal generation construction process. The approximation method in which the dynamic programming technique and gradient method are combined is applied to determine the optimal generation mix with hydropower generation technologies. The successive approximations dynamic programming (SADP) technique, which is very suitable for high-dimensional multistage decision process problems, is used for obtaining the optimal generation construction process. The effectiveness and feasibility of the developed technique are demonstrated on a practical power system model which has five types of generation technologies including a hydropower generation technology.  相似文献   
14.
What has become known as Community Operational Research has been around in the UK for many years. The election of Jonathan Rosenhead as President of the UK OR Society in 1986–87 was the catalyst for bringing together and expanding activities which had been carried out largely by individuals working in isolation on a voluntary basis. The following five years have seen the establishment of the Community OR Unit at Northern College, the Centre for Community OR at Hull University and the Community OR Network, which supports the activities of volunteer OR workers across the UK. This paper reviews the range and types of work which have been undertaken by various practitioners. An assessment of the success of community OR is made and a number of issues which have arisen are discussed. Finally, given the diverse nature of community OR, its practice and practitioners, there is some discussion about the future of the area.  相似文献   
15.
吴正立  严利人 《微电子学》1996,26(3):189-191
隧道小孔中超薄SiO2的生长是EEPROM电路制造的关键工艺之一。采用SUPREM-Ⅲ工艺模拟程序对超薄SiO2的热生长进行了工艺模拟,经过大量的工艺实验及优化,确定了超薄SiO2的最佳生长条件,生长出的SiO2性能良好,完全可满足EEPROM研制的要求。  相似文献   
16.
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry  相似文献   
17.
所开发的压水堆核燃料循环分析计算机经济程序包括12个子程序,代表着压水堆整个核燃料循环各种不同的工艺过程。本程序能算出压水堆核电站核燃料循环中燃料费用对发电成本的影响,给出各工艺过程对燃料成本的敏感度分析,并尽可能给出燃料循环中燃料材料及服务的价格数据.  相似文献   
18.
介绍了二次盐水及离子膜电解工序的主要设备和流程,对二次盐水及离子膜电解工序运行中出现的问题进行了分析,并提出了解决措施。  相似文献   
19.
铝型材推弯工艺   总被引:5,自引:0,他引:5  
通过铝型材圆环的推弯实验,研究了推弯工艺原理、变形过程,结合有限元模拟得到了和实验结果相吻合的型材厚度分布、成形零件卸载回弹后的曲率半径及型材截面畸变.结果表明:推弯零件曲率及截面畸变一致性高,成形模具结构简单且便于调整,数值模拟可以用于推弯工艺的优化分析.  相似文献   
20.
The growth structure of MgF2 and NdF3 films grown on polished CaF2(111) substrates deposited by molecular beam deposition has been investigated using transmission electron microscopy (TEM) of microfractographical and surface replications as well as cross-sectional TEM, atomic force microscopy, packing density, and absorption measurements. It has been shown that by taking advantage of ultrahigh vacuum environments and a special stratification property of MgF2 and NdF3 films, the preparation of nanocrystalline films of high packing density and low optical absorption is possible at a substrate temperature of 425 K.  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