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   2582篇
  免费   155篇
  国内免费   26篇
耳鼻咽喉   75篇
儿科学   123篇
妇产科学   143篇
基础医学   219篇
口腔科学   112篇
临床医学   309篇
内科学   631篇
皮肤病学   97篇
神经病学   109篇
特种医学   81篇
外科学   400篇
综合类   35篇
一般理论   1篇
预防医学   80篇
眼科学   113篇
药学   118篇
中国医学   1篇
肿瘤学   116篇
  2024年   6篇
  2023年   37篇
  2022年   48篇
  2021年   82篇
  2020年   61篇
  2019年   75篇
  2018年   98篇
  2017年   73篇
  2016年   111篇
  2015年   123篇
  2014年   144篇
  2013年   168篇
  2012年   216篇
  2011年   169篇
  2010年   87篇
  2009年   68篇
  2008年   164篇
  2007年   149篇
  2006年   175篇
  2005年   140篇
  2004年   130篇
  2003年   82篇
  2002年   101篇
  2001年   50篇
  2000年   37篇
  1999年   31篇
  1998年   16篇
  1997年   9篇
  1996年   6篇
  1995年   7篇
  1992年   4篇
  1991年   9篇
  1990年   7篇
  1989年   3篇
  1988年   3篇
  1987年   8篇
  1985年   9篇
  1984年   5篇
  1983年   3篇
  1982年   4篇
  1980年   2篇
  1979年   6篇
  1975年   2篇
  1974年   5篇
  1972年   5篇
  1970年   2篇
  1969年   2篇
  1968年   3篇
  1967年   3篇
  1965年   3篇
排序方式: 共有2763条查询结果,搜索用时 23 毫秒
91.
Recent studies have established ciliary dysfunction as the underlying cause of a broad range of multi-organ phenotypes, known as 'ciliopathies'. Ciliopathy-associated proteins have a common site of action in the cilium, however, their overall importance for ciliary function differs, as implied by the extreme variability in ciliopathy phenotypes. The aim of this study was to gain more insight in the function of two ciliopathy-associated protein homologs, RPGR interacting protein 1 (RPGRIP1) and RPGRIP1-like protein (RPGRIP1L). Mutations in RPGRIP1 lead to the eye-restricted disease Leber congenital amaurosis, while mutations in RPGRIP1L are causative for Joubert and Meckel syndrome, which affect multiple organs and are at the severe end of the ciliopathy spectrum. Using tandem affinity purification in combination with mass spectrometry, we identified Nek4 serine/threonine kinase as a prominent component of both the RPGRIP1- as well as the RPGRIP1L-associated protein complex. In ciliated cells, this kinase localized to basal bodies, while in ciliated organs, the kinase was predominantly detected at the ciliary rootlet. Down-regulation of NEK4 in ciliated cells led to a significant decrease in cilium assembly, pointing to a role for Nek4 in cilium dynamics. We now hypothesize that RPGRIP1 and RPGRIP1L function as cilium-specific scaffolds that recruit a Nek4 signaling network which regulates cilium stability. Our data are in line with previously established roles in the cilium of other members of the Nek protein family and define NEK4 as a ciliopathy candidate gene.  相似文献   
92.
Background/aim Gout may cause various radiographic abnormalities such as cartilage loss, spurs, sclerosis, and periostal new bone formation. The purpose of this study was to investigate the frequency of Achilles and plantar spurs and related factors in gout patients.Matherial and methodsWe performed a retrospective review of gout patients, treated at Hacettepe University hospitals between 2014 and 2019. We identified patients from the hospital records using the ICD-10 code (M10). Demographic and clinical features, comorbidities, and foot radiographies were collected. The radiographies were evaluated by a rheumatologist (U.K.) who was experienced in musculoskeletal radiography. Factors predicting the spurs were analyzed by logistic regression analysis.Results181 patients who had lateral foot radiograph were included in this study. Eighty-one (44.7%) patients had score ≥ 2 Achilles spur, 81 (44.7%) patients had score ≥ 2 plantar spur, and 22 (12.1%) patients had no spur. Age, disease duration, duration between the gout diagnosis and appearing spur, the presence of metabolic comorbidities and hypertension were higher in both Achilles and plantar spurs than no spur group. Forty (22.1%) patients had score ≥ 2 both Achilles and plantar spur. In this group, the mean age was older and the proportion of metabolic comorbidities was higher than the groups of Achilles and plantar spur with a score 0 or 1. Predictor of the development of large or moderate-severe calcaneal spur was the existence of metabolic comorbidity [OR (95% CI): 3.49 (1.11–11.0) and p = 0.033].ConclusionThe presence of metabolic comorbidities increases the frequency of calcaneal spurs in gout patients. This condition can be explained by the impaired microvascular structure and increased hypoxia resulting in calcification on the tendon and ligament insertion sites.  相似文献   
93.
Image quality in non‐contrast‐enhanced (NCE) angiograms is often limited by scan time constraints. An effective solution is to undersample angiographic acquisitions and to recover vessel images with penalized reconstructions. However, conventional methods leverage penalty terms with uniform spatial weighting, which typically yield insufficient suppression of aliasing interference and suboptimal blood/background contrast. Here we propose a two‐stage strategy where a tractographic segmentation is employed to auto‐extract vasculature maps from undersampled data. These maps are then used to incur spatially adaptive sparsity penalties on vascular and background regions. In vivo steady‐state free precession angiograms were acquired in the hand, lower leg and foot. Compared with regular non‐adaptive compressed sensing (CS) reconstructions (CSlow), the proposed strategy improves blood/background contrast by 71.3 ± 28.9% in the hand (mean ± s.d. across acceleration factors 1–8), 30.6 ± 11.3% in the lower leg and 28.1 ± 7.0% in the foot (signed‐rank test, P < 0.05 at each acceleration). The proposed targeted reconstruction can relax trade‐offs between image contrast, resolution and scan efficiency without compromising vessel depiction. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
94.
DNA methods have resulted in improved renal allograft survival rates in cadaveric renal transplantation. This paper describes the impact of DNA typing by PCR-SSP on a living-related renal transplant (LRRT) programme. It evaluates error rates in serology, acute rejections, graft function and survival rates between the two typing methods. Serological typing was carried out on CTS 120 antisera Class 1, 60 antisera Class 2, 72 antisera Terasaki Class 1 and 72 antisera Class 2 antigens. Low-resolution PCR-SSP typing was carried out by 24 primers for HLA-A, 48 for HLA-B and 24 for HLA-DR. Of the 585 transplants: 159 (Group I) were serology based; 172 were serology and PCR-SSP based for HLA-DR (Group II); and 254 were serology and PCR-SSP based for HLA-A and -B, and only PCR-SSP based for HLA-DR (Group III). Error rates in serology compared with PCR-SSP were 24% for HLA-A, 16% for HLA-B and 35% for HLA-DR. Acute rejections were 39%, 30% 26% in Groups I, II and III, respectively ( P= 0.02). Graft function of serum creatinine <1.5 mg/dl at 1 year was found in 26% of the Group I patients compared with 48% of those in Group III ( P <0.0001). One- and 3-year graft survival was 93% and 87% for Group II compared with 81% and 69% for Group I, respectively ( P= 0.0001). Matching by this combination of serology and PCR-SSP is not only economical for a developing country but also improves graft survival by 12% and 18% at 1 and 3 years, respectively.  相似文献   
95.

Purpose  

In this study, our objective was to investigate the development of the gallbladder, its morphological structure and relationship with the adjacent organs during the fetal period.  相似文献   
96.
ObjectiveThe objective of this study was to report the first case of prenatal diagnosis of the fetal 20p13 microdeletion syndrome in the literature.Case reportThe mother was 31 years old and had a first trimester serum screening that indicated the fetus was at low risk. The prenatal ultrasound at 23 weeks of gestation showed mild ventriculomegaly (10.2 mm) and absent septum pellucidum. She underwent amniocentesis because of the abnormal imaging results. Karyotype analysis revealed normal results. Chromosome microarray analysis (CMA) was then performed to provide genetic analysis of the fetus and parents. CMA detected 317.902 kb deletion of 20p13 in fetus. Finally, pregnancy was terminated at 32 weeks of gestation.ConclusionThis study is the first to report the prenatal diagnosis of a 20p13 microdeletion syndrome. Our results further confirmed that genes in this region, including SOX12, NRSN2 are essential for normal fetal growth and TBC1D20 for normal brain development.  相似文献   
97.
There is a significant body of evidence showing that efficient vaccination schemes against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is helping control the coronavirus disease 2019 (COVID-19) pandemic. However, this goal cannot be achieved without real world data highlighting the impact of vaccines against viral spread. In this study, we have aimed at differentially investigating the impact of COVID-19 vaccines (CoronaVac, Pfizer/BioNTech, Astra/Zeneca Oxford, Janssen) used in North Cyprus in limiting the viral load of Delta and Omicron variants of SARS-COV-2. We have utilized real-time quantitative polymerase chain reaction cycle threshold values (Ct values) as a proxy of viral load of the two SARS-CoV-2 variants. Our results indicate that the administration of at least two doses of the messenger RNA-based Pfizer/BioNTech vaccine leads to the lowest viral load (highest Ct values) obtained for both Omicron and Delta variants. Interestingly, regardless of the vaccine type used, our study revealed that Delta variant produced significantly higher viral loads (lower Ct values) compared with the Omicron variant, where the latter was more commonly associated with younger patients. Viral spread is a crucial factor that can help determine the future of the pandemic. Thus, prioritizing vaccines that will play a role in not only preventing severe disease but also in limiting viral load and spread may contribute to infection control strategies.  相似文献   
98.

Objective

To investigate the effect of chronic pelvic pain (CPP), a debilitating condition, on sleep quality.

Methods

The present case–control study enrolled women older than 18 years attending the Gynecology Clinic of Çanakkale Onsekiz Mart University Hospital, Çanakkale, Turkey, with CPP between August 2011 and August 2012. The control group was selected from women attending the clinic for another complaint. Sleep quality was evaluated via the Pittsburgh Sleep Quality Index, and differences between the groups were compared by t and χ2 tests.

Results

During the study period, 157 women were enrolled. Seventy-two had CPP symptoms, and 85 attended the clinic for other complaints. Poor sleep quality was found in 80% (n = 58) of the women with CPP, and 55% (n = 47) of the control group (P < 0.05).

Conclusion

Women with CPP were found to have poor sleep quality. Sleep education should be recommended in psychiatry and neurology clinics to increase the awareness of sleeping problems among these women.  相似文献   
99.
Purpose: The aim of this study was to compare vertical and horizontal mandibular alveolar bone resorption by measuring bone morphological variation in Kennedy Class II removable partial denture (RPD) wearers and non‐wearers using cone‐beam computed tomography (CBCT). Materials and Methods: In total, 124 sites in the CBCT scans of 62 (29 RPD non‐wearers, 33 RPD wearers) Kennedy Class II patients were analyzed retrospectively. Three‐dimensional representations of the mandible with superimposed cross‐sectional slices were developed with the CBCT scans to evaluate the mandibular alveolar height and width by measuring distances between the mandibular canal, mylohyoid ridge, alveolar crest, and lower border of the mandible in four regions (eight sites) of Kennedy Class II non‐wearers and wearers of RPDs. Results: Mandibular alveolar bone height and width were significantly lower in edentulous sites when compared with dentate sites in both Kennedy Class II non‐wearers and wearers of RPDs (p < 0.05). Additionally, mean vertical and horizontal mandibular bone resorption was significantly higher in RPD wearers than in non‐wearers (p < 0.05). Conclusions: Vertical and horizontal alveolar bone resorption was found to be higher in the RPD wearing patients when comparing the dentate and edentulous sites.  相似文献   
100.
Summary Prolonged supplementation of vitamins A and E (2500 IU and 11.3 IU/rat daily) in 10.3% and 21.6% fatty diets administered to methylnitrosourea-induced Sprague-Dawley rats caused alterations in plasma and liver levels of both vitamins as well as of the total lipids. Liver vitamin A levels increased steadily (more than four-fold) until termination of the experiment, whereas plasma vitamin A levels only showed a minor increase at the end of the study in comparison to rats fed a standard diet. Liver vitamin E levels initially showed no difference from those of rats treated with a standard diet, and were decreased at the end of the experiment, whereas the respective plasma levels were increased throughout the study, only showing a decrease relative to initial values at termination of the experiment. Plasma total lipids increased with age and following supplementation of the vitamins in the high-fat diet, whereas liver total lipids were influenced less by aging than by the fat and vitamin contents of the respective diets. The observed alterations were, however, not related to significant chemopreventive activity of the vitamins A and E contained in high-fat diets.Dedicated to Professor Dr. Dietrich Schmähl on the occasion of his 65th birthday  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