全文获取类型
收费全文 | 73233篇 |
免费 | 7971篇 |
国内免费 | 4157篇 |
专业分类
电工技术 | 12087篇 |
技术理论 | 13篇 |
综合类 | 5188篇 |
化学工业 | 8809篇 |
金属工艺 | 2605篇 |
机械仪表 | 2998篇 |
建筑科学 | 9953篇 |
矿业工程 | 2066篇 |
能源动力 | 12709篇 |
轻工业 | 2117篇 |
水利工程 | 1398篇 |
石油天然气 | 2145篇 |
武器工业 | 625篇 |
无线电 | 5153篇 |
一般工业技术 | 7549篇 |
冶金工业 | 3618篇 |
原子能技术 | 1313篇 |
自动化技术 | 5015篇 |
出版年
2024年 | 495篇 |
2023年 | 1669篇 |
2022年 | 2693篇 |
2021年 | 2952篇 |
2020年 | 3137篇 |
2019年 | 2775篇 |
2018年 | 2337篇 |
2017年 | 2784篇 |
2016年 | 3118篇 |
2015年 | 3039篇 |
2014年 | 5093篇 |
2013年 | 4835篇 |
2012年 | 5299篇 |
2011年 | 5964篇 |
2010年 | 4576篇 |
2009年 | 4630篇 |
2008年 | 4193篇 |
2007年 | 4575篇 |
2006年 | 3617篇 |
2005年 | 2794篇 |
2004年 | 2335篇 |
2003年 | 1997篇 |
2002年 | 1772篇 |
2001年 | 1506篇 |
2000年 | 1306篇 |
1999年 | 1049篇 |
1998年 | 835篇 |
1997年 | 663篇 |
1996年 | 597篇 |
1995年 | 444篇 |
1994年 | 403篇 |
1993年 | 318篇 |
1992年 | 242篇 |
1991年 | 223篇 |
1990年 | 184篇 |
1989年 | 154篇 |
1988年 | 129篇 |
1987年 | 96篇 |
1986年 | 71篇 |
1985年 | 96篇 |
1984年 | 87篇 |
1983年 | 52篇 |
1982年 | 69篇 |
1981年 | 34篇 |
1980年 | 42篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1959年 | 5篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
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
52.
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
53.
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
54.
光催化氧化后四环素的分解率与COD去除率之间关系的探讨 总被引:1,自引:0,他引:1
以粉状无机半导体(ZnO)为催化剂,探讨了水溶液中四环素经光催化氧化分解率和COD去除率之间的关系。实验表明,在本实验中四环素的分解率和COD去除率之间有较好的正相关性。当反庆系统中有足量的活性催化剂和足够的光照时间时,绝大部分四环素将被较彻底地氧化分解成CO2,这不仅有助于光催化反应机理的研究,助于今后在环保中的实际应用。 相似文献
55.
A demonstrative study for the wind and solar hybrid power system 总被引:1,自引:0,他引:1
In March 1995, a small scale wind and solar hybrid power system was installed at Ashikaga Institute of Technology. Until now, the authors have acquired the data of the output of the hybrid power plant along with wind speed, wind direction, and the solar radiation, in order to demonstrate a complementary relationship between solar energy and wind energy.After nine months operation of the system, the authors confirmed that there exists a complementary relationship between solar energy and wind energy. We also found, however, that the power output by wind does not have much prospect compared to that by solar cell especially in summer season in Ashikaga area. 相似文献
56.
用电刷镀的方法,对尺寸为2000mm×1000mm×0.8mm 的 A_3钢板电刷镀锌保护层;并对影响镀锌层质量的因素进行了充分的研究。 相似文献
57.
The magnetic properties of polyethersulfone-matrix composites with 3-19 vol.% polycrystalline nickel filaments (0.4 (im diam)
were investigated. These filaments were found to exhibit hysteresis energy loss 10800 J/m3 of nickel and coercive force 16.9 kA/m, compared to corresponding values of 4930 J/m3 and 4.7 kA/m for 2 μ.m diam polycrystalline nickel fibers, 1020 J/m3 and 0.5 kA/m for 20 μm diam polycrystalline nickel fibers, and 1280 J/m3 and 2.3 kA/m for solid polycrystalline nickel. 相似文献
58.
Air cleaning as a means of mitigating the risks arising from exposure to indoor radon progeny has been evaluated in a single-family house in the north eastem US. using an automated, semi-continuous activity-weighted size distribution measurement system. The measurements included radon concentration, condensation nuclei count, and activity-weighted size distribution of radon decay products. Measurements were made in the house with and without an operating air filtration system and with various particle sources common to normal indoor activities operating. Aerosols were generated by running water in a shower, candle burning, cigarette smoking, vacuuming, opening doors, and cooking. Using a room model, the changes in attachment rates, average attachment diameters, and deposition rates of the unattached fraction with and without the air cleaning system were calculated. In the presence of active aerosol sources, the air filtration unit typically reduced the concentration of particles within the hour following the end of particle generation. After candle burning, cigarette smoking, and vacuuming in the bedroom, the reductions of PAEC by air filtration are about 60% with the air filtration system operating in the bedroom. During cooking in the kitchen, the reductions of PAEC in the bedroom with the air filtration system were about 40%. However, for all cases the dose reductions were smaller than the particle and PAEC reductions. For those particles that were generated within the bedroom, there was a 20% to 50% reduction in dose. In the case of cooking where the door was open and particles infiltrated from the rest of the house, the dose reduction was only 5% on average and appears to be insignificant. Thus, the dose reductions were h e r than the reductions in activity concentration, but there were no cases where the estimated dose actually increased. 相似文献
59.
60.