首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   778篇
  免费   21篇
  国内免费   3篇
电工技术   68篇
综合类   1篇
化学工业   144篇
金属工艺   9篇
机械仪表   10篇
建筑科学   8篇
能源动力   9篇
轻工业   74篇
水利工程   1篇
石油天然气   1篇
无线电   48篇
一般工业技术   127篇
冶金工业   240篇
原子能技术   16篇
自动化技术   46篇
  2023年   5篇
  2021年   8篇
  2020年   7篇
  2019年   4篇
  2018年   9篇
  2017年   9篇
  2016年   11篇
  2015年   19篇
  2014年   19篇
  2013年   27篇
  2012年   26篇
  2011年   25篇
  2010年   18篇
  2009年   21篇
  2008年   31篇
  2007年   29篇
  2006年   18篇
  2005年   20篇
  2004年   20篇
  2003年   16篇
  2002年   25篇
  2001年   20篇
  2000年   21篇
  1999年   31篇
  1998年   91篇
  1997年   46篇
  1996年   34篇
  1995年   32篇
  1994年   29篇
  1993年   15篇
  1992年   9篇
  1991年   8篇
  1990年   5篇
  1989年   7篇
  1988年   9篇
  1987年   4篇
  1986年   3篇
  1985年   8篇
  1984年   4篇
  1983年   3篇
  1982年   7篇
  1981年   4篇
  1979年   3篇
  1978年   9篇
  1977年   12篇
  1976年   10篇
  1972年   1篇
  1969年   3篇
  1967年   2篇
  1966年   1篇
排序方式: 共有802条查询结果,搜索用时 15 毫秒
91.
The present study was undertaken after the detection of one case of cutaneous leishmaniasis with presumed infection in one of the three remaining wooded areas in the urban area of the city of Maringá, Southern Brazil; also in view of the lack of knowledge about sand flies and their behavior. From June to September, 1995, sand flies were caught with Falc?o traps during the night in the remaining wooded areas (Parque do Ingá, Bosque Dois and Horto Florestal). A total of 2,907 sand flies were caught in Parque do Ingá; 1,723 of them were aught in forest traps and 1,184 in wild animal shelter traps at the zoo. The results show that Lutzomyia whitmani is better adapted to the three areas under study and that it frequently occurs in wild animal shelters within the urban perimeter of Maringá.  相似文献   
92.
In alloxan-induced diabetic rats (Wistar, females, age 3-4 months of postnatal life) the large spectrum of fatty acids in blood serum, brain cortex, medulla oblongata and liver was studied. The fatty acids, using gas chromatography, were detected as methyl esters and the methods were published previously (Smídová and al. 1994). Alloxan (Merck) administered i.p., 140 mg/kg body weight, caused immediately elevation (three times) of blood sugar levels. On the 13th day the rats were killed. The results are as follows: a) In blood serum alloxan diabetes of cca two weeks duration caused a significantly increased participation of saturated FA and decreased participation of both polyunsaturated FA (n-3 and n-6). b) In brain cortex no differences between controls and diabetic rats in the indicated groups of FA were found. c) In the medulla oblongata an increased participation of polyunsaturated fatty acids n-6 was established. d) In hepatic tissue the increased participation of saturated FA as well as a decreased participation of FA n-6 was described. Analysing the main groups of FA we found especially in n-3 and n-6 FA several significant changes in single FA (a smaller pool of arachidonic acid in blood serum as well as in liver, decreased participation of docosahexaenoic acid in the brain cortex, etc.). The purpose and possible consequences of such changes are discussed.  相似文献   
93.
In this study, we examined the ability of tumour necrosis factor-alpha (TNF) to stimulate the mitogen-activated protein (MAP) kinase homologues p42/44 MAP kinase, c-Jun NH2-terminal kinase (JNK) and p38 MAP kinase and its effect upon DNA synthesis in primary cultures of bovine aortic endothelial cells (BAECs). TNF strongly stimulated p38 MAP kinase and JNK activity in both a time- and concentration-dependent manner. By contrast, TNF was a very poor activator of p42/44 MAP kinase relative to the known activator of p42/44 MAP kinase in endothelial cells, adenosine triphosphate (ATP). TNF-stimulated activation of p38 MAP kinase, and MAPKAP kinase-2, a known downstream target of p38 MAP kinase, was strongly inhibited by pre-incubation with the p38 MAP kinase inhibitor SB203580, whereas the minor activation of p42/44 MAP kinase was abolished by pre-incubation of the cell with the novel MAP kinase kinase 1 inhibitor PD098059. Addition of TNF resulted in a 50-60% decrease in DNA synthesis in BAECs. Pre-incubation with PD098059 or co-incubation with ATP failed to modify the inhibitory effect of TNF upon DNA synthesis. SB203580 reduced basal DNA synthesis by approximately 50%; however, if failed to modify the inhibition mediated by TNF. These results indicate that TNF strongly activates both p38 MAP kinase, JNK and, to a minor extent, p42/p44 MAP kinase. It is likely that only one of these kinases, JNK, plays a role in the regulation of DNA synthesis in these cells.  相似文献   
94.
BACKGROUND/AIMS: Vasopressin has been reported to reduce bile flow, but its effects on bile acid secretion and bile acid-related hepatotoxicity are still unclear. We therefore investigated the influence of vasopressin on the hepatotoxicity and biliary excretion of taurochenodeoxycholic acid in primary cultured rat hepatocytes and isolated perfused rat liver models. METHODS/RESULTS: 1) Addition of vasopressin to hepatocyte cultures significantly decreased lactate dehydrogenase release as compared to cultures exposed to 1 mM taurochenodeoxycholic acid alone, and also reduced intracellular taurochenodeoxycholic acid content from 19.3 +/- 2.2 to 13.0 +/- 1.6 nmol/mg protein. After 30 min of preincubation with 1 mM taurochenodeoxycholic acid, rinsing and reculture of hepatocytes in bile acid-free medium resulted in gradual decrease in the intracellular level of the bile acid, and addition of vasopressin (10(-9) M) to the reculture medium accelerated this process. 2) Superimposition of vasopressin (330 pmol/l) for 10 min on taurochenodeoxycholic acid infusion (1.0 mumol/min: 25 mumol/l) caused a rapid increase in bile flow and biliary excretion of taurochenodeoxycholic acid (697 +/- 42 vs 584 +/- 27 nmol/10 min per g liver) from perfused rat livers, and significantly reduced lactate dehydrogenase release. 3) Superimposition of the PKC blocker H-7 (5 mumol/l) on taurochenodeoxycholic acid infusion (1.0 mumol/min: 25 mumol/l) caused a gradual increase in bile flow and biliary excretion of taurochenodeoxycholic acid. Furthermore, an additional infusion of vasopressin (100 pmol/l) for 10 min in the presence of H-7 produced a greater increase in bile flow and biliary excretion of taurochenodeoxycholic acid as compared with H-7 alone (754 +/- 71 vs. 657 +/- 26 nmol/g liver). 4) Continuous infusion of vasopressin (330 pmol/l) significantly increased the late peak (10-50 min) of horseradish peroxidase excretion from perfused livers (from 8.48 +/- 1.02 to 21.7 +/- 6.02 ng/g liver). CONCLUSIONS: These findings suggest that vasopressin exerts a protective effect against taurochenodeoxycholic acid-induced hepatotoxicity by stimulating the secretion of this bile acid via intracellular vesicular transport systems.  相似文献   
95.
We evaluated portal and peripheral blood immunoreactive insulin concentrations (IRI) after glucose infusion in patients undergoing gastrectomy. Seventy-four patients were divided into following two groups: 68 received 25g glucose infusion in an hour (glucose group), and the remainder received no glucose (control group). Portal blood IRI level in glucose group was about thirty-fold higher than that in control group. However, peripheral blood IRI did not correlate with portal blood IRI in glucose group. In addition, significant negative correlation between portal blood IRI and blood glucose was observed in glucose group. Our results reveal that adequate pancreatic insulin secretion occurs after glucose infusion during gastrectomy, but peripheral blood IRI does not reflect this pancreatic insulin secretion. The results also suggest that blood glucose may be regulated by the liver under these conditions.  相似文献   
96.
97.
1简介 当前,从成膜方法来讲,ILD loW-k材料大致上分为两类:一类是以SiCOH为代表的CVD(化学气相淀积)膜,另一类是SOD(旋转涂层)膜,它包括有机的、无机的和SiCOH.  相似文献   
98.
Breeding studies are reported of a previously undescribed hereditary retinal degeneration identified in the Siberian Husky breed of dog. This disorder clinically resembles the previously reported autosomal recessive canine hereditary retinal degenerations collectively termed progressive retinal atrophy (PRA). However, the pedigree of the propositus, a male Siberian Husky, exhibited an X-linked pattern of transmission. This dog was outcrossed to three phenotypically normal female laboratory Beagles and two of their F1 daughters were bred to a phenotypically normal male Beagle, producing affected males in the F2 generation. Subsequent inbreedings produced further affected males and affected females as well. X-linked transmission was established by exclusion of alternative modes of inheritance and, consequently, the disease has been termed X-linked progressive retinal atrophy (XLPRA). This is the first reported X-linked retinal degeneration in an animal. Because of the many similarities of PRA in dogs to retinitis pigmentosa (RP) in humans, this new disease may not only represent the first animal model of X-linked RP (XLRP) but may well be a true homolog of one of the XLRP loci (RP2, RP3, RP6). It is the first retinal degeneration in dogs that can be assigned to an identified canine chromosome, and the first for which linkage mapping offers a realistic approach to proceed by positional cloning towards identifying the responsible gene locus.  相似文献   
99.
100.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号