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   2378461篇
  免费   173755篇
  国内免费   3424篇
耳鼻咽喉   32323篇
儿科学   76786篇
妇产科学   63427篇
基础医学   351809篇
口腔科学   64128篇
临床医学   214895篇
内科学   462674篇
皮肤病学   52340篇
神经病学   187961篇
特种医学   88969篇
外国民族医学   490篇
外科学   357183篇
综合类   47958篇
现状与发展   12篇
一般理论   866篇
预防医学   185910篇
眼科学   55321篇
药学   176843篇
  11篇
中国医学   4600篇
肿瘤学   131134篇
  2021年   19733篇
  2019年   20247篇
  2018年   27986篇
  2017年   20969篇
  2016年   23447篇
  2015年   26442篇
  2014年   37134篇
  2013年   55416篇
  2012年   76703篇
  2011年   81444篇
  2010年   48126篇
  2009年   45624篇
  2008年   76285篇
  2007年   81199篇
  2006年   81910篇
  2005年   79259篇
  2004年   75737篇
  2003年   72977篇
  2002年   70574篇
  2001年   109121篇
  2000年   111813篇
  1999年   93870篇
  1998年   27237篇
  1997年   23905篇
  1996年   24229篇
  1995年   22918篇
  1994年   21060篇
  1993年   19882篇
  1992年   72258篇
  1991年   70336篇
  1990年   68636篇
  1989年   65894篇
  1988年   60508篇
  1987年   59337篇
  1986年   55411篇
  1985年   53200篇
  1984年   39482篇
  1983年   33539篇
  1982年   19974篇
  1979年   35979篇
  1978年   25747篇
  1977年   21337篇
  1976年   20429篇
  1975年   21903篇
  1974年   26244篇
  1973年   24899篇
  1972年   23269篇
  1971年   22127篇
  1970年   20310篇
  1969年   19384篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
The increased number of lymphocytes in airways during an asthmatic response is believed to be the result of increased recruitment of these cells. However, it is possible that a decreased apoptotic rate could also contribute to the increased number. The aim of the present study was to investigate whether allergen airway provocation influences the apoptotic phenotype of lung and peripheral blood lymphocytes (PBL) in subjects with atopic asthma. Bronchoalveolar lavage (BAL) lymphocytes and PBL from 12 asthmatic subjects previously challenged with allergen (n = 7) or saline (n = 5) were exposed to the apoptotic stimulus tributyltin (TBT) in vitro and assayed for apoptosis. Airway allergen provocation resulted in decreased sensitivity of BAL lymphocytes to TBT-induced apoptosis, with 42.2% (range 33.9-62.5%) apoptotic cells before challenge versus 23.5% (range 15.3-42.4%) after challenge, while PBL were unaffected. The increased apoptosis resistance correlated with higher numbers of Bcl-2-expressing lymphocytes. Interestingly, baseline caspase-3-like activity was significantly elevated in viable BAL lymphocytes compared with viable PBL, and was unaltered by allergen exposure. In conclusion, allergen inhalation renders bronchoalveolar lavage lymphocytes more resistant to apoptosis while peripheral blood lymphocytes were not influenced at all, indicating that the apoptotic phenotype of airway lymphocytes may play a role in asthmatic inflammation.  相似文献   
103.
104.
105.
106.
In patients with Type 2 diabetes, the appropriate intensity of glucose control is determined by age, life expectancy, and the presence of concomitant disease. Geriatric patients are especially susceptible to hypoglycaemia and therefore particular care should be taken in this group characterized by polypharmacy, renal or hepatic dysfunction, cardiovascular multimorbidity and malnutrition. As hypoglycaemia is a significant cause of morbidity and mortality, treatment regimens for diabetes should minimize the occurrence of hypoglycaemic episodes and be tailored to the patient's individual needs. The pharmacological options for treating Type 2 diabetes have increased considerably and the risk of hypoglycaemia of the currently available drugs varies considerably. Metformin, thiazolidinediones, and acarbose, oral antidiabetic drugs that decrease insulin resistance or postprandial glucose absorption, are associated with a low risk of hypoglycaemia. These drugs can also be used effectively in various combination regimens; however, by improving insulin sensitivity, combinations of metformin and thiolidinediones with sulphonylureas or meglitinides may considerably increase the risk of hypoglycaemia. On account of its complex pharmacoprofile glibenclamide is a problematic substance carrying a high risk of hypoglycaemia. There are limited preliminary data indicating that, under routine conditions, glimepiride may be associated with a lower risk of hypoglycaemia than glibenclamide and is no more likely to cause hypoglycaemia than other shorter-acting agents such as gliclazide and glipizide. Nateglinide and repaglinide as short-acting insulin secretagogues may be associated with a reduced risk of hypoglycaemia compared with glibenclamide, in particular when dosed flexibly. Repaglinide might be beneficial in individuals with renal impairment.  相似文献   
107.
BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a rare malignant tumour of the skin, with an estimated incidence of 0.8 to five cases per 1 million people per year. OBJECTIVE: To study epidemiological, immunohistochemical and clinical features, delay in diagnosis, type of treatment and outcome of DFSP from 1982 to 2002. METHODS: Using data from the population-based cancer registry, 66 patients with pathologically proved DFSP were included (fibrosarcomatous DFSP were excluded). Each patient lived in one of the four departments of Franche-Comté (overall population of 1 million people) at the time of diagnosis. The main data sources came from public and private pathology laboratories and medical records. The rules of the International Agency for Research on Cancer were applied. RESULTS: The estimated incidence of DFSP in Franche-Comté was about three new cases per 1 million people per year. Male patients were affected 1.2 times as often as female patients were. The trunk (45%) followed by the proximal extremities (38%) were the most frequent locations. DFSP occurred mainly in young adults between 20 and 39 years of age. Mean age at diagnosis was 43 years, and the mean delay in diagnosis was 10.08 years. Our 66 patients initially underwent a radical local excision. Among them, 27% experienced one or more local recurrences during 9.6 years of follow-up. There was one regional lymph node recurrence without visceral metastases. These recurrences were significantly related to the initial peripheral resection margins. We observed a local recurrence rate of 47% for margins less than 3 cm, vs. only 7% for margins ranging from 3 to 5 cm [P=0.004; OR=0.229 (95%, CI=0.103-0.510)]. The mean time to a first local recurrence was 2.65 years. Nevertheless, there was no death due to the DFSP course at the end of the follow-up, and the final outcome was favourable. CONCLUSION: Our study emphasizes the importance of wide local excision with margins of at least 3 cm in order to prevent local recurrence. However, the recent development of inhibitors of signal transduction by the PDGFB pathway should soon modify the surgical strategy, which is often too mutilating.  相似文献   
108.
A 65-year-old man developed acute limb ischemia, severe abdominal wall and lower limb livedo reticularis following a coronary angiogram. The differential diagnoses of acute limb ischemia and multiple cholesterol emboli syndrome (MCES) are discussed. This work was performed at Long Island Jewish Medical Center, 270-05, 76th Avenue, New Hyde Park, NY 11040.  相似文献   
109.
We describe the simple adaptation of a standard fluorescent microscope for illumination using a 'Royal Blue' Luxeon light emitting diode (LED) and demonstrate that this form of illumination is suitable for the detection of auramine O stained Mycobacterium spp. The low cost, low power consumption, safety and reliability of LEDs makes them attractive alternatives to mercury vapour lamps.  相似文献   
110.
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