首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4492篇
  免费   32篇
  国内免费   3篇
电工技术   30篇
综合类   21篇
化学工业   508篇
金属工艺   48篇
机械仪表   52篇
建筑科学   78篇
矿业工程   1篇
能源动力   29篇
轻工业   483篇
水利工程   6篇
石油天然气   1篇
无线电   115篇
一般工业技术   368篇
冶金工业   2554篇
原子能技术   11篇
自动化技术   222篇
  2022年   22篇
  2021年   32篇
  2020年   29篇
  2019年   22篇
  2018年   20篇
  2016年   37篇
  2015年   27篇
  2014年   36篇
  2013年   52篇
  2012年   59篇
  2011年   86篇
  2010年   68篇
  2009年   65篇
  2008年   68篇
  2007年   68篇
  2006年   61篇
  2005年   75篇
  2004年   62篇
  2003年   40篇
  2002年   47篇
  2001年   35篇
  2000年   36篇
  1999年   122篇
  1998年   816篇
  1997年   509篇
  1996年   312篇
  1995年   205篇
  1994年   153篇
  1993年   195篇
  1992年   53篇
  1991年   34篇
  1990年   51篇
  1989年   36篇
  1988年   37篇
  1987年   44篇
  1986年   53篇
  1985年   51篇
  1984年   35篇
  1982年   24篇
  1981年   33篇
  1980年   44篇
  1979年   22篇
  1978年   32篇
  1977年   85篇
  1976年   143篇
  1974年   36篇
  1973年   20篇
  1971年   19篇
  1970年   20篇
  1967年   26篇
排序方式: 共有4527条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
A review of studies made in the compost production industry showed the biological agents posing a risk for workers were fungi and thermophile bacteria, gram-negative bacteria and endotoxins, with a prevalent inhalation exposure to airborne contaminated dusts. Medical examinations revealed cases of extrinsic allergic alveolitis due to A. fumigatus, and more frequently irritative and infectious disorders occurring especially in conditions of poor environmental hygiene and macroscopic dust pollution. For the evaluation of the air dispersion of microorganisms, which is high in compost transport and turning operations, at present no exposure limit values are available for biological agents; nevertheless, the concentrations measured were often higher than the limit values proposed for other manufacturing sectors by individual authors and by regulatory agencies in Europe, and were comparable to values observed in other industrial settings for which adverse health effects have been shown. Although the number of studies available are few in number, the results suggest that the hazards posed by microorganisms and the poor environmental hygiene conditions often encountered can undoubtedly be a source of risk for workers, which at present is difficult to establish but significant considering the high airborne concentrations of contaminated dust. Besides technical measures to avoid environmental macroscopic dispersion of dusts, measurement of airborne microbiological contaminants is also recommended. Health surveillance needs to be aimed at identifying subjects with hypersusceptibility to the infectious action of the pathogenetic and/or allergenic agents or with hypersensitivity to the same, and also to periodic control of respiratory organs.  相似文献   
995.
Demands and assessment of thin films in tribological applications Thin films for tribological use have been supported intensively in the last years and decades. For this reason lots of single results exist in this field of activity. But until now for engineers a handy und reliable method for the development of practical solutions is not available. The literature quoted at the end of this article deals with this problem and points out possibilities. The following paper presents selected results. Single aspects are here in this consequence only described without detailed documentation. To do this the quoted literature offers further information concerning the application of hard coatings and it refers to over 900 corresponding publications. Missing data on test parameters or boundary conditions of the test procedures as well as detailed information on all presented aspects are written down there. Tables to do selections and assessments qualify the reference as a useful handbook for the application of thin hard coatings in theory and practice. The author is pleased to help you to get the complete publication.  相似文献   
996.
Results from epidemiologic studies suggest that a carotenoid-rich diet may reduce risk for cervical cancer, possibly by inhibiting the progression of cervical intraepithelial neoplasia, a preneoplastic lesion of the cervical tissue. Laboratory studies suggest that the mechanism may be linked to the metabolism of carotenoids to retinoic acid or retinoic acid-like compounds, which has been hypothesized to occur in the cervical tissue. The purpose of this study was to demonstrate the presence of provitamin A carotenoids in biopsied samples of this peripheral tissue in human subjects and to examine the relationship between baseline concentrations of these carotenoids in plasma and normal cervical tissue in subjects who were being evaluated for possible participation in a diet intervention trial. Subjects were 13 women aged 19-41 y. With the use of HPLC methodology, plasma concentrations of alpha-carotene, beta-carotene and beta-cryptoxanthin were determined with UV/visible light detection for plasma and electrochemical detection for cervical tissue. Relationships between plasma and cervical tissue were evaluated with Pearson correlation analysis. Adjusted for plasma cholesterol concentration, plasma alpha-carotene and beta-carotene were correlated with cervical tissue concentrations (r = 0.91, P < 0.001; r = 0.90, P < 0.001; respectively). Adjusted for plasma cholesterol concentration, plasma beta-cryptoxanthin tended to be correlated with cervical tissue concentrations (r = 0.62, P = 0.058). These findings suggest that plasma concentrations of alpha-carotene and beta-carotene are good predictors of cervical tissue concentrations of these compounds in human subjects and describe a first step toward demonstrating a biological link between provitamin A carotenoids and cervical cancer in vivo.  相似文献   
997.
BACKGROUND: The Texas Medication Algorithm Project (TMAP), a public-academic collaborative effort, is a 3-phase project to develop, implement, and evaluate medication treatment algorithms for public sector patients with schizophrenia, major depressive disorders, or bipolar disorders. DISCUSSION: This paper, the first in a series describing the activities of the TMAP, focuses on the various definitions and reasons why guidelines have gained popularity. Also discussed are their strengths, the limitations of the various methods used to develop them, and potential barriers to their implementation.  相似文献   
998.
Recent advances in technology have not substantially changed the high mortality rate associated with acute renal failure (ARF). To obtain a simple, valid prognostic index, we retrospectively evaluated the relative importance of demographic data, causes (acute insults) of renal failure, and comorbid clinical conditions for the outcome in 102 ARF patients who received renal replacement therapy with an overall mortality rate of 65% (66 of 102). There were no significant differences between survivors and nonsurvivors in age and gender. Mortality according to acute insults was similar to that of the whole population studied. Of the 10 clinical conditions at the time of the first renal replacement therapy, mechanical ventilation (p = 0.0002), cardiac failure (p = 0.0006), hepatic failure (p = 0.003), central nervous system dysfunction (p = 0.005), and oliguria (p = 0.04) were found to be significantly related to mortality by univariate analysis. Furthermore, multivariate analysis demonstrated that only mechanical ventilation, cardiac failure, and hepatic failure were significant risk factors. Survival was directly related to the number of significant variables in univariate analysis: zero, 89% (8 of 9); one, 62% (21 of 34); two, 19% (5 of 27); three, 10% (2 of 20); four, 0% (0 of 8); five, 0% (0 of 4). This simple and early prognostic index, derived from the assessment of clinical conditions which were easily determined at the patient's bedside, could be useful for outcome prediction in ARF patients requiring renal replacement therapy.  相似文献   
999.
1000.
Electrophoretic karyotype (EK) was used to type 13 clinical isolates of Cryptococcus neoformans from eight AIDS patients. All of the isolates were also tested for their in vitro susceptibilities to fluconazole, itraconazole, D0870, flucytosine, and amphotericin B by a broth macrodilution technique performed according to the National Committee for Clinical Laboratory Standards recommendations. Although all strains were isolated from a limited geographic area, DNA typing showed a wide genetic variation in this group of patients, yielding seven different patterns. Two patients in whom C. neoformans was isolated in the same time period shared similar EK profiles, suggesting the possibility of cross-infection. In three patients, sequential isolates were evaluated: in two of them, EK analysis showed the persistence of the same genotype throughout the infection, whereas from the third, two isolates of C. neoformans with two different DNA profiles were obtained. Despite the small number of strains considered in this study, our susceptibility data indicate that C. neoformans isolates are very susceptible to the new triazoles.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号