全文获取类型
收费全文 | 573286篇 |
免费 | 6649篇 |
国内免费 | 1019篇 |
专业分类
电工技术 | 10718篇 |
综合类 | 498篇 |
化学工业 | 91600篇 |
金属工艺 | 23516篇 |
机械仪表 | 18683篇 |
建筑科学 | 12752篇 |
矿业工程 | 4347篇 |
能源动力 | 14657篇 |
轻工业 | 46719篇 |
水利工程 | 6989篇 |
石油天然气 | 15002篇 |
武器工业 | 40篇 |
无线电 | 60662篇 |
一般工业技术 | 117676篇 |
冶金工业 | 95710篇 |
原子能技术 | 14731篇 |
自动化技术 | 46654篇 |
出版年
2021年 | 5659篇 |
2020年 | 4173篇 |
2019年 | 5427篇 |
2018年 | 9501篇 |
2017年 | 9690篇 |
2016年 | 10162篇 |
2015年 | 6274篇 |
2014年 | 10585篇 |
2013年 | 26790篇 |
2012年 | 16206篇 |
2011年 | 21580篇 |
2010年 | 17349篇 |
2009年 | 19139篇 |
2008年 | 19320篇 |
2007年 | 18985篇 |
2006年 | 16432篇 |
2005年 | 14902篇 |
2004年 | 14100篇 |
2003年 | 13816篇 |
2002年 | 13377篇 |
2001年 | 12948篇 |
2000年 | 12393篇 |
1999年 | 12070篇 |
1998年 | 27718篇 |
1997年 | 20106篇 |
1996年 | 15691篇 |
1995年 | 12046篇 |
1994年 | 10912篇 |
1993年 | 10658篇 |
1992年 | 8370篇 |
1991年 | 8138篇 |
1990年 | 8024篇 |
1989年 | 7797篇 |
1988年 | 7501篇 |
1987年 | 6771篇 |
1986年 | 6561篇 |
1985年 | 7438篇 |
1984年 | 6753篇 |
1983年 | 6487篇 |
1982年 | 5824篇 |
1981年 | 5942篇 |
1980年 | 5677篇 |
1979年 | 5772篇 |
1978年 | 5699篇 |
1977年 | 6209篇 |
1976年 | 7718篇 |
1975年 | 5134篇 |
1974年 | 4922篇 |
1973年 | 5004篇 |
1972年 | 4292篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Discusses common presenting complaints and those of emergent significance that have an organic etiology. The following categories are discussed: head, eyes, ears, throat, neck, cardiac, respiratory, gastrointestinal, genito-urinary, musculoskeletal, and neurologic complaints. It is suggested that many therapists lack adequate medical information to suspect the presence of organic problems when symptoms are indistinguishable from psychogenic/psychosomatic problems. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
R. Toledo-Marin F.A. Cruz-Perez L. Ortigoza-Guerrero 《Electronics letters》2007,43(7):399-401
A new mathematical method to analyse the performance of guard-channel-based strategies is proposed. The analysis is based on the iterative calculation of the average effective channel holding time. The method presented provides higher accuracy than alternative solutions previously reported in the literature 相似文献
994.
We have assessed the antimicrobial, vapor-phase activity of the following natural essential oils (EOs) when used in paraffin-based “active coatings” for paper packaging materials intended to come into contact with foods: clove (Sygzium aromaticum), cinnamon (Cinnamomum zeylanicum), and oregano (Origanum vulgare) EOs, and cinnamaldehyde-enriched cinnamon EO. To our knowledge, this is the first time that such an approach has been presented for consideration by the scientific community. 相似文献
995.
996.
P M Reid A E Wilkinson K C Leung M N Jones 《Computer applications in the biosciences》1989,5(2):133-135
Analytical ultracentrifugation is commonly used for the determination of molecular weights (sedimentation equilibrium) and sedimentation coefficients (sedimentation rate) of biological macromolecules in solution. A Turbo Pascal program for the analysis of sedimentation equilibrium centrifugation data produced by absorbance optical systems is described. The user may enter data from a scan of absorbance versus distance from the centre of rotation, via a graphics tablet (or ASCII file). This is subsequently manipulated to yield an apparent weight average molecular weight for the given sample. Plots of ln (absorbance) versus (radius2) may also be produced. The method described uses readily available computational equipment requiring only a graphics tablet in addition to an IBM PC compatible computer. This technique and the software developed have been used to investigate the molecular weight range of two International Humic Substances Society (IHSS) reference samples from the Suwannee River. 相似文献
997.
998.
The conclusions are put forward that are adopted by a discussion group preparing the framework for a limitation policy of the radon problem in Belgium. Existing and future situations are treated in a coherent policy that is adequate for practical implementation. An action level is defined, together with a hierachy of levels for new constructions. The decision logic for the acceptance of building materials is explained. 相似文献
999.
V. A. Pilipovich V. L. Malevich G. D. Ivlev V. V. Zhidkov 《Journal of Engineering Physics and Thermophysics》1985,48(2):228-233
On the basis of a numerical solution of the Stefan problem, the dynamics of nanosecond laser annealing of silicon is investigated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 306–312, February, 1985. 相似文献
1000.