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   37168篇
  免费   2961篇
  国内免费   95篇
耳鼻咽喉   583篇
儿科学   1492篇
妇产科学   1147篇
基础医学   5218篇
口腔科学   885篇
临床医学   3359篇
内科学   8445篇
皮肤病学   804篇
神经病学   3920篇
特种医学   1130篇
外国民族医学   3篇
外科学   4478篇
综合类   573篇
一般理论   43篇
预防医学   2928篇
眼科学   681篇
药学   2208篇
中国医学   34篇
肿瘤学   2293篇
  2021年   573篇
  2020年   365篇
  2019年   600篇
  2018年   664篇
  2017年   482篇
  2016年   539篇
  2015年   627篇
  2014年   834篇
  2013年   1263篇
  2012年   1669篇
  2011年   1810篇
  2010年   1038篇
  2009年   911篇
  2008年   1604篇
  2007年   1707篇
  2006年   1677篇
  2005年   1601篇
  2004年   1602篇
  2003年   1456篇
  2002年   1506篇
  2001年   1132篇
  2000年   1188篇
  1999年   1021篇
  1998年   428篇
  1997年   362篇
  1996年   377篇
  1995年   335篇
  1994年   325篇
  1993年   336篇
  1992年   882篇
  1991年   821篇
  1990年   700篇
  1989年   743篇
  1988年   691篇
  1987年   722篇
  1986年   659篇
  1985年   685篇
  1984年   556篇
  1983年   477篇
  1982年   317篇
  1980年   278篇
  1979年   467篇
  1978年   317篇
  1977年   262篇
  1976年   284篇
  1975年   268篇
  1974年   298篇
  1973年   299篇
  1972年   270篇
  1971年   262篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The clinical, histopathological, and electron microscopic features of an unusual case of xanthogranulomatous appendicitis are reported. The patient, a 37-year-old female, presented with typical signs of acute appendicitis and the appendix appeared slightly dilated at laparatomy. The histopathological sections showed numerous xanthoma cells mixed with inspissated fecaliths. Electron microscopy disclosed the presence of xanthoma cells filled with electron-lucent lipid droplets of variable size. The ultrastructural characteristics of these cells enabled the distinction of two types of lipid-laden histiocytes, in relationship to the size of the lipid droplets. Since the lipid droplets were seen also in cells other than histiocytes, it appears that these changes are secondary to a common mechanism,comprising factors such as obstruction, hemorrhage, inflammation,and local hypoxia.  相似文献   
992.
To assess the association between RA and chronic obstructive pulmonary disease (COPD) in a population-based case-control study. A cross-sectional analysis performed utilizing the database of Clalit Health Services, the largest healthcare provider organization in Israel. Patients over the age of 20 years who were diagnosed with RA (‘cases’) and who were treated with any anti-rheumatic drug were compared with a sample of age- and gender-matched enrollees (‘controls’) without regard for the prevalence of COPD. Data on health-related lifestyles and other comorbidities were collected. χ2, t tests, and logistic regression models were used to compare the study groups. The study included 9,039 RA cases and 15,070 controls. The proportion of COPD was significantly higher in patients with RA as compared to the control group (8.6 vs. 4.4 %, p < 0.0001, odds ratio (OR) 2.06, 95 % confidence interval (CI) 1.85–2.29). A multivariate logistic regression model demonstrated that RA was significantly associated with COPD, after controlling for confounders, including age, sex, socioeconomic status, smoking, and obesity (adjusted OR 1.98, 95 % CI 1.77–2.21, p < 0.0001). In this large data-based study, RA was found to be associated with COPD.  相似文献   
993.
An increasing body of evidence connects alterations in the process of alternative splicing with cancer development and progression. However, a direct role of splicing factors as drivers of cancer development is mostly unknown. We analysed the gene copy number of several splicing factors in colon and lung tumours, and found that the gene encoding for the splicing factor SRSF6 is amplified and over‐expressed in these cancers. Moreover, over‐expression of SRSF6 in immortal lung epithelial cells enhanced proliferation, protected them from chemotherapy‐induced cell death and converted them to be tumourigenic in mice. In contrast, knock‐down of SRSF6 in lung and colon cancer cell lines inhibited their tumourigenic abilities. SRSF6 up‐ or down‐regulation altered the splicing of several tumour suppressors and oncogenes to generate the oncogenic isoforms and reduce the tumour‐suppressive isoforms. Our data suggest that the splicing factor SRSF6 is an oncoprotein that regulates the proliferation and survival of lung and colon cancer cells.  相似文献   
994.
995.
The present study is the first to assess whether the neural correlates of cognitive control processes differ in adults with and without a behaviorally inhibited temperament during early childhood. Adults with and without childhood behavioral inhibition completed an emotional conflict task while undergoing functional magnetic resonance imaging scanning. While no group differences in behavior were observed, adults with childhood behavioral inhibition, relative to adults without childhood behavioral inhibition, exhibited greater dorsomedial prefrontal cortex activity during conflict detection and greater putamen activity during conflict adaptation. Lifetime psychopathology predicted behavioral, but not brain-related, differences in conflict adaptation. These data suggest that the brain regions underlying cognitive control processes are differentially influenced by childhood behavioral inhibition, and may be differently related to psychopathology.  相似文献   
996.
One of the most promising areas in the therapeutics for metabolic diseases centers around activation of the pathways of energy expenditure. Brown adipose tissue is a particularly appealing target for increasing energy expenditure, given its amazing capacity to transform chemical energy into heat. In addition to classical brown adipose tissue, the last few years have seen great advances in our understanding of inducible thermogenic adipose tissue, also referred to as beige fat. A deeper understanding of the molecular processes involved in the development and function of these cell types may lead to new therapeutics for obesity, diabetes, and other metabolic diseases.  相似文献   
997.
998.
ObjectiveApathy is common in late-life depression and is associated with poor response to antidepressant drugs. In depressed older adults, apathy may be characterized by neuroanatomical abnormalities of the salience network. The current study examined whether cortical thickness of select salience network structures predicted change in apathy following a 12-week treatment with escitalopram.MethodsA sample of 46 older adults with major depressive disorder received 12 weeks of escitalopram treatment at a daily target dose of 20 mg. All participants underwent a structural brain MRI scan at baseline, and cortical thickness was estimated in key cortical nodes of the salience network: the caudal anterior cingulate cortex and the insula. We measured baseline and post-treatment symptoms using the Apathy Evaluation Scale and the Hamilton Depression Rating Scale.ResultsA thicker insula at baseline predicted reduction in apathy symptoms following 12 weeks of treatment with escitalopram, even when controlling for age, baseline depression severity and change in depressive symptoms.ConclusionReduced insular thickness predicted residual apathetic symptoms following escitalopram treatment. These results converge with our previous findings of abnormal functional connectivity of the insular cortex in older depressed individuals with apathy. Older depressed adults with apathy may benefit from alternative treatment approaches or augmentative interventions that target abnormalities of the salience network.  相似文献   
999.
Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that is accompanied by neurodevelopmental differences in regional cortical volume (CV), and a potential layer‐specific pathology. Conventional measures of CV, however, do not indicate how volume is distributed across cortical layers. In a sample of 92 typically developing (TD) controls and 92 adult individuals with ASD (aged 18–52 years), we examined volumetric gradients by quantifying the degree to which CV is weighted from the pial to the white surface of the brain. Overall, the spatial distribution of Frustum Surface Ratio (FSR) followed the gyral and sulcal pattern of the cortex and approximated a bimodal Gaussian distribution caused by a linear mixture of vertices on gyri and sulci. Measures of FSR were highly correlated with vertex‐wise estimates of mean curvature, sulcal depth, and pial surface area, although none of these features explained more than 76% variability in FSR on their own. Moreover, in ASD, we observed a pattern of predominant increases in the degree of FSR relative to TD controls, with an atypical neurodevelopmental trajectory. Our findings suggest a more outward‐weighted gradient of CV in ASD, which may indicate a larger contribution of supragranular layers to regional differences in CV.  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