全文获取类型
收费全文 | 13930篇 |
免费 | 1251篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 97篇 |
综合类 | 9篇 |
化学工业 | 4796篇 |
金属工艺 | 185篇 |
机械仪表 | 360篇 |
建筑科学 | 520篇 |
矿业工程 | 23篇 |
能源动力 | 418篇 |
轻工业 | 3751篇 |
水利工程 | 126篇 |
石油天然气 | 84篇 |
无线电 | 575篇 |
一般工业技术 | 1989篇 |
冶金工业 | 782篇 |
原子能技术 | 50篇 |
自动化技术 | 1425篇 |
出版年
2024年 | 34篇 |
2023年 | 139篇 |
2022年 | 166篇 |
2021年 | 1119篇 |
2020年 | 472篇 |
2019年 | 487篇 |
2018年 | 546篇 |
2017年 | 598篇 |
2016年 | 626篇 |
2015年 | 501篇 |
2014年 | 662篇 |
2013年 | 1061篇 |
2012年 | 1001篇 |
2011年 | 1105篇 |
2010年 | 846篇 |
2009年 | 784篇 |
2008年 | 731篇 |
2007年 | 682篇 |
2006年 | 521篇 |
2005年 | 389篇 |
2004年 | 336篇 |
2003年 | 307篇 |
2002年 | 276篇 |
2001年 | 178篇 |
2000年 | 117篇 |
1999年 | 148篇 |
1998年 | 198篇 |
1997年 | 152篇 |
1996年 | 113篇 |
1995年 | 102篇 |
1994年 | 76篇 |
1993年 | 82篇 |
1992年 | 72篇 |
1991年 | 58篇 |
1990年 | 37篇 |
1989年 | 38篇 |
1988年 | 47篇 |
1987年 | 30篇 |
1986年 | 46篇 |
1985年 | 40篇 |
1984年 | 31篇 |
1983年 | 26篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 30篇 |
1979年 | 25篇 |
1978年 | 22篇 |
1977年 | 18篇 |
1976年 | 19篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
41.
42.
43.
44.
45.
This review article is devoted to the materials containing niobium, which have been discovered or developed in the past few years and exhibit the potential application in heterogeneous catalysis. Niobium oxides and mixed oxides as well as sulfides, nitrides (oxynitrides), carbides (oxycarbides), and phosphates are considered. Among the catalytic processes in which Nb-containing materials were tested, liquid and gas phase oxidation is described in details, and the role of niobium in the prevention of the catalyst from SO2 poisoning is mentioned. 相似文献
46.
An approach is presented to satisfy the demand for simple criteria, guidelines and models for the preliminary sizing of horizontal subsurface flow (SF) constructed wetland systems. This approach eliminates time-consuming calculations and iterations by providing graphical solutions for wetland system sizing. Therefore, it can be used for the preliminary assessment of new or performance evaluation of existing subsurface flow constructed wetland systems. The validity of this methodology is checked with data from existing systems and is found to be quite satisfactory. This methodology is combined with simple equations predicting the maximum wetland capacity in summer, so as to assist designers in sizing installations in tourist areas with increased summer populations. Furthermore, based on this methodology, a sensitivity analysis is performed of the area requirements for wastewaters of various strengths and various design conditions and performance criteria. The results provide a useful overview to engineers and further simplify the design methodology of new subsurface flow constructed wetland systems. 相似文献
47.
48.
Daniela M. Nevskaia Maria Luisa Rojas Cervantes Antonio Guerrero Ruíz Juan de Dios Lpez Gonzlez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):249-256
Adsorption of Triton X-100 on various silica substrates has been investigated. A number of solids, including a natural quartz, this quartz washed with HCl acid and subsequently heated at 1273 K; two aerosils and one Kieselgel silicas were studied. These solids exhibit surface areas in the range of 5 to 430 m2 g?1. All the Triton adsorption isotherms display an S-shape at the adsorption temperatures studied (298 and 308 K). It has been found that the pretreatments of natural quartz (by water washing, impurities removed by acid and/or high temperature calcination) affect considerably the amounts of TX-100 adsorbed. Measurements of surface composition have been made by X-ray photoelectron spectroscopy (XPS) with particular emphasis on the presence of impurities and on the number of OH groups at the surface of the samples. The nature of the surface hydroxyl has also been studied by infrared spectroscopy. Furthermore, the specific number of hydroxyl groups on the surface of the silica samples has been determined by thermogravimetric analysis. Finally an attempt to correlate solid surface characteristics with adsorption isotherms has been developed. 相似文献
49.
50.