全文获取类型
收费全文 | 2864篇 |
免费 | 18篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 50篇 |
综合类 | 15篇 |
化学工业 | 640篇 |
金属工艺 | 95篇 |
机械仪表 | 157篇 |
建筑科学 | 72篇 |
矿业工程 | 10篇 |
能源动力 | 567篇 |
轻工业 | 76篇 |
水利工程 | 12篇 |
石油天然气 | 37篇 |
无线电 | 227篇 |
一般工业技术 | 431篇 |
冶金工业 | 28篇 |
原子能技术 | 22篇 |
自动化技术 | 450篇 |
出版年
2024年 | 3篇 |
2023年 | 32篇 |
2022年 | 32篇 |
2021年 | 45篇 |
2020年 | 77篇 |
2019年 | 96篇 |
2018年 | 35篇 |
2017年 | 116篇 |
2016年 | 229篇 |
2015年 | 182篇 |
2014年 | 344篇 |
2013年 | 284篇 |
2012年 | 222篇 |
2011年 | 193篇 |
2010年 | 146篇 |
2009年 | 154篇 |
2008年 | 41篇 |
2007年 | 82篇 |
2006年 | 87篇 |
2005年 | 56篇 |
2004年 | 33篇 |
2003年 | 34篇 |
2002年 | 46篇 |
2001年 | 51篇 |
2000年 | 34篇 |
1999年 | 93篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 15篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
排序方式: 共有2889条查询结果,搜索用时 0 毫秒
1.
Abdelbaki Benamor Brahim Si Ali Mohamed Kheireddine Aroua 《Korean Journal of Chemical Engineering》2008,25(3):451-460
The absorption rates of CO2 into aqueous solutions of Diethanolamine (DEA) with varying concentrations from 0.2 to 4M and temperature range from 293
to 323 K were measured by using a laboratory stirred reactor. The CO2 partial pressure was varied in a range that the reaction would occur in pseudo first order regime. Experimental data were
analyzed and the kinetic parameters associated with the reaction were determined. The activation energy for the deprotonation
of the intermediate zwitterion was estimated at about 11.4 kcal/mol. The contribution of carbamate formation to the overall
absorbed CO2 was experimentally evaluated and found to be of the order of 100%. 相似文献
2.
3.
4.
《Cement and Concrete Composites》2006,28(1):21-25
The effectiveness of a new type of alkali activator is studied. The activator is a product of silica fume. The results obtained showed the silica fume activator as a highly effective substance for the alkali activation of the combinations of Portland cement, silica fume and blast furnace slag, and slag alone. The positive effect of activator is based on the intensification of the production of calcium silicate hydrates and the densifying of the forming pore structure of the activated binder. 相似文献
5.
《Fuel》2006,85(5-6):867-870
Crude and distilled palm oil methyl esters conveniently known as palm diesel have been successfully evaluated as diesel substitute. Crude palm oil methyl esters are produced from transesterification of crude palm oil with minor components such as carotenes and vitamin E still intact and they are reddish in colour. The distilled palm oil methyl esters are obtained after the recovery of minor components (e.g. Carotenes and vitamin E) From the crude palm oil methyl esters. These valuable minor components are preferably to be recovered as they can be sold as value-added products before they are burnt together with the methyl esters as fuel. Although both possesses fuel characteristics which are comparable to those of petroleum diesel, crude palm oil methyl esters are found to exhibit better oxidative stability (rancimat induction period >25 h) than distilled palm oil methyl esters (about 3.5 h). It is attributed to the presence of vitamin E (about 600 ppm), a natural antioxidant in the former. While the distilled palm oil methyl esters contain practically no vitamin E (<50 ppm) and as a result, they exhibit poor oxidative stability. Thus, the crude palm oil methyl esters meet the european standard for biodiesel (EN 14214) which has set a minimum rancimat induction period of 6 h. In the present study, research was conducted to enhance the oxidative stability of distilled palm oil methyl esters in order to meet the aforementioned standard. Natural and synthetic antioxidants were used in the present study to investigate their effect on the oxidative stability of distilled palm oil methyl esters. It was found that both types of antioxidant showed beneficial effects in inhibiting the oxidation of distilled palm oil methyl esters. Comparatively, the synthetic antioxidants were found to be more effective than the natural antioxidants as lower dosage (17 times less) was needed to achieve the minimum rancimat induction period of 6 h. 相似文献
6.
《Solid-state electronics》2006,50(7-8):1382-1388
We have performed the first principles full-potential linearized augmented plane wave calculations (FP-LAPW) with density functional theory in local density approximations (LDA), in aim to determine and to predict the pressure dependence of structural and optical properties of zinc-blende BeS, BeSe and BeTe compounds. The elastic constant, refractive index and its variation with hydrostatic pressure are well described. 相似文献
7.
《Cement and Concrete Composites》2007,29(1):13-21
There are ∼6700 million tons of perlite reserves in the world and two thirds of this amount takes place in Turkey. Although perlite possesses pozzolanic properties, it has not been so far used in producing blended cements. This study focuses on the use of natural perlites in blended cement production. For this purpose, after examining the suitability of the perlites as pozzolans and their ease of grindability, 16 types of blended cements having 320 m2/kg or 370 m2/kg Blaine fineness were produced by using 20% or 30% perlite additions. Production of the blended cements were accomplished either by intergrinding or separate grinding. The performance of the cements was evaluated by conducting the following tests: particle size distribution by laser diffraction, normal consistency, setting time, soundness and compressive strength. The results showed that perlites possess sufficient pozzolanic characteristics to be used in production of blended cement. 相似文献
8.
《Expert systems with applications》2014,41(18):8225-8233
The current web IR system retrieves relevant information only based on the keywords which is inadequate for that vast amount of data. It provides limited capabilities to capture the concepts of the user needs and the relation between the keywords. These limitations lead to the idea of the user conceptual search which includes concepts and meanings. This study deals with the Semantic Based Information Retrieval System for a semantic web search and presented with an improved algorithm to retrieve the information in a more efficient way.This architecture takes as input a list of plain keywords provided by the user and the query is converted into semantic query. This conversion is carried out with the help of the domain concepts of the pre-existing domain ontologies and a third party thesaurus and discover semantic relationship between them in runtime. The relevant information for the semantic query is retrieved and ranked according to the relevancy with the help of an improved algorithm. The performance analysis shows that the proposed system can improve the accuracy and effectiveness for retrieving relevant web documents compared to the existing systems. 相似文献
9.
Estimation and forecasting with logarithmic autoregressive conditional duration models: A comparative study with an application 总被引:1,自引:0,他引:1
《Expert systems with applications》2014,41(7):3323-3332
This paper presents a semi-parametric method of parameter estimation for the class of logarithmic ACD (Log-ACD) models using the theory of estimating functions (EF). A number of theoretical results related to the corresponding EF estimators are derived. A simulation study is conducted to compare the performance of the proposed EF estimates with corresponding ML (maximum likelihood) and QML (quasi maximum likelihood) estimates. It is argued that the EF estimates are relatively easier to evaluate and have sampling properties comparable with those of ML and QML methods. Furthermore, the suggested EF estimates can be obtained without any knowledge of the distribution of errors is known. We apply all these suggested methodology for a real financial duration dataset. Our results show that Log-ACD (1, 1) fits the data well giving relatively smaller variation in forecast errors than in Linear ACD (1, 1) regardless of the method of estimation. In addition, the Diebold–Mariano (DM) and superior predictive ability (SPA) tests have been applied to confirm the performance of the suggested methodology. It is shown that the new method is slightly better than traditional methods in practice in terms of computation; however, there is no significant difference in forecasting ability for all models and methods. 相似文献
10.
《Expert systems with applications》2014,41(7):3343-3350