全文获取类型
收费全文 | 32567篇 |
免费 | 4266篇 |
国内免费 | 724篇 |
专业分类
电工技术 | 2333篇 |
技术理论 | 2篇 |
综合类 | 2198篇 |
化学工业 | 7842篇 |
金属工艺 | 182篇 |
机械仪表 | 460篇 |
建筑科学 | 1257篇 |
矿业工程 | 15824篇 |
能源动力 | 2462篇 |
轻工业 | 57篇 |
水利工程 | 175篇 |
石油天然气 | 826篇 |
武器工业 | 8篇 |
无线电 | 178篇 |
一般工业技术 | 475篇 |
冶金工业 | 1865篇 |
原子能技术 | 37篇 |
自动化技术 | 1376篇 |
出版年
2024年 | 46篇 |
2023年 | 158篇 |
2022年 | 686篇 |
2021年 | 1126篇 |
2020年 | 1273篇 |
2019年 | 699篇 |
2018年 | 761篇 |
2017年 | 685篇 |
2016年 | 954篇 |
2015年 | 1169篇 |
2014年 | 2433篇 |
2013年 | 2096篇 |
2012年 | 3528篇 |
2011年 | 2888篇 |
2010年 | 2056篇 |
2009年 | 2065篇 |
2008年 | 1864篇 |
2007年 | 2053篇 |
2006年 | 1751篇 |
2005年 | 1495篇 |
2004年 | 1151篇 |
2003年 | 1099篇 |
2002年 | 845篇 |
2001年 | 842篇 |
2000年 | 675篇 |
1999年 | 530篇 |
1998年 | 372篇 |
1997年 | 361篇 |
1996年 | 294篇 |
1995年 | 252篇 |
1994年 | 191篇 |
1993年 | 104篇 |
1992年 | 101篇 |
1991年 | 57篇 |
1990年 | 39篇 |
1989年 | 28篇 |
1988年 | 39篇 |
1987年 | 30篇 |
1986年 | 21篇 |
1985年 | 187篇 |
1984年 | 223篇 |
1983年 | 169篇 |
1982年 | 145篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
The Wabash River Integrated Methanol and Power Production from Clean Coal Technologies (IMPPCCT) project is investigating an Early Entrance Coproduction Plant (EECP) concept to evaluate integrated electrical power generation and methanol production from coal and other carbonaceous feedstocks. Research, development and testing (RD&T) that is currently being conducted under the project is evaluating cost effective process systems for removing contaminants, particularly sulfur species, from the generated gas which contains mainly synthesis gas (syngas), CO2 and steam at concentrations acceptable for the methanol synthesis catalyst. The RD&T includes laboratory testing followed by bench-scale and field testing at the SG Solutions Gasification Plant located in West Terre Haute, Indiana. Actual synthesis gas produced by the plant was utilized at system pressure and temperature for bench-scale field testing. 相似文献
13.
通过小规模爆破试验,用线性回归方法对块煤进行筛分分析,指出影响炮采工作面块煤率的因素是炸药性能、装药结构、爆破参数、起爆顺序、时间间隔等。 相似文献
14.
旋风燃烧器冷态模型内颗粒运动轨迹计算 总被引:2,自引:0,他引:2
在冷态模型流场内,考虑气流对粉煤颗粒的气动阻力,建立其运动微分方程式。通过计算,得到九种粒径的颗粒在流场中的运动轨迹、停留时间、着膜位置和气-固相相对速度与该燃烧器几何参数和气动参数的关系,为燃烧器的深入研究提出了建议。 相似文献
15.
There have been extensive attempts in recent years to perform spatial equilibrium analysis of commodity markets, particularly that of energy. Most of these attempts have been based on linear programming transportation models, and more recently quadratic programming models. Unfortunately, neither of these modelling approaches can deal with the case of multi-commodity analysis with non-symmetric regression coefficients. In this paper, we overcome this problem by employing the linear complementarity programming model. In addition, we show how the model can be applied to coal and gas energy flows within a single region. Future potential applications of the model are also implied. 相似文献
16.
An examination of the influence of pressure and heating rate on the thermoplastic properties of a weakly coking coal and of coal with various pitch-like additives was carried out using a high pressure dilatometer. Pressure up to 4 MPa markedly increased the swelling properties and increased the plastic range by decreasing the softening temperature, but the effects of pressure were strongly influenced by rate of heating with high heating rates enhancing the effects. Additions of tar or pitch also enhanced swelling at low pressure. The solid carbonization residues from the dilatometer were examined by polarized light microscopy to determine the content and composition of optically anisotropic species. The anisotropic content was increased by increases in pressure and heating rate and pitch additives enhanced the anisotropic content, especially at low pressure, without affecting the composition of the anisotropy. No direct correlations exist between the dilatometric parameters and the optical anisotropy but their dependence on the conditions emphasizes that when considering high pressure gasification of coal, it is necessary to obtain data under appropriate conditions. 相似文献
17.
18.
Microwave plasma is studied as an alternative to oil or gas fuel for ignition and stabilisation of burning of lean coal. The study is performed on an experimental set-up, which includes a burner with a microwave plasma generator, coal and air supply systems, and measurement equipment. Power and thermochemical characteristics of the coal-plasma interaction have been measured and analysed. The obtained results indicate an essential intensification of ignition and combustion processes in the microwave burner compared to those in conventional burners. In particular, it has been demonstrated that the microwave energy consumption is only about 10% of the required expenditure of oil or gas, measured in heat equivalent. A design of an industrial microwave-plasma burner is proposed. Prospects of such burner for applications at industrial boilers of power plants are discussed. 相似文献
19.
A suite of density-differentiated macerals from several coals was analysed by Fourier transform infrared spectroscopy to obtain information on the nature and magnitude of the variations exhibited by the various maceral fractions. The most characteristic change between maceral groups was the variation in aliphatic hydrogen content, with exinite ? vitrinite ? inertinite. Since the separation technique (density gradient centrifugation) generally provided a number of fractions within a maceral group region, some of these were also analysed. In a series of density fractions from a low rank vitrinite, it was found that the aliphatic hydrogen content decreased as the density increased. The inertinites also exhibited a decrease in aliphatic hydrogen. The inertinite C—O bands had extinction coefficients different from those of vitrinites or exinites. The data suggest that quite profound variations in organic structure as determined by FT-i.r. spectroscopy can exist within a maceral group, so that for the most critical work on coals it is necessary to take this into account. 相似文献
20.
The relations between coke yields and the volatile matter content of 30 individual and 30 blended coals were investigated. Coke yields and deposited carbon related to volatile matter content can be expressed in the following equations: CY (%) = 97.89?0.86 VMch+VMc; and DC (%)= ?2.24+0.16 VMch; where: CY=real coke yield; VMch = volatile matter content of charging coal; VMc=volatile matter content of coke, and in the case of <2%; DC = deposited carbon. The test results show excellent correlation with practice. 相似文献