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   6612篇
  免费   3篇
电工技术   6篇
化学工业   61篇
机械仪表   2篇
建筑科学   1篇
能源动力   25篇
轻工业   19篇
水利工程   6篇
石油天然气   6篇
无线电   17篇
一般工业技术   37篇
冶金工业   6409篇
原子能技术   2篇
自动化技术   24篇
  2019年   3篇
  2018年   4篇
  2017年   2篇
  2016年   3篇
  2015年   1篇
  2014年   4篇
  2013年   7篇
  2012年   10篇
  2011年   5篇
  2010年   6篇
  2009年   5篇
  2008年   9篇
  2007年   19篇
  2006年   18篇
  2005年   9篇
  2004年   8篇
  2003年   10篇
  2002年   14篇
  2001年   1篇
  2000年   3篇
  1999年   184篇
  1998年   2044篇
  1997年   1150篇
  1996年   735篇
  1995年   374篇
  1994年   336篇
  1993年   390篇
  1992年   43篇
  1991年   94篇
  1990年   70篇
  1989年   82篇
  1988年   77篇
  1987年   84篇
  1986年   72篇
  1985年   71篇
  1984年   5篇
  1983年   12篇
  1982年   34篇
  1981年   44篇
  1980年   38篇
  1979年   2篇
  1978年   18篇
  1977年   161篇
  1976年   322篇
  1975年   16篇
  1974年   2篇
  1973年   1篇
  1966年   2篇
  1965年   1篇
  1955年   7篇
排序方式: 共有6615条查询结果,搜索用时 15 毫秒
91.
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   
92.
93.
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   
94.
95.
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   
96.
97.
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   
98.
99.
100.
The cause of stuttering is unknown. Failure to develop left-hemispheric dominance for speech is a long-standing theory although others implicated the motor system more broadly, often postulating hyperactivity of the right (language nondominant) cerebral hemisphere. As knowledge of motor circuitry has advanced, theories of stuttering have become more anatomically specific, postulating hyperactivity of premotor cortex, either directly or through connectivity with the thalamus and basal ganglia. Alternative theories target the auditory and speech production systems. By contrasting stuttering with fluent speech using positron emission tomography combined with chorus reading to induce fluency, we found support for each of these hypotheses. Stuttering induced widespread overactivations of the motor system in both cerebrum and cerebellum, with right cerebral dominance. Stuttered reading lacked left-lateralized activations of the auditory system, which are thought to support the self-monitoring of speech, and selectively deactivated a frontal-temporal system implicated in speech production. Induced fluency decreased or eliminated the overactivity in most motor areas, and largely reversed the auditory-system underactivations and the deactivation of the speech production system. Thus stuttering is a disorder affecting the multiple neural systems used for speaking.  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