全文获取类型
收费全文 | 5359篇 |
免费 | 175篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 54篇 |
综合类 | 6篇 |
化学工业 | 1157篇 |
金属工艺 | 106篇 |
机械仪表 | 144篇 |
建筑科学 | 204篇 |
矿业工程 | 23篇 |
能源动力 | 94篇 |
轻工业 | 448篇 |
水利工程 | 43篇 |
石油天然气 | 35篇 |
武器工业 | 1篇 |
无线电 | 444篇 |
一般工业技术 | 848篇 |
冶金工业 | 1059篇 |
原子能技术 | 32篇 |
自动化技术 | 844篇 |
出版年
2022年 | 49篇 |
2021年 | 86篇 |
2020年 | 73篇 |
2019年 | 62篇 |
2018年 | 86篇 |
2017年 | 82篇 |
2016年 | 123篇 |
2015年 | 79篇 |
2014年 | 140篇 |
2013年 | 329篇 |
2012年 | 240篇 |
2011年 | 290篇 |
2010年 | 196篇 |
2009年 | 194篇 |
2008年 | 206篇 |
2007年 | 230篇 |
2006年 | 182篇 |
2005年 | 135篇 |
2004年 | 149篇 |
2003年 | 145篇 |
2002年 | 141篇 |
2001年 | 103篇 |
2000年 | 95篇 |
1999年 | 123篇 |
1998年 | 182篇 |
1997年 | 121篇 |
1996年 | 99篇 |
1995年 | 93篇 |
1994年 | 85篇 |
1993年 | 81篇 |
1992年 | 63篇 |
1991年 | 53篇 |
1990年 | 74篇 |
1989年 | 68篇 |
1988年 | 50篇 |
1987年 | 48篇 |
1986年 | 41篇 |
1985年 | 65篇 |
1984年 | 49篇 |
1983年 | 50篇 |
1982年 | 40篇 |
1981年 | 52篇 |
1980年 | 51篇 |
1979年 | 52篇 |
1978年 | 48篇 |
1977年 | 42篇 |
1976年 | 48篇 |
1975年 | 59篇 |
1974年 | 39篇 |
1973年 | 32篇 |
排序方式: 共有5542条查询结果,搜索用时 15 毫秒
41.
Higher heating values (HHVs) of fatty acids (C4–C18) were measured and correlated using linear least square regression analysis. Equations were developed for the estimation of the HHVs of saturated fatty acids from their molecular weight (Mw), density (DN) and carbon number (CN). These equations are HHV = 0.0518 Mw + 29.76, HHV = −93.4 DN + 122.67 and HHV = 0.7271 CN + 31.419 with R2 values of 0.9895, 0.9798, and 0.9895, respectively. The correlations may be used for HHV estimation of mixtures of fatty acids developed from vegetable oils. 相似文献
42.
Costa Albert; Kovacic Damir; Fedorenko Evelina; Caramazza Alfonso 《Canadian Metallurgical Quarterly》2003,29(6):1270
The authors report 3 picture-word interference experiments in which they explore some properties of the agreement process in speech production. In Experiment 1, Croatian speakers were asked to produce utterances in which the noun's gender value had an impact on the selection of gender-marked freestanding morphemes (pronouns) while ignoring the presentation of same- or different-gender distractor words. In Experiments 2 and 3, Croatian speakers were asked to name the same pictures using noun phrases in which the noun's gender value surfaced as an inflectional suffix. Different-gender distractors interfered more than same-gender distractors (the gender congruency effect) in Experiment 1, but not in Experiments 2 and 3. These contrasting results show that the cause of the gender congruency effect is not at the level where lexical-grammatical information is selected but at the level of selection of freestanding morphemes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
This obituary reports the death of Harold Harding Kelley, Professor Emeritus of Psychology at University of California (1921-2003). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
45.
46.
The Wabash River Integrated Methanol and Power Production from Clean Coal Technologies (IMPPCCT) project is investigating an Early Entrance Coproduction Plant (EECP) concept to evaluate integrated electrical power generation and methanol production from coal and other carbonaceous feedstocks. Research, development and testing (RD&T) that is currently being conducted under the project is evaluating cost effective process systems for removing contaminants, particularly sulfur species, from the generated gas which contains mainly synthesis gas (syngas), CO2 and steam at concentrations acceptable for the methanol synthesis catalyst. The RD&T includes laboratory testing followed by bench-scale and field testing at the SG Solutions Gasification Plant located in West Terre Haute, Indiana. Actual synthesis gas produced by the plant was utilized at system pressure and temperature for bench-scale field testing. 相似文献
47.
This paper highlights the role of the faculty member in recruiting students currently enrolled in B.S. programs in engineering and the sciences into full-time pursuit of a graduate-level engineering degree. The faculty member is demonstrated to be in a unique position to influence such students, providing strong counterforces to a confluence of attitudes and pressures experienced during the B.S. experience which effectively create a barrier to full-time engineering graduate study. We analyze this barrier via the method of force field analysis, and demonstrate that effective recruitment into full-time graduate study must be based on a four-fold strategy of education, expectations, improved B.S. experience and better control of the B.S. environment. Approaches to implement these strategies are discussed. 相似文献
48.
M Albert C Athanassopoulos LB Auerbach D Bauer R Bolton B Boyd RL Burman I Cohen DO Caldwell BD Dieterle JB Donahue AM Eisner A Fazely FJ Federspiel GT Garvey RM Gunasingha V Highland J Hill R Imlay K Johnston WC Louis A Lu AK Mann J Margulies K McIlhany W Metcalf RA Reeder V Sandberg M Schillaci D Smith I Stancu W Strossman MK Sullivan GJ VanDalen W Vernon YX Wang DH White D Whitehouse D Works Y Xiao S Yellin 《Canadian Metallurgical Quarterly》1995,51(3):R1065-R1069
49.
Jennifer K. Edwards Adrian Thomas Benjamin E. Solsona Philip Landon Albert F. Carley Graham J. Hutchings 《Catalysis Today》2007,122(3-4):397-402
The direct synthesis of hydrogen peroxide from H2 and O2 using a range of supported Au–Pd alloy catalysts is compared for different supports using conditions previously identified as being optimal for hydrogen peroxide synthesis, i.e. low temperature (2 °C) using a water–methanol solvent mixture and short reaction time. Five supports are compared and contrasted, namely Al2O3, -Fe2O3, TiO2, SiO2 and carbon. For all catalysts the addition of Pd to the Au only catalyst increases the rate of hydrogen peroxide synthesis as well as the concentration of hydrogen peroxide formed. Of the materials evaluated, the carbon-supported Au–Pd alloy catalysts give the highest reactivity. The results show that the support can have an important influence on the synthesis of hydrogen peroxide from the direct reaction. The effect of the methanol–water solvent is studied in detail for the 2.5 wt% Au–2.5 wt% Pd/TiO2 catalyst and the ratio of methanol to water is found to have a major effect on the rate of hydrogen peroxide synthesis. The optimum mixture for this solvent system is 80 vol.% methanol with 20 vol.% water. However, the use of water alone is still effective albeit at a decreased rate. The effect of catalyst mass was therefore also investigated for the water and water–methanol solvents and the observed effect on the hydrogen peroxide productivity using water as a solvent is not considered to be due to mass transfer limitations. These results are of importance with respect to the industrial application of these Au–Pd catalysts. 相似文献
50.
Although the banking industry plays a central role in the world economy and has traditionally been an innovative user of information technology, banks are struggling to develop mature Internet strategies. A model used to analyze the type of Internet activities among a sample of banks as well as their level of sophistication and customization is useful not only for revealing unexploited opportunities in the banking sector but also for guiding the strategy-building process of organizations in other industries. 相似文献