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   6882篇
  免费   445篇
  国内免费   9篇
耳鼻咽喉   66篇
儿科学   245篇
妇产科学   158篇
基础医学   850篇
口腔科学   77篇
临床医学   930篇
内科学   1278篇
皮肤病学   173篇
神经病学   714篇
特种医学   258篇
外科学   743篇
综合类   28篇
一般理论   4篇
预防医学   778篇
眼科学   66篇
药学   392篇
中国医学   13篇
肿瘤学   563篇
  2024年   8篇
  2023年   65篇
  2022年   102篇
  2021年   197篇
  2020年   153篇
  2019年   213篇
  2018年   257篇
  2017年   212篇
  2016年   166篇
  2015年   198篇
  2014年   258篇
  2013年   388篇
  2012年   589篇
  2011年   596篇
  2010年   310篇
  2009年   293篇
  2008年   505篇
  2007年   470篇
  2006年   461篇
  2005年   417篇
  2004年   391篇
  2003年   342篇
  2002年   305篇
  2001年   41篇
  2000年   24篇
  1999年   40篇
  1998年   67篇
  1997年   51篇
  1996年   33篇
  1995年   21篇
  1994年   24篇
  1993年   25篇
  1992年   9篇
  1991年   20篇
  1990年   7篇
  1989年   10篇
  1988年   3篇
  1987年   3篇
  1986年   4篇
  1985年   9篇
  1984年   5篇
  1983年   4篇
  1982年   8篇
  1981年   10篇
  1980年   4篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1969年   2篇
排序方式: 共有7336条查询结果,搜索用时 15 毫秒
991.

Background  

In Australia in June 2001, a unique pneumococcal vaccine schedule commenced for Indigenous infants; seven-valent pneumococcal conjugate vaccine (7PCV) given at 2, 4, and 6 months of age and 23-valent pneumococcal polysaccharide vaccine (23PPV) at 18 months of age. This study presents carriage serotypes following this schedule.  相似文献   
992.
993.
Building on seminal studies of the last 20 years, genetic testing for hypertrophic cardiomyopathy (HCM) has become a clinical reality in the form of targeted exonic sequencing of known disease-causing genes. This has been driven primarily by the decreasing cost of sequencing, but the high profile of genome-wide association studies, the launch of direct-to-consumer genetic testing, and new legislative protection have also played important roles. In the clinical management of hypertrophic cardiomyopathy, genetic testing is primarily used for family screening. An increasing role is recognized, however, in diagnostic settings: in the differential diagnosis of HCM; in the differentiation of HCM from hypertensive or athlete’s heart; and more rarely in preimplantation genetic diagnosis. Aside from diagnostic clarification and family screening, use of the genetic test for guiding therapy remains controversial, with data currently too limited to derive a reliable mutation risk prediction from within the phenotypic noise of different modifying genomes. Meanwhile, the power of genetic testing derives from the confidence with which a mutation can be called present or absent in a given individual. This confidence contrasts with our more limited ability to judge the significance of mutations for which co-segregation has not been demonstrated. These variants of “unknown” significance represent the greatest challenge to the wider adoption of genetic testing in HCM. Looking forward, next-generation sequencing technologies promise to revolutionize the current approach as whole genome sequencing will soon be available for the cost of today’s targeted panel. In summary, our future will be characterized not by lack of genetic information but by our ability to effectively parse it.  相似文献   
994.
995.

Objective

To study the expression of small ubiquitin‐like modifier 1 (SUMO‐1) in aseptic loosening of prosthesis implants and to investigate its role in regulating the susceptibility of prosthesis‐loosening fibroblast‐like synoviocytes (FLS) to Fas‐induced apoptosis.

Methods

Specimens of aseptically loosened tissue were obtained at revision surgery, and the expression of SUMO‐1 was analyzed by in situ hybridization. SUMO‐1 levels in FLS were determined by quantitative polymerase chain reaction and Western blot analysis. Immunohistochemistry and confocal microscopy were used to study the subcellular localization of SUMO‐1. The functional role of SUMO‐1 in Fas‐induced apoptosis of prosthesis‐loosening FLS was investigated by small interfering RNA–mediated knockdown of SUMO‐1 and by gene transfer of the nuclear SUMO‐specific protease SENP1.

Results

SUMO‐1 was expressed strongly in aseptically loosened tissue and was found prominently at sites adjacent to bone. Prosthesis‐loosening FLS expressed levels of SUMO‐1 similar to the levels expressed by rheumatoid arthritis (RA) FLS, with SUMO‐1 being found mainly in promyelocytic leukemia protein nuclear bodies. Knockdown of SUMO‐1 had no effect on spontaneous apoptosis but significantly increased the susceptibility of prosthesis‐loosening FLS to Fas‐induced apoptosis. Gene transfer of the nuclear SUMO‐specific protease SENP1 reverted the apoptosis‐inhibiting effects of SUMO‐1.

Conclusion

These data suggest that SUMO‐1 is involved in the activation of both RA FLS and prosthesis‐loosening FLS by preventing these cells from undergoing apoptosis. Modification of nuclear proteins by SUMO‐1 contributes to the antiapoptotic effects of SUMO‐1 in prosthesis‐loosening FLS, providing evidence for the specific activation of sumoylation during their differentiation. Therefore, SUMO‐1 may be an interesting target for novel strategies to prevent aseptic prosthesis loosening.
  相似文献   
996.
Mentoring is an important instructional strategy that should be maximally used to develop the next generation of physicians who will care for a growing population of frail older adults. Mentoring can fulfill three specific purposes: (1) help learners choose an area of specialty, (2) help fellows and new faculty navigate advancement in the academic environment, and (3) help new physicians enter a local medical community and develop a high-quality, professionally rewarding, financially viable practice that meets the needs of older adults. The components and process of mentoring are reviewed. Current and potential mechanisms to promote mentoring for the specific purpose of increasing the quality and quantity of physicians available to care for the older adult population are discussed.  相似文献   
997.
998.
Aims   To assess hospitalization rates (HR) for poisoning with heroin, methadone or strong analgesics and relate them to quantities of prescribed methadone and strong analgesics in Denmark between 1998 and 2004.
Design   Population-based ecological study.
Settings   We extracted data on all emergency department visits and hospital admissions registered in the Danish National Patient Registry with a diagnosis of poisoning with heroin ( n  = 1688), methadone ( n  = 173) or strong analgesics ( n  = 384). To ascertain sale of prescribed medications we used data from the Danish Medicines Agency.
Measurements   Age- and gender-standardized HR and defined daily doses (DDD) per 1000 people per day.
Findings   HR for heroin poisoning was 4.4 [95% confidence interval (CI): 3.8–4.9] per 100 000 person-years (p-y) in 1998 and 4.6 (CI: 4.0–5.2) per 100 000 p-y in 2004. HR for methadone poisoning increased from 0.1 (CI: 0.0–0.2) per 100 000 p-y in 1998 to 1.1 (CI: 0.8–1.4) per 100 000 p-y in 2004. HR for poisoning with strong analgesics increased from 0.6 (CI: 0.4–0.9) per 100 000 p-y in 1998 to 2.1 (CI: 1.8–2.6) per 100 000 p-y in 2004. The sale of prescribed strong analgesics (5.0 DDD per 1000 people per day in 1998 to 5.9 DDD in 2004) and methadone (3.0 DDD per 1000 people per day in 1998 to 3.4 DDD in 2004) increased slightly between 1998 and 2004.
Conclusion   Increasing sale of prescribed methadone and strong analgesics coincided with increasing HRs of poisoning with these drugs, whereas HR of heroin poisoning varied. Further longitudinal studies are important for the guidance of future policy making.  相似文献   
999.
The objectives of this study were: systematic investigation of dry powder aerosol performance using standardized entrainment tubes (SETs) and lactose-based formulations with two model drugs; mechanistic evaluation of performance data by powder aerosol deaggregation equation (PADE). The drugs (IPB and FP) were prepared in sieved and milled lactose carriers (2% w/w). Aerosol studies were performed using SETs (shear stresses τs = 0.624-13.143 N/m2) by twin-stage liquid impinger, operated at 60 L/min. PADE was applied for formulation screening. Excellent correlation was observed when PADE was adopted correlating FPF to τs. Higher τs corresponded to higher FPF values followed by a plateau representing invariance of FPF with increasing τs. The R2 values for PADE linear regression were 0.9905-0.9999. Performance described in terms of the maximum FPF (FPFmax: 15.0–37.6%) resulted in a rank order of ML-B/IPB > ML-A/IPB > SV-A/IPB > SV-B/IPB > ML-B/FP > ML-A/FP > SV-B/FP > SV-A/FP. The performance of IPB was superior to FP in all formulations. The difference in lactose monohydrate carriers was less pronounced for the FPF in IPB than in FP formulations. The novel PADE offers a robust method for evaluating aerodynamic performance of dry powder formulations within a defined τs range.  相似文献   
1000.
Although excessive alcohol consumption is known to elevate the mean cell volume (MCV) of erythrocytes, the relationships among the intensity of ethanol exposure, the generation of abnormal red blood cell indices, and the underlying pathogenic mechanisms have remained unclear. The authors examined 105 alcoholics with a wide range of ethanol consumption (40-500 g of ethanol/day), 62 moderate drinkers (mean consumption 1-40 g/day), and 24 abstainers, who underwent detailed interviews, measurements of blood cell counts, markers of liver status, and circulating antibodies against ethanol-derived protein modifications. Follow-up information was collected from healthy volunteers with detailed records on drinking habits. Data from the NORIP project for laboratory parameters in apparently healthy moderate drinkers or abstainers (n = 845) were used for reference interval comparisons. The highest MCV (P < 0.001) and mean cell hemoglobin (MCH) (P < 0.01) occurred in the alcoholics. However, the values in the moderate drinkers also responded to ethanol intake such that the upper normal limit for MCV based on the data from moderate drinkers was 98 fl, as compared with 96 fl from abstainers. Follow-up cases with carefully registered drinking habits showed parallel changes in MCV and ethanol intake. Anti-adduct IgA and IgM against acetaldehyde-induced protein modifications were elevated in 94% and 64% of patients with high MCV, respectively, the former being significantly less frequent in the alcoholics with normal MCV (63%) (P < 0.05). The data indicate dose-related responses in red blood indices upon chronic ethanol consumption, which may also be reflected in reference intervals for hematological parameters in health care. Generation of immune responses against acetaldehyde-modified erythrocyte proteins may be associated with the appearance of such abnormalities.  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