全文获取类型
收费全文 | 2428篇 |
免费 | 106篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
综合类 | 4篇 |
化学工业 | 515篇 |
金属工艺 | 18篇 |
机械仪表 | 21篇 |
建筑科学 | 107篇 |
矿业工程 | 3篇 |
能源动力 | 35篇 |
轻工业 | 348篇 |
水利工程 | 34篇 |
石油天然气 | 1篇 |
无线电 | 83篇 |
一般工业技术 | 323篇 |
冶金工业 | 844篇 |
原子能技术 | 4篇 |
自动化技术 | 181篇 |
出版年
2024年 | 4篇 |
2023年 | 35篇 |
2022年 | 87篇 |
2021年 | 90篇 |
2020年 | 57篇 |
2019年 | 47篇 |
2018年 | 63篇 |
2017年 | 50篇 |
2016年 | 57篇 |
2015年 | 45篇 |
2014年 | 63篇 |
2013年 | 117篇 |
2012年 | 111篇 |
2011年 | 162篇 |
2010年 | 128篇 |
2009年 | 129篇 |
2008年 | 154篇 |
2007年 | 126篇 |
2006年 | 107篇 |
2005年 | 95篇 |
2004年 | 85篇 |
2003年 | 69篇 |
2002年 | 76篇 |
2001年 | 42篇 |
2000年 | 52篇 |
1999年 | 44篇 |
1998年 | 39篇 |
1997年 | 48篇 |
1996年 | 42篇 |
1995年 | 45篇 |
1994年 | 55篇 |
1993年 | 36篇 |
1992年 | 32篇 |
1991年 | 9篇 |
1990年 | 25篇 |
1989年 | 16篇 |
1988年 | 25篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有2536条查询结果,搜索用时 10 毫秒
21.
22.
Providing an easy ingress–egress (I/E) movement remains a challenge for car designers. I/E has been largely studied in kinematics, but not in dynamics. This study proposes: (1) to evaluate and describe the motor torques developed in the lower limbs and lumbar joints during I/E motions and (2) to analyse the influence of the car geometry and subject anthropometry. An experiment was performed to observe 15 subjects of three anthropometrical groups getting in and out of a car mock-up simulating three different vehicle configurations. Motor torques were extracted using an inverse dynamics analysis. Both ingress and egress motions were primarily characterised by large torques. Overall, the taller a subject and the lower the seat of the vehicle were, the larger the peak torques were. Moreover, peak torques were higher for egress than ingress. These results are discussed in regard to the current knowledge on I/E ergonomics. 相似文献
23.
Rat hepatocytes in monolayer culture were utilized to determine if the decrease in glucose-6-phosphate dehydrogenase (G6PD)
activity resulting from the ingestion of fat can be mimicked by the addition of fatty acids to a chemically, hormonally defined
medium. G6PD activity in cultured hepatocytes was induced several-fold by insulin. Dexamethasone or T3 did not amplify the
insulin induction of G6PD. Glucose alone increased G6PD activity in cultured hepatocytes from fasted donors by nearly 500%.
Insulin in combination with glucose induced G6PD an additional two-fold. The increase in G6PD activity caused by glucose was
greater in hepatocytes isolated from 72 hr-fasted rats as compared to fed donor rats. Such a response was reminiscent of the
“overshoot” phenomenon in which G6PD activity is induced well above the normal level by fasting-refeeding rats a high glucose
diet. Addition of linoleate to the medium resulted in a significant suppression of insulin’s ability to induce G6PD, but linoleate
had no effect on the induction of G6PD activity by glucose alone. A shift to the right in the insulin-response curve for the
induction of G6PD also was detected for the induction of malic enzyme and acetyl-CoA carboxylase. Arachidonate (0.25 mM) was
a significantly more effective inhibitor of the insulin action than linoleate was. Apparently rat hepatocytes in monolayer
culture can be utilized as a model to investigate the molecular mechanism by which fatty acids inhibit the production of lipogenic
enzymes. In part, this mechanism of fatty acid inhibition involves desensitization of hepatocytes to the lipogenic action
of insulin. 相似文献
24.
Alumina membranes were prepared using a sol–gel process. Thin gel layers were grown onto porous alumina support tubes by using the permeation of water through the tube to control the rate of hydrolysis. Optimum coating conditions were found to be an ASB to 2-propanol volume ratio of 1:25, coating times between 10 and 15 s, and partial drying times between 2.5 and 3 min, depending on whether the water was flowing in the tube or stored in the tube. The coatings remained crack-free and adherent when fired to 800°C. 相似文献
25.
Lisa N. Yee Casimir C. Akoh Robert S. Phillips 《Journal of the American Oil Chemists' Society》1997,74(3):255-260
Pseudomonas sp. lipase PS was immobilized by adsorption and tested for its ability to catalyze the synthesis of citronellyl butyrate
and geranyl caproate by transesterification in n-hexane. The reaction parameters investigated were: enzyme load, effect of substrate concentration, added water, temperature,
time course, organic solvent, pH memory, and enzyme reuse. Yields as high as 96 and 99% were obtained for citronellyl butyrate
and geranyl caproate, respectively, with 300 units (approx. 15% w/w of reactants) of lipase PS. Increasing amounts of terpene
alcohol inhibited lipase activity, while excess acyl donor (triacylglycerol) concentration enhanced ester production. Optimal
yields were obtained at temperatures from 30–50°C after 24-h incubation time. Yields of 90 and 99% were obtained for citronellyl
and geranyl esters, respectively, with 2% added water. Solvents with log P values ≥ 2.5 showed the highest conversion yields. pH 7 and 6–8 seemed to be ideal for citronellyl butyrate and geraniol
caproate, respectively. The lipase remained active after reusing 12 times. 相似文献
26.
Cleland LG Proudman SM Hall C Stamp LK McWilliams L Wylie N Neumann M Gibson RA James MJ 《Lipids》2003,38(4):419-424
Dietary fish oil supplements have been shown to have benefits in rheumatoid arthritis (RA), other inflammatory diseases, and
in cardiovascular disease. As with any medical advice, variability will exist with regard to adherence and consequent biochemical
or pharmacophysiologic effects. The aim was to explore the utility of plasma phospholipid EPA as a measure of n−3 PUFA intake
and response to standardized therapeutic advice given in an outpatient or office practice setting, to increase dietary n−3
PUFA, including a fish oil supplement. Patients with early RA were given verbal and written advice to alter their dietary
n−3 PUFA intake, including ingestion of 20 mL of bottled fish oil on juice daily. The advice included instructions to increase
n−3 PUFA and to avoid foods rich in n−6 PUFA. Every 3 mon, blood samples were obtained for analysis of plasma phospholipid
FA. Plasma phospholipid EPA was used as the primary index of n−3 PUFA intake. A diverse response was seen, with about one-third
of patients achieving a substantial elevation of plasma phospholipid EPA over the 12-mon study period. A third had little
change, with the remainder achieving intermediate levels. Data obtained longitudinally from individual patients indicated
that substantial elevations of EPA (>5% total plasma phospholipid FA) could be maintained for more than 3 yr. Plasma phospholipid
EPA is a convenient measure of adherence to advice to take a dietary n−3 PUFA-rich fish oil supplement. This measure may prove
a useful adjunct to intention to treat analyses in determining the effect of dietary fish oil supplements on long-term outcomes
in arthritis and other chronic inflammatory diseases. It may also provide a guide to the effectiveness of therapeutic and
preventive messages designed to increase n−3 PUFA intake. 相似文献
27.
Adriana Caione Anna Lisa Guido Angelo Martella Roberto Paiano Andrea Pandurino 《Information Systems and E-Business Management》2016,14(3):533-576
Enterprise activities are governed by regulations and laws that are multiple, heterogeneous and not always easy to understand. The arising and/or the modification of these regulations and laws can cause a significant impact in the business context, especially in terms of enterprise information systems adaptation. Currently, there are many methodological and technological tools that facilitate the application of regulations and procedures, but they are not integrated enough to ensure a complete problem management. Therefore, they are not sufficient to support organizations and companies in the management of their business processes. In this paper we propose a methodological and technological solution, able to model, manage, execute and monitor business processes of complex domains. The system allows both the design of an information system and its prototyping as a web application, by the extension of an appropriately selected Business Process Management suite. During both the design and the usage phases of the prototyped information system, it is possible to interface with a knowledge base that contains information about regulations and aspects that characterize the enterprise (organizational chart, tasks, etc.). 相似文献
28.
The experimental low energy plasma for hemispherical analyzers nominal testing thermal plasma facility of Dartmouth College uses a microwave plasma source which generates an ionosphere-like plasma through a two-step process. The plasma is initially generated inside a cylindrical, insulated, resonance cavity. This initial plasma must pass through a sheath in order to enter the main experimental region. This process imparts a significant flow velocity to the ions which has been neglected in previous analysis of this plasma source. We predict the flow energy of the ions to be between 12-15 eV depending on conservation laws and show agreement with experimental results. 相似文献
29.
30.
Tom Martin Kahyun Kim Jason Forsyth Lisa McNair Eloise Coupey Ed Dorsa 《Personal and Ubiquitous Computing》2013,17(3):465-478
This paper reports on a design experience for undergraduates in computer engineering, industrial design, and marketing that focuses on pervasive computing devices. Across a broad range of targeted application areas and user groups, many of the student designs have been wearable computers. Consequently, our course will be of interest to the wearable computing community, particularly in terms of our aim of bridging the gap between design and engineering. For the two most recent offerings of the course, we have utilized external observers and surveyed the students in order to validate the impact of aspects of our process and changes to it. This paper is based upon 5 years of experience and 2 years of analysis of our course, and it presents an overview of our process with both qualitative and quantitative results from these two most recent offerings. 相似文献