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   1336377篇
  免费   114744篇
  国内免费   6365篇
耳鼻咽喉   16793篇
儿科学   43020篇
妇产科学   36632篇
基础医学   183696篇
口腔科学   36278篇
临床医学   120615篇
内科学   278386篇
皮肤病学   31888篇
神经病学   110496篇
特种医学   55542篇
外国民族医学   274篇
外科学   210537篇
综合类   31545篇
现状与发展   2篇
一般理论   414篇
预防医学   106535篇
眼科学   28067篇
药学   93705篇
  5篇
中国医学   2227篇
肿瘤学   70829篇
  2018年   13386篇
  2017年   10645篇
  2016年   12811篇
  2015年   14315篇
  2014年   19978篇
  2013年   29766篇
  2012年   36267篇
  2011年   38903篇
  2010年   24396篇
  2009年   23914篇
  2008年   36390篇
  2007年   38800篇
  2006年   39928篇
  2005年   38520篇
  2004年   36756篇
  2003年   35842篇
  2002年   33854篇
  2001年   66082篇
  2000年   67948篇
  1999年   56606篇
  1998年   16733篇
  1997年   15022篇
  1996年   16034篇
  1995年   16239篇
  1994年   15108篇
  1993年   14166篇
  1992年   47130篇
  1991年   45776篇
  1990年   43989篇
  1989年   41848篇
  1988年   38769篇
  1987年   38098篇
  1986年   35871篇
  1985年   34646篇
  1984年   26366篇
  1983年   22127篇
  1982年   13849篇
  1981年   12456篇
  1980年   11722篇
  1979年   23553篇
  1978年   17079篇
  1977年   14388篇
  1976年   13195篇
  1975年   13731篇
  1974年   16107篇
  1973年   15408篇
  1972年   14184篇
  1971年   13050篇
  1970年   11892篇
  1969年   11113篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
951.
952.
M E Baca  A M Mowat  S MacKenzie    D M Parrott 《Gut》1987,28(10):1267-1274
In this study we have investigated whether addition of bone marrow accessory cells or concurrent administration of recombinant IL-2 would allow intraepithelial lymphocytes (IEL) to induce a systemic, lethal GvHR in irradiated hosts. In addition we have studied the ability of IEL to migrate into lymphoid tissues after intravenous injection and compared this with their locomotor capacity in vitro.  相似文献   
953.
954.
955.
956.
957.
The isolated perfused working rat heart model of cardiopulmonary bypass was used to assess whether (a) allopurinol pretreatment enhances resistance to normothermic (30 min) or hypothermic (4 h) ischemia; (b) addition of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) to cardioplegic and/or reperfusion solutions are protective; (c) any protective effects are additive. With normothermic ischemia, allopurinol pretreatment improved recovery of aortic flow from its control value of 25 +/- 3% to 48 +/- 6% (P less than 0.05). Similarly, SOD plus CAT used during both ischemia and reperfusion improved recovery of aortic flow from a control value of 28 +/- 4% to 48 +/- 6% (P less than 0.05). However, various combinations of the two types of intervention afforded no additive protection. Under hypothermic (21 degrees C) conditions, allopurinol pretreatment was not effective, whereas SOD and CAT added during ischemia and reperfusion improved recovery of aortic flow from its control value of 53 +/- 4% to 69 +/- 5% (P less than 0.05). This value was similar to allopurinol pretreatment and SOD plus CAT added during ischemia and reperfusion (69 +/- 6%: P less than 0.05). These results provide further evidence that reperfusion-induced free radical formation may adversely affect postischemic recovery of function. The absence of an additive effect suggests a common mechanism of action, which is likely to involve the free radical-generating enzyme xanthine oxidase; however, other mechanisms may exist. Our results further support the use of antifree radical intervention in conjunction with cardioplegia to protect the heart during ischemia and reperfusion.  相似文献   
958.
Clinical data of 192 patients with breast cancer with a primary lesion of 2-5 cm (stage II according to the criteria recommended by the UICC) and with histopathologically confirmed positive axillary lymph nodes were analyzed. The patients were divided into three groups: 1) surgical excision alone; 2) surgery plus irradiation; and 3) surgery plus chemotherapy. It was shown that the 5-year survival rates for these groups were 40.5%, 61.0%, and 62.0%, respectively (P less than .05).  相似文献   
959.
The use of adjuvant radiation therapy in breast cancer patients treated with mastectomy and adjuvant chemotherapy has been controversial. In order to assess the necessity and effectiveness of adjuvant radiation therapy in this setting, we reviewed the results in 510 patients with T1-T3 tumors and pathologically positive nodes or tumors larger than 5 cm and negative nodes who were treated with adjuvant chemotherapy. Patients with four or more positive nodes or at least one positive apical node were randomized to receive either five or ten cycles of cyclophosphamide/Adriamycin (Adria Laboratories, Columbus, OH) (CA) and patients with one to three positive nodes or operable tumors larger than 5 cm and pathologically negative nodes were randomized to receive eight cycles of either cyclophosphamide, methotrexate, and 5-fluorouracil (5-FU) (CMF) or methotrexate and 5-FU (MF) chemotherapy. Two hundred six of these patients were subsequently rerandomized to receive either no further treatment or adjuvant radiotherapy. Thirty-five patients withdrew after randomization, including 34 who declined to receive radiotherapy. Radiation therapy consisted of 4,500 cGy in 5 weeks to the chest wall and appropriate draining lymph nodes. Median follow-up from chemotherapy randomization is 45 months for patients in the CA arm and 53 months for those in the CMF/MF arm. The crude rate of local failure (chest wall or draining lymph node areas) as first site of failure for patients randomized to receive chemotherapy only was 14%; for those randomized to receive both chemotherapy and radiotherapy it was 5% (P = .03). For patients in the CMF/MF arm, the rate of local failure as the first site of failure was nearly the same for patients randomized to chemotherapy only as for those randomized to adjuvant radiotherapy as well (5% v 2%). For patients in the CA arm, the crude rate of local failure was 20% for patients randomized to receive chemotherapy only, and 6% for those randomized to both types of adjuvant treatment (P = .03). Among the 43 patients treated with CA who actually received radiotherapy, there was only one local failure, compared with 12 local failures among the 59 patients (20%) who actually did not receive radiotherapy (P = .007). No significant difference was seen in disease-free survival or overall survival in either the CA or the CMF/MF arm between patients randomized to receive radiation therapy and those randomized to no further treatment.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
960.
Conclusions Since the discovery of HDV in 1977 byRizzetto and collegues (10), several studies regarding the pathogenesis, natural history and epidemiology of this infection have been accumulated. It emerges that HDV is an agent with unusual biologic properties which requires HBV replication for its expression. Given the obligatory association between HDV and HBV, transmission of HDV follows the same routes of HBV transmission. This implies that one expects HDV infection to be much more prevalent in countries with high HBsAg carrier rates. This is true in most areas of the world but not in Far East Asia. Endemicity of HDV is maintained in the community through the network of HBsAg carriers. HDV can be transmitted to HBV positive and negative individuals, but survives only after encountering the carrier. Recent outbreaks of severe epidemics of fulminant hepatitis due to HDV among the Yucpa Indians in Northern Venezuela, pointed out very clearly that HDV superinfection is an ominous risk for all populations where HBV is endemic.  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