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   2931篇
  免费   170篇
  国内免费   2篇
耳鼻咽喉   41篇
儿科学   71篇
妇产科学   100篇
基础医学   401篇
口腔科学   93篇
临床医学   276篇
内科学   626篇
皮肤病学   59篇
神经病学   183篇
特种医学   140篇
外科学   399篇
综合类   43篇
一般理论   1篇
预防医学   215篇
眼科学   36篇
药学   194篇
肿瘤学   225篇
  2022年   19篇
  2021年   39篇
  2020年   30篇
  2019年   34篇
  2018年   43篇
  2017年   43篇
  2016年   43篇
  2015年   45篇
  2014年   56篇
  2013年   118篇
  2012年   131篇
  2011年   130篇
  2010年   70篇
  2009年   85篇
  2008年   126篇
  2007年   147篇
  2006年   130篇
  2005年   150篇
  2004年   124篇
  2003年   110篇
  2002年   131篇
  2001年   109篇
  2000年   81篇
  1999年   93篇
  1998年   32篇
  1996年   23篇
  1995年   21篇
  1994年   31篇
  1993年   27篇
  1992年   68篇
  1991年   65篇
  1990年   58篇
  1989年   64篇
  1988年   58篇
  1987年   58篇
  1986年   44篇
  1985年   46篇
  1984年   28篇
  1983年   23篇
  1981年   17篇
  1979年   21篇
  1978年   18篇
  1977年   20篇
  1976年   19篇
  1975年   17篇
  1974年   20篇
  1973年   20篇
  1972年   17篇
  1971年   20篇
  1969年   23篇
排序方式: 共有3103条查询结果,搜索用时 0 毫秒
61.
62.
We wanted to evaluate the cutaneous synthesis of 25OHD and cholecalciferol after one whole-body exposure to ultraviolet radiation type B (UVB) in a randomized setup. Healthy volunteers were randomized to one whole-body exposure in a commercial tanning bed with UVB emission (UVB/UVA ratio 1.8-2.0%) or an identical placebo tanning bed without UVB. The output in the 280-320?nm range was 450?μW/cm(2). Blood samples were analyzed for 25OHD and cholecalciferol at baseline and during 7?days after treatment. We included 20 volunteers, 11 to UVB and 9 to placebo treatment. During the first 6?h, no significant differences in 25OHD between the groups were found. At the end of the study, we found a mean increase of 25OHD in the UVB group of 4.5?nmol/l (SD 7?nmol/l) compared to a decline of -1.2?nmol/l (SD 7?nmol/l) in the placebo group (p?=?0.1). A linear mixed model yielded an increase of 25OHD in the UVB group of 1.0?nmol/l per 24?h (p?相似文献   
63.
64.

Introduction and hypothesis

Owing to the recent upsurge in adverse events reported after mesh-augmented pelvic organ prolapse (POP) repairs, our aim was to determine whether the location and depth of synthetic mesh can be measured postoperatively within the vaginal tissue microstructure using optical coherence tomography (OCT).

Methods

Seventeen patients with prior mesh-augmented repairs were recruited for participation. Patients were included if they had undergone an abdominal sacral colpopexy (ASC) or vaginal repair with mesh. Exclusion criteria were a postoperative period of <6 months, or the finding of mesh exposure on examination. OCT was used to image the vaginal wall at various POP-Q sites. If mesh was visualized, its location and depth was calculated and recorded.

Results

Ten patients underwent ASC and 7 patients had 8 transvaginal mesh repairs. Mesh was visualized in 16 of the 17 patients using OCT. In all ASC patients, mesh was imaged centrally at the posterior apex. In patients with transvaginal mesh in the anterior and/or posterior compartments, the mesh was visualized directly anterior and/or posterior to the apex respectively. Mean depth of the mesh in the ASC, anterior, and posterior groups was 60.9, 146.7, and 125.7 μm respectively. Mesh was visualized within the vaginal epithelial layer in all 16 patients despite the route of placement.

Conclusion

In this pilot study we found that OCT can be used to visualize polypropylene mesh within the vaginal wall following mesh-augmented prolapse repair. Regardless of abdominal versus vaginal placement, the mesh was identified within the vaginal epithelial layer.  相似文献   
65.
66.
ObjectivesThe aim of this report was to evaluate the 5-year clinical performance and survival of zirconia (NobelProcera?) single crowns.MethodsAll patients treated with porcelain-veneered zirconia single crowns in a private practice during the period October 2004 to November 2005 were included. The records were scrutinized for clinical data. Information was available for 162 patients and 205 crowns.ResultsMost crowns (78%) were placed on premolars and molars. Out of the 143 crowns that were followed for 5 years, 126 (88%) did not have any complications. Of those with complications, the most common were: extraction of abutment tooth (7; 3%), loss of retention (15; 7%), need of endodontic treatment (9; 4%) and porcelain veneer fracture (6; 3%). No zirconia cores fractured. In total 19 restorations (9%) were recorded as failures: abutment tooth extraction (7), remake of crown due to lost retention (6), veneer fracture (4), persistent pain (1) and caries (1). The 5-year cumulative survival rate (CSR) was 88.8%.ConclusionsAccording to the present 5-year results zirconia crowns (NobelProcera?) are a promising prosthodontic alternative also in the premolar and molar regions. Out of the 143 crowns followed for 5 years, 126 (88%) did not have any complications. However, 9% of the restorations were judged as failures. Further studies are necessary to evaluate the long-term success.  相似文献   
67.
Here we review the motivation for creating the enhancing neuroimaging genetics through meta-analysis (ENIGMA) Consortium and the genetic analyses undertaken by the consortium so far. We discuss the methodological challenges, findings, and future directions of the genetics working group. A major goal of the working group is tackling the reproducibility crisis affecting “candidate gene” and genome-wide association analyses in neuroimaging. To address this, we developed harmonized analytic methods, and support their use in coordinated analyses across sites worldwide, which also makes it possible to understand heterogeneity in results across sites. These efforts have resulted in the identification of hundreds of common genomic loci robustly associated with brain structure. We have found both pleiotropic and specific genetic effects associated with brain structures, as well as genetic correlations with psychiatric and neurological diseases.  相似文献   
68.
69.
Concentrations of urinary steroids are measured in anti‐doping test programs to detect doping with endogenous steroids. These concentrations are combined into ratios and followed over time in the steroidal module of the Athlete Biological Passport (ABP). The most important ratio in the ABP is the testosterone/epitestosterone (T/E) ratio but this ratio is subject to intra‐individual variations, especially large in women, which complicates interpretation. In addition, there are other factors affecting T/E. Pregnancy, for example, is known to affect the urinary excretion rate of epitestosterone and hence the T/E ratio. However, the extent of this variation and how pregnancy affect other ratios has not been fully evaluated. Here we have studied the urinary steroid profile, including 19‐norandrosterone (19‐NA), in 67 pregnant women and compared to postpartum. Epitestosterone was higher and, consequently, the T/E and 5αAdiol/E ratios were lower in the pregnant women. Androsterone/etiocholanolone (A/Etio) and 5αAdiol/5βAdiol, on the other hand, were higher in the first trimester as compared to postpartum (p<0.0001 and p=0.0396, respectively). There was no difference in A/T during pregnancy or after. 19‐NA was present in 90.5% of the urine samples collected from pregnant women. In this study, we have shown that the steroid profile of the ABP is affected by pregnancy, and hence can cause atypical passport findings. These atypical findings would lead to unnecessary confirmation procedures, if the patterns of pregnancy are not recognized by the ABP management units.  相似文献   
70.
OBJECTIVES: The first objective was to investigate the correlations between anthropometrical measurements and visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in two cohorts differing in age using magnetic resonance imaging (MRI) as reference. A second objective was to investigate the potential usage of abdominal diameters in practical estimation of adipose tissue compartments using these cohorts. METHODS: Measurements of body mass index, waist circumference, sagittal abdominal diameter (sagittal AD) and transverse abdominal diameter (transverse AD) were obtained from 336 volunteers of age 14-70 years. Manual measurements of VAT and SAT from single slice MRI at the L4-L5 level were used as reference. The abdominal diameters were measured from the MR images. Linear correlations between the anthropometrical measurements and the reference were studied. RESULTS: Sagittal AD showed the strongest correlation to VAT (r >or= 0 x 780, P<0 x 0001) and transverse AD was found to give information about the amount of SAT (r >or= 0 x 866, P<0 x 0001). The ellipse spanned by the sagittal AD and the transverse AD was strongly correlated to the total amount of adipose tissue (r >or= 0 x 962, P<0 x 0001). CONCLUSION: Strong correlations were found between sagittal and transverse abdominal diameters, assessed using MRI, and VAT and SAT, respectively. These results suggest the use of abdominal diameters in practical estimations of VAT and SAT depots.  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