全文获取类型
收费全文 | 233990篇 |
免费 | 18158篇 |
国内免费 | 9960篇 |
专业分类
电工技术 | 12713篇 |
技术理论 | 10篇 |
综合类 | 15417篇 |
化学工业 | 37765篇 |
金属工艺 | 13686篇 |
机械仪表 | 14365篇 |
建筑科学 | 14551篇 |
矿业工程 | 5509篇 |
能源动力 | 5459篇 |
轻工业 | 15415篇 |
水利工程 | 4549篇 |
石油天然气 | 12186篇 |
武器工业 | 1586篇 |
无线电 | 25582篇 |
一般工业技术 | 33739篇 |
冶金工业 | 13981篇 |
原子能技术 | 5738篇 |
自动化技术 | 29857篇 |
出版年
2024年 | 915篇 |
2023年 | 3023篇 |
2022年 | 5958篇 |
2021年 | 8127篇 |
2020年 | 6182篇 |
2019年 | 5345篇 |
2018年 | 6557篇 |
2017年 | 7260篇 |
2016年 | 6784篇 |
2015年 | 7990篇 |
2014年 | 10463篇 |
2013年 | 12770篇 |
2012年 | 14160篇 |
2011年 | 15214篇 |
2010年 | 13431篇 |
2009年 | 13197篇 |
2008年 | 13077篇 |
2007年 | 12386篇 |
2006年 | 11726篇 |
2005年 | 9948篇 |
2004年 | 7839篇 |
2003年 | 7423篇 |
2002年 | 7975篇 |
2001年 | 7163篇 |
2000年 | 5670篇 |
1999年 | 4691篇 |
1998年 | 3528篇 |
1997年 | 2957篇 |
1996年 | 2646篇 |
1995年 | 2327篇 |
1994年 | 1898篇 |
1993年 | 1556篇 |
1992年 | 1469篇 |
1991年 | 1271篇 |
1990年 | 1255篇 |
1989年 | 1112篇 |
1988年 | 995篇 |
1987年 | 918篇 |
1986年 | 794篇 |
1985年 | 764篇 |
1984年 | 739篇 |
1981年 | 686篇 |
1979年 | 750篇 |
1978年 | 785篇 |
1977年 | 751篇 |
1976年 | 770篇 |
1975年 | 719篇 |
1974年 | 725篇 |
1973年 | 726篇 |
1972年 | 707篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
本文对多目标二次规划问题非劣解集的理论生成进行了探讨,在介绍二次规划单目标问题优化解求法的基础上,提出了在决策平面上互切点,共交点轨迹的概念.由此导出了非劣解集的一般解析式(对切点解问题)和另一类交点解问题时的非劣解集求法,然后介绍了在目标平面非劣解集的解析表达式.使多目标二次规划问题整个非劣解集的推求严格、明确和方便,有理论和实际意义。文中以一个综合利用水库参数的多目标优选作为例子阐述了应用,并求出了最终的最佳协调解. 相似文献
994.
Bor -Yir Chen Wei -Hsiung Wu Jiann -Ruey Chen Chum -Sam Hong 《Journal of Materials Science》1995,30(9):2254-2256
The temperature dependence characteristics of hydrogenated amorphous silicon thin-film transistors were investigated. The results indicate that as the temperature was increased, the threshold voltage and the field-effect mobility were first increased, and then decreased, which may be controlled by different mechanisms at low and high temperatures. In addition, if the temperature was higher than 420 K, the Fermi level was promoted to the degenerate-like states, the current channel always existed due to the temperature effect, and the threshold voltage became negative. 相似文献
995.
The process of mechanoluminescence transformation of a pulse pressure sensor is considered. The process consists in excitation
of emission under the action of mechanical loading. An algorithm for use in processing the output optical signal of the sensor
that makes it possible to determine an input shock pulse is presented.
__________
Translated from Izmeritel’naya Tekhnika, No. 10, pp. 28–31, October, 2007. 相似文献
996.
997.
随着Macha遥爆系统在地震勘探中使用年限的增加,该系统在工作中时常出现各种各样的故障,本文根据其日常检修记录,分析总结了Macha系统常见的十一例故障,并从故障的现象、分析、排除三个方面对各个故障进行了详细的介绍。 相似文献
998.
999.
A semi-Markov model is constructed that describes an arbitrarily structured multicomponent technological system and takes
into account its calendar maintenance. Using an aggregation algorithm, approximate values of stationary reliability characteristics
and an optimal term of maintenance work are determined for the system.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 69–86, March–April 2006. 相似文献
1000.
Floods cause environmental hazards and influence on socio‐economic activities. In this study, we evaluated the historic flood frequency at a confluence in the middle Yellow River, China. A non‐parametric, multivariate, empirical, orthogonal function matrix model, which consists of time correlation coefficients of flood discharge at different gauge stations and flood events was used for the analysis of flood frequency. The model addresses the characteristics of confluent floods such as frequency and the probability in multiple tributary rivers. Flood frequency analysis is often coupled with studies of hydrological routing processes that reduce the flood capacity of the rivers. Flood routing to the confluence were simulated using kinematic wave theory. Results of this flood frequency analysis showed that flooding frequency has intensified in the past 500 years, especially during the 19th century. Flooding in streams above the confluence was more frequent than in streams below the confluence. Over the last 2000 years, concurrent flooding in multiple tributary rivers accounted for 67.5% of the total flooding in the middle Yellow River. Simulation of flood routing processes shows that the decreased flooding capacity and elevated river bed of the shrunken main channel leads to an increased flood wave propagation time (24–52.3 h) in the study area after 1995. The model indicates that human activities, such as constructions of the Sanmenxia Dam, have changed flood routing boundary conditions and have contributed to the increased flood frequency at the confluence. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献