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   2397285篇
  免费   185828篇
  国内免费   5072篇
耳鼻咽喉   33714篇
儿科学   80408篇
妇产科学   67316篇
基础医学   340709篇
口腔科学   64918篇
临床医学   214237篇
内科学   475230篇
皮肤病学   54374篇
神经病学   193198篇
特种医学   93434篇
外国民族医学   1051篇
外科学   362340篇
综合类   54266篇
现状与发展   4篇
一般理论   797篇
预防医学   185915篇
眼科学   54501篇
药学   173987篇
  3篇
中国医学   5362篇
肿瘤学   132421篇
  2019年   18957篇
  2018年   26887篇
  2017年   20338篇
  2016年   22869篇
  2015年   25927篇
  2014年   36283篇
  2013年   54111篇
  2012年   74077篇
  2011年   78476篇
  2010年   46537篇
  2009年   44161篇
  2008年   72981篇
  2007年   77509篇
  2006年   77934篇
  2005年   75768篇
  2004年   72959篇
  2003年   69914篇
  2002年   68134篇
  2001年   116837篇
  2000年   120251篇
  1999年   101169篇
  1998年   28324篇
  1997年   25562篇
  1996年   25900篇
  1995年   24599篇
  1994年   22713篇
  1993年   21211篇
  1992年   78122篇
  1991年   75412篇
  1990年   72853篇
  1989年   69487篇
  1988年   63905篇
  1987年   62642篇
  1986年   58503篇
  1985年   55967篇
  1984年   42438篇
  1983年   35795篇
  1982年   21375篇
  1981年   19193篇
  1979年   37804篇
  1978年   26483篇
  1977年   22162篇
  1976年   20874篇
  1975年   22098篇
  1974年   26214篇
  1973年   25301篇
  1972年   23476篇
  1971年   21307篇
  1970年   20243篇
  1969年   18498篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
Bernard–Soulier syndrome (BSS) is a rare autosomal recessively inherited bleeding disorder. Pregnancy in patients with BSS is characterized by ante‐, intra‐, or postpartum haemorrhage, which may be delayed and severe. There is no consensus in the management of BSS in pregnancy and so far only 16 pregnancies in nine patients have been described. We report a further three pregnancies in two women with the syndrome. We also outline our management of pregnant patients with BSS.  相似文献   
33.
Multi-day signals, generally with duration of 2-10 days, are a prominent temporal variation type of radon (Rn) in geogas in the unsaturated zone. Rare multi-day Rn signals have been found which are characterized by: (a) a declining limb lasting up to 10 days which conforms to the radioactive decay of Rn, (b) recurs at the same location and (c) is recorded in diverse situations-volcanic and seismogenic. It suggested that a Rn blob is injected at a lower level on a steady upward flow of geogas whereby the rise and final fall of the signal are attributed to the edges of the blob while the central Rn-decay segment records the passing of the decaying blob itself. Rn-decay signals are a small subset of multi-day Rn signals which are considered as highly irregular and unusable for the understanding of geophysical processes. In difference, it is concluded that multi-day Rn signals are probably proxies of subtle geodynamic processes at upper crustal levels and are therefore significant for studying such processes.  相似文献   
34.
Conclusion  Several quality-control measures take place before (patient and camera preparation) and during SPECT acquisition to achieve high-quality images. Not uncommonly, technologists and physicians are left with suboptimal images that have to be addressed to reach the “right answer” for patient diagnosis and hence management. In many cases patients may be reimaged, especially if the problem is detected early, but in other cases either the patient has left the nuclear laboratory or there is an inevitable problem that, even with reimaging, will not be resolved. In these situations the technologist and physician have to seek the available techniques to obtain the best images possible. These resources are discussed in this issue as an aid in quality control to obtain the best possible images.  相似文献   
35.
36.
We study the image formation of vibro-acoustography systems based on a concave sector array transducer taking into account depth-of-field effects. The system point-spread function (PSF) is defined in terms of the acoustic emission of a point-target in response to the dynamic radiation stress of ultrasound. The PSF on the focal plane and the axis of the transducer are presented. To extend the obtained PSF to the 3D-space, we assume it is a separable function in the axial direction and the focal plane of the transducer. In this model, an image is formed through the 3D convolution of the PSF with an object function. Experimental vibro-acoustography images of a breast phantom with lesion-like inclusions were compared with simulated images. Results show that the experimental images are in good agreement with the proposed model.  相似文献   
37.
38.
BACKGROUND: The laparoscopic resection of rectal cancer shows morbidity and oncological safety comparable to the open approach, but morbidity increases after conversion to open resection. No oncological long-term results are available for the latter patients. METHODS: From 01/01/2000-31/12/2002, patients with curatively resected rectal cancer enrolled in a observational study were evaluated for morbidity, mortality, tumor- and local recurrence rate, paying attention to patients with conversion from laparoscopic to open resection. RESULTS: 237 (3.3%) of 7,189 patients underwent laparoscopic resection (ITT). These patients showed significantly more T1/2 tumors (P<0.001) in earlier UICC stages (P<0.001) than open resected patients. 35 (14.8%) of 237 laparoscopic procedures were converted. Compared with patients receiving complete laparoscopic or open resection, these patients showed significantly higher frequencies of intraoperative (P<0.001) and general postoperative complications (P=0.003) as well as the highest overall morbidity (P=0.031). After a median follow-up of 30.1 months, the highest 5-year local recurrence rate was found in the converted group (16.0%). The laparoscopically resected patients showed a local recurrence rate of 3.3%, patients with open resection of 12.4% (P=0.082). The disease-free survival rate did not differ between the groups (P=0.585). CONCLUSION: Laparoscopic resection of rectal cancer provides oncological results similar to open resection. After conversion, the short and oncological long-term outcomes were worse. Considering a conversion rate of 15%, only a strict indication for the laparoscopic approach can be allowed, and laparoscopic resection should be performed at centers.  相似文献   
39.
40.
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