全文获取类型
收费全文 | 2696篇 |
免费 | 20篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 23篇 |
综合类 | 1篇 |
化学工业 | 141篇 |
金属工艺 | 6篇 |
机械仪表 | 25篇 |
建筑科学 | 40篇 |
矿业工程 | 2篇 |
能源动力 | 11篇 |
轻工业 | 60篇 |
水利工程 | 13篇 |
石油天然气 | 3篇 |
无线电 | 109篇 |
一般工业技术 | 141篇 |
冶金工业 | 2071篇 |
原子能技术 | 3篇 |
自动化技术 | 73篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 43篇 |
2012年 | 14篇 |
2011年 | 28篇 |
2010年 | 24篇 |
2009年 | 18篇 |
2008年 | 33篇 |
2007年 | 42篇 |
2006年 | 30篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 27篇 |
2002年 | 23篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 80篇 |
1998年 | 697篇 |
1997年 | 363篇 |
1996年 | 250篇 |
1995年 | 140篇 |
1994年 | 144篇 |
1993年 | 133篇 |
1992年 | 22篇 |
1991年 | 30篇 |
1990年 | 35篇 |
1989年 | 34篇 |
1988年 | 39篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 26篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 31篇 |
1979年 | 5篇 |
1978年 | 10篇 |
1977年 | 46篇 |
1976年 | 97篇 |
1975年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有2722条查询结果,搜索用时 15 毫秒
11.
12.
D Barry J Bea D Bernd T DeFauw C Marr T McCormick JK Mitchell M O'Neil M Pittman D Strum 《Canadian Metallurgical Quarterly》1994,68(11):42, 44-46, 48
In cooperation with McManis Associates, Hospitals & Health Networks recently convened a CEO summit on physician/hospital integration activities. In the third report of a three-part series on the summit, leading health care executives discuss investor capital needs, strategic information management needs, and the management competencies required for capitated managed care success. 相似文献
13.
BH Shieh MY Zhu JK Lee IM Kelly F Bahiraei 《Canadian Metallurgical Quarterly》1997,94(23):12682-12687
Visual transduction in Drosophila is a G protein-coupled phospholipase C-mediated process that leads to depolarization via activation of the transient receptor potential (TRP) calcium channel. Inactivation-no-afterpotential D (INAD) is an adaptor protein containing PDZ domains known to interact with TRP. Immunoprecipitation studies indicate that INAD also binds to eye-specific protein kinase C and the phospholipase C, no-receptor-potential A (NORPA). By overlay assay and site-directed mutagenesis we have defined the essential elements of the NORPA-INAD association and identified three critical residues in the C-terminal tail of NORPA that are required for the interaction. These residues, Phe-Cys-Ala, constitute a novel binding motif distinct from the sequences recognized by the PDZ domain in INAD. To evaluate the functional significance of the INAD-NORPA association in vivo, we generated transgenic flies expressing a modified NORPA, NORPAC1094S, that lacks the INAD interaction. The transgenic animals display a unique electroretinogram phenotype characterized by slow activation and prolonged deactivation. Double mutant analysis suggests a possible inaccessibility of eye-specific protein kinase C to NORPAC1094S, undermining the observed defective deactivation, and that delayed activation may similarly result from NORPAC1094S being unable to localize in close proximity to the TRP channel. We conclude that INAD acts as a scaffold protein that facilitates NORPA-TRP interactions required for gating of the TRP channel in photoreceptor cells. 相似文献
14.
This paper argues that shiftworkers may have gradually habituated to their problems and hence that they underestimate them. Some support for this view was obtained in a 'reminiscence' questionnaire study of retired UK Police Officers who had all subsequently taken on another (mainly day-time) job. They completed a specially constructed questionnaire, which included several measures of health and well being, and in which they were asked to reminisce about how they had felt while still a shiftworker. These reminiscence scores were compared to their current perception of how they were. The results clearly indicated that individuals in retrospect perceive their situation as being worse than they realised at the time. This effect was most marked for scores on the General Health Questionnaire and Chronic Fatigue scale. The results of this study draw attention to a potential confounding in much of the shiftwork literature which demands further, more detailed, investigation. 相似文献
15.
RG Wilde JT Billheimer SJ Germain EA Hausner PC Meunier DA Munzer JK Stoltenborg PJ Gillies DL Burcham SM Huang JD Klaczkiewicz SS Ko RR Wexler 《Canadian Metallurgical Quarterly》1996,4(9):1493-1513
Acyl-CoA:cholesterol acyltransferase (ACAT) is the enzyme largely responsible for intracellular cholesterol esterification. A systemic inhibitor of ACAT is believed to be able to slow or even reverse the atherosclerotic process. Towards that goal, a series of cyclic sulfides, derived from the hetero-Diels-Alder reaction of thioaldehydes with 1,3-dienes, and bearing carboxamide substituents, were prepared and evaluated for in vitro (in several tissues and species) and ex vivo ACAT inhibition. Minor changes in subsequent structure were found to have a significant effect in optimization of the biological activity of this series of compounds. 相似文献
16.
17.
BW Woodward JW Mabry MT See JK Bertrand LL Benyshek 《Canadian Metallurgical Quarterly》1993,71(8):2040-2046
An animal model and computer software were developed to conduct across-herd genetic evaluations using data from producers participating in the Sow Productivity Index program of the American Yorkshire Club. The final data set consisted of 61,596 litter records from 1986 to early 1990. The animal model included fixed contemporary group effects and random additive direct, service sire, permanent environmental, and residual effects. Additive genetic relationships among animals were included. A separate relationship matrix for service sires and their sires was also included. A data set similar to the Yorkshire field data was simulated to use in testing the animal model. The simulated data set consisted of 40 herds, each with 120 reproducing dams and either four or five sires. Six generations of simulated data were produced, resulting in 20,605 litter records. These records were then evaluated using the animal model for number of pigs born alive. Finally, correlations between the true breeding values from the simulation and the predicted breeding values were computed. The correlation between the 918 true and predicted sire breeding values was considerably lower for the animal model without a service sire effect than when it was included (.53 vs .74, respectively). However, the difference was cut in half (.66 vs .77) when only sires with greater than five daughter records were included. The high accuracy of the animal model with a random service sire effect indicates that the proposed model adequately accounts for the variation found in records for number of pigs born alive. 相似文献
18.
19.
20.
A competitive enzyme-linked immunoadsorbent assay (ELISA) technique has been developed to facilitate quantitative analysis of the earliest step in the initiation of the extrinsic pathway of coagulation, i.e., complex formation of factor VII/VIIa with tissue factor. The ELISA measures the binding of biotinylated human plasma factor VII to relipidated recombinant human tissue factor. Quantitation of the relative affinity (expressed as IC50) of any factor VII molecular population or structural analogue for tissue factor can be determined by competitive binding. Subnanomolar concentrations of both wild-type recombinant human factor VII (rFVII) and rFVII(R152Q), a mutation at the FVII activation site, competed effectively with biotinylated plasma-derived factor VII in binding to tissue factor. In contrast, the affinity of rFVII(R79Q), a mutation in the first epidermal growth factor-like domain, was 12-fold lower. Following activation of rFVII(R79Q), its affinity for tissue factor and enzymatic activity increased 4-fold and 6-fold, respectively. For wild-type rFVII, enzymatic activity rose significantly following activation. However, its affinity for tissue factor was unchanged. We conclude that both the activation state of factor VII and the mutation of amino-acid residues within the first epidermal growth factor-like domain may alter the affinity of factor VII for tissue factor. 相似文献