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   2264篇
  免费   3篇
  国内免费   1篇
电工技术   3篇
化学工业   39篇
金属工艺   1篇
机械仪表   6篇
建筑科学   7篇
能源动力   5篇
轻工业   6篇
水利工程   1篇
石油天然气   1篇
无线电   12篇
一般工业技术   29篇
冶金工业   2128篇
原子能技术   3篇
自动化技术   27篇
  2020年   2篇
  2019年   2篇
  2017年   2篇
  2014年   2篇
  2013年   14篇
  2012年   5篇
  2011年   8篇
  2010年   5篇
  2009年   7篇
  2008年   5篇
  2007年   13篇
  2006年   9篇
  2005年   8篇
  2004年   6篇
  2003年   12篇
  2002年   5篇
  2001年   8篇
  2000年   8篇
  1999年   72篇
  1998年   626篇
  1997年   367篇
  1996年   220篇
  1995年   116篇
  1994年   111篇
  1993年   131篇
  1992年   18篇
  1991年   27篇
  1990年   28篇
  1989年   40篇
  1988年   36篇
  1987年   45篇
  1986年   34篇
  1985年   23篇
  1983年   9篇
  1982年   9篇
  1981年   16篇
  1980年   14篇
  1979年   4篇
  1978年   5篇
  1977年   52篇
  1976年   115篇
  1975年   6篇
  1972年   2篇
  1968年   1篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
  1961年   2篇
  1960年   1篇
  1955年   3篇
排序方式: 共有2268条查询结果,搜索用时 0 毫秒
31.
32.
We report two patients with paraneoplastic limbic and brainstem encephalitis associated with occult nonmetastatic testicular seminoma. In each patient, the neoplasm was detectable only by testicular ultrasonography. Male patients with this syndrome in whom lung cancer is not found should undergo testicular ultrasonography as part of the search for an extrapulmonary neoplasm. A normal clinical testicular examination is insufficient to exclude an occult seminoma.  相似文献   
33.
This study compared prototype and rote instruction of English names for Chinese visual characters. In the prototype condition, participants were taught the meaning of the prototype that served as the distinctive feature of multicomponent characters. In the rote condition, participants traced the character and wrote its translation. Participants learned more rapidly and maintained more words in the prototype condition.  相似文献   
34.
35.
36.
37.
OBJECTIVE: To determine whether concurrent intravenous administration of the loop diuretic ethacrynic acid potentiates the toxicity of the aminoglycoside antibiotic gentamicin applied topically on the round window. STUDY DESIGN: The authors studied the effects on cochlear sensitivity of co-administered intracardiac ethacrynic acid (40 mg/kg) and high-dose topical gentamicin solution (100%) applied to the round window. Comparisons were made with animals receiving ethacrynic acid plus systemic gentamicin (100 mg/kg); topical gentamicin alone; systemic gentamicin alone; and intravenous ethacrynic acid alone. METHODS: Experiments were carried out on pigmented guinea pigs weighing 400 to 500 g. Changes in cochlear function were characterized by monitoring shifts in compound action potential (CAP) thresholds by use of chronic indwelling electrodes implanted at the round window, vertex, and contralateral mastoid. RESULTS: After 20 days animals receiving ethacrynic acid in combination with topical gentamicin to the round window failed to demonstrate a significant deterioration in cochlear sensitivity, whereas all animals receiving systemic gentamicin plus ethacrynic acid experienced profound increases in CAP thresholds. CONCLUSIONS: This study supports the contention that ethacrynic acid potentiates aminoglycoside ototoxicity by facilitating the entry of the antibiotics from the systemic circulation into the endolymph. In addition, this study answers important clinical concerns regarding the safety of the use of topical aminoglycoside agents in combination with loop diuretics.  相似文献   
38.
OBJECTIVE: Multivariate statistical methods were used to identify patient-related variables that predicted length of stay in a single psychiatric facility. The study investigated whether these variables remained stable over time and could be used to provide individual physicians with data on length of stay adjusted for differences in clinical caseloads and to detect trends in the physicians' practice patterns. METHODS: Data on all patients discharged over two six-month periods were collected at an acute psychiatric inpatient facility. Stepwise multiple regression analyses were conducted on the two datasets. RESULTS: The results from both analyses revealed that five variables significantly predicted length of stay and were stable over time. They were a primary diagnosis of schizophrenia, the number of previous admissions, a primary diagnosis of a mood disorder, age, and a secondary diagnosis of an alcohol- or other drug-related disorder. For some physicians, the mean length of stay of their patients differed significantly from the length predicted by the regression model--generally, it was shorter. CONCLUSIONS: The results demonstrate that patient-related predictors of length of stay in a single psychiatric hospital can be identified using relatively simple statistical procedures and can be consistent across a large dataset and over time.  相似文献   
39.
This article summarizes an approach for improving the indoor air quality (IAQ) in a building by providing feedback on the performance of the ventilation system. The delivery of adequate quantities of ventilation to all building occupants is necessary for the achievement of good IAQ. Feedback on the performance includes information on the adequacy of ventilation provided, the effectiveness of the distribution of this air, the adequacy of the duration of operation of the ventilation system, and the identification of leakage into the return plenum, either of outdoor or supply air. Keeping track of ventilation system performance is important not only in terms of maintaining good IAQ, but also making sure that this system continues to perform as intended after changes in building use. Information on the performance of the ventilation system is achieved by means of an automated sampling system that draws air from multiple locations and delivers it to both a carbon dioxide monitor and dew point sensor. The use of single shared sensors facilitates calibration checks as well as helps to guarantee data integrity. This approach to monitoring a building's ventilation system offers the possibility of achieving sustainable performance of this important aspect of good IAQ.  相似文献   
40.
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