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   3458427篇
  免费   295268篇
  国内免费   13899篇
耳鼻咽喉   47400篇
儿科学   109360篇
妇产科学   87957篇
基础医学   550599篇
口腔科学   93242篇
临床医学   313310篇
内科学   612741篇
皮肤病学   89493篇
神经病学   298216篇
特种医学   138122篇
外国民族医学   299篇
外科学   534397篇
综合类   106099篇
现状与发展   24篇
一般理论   2268篇
预防医学   294629篇
眼科学   78789篇
药学   238000篇
  25篇
中国医学   9569篇
肿瘤学   163055篇
  2021年   55258篇
  2020年   35153篇
  2019年   58199篇
  2018年   71530篇
  2017年   54454篇
  2016年   60096篇
  2015年   74199篇
  2014年   108522篇
  2013年   173582篇
  2012年   93015篇
  2011年   93048篇
  2010年   116804篇
  2009年   121175篇
  2008年   79800篇
  2007年   83024篇
  2006年   93527篇
  2005年   88999篇
  2004年   90924篇
  2003年   81788篇
  2002年   70874篇
  2001年   111012篇
  2000年   104607篇
  1999年   102183篇
  1998年   66168篇
  1997年   63794篇
  1996年   61993篇
  1995年   57740篇
  1994年   51753篇
  1993年   48354篇
  1992年   73481篇
  1991年   70209篇
  1990年   66544篇
  1989年   65103篇
  1988年   60372篇
  1987年   59041篇
  1986年   55864篇
  1985年   55966篇
  1984年   50420篇
  1983年   45765篇
  1982年   42546篇
  1981年   39966篇
  1980年   37666篇
  1979年   41775篇
  1978年   36565篇
  1977年   33114篇
  1976年   30454篇
  1975年   29033篇
  1974年   30273篇
  1973年   29040篇
  1972年   27042篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A national conference on organ donation after cardiac death (DCD) was convened to expand the practice of DCD in the continuum of quality end-of-life care. This national conference affirmed the ethical propriety of DCD as not violating the dead donor rule. Further, by new developments not previously reported, the conference resolved controversy regarding the period of circulatory cessation that determines death and allows administration of pre-recovery pharmacologic agents, it established conditions of DCD eligibility, it presented current data regarding the successful transplantation of organs from DCD, it proposed a new framework of data reporting regarding ischemic events, it made specific recommendations to agencies and organizations to remove barriers to DCD, it brought guidance regarding organ allocation and the process of informed consent and it set an action plan to address media issues. When a consensual decision is made to withdraw life support by the attending physician and patient or by the attending physician and a family member or surrogate (particularly in an intensive care unit), a routine opportunity for DCD should be available to honor the deceased donor's wishes in every donor service area (DSA) of the United States.  相似文献   
992.
993.
994.
Effect of catalase supplementation in storage media for avulsed teeth   总被引:1,自引:0,他引:1  
Abstract – The type of liquid medium used to store avulsed teeth prior to replantation has been shown to affect the long‐term prognosis. One possibility is that some storage media contain hydrogen peroxide (H2O2) that may be toxic to periodontal ligament cells. Therefore, the aim of this study was to determine if the addition of catalase to storage media improved the prognosis of replanted dog teeth. Forty‐eight mongrel premolar roots were endodontically treated, extracted, randomly divided and placed into one of four storage media: Hank's balanced salt solution (HBSS), containing no antioxidant); Viaspan, containing the antioxidant, glutathione, or the same two media supplemented with catalase(100 U ml?1) for 1, 5, or 26 h prior to replantation. After 2 months, the dogs were euthanized and the roots histologically examined to evaluate the attachment tissues. Regardless of the storage medium used, overall healing was excellent and only 4% of the roots displayed inflammatory or replacement resorption. When roots from the different storage media were compared, those stored in HBSS were found to display the highest incidence of surface resorption (55.7%). Supplementation of HBSS with catalase resulted in a lower level of surface resorption (48.6%) that was statistically significant (P < 0.05). Roots stored in Viaspan – or + catalase displayed even lower levels of surface resorption (41.3 and 38.2%, respectively). The improvement observed with catalase‐supplemented HBSS was confined to the 45‐min incubation period; only Viaspan – or + catalase reduced surface resorption at the 5‐ and 26‐h incubations. Collectively, these data demonstrate that roots stored in media containing antioxidant activity undergo less surface resorption. These results suggest that low levels of H2O2 in storage media for avulsed teeth may adversely affect periodontal ligament cells.  相似文献   
995.
996.
997.
998.
999.
OBJECTIVES: Patients undergoing emergent endotracheal intubation are at increased risk for developing pneumonia. Although numerous strategies have been investigated to reduce ventilator-associated pneumonia (VAP), the incidence of VAP and its associated mortality remains high. This investigation tested the hypothesis that LiquiVent (Alliance Pharmaceutical, San Diego, CA-LV) delivered antibiotics (via spray-dried microspheres-SDM) would improve survival in a rat model of descending gram-negative pneumonia. METHODS: Wistar rats (n = 49) were randomized to receive prophylaxis with 1). nothing (controls); 2). intramuscular (IM) tobramycin, 3). intratracheal LV plus SDM shells (vehicle), 4). intratracheal LV plus SDM shells plus IM tobramycin, or 5). intratracheal LV plus SDM containing 1 mg/kg of tobramycin. All interventions were given 24 hours before a bacterial challenge with 10(8) colony-forming units of intratracheal Klebsiella pneumoniae. Mortality at ten days was the sole outcome measure. Survival in individual groups was compared with controls by Fisher's exact test with Bonferroni correction for multiple comparisons. RESULTS: All animals in the control group died of pneumonia within ten days of bacterial inoculation (0% survival). Prophylaxis with either IM tobramycin or SDM vehicle plus IM tobramycin provided no protection (0% survival). This is in sharp contrast to the cohort receiving pretreatment with tobramycin-containing SDM delivered via LV, in which 60% of the animals survived to study completion (p < 0.05). CONCLUSIONS: Prophylaxis with SDM containing antibiotics delivered in low-dose LV provided significant protection in a rat model of descending gram-negative pneumonia. These data support the hypothesis that perfluorocarbon-delivered intratracheal antimicrobials may be useful in the prevention of VAP.  相似文献   
1000.
Clinicopathological and electron microscopical findings of eight cases of enzootic nasal adenocarcinoma of sheep, diagnosed solely in one big flock in Slovenia between years 2001 and 2003 are described. All affected sheep were female, their mean age was 4.5 ± 1.5 years and they either belonged to the Istrian pramenka breed (five sheep) or were crossbreeds (three sheep). Tumours that arose from the ethmoid area of the nasal cavity were unilateral in six cases (75%) and bilateral in two cases (25%). All tumours were classified as adenocarcinomas by histopathological examination and they displayed either a combination of tubular and papillary growth or less often solely tubular proliferation. No metastases were detected in regional lymph nodes, brain or other organs. Electron microscopical studies performed on the reprocessed paraffin‐embedded tissues revealed the presence of the virus‐like particles with an average diameter between 70 and 90 nm.  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