全文获取类型
收费全文 | 29213篇 |
免费 | 3021篇 |
国内免费 | 1759篇 |
专业分类
电工技术 | 1389篇 |
技术理论 | 5篇 |
综合类 | 1605篇 |
化学工业 | 7708篇 |
金属工艺 | 1918篇 |
机械仪表 | 866篇 |
建筑科学 | 1491篇 |
矿业工程 | 1115篇 |
能源动力 | 3444篇 |
轻工业 | 912篇 |
水利工程 | 568篇 |
石油天然气 | 911篇 |
武器工业 | 124篇 |
无线电 | 1518篇 |
一般工业技术 | 3311篇 |
冶金工业 | 2767篇 |
原子能技术 | 217篇 |
自动化技术 | 4124篇 |
出版年
2024年 | 128篇 |
2023年 | 723篇 |
2022年 | 1005篇 |
2021年 | 1128篇 |
2020年 | 1205篇 |
2019年 | 1074篇 |
2018年 | 968篇 |
2017年 | 1115篇 |
2016年 | 1104篇 |
2015年 | 1055篇 |
2014年 | 1866篇 |
2013年 | 1892篇 |
2012年 | 2094篇 |
2011年 | 2787篇 |
2010年 | 2080篇 |
2009年 | 2091篇 |
2008年 | 1896篇 |
2007年 | 1864篇 |
2006年 | 1504篇 |
2005年 | 1056篇 |
2004年 | 841篇 |
2003年 | 744篇 |
2002年 | 670篇 |
2001年 | 466篇 |
2000年 | 424篇 |
1999年 | 389篇 |
1998年 | 319篇 |
1997年 | 249篇 |
1996年 | 260篇 |
1995年 | 170篇 |
1994年 | 169篇 |
1993年 | 122篇 |
1992年 | 118篇 |
1991年 | 74篇 |
1990年 | 54篇 |
1989年 | 36篇 |
1988年 | 34篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 36篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1973年 | 3篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Zhonghua LIU+ Chunpeng LIU Dept. of Metallurgy Kunming Institute of Technology Kunming China 《材料科学技术学报》1993,9(2):136-138
Reduction of stibnite with hydrogen in the presence of calcium oxide has been experimentally inves-tigated at moderate temperature. The results reveal that the effluent generated in the reduction pro-cess contains much less air-polluting substance H_2S, and that the reaction activation energy is63. 3 kJ/mol. The form of antimony changes considerably when the reaction temperature varies. 相似文献
92.
93.
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
94.
特超稠油污水回掺降粘集输工艺 总被引:4,自引:1,他引:3
通过对河南古城油田BQ10区特超稠油乳状液的室内试验分析,指出该种乳状液的实际相突变点为68%左右,当相浓度Φ≥68%时,以W/O型为主的乳状液突变为以O/W型为主的乳状液.乳状液变型后,原油与管道内壁之间的摩擦以及原油之间的摩擦转变为水与管道内壁及水与水之间的摩擦,从而大幅度降低其粘度和摩阻损失;通过对古城BQ10区特超稠油区块单元内部污水回掺降粘集输的现场试验,证明与室内试验分析得出的结论相符合,说明区块单元污水回掺不同于常规的掺热水,也不同于掺联合站处理过的净化污水,它优于单井掺稀油.最后指出该工艺可有效地降低井站回压,方便生产管理,降低开采成本,提高采油效率和经济效益,具有低耗节能的优点. 相似文献
95.
96.
A two-dimensional model was applied to simulate the liquid core reduction(LCR) technology of bloom CC using ANSYS software.The deformation characteristics of bloom under different liquid fraction and reducing amount are obtained.The results indicate that the main deformation condition of bloom shell is compressive strain,mainly undertaken by the liquid core,which increases with the enhancement of reducing amount.Solidified shell takes minor deformation.The longitudinal section of bloom appears sunken and the narrow side bulges,which grow serious when the liquid fractionincreases. 相似文献
97.
98.
This study has explored the potential energy surface on the chemical reaction of CH2OH with NO by using ab initio calculation. We have found the new reaction pathway producing N-hydroxy formamide, which can further decompose to generate isocyanic acid as a reducing agent of hydrocarbons selective catalytic reduction. 相似文献
99.
L. O. Aizenberg E. A. Khvoles 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(6):379-382
Problems with the construction of transmission lines above a forest are examined. Construction of lines above standing timber
makes it possible to shorten the length of the route, eliminate the clearing of a continuous swath along the line, and reduce
the volume of in-service work. To implement this solution, it is necessary to introduce changes and supplements to existing
regulatory technical documents.
__________
Translated from élektricheskie Stantsii, No. 10, October 2007, pp. 48–51. 相似文献
100.
Ali Hassanzadeh 《Corrosion Science》2007,49(4):1895-1906
In our previous works, the corrosion inhibition properties of propylamine (PA), iso-propylamine (i-PA), butylamine (BA), tert-butylamine (t-BA), hexylamine (HA), ethylenediamine (EDA), diethanolamine (DEA), 3-amino-1-propanol (3-AP), 2-dimethylethanolamine (2-DEA), cyclohexylamine (CHA), N-methylcyclohexylamine (N-MCA) and dicyclohexylamine (DCHA) have been investigated by means of electrochemical impedance spectroscopy (EIS) with a carbon steel rotating disc electrode in some petroleum/water corrosive mixtures containing acetic acid and NaCl at 25 °C. In this work, the Kramers-Kronig transformations (KKTs) were applied to evaluate the validity of the impedance data of these amine compounds in hydrodynamic condition. The results obtained showed that experimental impedance data did not satisfy in K-K relations completely viz. indicated some errors. These errors were related to stray capacitances, external transmission line effects, pits formation and change in interface during data acquisition at high and low frequencies regions. In addition, the selection of a suitable equivalent circuit strongly emphasized to better interpret of EIS data which in turn cause better resulted KKTs spectra. With considering obtained transformations, more effective inhibitor was selected with regard to its charge transfer resistance, the corrosion capacitance and well satisfying in K-K relations. 相似文献