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   3366940篇
  免费   245492篇
  国内免费   8413篇
耳鼻咽喉   45365篇
儿科学   110922篇
妇产科学   94122篇
基础医学   479243篇
口腔科学   93820篇
临床医学   310841篇
内科学   658434篇
皮肤病学   78954篇
神经病学   276029篇
特种医学   128697篇
外国民族医学   964篇
外科学   496016篇
综合类   69055篇
现状与发展   7篇
一般理论   1448篇
预防医学   266047篇
眼科学   75946篇
药学   246057篇
  12篇
中国医学   6467篇
肿瘤学   182399篇
  2019年   26436篇
  2018年   36780篇
  2017年   28341篇
  2016年   32422篇
  2015年   36829篇
  2014年   50724篇
  2013年   76924篇
  2012年   102329篇
  2011年   108565篇
  2010年   64986篇
  2009年   62479篇
  2008年   101929篇
  2007年   108439篇
  2006年   109655篇
  2005年   105761篇
  2004年   101799篇
  2003年   98116篇
  2002年   94821篇
  2001年   156291篇
  2000年   159946篇
  1999年   135106篇
  1998年   39153篇
  1997年   34969篇
  1996年   35424篇
  1995年   34078篇
  1994年   31420篇
  1993年   29474篇
  1992年   106245篇
  1991年   103125篇
  1990年   99911篇
  1989年   96440篇
  1988年   88942篇
  1987年   87162篇
  1986年   82169篇
  1985年   78306篇
  1984年   58900篇
  1983年   50244篇
  1982年   29964篇
  1981年   26933篇
  1979年   53030篇
  1978年   37960篇
  1977年   32213篇
  1976年   29795篇
  1975年   31903篇
  1974年   38011篇
  1973年   36666篇
  1972年   34518篇
  1971年   32090篇
  1970年   29858篇
  1969年   28501篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
972.
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   
973.
目的:在瑞典儿童群体中,研究瑞典语译的出院后行为学问卷调查(PHBQ)的有效性和可行性。方法:利用回译的方法,将PHBQ翻译成瑞典语。340名2~13岁间的小儿被纳入研究对象,均曾有过麻醉下接受选择性外科手术或诊断过程的住院史。利用旋光性甲戊炔醇主成分分析的探测性因素分析法分析结果。选择一匹配于该模型的可靠的适合度测量法,利用证实性的因素分析,检查数据的适合度(所有因素P〉0.09)。  相似文献   
974.
975.
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   
976.
977.
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   
978.
979.
980.
Perforator flaps are perfused through a long vessel whose calibre decreases from its origin to the skin, because all branches have been sealed, resulting in a conduit with resistances in series, rather than a tree with resistances in parallel, as in the normal systemic circulation. This study was planned to assess whether the differences between perforator flap and normal systemic vasculature have an impact on haemodynamic parameters in perforator flaps and on their clinical significance. The study was performed on 10 patients. Echo-colour-Doppler measurement of diameters, velocity of flow and calculations of flow rate were made at the level of flap pedicle artery and skin perforator artery, pre- and post-operatively in each patient. Statistical analysis used the Wilcoxon matched pairs signed sum rank test. Our data show that in the donor area pre-operatively, blood velocity in skin artery perforator is lower that in the corresponding pedicle artery, whereas post-operatively, in perforator flaps, blood velocity in the perforator is higher than in the pedicle. The difference was statistically significant (P<0.01). There is an inversion of the gradient of blood velocity between pedicle artery and perforator artery compared to normal circulation. Furthermore, in normal circulation flow through the perforator was found smaller than that at the pedicle, whereas in perforator flaps, flow through the perforator is smaller but is a greater proportion of the flow through the pedicle and the difference is statistically significant (P<0.01). Therefore, the velocity of blood and the rate of flow reaching the skin are higher in perforator flaps than in normal circulation.  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