全文获取类型
收费全文 | 1288篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 93篇 |
金属工艺 | 17篇 |
机械仪表 | 5篇 |
建筑科学 | 17篇 |
能源动力 | 13篇 |
轻工业 | 53篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 33篇 |
一般工业技术 | 68篇 |
冶金工业 | 951篇 |
原子能技术 | 7篇 |
自动化技术 | 47篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 19篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 6篇 |
2014年 | 14篇 |
2013年 | 29篇 |
2012年 | 18篇 |
2011年 | 23篇 |
2010年 | 14篇 |
2009年 | 24篇 |
2008年 | 11篇 |
2007年 | 16篇 |
2006年 | 15篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 43篇 |
1998年 | 290篇 |
1997年 | 182篇 |
1996年 | 117篇 |
1995年 | 82篇 |
1994年 | 57篇 |
1993年 | 47篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 20篇 |
1976年 | 52篇 |
1970年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有1310条查询结果,搜索用时 15 毫秒
1.
BACKGROUND: The enterococci have become important nosocomial pathogens. They can cause multiple site infections and enterococcal bacteremia becomes more frequently associated with a high mortality rate. Previous studies of enterococcal bacteremia showed a variety of results. To establish the significance and importance of enterococci as nosocomial pathogens in this hospital, to characterize their clinical pictures and to search for the risk factors for mortality, this retrospective study was performed. METHODS: There were 208 cases of enterococcal bacteremia which occurred from 1988 to 1992. Twenty-seven cases had no medical charts, dismissing possibility of evaluation. Finally, 181 cases of enterococcal bacteremia were analysed. RESULTS: One hundred and eighteen episodes were nosocomial infections. Polymicrobial bacteremia occurred in 68.5% of the patients and the most common co-isolate was Pseudomonas aeruginosa. Those patients (78.5%) with underlying diseases and malignancies were the most common underlying problems. The portal of entry could be found in 69.6 percent of patients, with the gastrointestinal tract the most common sources. Antimicrobial susceptibility testing showed high gentamicin resistance rate (89.5%), and ampicillin still had about 80 percent sensitivity rate. The group who received specific antibiotic therapy for enterococcus showed lower mortality (36.4% versus 47.6%). Only one case had infective endocarditis. Forty-nine patients suffered from septic shock, the cause of 30 deaths. Totally 75 patients died during hospitalization. Besides sepsis, another major cause of death was their underlying diseases itself. CONCLUSIONS: Enterococci have no doubt become important nosocomial pathogens and enterococcal bacteremia were associated with high mortality, especially in elderly patients with underlying diseases such as malignancy or diabetes. When clinically dealing with sepsis from the gastrointestinal or biliary tract, especially when previous cephalosporins therapy showed no response, the possibility of enterococcal bacteremia should always be considered. 相似文献
2.
ML Martínez-Frías E Bermejo Sánchez E Rodríguez Pinilla A Villa 《Canadian Metallurgical Quarterly》1997,46(6):593-596
INTRODUCTION: Even though there are few epidemiological studies evaluating the birth weights of different groups of malformed babies with chromosomal abnormalities, it is widely known that infants with trisomy 18, and to a lesser degree those with trisomy 13 and other chromosomal alterations, have low birth weights. PATIENTS AND METHODS: In this study we present the analysis of the birth weights and gestational ages of a large sample of babies (23,155 malformed and a similar number of nonmalformed babies), separating the different groups of chromosomal anomalies and comparing the weight in the clinical groups of malformed infants. RESULTS: Most of the groups with chromosomal abnormalities present lower birth weights in comparison to the other groups. CONCLUSIONS: The results of our study support the conclusion that the relationship between chromosomal alterations and low birth weight is sufficiently important that such a low birth weight in children with minor or major anomalies should be considered as one more indication to perform chromosomal analysis. 相似文献
3.
TG Morales 《Canadian Metallurgical Quarterly》1997,15(6):346-356
Although adenocarcinoma of the stomach has decreased in incidence over the past several decades, cancer of the gastric cardia has increased rapidly over this time frame. There are several differences between adenocarcinoma of the cardia and distal stomach with respect to epidemiology, risk factors, and prognosis. In addition, recent data raise questions with regard to possible associations of cardia cancer with Barrett's esophagus, intestinal metaplasia of the cardia, and Helicobacter pylori. This article will review the current literature with regard to this important tumor and explore these potential disease associations. 相似文献
4.
We have shown that normal and human papillomavirus (HPV) type 16 immortalized human foreskin keratinocytes are growth inhibited by tumor necrosis factor alpha (TNF-alpha), whereas HPV-18- and SV40-immortalized keratinocytes are resistant to this cytokine (1). In this report, we investigated the expression of mitotic regulatory proteins, such as cyclin A, cyclin B, and p34cdc2. After exposure to TNF-alpha, normal and HPV-16-immortalized cells exhibited a dramatic decrease in the expression of these proteins. In contrast, no alteration in the levels of these proteins was observed after treatment of the resistant cell lines, as well as two HPV-positive cervical carcinoma cell lines. Expression of cyclin E does not seem to be modulated by TNF-alpha in any of the cells tested. On the other hand, cyclin D1, expression is slightly increased in normal keratinocytes and in the HPV-16-immortalized cells, whereas no alteration was observed in the HPV-18-transfected cells. The phosphorylation state of pRb correlated with cell growth; sensitive cells, which accumulate in G0-G1, after exposure to TNF-alpha, exhibited an accumulation of hypophosphorylated pRb, whereas no effect on pRb phosphorylation was observed for HPV-18-immortalized cells. These results clearly correlate with TNF-alpha-induced growth arrest in G0-G1. 相似文献
5.
AA Bakova BD Brondz OA Fedorkina VA Gusev AI Gordienko IuS Krivoshein IuL Krivorutchenko TG Prokopenko IA Popov 《Canadian Metallurgical Quarterly》1994,39(4):187-189
The possibilities of using influenza A (Leningrad) 385/80 (H3N2) virus matrix protein-specific FITC-labeled D8 monoclonal antibodies in immunofluorescence assays were investigated. The virus antigen accumulation was detected in chorioallantoic cells of chick embryos. Exhibiting the type-specific properties, the fluorescent antibodies stain the perinuclear space, cytoplasmic membrane, and granular structures in the cytoplasm of infected cells. The haemagglutination test tires in the corresponding specimens were at least 1:16. 相似文献
6.
7.
Bez R. Cantarelli D. Moioli L. Ortolani G. Servalli G. Villa C. Dallabora M. 《Electron Device Letters, IEEE》1998,19(2):37-39
A new method to erase a standard (double-poly, stacked-gate NOR-type) flash cell is proposed. The method, still using the tunneling mechanism to extract electrons from the floating gate, is based on the concept of keeping the electric field constant during the whole erasing operation. The new method has two main advantages with respect to the conventional one: (1) it does not depend on the supply voltage variation and (2) it allows a better reliability in terms of endurance-induced stress. Results have shown that flash device performances are greatly improved in terms of stability and endurance reliability up to one million cycles 相似文献
8.
DI Timokhin AV Istomin TS Shushkova TG Voronel' IG Mikha?lov 《Canadian Metallurgical Quarterly》1997,(2):19-21
Based on generalization and analysis of instructions and guidelines for therapeutical and prophylactic diets of workers, ways of its optimization were proposed, by using bifide-containing acid dairy products as a preventive agent against possible occupational diseases caused by occupational factors. 相似文献
9.
YV Panchin YI Arshavsky TG Deliagina GN Orlovsky LB Popova AI Selverston 《Canadian Metallurgical Quarterly》1996,109(2):361-365
The locomotor activity in the marine mollusc Clione limacina has been found to be strongly excited by serotonergic mechanisms. In the present study putative serotonergic cerebropedal neurons were recorded simultaneously with pedal locomotor motoneurons and interneurons. Stimulation of serotonergic neurons produced acceleration of the locomotor rhythm and strengthening of motoneuron discharges. These effects were accompanied by depolarization of motoneurons, while depolarization of the generator interneurons was considerably lower (if it occurred at all). Effects of serotonin application on isolated locomotor and non-locomotor pedal neurons were studied. Serotonin (5 x 10(-7) to 1 x 10(-6) M) affected most pedal neurons. All locomotor neurons were excited by serotonin. This suggests that serotonergic command neurons exert direct influence on locomotor neurons. Effects of serotonin on nonlocomotor neurons were diverse, most neurons being inhibited by serotonin. Some effects of serotonin on locomotor neurons could not be reproduced by neuron depolarization. This suggests that, along with depolarization, serotonin modulates voltage-sensitive membrane properties of the neurons. As a result, serotonin promotes the endogenous rhythmical activity in neurons of the C. limacina locomotor central pattern generator. 相似文献
10.