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   7063篇
  免费   9篇
  国内免费   1篇
电工技术   44篇
化学工业   113篇
金属工艺   23篇
机械仪表   16篇
建筑科学   8篇
能源动力   14篇
轻工业   32篇
水利工程   3篇
石油天然气   4篇
无线电   137篇
一般工业技术   121篇
冶金工业   6495篇
原子能技术   44篇
自动化技术   19篇
  2022年   6篇
  2021年   8篇
  2019年   9篇
  2018年   12篇
  2017年   9篇
  2016年   7篇
  2015年   7篇
  2014年   7篇
  2013年   25篇
  2012年   19篇
  2011年   22篇
  2010年   16篇
  2009年   28篇
  2008年   30篇
  2007年   26篇
  2006年   18篇
  2005年   24篇
  2004年   23篇
  2003年   21篇
  2002年   17篇
  2001年   14篇
  2000年   9篇
  1999年   196篇
  1998年   2086篇
  1997年   1169篇
  1996年   754篇
  1995年   401篇
  1994年   349篇
  1993年   407篇
  1992年   51篇
  1991年   105篇
  1990年   86篇
  1989年   85篇
  1988年   85篇
  1987年   92篇
  1986年   79篇
  1985年   74篇
  1984年   4篇
  1983年   17篇
  1982年   40篇
  1981年   49篇
  1980年   41篇
  1979年   4篇
  1978年   19篇
  1977年   164篇
  1976年   320篇
  1975年   15篇
  1973年   3篇
  1972年   3篇
  1955年   7篇
排序方式: 共有7073条查询结果,搜索用时 10 毫秒
71.
Investigation of the correlation between longitudinal photon density distribution and spectral linewidth re-broadening, in conjunction with carefully designed coupling optics, enable laser modules that simultaneously achieve very high fibre-coupled power of 175 mW and very narrow linewidth<1 MHz even at /spl sim/120 mW of output power to be successfully fabricated.  相似文献   
72.
Large bone flaps for free transfer can be successfully and safely harvested based on the deep branch of the superior gluteal artery. The anatomy is consistent, the vessels are large, and the complications of this technique are minimal.  相似文献   
73.
74.
Mass treatment of the human population with niclosamide was carried out in 2 villages in rural Guatemala where Taenia solium was endemic, to determine how this would affect the epidemiology of the parasite. Intestinal taeniasis was diagnosed by microscopy and coproantigen testing, and porcine cysticercosis by a specific Western blot. Before mass treatment, the prevalence of human taeniasis was 3.5%; 10 months after treatment it was 1%, a significant decrease (P < 10(-4)). All tapeworms that could be identified to the species level were T. solium. Similarly, the seroprevalence of antibodies to cysticercosis in pigs declined from 55% before treatment to 7% 10 months after treatment, once again a significant decrease (P < 10(-6)). These effects were seen in both villages. The possible use of mass chemotherapy as a tool in the control of T. solium is discussed.  相似文献   
75.
76.
The available surgical and non-surgical therapy options for treatment of gallstone disease are presented. Conventional cholecystectomy is regarded as standard therapy of symptomatic cholecystolithiasis. Other modes of therapy may be indicated under certain circumstances, depending on the results of imaging procedures. In this context conventional X-ray examination, oral and intravenous cholecystography, sonography, computed tomography, endoscopic retrograde cholangiography/cholecystography, and magnetic resonance imaging are discussed and their influence on therapeutic decisions is explained.  相似文献   
77.
A case of primary carcinoid tumor arising in the liver of a 69 year old woman with no endocrine symptoms is reported. Histopathologically, the tumor was diagnosed initially as a hepatocellular carcinoma in the biopsy specimen, and was shown subsequently to be a carcinoid tumor, demonstrating diffuse positive staining with Grimelius method. Mucin stained with periodic acid-Schiff (PAS), alcian-blue, and mucicarmine, and was shown partially in the glandular structures. Immunohistochemically, most of the tumor cells stained positively for chromogranin-A, epithelial membrane antigen (EMA) and neuron specific enolase (NSE). Ultrastructural examination revealed electron-dense core granules, measuring 40-120 nm in diameter in some of the tumor cells. Intensive and careful searches pre- and post-operatively revealed no other primary source of tumor other than the liver. The patient was reported well with no symptoms 3 1/2 years after the operation. This case is considered to be a primary hepatic carcinoid tumor. The recent literature is reviewed, and the possible histogenesis of hepatic carcinoid tumor is discussed.  相似文献   
78.
79.
We analyzed the first 5 years of surveillance data from the Established Population for the Epidemiologic Studies of the Elderly (EPESE) in the Piedmont of North Carolina (n = 4162) to estimate the effect of a global self-rating of health on survival. Covariates used in Cox proportional hazard models included sociodemographic factors, chronic medical conditions, activities of daily living, use of health services, health risk behaviors, cognitive function, affective mood, and negative life events. Adjusted risk of mortality associated with poor (compared to excellent) self-ratings of health was significantly elevated among urban men only. Confounders of the association between survival and overall health assessment varied widely by subgroup. Pooled estimates from heterogeneous populations may mask significant subgroup differences both in the pattern of variables that mediate crude risk and also in the magnitude of residual risk of global self-ratings of health.  相似文献   
80.
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