全文获取类型
收费全文 | 1882篇 |
免费 | 11篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 91篇 |
金属工艺 | 65篇 |
机械仪表 | 7篇 |
建筑科学 | 40篇 |
能源动力 | 32篇 |
轻工业 | 68篇 |
水利工程 | 5篇 |
无线电 | 119篇 |
一般工业技术 | 103篇 |
冶金工业 | 1312篇 |
原子能技术 | 5篇 |
自动化技术 | 41篇 |
出版年
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 32篇 |
2009年 | 28篇 |
2008年 | 30篇 |
2007年 | 31篇 |
2006年 | 36篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 22篇 |
2002年 | 21篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 58篇 |
1998年 | 392篇 |
1997年 | 218篇 |
1996年 | 146篇 |
1995年 | 73篇 |
1994年 | 78篇 |
1993年 | 90篇 |
1992年 | 24篇 |
1991年 | 25篇 |
1990年 | 16篇 |
1989年 | 26篇 |
1988年 | 32篇 |
1987年 | 17篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 37篇 |
1976年 | 110篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有1893条查询结果,搜索用时 10 毫秒
91.
92.
93.
94.
Granestrand P. Lagerstrom B. Svensson P. Thylen L. Stoltz B. Bergvall K. Olofsson H. 《Electronics letters》1988,24(19):1198-1200
Reports on the performance of a 4×4 polarisation-independent LiNbO3 switch matrix with a `tree-structure', permitting strictly nonblocking communicative as well as distributive switching 相似文献
95.
S. Mustorp C. Engdahl-Axelsson U. Svensson A. Holck 《European Food Research and Technology》2008,226(4):771-778
Legislation requires labelling of foods containing allergic ingredients, amongst them celery, mustard and sesame. Here we present robust quantitative and sensitive methods for real-time PCR detection of celery, mustard (Sinapis alba and Brassica sp.) and sesame in food. The development of the DNA-based assays was part of an effort to generate alternative detection methods for allergens for which effective protein-based assays are lacking. The celery and sesame methods were specific for the celery mannitol dehydrogenase gene and the sesame allergen encoding 2S albumin gene, respectively, when tested against a range of plant materials. The mustard method was specific for the allergen encoding sinA gene and its homologues present in different Brassica sp. All primer probe pairs gave high amplification efficiency and sensitivities below approximately ten molecules of purified template DNA. These DNA-based detection methods will constitute supplementary and complementary methods to the traditional protein-based methods. Laboratories may choose different analysis formats depending on the food matrix, the availability of specific tests and the performance characteristics of the tests. 相似文献
96.
97.
High threshold voltage-dependent P- and Q-type calcium channels are involved in neurotransmitter release. In order to investigate the role of P- and Q-type calcium channels in the mechanosensory (nociceptive) processing in the spinal cord, their participation in the responses of spinal wide-dynamic-range neurons to innocuous and noxious mechanical stimulation of the knee and ankle joints was studied in 30 anaesthetized rats. The knee was either normal or acutely inflamed by kaolin/carrageenan. During the topical application of omega-agatoxin IVA (P-type channel antagonist, 0.1 microM) onto the dorsal surface of the spinal cord, the responses to innocuous and noxious pressure applied to the normal knee were increased to respectively 124 +/- 42% and 114 +/- 23% of predrug values (mean +/- SD, P < 0.05, 14 neurons). By contrast, in rats with an inflamed knee, the responses to innocuous and noxious pressure applied to the knee were reduced to respectively 72 +/- 19 and 73 +/- 22% of baseline (mean +/- SD, P < 0.01, 13 neurons). In the same neurons, omega-agatoxin IVA slightly increased the responses to pressure on the non-inflamed ankle whether the knee was normal or inflamed. Thus P-type calcium channels seem to acquire a predominant importance in the excitation of spinal cord neurons by mechanosensory input from inflamed tissue and hence in the generation of inflammatory pain. By contrast, the Q-type channel antagonist, omega-conotoxin MVIIC (1 or 100 microM), had no significant effect upon responses to innocuous or noxious pressure applied to either normal or inflamed knees (25 neurons). 相似文献
98.
OBJECTIVES: Research has been oriented toward elucidating the links between religion and mental health. The purpose of this article is to further our knowledge in this area by examining the effect of religious activity on depressive symptomatology among community-dwelling elderly persons with cancer. We also test whether these effects differ between Blacks and Whites. METHODS: We use two waves of data collected from a community-dwelling sample of elderly persons living in North Carolina. Depressive symptomatology is measured using four subscales from the CES-D 20 scale: somatic-retarded activity, depressed affect, positive affect, and interpersonal relations. Measures of religious activity include service attendance, religious devotion, and watching or listening to religious programs. RESULTS: The findings indicate that among Blacks with cancer, religious activity is related to lower levels of depressive symptomatology; no such relationship is found for respondent with other illnesses or no illness. Further, the effects of religious activity are stronger among Blacks than Whites. DISCUSSION: The analyses lend support to the hypothesis that religious activity is a strong predictor of depression in elderly adults with cancer. This finding, however, is not as strong as we had anticipated. 相似文献
99.
100.
J Keane MK Balcewicz-Sablinska HG Remold GL Chupp BB Meek MJ Fenton H Kornfeld 《Canadian Metallurgical Quarterly》1997,65(1):298-304
The effect of Mycobacterium tuberculosis infection on the viability of healthy (control) human alveolar macrophages was evaluated by staining with ethidium homodimer and calcein to discriminate live from dead cells. Infection with M. tuberculosis H37Ra or H37Rv increased macrophage mortality at 6 days from the control level of 3.8% +/- 0.7% to 28.7% +/- 6.9% or 12.6% +/- 3.1%, respectively (P < 0.001 for comparisons of all conditions). A role for tumor necrosis factor alpha (TNF-alpha) in the M. tuberculosis-induced cytolysis of alveolar macrophages was demonstrated by increased cytotoxicity following the addition of exogenous TNF-alpha to the cultures and by enhancement of macrophage survival when M. tuberculosis-infected alveolar macrophages were treated with pentoxifylline or anti-TNF-alpha antibody. The cytolytic mechanism was determined to be apoptosis by the demonstration of a characteristic internucleosomal ladder of genomic DNA by agarose gel electrophoresis, by finding nuclear fragmentation and condensation by electron microscopy, and by in situ terminal transferase-mediated nick end labeling of fragmented DNA in alveolar macrophages infected with M. tuberculosis in vitro. The latter technique was employed to reveal extensive apoptosis within caseating granulomas from lung tissue samples from clinical tuberculosis cases. The induction of apoptosis in alveolar macrophages by M. tuberculosis may play a role in the macrophage-pathogen interaction of tuberculosis in vivo. 相似文献