全文获取类型
收费全文 | 67708篇 |
免费 | 5474篇 |
国内免费 | 3024篇 |
专业分类
电工技术 | 3957篇 |
技术理论 | 8篇 |
综合类 | 4427篇 |
化学工业 | 11518篇 |
金属工艺 | 3815篇 |
机械仪表 | 4281篇 |
建筑科学 | 5753篇 |
矿业工程 | 1979篇 |
能源动力 | 1978篇 |
轻工业 | 4243篇 |
水利工程 | 1227篇 |
石油天然气 | 4743篇 |
武器工业 | 486篇 |
无线电 | 7374篇 |
一般工业技术 | 8420篇 |
冶金工业 | 3228篇 |
原子能技术 | 766篇 |
自动化技术 | 8003篇 |
出版年
2024年 | 245篇 |
2023年 | 1104篇 |
2022年 | 1909篇 |
2021年 | 2641篇 |
2020年 | 2037篇 |
2019年 | 1756篇 |
2018年 | 1962篇 |
2017年 | 2231篇 |
2016年 | 2011篇 |
2015年 | 2534篇 |
2014年 | 3414篇 |
2013年 | 3887篇 |
2012年 | 4334篇 |
2011年 | 4687篇 |
2010年 | 4130篇 |
2009年 | 3899篇 |
2008年 | 3772篇 |
2007年 | 3667篇 |
2006年 | 3750篇 |
2005年 | 3223篇 |
2004年 | 2176篇 |
2003年 | 1962篇 |
2002年 | 1709篇 |
2001年 | 1646篇 |
2000年 | 1713篇 |
1999年 | 1829篇 |
1998年 | 1428篇 |
1997年 | 1209篇 |
1996年 | 1081篇 |
1995年 | 973篇 |
1994年 | 791篇 |
1993年 | 568篇 |
1992年 | 442篇 |
1991年 | 343篇 |
1990年 | 317篇 |
1989年 | 229篇 |
1988年 | 178篇 |
1987年 | 107篇 |
1986年 | 106篇 |
1985年 | 61篇 |
1984年 | 41篇 |
1983年 | 26篇 |
1982年 | 33篇 |
1981年 | 23篇 |
1980年 | 13篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
A method for observing the three-dimensional morphologies of inclusions by deeply eroding a steel sample with a kind of organic solution composed of bromine water,acetone,and HC1 (volume ratio,45∶45∶10... 相似文献
134.
In this paper, we consider the partial pole assignment problem (PPAP) for high order control systems. It is shown that solving the PPAP is essentially solving a pole assignment for a linear system of a much lower order, and the robust PPAP is then concerning the robust pole assignment problem for this linear system. Based on this theory, a rather simple algorithm for solving the robust PPAP is proposed, and numerical examples show that this algorithm does lead to comparable results with earlier algorithms, but at much lower computational cost. 相似文献
135.
Jun-Qiu Jiang Kun Wang Xue-Xuan Peng Qing-Liang Zhao Yun-Shu Zhang Xiu-Dong Zhou 《哈尔滨工业大学学报(英文版)》2013,20(4):1-6
This paper compared the degradation efficiency of sludge organic matters and electric-production by two typical microbial fuel cells——dual-chamber microbial fuel cell(DMFC)and single chamber air cathode microbial fuel cell(SAMFC),and the variations of sludge protein,polysaccharide and ammonia nitrogen within the systems were also investigated.The results showed that the concentration of sludge soluble chemical oxygen demand,protein and carbohydrate of DMFC are higher than these of SAMFC during the systems operation,while DMFC can achieve a better ammonia nitrogen removal than SAMFC.Under the same operation condition,the stable voltage output of DMFC and SAMFC is 0.61 V and 0.37 V;the maximum power density of DMFC and SAMFC is 2.79 W/m3and 1.25 W/m3;TCOD removal efficiency of DMFC and SAMFC is 34.14%and 28.63%for 12 d,respectively.Meanwhile,DMFC has a higher coulomb efficiency than SAMFC,but both are less than5%.The results showed that DMFC present a better performance on sludge degradation and electric-production. 相似文献
136.
孟政 《武汉理工大学学报(材料科学英文版)》2013,28(1):79-81
The oxidation state of sulfur is detected in Na2O-CaO-SiO2 float glass by synchrotron radiation X-ray absorption near edge structure (XANES) spectra at the sulfur K edge. The measured spectra show the only presence of S6+ in the Na2O-CaO-SiO2 float glass and the oxidation state of sulfur do not change with the increase of glass depth. It is also found that, after the melt has gone through the molten tin bath, the S6+ is the dominant species, but S2- is also present on both surfaces. It is not certain whether cation bonds to S2- or not, because there are many cations dissolved in the melted tin which makes the spectrum complicated. 相似文献
137.
In this paper, we propose an efficient simulation-based two-stage scheduling methodology by integrating vector ordinal optimization (VOO) and response surface methodology (RSM) to make a good scheduling policy for fab operation. The suggested method combines local and global rules into a single rule, with the objective of simultaneously optimizing multiple performance indices. Our approach consists of 2 stages: rule combination selection, and parameter optimization. In the first stage, we apply the VOO techniques to effectively selecting good rule combination. Results show that 1 orders of computation time reduction over traditional simulations can be achieved. In the second stage, we adopt RSM and desirability function to tune the parameters associated to scheduling algorithm. The proposed approach is validated by means of a comparison with other scheduling policies. The results show that the proposed scheduling method is effective. 相似文献
138.
139.
应用Menke条件,在改性高岭土固体酸催化下,甲苯能被浓硝酸对位选择性硝化,表现在对邻硝化产物比例达到1.5。 相似文献
140.
同时考虑联轴器和轴承的不对中效应,建立了转子-轴承系统的动力学模型,分析了不对中对轴承动静特性,如负荷分配、刚度阻尼系数等的影响。结果表明,转子系统的不对中对轴承特性的影响不可忽略。 相似文献