全文获取类型
收费全文 | 577458篇 |
免费 | 6345篇 |
国内免费 | 1534篇 |
专业分类
电工技术 | 10390篇 |
综合类 | 390篇 |
化学工业 | 87674篇 |
金属工艺 | 27158篇 |
机械仪表 | 19876篇 |
建筑科学 | 11604篇 |
矿业工程 | 4939篇 |
能源动力 | 14288篇 |
轻工业 | 35684篇 |
水利工程 | 7256篇 |
石油天然气 | 16916篇 |
武器工业 | 36篇 |
无线电 | 62495篇 |
一般工业技术 | 126384篇 |
冶金工业 | 98030篇 |
原子能技术 | 16418篇 |
自动化技术 | 45799篇 |
出版年
2021年 | 5542篇 |
2020年 | 4276篇 |
2019年 | 5432篇 |
2018年 | 9775篇 |
2017年 | 9970篇 |
2016年 | 10639篇 |
2015年 | 6254篇 |
2014年 | 10576篇 |
2013年 | 26883篇 |
2012年 | 16206篇 |
2011年 | 21267篇 |
2010年 | 17069篇 |
2009年 | 19212篇 |
2008年 | 19656篇 |
2007年 | 19227篇 |
2006年 | 16719篇 |
2005年 | 14882篇 |
2004年 | 14304篇 |
2003年 | 14092篇 |
2002年 | 13391篇 |
2001年 | 13217篇 |
2000年 | 12598篇 |
1999年 | 12582篇 |
1998年 | 29763篇 |
1997年 | 21105篇 |
1996年 | 16111篇 |
1995年 | 12228篇 |
1994年 | 10906篇 |
1993年 | 11032篇 |
1992年 | 8365篇 |
1991年 | 8046篇 |
1990年 | 8129篇 |
1989年 | 7686篇 |
1988年 | 7368篇 |
1987年 | 6732篇 |
1986年 | 6520篇 |
1985年 | 7222篇 |
1984年 | 6784篇 |
1983年 | 6242篇 |
1982年 | 5788篇 |
1981年 | 5906篇 |
1980年 | 5649篇 |
1979年 | 5770篇 |
1978年 | 5878篇 |
1977年 | 6357篇 |
1976年 | 7800篇 |
1975年 | 5206篇 |
1974年 | 5117篇 |
1973年 | 5216篇 |
1972年 | 4546篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
This paper presents the mass transfer results from an impinging liquid jet to a rotating disk. The mass transfer coefficients were measured using the electrochemical limiting diffusion current technique (ELDCT). Rotational Reynolds number (Rer) in the range of 3.4 × 104–1.2 × 105, jet Reynolds number (Rej) 1.7 × 104–5.3 × 104 and non-dimensional jet-to-disk spacing (H/d) 2–8 were taken into consideration as parameters. It was found that the jet impingement resulted in a substantial enhancement in the mass transfer compared to the case of the rotating disk without jet. 相似文献
952.
Ana MRB Xavier Ana Paula M Tavares Margarida SM Agapito Dmitry V Evtuguin 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(12):1602-1608
BACKGROUND: A sequential batch reactor (SBR) was used for eucalypt kraft pulp effluent treatment with Trametes versicolor. A 23 full factorial design and response surface methodology were applied to optimise the batch fermentation conditions. Effluent concentration, culture medium and inoculum age were the factors selected for this study in order to optimise the reduction of chemical oxygen demand (COD). RESULTS: The presence of Trametes Defined Medium (TDM) in the fermentation was required to obtain a significant COD reduction. Experiments in the batch reactor confirmed, in general, the predicted results of optimisation developed from Erlenmeyer batch assays. The T. versicolor culture remained active during 42 days of study in the SBR, providing approximately 80% of COD reduction. CONCLUSION: Trametes versicolor may be considered as very promising for the biological treatment of effluents from kraft pulp mills in an SBR system instead of the activated sludge mixed cultures traditionally used. Copyright © 2008 Society of Chemical Industry 相似文献
953.
Yu. V. Larichev D. A. Shlyapin P. G. Tsyrul’nikov V. I. Bukhtiyarov 《Catalysis Letters》2008,120(3-4):204-209
Sibunit-supported Ru-catalysts promoted with cesium or rubidium compounds have been comparatively studied with XPS. The cesium promoter interacts both with support and with active component. The absence of the promoter–support interaction in the case of rubidium provides a stronger interaction between promoter and active component compared to the cesium-based catalysts. These differences in the promoter–support and promoter–metal interactions are exhibited when a sequence of ruthenium and alkali introduction are changed. 相似文献
954.
To convey the dynamic information related to traffic conditions in various parts of a city, we propose an environment utilizing the technology of smart phones to provide information anywhere and anytime. Called ";The Interactive Traffic Beat Project,"; it uses a Web-based service to deliver this information to people through their cell phones at the right time so that valuable time can be saved and the chaos on the roads can be managed. 相似文献
955.
956.
Terahertz (THz) imaging is rapidly developing. We present two new methods, based respectively on (a) a broadband thermal source (globar) and (b) a coherent, monochromatic source (optically-pumped THz laser). A room-temperature detector (Golay cell) is employed. Image quality is similar to that reported by others using more complex sources (quantum cascade lasers) and detectors (superconducting tunneling junctions). 相似文献
957.
Residual stress as measured quantity in quality assurance The x‐ray method is used in the Volkswagen Automotive Group at different world‐wide locations as a standard procedure to determine residual stress. As an important measured quantity in the quality assurance residual stresses are specified in drawings of different components (e.g. gears, coil springs). Measurements are carried out during quality assurance, production, damage analyse, technical development department and design control of components from suppliers. An optimum efficiency can be achieved, if it exists a unique correlation between residual stress values and loading capacity of components, and if the processes to introduce residual stress can be optimized using residual stress measurements during the production. 相似文献
958.
A. K. Srivastava Ram M. Shrestha S. C. Srivastava Rabin Shrestha Dharam Paul 《国际能源研究杂志》2003,27(7):671-685
The power sector in India at present comprises of five separate regional electricity grids having practically no integrated operation in between them. This study analyses the utility planning, environmental and economical effects of integrated power sector development at the national level in which the regional electric grids are developed and operated as one integrated system. It also examines the effects of selected CO2 emission reduction targets in the power sector and the role of renewable power generation technologies in India. The study shows that the integrated development and operation of the power system at the national level would reduce the total cost including fuel cost by 4912 million $, total capacity addition by 2784 MW, while the emission of CO2, SO2 and NOx would be reduced by 231.6 (1.9%), 0.8 (0.9%), 0.4 (1.2%) million tons, respectively, during the planning horizon. Furthermore, the study shows that the expected unserved energy, one of the indices of generation system reliability, would decrease to 26 GWh under integrated national power system from 5158 GWh. As different levels of CO2 emission reduction targets were imposed, there is a switching of generation from conventional coal plants to gas fired plants, clean coal technologies and nuclear based plants. As a result the capacity expansion cost has increased. It was found that wind power plant is most attractive and economical in the Indian perspective among the renewable options considered (Solar, wind and biomass). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
959.
A. V. Lyutetskii N. A. Pikhtin S. O. Slipchenko N. V. Fetisova A. Yu. Leshko E. G. Golikova Yu. A. Ryaboshtan I. S. Tarasov 《Technical Physics Letters》2003,29(4):290-293
Separate confinement InGaAsP/InP laser heterostructures were grown by metalorganic-hydride vapor-phase epitaxy. High-power single-mode laser diodes of mesastripe design based on these heterostructures operate in a wavelength interval of 1.7–1.8 μm with a maximum continuous room temperature output power of 150 mW. The single-mode lasing regime is maintained up to an output power level of 100 mW. 相似文献
960.