首页 | 官方网站   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   52653篇
  免费   2923篇
  国内免费   220篇
医药卫生   55796篇
  2023年   316篇
  2022年   331篇
  2021年   993篇
  2020年   722篇
  2019年   946篇
  2018年   1211篇
  2017年   1033篇
  2016年   1262篇
  2015年   1505篇
  2014年   1719篇
  2013年   2196篇
  2012年   3516篇
  2011年   3625篇
  2010年   2140篇
  2009年   1871篇
  2008年   3144篇
  2007年   3208篇
  2006年   3074篇
  2005年   2996篇
  2004年   2732篇
  2003年   2533篇
  2002年   2385篇
  2001年   1051篇
  2000年   1065篇
  1999年   960篇
  1998年   512篇
  1997年   375篇
  1996年   311篇
  1995年   258篇
  1994年   225篇
  1993年   206篇
  1992年   406篇
  1991年   416篇
  1990年   405篇
  1989年   346篇
  1988年   297篇
  1987年   295篇
  1986年   256篇
  1985年   259篇
  1984年   218篇
  1983年   142篇
  1982年   149篇
  1979年   199篇
  1978年   145篇
  1975年   156篇
  1974年   142篇
  1973年   159篇
  1972年   146篇
  1971年   133篇
  1970年   134篇
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
61.
It obviously escaped the notion of Egeland and Brinchman thatthe protocols additionally differ with regard to the washingsteps and buffer components used in the  相似文献   
62.
PURPOSE: To study the effect of treatment time prolongation following initial dose acceleration on the response of subcutaneously growing R1H tumor. MATERIAL AND METHODS: Continuous standard fractionation (30 fractions/40 days) was compared to initially accelerated treatment (30 fractions/21 days) followed by five to two fractions per week yielding total treatment times from 40 to 72 days. Local tumor control was assessed as endpoint. RESULTS: Radiation dose to control 50% of the tumors (TCD50%) decreased statistically significant from 83.5 Gy (95% confidence interval [CI]: 78.6 .. 88.4) for standard fractionation to 74.1 Gy (95% CI: 72.7 .. 75.5) determined for all accelerated treatment arms (p = 0.003). Prolongation of treatment time after initial acceleration from 40 to 72 days led to a small but statistically not significant increase in TCD50% from 72.0 Gy (95% CI: 71.0 .. 72.9) to 76.2 Gy (95% CI: 69.9 .. 82.4) corresponding to a repopulated dose of 0.9 Gy per week. This time factor is considerably smaller than for conventional radiation treatment as determined in previous experiments. CONCLUSION: The results indicate that initially accelerated irradiation not only improves local tumor control but also minimizes the negative effect of treatment time prolongation. This might be due to changes in tumor cell repopulation kinetics.  相似文献   
63.
64.
In the past, addiction disorders were considered to be mainly substance use disorders. The main focus has been on dependence disorders. Dependence criteria do not differ substantially in the two main classification systems ICD and DSM, while harmful use (ICD) and abuse (DSM) criteria show much less concordance. Presently diagnostic criteria for behavioral addiction disorders are only available for pathological gambling, however, under the category of disorders of impulse control, while other disorders have to be categorized under disorders not otherwise specified. Evidence of neurobiological similarities implies that future ICD and DSM revisions, in addition to other needed changes, will group behavioral addiction and substance use disorders together.  相似文献   
65.
Background: Although the activation-induced intracellular Ca2+ signal is disrupted by sensory neuron injury, the contribution of specific Ca2+ channel subtypes is unknown.

Methods: Transients in dissociated rat dorsal root ganglion neurons were recorded using fura-2 microfluorometry. Neurons from control rats and from neuropathic animals after spinal nerve ligation were activated either by elevated bath K+ or by field stimulation. Transients were compared before and after application of selective blockers of voltage-activated Ca2+ channel subtypes.

Results: Transient amplitude and area were decreased by blockade of the L-type channel, particularly during sustained K+ stimulation. Significant contributions to the Ca2+ transient are attributable to the N-, P/Q-, and R-type channels, especially in small neurons. Results for T-type blockade varied widely between cells. After injury, transients lost sensitivity to N-type and R-type blockers in axotomized small neurons, whereas adjacent small neurons showed decreased responses to blockers of R-type channels. Axotomized large neurons were less sensitive to blockade of N- and P/Q-type channels. After injury, neurons adjacent to axotomy show decreased sensitivity of K+-induced transients to L-type blockade but increased sensitivity during field stimulation.  相似文献   

66.
67.
Introduction Choroid plexus cysts can lead to isolation of the lateral ventricles and distension of the third ventricle. We present an ultrasonographic video documentation of an infant with variably shaped and localized choroid plexus cyst of the third ventricle. Case report An infant had periods of increased intracranial pressure with changing dilatation of the first to third ventricle. Cerebral ultrasonography of the not crying boy demonstrated a choroid plexus cyst limply hanging down from the roof of the third ventricle to the beginning of the aqueduct of Sylvius. During crying, the cyst prolapsed from the third into left lateral ventricle and was strangled by the foramen of Monro. Endoscopic cyst fenestration and third ventriculostomy continuously solved the problem of intermittent hydrocephalus occlusus. Conclusion Depending not only on localization and size but also on cyst form and cerebrospinal fluid pressure, a single choroid plexus cyst can cause various obstructions of cerebrospinal fluid pathways.  相似文献   
68.
A multiply injured patient’s airway is primarily secured with a laryngeal tube by the responding EMS. For helicopter transfer the flight physician decides not to intubate the patient’s trachea. Mechanical ventilation was performed without complications.  相似文献   
69.
70.
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-23

京公网安备 11010802026262号