全文获取类型
收费全文 | 423901篇 |
免费 | 33542篇 |
国内免费 | 18945篇 |
专业分类
电工技术 | 25884篇 |
技术理论 | 60篇 |
综合类 | 28392篇 |
化学工业 | 69020篇 |
金属工艺 | 24261篇 |
机械仪表 | 27539篇 |
建筑科学 | 32623篇 |
矿业工程 | 14047篇 |
能源动力 | 12245篇 |
轻工业 | 26672篇 |
水利工程 | 7811篇 |
石油天然气 | 27051篇 |
武器工业 | 3810篇 |
无线电 | 47138篇 |
一般工业技术 | 48029篇 |
冶金工业 | 22076篇 |
原子能技术 | 4501篇 |
自动化技术 | 55229篇 |
出版年
2024年 | 1705篇 |
2023年 | 6368篇 |
2022年 | 11551篇 |
2021年 | 16348篇 |
2020年 | 12492篇 |
2019年 | 10157篇 |
2018年 | 11569篇 |
2017年 | 13102篇 |
2016年 | 11837篇 |
2015年 | 16209篇 |
2014年 | 20833篇 |
2013年 | 25273篇 |
2012年 | 27429篇 |
2011年 | 30017篇 |
2010年 | 26448篇 |
2009年 | 25328篇 |
2008年 | 24967篇 |
2007年 | 24208篇 |
2006年 | 24452篇 |
2005年 | 21114篇 |
2004年 | 14003篇 |
2003年 | 11789篇 |
2002年 | 10650篇 |
2001年 | 9554篇 |
2000年 | 9623篇 |
1999年 | 10754篇 |
1998年 | 8845篇 |
1997年 | 7332篇 |
1996年 | 6852篇 |
1995年 | 5766篇 |
1994年 | 4721篇 |
1993年 | 3299篇 |
1992年 | 2683篇 |
1991年 | 2085篇 |
1990年 | 1600篇 |
1989年 | 1325篇 |
1988年 | 1079篇 |
1987年 | 720篇 |
1986年 | 567篇 |
1985年 | 354篇 |
1984年 | 260篇 |
1983年 | 216篇 |
1982年 | 209篇 |
1981年 | 144篇 |
1980年 | 150篇 |
1979年 | 80篇 |
1978年 | 41篇 |
1977年 | 48篇 |
1976年 | 74篇 |
1975年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry 相似文献
62.
63.
Gang Chen Zhonghua Yang Chor Ping Low 《Industrial Informatics, IEEE Transactions on》2006,2(4):269-280
In this paper, we address agent coordination from a dynamic systems perspective and propose a dynamic coordination model, which is inspired by biological metabolic systems. A new coordination mechanism through dynamic local adjustment (CDLA) is presented, and coordination is achieved when every agent utilizes explicitly the global system dynamics and performs iteratively a dynamic local adjustment procedure. The CDLA mechanism is investigated in an example multiagent shop floor system. The results show that the example manufacturing process is well-coordinated and the coordination approach is practically applicable and effective 相似文献
64.
65.
Jing Wang Walker D.M. Xiang Lu Majhi A. Kruseman B. Gronthoud G. Villagra L.E. van de Wiel P.J.A. Eichenberger S. 《Design & Test of Computers, IEEE》2007,24(3):226-234
Excessive power supply noise during test can cause overkill. This article discusses two models for supply noise in delay testing and their application to test compaction. The proposed noise models avoid complicated power network analysis, making them much faster than existing power noise analysis tools. can cause performance degradation and 相似文献
66.
本文分析了Seya-Namioka系统光学参数与离焦量的关系,为选取最佳光学参数提供了依据。同时,简要说明了影响谱线质量及波长读数精度的因素,并讨论了补偿波长读数误差的方法。 相似文献
67.
Spectral slope (S), describing the exponential decrease of the absorption spectrum over a given wavelength range, is an important parameter in the study of of chromophoric dissolved organic matter (CDOM) dynamics, and also an essential input parameter in remote sensing models. Furthermore, S is often used as a proxy for CDOM composition, including the ratio of fulvic to humic acids and molecular weight. The relative broad range in S values reported in the literature can be explained by the different spectral ranges and fitting methods used. A single exponential model is used to fit the S values for 17 investigations involving 458 samples in Lake Taihu from January to October in 2004. The average S value was 15.18 ± 1.39 μm−1 for the range of 280–500 nm, which fell within the range reported in the literature. The frequency distribution of S value basically obeyed a normal distribution. Significant differences in S values between summer and other seasons showed that phytoplankton degradation was one of the important sources of CDOM in summer, whereas CDOM mainly came from the river input in other seasons. Furthermore, the estimated S value decreased with increasing wavelength range used in regression. The maximum and minimum values derived from the regression were 17.89 ± 1.25 μm−1 and 13.62 ± 2.11 μm−1 for the wavelength ranges of 280–380 nm and 400–500 nm, respectively, a decrease of 23.9%. S values significantly decreased with the increase of CDOM absorption coefficients. CDOM absorption coefficients could be more appropriately estimated from exponential model introducing the variation of S with absorption coefficients, making them useful for a remote sensing bio-optical model of Lake Taihu. DOC-specific absorption coefficient a*(λ) and the parameter M describing molecular size of the humic molecules could also be used as a proxy for the sources and types of CDOM. A general relationship was found between S and a*(λ), and M values. S increased with the decrease of DOC-specific absorption coefficient and the increase of M corresponding to the decrease of molecular weight. 相似文献
68.
69.
Hybrid techniques are effective for exploring interesting corner cases, coverage holes, invariant variations, and so forth, in the general area of directed functional validation. However, despite the emergence of several effective hybrid validation techniques, several questions still remain. The five articles in this special issue help explain some of the different facets of this area. 相似文献
70.
Alkali-metal carbonate salts meet the requirements for high-temperature solar central receiver systems, but because of their corrosiveness they present special problems in the design of storage tanks. In order to reduce corrosion and temperature sufficiently to retain strength in the storage containing wall, internal and thermal insulation is required. We present design options and operation criteria for sensible-heat, molten-salt storage with internal insulation. 相似文献