全文获取类型
收费全文 | 81897篇 |
免费 | 6936篇 |
国内免费 | 3544篇 |
专业分类
电工技术 | 2934篇 |
技术理论 | 6篇 |
综合类 | 6174篇 |
化学工业 | 18907篇 |
金属工艺 | 7376篇 |
机械仪表 | 5163篇 |
建筑科学 | 5702篇 |
矿业工程 | 2922篇 |
能源动力 | 1917篇 |
轻工业 | 8495篇 |
水利工程 | 1422篇 |
石油天然气 | 3780篇 |
武器工业 | 678篇 |
无线电 | 3678篇 |
一般工业技术 | 7666篇 |
冶金工业 | 6228篇 |
原子能技术 | 497篇 |
自动化技术 | 8832篇 |
出版年
2024年 | 264篇 |
2023年 | 900篇 |
2022年 | 1779篇 |
2021年 | 2252篇 |
2020年 | 2475篇 |
2019年 | 1905篇 |
2018年 | 1702篇 |
2017年 | 2268篇 |
2016年 | 2638篇 |
2015年 | 2809篇 |
2014年 | 5013篇 |
2013年 | 5282篇 |
2012年 | 6134篇 |
2011年 | 6390篇 |
2010年 | 4643篇 |
2009年 | 4745篇 |
2008年 | 4059篇 |
2007年 | 5312篇 |
2006年 | 5018篇 |
2005年 | 4321篇 |
2004年 | 3703篇 |
2003年 | 3300篇 |
2002年 | 2858篇 |
2001年 | 2411篇 |
2000年 | 2022篇 |
1999年 | 1681篇 |
1998年 | 1285篇 |
1997年 | 1004篇 |
1996年 | 930篇 |
1995年 | 726篇 |
1994年 | 615篇 |
1993年 | 399篇 |
1992年 | 354篇 |
1991年 | 277篇 |
1990年 | 190篇 |
1989年 | 154篇 |
1988年 | 119篇 |
1987年 | 66篇 |
1986年 | 58篇 |
1985年 | 40篇 |
1984年 | 46篇 |
1983年 | 32篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 31篇 |
1979年 | 14篇 |
1977年 | 14篇 |
1961年 | 7篇 |
1959年 | 8篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
971.
回收废旧PVC的新技术 总被引:2,自引:0,他引:2
综述几种回收废旧PVC(聚氯乙烯)的工艺,包括溶剂法、机械法、化学法及焚烧法,其中的2种溶剂法都是欧洲新近开发的。溶剂法回收PVC的价格远低于新PVC。 相似文献
972.
工业管道测厚技术在化工厂的应用 总被引:1,自引:0,他引:1
本文较为详细地介绍了工业管道的规范化管理及其在化工厂的应用。指出管道定期定点测厚和计算机管理是工业管道规范化管理的重要内容。通过实施这一管理措施可以提高企业的经济效益和社会效益。 相似文献
973.
针对精密注塑件的生产,介绍了设计,成型精密注塑件的基本要求,探讨了原材料,注塑机,电压,环境温湿度及模具积垢等因素对生产精密注塑件稳定性的影响,研究了评估工艺参数敏感性的试验方法和获得稳定工艺的手段;说明了统计过程控制(SPC)的基本原理,以及如何利用控制图和工序能力指数CP,CPK来评估,预测工序能力,确保工序确定性。 相似文献
974.
针对多属性群决策中的共识问题, 提出两种使群体达成共识的方法. 假设群体决策的结果以从个体偏好通过集结得到的群体偏好为基础, 在使用算术加权集结算子和几何加权集结算子的条件下, 分别设计相应的共识达成算法, 并对算法的收敛性进行分析. 与已有方法相比, 所提出算法能够体现决策个体的差异和决策个体对群体的影响. 通过某市政图书馆空调系统安装方案的选择表明了所提出方法的合理性和可行性.
相似文献975.
Viability study of different reverse osmosis membranes for application in the tertiary treatment of wastes from the tanning industry 总被引:2,自引:0,他引:2
The tanning industry uses large quantities of water and produces a correspondingly large amount of wastewater with high levels of salts and organic materials. Before these wastewaters can be eliminated, they must be submitted to a suitable depuration treatment. However, conventional treatments such as those used for urban wastewater are not able to reduce the salt content sufficiently and new methods need to be studied in the light of new technologies. In this aspect, membrane technology is increasingly used as a separation technique in chemical and environmental engineering, including desalination, selective separation and wastewater treatment. In this paper, we describe a comparative study of six different reverse osmosis membranes, which were tested for their ability to reduce the salt content in the tertiary treatment after the elimination of chromium salts and organic matter of an effluent from a pilot plant for treating industrial wastewater from the tanning industry to reach the legal levels established for their safe disposal. The membranes were checked using a 3×10−3 m2 flat cell, where the concentrated streams were recirculated to the feed reservoir. 相似文献
976.
Takuya Goto 《Electrochimica acta》2005,50(6):1283-1288
Electrochemical formation of aluminum nitride was investigated in molten LiCl-KCl-Li3N systems at 723 K. When Al was anodically polarized at 1.0 V (versus Li+/Li), oxidation of nitride ions proceeded to form adsorbed nitrogen atoms, which reacted with the surface to form AlN film. The obtained nitrided film had a thickness of sub-micron order. The obtained nitrided layer consisted of two regions; the outer layer involving AlN and aluminum oxynitride and the inner layer involving metallic Al and AlN. When Al electrode was anodically polarized at 2.0 V, anodic dissolution of Al electrode occurred to give aluminum ions, which reacted with nitride ions in the melt to produce AlN particles (1-5 μm of diameter) of wurtzite structure. 相似文献
977.
物联网的基本功能是感知物理环境,并根据实时的感知信息和用户的执行需求实现对物理环境的控制.因此,感执模块是物联网软件的核心模块.为最终将软件体系结构应用于物联网软件的开发,在基于物理模型的物联网软件体系结构(physical-model driven software architecture,简称PMDA)研究的基础上,对PMDA 中的感执模型SEM进行求精,求精后的感执模型称为R-SEM.R-SEM 考虑了物联网的特有属性,将SEM的内部构件按照物理应用的感执工作流程分解为用通信顺序进程(communication sequential process,简称CSP)表达的子构件来说明构件端口的功能实现,并采用CSP 中的导管运算符来说明子构件的端口与构件的端口之间的同步,通过CSP 描述了子构件与子构件之间的交互.使用进程分析工具(process analysis toolkit,简称PAT)对R-SEM 进行了验证.验证结果表明:R-SEM 中子构件之间的交互、子构件的端口与构件的端口之间的同步保持了SEM 所具有的保证物理应用之间有效互联的性质——不死锁、不中止和不发散.由于R-SEM 精化了SEM 的内部组成,且保持了SEM 的有效互联性质,因此,R-SEM 对最终将PMDA 应用于物联网软件的开发具有实际的指导意义. 相似文献
978.
The catalytic reforming of methane by steam is an important industrial process that produces H2, CO and CO2, thus chemically transforming natural gas, coal gas and light hydrocarbon feedstocks to synthesis gas or hydrogen fuel. Methane-steam reforming may consist of a number of reactions depending on the reforming catalyst, operating conditions and feedstock composition, The typical industrially desirable reactions are the reverse of methanation (CH4 + H2O = CO + 3H2) and the water-gas shift (CO + H2O = CO2 + H2). Both reactions are equilibrium limited and the composition of the mixture that exits the reformer is in accordance with the one calculated thermodynarmically. Removal of reaction products at the reactor exit by means of selective membrane permeation can offer improved CH4 conversions and CO2 and H2 yields, assuming the subsequent utilization of the reject streams by a second methane-steam reformer. We numerically investigated the feasibility of a system of two tubular methane-steam reformers, in series with an intermediate permselective polyimide membrane permeator, as means of improving the overall CH4 conversion and the H2, CO2 yields over conventional methane-steam reforming equilibrium reaction-separation schemes that are currently in industrial practice. The unique feature of the permselective polyimide separator is the simultaneous removal of H2 and CO2 versus CH4 and CO from the reformed streams. The utilized 6FDA-3,3', 5,5'-TMB aromatic polyimide was reportedly characterized [10] and found to exhibit superior permselective properties compared with other polyimides of the same or different dianhydride sequence. Conversion and yield of the designed reactor-membrane permeator reforming system can be maximized by optimizing the permselective properties of the membrane material and the design variables of the reactors and the permeator. Product recovery and purity in the permeate stream need to be compromised to overall enhance methane conversion and product yield. The operating variables that were varied to investigate their effect on the magnitude of conversion and yield included the inlet pressure of the first reformer, the temperature of both reformers, and the permeator dimensionless Pe' number (variation of the first two variables results to a drastic change in the composition of the reformed stream that enters into the permeator). The numerical results show that the new reformer-membrane permeator cascade process can be more effective (it can offer increased CH4 conversions and H2, CO2 yields) than conventional equilibrium methane-steam reforming reaction-separation processes currently in practice. 相似文献
979.
980.