全文获取类型
收费全文 | 2632篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 20篇 |
金属工艺 | 4篇 |
机械仪表 | 6篇 |
矿业工程 | 4篇 |
能源动力 | 1篇 |
轻工业 | 7篇 |
无线电 | 23篇 |
一般工业技术 | 25篇 |
冶金工业 | 2483篇 |
原子能技术 | 1篇 |
自动化技术 | 60篇 |
出版年
2017年 | 2篇 |
2016年 | 2篇 |
2013年 | 6篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 86篇 |
1998年 | 735篇 |
1997年 | 470篇 |
1996年 | 284篇 |
1995年 | 155篇 |
1994年 | 140篇 |
1993年 | 157篇 |
1992年 | 16篇 |
1991年 | 26篇 |
1990年 | 28篇 |
1989年 | 28篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 22篇 |
1985年 | 19篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 28篇 |
1979年 | 5篇 |
1978年 | 13篇 |
1977年 | 68篇 |
1976年 | 163篇 |
1975年 | 12篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1967年 | 2篇 |
1963年 | 1篇 |
1957年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有2635条查询结果,搜索用时 15 毫秒
91.
JM Gimble GM Pighetti MR Lerner X Wu SA Lightfoot DJ Brackett K Darcy AB Hollingsworth 《Canadian Metallurgical Quarterly》1998,253(3):813-817
PURPOSE: To evaluate the usefulness of Doppler ultrasonography (US) in the diagnosis of hyperfiltration in patients with insulin-dependent diabetes mellitus (IDDM). MATERIALS AND METHODS: Eighty-one consecutive patients with IDDM were studied. All patients were normotensive and had normal creatinine and blood urea nitrogen levels. The glomerular filtration rate (GFR) was evaluated by means of plasma clearance of chromium-51 ethylenediaminetetraacetic acid, urinary albumin excretion, US evaluation of renal volume, and Doppler evaluation of resistance index (RI) in the renal interlobar arteries. The patients were divided according to GFR into the following groups: those with hyperfiltering kidneys (group 1, n = 40) and those with normofiltering kidneys (group 2, n = 41). RESULTS: The median renal volume was 351 mL (95% CI = 337 mL, 379 mL) in group 1 and 318 mL (95% CI = 300 mL, 335 mL) in group 2 (P = .005). The number of patients with microalbuminuria was significantly lower in group 1 than in group 2 (P = .02). The median RI was significantly lower in group 1 (0.55; 95% CI = 0.53, 0.57) than in group 2 (0.57; 95% CI = 0.56, 0.59) (P = .04). An RI of less than 0.5, a renal volume greater than 410 mL/m2, and the absence of microalbuminuria were independent predictors of hyperfiltration. An RI of less than 0.5 and a renal volume greater than 410 mL/m2 showed high specificity (98% and 95%, respectively) and poor sensitivity (25% and 23%, respectively) in the diagnosis of hyperfiltration in IDDM patients. CONCLUSION: Both RI and renal volume showed correlation with GFR, but neither parameter is sufficiently sensitive in screening for hyperfiltration in IDDM patients. 相似文献
92.
Prevention of T cell anergy by signaling through the gamma c chain of the IL-2 receptor 总被引:1,自引:0,他引:1
VA Boussiotis DL Barber T Nakarai GJ Freeman JG Gribben GM Bernstein AD D'Andrea J Ritz LM Nadler 《Canadian Metallurgical Quarterly》1994,266(5187):1039-1042
When stimulated through their antigen receptor without requisite costimulation, T cells enter a state of antigen-specific unresponsiveness termed anergy. In this study, signaling through the common gamma chain of the interleukin-2 (IL-2), IL-4, and IL-7 receptors in the presence of antigen was found to be sufficient to prevent the induction of anergy. After culture with IL-2, IL-4, or IL-7, Jak3 kinase was tyrosine-phosphorylated, which correlated with the prevention of anergy. Therefore, a signal through the common gamma chain may regulate the decision of T cells to either clonally expand or enter a state of anergy. 相似文献
93.
94.
95.
SA Jones S Horiuchi D Novick N Yamamoto GM Fuller 《Canadian Metallurgical Quarterly》1998,28(11):3514-3522
The soluble IL-6 receptor (sIL-6R) is generated through either proteolytic shedding of the cognate receptor (PC-sIL-6R), or released as the product of differential mRNA splicing (DS-sIL-6R). Using monocytic THP-1 cells, we demonstrate that both mechanisms are independently regulated, and that each process contributes to sIL-6R production. Shedding of the IL-6R was activated by the Ca2+ ionophore, ionomycin, and inhibited by the TNF-alpha protease inhibitor (TAPI). In contrast, basal sIL-6R release was unaffected by Ca2+ depletion and largely insensitive to TAPI. Moreover, although IL-6R shedding was inactivated by serum starvation, non-stimulated production remained intact. Basal sIL-6R production via differential mRNA splicing was shown through the inhibitory action of brefeldin A and an enzyme-linked immunosorbent assay specific for DS-sIL-6R. Release of this isoform was unaffected by ionomycin or TAPI, indicating that Ca2+ mobilization activates PC-sIL-6R generation, but not DS-sIL-6R. The divergent control of these sIL-6R isoforms indicates that they may independently influence the inflammatory response. 相似文献
96.
Chard (Beta vulgaris L. var. cicla) is one of the plants used as hypoglycaemic agent by diabetics in Turkey and it has been reported to reduce blood glucose. The purpose of this study was to investigate the effect of feeding chard on diabetes induced impairments in rat skins. Uncontrolled induced diabetes caused significant increases in nonenzymatic glycosylation of skin proteins, lipid peroxidation and blood glucose. Administration of chard extract inhibited these effects except the increase in lipid peroxidation. SDS-polyacrylamide gel electrophoresis revealed no significant differences in any protein bands between any of the groups. The data indicate that the use of chard may be effective in preventing or at least retarding the development of some diabetic complications. 相似文献
97.
CTLs from patients with Chediak-Higashi syndrome (CHS) are unable to destroy target cells recognized via the TCR. To determine the mechanism responsible for the loss of cytotoxicity, CD8+ CTL clones have been derived from a patient with CHS. Individual CTL clones show poor killing that can be increased in longer assays. However, in the presence of cycloheximide, the small amount of killing observed is abolished, indicating killing arises from newly synthesized proteins, rather than from proteins stored in granules. In this study, we show that the CHS CTL clones express normal levels of the lytic proteins granzyme A, granzyme B, and perforin, which are processed properly during biosynthesis and targeted correctly to giant lytic granules. Despite the difference in size, CHS and normal lytic granules are similar, in that both contain the lysosomal enzyme cathepsin D and the lytic protein granzyme A, and lack the mannose-6-phosphate receptor (MPR). However, unlike normal CTL clones, the CHS CTL clones are unable to secrete their giant granules in which the lytic proteins are stored. After cross-linking the TCR, CHS CTL clones fail to secrete granzyme A, as assayed by both enzyme release and confocal microscopy. We suggest that the defect in CHS lies in a protein that is involved in membrane fusion and is essential for the secretion of lysosomal compartments in certain hemopoietic cells. 相似文献
98.
The first isolated case of agenesis of the mastoid antrum, previously only described in association with the congenital syndromes trisomy 13 and mandibulofacial dysostosis, is reported. The loss of this important surgical landmark may result in disorientation and iatrogenic trauma. The surgeon must be aware of its existence, and where it is suspected the middle fossa dura should be exposed and followed posteriorly until the lateral sinus is encountered. 相似文献
99.
A transient increase in brain polyamine metabolism, termed the polyamine-stress-response is a common response to stressful stimuli. Previous studies have implicated an over-reactive polyamine response as a component of the maladaptive brain response to stressful events, and as a novel molecular mechanism involved in the pathophysiology of affective disorders. Ample evidence indicates that stressful experiences during early life can alter normal developmental processes and may result in pathophysiological and behavioral changes in the adult. Additionally, an important characteristic of affective disorders is their age dependency, a phenomenon that may be correlated with a maladaptive regulation of the hypothalamic-pituitary-adrenocortical (HPA) neuroendocrine system. In the present study we measured the activities of the enzymes ornithine decarboxylase and S-adenosylmethionine decarboxylase as markers of polyamine synthesis and found that unlike adults, immature rats do not show the characteristic brain polyamine-stress-response. Instead of the characteristic increase observed in adults, ornithine decarboxylase activity in immature animals was reduced or remained unchanged (for up to 16 days of age) after a dexamethasone injection or restraint stress application. The ontogenesis of this ornithine decarboxylase response was brain region-specific, indicating its dependence on the stage of neuronal maturation. Animals treated with dexamethasone at 7 days of age, showed increased behavioral reactivity in the open-field test as adults and an attenuated increase in ornithine decarboxylase activity after a re-challenge with dexamethasone at age 60 days. The results indicate that: (1) the brain polyamine-stress-response is developmentally regulated and its ontogenesis is brain region-specific, indicating dependence on the stage of neuronal maturation; (2) the switch to a mature polyamine-stress-response pattern coincides with the cessation of the stress hyporesponsive period in the HPA system: (3) activation of the polyamine-stress-response, as in the mature brain, appears to be a constructive reaction, while its down-regulation, as in the developing brain, may be implicated in neuronal cell death; (4) an attenuated dexamethasone-induced increase in ornithine decarboxylase activity implicates an altered polyamine-stress-response in the maladaptive response of the brain to stressful events. 相似文献
100.
N van Wieringen AN Kotte GM van Leeuwen JJ Lagendijk JD van Dijk GJ Nieuwenhuys 《Canadian Metallurgical Quarterly》1998,43(1):121-138
There is evidence of a two-way interaction between gastric acid secretion and H. pylori-associated gastritis. Gastric acid secretion influences the density of H. pylori colonisation, its distribution within the stomach and the severity of the mucosal inflammatory response to the infection. In addition, H. pylori gastritis alters gastric acid secretion. In subjects with a predominant antral gastritis, it increases acid secretion predisposing to duodenal ulcer, whereas in others with predominant body gastritis, acid secretion is impaired and the subjects have an increased risk of gastric cancer. The two-way interaction between acid secretion and H. pylori gastritis is observed when H. pylori-positive subjects are treated with proton pump inhibitor agents. The inhibition of acid secretion induces a body gastritis and this inflammation of the body mucosa inhibits acid secretion thus augmenting the anti-secretory effect of the drug. In this article, we discuss the interaction between gastric acid secretion and H. pylori gastritis and its importance in determining disease outcome. 相似文献