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   13984篇
  免费   1314篇
  国内免费   40篇
耳鼻咽喉   165篇
儿科学   441篇
妇产科学   422篇
基础医学   1915篇
口腔科学   232篇
临床医学   1885篇
内科学   2561篇
皮肤病学   221篇
神经病学   1398篇
特种医学   627篇
外国民族医学   1篇
外科学   1642篇
综合类   289篇
一般理论   12篇
预防医学   1467篇
眼科学   323篇
药学   890篇
中国医学   19篇
肿瘤学   828篇
  2022年   108篇
  2021年   241篇
  2020年   174篇
  2019年   219篇
  2018年   308篇
  2017年   232篇
  2016年   248篇
  2015年   252篇
  2014年   388篇
  2013年   566篇
  2012年   715篇
  2011年   691篇
  2010年   392篇
  2009年   389篇
  2008年   622篇
  2007年   618篇
  2006年   643篇
  2005年   639篇
  2004年   546篇
  2003年   526篇
  2002年   503篇
  2001年   345篇
  2000年   337篇
  1999年   325篇
  1998年   180篇
  1997年   172篇
  1996年   138篇
  1995年   128篇
  1994年   149篇
  1993年   111篇
  1992年   254篇
  1991年   254篇
  1990年   244篇
  1989年   227篇
  1988年   247篇
  1987年   237篇
  1986年   250篇
  1985年   209篇
  1984年   185篇
  1983年   180篇
  1982年   130篇
  1981年   144篇
  1980年   103篇
  1979年   184篇
  1978年   138篇
  1977年   107篇
  1976年   129篇
  1975年   127篇
  1974年   128篇
  1973年   94篇
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
951.
952.
Our paper analyzes technical efficiency in the production of aggregate health outcomes of reduced infant mortality and increased life expectancy, using Organization for Economic Cooperation and Development (OECD) health data. Application of data envelopment analysis (DEA) reveals that some countries achieve relative efficiency advantages, including those with good health outcomes (Japan, Sweden, Norway, and Canada) and those with modest health outcomes (Mexico and Turkey). We conclude the USA may learn from countries more economical in their allocation of healthcare resources that more is not necessarily better. Specifically, we find that the USA can substantially reduce inputs while maintaining the current level of life expectancy.  相似文献   
953.
954.
We compared the power of gene expression measurements with that of conventional prognostic markers, i.e., clinical, histopathological, and cell biological parameters, for predicting distant metastases in breast cancer patients using both established prognostic indices (e.g., the Nottingham Prognostic Index (NPI)) and novel combinations of conventional markers. We used publicly available data on 97 patients, and the performance of metastasis prediction was represented by receiver operating characteristic (ROC) areas and Kaplan-Meier plots. The gene expression profiler did not perform noticeably better than indices constructed from the clinical variables, e.g., the well established NPI. When analysing separately subgroups, according to the oestrogen receptor (ER) status both approaches could predict clinical outcome more easily for the ER-positive than for the ER-negative cohort. Given the time it may take before microarray processing is used worldwide, particularly due to the costs and the lack of standards, it is important to pursue research using conventional markers. Our analysis suggests that it might be possible to improve the combination of different conventional prognostic markers into one prognostic index.  相似文献   
955.
956.
BACKGROUND: Antibody responses to pneumococcal conjugate vaccines may vary when administered in different populations or epidemiologic settings. Understanding the causes and significance of this variation could help to determine the number of doses and timing required for protection against pneumococcal diseases in each country. METHODS: This report compares antibody responses to aluminum-adjuvanted and nonadjuvanted mixed carrier 11-valent diphtheria- or tetanus-conjugated pneumococcal vaccine (11-PncTD) formulations when given at 6, 10 and 14 weeks and 9 months of age to Filipino infants (n = 51) and at 2, 4, 6 and 12 months of age to Finnish (n = 127) and Israeli (n = 124) infants. The study populations differ in their natural exposure to pneumococcus and risk factors for pneumococcal carriage and disease. RESULTS: Filipino and Israeli infants had slightly but significantly higher prevaccination geometric mean concentration (GMC) of antibodies than did the Finnish infants. After three doses of aluminum-adjuvanted 11-PncTD vaccine, the Filipino infants had 1.8 to 6.7 and 1.5 to 5.0 times higher GMC than the Finnish and Israeli infants, respectively, against pneumococcal serotypes conjugated to tetanus protein. The GMC of serotypes conjugated to diphtheria toxoid was 1.3 to 3.0 and 0.7 to 2.0 times the GMC in Finnish and Israeli infants, respectively. The nonadjuvanted vaccine formulation induced generally lower GMCs. CONCLUSIONS: The antibody responses to the tetanus-conjugated polysaccharides were considerably higher in the Filipino than in the Finnish or Israeli infants. This may be a result of several factors including the priming effect of tetanus toxoid given to pregnant women, early pneumococcal nasopharyngeal acquisition and genetic differences among populations.  相似文献   
957.
958.
Regenerative processes enhance postsynaptic potential (PSP) amplitude and behaviorally relevant temporal filtering in more than one-third of electrosensory neurons in the torus semicircularis of Eigenmannia. Data from in vivo current-clamp intracellular recordings indicate that these "regenerative PSPs" can be divided in two groups based on their half-amplitude durations: constant duration (CD) and variable duration (VD) PSPs. CD PSPs have half-amplitude durations of between 20 and 60 ms that do not vary in relation to stimulus periodicity. In contrast, the half-amplitude durations of VD PSPs vary in relation to stimulus periodicity and range from approximately 10 to 500 ms. Injection of 0.1 nA sinusoidal current through the recording electrode demonstrated that CD PSPs and not VD PSPs can be elicited by voltage fluctuations alone. In addition, CD PSPs were blocked by intracellular application of either QX-314 or QX-222, whereas VD PSPs were not. These in vivo data suggest, therefore, that CD PSPs are mediated by voltage-dependent Na+ conductances.  相似文献   
959.
While the androgens, including dihydrotestosterone (DHT), have been implicated in the development of androgenetic alopecia (AGA), the exact mechanism by which they exert their effect(s) is unknown. Since apoptosis is an integral component of the normal cycling of human hair, we investigated individuals clinically affected by AGA to assess whether objective differences in the expression of apoptosis-related immunohistochemical markers could be observed in scalp biopsies. Specimens from 16 alopecic male patients were stained with bd-2 and the terminal deoxynucleotidyltransferase dUTP fluorescein nick end-labeling (TUNEL) method was used to assess apoptotic activity in affected and unaffected areas ofthe scalp. Immunoreactivity was analyzed by quantifying staining differences within the same individual. Sections from 3 human volunteers were used to establish the method validity. Significant differences in the bcl-2 staining index (0.67 versus 0.42, p < 0.05) and TUNEL expression (5.7 versus 10.2, p < 0.05) were observed between the areas of the scalp that were clinically affected (frontal) and unaffected (occipital) by AGA. The Gaussian distributions of bcl-2 and TUNEL staining suggest that a relatively uniform population of follicles exists at the frontal hairline and/or that synchrony of follicular cycling occurs in AGA. The apoptosis "hot spot" revealed by TUNEL staining in the bulge-isthmus region of the murine follicle is also identifiable in the human follicle.  相似文献   
960.
Retinoids influence the pathogenesis of alcohol liver disease (ALD). To analyze the impact of retinoid X receptor alpha (RXRalpha) on ALD, alcohol-induced hepatotoxicity was studied using mice fed ethanol intragastrically for 25 days. Alcohol-induced microvesicular fat around the central vein and drug-induced morphological changes (loss of rough endoplasmic reticulum, pinkish cytoplasm, and enlarged hepatocyte) in the pericentral area were observed in the liver of wild-type mice. In the hepatocyte RXRalpha-deficient mouse liver, alcohol induced fat accumulation, mitosis, acute inflammation, and necrosis. The histology score after alcohol treatment was significantly higher in mutant mice than in wild-type mice. However, drug-induced morphological changes were not apparent in alcohol-treated hepatocyte RXRalpha-deficient mice. Northern analysis showed that the basal and alcohol-induced CYP2B, CYP2A, and CYP3A mRNA levels were lower in hepatocyte RXRalpha-deficient mice than in wild-type mice, which in turn may protect mutant mice from morphological changes. Compared with wild-type mice, hepatocyte RXRalpha-deficient mice have significant lower levels of S-adenosylmethionine and glutathione, which is further reduced after alcohol treatment, and that may account for severe liver injury induced by alcohol. The overall result suggests an important role of RXRalpha in preventing alcohol-induced liver injury.  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