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   39646篇
  免费   2738篇
  国内免费   145篇
耳鼻咽喉   257篇
儿科学   1373篇
妇产科学   915篇
基础医学   4598篇
口腔科学   735篇
临床医学   4143篇
内科学   8367篇
皮肤病学   703篇
神经病学   3945篇
特种医学   1284篇
外科学   6084篇
综合类   636篇
一般理论   60篇
预防医学   3212篇
眼科学   999篇
药学   2796篇
中国医学   41篇
肿瘤学   2381篇
  2023年   124篇
  2022年   203篇
  2021年   599篇
  2020年   377篇
  2019年   634篇
  2018年   758篇
  2017年   598篇
  2016年   609篇
  2015年   786篇
  2014年   1118篇
  2013年   1702篇
  2012年   2606篇
  2011年   2811篇
  2010年   1601篇
  2009年   1457篇
  2008年   2589篇
  2007年   2808篇
  2006年   2756篇
  2005年   2842篇
  2004年   2689篇
  2003年   2479篇
  2002年   2485篇
  2001年   369篇
  2000年   225篇
  1999年   384篇
  1998年   609篇
  1997年   452篇
  1996年   404篇
  1995年   350篇
  1994年   299篇
  1993年   305篇
  1992年   243篇
  1991年   208篇
  1990年   196篇
  1989年   192篇
  1988年   177篇
  1987年   147篇
  1986年   179篇
  1985年   181篇
  1984年   278篇
  1983年   236篇
  1982年   308篇
  1981年   273篇
  1980年   272篇
  1979年   144篇
  1978年   144篇
  1977年   147篇
  1976年   124篇
  1975年   103篇
  1974年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Background

This study used path-analysis to examine the assumption that the presence of mental pain in adults mediates the relationship between self-destruction, number of losses experienced in one’s life, and suicidal tendency.

Methods

Fifty suicidal inpatients, 50 non-suicidal inpatients and 50 healthy volunteers were assessed for self-destruction, losses experienced, depression, suicidal tendency, and mental pain.

Results

Self-destruction was found to have both a direct effect on suicidal tendency as well as one mediated by the presence of mental pain. Number of losses effected suicidal tendency only indirectly, mediated by the presence of mental pain. Overall, self-destruction was a more significant determinant of suicidal tendency than were the number of losses experienced during one’s life. A competing model, with depression replacing mental pain as the mediator, was also found to fit the data.

Discussion

These findings provide evidence that the presence of mental pain is a mediator in the relationships between both self-destruction and number of losses experienced, and between suicidal tendencies. More studies are needed in order to further differentiate between mental pain and depression as mediators in suicidal tendency.  相似文献   
992.
993.
994.
One of the hallmarks of polycystic ovary syndrome (PCOS) is increased ovarian androgen secretion that contributes to the ovarian, hormonal, and metabolic features of this condition. Thecal cells from women with PCOS have an enhanced capacity for androgen synthesis. To investigate whether this propensity is a potential cause, rather than a consequence, of PCOS, we used an ovine prenatal androgenization model of PCOS and assessed ewes at 11 months of age. Pregnant Scottish Greyface ewes were administered 100 mg testosterone propionate (TP) or vehicle control twice weekly from d 62 to 102 of gestation, and female offspring (TP = 9, control = 5) were studied. Prenatal TP exposure did not alter ovarian morphology or cyclicity, or plasma androgen, estrogen, and gonadotropin concentrations, at this stage. However, follicle function was reprogrammed in vivo with increased proportions of estrogenic follicles (P < 0.05) in the TP-exposed cohort. Furthermore, in vitro the thecal cells of follicles (>4 mm) secreted more LH-stimulated androstenedione after prenatal androgenization (P < 0.05), associated with increased basal expression of thecal StAR (P < 0.01), CYP11A (P < 0.05), HSD3B1 (P < 0.01), CYP17 (P < 0.05), and LHR (P < 0.05). This provides the first evidence of increased thecal androgenic capacity in the absence of a PCOS phenotype, suggesting a thecal defect induced during fetal life.  相似文献   
995.
AMP-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis, is present in metabolic tissues (muscle and liver) and has been identified as a modulator of the female reproductive functions. However, its function in the testis has not yet been clearly defined. We have investigated the potential role of AMPK in male reproduction by using transgenic mice lacking the activity of AMPK catalytic subunit α1 gene [α1AMPK knockout (KO)]. In the testis, the α1AMPK subunit is expressed in germ cells and also in somatic cells (Sertoli and Leydig cells). α1AMPK KO male mice show a decrease in fertility, despite no clear alteration in the testis morphology or sperm production. However, in α1AMPK(-/-) mice, we demonstrate that spermatozoa have structural abnormalities and are less motile than in control mice. These spermatozoa alterations are associated with a 50% decrease in mitochondrial activity, a 60% decrease in basal oxygen consumption, and morphological defects. The α1AMPK KO male mice had high androgen levels associated with a 5- and 3-fold increase in intratesticular cholesterol and testosterone concentrations, respectively. High concentrations of proteins involved in steroid production (3β-hydroxysteroid dehydrogenase, cytochrome steroid 17 alpha-hydroxylase/17,20 lysate, and steroidogenic acute regulatory protein) were also detected in α1AMPK(-/-) testes. In the pituitary, the LH and FSH concentrations tended to be lower in α1AMPK(-/-) male mice, probably due to the negative feedback of the high testosterone levels. These results suggest that total α1AMPK deficiency in male mice affects androgen production and quality of spermatozoa, leading to a decrease in fertility.  相似文献   
996.
997.
998.
999.
ObjectivePreclinical and genetic epidemiologic studies suggest that modulating cytochrome P450 (CYP)-mediated arachidonic acid metabolism may have therapeutic utility in the management of coronary artery disease (CAD). However, predictors of inter-individual variation in CYP-derived eicosanoid metabolites in CAD patients have not been evaluated to date. Therefore, the primary objective was to identify clinical factors that influence CYP epoxygenase, soluble epoxide hydrolase (sEH), and CYP ω-hydroxylase metabolism in patients with established CAD.MethodsPlasma levels of epoxyeicosatrienoic acids (EETs), dihydroxyeicosatrienoic acids (DHETs), and 20-hydroxyeicosatetraenoic acid (20-HETE) were quantified by HPLC–MS/MS in a population of patients with stable, angiographically confirmed CAD (N = 82) and healthy volunteers from the local community (N = 36). Predictors of CYP epoxygenase, sEH, and CYP ω-hydroxylase metabolic function were evaluated by regression.ResultsObesity was significantly associated with low plasma EET levels and 14,15-EET:14,15-DHET ratios. Age, diabetes, and cigarette smoking also were significantly associated with CYP epoxygenase and sEH metabolic activity, while only renin-angiotensin system inhibitor use was associated with CYP ω-hydroxylase metabolic activity. Compared to healthy volunteers, both obese and non-obese CAD patients had significantly higher plasma EETs (P < 0.01) and epoxide:diol ratios (P < 0.01), whereas no difference in 20-HETE levels was observed (P = NS).ConclusionsCollectively, these findings suggest that CYP-mediated eicosanoid metabolism is dysregulated in certain subsets of CAD patients, and demonstrate that biomarkers of CYP epoxygenase and sEH, but not CYP ω-hydroxylase, metabolism are altered in stable CAD patients relative to healthy individuals. Future studies are necessary to determine the therapeutic utility of modulating these pathways in patients with CAD.  相似文献   
1000.
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