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   1339661篇
  免费   112796篇
  国内免费   6359篇
耳鼻咽喉   16737篇
儿科学   43016篇
妇产科学   36554篇
基础医学   183702篇
口腔科学   36290篇
临床医学   120818篇
内科学   278922篇
皮肤病学   31901篇
神经病学   110643篇
特种医学   55550篇
外国民族医学   274篇
外科学   210403篇
综合类   31537篇
现状与发展   2篇
一般理论   414篇
预防医学   106672篇
眼科学   28106篇
药学   94043篇
  24篇
中国医学   2232篇
肿瘤学   70976篇
  2018年   13378篇
  2017年   10631篇
  2016年   12804篇
  2015年   14303篇
  2014年   19947篇
  2013年   29733篇
  2012年   36233篇
  2011年   38883篇
  2010年   24370篇
  2009年   23901篇
  2008年   36363篇
  2007年   38775篇
  2006年   39904篇
  2005年   38495篇
  2004年   36733篇
  2003年   35826篇
  2002年   33831篇
  2001年   66052篇
  2000年   67916篇
  1999年   56587篇
  1998年   16724篇
  1997年   15018篇
  1996年   16014篇
  1995年   16232篇
  1994年   15098篇
  1993年   14153篇
  1992年   47098篇
  1991年   45747篇
  1990年   43970篇
  1989年   41815篇
  1988年   38758篇
  1987年   38081篇
  1986年   35859篇
  1985年   34635篇
  1984年   26358篇
  1983年   22108篇
  1982年   13847篇
  1981年   12447篇
  1980年   11718篇
  1979年   23544篇
  1978年   17072篇
  1977年   14385篇
  1976年   13182篇
  1975年   13722篇
  1974年   16093篇
  1973年   15396篇
  1972年   14173篇
  1971年   13036篇
  1970年   11880篇
  1969年   11101篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
BackgroundFluoroquinolones are a popular alternative to trimethoprim-sulfamethoxazole for Stenotrophomonas maltophilia infections.ObjectivesTo compare the effects of fluoroquinolones and trimethoprim-sulfamethoxazole on mortality of S. maltophilia infections.Data sourcesPubMed and EMBASE.Study eligibility criteriaClinical studies reporting mortality outcomes of S. maltophilia infections.ParticipantsPatients with clinical infections caused by S. maltophilia.InterventionsFluoroquinolone monotherapy in comparison with trimethoprim-sulfamethoxazole monotherapy.MethodsSystematic review with meta-analysis technique.ResultsSeven retrospective cohort and seven case–control studies were included. Three cohort studies were designed to compare the two drugs, whereas others had other purposes. A total of 663 patients were identified, 332 of which were treated with trimethoprim-sulfamethoxazole (50.1%) and 331 with fluoroquinolones (49.9%). Three cohort studies were designed to compare the effect of the two drugs, whereas the others had other purposes. Levofloxacin was most frequently used among fluoroquinolones (187/331, 56.5%), followed by ciprofloxacin (114/331, 34.4%). The overall mortality rate was 29.6%. Using pooled ORs for the mortality of each study, fluoroquinolone treatment (OR 0.62, 95% CI 0.39–0.99) was associated with survival benefit over trimethoprim-sulfamethoxazole treatment, with low heterogeneity (I2 = 18%). Specific fluoroquinolones such as ciprofloxacin (OR 0.44, 95% CI 0.17–1.12) and levofloxacin (OR 0.78, 95% CI 0.48–1.26) did not show a significant difference in comparison with trimethoprim-sulfamethoxazole. In the sub-group analyses of adult and bacteraemic patients, significant differences in mortality were not observed between fluoroquinolones and trimethoprim-sulfamethoxazole.ConclusionsBased on a meta-analysis of non-randomized studies, fluoroquinolones demonstrated comparable effects on mortality of S. maltophilia infection to trimethoprim-sulfamethoxazole, supporting the use of fluoroquinolones in clinical S. maltophilia infections. Although the pooled analysis of overall studies favoured fluoroquinolones over trimethoprim-sulfamethoxazole, the studies included were observational, and sub-group analyses of certain fluoroquinolone agents did not show statistical differences with trimethoprim-sulfamethoxazole. Randomized clinical studies are needed to address these issues.  相似文献   
142.
ObjectivesStaphylococcus argenteus has been increasingly reported since the species was defined as a novel staphylococcal species in 2015. This study aims to investigate genetic epidemiological links and antimicrobial susceptibilities of methicillin-resistant S. argenteus isolates recovered in Stockholm.MethodsSixteen methicillin-resistant S. argenteus isolates were identified from a collection of methicillin-resistant Staphylococcus aureus in Stockholm 2007–2018, by using whole-genome sequencing and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The genomes of the isolates were investigated by pulsed-field gel electrophoresis, single-nucleotide polymorphism (SNP)-based phylogeny, k-mer analysis, core-genome multi-locus sequence typing (cgMLST), resistance traits and virulence factors. The MICs of 19 antimicrobial agents for each isolate were determined by using the broth microdilution method.ResultsOf the 16 isolates, seven, seven and two isolates were assigned to ST1223, ST2250 and ST2793, respectively, with the S. aureus MLST-scheme. Analyses based on SNPs and cgMLST revealed a likely clonal spread of methicillin-resistant S. argenteus in 2007. Four isolates were found to be resistant to non-β-lactams in antimicrobial susceptibility testing.ConclusionsA transmission event of methicillin-resistant S. argenteus in family was identified by this study. Among our limited number of isolates, non-β-lactam resistance was detected, which highlights the necessity of a continued surveillance on this emerging pathogen. S. argenteus could be correctly identified by MALDI-TOF MS with the updated database, enabling its detection also in clinical laboratories.  相似文献   
143.
Journal of Artificial Organs - A frequent complication of left ventricular assist devices (LVAD) is the LVAD-associated infections (LVADIs). Contamination may occur during initial surgery/admission...  相似文献   
144.
145.
146.
ObjectivesNon-cystic fibrosis bronchiectasis (NCFBE) with Pseudomonas aeruginosa has been associated with increased pulmonary exacerbation (PEx) and mortality risk. European Respiratory Society guidelines conditionally recommend inhaled antimicrobials for persons with NCFBE, P aeruginosa and three or more PEx/year. We report microbiological results of two randomized, 48-week placebo-controlled trials of ARD-3150 (inhaled liposomal ciprofloxacin) in individuals with NCFBE with P aeruginosa and PEx history [Lancet Respir Med 2019;7:213–26].MethodsRespiratory secretions from 582 participants receiving up to six 28-day on/off treatment cycles were analysed for sputum P. aeruginosa, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus and Escherichia coli densities, P. aeruginosa susceptibilities to ciprofloxacin and nine other antimicrobials, and prevalence of other bacterial opportunists. Associations between PEx risk and sputum density, antimicrobial susceptibility and opportunist prevalence changes were studied.ResultsSputum P. aeruginosa density reductions from baseline after ARD-3150 treatments ranged from 1.77 (95% CI 2.13–1.40) versus 0.54 (95% CI 0.89–0.19) log10 CFU/g for placebo (second period) to 2.07 (95% CI 2.45–1.69) versus 0.70 (95% CI 1.11–0.29) log10 CFU/g for placebo (fourth period) with only modest correlation between density reduction magnitude and PEx benefit. ARD-3150 (but not placebo) treatment was associated with increased P. aeruginosa ciprofloxacin MIC but not emergence of other bacterial opportunists across the study; ciprofloxacin MIC50 increased from 0.5 to 1 mg/L, MIC90 increased from 4 to 16 mg/L. Other antimicrobial MIC were mostly unaffected.ConclusionMicrobiological changes over 48 weeks of ARD-3150 treatment appear modest. Ciprofloxacin susceptibility (but not other antimicrobial susceptibility) decreases were observed that did not appear to preclude PEx risk reduction benefit.  相似文献   
147.
148.
149.
150.
Infections and graft-versus-host disease (GVHD) have historically resulted in high mortality among children undergoing umbilical cord blood transplantation (UCBT). However, recent advances in clinical practice have likely improved outcomes of these patients. We conducted a retrospective cohort study of children (<18years of age) undergoing UCBT at Duke University between January 1, 1995 and December 31, 2014. We compared 2-year all-cause and cause-specific mortality during 3 time periods based on year of transplantation (1995 to 2001, 2002 to 2007, and 2008 to 2014). We used multivariable Cox regression to identify demographic and UCBT characteristics that were associated with all-cause mortality, transplantation-related mortality, and death from invasive aspergillosis after adjustment for time period. During the 20-year study period 824 children underwent UCBT. Two-year all-cause mortality declined from 48% in 1995 to 2001 to 30% in 2008 to 2014 (P?=?.0002). White race and nonmalignant UCBT indications were associated with lower mortality. Black children tended to have a higher risk of death for which GVHD (18% versus 11%; P?=?.06) or graft failure (9% versus 3%; P?=?.01) were contributory than white children. Comparing 2008 to 2014 with 1995 to 2001, more than half (59%) of the reduced mortality was attributable to a reduction in infectious mortality, with 45% specifically related to reduced mortality from invasive aspergillosis. Antifungal prophylaxis with voriconazole was associated with lower mortality from invasive aspergillosis than low-dose amphotericin B lipid complex (hazard ratio, .09; 95% confidence interval, .01 to .76). With the decline in mortality from invasive aspergillosis, adenovirus and cytomegalovirus have become the most frequentinfectious causes of death in children after UCBT. Advances in clinical practice over the past 20years improved survival of children after UCBT. Reduced mortality from infections, particularly invasive aspergillosis, accounted for the largest improvement in survival and was associated with use of voriconazole for antifungal prophylaxis.  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