全文获取类型
收费全文 | 37912篇 |
免费 | 3984篇 |
国内免费 | 2121篇 |
专业分类
电工技术 | 1692篇 |
技术理论 | 2篇 |
综合类 | 2869篇 |
化学工业 | 7869篇 |
金属工艺 | 2138篇 |
机械仪表 | 1120篇 |
建筑科学 | 3681篇 |
矿业工程 | 1912篇 |
能源动力 | 3444篇 |
轻工业 | 794篇 |
水利工程 | 5439篇 |
石油天然气 | 3023篇 |
武器工业 | 173篇 |
无线电 | 3141篇 |
一般工业技术 | 3244篇 |
冶金工业 | 1101篇 |
原子能技术 | 322篇 |
自动化技术 | 2053篇 |
出版年
2024年 | 121篇 |
2023年 | 533篇 |
2022年 | 842篇 |
2021年 | 1076篇 |
2020年 | 1130篇 |
2019年 | 1069篇 |
2018年 | 931篇 |
2017年 | 1242篇 |
2016年 | 1356篇 |
2015年 | 1346篇 |
2014年 | 2125篇 |
2013年 | 2376篇 |
2012年 | 2663篇 |
2011年 | 2877篇 |
2010年 | 2149篇 |
2009年 | 2098篇 |
2008年 | 2108篇 |
2007年 | 2433篇 |
2006年 | 2364篇 |
2005年 | 1959篇 |
2004年 | 1725篇 |
2003年 | 1546篇 |
2002年 | 1366篇 |
2001年 | 1217篇 |
2000年 | 975篇 |
1999年 | 837篇 |
1998年 | 653篇 |
1997年 | 561篇 |
1996年 | 477篇 |
1995年 | 401篇 |
1994年 | 290篇 |
1993年 | 257篇 |
1992年 | 234篇 |
1991年 | 153篇 |
1990年 | 120篇 |
1989年 | 105篇 |
1988年 | 76篇 |
1987年 | 82篇 |
1986年 | 31篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1959年 | 4篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
151.
用层次分析法(AHP)确定煤和瓦斯突出中的有关参数 总被引:1,自引:0,他引:1
介绍了井下瓦斯突出的原因 ,详细阐述了瓦斯突出的有关参数的确定方法。 相似文献
152.
P. T. Tsilingiris 《国际能源研究杂志》1991,15(9):723-730
The paper describes the calculation of the beam solar radiation transmission across the uniform salinity upper convecting zone (UCZ) and the salinity stratified gradient zone (GZ), when the extinction coefficient is not only wavelength but also salinity-concentration dependent, assuming that the effect of scattering to be negligible. The results are useful in determining the effects of dissolved salt ions on pure water transmission, at least according to the existing measured data in the literature. 相似文献
153.
航空齿轮表面硬化层断裂性能研究 总被引:1,自引:0,他引:1
按照航空齿轮的具体工艺过程,对材料12Cr2Ni4A的拉伸试样和断裂试样进行设计和加工,通过三点弯曲实验,重点研究了齿轮材料硬化层的硬度分布,硬化试样拉伸力学性能参数和断裂性能参数,实验结果表明,所采用试样的加工工艺方案是可行的,所获得的Kc基本反映我国航空硬化齿轮材料的断裂性能特征,为定量预测航空硬化齿轮疲劳寿命提供实验和理论分析的依据。 相似文献
154.
A compact lumped‐element equivalent circuit model of two‐layer integrated spiral inductors on silicon substrates is developed in this article. Based on this proposed model, excellent agreements are achieved between the measured and simulated S‐parameters for different inductors. Also, both self‐ and mutual inductances of two‐layer inductors are accurately extracted, and their overall performances are understood clearly. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 148–153, 2003. 相似文献
155.
《Drying Technology》2007,25(7):1175-1183
Although considerable progress has been made in the development of experimental techniques for investigating velocity distribution inside a fixed bed, these techniques were limited to special cases. Consequently, the velocity distribution is normally measured at downstream of the fixed bed and then this measurement is considered to be representative for the flow inside the bed. To evaluate the representativeness of this technique, this work presents a study of the change in the flow characteristics, starting from the boundary of the fixed bed within the pipe to a downstream position where the experimental measurement is taken, by using simulations based on computational fluid dynamics methods. 相似文献
156.
157.
L.J. Webb 《Water research》1985,19(8):969-974
Wastewaters from the manufacture of pulp and paper have given rise to problems of excessive microbial growth in rivers over a number of years. This paper is the first in a series of four articles describing research undertaken by PIRA at four U.K. paper/board mills (one integrated with pulp production) over the period 1978–1980. This first paper briefly reviews the published literature on sewage fungus growth from pulp and paper mill discharges up to 1978, but mainly describes previously unpublished work undertaken by PIRA over the period 1965–1975. This introductory paper thus provides a state-of-the-art review of methods to control sewage fungus growth from pulp and paper mill effluents prior to commencement of the research described in the following three articles. 相似文献
158.
钱塘江光缆管穿越长度2454.15m,穿越深度为32m,穿越中采用了多项新技术、新工艺、新方法。文章介绍了导向孔对穿技术、套管技术、水下磁场电缆铺设技术、长距离泥浆回流技术、长距离穿越钻杆组合技术在钱塘江光缆管穿越施工中的应用。 相似文献
159.
In order to increase the efficiency of waste utilization in thermal conversion processes, pre-treatment is advantageous. With the Herhof Stabilat® process, residual domestic waste is upgraded to waste-derived fuel by means of biological drying and mechanical separation of inerts and metals. The dried and homogenized waste-derived Stabilat® fuel has a relatively high calorific value and contains high volatile matter which makes it suitable for gasification. As a result of extensive mechanical treatment, the Stabilat® produced is of a fluffy appearance with a low density. A two-stage gasifier, based on a parallel-arranged bubbling fluidized bed and a fixed bed reactor, has been developed to convert Stabilat® into hydrogen-rich product gas. This paper focuses on the design and construction of the configured laboratory-scale gasifier and experience with its operation. The processing of low-density fluffy waste-derived fuel using small-scale equipment demands special technical solutions for the core components as well as for the peripheral equipment. These are discussed here. The operating results of Stabilat® gasification are also presented. 相似文献
160.
Wang Xing-kui Li Dan-xun Qu Zhao-song Wang Dian-chang Department of Hydraulic Engineering Tsinghua University Beijing China 《水动力学研究与进展(B辑)》2001,(1)
1 . INTRODUCTIONThebedloadtransporthasbeenextensivelystudiedinthepastfewdecadesandmanyformulasforpredictingbedloadtransportratehavebeenpresented(Einstein 1950 ;Meyer Peter 194 8;Bagnold 1973;Engelund 1976;Yalin 1972 ;Samaga 1986;andKarim 1998) .Whenappliedtostreamswithpartial… 相似文献