全文获取类型
收费全文 | 871篇 |
免费 | 18篇 |
专业分类
电工技术 | 9篇 |
综合类 | 2篇 |
化学工业 | 142篇 |
金属工艺 | 10篇 |
机械仪表 | 17篇 |
建筑科学 | 35篇 |
矿业工程 | 1篇 |
能源动力 | 41篇 |
轻工业 | 60篇 |
水利工程 | 18篇 |
无线电 | 48篇 |
一般工业技术 | 68篇 |
冶金工业 | 335篇 |
原子能技术 | 17篇 |
自动化技术 | 86篇 |
出版年
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 35篇 |
2012年 | 13篇 |
2011年 | 42篇 |
2010年 | 17篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 39篇 |
2006年 | 27篇 |
2005年 | 16篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 16篇 |
2001年 | 18篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 80篇 |
1997年 | 60篇 |
1996年 | 29篇 |
1995年 | 34篇 |
1994年 | 28篇 |
1993年 | 25篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 16篇 |
1976年 | 22篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1968年 | 3篇 |
排序方式: 共有889条查询结果,搜索用时 546 毫秒
101.
HL Carmalt LJ Mann CW Kennedy JM Fletcher DJ Gillett 《Canadian Metallurgical Quarterly》1998,68(10):712-715
OBJECTIVES: To investigate whether occupational exposure to organic solvents increases the risk of dementia. METHODS: Cases of dementia were identified from the computed tomography records of eight neuroradiology centres in England and Wales, and were compared with two sets of controls investigated at the same centres. The first set of controls were patients with brain cancer and the second set were patients with other disorders that were not chronically disabling. Lifetime occupational histories were obtained through a postal questionnaire completed by the subjects or their next of kin. Associations between dementia and occupation were examined by logistic regression. RESULTS: Usable questionnaires were returned for 204 (61%) of the cases, 225 (51%) of the controls with brain cancer, and 441 (61%) of the other controls. The findings with each of the two sets of controls were similar. In comparison with all controls combined, cases had less often worked ever as a painter or printer (odds ratio (OR) 0.6, 95% confidence interval (95% CI) 0.3 to 1.2), and were less likely to have worked for > 1 year as a printer, painter, or launderer or dry cleaner (OR 0.6, 95% CI 0.3 to 1.4). CONCLUSIONS: These findings provide no support for the hypothesis that occupational exposure to solvents is a cause of dementia. An excess risk in subsets of workers with extremes of exposure cannot be discounted, but the data indicate that any influence of exposure to solvents on the overall incidence of severe dementia in the general population of England and Wales is small. 相似文献
102.
In order to improve knowledge on stormwater biofiltration systems, the Facility for Advancing Water Biofiltration (FAWB) was created at Monash University in Melbourne, Australia. One of the aims of FAWB is to improve hydraulic performance of biofilters, given that there are numerous cases of infiltration devices failing after a few years of operation. Experiments were conducted in the field to evaluate the performance of existing systems, and in the lab to understand the factors that influence hydraulic behavior over time. The field experiments show that 43% of tested systems are below nominal Australian guidelines for hydraulic conductivity. The preliminary lab results show a decrease in hydraulic conductivity during the first weeks of operation (mu=66% reduction), although most remain within acceptable limits. Influences of the size of the biofilter relative to its catchment and the importance of the type of media, on the evolution of hydraulic conductivity, are examined. 相似文献
103.
This article presents a technique that uses rotor shorting rings to start the single-phase switched reluctance (SR) machine, from any rotor position, in a specified direction. It also outlines how the shorting rings enable starting of the machine. Transient finite-element analysis is used to illustrate the torque-producing mechanism from the aligned position using the rotor-mounted shorting rings. It is also used to determine the optimal stator and rotor pole arcs and shorting ring design for a 200-W prototype machine. An SR drive system incorporating rotor shorting rings is evaluated, and experimental results show the effectiveness of the technique 相似文献
104.
D Fishwick AM Fletcher CA Pickering RM Niven EB Faragher 《Canadian Metallurgical Quarterly》1994,51(11):744-748
OBJECTIVES: To document the prevalence of work related ocular (eyeWRI) and nasal (noseWRI) irritation in workers in spinning mills of cotton and synthetic textile fibres and to relate the prevalence of symptoms to atopy, byssinotic symptoms, work history, and measured dust concentrations in the personal breathing zone and work area. METHODS: A cross sectional study of 1048 cotton workers and 404 synthetic fibre workers was performed. A respiratory questionnaire was given to 1452 workers (95% of the total available population). Atopy was judged by skin prick tests to three common allergens. Work area cotton dust sampling (WAdust) was carried out according to EH25 guidelines in nine of the 11 spinning mills included in the study. Personal breathing zone dust concentrations were assessed with the IOM sampler to derive total dust exposure (PTdust) and a concentration calculated after the removal of fly (Pless). RESULTS: 3.7% of all operatives complained of symptoms of byssinosis, 253 (17.5%) complained of eyeWRI and 165 (11%) of noseWRI. These symptoms did not relate to atopy or byssinosis, or correlate univariately with any measure of cotton dust exposure (noseWRI v WAdust r = 0.153, PTdust r = 0.118, eyeWRI v WAdust r = 0.029, PTdust r = 0.052). Both of these symptoms on logistic regression analysis were related to being of white origin (P < 0.001), female sex (P < 0.001), and younger age (P < 0.001). With regression analysis, there was a negative relation between dust concentration and prevalence of symptoms. CONCLUSION: Work related ocular and nasal irritation are the most common symptoms complained of by cotton textile workers. There was no relation between these symptoms and atopy, byssinosis, or dust concentration. It is likely that they relate to as yet unidentified agents unrelated to concentration of cotton dust. 相似文献
105.
JM Howell H Lochmüller A O''Hara S Fletcher BA Kakulas B Massie J Nalbantoglu G Karpati 《Canadian Metallurgical Quarterly》1998,9(5):629-634
The position effect of the cubitus interruptus (ci) gene occurs when this gene, which is normally located in the vicinity of the pericentric heterochromatin of chromosome 4, is transferred by chromosome rearrangements to euchromatin regions. Cytological aspects of this phenomenon were investigated. For six reciprocal translocations causing the position effect (Dubinin effect) of ci, the frequencies of the ectopic contacts of the translocated chromosome 4 homologue with pericentric heterochromatin were compared to the conjugation frequencies of this chromosome's homologues. The frequencies were significantly higher when the gene was transferred to proximal chromosome regions. This suggested that the suppression of the Dubinin effect in the case of translocations with euchromatin breaks in proximal chromosome regions is caused by the higher conjugation frequency of translocated and normal chromosome 4 homologues in proximal than in distal regions. The effect of genes modulo and Su(var)2-05, which are known as modifiers of the position effect variegation, on the conjugation frequency of chromosome 4 homologues was studied for three translocations. It was shown that modulo did not affect this frequency, whereas Su(var)205 significantly decreased it. Cytogenetic data confirmed the association of the ci position effect with damage in the somatic pairing of chromosome 4 homologues. These data indicate that pericentric heterochromatin participates in determination of the localization of chromosome regions in the interphase nucleus. 相似文献
106.
MD Rugg PC Fletcher CD Frith RS Frackowiak RJ Dolan 《Canadian Metallurgical Quarterly》1997,8(5):1283-1287
Regional brain activity associated with intentional and incidental memory retrieval was studied with PET. Previously studied and new words were presented in either an intentional or an incidental memory task. Type of task was crossed with an encoding manipulation ('deep' vs 'shallow') which varied the probability that studied items would be remembered. In both tasks, deeply encoded items were associated with greater activation in the left hippocampus than were items that had received shallow encoding, suggesting that the involvement of the hippocampus in memory retrieval is independent of whether remembering is intentional or incidental. Right prefrontal and bilateral parietal cortex were more activated during the international task than during the incidental task, irrespective of encoding condition. Thus, these regions play a more extensive role in memory retrieval when remembering is intentional. 相似文献
107.
108.
The major goal of the author's research has been to discover how readers overcome the limited capacity of working memory to discover the rich pattern of causal relationships found in even the simplest stories. The specific purpose of the series of experiments presented in this article is to discover what happens when the goals and actions are widely separated in the text, and when the actions are not associated with a coherence break. The results suggest that some readers retrieve the goal from long-term memory while others do not. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
110.