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   1528580篇
  免费   115881篇
  国内免费   6375篇
耳鼻咽喉   18119篇
儿科学   49981篇
妇产科学   39966篇
基础医学   204532篇
口腔科学   37875篇
临床医学   133941篇
内科学   312294篇
皮肤病学   32754篇
神经病学   127819篇
特种医学   65076篇
外国民族医学   274篇
外科学   242844篇
综合类   34142篇
现状与发展   2篇
一般理论   416篇
预防医学   125302篇
眼科学   30905篇
药学   104134篇
  5篇
中国医学   2856篇
肿瘤学   87599篇
  2018年   35837篇
  2017年   28589篇
  2016年   33816篇
  2015年   15375篇
  2014年   20886篇
  2013年   30658篇
  2012年   43314篇
  2011年   60620篇
  2010年   43446篇
  2009年   35975篇
  2008年   57544篇
  2007年   63238篇
  2006年   40669篇
  2005年   41509篇
  2004年   41322篇
  2003年   42053篇
  2002年   37831篇
  2001年   66506篇
  2000年   68671篇
  1999年   56890篇
  1998年   17062篇
  1997年   15391篇
  1996年   16210篇
  1995年   16438篇
  1994年   15320篇
  1993年   14334篇
  1992年   47227篇
  1991年   45927篇
  1990年   44166篇
  1989年   41959篇
  1988年   38878篇
  1987年   38216篇
  1986年   35961篇
  1985年   34746篇
  1984年   26427篇
  1983年   22180篇
  1982年   13956篇
  1981年   12467篇
  1980年   11838篇
  1979年   23647篇
  1978年   17138篇
  1977年   14406篇
  1976年   13248篇
  1975年   13728篇
  1974年   16134篇
  1973年   15405篇
  1972年   14175篇
  1971年   13036篇
  1970年   11910篇
  1969年   11138篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
The incidence of eye infections in a community is generally accepted as an indicator of the adequacy of water supply for their needs. However, discrepancies in the published results from various studies seem to challenge this view. We have reanalysed the published data on trachoma in relation to the most relevant indicators of water accessibility, using prevalence ratios as the single parameter for risk assessment. A definite trend emerges from this review: the incidence of infectious conjunctivitis is not sensitive to differences in water accessibility; on the other hand, a reduction in the risk of trachoma is consistently associated with better access to water. This conclusion may support the efforts of WHO and other multilateral and bilateral agencies to sustain the commitment towards the water supply sector beyond the International Drinking Water Supply and Sanitation Decade.  相似文献   
992.
993.
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   
994.
995.
996.
997.
998.
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   
999.
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   
1000.
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   
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