全文获取类型
收费全文 | 1721篇 |
免费 | 10篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 47篇 |
金属工艺 | 1篇 |
机械仪表 | 8篇 |
建筑科学 | 17篇 |
能源动力 | 3篇 |
轻工业 | 43篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
无线电 | 11篇 |
一般工业技术 | 26篇 |
冶金工业 | 1494篇 |
原子能技术 | 4篇 |
自动化技术 | 68篇 |
出版年
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 29篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 6篇 |
2009年 | 18篇 |
2008年 | 8篇 |
2007年 | 18篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 10篇 |
1999年 | 32篇 |
1998年 | 415篇 |
1997年 | 281篇 |
1996年 | 157篇 |
1995年 | 105篇 |
1994年 | 78篇 |
1993年 | 95篇 |
1992年 | 14篇 |
1991年 | 11篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 14篇 |
1980年 | 23篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 60篇 |
1976年 | 131篇 |
1975年 | 4篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有1731条查询结果,搜索用时 15 毫秒
991.
992.
AI Spiff V Zabel WH Watson MA Zemaitis AM Ateya DJ Slatkin JE Knapp PL Schiff 《Canadian Metallurgical Quarterly》1981,44(2):160-165
Triclisia dictyophylla Diels (Menispermaceae) is a woody climber indigenous to West Africa which has been used natively as a medicinal in the treatment of several ailments. Chromatography of an extract of the whole plant afforded tridictophylline (3), a new morphinan alkaloid whose structure was established by a consideration of spectral data and confirmed by x-ray crystallographic analysis. The bisbenzylisoquinoline dibenzodioxin alkaloids cocsuline (1) and trigilletimine (2) were also isolated from the same extract. 相似文献
993.
994.
995.
Comprehensive viral immunology of multiple sclerosis. I. Clinical, epidemiological, and CSF studies 总被引:1,自引:0,他引:1
Epidemiological, clinical, and CSF data were collected on 87 patients with clinically definite multiple sclerosis (MS) and 50 with probable MS. As part of a study of immunologic reactivity to viral antigens, a control group separated into 26 patients with probable inflammatory neural disease and 140 with noninflammatory neural disease was similarly studied. Among the groups with MS, females predominated and both Oriental and Spanish surnamed patients were under-represented. The spinal cord, optic nerves, and brainstem were the most common sites of initial disease and more than 20% of the patients had only cord symptoms after several years of disease activity. Of several CSF assays used, determination of oligoclonal IgG bands by agarose electrophoresis was most useful diagnostically. 相似文献
996.
An improved method for extraction and purification of soluble elastin from aortas of copper-deficient swine has been devised. It depends upon the use of both acidic and neutral protease inhibitors during preparation. Collagen is first precipitated with acetic acid. A two-step separation and purification of elastin from the collagen-free extract is based on absorption of the acidic proteins on DEAE-cellulose and gel filtration through agarose. The protein recovered is homogeneous by gel electrophoresis. It has the molecular weight (75,000) and amino acid composition of the soluble elastin from the same source prepared by repeated coacervation. 相似文献
997.
998.
999.
1000.
Observations on the swarming of mosquitoes were conducted in the flood plain forest of South Yamal (67 degrees N.L.). The individuals of A. communis made 83 to 94% of the swarming males. Their number in swarms varied from 30 to 800 specimens. The dynamics of the swarming males number depends on the rate of their emergence from the pupae. At the mass emergence the number of swarming males was 3 times higher though the increase in the general size of the population was negligible. Synchronization of the swarming time of males was also favoured by warm windless weather. 相似文献