全文获取类型
收费全文 | 4535篇 |
免费 | 3篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 69篇 |
金属工艺 | 2篇 |
机械仪表 | 8篇 |
建筑科学 | 20篇 |
矿业工程 | 1篇 |
能源动力 | 4篇 |
轻工业 | 21篇 |
水利工程 | 5篇 |
无线电 | 27篇 |
一般工业技术 | 75篇 |
冶金工业 | 4259篇 |
原子能技术 | 2篇 |
自动化技术 | 43篇 |
出版年
2019年 | 2篇 |
2018年 | 3篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 16篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 3篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 148篇 |
1998年 | 1427篇 |
1997年 | 802篇 |
1996年 | 519篇 |
1995年 | 267篇 |
1994年 | 244篇 |
1993年 | 255篇 |
1992年 | 37篇 |
1991年 | 46篇 |
1990年 | 38篇 |
1989年 | 51篇 |
1988年 | 52篇 |
1987年 | 32篇 |
1986年 | 30篇 |
1985年 | 26篇 |
1984年 | 7篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 37篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 84篇 |
1976年 | 199篇 |
1975年 | 9篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有4538条查询结果,搜索用时 31 毫秒
51.
1. In the present study, we evaluated the role of repeated administration on conditioning place preference (CPP) induced by fencamfamine (FCF) in male rats. 2. Repeated FCF (3.5 mg/kg) or saline once or daily for ten consecutive days enhanced sniffing duration and decreased locomotion and rearing duration. 3. At the 3.5 mg/kg dose, FCF produced a significant place-preference effect. 4. Repeated exposures to FCF intensified its reinforcing properties. 5. These results suggest that repeated FCF administration sensitizes its rewarding effects, as with other addictive substances. 相似文献
52.
53.
54.
55.
56.
The cytoskeletal components of hamster oocytes, zygotes, and spontaneously activated parthogenotes were examined after immunocytochemical labeling. Microtubules were found only in the anastral, tangentially arranged second meiotic spindle of unfertilized oocytes. Taxol treatment of unfertilized oocytes greatly augmented astral microtubules in both the metaphase II spindle and the cortex. Disruption of the meiotic spindle microtubules with nocodazole resulted in cortical chromosomal scattering. During hamster sperm incorporation and pronuclear formation, no sperm aster was detected in association with the male DNA. Instead, a large overlapping array of microtubules assembled in the cortex. By mitosis, this interphase array disassembled and an anastral metaphase spindle formed. Microtubule and chromatin configurations were also imaged in hamster oocytes injected with human sperm. Astral microtubules were absent from the sperm centrosome. The implications of these results are discussed in relation to the hamster oocyte penetration assay, a test commonly used by in vitro fertilization clinics to demonstrate the fertilizing ability of human sperm. We conclude that since hamsters and humans follow different methods of centrosome inheritance, maternal and paternal, respectively, the hamster may be an inappropriate model for exploring microtubule and centrosomal defects in humans or for assaying postinsemination forms of human male fertility defects. 相似文献
57.
AP West PJ Bjorkman DA Dougherty HA Lester 《Canadian Metallurgical Quarterly》1997,272(41):25468-25473
To provide material suitable for structural studies of the nicotinic acetylcholine receptor, we have expressed and purified the NH2-terminal extracellular domain of the mouse muscle alpha subunit. Several constructs were initially investigated using Xenopus oocytes as a convenient small scale expression system. A fusion protein (alpha210GPI) consisting of the 210 NH2-terminal amino acids of the alpha subunit and a glycosylphosphatidylinositol anchorage sequence conferred surface alpha-bungarotoxin binding in oocytes. Coexpression of alpha210GPI with an analogous construct made from the delta subunit showed no evidence of heterodimer formation. The alpha210GPI protein was chosen for large scale expression in transfected Chinese hamster ovary cells. The alpha210GPI protein was cleaved from these cells and purified on an immunoaffinity column. Gel and column chromatography show that the purified protein is processed as expected and exists as a monomer. The purified protein also retains the two distinct, conformation-specific binding sites expected for the correctly folded alpha subunit. Circular dichroism studies of alpha210GPI suggest that this region of the receptor includes considerable beta-sheet secondary structure, with a small proportion of alpha-helix. 相似文献
58.
59.
60.