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   3433篇
  免费   277篇
  国内免费   19篇
耳鼻咽喉   11篇
儿科学   76篇
妇产科学   64篇
基础医学   550篇
口腔科学   30篇
临床医学   420篇
内科学   892篇
皮肤病学   31篇
神经病学   275篇
特种医学   61篇
外国民族医学   1篇
外科学   418篇
综合类   67篇
一般理论   8篇
预防医学   274篇
眼科学   53篇
药学   247篇
中国医学   23篇
肿瘤学   228篇
  2023年   28篇
  2022年   56篇
  2021年   115篇
  2020年   64篇
  2019年   87篇
  2018年   87篇
  2017年   68篇
  2016年   74篇
  2015年   87篇
  2014年   87篇
  2013年   149篇
  2012年   248篇
  2011年   269篇
  2010年   137篇
  2009年   120篇
  2008年   187篇
  2007年   217篇
  2006年   177篇
  2005年   159篇
  2004年   153篇
  2003年   124篇
  2002年   127篇
  2001年   103篇
  2000年   105篇
  1999年   60篇
  1998年   43篇
  1997年   45篇
  1996年   33篇
  1995年   16篇
  1994年   20篇
  1993年   27篇
  1992年   58篇
  1991年   44篇
  1990年   46篇
  1989年   33篇
  1988年   41篇
  1987年   28篇
  1986年   27篇
  1985年   27篇
  1984年   17篇
  1983年   19篇
  1982年   20篇
  1981年   10篇
  1980年   11篇
  1979年   16篇
  1978年   9篇
  1976年   7篇
  1975年   5篇
  1974年   8篇
  1970年   5篇
排序方式: 共有3729条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Purpose : To evaluate the sex ratio in births conceived with blastocyst transfer compared to day 3-ET. Methods : A retrospective analysis of IVF patients who became pregnant after blastocyst or cleavage stage transfer at Stanford University Hospital and a literature review were performed. Result(s) : In the day 3-ET group, the male-to-female (M/F) ratio was 157/139 (53%/47%) compared to 97/66 (59.5%/40.5%) in the blastocyst group (P = 0.18). Similar trends have been found in individual studies in the literature but reached statistical significance in only one out of six reports reviewed. The combined data from our study and the literature show a male-to-female ratio of 797/594 (57.3%/42.7%) in blastocyst transfer compared to 977/932 (51.2%/48.8%) in day 3-ET (P = 0.001). Conclusion(s) : Although individual studies may lack power to show an altered sex ratio with blastocyst transfer, the combined data presented in this report do suggest that the M/F ratio is higher with blastocyst transfer compared to cleavage stage transfer.  相似文献   
995.
OBJECTIVE: To evaluate the incidence of monozygotic twinning (MZT) in pregnancies conceived after blastocyst transfer compared to cleavage-stage transfer. DESIGN: Retrospective study. SETTING: University IVF program. PATIENT(S): All IVF patients with viable pregnancies conceived during a 4-year period. INTERVENTION(S): Blastocyst transfer or day 3 ET. MAIN OUTCOME MEASURE(S): Incidence of MZT assessed by transvaginal ultrasound. RESULT(S): There were 11 incidences of MZT in 197 viable pregnancies (5.6%) with blastocyst transfer compared to 7 of 357 viable pregnancies (2%) with day 3 ET. In 10 of 18 pregnancies, MZT was observed in the setting of a higher order multiple gestation (6 of 11 for blastocyst transfer and 4 of 7 for day 3 ET). In the day 3 ET group, assisted hatching or intracytoplasmic sperm injection (ICSI) did not increase MZT (4 of 213, 1.9%) compared to cycles without zona breaching (3 of 144, 2.1%). Similarly, in the blastocyst-transfer group, ICSI did not increase the incidence of MZT (4 of 74, 5.5% for ICSI and 7 of 123, 5.7% for non-ICSI IVF). CONCLUSION(S): Compared to day 3 ET, blastocyst transfer appears to significantly increase the incidence of gestations with MZT. This information should be taken into account when counseling patients about the pros and cons of extended culture.  相似文献   
996.
In the present study, the hepatoprotective effect of metformin (Met), a dimethylbiguanide anti-hyperglycemic, was examined in a mouse model of liver damage induced by chronic repeated administration of carbon tetrachloride (CCl(4)) (5 microl/kg, twice a week for 12 weeks). Met, when given orally in drinking water at an estimated daily dose of 25 or 50 mg/kg for 10 weeks starting 2 weeks after CCl(4) challenge, protected against CCl(4) hepatotoxicity. The results indicate that the hepatoprotection afforded by Met treatment at a dose of 25 mg/kg against CCl(4) toxicity may at least in part be mediated by the enhancement of mitochondrial glutathione redox status.  相似文献   
997.
998.
Liver transplantation for hepatocellular carcinoma: an Asian perspective   总被引:8,自引:0,他引:8  
Liver transplantation is an established treatment modality for patients with hepatocellular carcinoma (HCC), creating a potential for disease-free, long-term survival. In Asia, due to a severe shortage of donors, resection remains the treatment of choice for patients with HCC and good liver functional reserve. The use of marginal donors, split liver grafts and grafts from living donors are potential solutions that are best performed in experienced liver transplant centres to ensure an optimal outcome. Ethical issues relating to living donor liver transplantation have yet to be fully addressed. The roles of therapies to limit tumour progression during the waiting period, such as transarterial chemoembolization, need to be further investigated in the setting of a prospective trial and their benefits better defined.  相似文献   
999.
1000.
In April 1999, isolation of avian influenza A (H9N2) viruses from humans was confirmed for the first time. H9N2 viruses were isolated from nasopharyngeal aspirate specimens collected from two children who were hospitalized with uncomplicated, febrile, upper respiratory tract illnesses in Hong Kong during March 1999. Novel influenza viruses have the potential to initiate global pandemics if they are sufficiently transmissible among humans. We conducted four retrospective cohort studies of persons exposed to these two H9N2 patients to assess whether human-to-human transmission of avian H9N2 viruses had occurred. No serologic evidence of H9N2 infection was found in family members or health-care workers who had close contact with the H9N2-infected children, suggesting that these H9N2 viruses were not easily transmitted from person to person.  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