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   201775篇
  免费   13455篇
  国内免费   1289篇
耳鼻咽喉   2584篇
儿科学   4750篇
妇产科学   4935篇
基础医学   29364篇
口腔科学   3784篇
临床医学   20224篇
内科学   38272篇
皮肤病学   5037篇
神经病学   16814篇
特种医学   8859篇
外科学   25758篇
综合类   2533篇
现状与发展   6篇
一般理论   154篇
预防医学   15166篇
眼科学   4934篇
药学   16227篇
  45篇
中国医学   1653篇
肿瘤学   15420篇
  2024年   664篇
  2023年   1829篇
  2022年   3761篇
  2021年   6913篇
  2020年   3783篇
  2019年   5227篇
  2018年   6280篇
  2017年   4502篇
  2016年   5634篇
  2015年   7119篇
  2014年   8856篇
  2013年   10846篇
  2012年   16222篇
  2011年   15757篇
  2010年   8998篇
  2009年   7561篇
  2008年   11544篇
  2007年   11520篇
  2006年   10423篇
  2005年   9837篇
  2004年   8716篇
  2003年   7524篇
  2002年   6582篇
  2001年   4575篇
  2000年   4172篇
  1999年   3480篇
  1998年   1550篇
  1997年   1138篇
  1996年   1076篇
  1995年   991篇
  1994年   871篇
  1993年   753篇
  1992年   1660篇
  1991年   1643篇
  1990年   1413篇
  1989年   1305篇
  1988年   1204篇
  1987年   1081篇
  1986年   1054篇
  1985年   940篇
  1984年   687篇
  1983年   599篇
  1982年   437篇
  1981年   414篇
  1980年   382篇
  1979年   560篇
  1978年   429篇
  1977年   416篇
  1976年   352篇
  1974年   377篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
63.
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   
64.
HLA haplotype mismatches have been associated with an elevated risk of acute graft-versus-host disease (aGVHD) in patients undergoing HLA-matched unrelated donor (URD) hematopoietic cell transplantation (HCT). The gamma block (GB) is located in the central MHC region between beta and delta blocks (encoding HLA-B and -C and HLA-DQ and -DR antigens, respectively) and contains numerous inflammatory and immune regulatory genes, including Bf, C2, and C4 genes. A single-center study showed that mismatches in SNPs c.2918+98G, c.3316C, and c.4385C in the GB block (C4 SNPs) were associated with higher risk of grade III-IV aGVHD. We investigated the association of GB SNP (GBS) mismatches with outcomes after 10/10 and 9/10 URD HCT (n?=?714). The primary outcome was acute GVHD. Overall survival, disease-free survival, transplantation-related mortality, relapse, chronic GVHD, and engraftment were also analyzed. DNA samples were GBS genotyped by identifying 338 SNPs across 20 kb using the Illumina NGS platform. The overall 100-day incidence of aGVHD grade II-IV and II-IV were 41% and 17%, respectively. The overall incidence of matching at all GBSs tested and at the C4 SNPs were 23% and 81%, respectively. Neither being matched across all GB SNPs tested (versus mismatched) nor having a higher number of GBS mismatches was associated with transplantation outcomes. There was no association between C4 SNP mismatches and outcomes except for an unexpected significant association between having 2 C4 SNP mismatches and a higher hazard ratio (HR) for relapse (association seen in 15 patients only; HR, 3.38, 95% confidence interval, 1.75 to 6.53; P?=?.0003). These data do not support the hypothesis that mismatching at GB is associated with outcomes after HCT.  相似文献   
65.
The revised International Staging System (R-ISS) combines ISS with genetic markers and lactate dehydrogenase and can prognosticate newly diagnosed multiple myeloma (MM). Early relapse (<24 months) after upfront autologous hematopoietic cell transplantation (AHCT) strongly predicts inferior overall survival (OS). We examined the ability of R-ISS in predicting early relapse and its independent prognostic effect on postrelapse survival after an early relapse. Using the Center for International Blood and Marrow Transplant Research database we identified MM patients receiving first AHCT within 18 months after diagnosis with available R-ISS stage at diagnosis (n?=?628). Relative risks of relapse/progression, progression-free survival (PFS), and OS were calculated with the R-ISS group as a predictor in multivariate analysis. Among early relapsers, postrelapse survival was tested to identify factors affecting postrelapse OS. The cumulative incidence of early relapse was 23%, 39%, and 50% for R-ISS I, R-ISS II, and R-ISS III, respectively (P < .001). Shorter PFS and OS were seen with higher stage R-ISS. R-ISS was independently predictive for inferior postrelapse OS among early relapsers, as was the presence of ≥3 comorbidities and the use of ≥2 induction chemotherapy lines. R-ISS stage at diagnosis predicts early post-AHCT relapse and independently affects postrelapse survival among early relapsers.  相似文献   
66.
This study examined associations between multiple types of interpersonal and noninterpersonal stressors and the subsequent occurrence of suicide ideation and attempts among female adolescents. Adolescents ages 12 to 18 years old (n = 160) at elevated risk for suicidal thoughts and behaviors were followed for 18 months, divided into two 9-month epochs for data analysis (Periods 1 and 2). Exposure to acute relational victimization, targeted rejection, nonspecified interpersonal, and noninterpersonal life stressors over the first 9-month epoch (Period 1) was assessed using semistructured interviews and an independent life stress rating team. Participants also completed phone-based semistructured interviews of suicidal thoughts and behaviors. Preliminary analyses showed significant prospective associations between acute targeted rejection and nonspecified interpersonal stress during Period 1 and suicide ideation during Period 2, as well as relational victimization and noninterpersonal stress during Period 1 and suicide attempts during Period 2. However, in logistic regression analyses that adjusted for prior suicidality and depressive symptoms, relational victimization during Period 1 (but not targeted rejection, nonspecified interpersonal or noninterpersonal events) was associated with increased odds of suicide attempt during Period 2. Therefore, acute relational victimization exposure is associated with heightened risk for suicidal behaviors in female adolescents. Future studies should examine potential mediators and moderators of this association, and these stressors should be considered for inclusion in clinical screening tools.  相似文献   
67.
68.
Severe forms of osteogenesis imperfecta (OI) are usually caused by mutations in genes that code for collagen Type I and frequently are associated with craniofacial abnormalities. However, the dental and craniofacial characteristics of OI caused by the p.Ser40Leu mutation in the IFITM5 gene have not been reported. We investigated a 15‐year‐old girl with severe OI caused by this mutation. She had marked deformations of extremity long bones. There were no clinical or radiological signs of dentinogenesis imperfecta, but one tooth was missing and several teeth were impacted. Cone beam computed tomography revealed a generalized osteopenic appearance of the craniofacial skeleton, bilateral enlargement of mandibular bodies, and areas of cortical erosions. The cranial base and skull showed a generalized granular bone pattern with a mixture of osteosclerosis and osteolysis. Sphenoid and frontal sinuses were congenitally missing. Cephalometric analysis indicated a Class III growth pattern. In this case, the IFITM5 p.Ser40Leu mutation did not affect tooth structure but was associated with deformities in craniofacial bones that resemble those in the other parts of the skeleton.  相似文献   
69.
70.
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