全文获取类型
收费全文 | 325900篇 |
免费 | 27340篇 |
国内免费 | 16936篇 |
专业分类
电工技术 | 27479篇 |
技术理论 | 63篇 |
综合类 | 40690篇 |
化学工业 | 36197篇 |
金属工艺 | 11969篇 |
机械仪表 | 16736篇 |
建筑科学 | 46106篇 |
矿业工程 | 16616篇 |
能源动力 | 19574篇 |
轻工业 | 16366篇 |
水利工程 | 15051篇 |
石油天然气 | 13055篇 |
武器工业 | 3035篇 |
无线电 | 21606篇 |
一般工业技术 | 25148篇 |
冶金工业 | 18571篇 |
原子能技术 | 3744篇 |
自动化技术 | 38170篇 |
出版年
2024年 | 1262篇 |
2023年 | 4004篇 |
2022年 | 7200篇 |
2021年 | 8403篇 |
2020年 | 8922篇 |
2019年 | 7664篇 |
2018年 | 6944篇 |
2017年 | 8369篇 |
2016年 | 9790篇 |
2015年 | 10544篇 |
2014年 | 19047篇 |
2013年 | 17468篇 |
2012年 | 21884篇 |
2011年 | 23635篇 |
2010年 | 18719篇 |
2009年 | 19331篇 |
2008年 | 17928篇 |
2007年 | 22713篇 |
2006年 | 20925篇 |
2005年 | 17987篇 |
2004年 | 15279篇 |
2003年 | 13654篇 |
2002年 | 11373篇 |
2001年 | 9641篇 |
2000年 | 8156篇 |
1999年 | 6625篇 |
1998年 | 5047篇 |
1997年 | 4359篇 |
1996年 | 4036篇 |
1995年 | 3361篇 |
1994年 | 3003篇 |
1993年 | 2253篇 |
1992年 | 1969篇 |
1991年 | 1512篇 |
1990年 | 1313篇 |
1989年 | 1141篇 |
1988年 | 920篇 |
1987年 | 632篇 |
1986年 | 477篇 |
1985年 | 437篇 |
1984年 | 404篇 |
1983年 | 288篇 |
1982年 | 279篇 |
1981年 | 194篇 |
1980年 | 167篇 |
1979年 | 132篇 |
1978年 | 73篇 |
1977年 | 80篇 |
1976年 | 57篇 |
1975年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
2.
3.
In this paper, we study scheduling games under mixed coordination mechanisms on hierarchical machines. The two scheduling policies involved are ‐ and ‐, where ‐ (resp., ‐) policy sequences jobs in nondecreasing order of their hierarchies, and jobs of the same hierarchy in nonincreasing (resp., nondecreasing) order of their processing times. We first show the existence of a Nash equilibrium. Then we present the price of anarchy and the price of stability for the games with social costs of minimizing the makespan and maximizing the minimum machine load. All the bounds given in this paper are tight. 相似文献
4.
无刷同步电机的励磁系统对励磁电流的测量是制约该励磁方式发展的一大障碍。设计了一个射频系统可以用来解决同步电机的励磁电流的测量问题。该系统可以方便地检测到同步电机励磁机的整流二极管的工作状态并且可以动态地显示励磁电流,极大地方便了运行人员做出判断,而且结构简单、方便实用。 相似文献
5.
6.
The performance of the energy consumption of an electronic valve and a classical thermostatic valve has been compared when these expansion valves are adopted in a vapour compression plant subjected to a cold store. The main aim is to verify experimentally which type of expansion valve would be preferable from energy point of view when a classical thermostat or a fuzzy logic algorithm are used as the control system for the refrigeration capacity. The fuzzy logic‐based control is able to modulate continuously the compressor speed through an inverter. The results show that with a fuzzy algorithm, the thermostatic expansion valve allows an energy saving of about 8% in comparison with the electronic valve. When on–off control is used, the electric energy consumption obtained both with the electronic valve and with the thermostatic valve is comparable. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
8.
The problem of operating freeze drying of pharmaceutical products in vials placed in trays of a freeze dryer to remove free water (in frozen state) at a minimum time was formulated as an optimal control problem. Two different types of freeze dryer designs were considered. In type I freeze dryer design, upper and lower plate temperatures were controlled together, while in type II freeze dryer design, upper and lower plate temperatures were controlled independently. The heat input to the material being dried and the drying chamber pressure were considered as control variables. Constraints were placed on the system state variables by the melting and scorch temperatures during primary drying stage. Necessary conditions of optimality for the primary drying stage of freeze drying process in vials are derived and presented. Furthermore, an approach for constructing the optimal control policies that would minimize the drying time for the primary drying stage was given. In order to analyze optimal control policy for the primary drying stage of the freeze-drying process in vials, a rigorous multi-dimensional unsteady state mathematical model was used. The theoretical approach presented in this work was applied in the freeze drying of skim milk. Significant reductions in the drying times of primary drying stage of freeze drying process in vials were obtained, as compared to the drying times obtained from conventional operational policies. 相似文献
9.
大型连杆流线简易试验方法 总被引:1,自引:1,他引:0
程里 《理化检验(物理分册)》2004,40(9):457-458
介绍了一种大型连杆流线的简易试验方法及其评价原则。该方法可清晰显示流线,并适合任何尺寸和形状的锻造连杆的流线试验。 相似文献
10.
Cs-K混合蒸气中Cs(8D)+K(4S)碰撞能量转移 总被引:3,自引:3,他引:0
在Cs-K混合蒸气中,两步激发Cs原子到8D态,观察了Cs(8D) K(4S)→Cs(5D) K(4P)碰撞能量合并逆过程(REP,reverse energy pooling)。应用双调制技术探测K(4P)原子发射的荧光,基态K原子密度用光学吸收方法测量。得到了REP速率系数,讨论了其它过程对速率系数的影响. 相似文献