全文获取类型
收费全文 | 4369篇 |
免费 | 7篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 68篇 |
金属工艺 | 12篇 |
机械仪表 | 6篇 |
建筑科学 | 30篇 |
矿业工程 | 3篇 |
能源动力 | 15篇 |
轻工业 | 41篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 28篇 |
一般工业技术 | 95篇 |
冶金工业 | 4000篇 |
原子能技术 | 7篇 |
自动化技术 | 60篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 12篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 20篇 |
2011年 | 22篇 |
2010年 | 13篇 |
2009年 | 11篇 |
2008年 | 22篇 |
2007年 | 22篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 26篇 |
2002年 | 15篇 |
2001年 | 30篇 |
2000年 | 17篇 |
1999年 | 119篇 |
1998年 | 1201篇 |
1997年 | 734篇 |
1996年 | 473篇 |
1995年 | 235篇 |
1994年 | 237篇 |
1993年 | 223篇 |
1992年 | 22篇 |
1991年 | 50篇 |
1990年 | 44篇 |
1989年 | 44篇 |
1988年 | 36篇 |
1987年 | 45篇 |
1986年 | 52篇 |
1985年 | 39篇 |
1984年 | 5篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 26篇 |
1980年 | 52篇 |
1979年 | 3篇 |
1978年 | 9篇 |
1977年 | 113篇 |
1976年 | 259篇 |
1975年 | 9篇 |
1964年 | 2篇 |
1955年 | 5篇 |
1954年 | 2篇 |
排序方式: 共有4376条查询结果,搜索用时 15 毫秒
91.
IT outsourcing is a complex and opaque decision problem. Managers facing a decision about IT outsourcing have difficulty in
framing what needs to be thought about further in their discourses. Framing is one of the most crucial steps of human decision
making and needs to be assisted to better understand a decision situation. In this research, we examine a number of decision
primitives in the context of an IT outsourcing decision situation. We demonstrate how the decision primitives can be employed
so that managers can probe deep to better understand a decision situation and to establish a decision basis. In the organizational
setting, we exemplify the use of the decision primitives in relation to the perceived outsourcing implications for the managers
looking for assistance in accommodating a knowledge management perspective on IT outsourcing. Consequently, we induce insight
and a guideline on how to use knowledge management for effective outsourcing in one of the leading financial institutes in
Europe.
相似文献
Mehmet N. AydinEmail: |
92.
This study aimed to gain insight into the interplay between citizens’ reactions on Twitter and governmental communications as well as their effects on self‐reliant behaviour and trust. Two experimental studies were conducted. In Study 1, participants first received other citizens’ reactions followed by the government's communications about how to act. Participants received supporting, opposing, mixed, or no reactions from other citizens. In Study 2, participants first received the government's communications with either certain or uncertain crisis information, followed by the different citizens’ reactions. The results showed that citizens’ reactions via Twitter are not necessarily detrimental to the effectiveness of governmental communications regarding self‐reliant behaviour. In addition, our findings suggest being careful with providing uncertain governmental communications during a crisis. 相似文献
93.
A comparative semantic study is made of an element of the family of concurrent object-oriented programming languages. Particular attention is paid to two notions: (i) dynamically evolving process structures, including a mechanism to name and refer to processes and a means to create new processes, and (ii) rendez-vous between processes involving the sending and answering of messages and the induced execution of method calls. The methodology of metric semantics is applied in the design of operational and denotational semantics, as well as in the proof of their equivalence. Both semantics employ domains which are determined as fixed points of a contracting functor in the category of complete metric spaces. Moreover, fruitful use is made of the technique of defining semantic meaning functions as fixed points of contracting higher-order mappings. Finally. syntactic and semantic continuations play a pervasive role. 相似文献
94.
95.
To understand the building design process and to help designers involved, the idea of a research engine has been developed: In this engine cyclic transformations take place between spatial and structural building designs. With this engine, a design process can be studied closely and subjected to improvement, and designers can be supported. To develop the engine, in this paper a part of it is studied, namely the transformation from spatial to structural design, which can be divided into four sub transformations: (1) from spatial design to structural topology; (2) from structural topology to mechanical model; (3) from mechanical model to finite element model; (4) from finite element model to design recommendations. For the first sub transformation, two different techniques are presented: Spatial–Structural Transformation Rules and Element Selection. For the second sub transformation, also two techniques are presented: Element Approach and System Approach. Where possible, data models in EXPRESS and process models in IDEF0 are used. For the third and fourth sub transformation, new procedures have been developed using data models in EXPRESS. To test the data and process models for all four sub transformations, a simplified two-storey building, derived from a real six-storey apartment building, is used as case study. It can be concluded that the developed sub transformations function well, related to their application in the research engine, and that their development raises new research questions that have to be solved in the near future. 相似文献
96.
Annealed single-phase NiAl3 and Ni2Al3 materials were leached with 20wt% aqueous NaOH solution to remove the aluminium. At temperatures of 274 to 323 K, NiAl3 leached according to linear kinetics, yielding porous nickel which was friable and disintegrated. At these temperatures Ni2Al3 was unreactive, but at 343 to 380 K it leached according to parabolic kinetics, producing a strong, tightly adherent rim of residual material. The Ni2Al3 reaction proceeded in two steps, firstly to produce a two-phase mixture of Ni2Al3 plus nickel, and secondly to produce nickel alone. In both stages the detailed microstructure of the prior alloy was preserved, implying that the mechanism is selective dissolution. The surface adsorption properties of the nickel residues were obscured by reprecipitated aluminA. However, metal crystallite size measurements showed that a large nickel surface area was potentially available. 相似文献
97.
R Fuhrer C Dufouil TC Antonucci MJ Shipley C Helmer JF Dartigues 《Canadian Metallurgical Quarterly》1999,149(2):116-126
The possible modifying effect of social relations on the association between depression and mortality was examined in a community-based cohort study. A total of 3,777 randomly selected persons 65 years of age and older in southwest France were followed over a 5-year period from 1988 in the Personnes Agees Quid (PAQUID). At study entry, the prevalence of elevated depressive symptomatology was 12.9% for men and 14.7% for women, and the reported relative isolation was 14.1% for men and 26.0% for women. During a total of 16,984 person-years of follow-up, 849 deaths occurred. Among participants with high levels of depressive symptomatology, the age-adjusted mortality rate ratio was 2.10 (95% confidence interval 1.7-2.7) in men and 1.76 (95% confidence interval 1.4-2.3) in women. When compared with individuals with the most connections, men and women with few social network connections were also at increased risk of mortality: age-adjusted rate ratio = 2.69 (95% confidence interval 1.9-3.8) for men and 1.56 (95% confidence interval 1.0-2.4) for women. Satisfaction with social support had a small but nonsignificant effect on mortality risk. For women, the excess risks due to depressive symptoms and few network connections are observed only in the 65- to 74-year age group, after adjusting for health and health behaviors. Social relations did not significantly modify the depression-mortality associations for either men or women, although the depression-mortality effect was reduced by 12.8% in men. The latter findings do not appear to be compatible with the buffering hypothesis, whereby we would expect social relations to decrease the depression-mortality association. Nonetheless, there are independent effects from these two factors, and older men who are depressed and not socially connected are at increased risk of dying earlier. 相似文献
98.
Concepcion Romero & Johanna Bakker 《International Journal of Food Science & Technology》2000,35(1):129-140
Summary It was found that the reaction between malvidin 3-glucoside and added pyruvic acid (PA), leading to the formation of vitisin A in model wine solutions, was not prevented by the addition of either acetaldehyde (A) or several organic acids. The acylated forms of vitisin A (3-acetylvitisin A and 3- p -coumarylvitisin A) were formed through the interaction of malvidin 3-acetylglucoside and malvidin 3- p -coumarylglucoside. Disappearance of the three main anthocyanins (malvidin 3-glucoside, malvidin 3-acetylglucoside and malvidin 3- p- coumarylglucoside) from the model wine with time followed first order kinetics. Acetaldehyde had the effect of increasing the total amount of these losses but producing smaller amounts of vitisin A. During ageing model solutions developed some browness. The brownest solution was obtained without A and a reduced rate of browning was found in the presence of A. This latter result can be explained by the assumption of a superimposition of a blueing effect upon reactions of A with anthocyanins. In the presence of PA the formation of vitisin A compounds gave an intermediate colour, contributing a reddish hue to the solution. A good correlation (r2 = 0.96) between the percentage of vitisin A, of the total anthocyanins and the hue angle was observed. The addition of large amounts of organic acids that are normally found in wine into the model solutions did not lead to the formation of new anthocyanins. The linear loss of PA in all model systems indicates that a first order reaction occurs and 35.35 times more PA than total anthocyanin was lost to form the new compounds. 相似文献
99.
100.