全文获取类型
收费全文 | 2203篇 |
免费 | 12篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 104篇 |
金属工艺 | 16篇 |
机械仪表 | 26篇 |
建筑科学 | 20篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 47篇 |
水利工程 | 2篇 |
无线电 | 75篇 |
一般工业技术 | 186篇 |
冶金工业 | 1662篇 |
原子能技术 | 1篇 |
自动化技术 | 57篇 |
出版年
2019年 | 4篇 |
2018年 | 5篇 |
2016年 | 4篇 |
2014年 | 5篇 |
2013年 | 21篇 |
2012年 | 22篇 |
2011年 | 21篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 28篇 |
2007年 | 20篇 |
2006年 | 23篇 |
2005年 | 16篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 9篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 64篇 |
1998年 | 523篇 |
1997年 | 278篇 |
1996年 | 196篇 |
1995年 | 133篇 |
1994年 | 97篇 |
1993年 | 109篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 33篇 |
1989年 | 38篇 |
1988年 | 38篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 21篇 |
1984年 | 4篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 29篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 65篇 |
1976年 | 97篇 |
1975年 | 11篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1968年 | 4篇 |
1966年 | 3篇 |
1890年 | 4篇 |
排序方式: 共有2215条查询结果,搜索用时 10 毫秒
1.
Mobile devices are vulnerable to theft and loss due to their small size and the characteristics of their common usage environment. Since they allow users to work while away from their desk, they are most useful in public locations and while traveling. Unfortunately, this is also where they are most at risk. Existing schemes for securing data either do not protect the device after it is stolen or require bothersome reauthentication. Transient Authentication lifts the burden of authentication from the user by use of a wearable token that constantly attests to the user's presence. When the user departs, the token and device lose contact and the device secures itself. We show how to leverage this authentication framework to secure all the memory and storage locations on a device into which secrets may creep. Our evaluation shows this is done without inconveniencing the user, while imposing a minimal performance overhead 相似文献
2.
AG Niessen JG Bollemeijer RJ de Keizer PH de Meijer 《Canadian Metallurgical Quarterly》1994,138(15):770-775
OBJECTIVE: To assess how often the aetiology is established in patients with uveitis, what systemic disease are found and what is the contribution of the internist to the diagnostic process. DESIGN: Retrospective study. SETTING: University Hospital Leiden, the Netherlands. METHOD: From January 1987 to April 1992, 342 patients presented with uveitis. All patients underwent a standard ophthalmological examination. Referral to an internist and individualised laboratory screening followed in patients with recurrent, chronic, bilateral or panuveitis. Recorded were: ophthalmological data, results of laboratory screening, results of analysis by the internist, final diagnosis and presence of systemic disease. RESULTS: 149 (44%) patients were examined by the internist, 18 (5.2%) were seen by another specialist. In 169 (49%) patients a specific diagnosis was made. 74 (22%) had a systemic disease, 74 a primary ocular disease. In 28 (8%) a systemic disease was presumed (5% were HLA-B27 positive, 3% had abnormal laboratory results); 5 (1%) patients had endophthalmitis as a complication of a septic process. CONCLUSION: In approximately 1/3 of the patients with uveitis a systemic disease was found. Examination by the internist tailored to the individual patient is essential in the evaluation of uveitis patients. 相似文献
3.
MD Goldberg JR Canvin P Freestone C Andersen D Laoudj PH Williams IB Holland V Norris 《Canadian Metallurgical Quarterly》1997,79(6):315-322
In the bacterium Escherichia coli, H-NS-(H1, H1a) is a heat-stable protein with a molecular mass of 15.5 kDa involved in nucleoid organisation and gene regulation linked to certain signal transduction pathways. We have shown that, following addition of preparations of everted inner membrane vesicles, heat-stable cleavage products of approximately 10 kDa of H-NS are formed in vitro from newly synthesised, radio-labelled H-NS and from purified H-NS. The 15.5 kDa protein and its cleavage products were also recovered from a minicell system. These results raised the possibility that cleavage of H-NS is physiologically significant. However, the cleavage of H-NS observed appears to occur during cell breakage and to depend on the method of protein extraction and the presence of the outer membrane protease, OmpT. Nevertheless, the results indicate that H-NS may contain at least two separate domains with cleavage occurring between these domains at a preferred OmpT site. Failure to take account of H-NS cleavage in sample preparation and analysis can lead to serious underestimation of H-NS levels. 相似文献
4.
5.
Wilhelm Conrad Roentgen's discovery of the X-ray one century ago has been ranked in importance with the discovery and development of anesthesia and the discovery of microorganisms and their role in disease. Roentgen's scientific devotion and the persistence of C. Edmund Kells, who took Roentgen's discovery and applied it to dentistry, had a great impact on how dentists practice today. 相似文献
6.
PB Imrey LA Jackson PH Ludwinski AC England GA Fella BC Fox LB Isdale MW Reeves JD Wenger 《Canadian Metallurgical Quarterly》1996,143(6):624-630
Between February 1991 and April 1992, eight undergraduates at a US residential university and one at a nearby 2-year college contracted serogroup C meningococcal disease. A case-control investigation with 20 controls per case, oropharyngeal carriage surveys, and multilocus enzyme electrophoresis (MEE) of serogroup C isolates were used to identify factors contributing to the outbreak. All eight sterile-site isolates from cases were closely related by MEE and were similar (though not identical) to the strain associated with the 1991-1992 epidemic of meningococcal disease in eastern Canada. Disease was associated with cigarette smoking (p = 0.012), recent patronage of campus-area bars (p = 0.034), estimated amount of time spent in campus-area bars (p = 0.0003), and, especially, recent patronage of one specific bar, bar A (p = 0.0006; odds ratio = 23.1, 95% confidence interval 3.0-571.5). In carriage surveys, 1,528 throat cultures taken from (primarily student) noncases yielded only five (0.3%) strains that were identical by MEE to those from cases. Two of these were found among 22 cultures obtained from bar A employees in spring 1992. Some cases in this outbreak may have followed transmission of the epidemic strain in bar A. Campus bar environments may facilitate the spread of meningococcal disease among teenagers and young adults. 相似文献
7.
Vladimir Kulyukin Chaitanya Gharpure John Nicholson Grayson Osborne 《Autonomous Robots》2006,21(1):29-41
We present a robot-assisted wayfinding system for the visually impaired in structured indoor environments. The system consists
of a mobile robotic guide and small passive RFID sensors embedded in the environment. The system is intended for use in indoor
environments, such as office buildings, supermarkets and airports. We describe how the system was deployed in two indoor environments
and evaluated by visually impaired participants in a series of pilot experiments. We analyze the system’s successes and failures
and outline our plans for future research and development. 相似文献
8.
9.
FY Ghauri JK Nicholson BC Sweatman J Wood CR Beddell JC Lindon NJ Cairns 《Canadian Metallurgical Quarterly》1993,6(2):163-167
Mutations of ras oncogenes in 37 human stomach cancers and 13 adenomas were investigated with regard to the histological phenotypes using polymerase chain reaction (PCR), allele-specific oligonucleotide hybridization and/or direct sequencing of the PCR products. The ras mutation was found only in one case (2.7%), the histology of which was poorly differentiated adenocarcinoma. We found no mutation in stomach adenomas. The mutation consisted of a guanine-to-adenine transition in the first base of codon 13 of c-Ki-ras which replaced wild-type glycine with serine, indicating that a putative glycine-to-aspartic acid change is not necessarily the critical event for c-Ki-ras gene activation in codon 13. These results further confirm the infrequency of ras mutation in stomach tumors and also suggest that ras mutations are not specific to the differentiated type of stomach cancer. 相似文献
10.
G. Meaden P. G. Partridge M. N. R. Ashfold E. D. Nicholson A. Wisbey 《Journal of Materials Science》1996,31(11):2801-2805
Continuous chemical vapour-deposited diamond-coated fibres with tungsten wire or SiC fibre cores are attractive for reinforcing metals and ceramics. The fibres have been embedded in Ti-6A1-4V alloy to produce a diamond fibre-reinforced composite. Both the fibres and the composite material are extremely difficult to cut without damage by conventional mechanical methods. The use of a Nd-YAG laser to cut these materials is described. 相似文献