全文获取类型
收费全文 | 810338篇 |
免费 | 29108篇 |
国内免费 | 13534篇 |
专业分类
电工技术 | 26345篇 |
技术理论 | 56篇 |
综合类 | 20076篇 |
化学工业 | 132776篇 |
金属工艺 | 37369篇 |
机械仪表 | 35501篇 |
建筑科学 | 37126篇 |
矿业工程 | 13892篇 |
能源动力 | 20555篇 |
轻工业 | 64199篇 |
水利工程 | 10443篇 |
石油天然气 | 33688篇 |
武器工业 | 2643篇 |
无线电 | 86922篇 |
一般工业技术 | 130612篇 |
冶金工业 | 107199篇 |
原子能技术 | 14978篇 |
自动化技术 | 78600篇 |
出版年
2023年 | 5901篇 |
2022年 | 11221篇 |
2021年 | 16282篇 |
2020年 | 12565篇 |
2019年 | 11506篇 |
2018年 | 15504篇 |
2017年 | 16608篇 |
2016年 | 15927篇 |
2015年 | 16409篇 |
2014年 | 23046篇 |
2013年 | 39387篇 |
2012年 | 31651篇 |
2011年 | 38100篇 |
2010年 | 31813篇 |
2009年 | 32583篇 |
2008年 | 32755篇 |
2007年 | 32149篇 |
2006年 | 31373篇 |
2005年 | 28020篇 |
2004年 | 21570篇 |
2003年 | 19973篇 |
2002年 | 19129篇 |
2001年 | 18222篇 |
2000年 | 18368篇 |
1999年 | 19992篇 |
1998年 | 33007篇 |
1997年 | 24915篇 |
1996年 | 20430篇 |
1995年 | 16050篇 |
1994年 | 14111篇 |
1993年 | 12550篇 |
1992年 | 9899篇 |
1991年 | 9059篇 |
1990年 | 8631篇 |
1989年 | 8284篇 |
1988年 | 7912篇 |
1987年 | 6605篇 |
1986年 | 6517篇 |
1985年 | 7246篇 |
1984年 | 6837篇 |
1983年 | 6202篇 |
1982年 | 5823篇 |
1981年 | 5959篇 |
1980年 | 5766篇 |
1979年 | 5546篇 |
1978年 | 5582篇 |
1977年 | 6341篇 |
1976年 | 8173篇 |
1975年 | 5040篇 |
1973年 | 4918篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The tensile elastic modulus (E), yield stress (σY) and microhardness (MH) of neat and binary and ternary blends of glassy semicrystalline ethylene–vinyl alcohol copolymer (EVOH), a glassy amorphous polyamide and a semicrystalline nylon‐containing ionomer covering a broad range of properties were examined. The tests were carried out on dry and water‐equilibrated samples to produce stiffer and softer materials, respectively. From the results, more accurate linear correlations were found to describe adequately the microhardness, modulus and yield stress of these strongly self‐associated polymers through hydrogen bonding. Copyright © 2003 Society of Chemical Industry 相似文献
12.
13.
The objective of this study was to compare methane production and characteristics of digested material in anaerobic digestion concepts according to the Animal By-Products Regulation (ABP-Regulation) of the EC (hygienisation of biowaste for 1 hour at 70 degrees C, particle size < 12 mm) and Finnish national regulations (treatment temperature 55 degrees C, feeding interval 24 h, hydraulic retention time (HRT) 20 d, particle size < 40 mm) and with small variations in treatment methods for treating manure and biowaste. Moreover, the survival of three different salmonella bacteria in these processes was studied. Hygienisation of biowaste prior to digestion at 35 degrees C enhanced methane production by 14-18% compared to similar treatment without hygienisation. The differences in treatment temperature, HRT and hygienisation of biowaste prior to digestion did not significantly affect the characteristics of digested material. The concepts according to the ABP-Regulation and Finnish national regulations were effective in destroying salmonella bacteria to an undetectable level. 相似文献
14.
A locomotive cabin adsorption air‐conditioner has been equipped in #DF4B‐2369 locomotive; and has been successfully run for 2 years. It is powered by waste heat from the exhaust of the diesel engine. The influence on heat transfer is described by the equivalent heat transfer coefficient or thermal resistance of components inside the adsorber. The variation of adsorption capacity is expressed by a non‐equilibrium adsorption function. The dynamic heat transfer process of adsorption air‐conditioning system is treated with the lumped parameter method. Some typical running experimental results are present. The diesel engine rotating speed and locomotive speed influenced on the refrigeration system are discussed. The maximum mean refrigeration power is regarded as an objective function. Based on experiments and theoretical analysis, the running characteristics of the air‐conditioning system are optimized. Some techniques of performance improvement are suggested as well. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
15.
The effects of the cuticle and epicuticular waxes of grapefruit, strawberry and apple on the photodegradation and penetration of chlorpyrifos-methyl were studied. Photodegradation experiments were conducted by exposing the insecticide to the light of a xenon lamp in the presence of a film of wax extracted from the fruit surface. The half-life of chlorpyrifos-methyl irradiated in absence of waxes was 9.6 min. The half-lives of pesticide irradiated in the presence of wax extracts of apple, grapefruit and strawberry were 83, 34 and 26 min, respectively. In penetration studies, fruit with and without wax layers were treated with an aqueous suspension of pesticide. The penetration of the pesticide from the cuticle to the pulp was measured after 24 h. Samples without wax contained a higher total amount of insecticide than those with wax. No pesticide was detected in samples of apple and grapefruit pulp. Residues were detected in all fractions of strawberry. The waxes and cuticle appear to have some effect on the photodegradation and penetration of chlorpyrifos-methyl in fruit samples. 相似文献
16.
The catalytic activities of alumina prepared from an Al alkoxide-amine adduct monomer for the reaction of cyclopentene oxide with piperidine was determined after various pretreatments, including calcination and exposure to moisture. They were compared with the activity of alumina prepared by the conventional hydrolysis method. It was found that the as-prepared sample from the alkoxide-amine monomer preparation was five times more active than a conventional preparation, suggesting that it has a higher density of surface Lewis acid sites. However, its activity was much more severely suppressed by exposure to moisture. 相似文献
17.
18.
19.
Nucleation and growth mechanisms and kinetics of crystals of an amino acid salt were investigated in a methanol‐water system by measuring and evaluating the induction time as a function of the supersaturation ratio and temperature in batch salting out crystallization experiments. Discrimination between the possible crystallization mechanisms, and estimation of the kinetic parameters were carried out using nonlinear parameter identification. The results concerning the growth mechanism obtained were checked additionally by measuring the induction time as a function of number density of seed crystals. 相似文献
20.