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中国航天科技集团公司中国空间究院所属北京卫星制造厂热处理与表面处理工程中心成功攻克光亮镀银技术,在功能镀覆层制备技术领域取得了新的突破。  相似文献   
3.
OBJECTIVE: To determine whether antibiotic and bronchodilator treatment of acute bronchitis in patients without lung disease is efficacious. DESIGN: A MEDLINE search of the literature from 1966 to 1995 was done, using "Bronchitis" as the key word. Papers addressing acute bronchitis in adults were used as well as several citations emphasizing pediatric infections. A manual search of papers addressing the microorganisms causing acute bronchitis was also done. Data were extracted manually from relevant publications. SETTING: All published reports were reviewed. Papers dealing with exacerbations of chronic bronchitis were excluded in this review. RESULTS: Although acute bronchitis has multiple causes, the large majority of cases are of viral etiology. Mycoplasma pneumoniae, Chlamydia pneumoniae, and Bordetella pertussis are the only bacteria identified as contributing to the cause of acute bronchitis in otherwise healthy adults. Nine double-blind, placebo-controlled trials were reviewed. Four studies showed no advantage for doxycycline and one study showed no advantage for erythromycin. One study using erythromycin and one study using trimethoprim and sulfamethoxazole showed that these antibiotics were slightly better than placebo. Two other studies showed an impressive superiority for liquid or inhaled albuterol when compared with erythromycin. CONCLUSIONS: Most studies showed no significant difference between drug and placebo, and the two studies that did showed only small clinical differences. Albuterol had an impressive advantage over erythromycin. Antibiotics should not be used in the treatment of acute bronchitis in healthy persons unless convincing evidence of a bacterial infection is present.  相似文献   
4.
Sparse-graph codes for quantum error correction   总被引:8,自引:0,他引:8  
Sparse-graph codes appropriate for use in quantum error-correction are presented. Quantum error-correcting codes based on sparse graphs are of interest for three reasons. First, the best codes currently known for classical channels are based on sparse graphs. Second, sparse-graph codes keep the number of quantum interactions associated with the quantum error-correction process small: a constant number per quantum bit, independent of the block length. Third, sparse-graph codes often offer great flexibility with respect to block length and rate. We believe some of the codes we present are unsurpassed by previously published quantum error-correcting codes.  相似文献   
5.
The vagus     
The surgical physiology of the vagus is reviewed with respect to vagotomy in the treatment of duodenal ulcer. All types of vagotomy (truncal, selective gastric, or proximal gastric) produce similar reduction in acid secretion and comparable elevation in serum gastrin. The evidence is mounting that the vagus may have opposing influences on gastrin release: stimulation and inhibition. Division of only the extragastric vagal branches leads to withdrawal of an inhibitory mechanism rendering the denervated stomach more sensitive to the action of gastrin. The loss of this vagally controlled inhibitory mechanism, rather than more meticulous dissection, may explain the higher incidence of more complete vagotomies in selective than in truncal vagotomy. Proximal gastric vagotomy may be the ideal elective operation yet devised for duodenal ulcer. It does, however, cause elevation in serum gastrin and more than 90 per cent of patients after this operation will have positive insulin test in two to four years. This is higher than the positivity seen with truncal vagotomy. Results of controlled trials are needed before this operation becomes fully established.  相似文献   
6.
Transport of 2-deoxy-D-galactose in Saccharomyces fragilis   总被引:2,自引:0,他引:2  
2-Deoxy-D-galactose (dGal) transport in Saccharomyces fragilis is characterized by energy requirement and accumulation of the free sugar against a concentration gradient, indicating active transport. Besides free sugar dGal-1-phosphate, UDP-dGal and a trehalose-like derivative were found inside the cells. The accumulation of the phosphorylated derivatives was balanced by a concomitant decrease of ATP, orthophosphate and polyphosphates. With pulse labeling experiments it could be shown that the free sugar is transported into the cells. This conclusion was supported by several other experimental results, e.g. the lack of correlation between the sugar transport parameters and the dGal phosphorylation capacity, and the countertransport of free dGal evoked by galactose in the medium. The typical differences between this active transport mechanism and the transport-associated phosphorylation system, described previously, are discussed.  相似文献   
7.
The pyrolysis under nitrogen of salt free and salt treated cellulose was studied by infrared spectroscopy. The results confirm the unzipping mechanism suggested by DTA and TGA studies, and show this mechanism to apply to the untreated and salt treated samples. The results also show the unzipping to stop at the stage of char formation. The onset of this stage was found to occur after the volatilization of only 45–50% of the initial sample of the borax treated cellulose, compared with 65–70% of the KCl treated cellulose and 80–85% of the untreated cellulose.  相似文献   
8.
    
Vinyl chloride (VC) workers are known to be at risk for development of liver angiosarcoma, a rare tumor. Previously, more than 80% of VC workers with liver angiosarcoma have been found to have an Asp-13 c-Ki-ras oncogene mutation, and more than 50% of VC-exposed workers without liver tumors were found to have Asp13-Ki-ras oncoprotein in their plasma. Some workers in Taiwan had also been exposed to VC, and some have contracted liver tumors. In this study, we used enhanced chemiluminescence Western blotting to detect Asp13-p21-Ki-ras in the sera of VC-exposed workers in Taiwan. There were 14 of 113 (12.4%) VC workers positive for the Asp13-Ki-ras oncoprotein in plasma, but 0 of 18 controls were positive. There were 10 of 69 (14.5%) plasma-positives among the more highly exposed (> 1000 ppm-months) workers and 4 of 48 (9.1%) plasma-positives among the lesser exposed (< or = 1000 ppm-months). Compared with the unexposed controls, the odds ratios (and 95% confidence intervals [CI]) for plasma-positivity were 4.11 (95% CI = 0.21, 80.4) in the lower-exposed workers and 6.53 (95% CI = 0.37, 116.9) in the higher-exposed workers, and there was a linear trend between exposure and plasma-positivity (P = 0.073). After adjusting for age and drinking status, the odds ratios (and 95% CIs) were 1.64 (95% CI = 0.17, 15.8), and 2.65 (95% CI = 0.42, 16.8), respectively, and there was a significant linear trend between exposure and plasma-positivity (P = 0.048). In summary, Asp13-Ki-ras oncoprotein can be found in the plasma of VC workers in Taiwan, and a significant dose-response relationship exists between plasma oncoprotein expression and VC exposure.  相似文献   
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New low-density single-crystal (IDS) alloys have been developed for turbine blade applications, which have the potential for significant improvements in the thrust-to-weight ratio over current production superalloys. An innovative alloying strategy was used to achieve alloy density reductions, high-temperature creep resistance, micro-structural stability, and cyclic oxidation resistance. The alloy design relies on molybdenum as a potent, lower-density solid-solution strengthener in the nickel-based superalloy. Low alloy density was also achieved with modest rhenium levels and the absence of tungsten. Microstructural, physical, mechanical, and environmental testing demonstrated the feasibility of this new IDS superalloy design.  相似文献   
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