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   30033篇
  免费   1796篇
  国内免费   112篇
耳鼻咽喉   399篇
儿科学   694篇
妇产科学   795篇
基础医学   3786篇
口腔科学   1696篇
临床医学   2294篇
内科学   7681篇
皮肤病学   727篇
神经病学   2473篇
特种医学   739篇
外科学   3992篇
综合类   152篇
一般理论   6篇
预防医学   2701篇
眼科学   452篇
药学   1830篇
中国医学   196篇
肿瘤学   1328篇
  2023年   265篇
  2022年   553篇
  2021年   1168篇
  2020年   671篇
  2019年   970篇
  2018年   1259篇
  2017年   771篇
  2016年   802篇
  2015年   932篇
  2014年   1358篇
  2013年   1571篇
  2012年   2336篇
  2011年   2526篇
  2010年   1336篇
  2009年   1119篇
  2008年   1888篇
  2007年   1803篇
  2006年   1595篇
  2005年   1583篇
  2004年   1379篇
  2003年   1149篇
  2002年   1073篇
  2001年   410篇
  2000年   424篇
  1999年   383篇
  1998年   197篇
  1997年   142篇
  1996年   138篇
  1995年   117篇
  1994年   102篇
  1993年   87篇
  1992年   173篇
  1991年   152篇
  1990年   144篇
  1989年   131篇
  1988年   107篇
  1987年   104篇
  1986年   101篇
  1985年   99篇
  1984年   83篇
  1983年   70篇
  1982年   50篇
  1981年   37篇
  1980年   44篇
  1979年   46篇
  1978年   40篇
  1975年   37篇
  1974年   41篇
  1973年   54篇
  1971年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Vitamin K was quantitated in the milk of four groups of 15 mothers from 1 d to 6 mo postpartum in a cross-sectional study. Concentrations were 7.52 +/- 5.90 and 6.36 +/- 5.32 nmol/L (3.39 +/- 2.66 and 2.87 +/- 2.40 micrograms/L) in colostrum and mature milk, respectively. Differences between colostrum and mature milk or among samples of mature milk collected at 1, 3, and 6 mo were not statistically significant. Because of significantly increased volumes of milk over the lactation period, approximately twice as much vitamin K was delivered in mature milk as in colostrum. Within normal ranges, concentrations of vitamin K in milk were not predicted by dietary intake of vegetables or fat. Vitamin K was correlated with fat in colostrum and was localized in the lipid core of the milk fat globule but was not associated with membranes. Vitamin K in human milk is insufficient to meet recommended intakes for infants aged less than 6 mo. Population and clinical studies are needed to assess the vitamin K status of exclusively breast-fed infants and to evaluate current recommendations.  相似文献   
42.
The health care supervisor responsible for establishing a therapeutic milieu within a traditional hospital organization will have greater success if these suggested management strategies are employed. Decentralizing, improving organizational communication, and clarifying interdisciplinary role relationships are the strategies that support the integration of differing organizational approaches to management.  相似文献   
43.
44.
Colorectal cancer is one of the best studied of all malignant diseases interms of genetics and/or molecular prognostic factors. These factors, and relationships with prognosis, may have important implications especially in the design of surgical and adjuvant chemo-radiotherapy options. However, the true prognostic significance of all known factors has yet to be realised. We have reviewed the literature with specific focus on the role of molecular markers involved in prognosis and the prediction of response to adjuvant treatment.  相似文献   
45.
46.
The effect of a two day fast on maternal plasma volume and plasma protein concentration was explored in pregnant rats. Fasting between days 17 and 19 of gestation prevented the rise in plasma volume observed in ad libitum fed rats. Plasma protein concentration declined between day 17 and day 19 in both fasted and not fasted rats. Placental weight was not reduced by fasting during this stage of gestation. Fetal weight in the fasted group was 91% of the fetal weight of the ad libitum fed group. These results show that acute undernutrition, like longer term food or protein restriction, can prevent adequate plasma volume expansion and slow fetal growth.  相似文献   
47.
48.
Percutaneous embolization of large portosystemic collaterals was performed in three patients following placement of a transjugular intrahepatic portosystemic shunt in order to improve hepatopetal portal flow. Improved hepatic portal perfusion was achieved in these cases, thereby theoretically reducing the risk of chronic hepatic encephalopathy.  相似文献   
49.
Purpose: Increasingly, evidence has shown that human papillomavirus (HPV) plays a role in the induction of certain carcinomas. The presence of HPV sequences in 56 previously untreated oral and pharyngolaryngeal carcinomas was examined by the polymerase chain reaction (PCR).Materials and Methods: After DNA extraction, samples underwent 40 replication cycles with specific oligonucleotide primers corresponding to sequences from the E6 open-reading frame of HPV-6b, HPV-16, and HPV-18. To determine the E6 genomic integration, positive samples were processed with specific primers for the corresponding HPV L1 genes. Genomic HPV DNA cloned into PBR 322 was used as positive control.Results: HPV E6 DNA of the 6b and 16 types was detected in 14 patients (25%). The L1 gene was not present.Conclusion: Detected HPV E6 DNA might be integrated into the cell genome in the positive cases as indicated by the absence of the L1 gene-coding for the viral capside. Histological and clinical parameters, such as tumor location, degree of differentiation, stage, recurrence, and survival rates, were unrelated to the presence of HPV.  相似文献   
50.
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