全文获取类型
收费全文 | 80925篇 |
免费 | 7266篇 |
国内免费 | 4257篇 |
专业分类
电工技术 | 3096篇 |
技术理论 | 5篇 |
综合类 | 6643篇 |
化学工业 | 16344篇 |
金属工艺 | 7194篇 |
机械仪表 | 5440篇 |
建筑科学 | 5058篇 |
矿业工程 | 2871篇 |
能源动力 | 1878篇 |
轻工业 | 7276篇 |
水利工程 | 1501篇 |
石油天然气 | 3473篇 |
武器工业 | 741篇 |
无线电 | 4756篇 |
一般工业技术 | 7825篇 |
冶金工业 | 6317篇 |
原子能技术 | 515篇 |
自动化技术 | 11515篇 |
出版年
2024年 | 372篇 |
2023年 | 1021篇 |
2022年 | 1939篇 |
2021年 | 2362篇 |
2020年 | 2732篇 |
2019年 | 2086篇 |
2018年 | 1883篇 |
2017年 | 2325篇 |
2016年 | 2726篇 |
2015年 | 2858篇 |
2014年 | 4956篇 |
2013年 | 5227篇 |
2012年 | 5924篇 |
2011年 | 6186篇 |
2010年 | 4502篇 |
2009年 | 4609篇 |
2008年 | 4057篇 |
2007年 | 5157篇 |
2006年 | 4929篇 |
2005年 | 4218篇 |
2004年 | 3645篇 |
2003年 | 3210篇 |
2002年 | 2781篇 |
2001年 | 2378篇 |
2000年 | 2004篇 |
1999年 | 1655篇 |
1998年 | 1268篇 |
1997年 | 1003篇 |
1996年 | 911篇 |
1995年 | 751篇 |
1994年 | 624篇 |
1993年 | 402篇 |
1992年 | 372篇 |
1991年 | 298篇 |
1990年 | 211篇 |
1989年 | 189篇 |
1988年 | 149篇 |
1987年 | 87篇 |
1986年 | 72篇 |
1985年 | 53篇 |
1984年 | 49篇 |
1983年 | 39篇 |
1982年 | 30篇 |
1981年 | 23篇 |
1980年 | 30篇 |
1979年 | 13篇 |
1977年 | 19篇 |
1964年 | 9篇 |
1959年 | 10篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Cathy Lawson Douglas C. Montgomery 《Quality and Reliability Engineering International》2006,22(8):971-984
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.
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.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
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.
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