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   7209篇
  免费   730篇
  国内免费   26篇
耳鼻咽喉   87篇
儿科学   230篇
妇产科学   129篇
基础医学   970篇
口腔科学   200篇
临床医学   764篇
内科学   1672篇
皮肤病学   138篇
神经病学   705篇
特种医学   194篇
外国民族医学   2篇
外科学   1053篇
综合类   70篇
一般理论   1篇
预防医学   657篇
眼科学   135篇
药学   383篇
中国医学   13篇
肿瘤学   562篇
  2023年   36篇
  2022年   65篇
  2021年   199篇
  2020年   87篇
  2019年   249篇
  2018年   273篇
  2017年   193篇
  2016年   185篇
  2015年   218篇
  2014年   251篇
  2013年   342篇
  2012年   409篇
  2011年   394篇
  2010年   257篇
  2009年   213篇
  2008年   326篇
  2007年   357篇
  2006年   345篇
  2005年   308篇
  2004年   251篇
  2003年   247篇
  2002年   264篇
  2001年   176篇
  2000年   202篇
  1999年   176篇
  1998年   69篇
  1997年   70篇
  1996年   57篇
  1995年   55篇
  1994年   49篇
  1993年   40篇
  1992年   145篇
  1991年   162篇
  1990年   129篇
  1989年   138篇
  1988年   122篇
  1987年   103篇
  1986年   113篇
  1985年   79篇
  1984年   71篇
  1983年   57篇
  1981年   28篇
  1980年   27篇
  1979年   58篇
  1977年   33篇
  1976年   30篇
  1975年   26篇
  1974年   33篇
  1973年   40篇
  1969年   25篇
排序方式: 共有7965条查询结果,搜索用时 15 毫秒
91.
The influence of energy restriction (ER) on muscle is controversial, and the mechanisms are not well understood. To study the effect of ER on skeletal muscle phenotype and the influence of vitamin D, rats (n = 34) were fed a control diet or an ER diet. Muscle mass, muscle somatic index (MSI), fiber-type composition, fiber size, and metabolic activity were studied in tibialis cranialis (TC) and soleus (SOL) muscles. Plasma vitamin D metabolites and renal expression of enzymes involved in vitamin D metabolism were measured. In the ER group, muscle weight was unchanged in TC and decreased by 12% in SOL, but MSI increased in both muscles (p < 0.0001) by 55% and 36%, respectively. Histomorphometric studies showed 14% increase in the percentage of type IIA fibers and 13% reduction in type IIX fibers in TC of ER rats. Decreased size of type I fibers and reduced oxidative activity was identified in SOL of ER rats. An increase in plasma 1,25(OH)2-vitamin D (169.7 ± 6.8 vs. 85.4 ± 11.5 pg/mL, p < 0.0001) with kidney up-regulation of CYP27b1 and down-regulation of CYP24a1 was observed in ER rats. Plasma vitamin D correlated with MSI in both muscles (p < 0.001), with the percentages of type IIA and type IIX fibers in TC and with the oxidative profile in SOL. In conclusion, ER preserves skeletal muscle mass, improves contractile phenotype in phasic muscles (TC), and reduces energy expenditure in antigravity muscles (SOL). These beneficial effects are closely related to the increases in vitamin D secondary to ER.  相似文献   
92.
Modern four-factor prothrombin complex concentrate was designed originally for rapid targeted replacement of the coagulation factors II, VII, IX and X. Dosing strategies for the approved indication of vitamin K antagonist-related bleeding vary greatly. They include INR and bodyweight-related protocols as well as fixed dose regimens. Particularly in the massively bleeding trauma and cardiac surgery patient, four-factor prothrombin complex concentrate is used increasingly for haemostatic resuscitation. Members of the Transfusion and Haemostasis Subcommittee of the European Association of Cardiothoracic Anaesthesiology performed a systematic literature review on four-factor prothrombin complex concentrate. The available evidence has been summarised for dosing, efficacy, drug safety and monitoring strategies in different scenarios. Whereas there is evidence for the efficacy of four-factor prothrombin concentrate for a variety of bleeding scenarios, convincing safety data are clearly missing. In the massively bleeding patient with coagulopathy, our group recommends the administration of an initial bolus of 25 IU.kg-1. This applies for: the acute reversal of vitamin K antagonist therapy; haemostatic resuscitation, particularly in trauma; and the reversal of direct oral anticoagulants when no specific antidote is available. In patients with a high risk for thromboembolic complications, e.g. cardiac surgery, the administration of an initial half-dose bolus (12.5 IU.kg-1) should be considered. A second bolus may be indicated if coagulopathy and microvascular bleeding persists and other reasons for bleeding are largely ruled out. Tissue-factor-activated, factor VII-dependent and heparin insensitive point-of-care tests may be used for peri-operative monitoring and guiding of prothrombin complex concentrate therapy.  相似文献   
93.
94.
BackgroundPrevious data has shown that severe traumatic injury is associated with bone marrow dysfunction, which manifests as persistent injury-associated anemia. This study sought to identify whether the expression of erythropoiesis-related microRNAs were altered in the bone marrow of trauma patients to determine if these microRNAs play a role in persistent injury-associated anemia.MethodsBone marrow was collected from severely injured trauma patients who underwent fracture fixation as well as patients who underwent elective hip replacement. There were 27 trauma patients and 10 controls analyzed. Total RNA and microRNA were isolated from CD34-positive cells using the RNeasy Plus Mini kit, and genome-wide microRNA expression patterns were assayed. Genes with significant expression differences were found using BRB-ArrayTools with a significance of P < .01.ResultsThere were marked differences in expression of 108 microRNAs in the trauma group when compared with hip replacement patients. Four of these microRNAs play a role in regulating erythropoiesis: microRNA-150, microRNA-223, microRNA15a, and microRNA-24. These microRNAs were all upregulated significantly, with trauma/hip replacement fold changes of 1.7, 1.8, 1.2, and 1.2 respectively, and all act to suppress or regulate erythropoiesis.ConclusionAssessment of the bone marrow microRNA profile in trauma patients compared to those undergoing elective hip replacement revealed the differential expression of microRNA-150, microRNA-223, microRNA-15a, and microRNA-24. These microRNAs all play a role in decreased erythroid progenitor cell growth and provide important insight to the erythropoietic dysfunction seen after trauma.  相似文献   
95.
96.
There is a broad range of patient travel distances to reach a lung transplant hospital in the United States. Whether patient travel distance is associated with waitlist outcomes is unknown. We present a cohort study of patients listed between January 1, 2006 and May 31, 2017 using the Scientific Registry of Transplant Recipients. Travel distance was measured from the patient's permanent zip code to the transplant hospital using shared access signature URL access to Google Maps, and assessed using multivariable competing risk regression models. There were 22 958 patients who met inclusion criteria. Median travel distance was 69.7 miles. Among patients who traveled > 60 miles, 41.2% bypassed a closer hospital and sought listing at a more distant hospital. In the adjusted models, when compared to patients who traveled ≤60 miles, patients who traveled >360 miles had a 27% lower subhazard ratio (SHR) for waitlist removal (SHR 0.73, 95% confidence interval [CI]: 0.60, 0.89, P = .002), 16% lower subhazard for waitlist death (SHR 0.84; 95% CI 0.73-0.95, P = .07), and 13% increased likelihood for transplant (SHR 1.13, 95% CI: 1.07, 1.20, P < .001). Many patients bypassed the nearest transplant hospital, and longer patient travel distance was associated with favorable waitlist outcomes.  相似文献   
97.
CRADLE was a 36-month multicenter study in pediatric (≥1 to <18 years) kidney transplant recipients randomized at 4 to 6 weeks posttransplant to receive everolimus + reduced-exposure tacrolimus (EVR + rTAC; n = 52) with corticosteroid withdrawal at 6-month posttransplant or continue mycophenolate mofetil + standard-exposure TAC (MMF + sTAC; n = 54) with corticosteroids. The incidence of composite efficacy failure (biopsy-proven acute rejection [BPAR], graft loss, or death) at month 36 was 9.8% vs 9.6% (difference: 0.2%; 80% confidence interval: −7.3 to 7.7) for EVR + rTAC and MMF + sTAC, respectively, which was driven by BPARs. Graft loss was low (2.1% vs 3.8%) with no deaths. Mean estimated glomerular filtration rate at month 36 was comparable between groups (68.1 vs 67.3 mL/min/1.73 m2). Mean changes (z-score) in height (0.72 vs 0.39; P = .158) and weight (0.61 vs 0.82; P = .453) from randomization to month 36 were comparable, whereas growth in prepubertal patients on EVR + rTAC was better (P = .050) vs MMF + sTAC. The overall incidence of adverse events (AEs) and serious AEs was comparable between groups. Rejection was the leading AE for study drug discontinuation in the EVR + rTAC group. In conclusion, though AE-related study drug discontinuation was higher, an EVR + rTAC regimen represents an alternative treatment option that enables withdrawal of steroids as well as reduction of CNIs for pediatric kidney transplant recipients. ClinicalTrials.gov: NCT01544491.  相似文献   
98.
99.
The fatty acids, alcohols, and mycolic acids of 26 strains of Mycobacterium xenopi were studied by capillary gas chromatography and thin-layer chromatography. All strains contained alpha-, keto-, and omega-carboxymycolates. The primary mycolic acid cleavage product was hexacosanoic acid. The fatty acid patterns and, especially, the presence of 2-docosanol are characteristic markers of M. xenopi.  相似文献   
100.
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