全文获取类型
收费全文 | 41163篇 |
免费 | 4327篇 |
国内免费 | 2877篇 |
专业分类
电工技术 | 3549篇 |
技术理论 | 1篇 |
综合类 | 3842篇 |
化学工业 | 1865篇 |
金属工艺 | 3619篇 |
机械仪表 | 7363篇 |
建筑科学 | 1173篇 |
矿业工程 | 1906篇 |
能源动力 | 552篇 |
轻工业 | 3097篇 |
水利工程 | 380篇 |
石油天然气 | 550篇 |
武器工业 | 359篇 |
无线电 | 3242篇 |
一般工业技术 | 2764篇 |
冶金工业 | 1579篇 |
原子能技术 | 86篇 |
自动化技术 | 12440篇 |
出版年
2024年 | 192篇 |
2023年 | 853篇 |
2022年 | 1466篇 |
2021年 | 1584篇 |
2020年 | 1540篇 |
2019年 | 1127篇 |
2018年 | 997篇 |
2017年 | 1236篇 |
2016年 | 1436篇 |
2015年 | 1659篇 |
2014年 | 2637篇 |
2013年 | 2157篇 |
2012年 | 3041篇 |
2011年 | 3168篇 |
2010年 | 2374篇 |
2009年 | 2355篇 |
2008年 | 2255篇 |
2007年 | 2865篇 |
2006年 | 2692篇 |
2005年 | 2277篇 |
2004年 | 1801篇 |
2003年 | 1561篇 |
2002年 | 1311篇 |
2001年 | 1152篇 |
2000年 | 934篇 |
1999年 | 720篇 |
1998年 | 555篇 |
1997年 | 471篇 |
1996年 | 356篇 |
1995年 | 336篇 |
1994年 | 277篇 |
1993年 | 203篇 |
1992年 | 150篇 |
1991年 | 110篇 |
1990年 | 105篇 |
1989年 | 108篇 |
1988年 | 82篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 31篇 |
1984年 | 17篇 |
1983年 | 26篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1974年 | 5篇 |
1963年 | 5篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
101.
H. Perez-Blanco 《International Journal of Refrigeration》1993,16(6):429-433
The search for high-efficiency, gas-fired cooling cycles has led to the development of dual-loop absorption machines with cooling coefficients of performance (COPs) in the 1.2 to 1.7 range. This increased performance may call for high generator temperatures, new working fluids or new materials of construction. In most cases, two different sets of working fluids are required. The conceptual design presented here is aimed at obtaining high efficiencies with relatively low temperatures, employing only one set of fluids. The concept consists of two loops coupled in a configuration aimed at minimizing the loss of thermodynamic availability incurred when transferring refrigerant between the loops. The working fluid pair is a solution of lithium bromide-water. The calculated COPs are of the order of 1.8. The cycle relies on an elaborate evaporator-absorber combination. The paper presents the conceptual design, the critical assumptions, and the performance calculations for the concept. 相似文献
102.
本文介绍了汉英机器翻译系统中从中间媒介语言生成英语的生成系统的词汇结构和功能,描述了生成系统各个层次之间的转换原理。为了说明清楚,在叙述中注意了列举从中间媒介中间媒介语言到目标语句的生成实例。 相似文献
103.
104.
The communicating finite state machines can exchange messages over bounded FIFO channels. In this paper, a new technique, called reverse reachability analysis, is proposed to detect deadlocks on the communication between the communicating finite state machines. The technique is based on finding reverse reachable paths starting from possible deadlock states. If a reverse reachable path can reach the initial global state, then deadlock occurs. Otherwise the communication is deadlock-free. The effectiveness of the technique has been verified by some real protocols such as a specification of X.25 call establishment/clear protocol and Bartlet's alternating bit protocol. 相似文献
105.
HVS:一个半现实全景图时空模型 总被引:7,自引:2,他引:5
利用实景图象组成具有空间感和时间感的虚拟空间,我们称之为半现实。这种具有空间“上下文”和时间“上下文”能力的半现实全景图可以应用于许多方面。文中描述了这种半现实HVS的建模思想,给出了组成时空座标系的方法,并且讨论了实现中的若干问题。 相似文献
106.
A procedure and underlying algorithm for extracting knowledge from production and inventory databases to support engineering management activities is described. The process searches for, detects and isolates behaviour patterns inherent in the data. It relates these patterns to production irregularities, suggests connections with specific causes and helps propose possible corrective or preventive actions. The approach is based on a four-phase procedure: (1) the decision-maker focuses on the subject or difficulty at issue, represented by a target concept; (2) the KEDB algorithm, based on a machine learning approach, processes the relevant database and provides knowledge characterizing and classifying the target concept; (3) the output is interpreted in Pareto fashion as a series of possible circumstances explaining the target concept behaviour; and (4) based on these causes, the decision-maker decides on possible corrective actions to improve the situation, or preventive actions to forestall unfavourable conditions. A case study based on an actual quality control database is detailed. 相似文献
107.
Shane Y. Hong 《Journal of Intelligent Manufacturing》1993,4(3):233-241
One major bottleneck in the automation of the drilling process by robots in the aerospace industry is drill condition monitoring. This paper describes a system approach to solve this problem through the advancement of new machine design, sensor instrumentation, metal-cutting research, and intelligent software development. All drill failures can be detected and distinguished: chisel edge wear, flank wear, crater wear, margin wear, corner wear, breakage, asymmetry, lip height difference, and chipping at lips. However, in the real manufacturing environment, different workpiece materials, drill size, drill geometry, drill material, cutting speed, feed rate, etc. will change the criteria for judging the drill condition. The knowledge base used for diagnosing the drill failures requires a huge data bank and prior exhaustive testing. A self-learning scheme is therefore introduced to the machine in order to acquire the threshold history needed for automatic diagnosis by using the same new tool under the same drilling conditions. 相似文献
108.
采用锁相技术,对电子束曝光机工件台运动实现速度环的全数字控制。设计了数字差频积分回路和数字差频比例控制器,能有效消除速度的静态误差和改善系统的动态特性。 相似文献
109.
A response to criticism of threshold plates for the study of color vision developed at the Mendeleev All-Russia Research Institute
of Metrology and published in 1994 is presented. The critics base their conclusions on colorimetric testing and the examination
of the plates.
In response to the article by M. V. Danilova and J. D. Mollon [4].
__________
Translated from Izmeritel’naya Tekhnika, No. 1, pp. 37–39, January, 2007. 相似文献
110.
介绍了一种生产效率高、加工质量稳定、利用单片机控制液压传动系列带式输送机托辊管筒自动加工机床的设计过程。 相似文献