全文获取类型
收费全文 | 1756篇 |
免费 | 8篇 |
专业分类
电工技术 | 12篇 |
综合类 | 2篇 |
化学工业 | 37篇 |
金属工艺 | 3篇 |
机械仪表 | 7篇 |
建筑科学 | 7篇 |
能源动力 | 4篇 |
轻工业 | 26篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 13篇 |
一般工业技术 | 27篇 |
冶金工业 | 1579篇 |
原子能技术 | 8篇 |
自动化技术 | 34篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2017年 | 3篇 |
2014年 | 5篇 |
2013年 | 16篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 49篇 |
1998年 | 489篇 |
1997年 | 257篇 |
1996年 | 184篇 |
1995年 | 122篇 |
1994年 | 91篇 |
1993年 | 87篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 20篇 |
1989年 | 24篇 |
1988年 | 27篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 52篇 |
1976年 | 97篇 |
1975年 | 8篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1955年 | 2篇 |
1890年 | 4篇 |
1882年 | 2篇 |
排序方式: 共有1764条查询结果,搜索用时 218 毫秒
111.
Grigsby Jim; Kaye Kathryn; Kowalsky Jacqueline; Kramer Andrew M. 《Canadian Metallurgical Quarterly》2002,47(3):291
Objective: To assess the relationship between behavioral self-regulation and functional status among older rehabilitation inpatients. Study Design: Prospective outcome study. Setting: Fourteen inpatient rehabilitation units and skilled nursing facilities. Participants: Two hundred twelve older adults following hip fracture or replacement. Measures: Mini Mental State Exam (MMSE), Geriatric Depression Scale, Behavioral Dyscontrol Scale (BDS), and nurse-rated functioning on activities of daily living (ADLs) and the Barthel Index. Results: Risk-adjusted analyses found the BDS to be strongly associated with all 11 ADLs and the Barthel Index. The MMSE made an additional contribution to 4 models. Conclusion: The results suggest that the ability to use intentions to guide purposeful behavior is an important contributor to functioning among older adults, affecting rehabilitation potential. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
112.
113.
D Li U Sreenivasan N Juranic S Macura FJ Puga PM Frohnert PH Axelsen 《Canadian Metallurgical Quarterly》1997,10(2):73-87
The antimicrobial activity of vancomycin and related glycopeptide antibiotics is due to stereospecific recognition of polypeptide components in bacterial cell walls. To better understand how these antibiotics recognize polypeptide determinants, we have developed dynamic models of the complexes formed by the vancomycin aglycon and two different dipeptide ligands, Ac-D-ala-D-ala and Ac-D-ala-gly. Molecular dynamics simulations of the two complexes, initially conditioned with distance constraints derived from two-dimensional nuclear magnetic resonance (NMR) studies, are conformationally stable and propagate in a manner consistent with the NMR-derived constraints after the constraints are removed. Free energy calculations accurately predict the relative binding affinity of these two complexes and help validate the simulation models for detailed structural analysis. Although the two ligands adopt similar conformations when bound to the antibiotic, there are clear differences in the configuration of intermolecular hydrogen bonds, the overall shape of the antibiotic, and other structural features of the two complexes. This analysis illustrates how complex structural and dynamic factors interrelate and contribute to differences in binding affinity. 相似文献
114.
115.
116.
117.
118.
119.
Sam Millet Christel PH Moons Monique J Van Oeckel Geert PJ Janssens 《Journal of the science of food and agriculture》2005,85(5):709-719
Conventional husbandry systems for pork production are scrutinized by members of the general public as well as the scientific community. As a response, alternative forms of pig production, such as outdoor housing, organic farming and environmental enrichment are gaining interest. The question arises whether these production systems are indeed able to improve the welfare and health status of the animals, and whether these production systems alter production characteristics and meat or carcass traits. Measures of poor welfare have been described, but evaluating overall welfare is difficult. Certain parameters of alternative housing will improve welfare in some ways but, simultaneously, other welfare problems are inflated, and the weighting of each of these problems is very subjective. Alternative housing systems allow pigs to display species‐specific behaviour and decrease the occurrence of abnormal behaviours by acting on several parameters: indoor versus outdoor housing, floor space/density, floor type, and provision of bedding or other types of environmental enrichment. Evaluating alternative housing systems should be done by looking at all the welfare‐improving factors and the cost of alleviating welfare‐decreasing problems in a given production system. Data in the literature on growth, meat and carcass traits in alternative production systems, are inconsistent, indicating that other factors can play an important role. However, as equal, or in some cases even better, performance can be attained in certain production systems that meet concerns of animal welfare scientists and members of the general public, alternative production forms may be considered preferable. Copyright © 2005 Society of Chemical Industry 相似文献
120.
Irina I Koleva Jozef PH Linssen Teris A van Beek Lyuba N Evstatieva Vessela Kortenska Nedyalka Handjieva 《Journal of the science of food and agriculture》2003,83(8):809-819
Plant samples from several species and populations of the genus Sideritis (Labiatae) grown in Bulgaria (S scardica, S syriaca and S montana) were extracted with different solvents. Their antioxidant activities were determined by the β‐carotene bleaching test (BCBT), 2,2′‐diphenyl‐1‐picrylhydrazyl (DPPH?) radical scavenging method and static headspace gas chromatography (HS‐GC) and compared with the antioxidant activity of two reference compounds of different polarity, viz butylated hydroxytoluene (BHT) and rosmarinic acid. The pure reference compounds were applied in a ten‐times lower concentration than the plant extracts. The highest antioxidant activity in the BCBT, close to that of BHT, was observed for the more apolar extracts. The inhibitory effect on β‐carotene bleaching of the polar extracts and rosmarinic acid was much lower than that of BHT. The inhibition of hexanal formation in bulk safflower oil by most of S syriaca and S scardica extracts was as effective as BHT but less so than rosmarinic acid. S montana extracts showed weak antioxidant or even pro‐oxidant properties. Extracts from butanol and from ethyl acetate and the total methanol extracts from all Sideritis plants studied showed a strong radical scavenging activity against DPPH?, close to that of rosmarinic acid. S montana extracts were, as a whole, slightly weaker radical inhibitors than the extracts from the other two species. The antioxidant activity of Sideritis extracts was attributed to the presence of flavonoid and phenylpropanoid glycosides. Copyright © 2003 Society of Chemical Industry 相似文献