全文获取类型
收费全文 | 83457篇 |
免费 | 9301篇 |
国内免费 | 5010篇 |
专业分类
电工技术 | 13021篇 |
技术理论 | 14篇 |
综合类 | 6334篇 |
化学工业 | 10056篇 |
金属工艺 | 3313篇 |
机械仪表 | 3221篇 |
建筑科学 | 11483篇 |
矿业工程 | 2505篇 |
能源动力 | 13293篇 |
轻工业 | 2703篇 |
水利工程 | 2474篇 |
石油天然气 | 3579篇 |
武器工业 | 673篇 |
无线电 | 5663篇 |
一般工业技术 | 8302篇 |
冶金工业 | 4018篇 |
原子能技术 | 1420篇 |
自动化技术 | 5696篇 |
出版年
2024年 | 452篇 |
2023年 | 1783篇 |
2022年 | 2928篇 |
2021年 | 3284篇 |
2020年 | 3394篇 |
2019年 | 3095篇 |
2018年 | 2603篇 |
2017年 | 3119篇 |
2016年 | 3499篇 |
2015年 | 3399篇 |
2014年 | 5686篇 |
2013年 | 5532篇 |
2012年 | 6052篇 |
2011年 | 6839篇 |
2010年 | 5191篇 |
2009年 | 5285篇 |
2008年 | 4800篇 |
2007年 | 5283篇 |
2006年 | 4272篇 |
2005年 | 3389篇 |
2004年 | 2853篇 |
2003年 | 2351篇 |
2002年 | 2127篇 |
2001年 | 1802篇 |
2000年 | 1558篇 |
1999年 | 1251篇 |
1998年 | 990篇 |
1997年 | 809篇 |
1996年 | 723篇 |
1995年 | 565篇 |
1994年 | 504篇 |
1993年 | 416篇 |
1992年 | 316篇 |
1991年 | 276篇 |
1990年 | 232篇 |
1989年 | 186篇 |
1988年 | 158篇 |
1987年 | 115篇 |
1986年 | 94篇 |
1985年 | 117篇 |
1984年 | 100篇 |
1983年 | 58篇 |
1982年 | 84篇 |
1981年 | 43篇 |
1980年 | 47篇 |
1979年 | 31篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1959年 | 6篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
221.
Ir.H.E.M. Stassen 《Renewable Energy》1994,5(5-8)
Within the European Community, the interest in energy generation from biomass and waste is increasing. A brief overview is given of several thermal conversion technologies, of biomass production and waste availability in the Netherlands. Based on this, the possibilities for energy generation from biomass and waste in the Netherlands are evaluated. 相似文献
222.
This paper shows that possibilities exist for maintaining current energy-related carbon emissions per capita in Mexico at almost constant levels in the long term. It is argued, however, that the identified carbon emissions reductions will not be achieved easily or rapidly, as they require a restructuring of Mexico's current technological base and an unusual degree of coordination among the government, lending institutions, equipment manufacturers, and final users. Such changes also will entail surmounting major institutional and financial barriers and creating a better international environment for technology transfer and capital lending. 相似文献
223.
雾化水流计算模式 总被引:21,自引:1,他引:20
梁在潮 《水动力学研究与进展(A辑)》1992,7(3):247-255
本文描述了雾化水流现象并提出了雾化水流的一个计算模型。得出了雾化水流影响领域的各种不同的计算公式和方法。 相似文献
224.
总结了动力能源调度监控技术在冶金企业的应用情况,介绍了这项技术的发展历程及企业在应用时需要注意的几个重要事项,分析了目前存在的问题,提出了相应对策。 相似文献
225.
A restructured electricity system may undervalue renewable energy. We remain wary of unregulated markets, but urge the renewable energy community to begin considering how they could adapt to increasing customer choice. 相似文献
226.
Two subroutines have been developed which permit users of the TRNSYS programme to calculate the parameters of ambiental comfort (PMV and PPD).The first subroutine deals with the calculation of the view factors inside a room for all the values of the spatial coordinates and, thus, permits the average radiant temperature to be calculated in every position. The second subroutine has been developed in accordance with the indications of the ISO 7730 standard.Both subroutines have been validated and then interfaced to TRNSYS.The integrated programme has been utilised to compare the performances of different heating systems in terms of energy consumption and comfort, maintaining the temperature of the interior constant for different climatic conditions. 相似文献
227.
Reconstruction of a discontinuous function from a few fourier coefficients using bayesian estimation
Alex Solomonoff 《Journal of scientific computing》1995,10(1):29-80
The goal of this paper is the application of spectral methods to the numerical solution of conservation law equations. Spectral methods furnish estimates of the firstn Fourier coefficients of the solution. But since the solutions of conservation law equations can have discontinuities, the estimate of the solution by summing the firstn terms of the Fourier series will haveO(1/n) error, even if the Fourier coefficients are known to high accuracy. But if the solution could be accurately reconstructed from its Fourier coefficients, spectral methods could be used effectively in these problems. A method for doing this is to assume a probability distribution for functions. Functions which are smooth away from the discontinuity are assumed to be likely, and those which are not smooth away from the discontinuity are assumed to be unlikely. Then a reconstruction algorithm is chosen by minimizing the expected error over all algorithms. It is possible to put the smoothness assumptions mentioned earlier into an infinite-dimensional Gaussian probability distribution, and then the minimum-error algorithm is well-known and fairly simple to construct and apply. If the Fourier coefficients of the reconstructed function are known exactly, then this approach gives very good results. But when used with Fourier coefficients obtained from a spectral approximation to Burgers' equation, the results were much less impressive, probably because the coefficients were not known very accurately. It is possible to construct filters that reconstruct a function using Legendre or Chebyshev coefficients for information instead Fourier coefficients. It is found that the performance of these filters is similar to the Fourier case. 相似文献
228.
Standard Gibbs free energy of formation (ΔGf0), an important property needed in design calculations has been estimated using molar refraction, RM. The linear relationships derived between ΔGf0 and RM tested with the data on 8 series of hydrocarbons at 228 compounds yielded average deviations comparable to the methods cited in recent literature. The method can be used as an alternative to the existing ones, because of its simplicity combined with reasonable accuracy. 相似文献
229.
本文主要论述了面流消能五种典型流态近底紊动流速特性,总结出了近底时均流速和紊动强度沿程变化规律,提出了近底紊动流速可能出现的最大瞬时值及相应位置的计算公式。面流消能工程的下游防冲设计中考虑的主要水力参数之一是,消能段近底流速紊动可能出现的最大瞬时值及其相应的部位,但目前国内外研究成果较少。笔者通过水工模型试验重点研究了面流消能各典型流态近底流速及其紊动纵向分量沿程的变化规律,并提出了计算公式,为优化面流设计提供科学依据。 相似文献
230.
Typical methods of dehumidification of air circulating in the dehumidifying driers (indirect and direct cooler and partial exchange of the air) were analysed. Energy aspect of cooler operation was evaluated. The method for minimization of unit thermal energy consumption in a dehumidifying drier by the optimal selection of the cooler point was also given. Methods of the heat recovery of heat conveyed in a cooler lending to save energy (heat regeneration. expansion and compression of the air, a dehumidifier) were analysed. It was indicated that introduction of dehumidifiers into contemporary wood driers caused significant improvement of energy aspects of their operation 相似文献