全文获取类型
收费全文 | 7218篇 |
免费 | 410篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 37篇 |
综合类 | 3篇 |
化学工业 | 926篇 |
金属工艺 | 113篇 |
机械仪表 | 177篇 |
建筑科学 | 134篇 |
矿业工程 | 7篇 |
能源动力 | 86篇 |
轻工业 | 512篇 |
水利工程 | 31篇 |
石油天然气 | 12篇 |
无线电 | 396篇 |
一般工业技术 | 742篇 |
冶金工业 | 3816篇 |
原子能技术 | 27篇 |
自动化技术 | 622篇 |
出版年
2024年 | 12篇 |
2023年 | 58篇 |
2022年 | 107篇 |
2021年 | 175篇 |
2020年 | 144篇 |
2019年 | 138篇 |
2018年 | 199篇 |
2017年 | 198篇 |
2016年 | 225篇 |
2015年 | 153篇 |
2014年 | 202篇 |
2013年 | 282篇 |
2012年 | 272篇 |
2011年 | 294篇 |
2010年 | 218篇 |
2009年 | 203篇 |
2008年 | 192篇 |
2007年 | 146篇 |
2006年 | 92篇 |
2005年 | 97篇 |
2004年 | 67篇 |
2003年 | 67篇 |
2002年 | 61篇 |
2001年 | 49篇 |
2000年 | 34篇 |
1999年 | 159篇 |
1998年 | 1288篇 |
1997年 | 708篇 |
1996年 | 429篇 |
1995年 | 261篇 |
1994年 | 210篇 |
1993年 | 252篇 |
1992年 | 51篇 |
1991年 | 65篇 |
1990年 | 53篇 |
1989年 | 39篇 |
1988年 | 34篇 |
1987年 | 50篇 |
1986年 | 26篇 |
1985年 | 32篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 72篇 |
1976年 | 118篇 |
1975年 | 5篇 |
排序方式: 共有7641条查询结果,搜索用时 21 毫秒
71.
72.
The flow and fracture behavior of Be-Al alloys were determined in tension with different levels of superimposed pressure.
The Be-Al alloys were prepared by Brush Wellman, Inc. (Cleveland, OH) from prealloyed powders processed to either a hot isostatically
pressed (“hipped”) or cold isostatically pressed and extruded condition. Significant effects of pressure on both the flow
and ductility have been observed at room temperature, with implications on the formability of these materials. The effects
of changes in processing conditions and stress state on the flow and fracture behavior are summarized in addition to both
optical and scanning electron microscopy (SEM) examination of the fracture surfaces. Separate other studies on the alloy constituents
(e.g., Al and Be) are also reported. The results are also compared to previous works on monolithic materials and composites tested
with high pressure. 相似文献
73.
MS Oitzl ER de Kloet M Jo?ls W Schmid TJ Cole 《Canadian Metallurgical Quarterly》1997,9(11):2284-2296
Previous studies in rats using the Morris water maze suggested that the processing of spatial information is modulated by corticosteroid hormones through mineralocorticoid and glucocorticoid receptors in the hippocampus. Mineralocorticoid receptors appear to be involved in the modulation of explorative behaviour, while additional activation of glucocorticoid receptors facilitates the storage of information. In the present study we used the water maze task to examine spatial learning and memory in mice homozygous and heterozygous for a targeted disruption of the glucocorticoid receptor gene. Compared with wild-type controls, homozygous and heterozygous mice were impaired in the processing of spatial but not visual information. Homozygous mutants performed variably during training, without specific platform-directed search strategies. The spatial learning disability was partly compensated for by increased motor activity. The deficits were indicative of a dysfunction of glucocorticoid receptors as well as of mineralocorticoid receptors. Although the heterozygous mice performed similarly to wild-type mice with respect to latency to find the platform, their strategy was more similar to that of the homozygous mice. Glucocorticoid receptor-related long-term spatial memory was impaired. The increased behavioural reactivity of the heterozygous mice in the open field points to a more prominent mineralocorticoid receptor-mediated function. The findings indicate that (i) the glucocorticoid receptor is of critical importance for the control of spatial behavioural functions, and (ii) mineralocorticoid receptor-mediated effects on this behaviour require interaction with functional glucocorticoid receptors. Until the development of site-specific, inducible glucocorticoid receptor mutants, glucocorticoid receptor-knockout mice present the only animal model for the study of corticosteroid-mediated effects in the complete absence of a functional receptor. 相似文献
74.
75.
A 10-year-old, previously healthy female presented to the emergency department via emergency medical service transport, with her tongue tightly entrapped inside a glass bottle (9 oz, Yoohoo brand of chocolate drink). The tongue was massively edematous and ecchymotic due to impaired venous return from constriction by the neck of the bottle. After repeated attempts at mechanically reducing the tongue out of the bottle, a professional glazier was contacted, who was able to remove the bottle in the operating room with a steel glass cutter. Needle evacuation of a small hematoma was then performed to decrease the pressure ischemia to the tongue, which began to improve quickly. 相似文献
76.
77.
78.
SO Trertola SJ Savader CA Prescott FA Osterman 《Canadian Metallurgical Quarterly》1993,189(1):285-286
A simple commercially available compression device allowed intermittent ultrasound scanning of the compression site during compression repair of a femoral artery pseudoaneurysm in six patients. All six of the pseudoaneurysms (five superficial femoral and one common femoral) were compressed without compression of the underlying vessels. The procedure was successful in four of the six patients, without complications. Use of this device may decrease operator fatigue during compression repair of pseudoaneurysm. 相似文献
79.
80.
Molecular cloning of a novel melanocortin receptor 总被引:2,自引:0,他引:2
I Gantz Y Konda T Tashiro Y Shimoto H Miwa G Munzert SJ Watson J DelValle T Yamada 《Canadian Metallurgical Quarterly》1993,268(11):8246-8250
Using the technique of the polymerase chain reaction primed with oligonucleotides based on the homologous transmembrane regions of seven transmembrane G protein-linked receptors, we isolated three full-length human genes that encode a novel subgroup of this receptor family. Recently, two of these receptors were identified as specific for alpha-melanocyte-stimulating hormone (alpha-MSH) and adrenocorticotropic hormone. We report the molecular cloning and pharmacologic characterization of a third member of this subgroup. The gene for this receptor encodes a protein of 361 amino acids in length. Its pharmacology characterizes it as an MSH receptor specific to the heptapeptide core common to adrenocorticotropic hormone and alpha-, beta-, and gamma-MSH. By Northern blot hybridization and polymerase chain reaction, it is expressed in brain, placental, and gut tissues but not in melanoma cells or in the adrenal gland. These findings may yield insight into the physiology of peptides derived from pro-opiomelanocortin post-translational processing. 相似文献