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   52290篇
  免费   3871篇
  国内免费   205篇
耳鼻咽喉   662篇
儿科学   1117篇
妇产科学   1019篇
基础医学   7276篇
口腔科学   1233篇
临床医学   5127篇
内科学   10797篇
皮肤病学   1168篇
神经病学   5108篇
特种医学   2178篇
外国民族医学   2篇
外科学   9316篇
综合类   501篇
一般理论   77篇
预防医学   3011篇
眼科学   1085篇
药学   3044篇
中国医学   79篇
肿瘤学   3566篇
  2023年   455篇
  2022年   805篇
  2021年   1818篇
  2020年   1098篇
  2019年   1441篇
  2018年   1643篇
  2017年   1093篇
  2016年   1329篇
  2015年   1503篇
  2014年   2024篇
  2013年   2406篇
  2012年   3852篇
  2011年   3784篇
  2010年   2123篇
  2009年   1892篇
  2008年   3063篇
  2007年   3095篇
  2006年   2919篇
  2005年   2694篇
  2004年   2497篇
  2003年   2310篇
  2002年   2123篇
  2001年   602篇
  2000年   603篇
  1999年   613篇
  1998年   501篇
  1997年   384篇
  1996年   298篇
  1995年   290篇
  1994年   253篇
  1993年   258篇
  1992年   404篇
  1991年   370篇
  1990年   343篇
  1989年   321篇
  1988年   290篇
  1987年   268篇
  1986年   272篇
  1985年   298篇
  1984年   245篇
  1983年   229篇
  1982年   190篇
  1981年   174篇
  1980年   180篇
  1979年   205篇
  1978年   175篇
  1977年   146篇
  1976年   143篇
  1974年   153篇
  1972年   124篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
51.
Age-related bone loss has been associated with high levels of marrow adipogenesis. Estrogens (E2) are known to regulate the differentiation of marrow precursors into osteoblasts, however, their role in bone marrow adipogenesis remain unknown. E2 regulate adipocyte differentiation in subcutaneous and visceral fat through interaction with other nuclear receptors. This interaction has not been assessed in bone marrow adipocytes in vivo. In this study, we compared two groups of animals, young and old, after either oophorectomy (OVX) or oophorectomy plus E2 (OVX + E2) replacement. We found that absence of E2 was associated with higher levels of PPARγ and lower levels of Sirt1 most significantly in the old group. In addition, old mice responded better to E2 replacement in terms of reducing adipogenesis and PPARγ expression as well as increasing levels of Sirt1 expression. Our findings represent a new understanding of the role of E2 in age-related bone loss, which could be mediated through the regulation of Sirt1 expression within the bone marrow. In addition, this evidence suggests that old individuals may show a better response to E2 administration in terms of reverting the high levels of marrow fat seen in age-related bone loss.  相似文献   
52.
53.
The aim of this study was to evaluate a case-mix system to classify inpatients with mental disorders in Germany by means of self-report and expert-rated instruments. The use of case-mix systems enhances the transparency of performance and cost structure and can thus improve the quality of mental health care. We analysed a consecutive sample of 1677 inpatients with mental disorders from 11 hospitals using regression tree analysis. The model assigns patients to 17 groups, accounting for 17% of the variance for duration of stay. Patients with eating disorders had a longer duration of stay than patients with anxiety disorder, duration of mental illness of less than 3–5 years, lower levels of interpersonal problems and higher occupational position. The results showed that besides diagnosis, variables such as duration of illness and interpersonal problems are important for classifying inpatients with mental disorders. The results of the study should be critically reviewed regarding the empirical results of other studies and the appropriateness of case group concepts for inpatients with mental disorders.  相似文献   
54.
55.
BACKGROUND: Results from studies in serotonin-1A (5-HT1A) knockout mice and previous positron emission tomography (PET) studies in humans imply a role for 5-HT1A receptors in normal state anxiety as well as in certain anxiety disorders. The objective of this study was to investigate 5-HT1A receptor binding potential (BP) in social anxiety disorder (SAD). METHODS: Using PET and [carbonyl-11C]WAY-100635, we compared a homogeneous group of 12 unmedicated, male SAD patients with 18 healthy control subjects (HC). A multivariate ANOVA with all regional BP values as dependent variables, age and four radiochemical variables as covariates was performed. RESULTS: We found a significantly lower 5-HT1A BP in several limbic and paralimbic areas but not in the hippocampus (p = .234) of SAD patients. The difference in 5-HT1A binding was most significant in the amygdala (-21.4%; p = .003). There was also a more than 20% lower 5-HT(1A) BP of SAD patients in the anterior cingulate cortex (p = .004), insula (p = .003), and dorsal raphe nuclei (p = .030). CONCLUSIONS: The lower 5-HT1A binding in the amygdala and mesiofrontal areas of SAD patients is consistent with 1) preclinical findings of elevated anxiety in 5-HT1A knockout mice, 2) a previous PET study in healthy volunteers showing an inverse correlation between 5-HT1A BP and state anxiety, and 3) another human PET study in patients with panic disorder showing reduced 5-HT1A binding, thus corroborating the potential validity of 5-HT1A receptors as targets in the treatment of human anxiety disorders.  相似文献   
56.
57.
The production of progesterone from pregnenolone, of cortisol from cortisone and of prostaglandin E (PGE) under basal and arachidonic acid-stimulated conditions was measured in cells dispersed from chorion and decidua. The cells were obtained after delivery from four groups of women: following spontaneous labour at term (38-42 weeks gestation), at elective caesarean section at term before the onset of labour, after induced labour at term, and after uncomplicated preterm (27-36 weeks) labour. Chorionic cells had a high progesterone output with relatively low cortisol and PGE production, whereas decidual cells had a high cortisol and PGE production rate. Free arachidonic acid stimulated PGE production in both decidual and chorionic cells. There were no significant differences in either steroid or PGE production among the four groups studied. These data suggest that steroid dehydrogenase activity in choriodecidual cells is not related to the mode of onset of labour and that the increased prostaglandin production in intrauterine tissues associated with parturition is due to enhanced availability of arachidonic acid.  相似文献   
58.
59.
Eighty-eight of 143 hospitals in New York State providing psychiatric inpatient treatment responded to a mailed questionnaire designed to determine the size of three subgroups of chemical abusers--alcohol abusers, drug abusers, and polychemical abusers--among inpatients with psychiatric diagnoses, as well as the availability of services for these patients. Data for New York City and its metropolitan area were analyzed separately. In 1987 almost one-third of psychiatric admissions both in and outside the metropolitan area had comorbid chemical abuse disorders. Seventy-five percent of patients in the metropolitan area with comorbid chemical abuse had a drug abuse disorder; in rural areas 88 percent of patients with chemical abuse disorders abused alcohol. Both hospital- and community-based aftercare services, especially in the metropolitan area, were less available to psychiatric patients with chemical abuse than to patients without these disorders.  相似文献   
60.
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