全文获取类型
收费全文 | 75945篇 |
免费 | 854篇 |
国内免费 | 689篇 |
专业分类
电工技术 | 1444篇 |
综合类 | 47篇 |
化学工业 | 11353篇 |
金属工艺 | 3510篇 |
机械仪表 | 2653篇 |
建筑科学 | 1700篇 |
矿业工程 | 503篇 |
能源动力 | 1892篇 |
轻工业 | 6500篇 |
水利工程 | 849篇 |
石油天然气 | 2307篇 |
武器工业 | 41篇 |
无线电 | 7334篇 |
一般工业技术 | 16655篇 |
冶金工业 | 12705篇 |
原子能技术 | 2631篇 |
自动化技术 | 5364篇 |
出版年
2022年 | 582篇 |
2021年 | 921篇 |
2020年 | 706篇 |
2019年 | 788篇 |
2018年 | 1563篇 |
2017年 | 1583篇 |
2016年 | 1779篇 |
2015年 | 976篇 |
2014年 | 1585篇 |
2013年 | 3615篇 |
2012年 | 2396篇 |
2011年 | 2878篇 |
2010年 | 2415篇 |
2009年 | 2689篇 |
2008年 | 2668篇 |
2007年 | 2607篇 |
2006年 | 2221篇 |
2005年 | 1955篇 |
2004年 | 1878篇 |
2003年 | 1828篇 |
2002年 | 1745篇 |
2001年 | 1705篇 |
2000年 | 1693篇 |
1999年 | 1608篇 |
1998年 | 3765篇 |
1997年 | 2652篇 |
1996年 | 1986篇 |
1995年 | 1562篇 |
1994年 | 1374篇 |
1993年 | 1380篇 |
1992年 | 1009篇 |
1991年 | 1063篇 |
1990年 | 1087篇 |
1989年 | 1062篇 |
1988年 | 950篇 |
1987年 | 883篇 |
1986年 | 883篇 |
1985年 | 945篇 |
1984年 | 786篇 |
1983年 | 769篇 |
1982年 | 681篇 |
1981年 | 697篇 |
1980年 | 666篇 |
1979年 | 653篇 |
1978年 | 625篇 |
1977年 | 779篇 |
1976年 | 948篇 |
1975年 | 583篇 |
1974年 | 554篇 |
1973年 | 547篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
The solutions of the direct and inverse problems of electromagnetic diagnostics of laminated materials with the use of a rectangular waveguide as a radiator are presented. The direct problem, i.e., the problem of finding the coefficient of reflection of electromagnetic waves, is solved by using a method based on the computation of the energy flow through the aperture of a waveguide. The method of global minimization was applied to solve the inverse problem, i.e., to find the parameters of the material for given reflection coefficients measured at various frequencies.Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 2, pp. 26–33, March–April, 1994. 相似文献
952.
NADPH diaphorase histochemistry is commonly used to identify cells containing nitric oxide synthase (NOS), the enzyme catalyzing the production of nitric oxide from L-arginine. NADPH diaphorase activity and NOS immunostaining was demonstrated in different cells of the vertebrate retina; photoreceptors, horizontal cells, amacrine cells, ganglion cells, and Müller cells. However, the physiological role of nitric oxide (NO) in the retina has yet to be elucidated. In this study, we tested the assumption that NADPH diaphorase activity in the retinas of rabbits and rats depended on the state of visual adaptation. In the rabbit, light adaptation enhanced NADPH diaphorase activity in amacrine cells and practically eliminated it in horizontal cells. Dark adaptation induced the opposite effects; the NADPH diaphorase activity was reduced in amacrine cells and enhanced in horizontal cells. Retinas from eyes that were injected intravitreally with L-glutamate exhibited a pattern of NADPH diaphorase activity that was similar to that seen in dark-adapted retinas. In rats, the NADPH diaphorase activity of amacrine and horizontal cells exhibited adaptation dependency similar to that of the rabbit retina. But, the most pronounced effect of dark adaptation in the rat's retina was an enhancement of NADPH diaphorase activity in Müller cells, especially of the endfoot region. Assuming that NADPH diaphorase activity is a marker for NOS, these findings suggest that NO production in the mammalian retina is modulated by the level of ambient illumination and support the notion that NO plays a physiological role in the retina. 相似文献
953.
Journal of Electronic Materials - Low pressure chemical vapor deposition (LPCVD) of tungsten (W) by SiH4 reduction of WF6 on Si(100) surfaces was studied in a single-wafer, cold-wall reactor over a... 相似文献
954.
955.
956.
957.
958.
We describe the case of a patient who developed bilateral loss of hearing during intravenous treatment with erythromycin. Predisposing factors may have been reduced renal and hepatic function and treatment with diuretics and aminoglycosides. Recovery was late, but hearing was probably restored to almost pre-treatment level. Patients receiving high doses of erythromycin should, as a routine, be questioned about hearing loss and tinnitus. 相似文献
959.
G Testa RM Goldstein A Toughanipour O Abbasoglu R Jeyarajah MF Levy BS Husberg TA Gonwa GB Klintmalm 《Canadian Metallurgical Quarterly》1998,227(4):590-599
The ability to acquire a motor and cognitive skill was investigated in 26 patients with schizophrenia and 26 normal participants using repeated testing on the Tower of Toronto puzzle. Seven patients with defective performance were retested using additional trials and immediate feedback designed to facilitate problem solving. A component analysis of performance was used based on J. R. Anderson's (1987) model of cognitive skill learning. Patients exhibited a performance deficit on both motor and cognitive skills. However, their acquisition rate was similar to that of normal participants on most parameters, indicating that skill learning suffered little or no impairment. Performance deficit was accounted for by poor problem-solving ability, explicit memory, and general intellectual capacities. It was remediable in some, but not all, patients. Remediation failure was also related to severe defects of cognitive functions. 相似文献
960.
M Majer DM Mott H Mochizuki JC Rowles O Pedersen WC Knowler C Bogardus M Prochazka 《Canadian Metallurgical Quarterly》1996,39(3):314-321
Skeletal muscle glycogen synthase (encoded by GYS1 on chromosome 19q13.3) is the rate-limiting enzyme in insulin-mediated non-oxidative glucose disposal. Our previous studies have demonstrated an impairment of insulin-stimulated GYS1 activities in insulin-resistant Pima Indians, and associations of non-insulin-dependent diabetes mellitus (NIDDM) with the GYS1 locus were reported recently in Finnish and Japanese populations. We have performed linkage and association analyses of GYS1 and seven additional DNA markers on 19q with NIDDM, and with parameters of insulin action in the Pima Indians. We have found a significant association of NIDDM with GYS1 genotypes (p = 0.009), and with common GYS1 alleles (p = 0.022) in the Pima Indians. We have performed a detailed comparative analysis of the GYS1 gene, mRNA, and protein product in insulin-sensitive and insulin-resistant Pima Indians. No mutations in GYS1 coding sequences were detected; nor did we find alterations of GYS1 mRNA expression or of its basal enzymatic activity in insulin-resistant Pima Indians. These results contrasted with a 25% reduction of immunoreactive protein in insulin-resistant subjects as detected by Western blotting with an antibody specific for the C-terminal end of GYS1 (t-test p = 0.024; Wilcoxon's rank-sum test, p = 0.04). Because no mutations were detected in the DNA encoding this epitope, the difference in immunoreactivity may reflect post-translational modification(s) of the protein rather than a difference in the gene itself, or it could have occurred by chance. We conclude that our data do not indicate alterations in the GYS1 gene as the cause for the observed association, and that a different locus near GYS1 may be the contributing genetic element. 相似文献