全文获取类型
收费全文 | 2474篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 2篇 |
化学工业 | 94篇 |
金属工艺 | 15篇 |
机械仪表 | 11篇 |
建筑科学 | 26篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 107篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 85篇 |
一般工业技术 | 145篇 |
冶金工业 | 1814篇 |
原子能技术 | 20篇 |
自动化技术 | 137篇 |
出版年
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 17篇 |
2013年 | 49篇 |
2012年 | 29篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 28篇 |
2008年 | 26篇 |
2007年 | 44篇 |
2006年 | 33篇 |
2005年 | 22篇 |
2004年 | 27篇 |
2003年 | 36篇 |
2002年 | 27篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 54篇 |
1998年 | 583篇 |
1997年 | 334篇 |
1996年 | 211篇 |
1995年 | 130篇 |
1994年 | 92篇 |
1993年 | 122篇 |
1992年 | 30篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 22篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 20篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 52篇 |
1976年 | 93篇 |
1974年 | 7篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1969年 | 5篇 |
排序方式: 共有2491条查询结果,搜索用时 15 毫秒
41.
42.
Several factors promote the progression of renal disease, including glomerular hypertension and hypertrophy, molecular factors such as cytokines and growth hormones, proteinuria, acidosis, and hyperlipidemia. Regardless of the underlying etiology, many patients with chronic renal insufficiency will ultimately require kidney replacement therapy. Your goal is to delay the progression of renal failure, mainly through aggressive control of blood pressure. Other possible interventions include protein restriction, bicarbonate therapy, and lipid-lowering drugs. 相似文献
43.
44.
KL Margolis N Lurie PG McGovern M Tyrrell JS Slater 《Canadian Metallurgical Quarterly》1998,13(8):515-521
Active cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS) was treated with an intraocular sustained-release ganciclovir implant. A total number of 19 implants were performed in 15 eyes of 9 AIDS patients. The intraocular sustained-release ganciclovir was effective in preventing reactivation of CMV retinitis in 15 of the 19 implants, ineffective in 3, and undetermined in 1. All ineffective cases had been resistant to ganciclovir therapy before the implants. Vision after the therapy was maintained at better than 0.5 except for one eye. There were no serious ocular complications caused by the therapy. Among 5 patients with unilateral CMV retinitis, 2 unaffected eyes developed CMV retinitis during this therapy. In addition, another patient developed presumed CMV infection in other systemic organs. Based on these data, the intraocular sustained-release ganciclovir implant was considered to be useful for the treatment of CMV retinitis in AIDS. 相似文献
45.
Phthalimidomethyl derivatives 1, encompassing a wide range of leaving group abilities, are rapidly hydrolysed to the corresponding phthalamic acid via rate-determining attack at the phthalimide carbonyl group. 相似文献
46.
The Kjeldahl and Dumas (combustion) methods were compared in 11 laboratories analyzing samples of milk, skim milk powder, whole milk powder, whey protein concentrate, infant formula, casein, caseinate, 2 reference compounds (glycine and EDTA), and a secondary reference skim milk powder. The comparison was conducted by using international standards where applicable. Overall means were 8.818 g N/100 g by the Kjeldahl method and 8.810 g N/100 g by the Dumas method. No evidence was found for a consistent bias between methods that may be of concern in the trading of dairy produce. A review of more than 10 related trials revealed a lack of consensus in the bias between the 2 methods, suggesting that differences in methodology and sources of systematic error may be contributors. For samples containing > 2 g N/100 g, the Dumas relative repeatability and reproducibility standard deviations were consistently about 0.35 and 0.75%, respectively, whereas the corresponding Kjeldahl values declined generally with N content and were significantly larger. The Dumas precision characteristics may be due to the dominance of Leco analyzers in this trials, and in most other recent trials, rather than an inherent method attribute. Protein determination methods for dairy products need to be reviewed and updated. The Dumas method needs Codex Alimentarius status as a recognized test method. 相似文献
47.
N Ram MV Rao L Prabhu CS Nirodi S Sultana PG Vatsala G Padmanaban 《Canadian Metallurgical Quarterly》1995,317(1):39-45
Polymeric films were deposited from hydroxyethylmethacrylate (HEMA) plasma on non-woven poly(butyleneterephtalate) (PBT) filter materials. To test the effect of deposition conditions on surface properties, film were deposited using a constant monomer flow rate and a discharge power ranging from 40-100 W. Surface composition and surface energetics were evaluated by Electron Spectroscopy for Chemical Analysis (ESCA) and contact angle measurement, respectively. Albumin (Alb) and fibrinogen (Fg) adsorption from single protein solutions to the plasma-coated filters was measured. Results illustrate the marked effects of the deposition condition on the surface composition, the surface field of forces, and the protein adsorption behavior. The latter is modeled by the application of the Good-van Oss-Chaudhury theory of Lewis acid-base contribution to interfacial energetics. Materials endowed with widely different properties are obtained from the same monomer and different deposition conditions, a result that must be taken into account both in the production step, to assure constant quality, and in the development of specifically tailored materials. 相似文献
48.
PG McNally NT Raymond ML Burden PR Burton JL Botha PG Swift AC Burden JR Hearnshaw 《Canadian Metallurgical Quarterly》1995,12(11):961-966
The relative risk of death by calendar date of diagnosis was investigated in a population-based incident cohort of 845 (463 males:382 females) IDDM diagnosed in Leicestershire before the age of 17 years between 1940 and 1989. The mortality status of 844 (99.9%) patients was determined as of the 31 December 1991, representing 14,346 person-years of risk. Trends in relative risk of death were investigated using Cox proportional hazards modelling for within cohort comparisons and age/sex and calendar time adjusted standardized mortality ratios (SMR) using generalized linear modelling for external comparisons. Median age at diagnosis was 10 years (range 3 months to 16 years); median duration of diabetes 15 years (range 1-51 years). Forty-four patients had died (5.2%; median age at death 31 years, range 11-51 years). A further four patients died at presentation (within 24 h) from ketoacidosis and are excluded from all analyses. Calendar date of diagnosis was found to be an important predictor of mortality. Adjusting for attained age there was evidence of a decline in relative risk of death with calendar date of diagnosis of 3.4% (95% CI, 0.005-6.9%) per annum, equivalent to a 32% fall per decade (95% CI, 5-51%), or 84% (95% CI, 21-97) from 1940 to 1989. The data are consistent with a large fall in mortality between the 1940s and 1950s representing over 50% of the total reduction in mortality between 1940 and 1991. Neither sex nor age at diagnosis were significant predictors of mortality. Over the study period 1940-89 the SMR (male and female combined) fell from 981 (541-1556) to 238 (60-953) relative to the general population. This population-based study shows that the prognosis for Type 1 (insulin-dependent) diabetes mellitus has improved markedly over the period 1940-1991. 相似文献
49.
The effects of the varicella-zoster virus (VZV) OKA vaccine strain in producing morphologic and antigenic changes in dissociated cultures of human fetal brain was investigated. Cultures containing 80% glial acidic fibrillary protein (GFAP), GFAP+ (positive) astrocytes and 20% GFAP- (negative) fibroblastic-like cells were infected with cell-free VZV OKA at a multiplicity of infection of 0.1 plaque-forming units per cell. Cytopathic effects and significant viral antigen labeling with antibodies against VZV gpl and immediate-early (IE) protein 62 were first detected 6 to 7 days postinfection. Several observations indicated that astrocyte GFAP expression was altered and diminished as a result of VZV infection itself, thereby raising doubts about the utility of combining cell markers and viral antigenic labeling in assessing the susceptibility of neural cell types to viral infection. The down-regulation of GFAP expression by VZV appears to be mediated by early rather than late events in the viral replication cycle and may not be the result of virally induced global shut-off of host cell protein synthesis. Similar observations were made using VZV Ellen, a multipassaged, nonvaccine strain. These observations have potential in vivo implications related to histologic analysis of VZV-infected tissues and disease pathogenesis. 相似文献
50.
It is generally agreed that naturally-occurring neuronal death in developing animals is dependent on the synthesis of proteins. Oxidative stress, as when intracellular concentrations of free radicals are raised or when cell constituents such as membrane lipids or protein thiols are oxidized, is also involved in various types of neuronal death. In the present report, we show that the number of naturally dying retinal cells in the chick embryo can be reduced by intraocular injections of cycloheximide, an inhibitor of protein synthesis. L-buthionine-[S,R]-sulfoximine, an inhibitor of glutathione synthesis, can either enhance or diminish the cell death, depending on the conditions of treatment. Moreover, when the two inhibitors are combined, L-buthionine-[S,R]-sulfoximine potentiates the neuroprotective effects of cycloheximide. Measurements of retinal glutathione concentration and protein synthesis show the specificity of the treatments: buthionine-sulfoximine diminishes glutathione concentrations but not protein synthesis whereas cycloheximide inhibits protein synthesis without decreasing glutathione concentrations. Naturally-occurring neuronal death thus seems to involve the synthesis of proteins, and is also influenced by oxidative phenomena. Our results extend previous data in tectal-lesioned embryos, and suggest that a moderate, non-lethal oxidative stress can enhance the resistance of ganglion cells that might otherwise have died (spontaneously or following axotomy) owing to insufficient retrograde trophic support. 相似文献