全文获取类型
收费全文 | 20793篇 |
免费 | 1263篇 |
国内免费 | 861篇 |
专业分类
电工技术 | 528篇 |
综合类 | 724篇 |
化学工业 | 3205篇 |
金属工艺 | 1345篇 |
机械仪表 | 2576篇 |
建筑科学 | 873篇 |
矿业工程 | 784篇 |
能源动力 | 1148篇 |
轻工业 | 663篇 |
水利工程 | 158篇 |
石油天然气 | 406篇 |
武器工业 | 115篇 |
无线电 | 1268篇 |
一般工业技术 | 1601篇 |
冶金工业 | 1025篇 |
原子能技术 | 156篇 |
自动化技术 | 6342篇 |
出版年
2024年 | 36篇 |
2023年 | 191篇 |
2022年 | 285篇 |
2021年 | 433篇 |
2020年 | 446篇 |
2019年 | 396篇 |
2018年 | 405篇 |
2017年 | 534篇 |
2016年 | 640篇 |
2015年 | 789篇 |
2014年 | 1231篇 |
2013年 | 1444篇 |
2012年 | 1205篇 |
2011年 | 1796篇 |
2010年 | 1058篇 |
2009年 | 1189篇 |
2008年 | 1094篇 |
2007年 | 1321篇 |
2006年 | 1209篇 |
2005年 | 1127篇 |
2004年 | 922篇 |
2003年 | 870篇 |
2002年 | 725篇 |
2001年 | 536篇 |
2000年 | 505篇 |
1999年 | 450篇 |
1998年 | 387篇 |
1997年 | 301篇 |
1996年 | 269篇 |
1995年 | 220篇 |
1994年 | 238篇 |
1993年 | 140篇 |
1992年 | 112篇 |
1991年 | 84篇 |
1990年 | 68篇 |
1989年 | 47篇 |
1988年 | 55篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
本文运用“软科学”一即通过建立数学模型,进行系统分析和系统优化,阐述对蒸汽管网优化运行的方法及原理,达到提高供热效率及节能降耗的目的. 相似文献
104.
105.
Jamshid Mohammadi 《Structural Safety》1985,2(4):301-308
Lifeline systems are vulnerable to two types of hazards arising from potential earthquake sources. These are the hazard of a fault-rupture strike on elements of a lifeline system and the hazard of overstress induced in different elements of the system because of the ground vibration. An optimum design method is presented in this paper for the design of a lifeline system for a maximum accepted probability of failure because of any of the two modes of failure. The method may be used to determine an optimum path between a number of fixed points which represent supply or demand stations in the system. 相似文献
106.
CEN Jun-bo CHEN Wei-min LI Hui HUANG Shang-lian 《半导体光子学与技术》2005,11(3):212-216
In order to develop competitive and high performance/cost ratio of digital binoculars, design scheme should be optimized in term of technical capacity, economic benefit, product performance, risk management, etc. The common optimization method is limited in qualitative analysis, and the parameter optimization method is limited in obtaining optimal parameter only from technical side. Each method has its limitation. Based on the analysis of digital binoculars parameters, optional design schemes are laid down.Analytic hierarchy process combined the qualitative analysis with the quantitative analysis together. The design schemes are optimized, and result is worked out. 相似文献
107.
模式识别催化剂生产调优 总被引:2,自引:0,他引:2
王景芳 《计算机与应用化学》1992,9(4):260-266
本文介绍如何将模式识别应用于生产调优,着重讨论了多指标(优化目标)因素的分级,提出了用模糊综合评价度量和依有序聚类最小损失函数准则划类,并相继进行变量与样本筛选、信息压缩、特征提取和模拟仿真获得优区操作条件,实施效果显著。 相似文献
108.
浮点加法器是协处理器的核心运算部件,是实现浮点指令各种运算的基础,其设计优化是提高浮点运算速度和精度的关键途径。文章从浮点加法器算法和电路实现的角度给出设计方法,并且提出动态与静态结合设计进位链的方案以及前导O预测面积与速度的折衷方法。动态与静态结合设计进位链的方法有效地降低了功耗,提高了速度,改善了性能。目前已经嵌入协处理器的设计中,并且流片测试成功。 相似文献
109.
Celso M. F. Lapa Cludio M. N. A. Pereira Paulo F. Frutuoso e Melo 《Reliability Engineering & System Safety》2003,81(1):103-109
In order to maximize systems average availability during a given period of time, it has recently been developed a non-periodic surveillance test optimization methodology based on genetic algorithms (GA). The fact of allowing non-periodic tests turns the solution space much more flexible and schedules can be better adjusted, providing gains in the overall system average availability, when compared to those obtained by an optimized periodic test scheme. This approach, however, turns the optimization problem more complex. Hence, the use of a powerful optimization technique, such as GA, is required.Considering that some particular features of certain systems can turn it advisable to introduce other specific constraints in the optimization problem, this work investigates the application of seasonal constraints for the set of the Emergency Diesel Generation of a typical four-loop pressurized water reactor in order to planning and optimizing its surveillance test policy. In this analysis, the growth of the blackout accident probability during summer, due to electrical power demand increases, was considered. Here, the used model penalizes surveillance test interventions when the blackout probability is higher.Results demonstrate the ability of the method in adapting the surveillance test policy to seasonal constraints. The knowledge acquired by the GA during the searching process has lead to test schedules that drastically minimize test interventions at periods of high blackout probability. It is compensated by more frequent redistributed tests through the periods of low blackout probability in order to improve on the overall average availability at the system level. 相似文献
110.
An integrated process based on simultaneous solid-liquid extraction and liquid membrane separation is proposed for recovery and isolation of valuable species from botanicals. This integration provides complete exhausting of the solid material even in the case of very low solubility of the specified solute in the extracting solvent. Selectivity of the liquid membrane ensures a preferential transport of the desired solute from the native extract into the strip solution, while the other co-extracted species remain predominantly in the native extract. 相似文献