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   765261篇
  免费   11031篇
  国内免费   2765篇
电工技术   14527篇
技术理论   5篇
综合类   1726篇
化学工业   123380篇
金属工艺   30831篇
机械仪表   23989篇
建筑科学   18296篇
矿业工程   5439篇
能源动力   19081篇
轻工业   67817篇
水利工程   8956篇
石油天然气   18152篇
武器工业   280篇
无线电   80067篇
一般工业技术   151219篇
冶金工业   132657篇
原子能技术   17621篇
自动化技术   65014篇
  2021年   8140篇
  2020年   5845篇
  2019年   7314篇
  2018年   12206篇
  2017年   12297篇
  2016年   13025篇
  2015年   8846篇
  2014年   14171篇
  2013年   36123篇
  2012年   22491篇
  2011年   29526篇
  2010年   23704篇
  2009年   25801篇
  2008年   26468篇
  2007年   26223篇
  2006年   22872篇
  2005年   20345篇
  2004年   18891篇
  2003年   18343篇
  2002年   17760篇
  2001年   17287篇
  2000年   16450篇
  1999年   16260篇
  1998年   37916篇
  1997年   27469篇
  1996年   21265篇
  1995年   16138篇
  1994年   14693篇
  1993年   14252篇
  1992年   11060篇
  1991年   10649篇
  1990年   10548篇
  1989年   10338篇
  1988年   9795篇
  1987年   8795篇
  1986年   8601篇
  1985年   9725篇
  1984年   8994篇
  1983年   8501篇
  1982年   7643篇
  1981年   7905篇
  1980年   7415篇
  1979年   7622篇
  1978年   7456篇
  1977年   8175篇
  1976年   10405篇
  1975年   6743篇
  1974年   6431篇
  1973年   6510篇
  1972年   5513篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
951.
BACKGROUND: Ascites in patients with hepatocellular carcinoma (HCC) is a poorly characterized subgroup of malignancy-related ascites. Not only the underlying liver disease, but also the tumor growth and spread contributes to the ascites formation. The authors differentiated ascites in HCC from other types of ascites. METHODS: The authors analyzed the ascitic fluid of 185 consecutive patients (89 liver cirrhosis, 33 HCC, 31 peritoneal carcinomatosis, 22 liver metastases, 10 spontaneous bacterial peritonitis). RESULTS: Each subgroup showed a typical pattern. Compared with the cirrhotic patients, those with HCC showed a higher frequency of positive cytologic findings (4 of 33 versus 0/89, P < 0.004), elevated fibronectin concentration (10/33 versus 8/89, P < 0.004), and elevated polymorphonuclear cell count (10/33 versus 5/89 P < 0.004). CONCLUSIONS: A significant number of patients with ascites and HCC patients showed signs of peritoneal infiltration with positive cytologic findings and increased concentration of fibronectin. Moreover, neutrocytic ascites without signs of superinfection is relatively common (30%).  相似文献   
952.
953.
In tests of direct-compression hydrochlorothiazide tablets prepared with either of two varieties of microcrystalline cellulose (Avicel PH 101 and Avicel PH 102), PH 102 tablets had better mechanical properties (owing to lower compressibility of mixtures and greater Interparticle bonding), while PH 101 tablets released the active principle faster. These differences are related to observed differences In tablet micropore structure.  相似文献   
954.
955.
956.
Translated from Metallurg, Vol. 39, No. 6, p. 45, June, 1995.  相似文献   
957.
A detailed review of SiGe epitaxial base technology is presented, which chronicles the progression of research from materials deposition through device and integration demonstrations, culminating in the first SiGe integrated circuit application. In part I of this paper, the requirements and processes for high-quality SiGe film preparation are discussed, with emphasis on fundamental principles. A detailed overview of SiGe HBT device design and implications for circuit applications is then presented  相似文献   
958.
With change abounding in Canada's health care system, nurses must redefine their roles. One role is in health promotion, a field where nurses have created a unique identity for themselves. But before advocating, the concept must be fully understood.  相似文献   
959.
Since foodborne diseases, especially those caused by bacteria, have become an increasingly important public health problem, the Authors conducted a survey in order to evaluate the organization of, and the intervention carried out by, six Public Health Services in the Lombardia region, after reports of foodborne diseases outbreaks. Lack of correct methodology was detected, not to mention the usual omission of epidemic curves and attack rates. Besides, too many microbiological tests were made and it took too much time to take care of and to report the outbreaks to Regional and National Health Authorities. Forty-one outbreaks were examined: 415 cases occurred (AR: 28.7%), most of which home-made food-related. In 25 outbreaks the suspected food vehicles were eggs or fish, but only 5 of them were confirmed by laboratory tests. Salmonella enterica, either serovar Eenteritidis or group D, appeared responsible for 26 of the outbreaks [corrected].  相似文献   
960.
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