全文获取类型
收费全文 | 12349篇 |
免费 | 1524篇 |
国内免费 | 370篇 |
专业分类
电工技术 | 194篇 |
综合类 | 1009篇 |
化学工业 | 3891篇 |
金属工艺 | 589篇 |
机械仪表 | 119篇 |
建筑科学 | 1487篇 |
矿业工程 | 931篇 |
能源动力 | 257篇 |
轻工业 | 322篇 |
水利工程 | 426篇 |
石油天然气 | 212篇 |
武器工业 | 18篇 |
无线电 | 153篇 |
一般工业技术 | 596篇 |
冶金工业 | 3935篇 |
原子能技术 | 24篇 |
自动化技术 | 80篇 |
出版年
2024年 | 63篇 |
2023年 | 197篇 |
2022年 | 417篇 |
2021年 | 436篇 |
2020年 | 463篇 |
2019年 | 310篇 |
2018年 | 344篇 |
2017年 | 507篇 |
2016年 | 561篇 |
2015年 | 505篇 |
2014年 | 825篇 |
2013年 | 682篇 |
2012年 | 961篇 |
2011年 | 939篇 |
2010年 | 706篇 |
2009年 | 708篇 |
2008年 | 547篇 |
2007年 | 769篇 |
2006年 | 671篇 |
2005年 | 572篇 |
2004年 | 471篇 |
2003年 | 358篇 |
2002年 | 354篇 |
2001年 | 345篇 |
2000年 | 250篇 |
1999年 | 261篇 |
1998年 | 186篇 |
1997年 | 132篇 |
1996年 | 119篇 |
1995年 | 111篇 |
1994年 | 87篇 |
1993年 | 72篇 |
1992年 | 55篇 |
1991年 | 40篇 |
1990年 | 43篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
钢渣沥青混凝土技术及其应用研究进展 总被引:1,自引:0,他引:1
钢渣常被当成工业废弃物处置,但其碱性强、棱角丰富,兼具有优异的力学特性,可以改善沥青混凝土的抗水损害、抗高温变形以及耐磨和抗滑等性能,被认为是可替代天然矿质集料的理想筑路材料。近年来道路建设对集料用量的高需求与天然集料短缺之间的矛盾越来越突出,钢渣沥青混凝土技术因而成为备受关注的热点。概述了钢渣的材料特性以及钢渣沥青混凝土的设计与性能,介绍了钢渣沥青混凝土的实际应用情况,研究了钢渣沥青混凝土长期应用后的路面性能变化,最后对钢渣沥青混凝土未来的发展趋势进行了展望。 相似文献
74.
Hossam F. H. Abdelfattah Khalid Al-Shamsi Khalifa Al-Jabri 《International Journal of Pavement Engineering》2018,19(7):630-640
Copper slag (CS) is a by-product of the copper extraction process, which can be used as coarse and/or fine aggregate in hot mix asphalt (HMA) pavements. This study used CS as a replacement of the fine aggregate with a percentage of up to 40% by total aggregate weight. The objective of this study was to evaluate the effect of CS on the rutting potential of the asphalt concrete mix using two methods. One method is based on the Dynamic modulus |E*| testing result. Actual pavement temperature data from a test section were used with the developed |E*| master curves. EverStressFE finite element program was used to perform a linear elastic load-deformation analysis for a pavement section and to determine the vertical resilient strain in a 40-mm HMA surface layer. The M-E PDG permanent deformation model was used with and Excel Visual Basic for Applications code to predict the accumulated rutting for different CS mixes for 10 million ESALs. The other method used the data from the flow number (FN) test. Based on the |E*| approach, the results indicated that adding 5% CS in the mix increased the predicted rutting from 0.59 to 0.98 mm at 10 million ESALs (increase by 68%). When 40% CS was used, rutting increased by more than 700% compared with the control mix. After analysing the FN results with the Francken model, the results indicated a decrease in FN as CS content is increased, indicating higher rutting potential. The decrease in FN ranged from 9% for 5% CS to 95% for 40% CS. The mixes containing up to 10% CS satisfied the minimum FN criteria for rutting. A calibration process for the M-E PDG distress prediction models that allows the use of waste and by-product materials such as CS should be considered in the future. 相似文献
75.
一次风反切系统的数值模拟和多相流动特性分析 总被引:12,自引:6,他引:6
四角切圆燃烧锅炉,存在着稳燃和结渣的矛盾,一次风微反切技术已在多台锅炉上得到应用,较好地解决了这对矛盾并能在一定程度上降低NOx的排放量。本文把湍流理论和多相流动理论应用于炉内空气动力场的计算机数值模拟,用投影法编制的计算软件对600MW锅炉炉内流动进行了计算,得出了一次风反切系统中炉内速度场、实际切圆、颗粒运动轨迹等结果,与冷炉和冷模试验基本吻合,对一次风反切系统的设计和调试具有参考价值。 相似文献
76.
介绍高炉INBA法渣处理工作原理和转鼓自动控制故障和自动控制故障的方法,以及INBA自动控制改造措施与故障的解决方法。 相似文献
77.
78.
79.
Fredrick J. Guya 《Lakes & Reservoirs: Research and Management》2013,18(2):129-143
Land‐use changes have been implicated a lot in the eutrophication of many lakes while forgetting the role of internal loading as influenced by the hydrological regimes of a given lake. The phosphorus loading of Nyanza Gulf is influenced both by internal and external loading with the internal loading playing a greater role in its eutrophication. The shear on the Apatite Phosphorus (AP) rich residual rock in the western end of the gulf through strong currents across the Rusinga Channel erodes the rock into non‐apatite inorganic phosphorus (NAIP) which is readily available for primary productivity. The current suspends the phosphorus rich apatite sediment together with the reserved phosphorus within sediments to the water column. The NAIP concentration on the western end of the gulf is exceptionally high, >1500 mg kg?1, and together with the hydrological forcing; is believed to be the driving force of Nyanza Gulf eutrophication. External loading through rivers and municipal discharges exacerbates the problem. The external loading mainly influences the inner gulf on the eastern shore while the internal loading affects mainly the western end of the gulf. Nyanza Gulf eutrophication can be managed by adopting the following measures: (i) the Mbita Causeway needs to be opened and a bridge erected in its place in order to reduce the strong current through the Rusinga Channel and the residence time within the gulf, by increasing the flushing rates; (ii) the farming communities within the basin need to be sensitized on the controlled use of fertilizers; (iii) the municipal wastes should be treated to tertiary level before discharge into the lake; and (iv) reduce erosion within the basin through re/afforestation. 相似文献
80.
Gertrud K. Nürnberg Lewis A. Molot Eavan O'Connor Hamdi Jarjanazi Jennifer Winter Joelle Young 《Journal of Great Lakes research》2013
Hypoxia and cyanobacterial blooms were extensive in Lake Simcoe during the 1980s and are still a problem to a lesser degree despite extensive nutrient load reduction from the catchment basin. The continuing signs of productivity indicate a potential internal phosphorus (P) source. Internal P load, as a redox-dependent release from bottom sediments, is hard to determine in a large, relatively shallow and partially unstratified lake such as Lake Simcoe. Of the lake's three major basins, only Kempenfelt Bay stratifies long enough to develop hypoxia in the stagnant summer hypolimnion. The following indications of sediment P release are available from historic data: 1) hypolimnetic hypoxia still occurs in Kempenfelt Bay although the hypoxic factor (number of days that an area equal to the bay's surface area is overlain by water of ≤ 2 mg/L dissolved oxygen, DO) has decreased substantially and significantly from 15.8 d/yr (1980–1994) to 4.0 d/yr (1995–2011); 2) hypoxic factors for other lake sections and at different DO levels also indicate widespread hypoxia; 3) concentrations of redox dependent metals, Fe and Mn, increase with depth; and 4) euphotic zone P and chlorophyll concentrations increase and water clarity decreases during fall turnover. Cyanobacterial blooms appear to occur in response to internal load as supported by occasional cyanobacteria counts. These indicators provide evidence that internal loading is likely occurring and affecting the water quality in Lake Simcoe. We expect that further monitoring, specific for internal load, will corroborate these results. 相似文献