全文获取类型
收费全文 | 3737篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 9篇 |
综合类 | 6篇 |
化学工业 | 381篇 |
金属工艺 | 9篇 |
机械仪表 | 8篇 |
建筑科学 | 44篇 |
矿业工程 | 3篇 |
能源动力 | 21篇 |
轻工业 | 96篇 |
水利工程 | 11篇 |
无线电 | 79篇 |
一般工业技术 | 150篇 |
冶金工业 | 2857篇 |
原子能技术 | 14篇 |
自动化技术 | 79篇 |
出版年
2021年 | 17篇 |
2018年 | 15篇 |
2013年 | 39篇 |
2012年 | 26篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 26篇 |
2008年 | 27篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 29篇 |
2003年 | 30篇 |
2002年 | 21篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 127篇 |
1998年 | 929篇 |
1997年 | 534篇 |
1996年 | 357篇 |
1995年 | 188篇 |
1994年 | 151篇 |
1993年 | 200篇 |
1992年 | 21篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 45篇 |
1988年 | 28篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 45篇 |
1983年 | 14篇 |
1982年 | 30篇 |
1981年 | 14篇 |
1980年 | 35篇 |
1978年 | 22篇 |
1977年 | 64篇 |
1976年 | 124篇 |
1975年 | 20篇 |
1974年 | 20篇 |
1973年 | 25篇 |
1972年 | 16篇 |
1971年 | 20篇 |
1970年 | 17篇 |
1969年 | 20篇 |
1967年 | 13篇 |
1966年 | 15篇 |
1965年 | 18篇 |
1962年 | 12篇 |
1961年 | 13篇 |
排序方式: 共有3767条查询结果,搜索用时 62 毫秒
101.
102.
103.
104.
105.
106.
107.
The microbial communities from three upflow anaerobic bioreactors treating purified terephthalic acid (PTA) wastewater were characterized with 16S ribosomal RNA gene sequencing surveys. Universal bacterial and archaeal primers were used to compare the bioreactor communities to each other. A total of 1,733 bacterial sequences and 383 archaeal sequences were characterized. The high number of Syntrophus spp. and Pelotomaculum spp. found within these reactors indicates efficient removal of benzoate and terephthalate. Under anaerobic conditions benzoate can be degraded through syntrophic associations between these bacteria and hydrogen-scavenging microbes, such as Desulfovibrio spp. and hydrogenotrophic methanogens, which remove H(2) to force the thermodynamically unfavourable reactions to take place. The authors did not observe a relatively high percentage of hydrogenotrophic methanogens with the archaeal gene survey because of a high acetate flux (acetate is a main component in PTA wastewater and is the main degradation product of terephthalate/benzoate fermentation), and because of the presence of Desulfovibrio spp. (a sulfate reducer that scavenges hydrogen). The high acetate flux also explains the high percentage of acetoclastic methanogens from the genus Methanosaeta among the archaeal sequences. A group of uncultured bacteria (OD1) may be involved in the degradation of p-toluate (4-methyl benzoate), which is a component of PTA wastewater. 相似文献
108.
TS Frank RE Bartos HK Haefner JA Roberts MD Wilson GP Hubbell 《Canadian Metallurgical Quarterly》1994,7(1):3-8
Eight anticonvulsant drugs-including clonazepam, diazepam and phenobarbital-were tested for their effects on GABA-stimulated chloride uptake in rat cerebral cortical microsacs (unfiltered synaptoneurosomes). "Mid" and "high" therapeutic concentrations were screened, and, if significant enhancement was found, full concentration-response tests were done. In the initial screens, enhancement of GABA-stimulated uptake was found only with phenobarbital, clonazepam and diazepam. In subsequent concentration-response tests, the effects of phenobarbital were found to occur throughout the range of normal, anticonvulsant concentrations, whereas the effects of clonazepam and diazepam were observed only above the concentrations normally used for the chronic control of seizures or anxiety. These data suggest that phenobarbital's anticonvulsant effects are mediated via the GABAA receptor complex, but that the low-dose effects of the benzodiazepines may be mediated via some other mechanism. 相似文献
109.
AP Gonzalez S Sepulveda S Massberg R Baumeister MD Menger 《Canadian Metallurgical Quarterly》1994,58(4):403-408
With the use of in vivo fluorescence microscopy we have analyzed microvascular reperfusion injury of small bowel isograft transplants in rats. Following 1 hr cold storage in University of Wisconsin solution, the small bowel was transplanted heterotopically, and the intestinal microcirculation was quantitatively analyzed 20-60 min after onset of reperfusion. The intestinal grafts' capillary perfusion of both the mucosa and the circular and longitudinal muscles was not found altered when compared with the intestinal capillary perfusion of sham-operated controls. In contrast, leukocyte-endothelial cell interaction, including leukocyte rolling (40 +/- 5%) and sticking (280 +/- 100 mm-2) in submucosal postcapillary venules, was significantly increased when compared with nontransplanted controls (12 +/- 8% and 20 +/- 10 mm-2, P < 0.01 and P < 0.05, respectively). Leukocyte-endothelial cell interaction was associated with a marked alteration of lymphatic capillary drainage, as indicated by the low functional density of lymphatic microvessels of 10.2 +/- 6.1 cm-1 (P < 0.01 vs. sham-operated controls (39.2 +/- 6.1 cm-1)). From these results we propose that leukocyte-endothelial cell interaction, not capillary "no-reflow," is the primary step in the manifestation of microvascular reperfusion injury following a short period of cold ischemia in small bowel grafts. 相似文献
110.
M Fernández J Cao MD Vázquez-Illanes JI Ramos-Martínez JA Villamarín 《Canadian Metallurgical Quarterly》1994,33(2):355-363
Phosphofructokinase purified from mantle tissue of the sea mussel Mytilus galloprovincialis, was phosphorylated "in vitro" by the catalytic subunit of cyclic AMP-dependent protein kinase. The incorporation of phosphate gave rise to an activation of the enzyme by increasing its affinity for fructose-6-phosphate, by decreasing its sensitivity to the inhibition by ATP and by enhancing the effect of allosteric activators (5'-AMP and fructose-2,6-bisphosphate). In addition, the effects of phosphorylation on the catalytic activity are pH-dependent. 相似文献