首页 | 官方网站   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   1020篇
  免费   74篇
  国内免费   32篇
医药卫生   1126篇
  2021年   14篇
  2019年   15篇
  2018年   15篇
  2017年   7篇
  2016年   15篇
  2015年   19篇
  2014年   28篇
  2013年   35篇
  2012年   26篇
  2011年   51篇
  2010年   29篇
  2009年   29篇
  2008年   36篇
  2007年   67篇
  2006年   35篇
  2005年   43篇
  2004年   34篇
  2003年   27篇
  2002年   24篇
  2001年   24篇
  2000年   23篇
  1999年   23篇
  1998年   35篇
  1997年   21篇
  1996年   27篇
  1995年   18篇
  1994年   23篇
  1993年   17篇
  1992年   22篇
  1991年   23篇
  1990年   18篇
  1989年   25篇
  1988年   30篇
  1987年   30篇
  1986年   24篇
  1985年   15篇
  1984年   20篇
  1983年   16篇
  1982年   9篇
  1981年   6篇
  1980年   5篇
  1978年   6篇
  1977年   5篇
  1976年   7篇
  1975年   9篇
  1974年   8篇
  1972年   11篇
  1969年   6篇
  1968年   8篇
  1967年   5篇
排序方式: 共有1126条查询结果,搜索用时 15 毫秒
951.
OBJECTIVES: Use three-dimensional (3D) facial laser scanned images from children with fetal alcohol syndrome (FAS) and controls to develop an automated diagnosis technique that can reliably and accurately identify individuals prenatally exposed to alcohol. METHODS: A detailed dysmorphology evaluation, history of prenatal alcohol exposure, and 3D facial laser scans were obtained from 149 individuals (86 FAS; 63 Control) recruited from two study sites (Cape Town, South Africa and Helsinki, Finland). Computer graphics, machine learning, and pattern recognition techniques were used to automatically identify a set of facial features that best discriminated individuals with FAS from controls in each sample. RESULTS: An automated feature detection and analysis technique was developed and applied to the two study populations. A unique set of facial regions and features were identified for each population that accurately discriminated FAS and control faces without any human intervention. CONCLUSION: Our results demonstrate that computer algorithms can be used to automatically detect facial features that can discriminate FAS and control faces.  相似文献   
952.
BM Eley  SW Cox 《Oral diseases》1995,1(4):201-213
OBJECTIVE: The aim of this study is to determine whether gingival crevicular fluid (GCF) dipeptidyl peptidase (DPP) II or IV levels, total activity (TA) and concentration (EC), predict progressive attachment loss (AL). SUBJECTS AND METHODS: Seventy five patients with moderate periodontitis were recruited. GCF was first collected from 16 molar and premolar mesiobuccal sites and then probing attachment level (PAL) and probing pocket depth (PPD) were measured with an electronic probe. Finally, gingival index, gingival bleeding and plaque indices were scored. Patients were given basic periodontal treatment prior to baseline after which the above procedures were repeated. Patients were seen 3 monthly for 2 years and the procedures were repeated. Carefully localised radiographs were taken of the test teeth annually. RESULTS: One hundred and twenty AL sites, 88 rapid AL (RAL) and 32 gradual AL (GrAL), in 48 patients were detected. DPP It and IV levels (TA and EC) at RAL sites were significantly higher (P ≤ 0.0001) than paired control sites at the attachment loss time (ALT) and prediction time (PT). Mean levels over the study period of both proteases (TA and EC) at GrAL sites were significantly higher (P≤ 0.0001) than paired control sites. The GCF levels of DPP IV were always slightly higher than those of DPP II. Critical values (CV) of 5 μU per 30 s (TA) and 25 μU μPI-1 (EC) for both proteases showed high sensitivity and specificity values for TA and EC and these were the same at both ALT and PT. The positive predictive values were slightly higher for DPP II. Mean site DPP II and IV levels (TA and EC) in intra-patient comparisons were significantly higher (P ≤ 0.0001) at RAL and GrAL sites than non-attachment loss (NAL) sites in AL patients and mean patient levels were significantly higher (P ≤ 0.0001) in AL patients than NAL patients in inter-patient comparisons. CONCLUSIONS: These results indicate that both GCF DPP II and IV may be predictors of periodontal attachment loss.  相似文献   
953.
目的:介绍一种矫正纽扣状畸形方法,认识该术式特点。方法:选择1995-01/2005-12在北华大学第一临床医学院手外科进行指背腱膜中央束重建的患者20例,男15例,女5例;年龄18~46岁。将伤指的外侧腱沿其纵轴分为两部分,其中背侧半(内侧束)在中节以远切断,掌侧半(外侧束)在近指根部水平切断。移位外侧腱的外侧束通过Cleland's韧带及部分屈肌腱鞘在远侧指间关节伸直条件下缝合固定。采用掌长肌腱之一半腱束游离移植。在中节指骨基底偏背侧用克氏针横行钻一骨孔,使掌长肌腱通过,移植腱在背侧交叉后,将移植腱与中央腱及两侧束编织缝合,使侧束、中央束及移植腱三者融为一体重建近侧指间关节的伸指功能。采用Caroli评定标准评估疗效,分3级:优、良、可。采用外侧腱外侧束的腱固定术来维持远侧指间关节关节的伸直位,在中央腱止点利用移植腱与中央腱、侧束近端缝合重建近侧指间关节的伸指功能。结果:本组共20例,按Caroli评定标准,优15例,良4例,可1例,优良率为95%。结论:该术式的最大特点是将伸腱装置复杂的动力结构变得简单化,易于掌握,是肌腱组织移植矫正创伤后钮扣状畸形的一种有效方法。  相似文献   
954.
In the past two decades, the need for economic restructuring has served as a rationale for dismantling social programs in Canada. As it has been enacted, such social restructuring has disproportionately affected marginalized people, particularly women. In this article we explore the schism between the principles that underlie the development of healthy public policy and those that are driving current social policy development. Through this analysis we discuss the implications of policy development that is based upon principles of inequity, and we suggest that implementation of healthy public policy requires transformational change in the underlying principles of the social system. A policy shift based upon principles of equity and social justice has been espoused throughout the health promotion literature. We suggest that such a shift will be facilitated by strengthening collaborative relations among points of conflict within society and among policy makers and women's organizations.  相似文献   
955.
956.

Background  

Pancreatic ductal adenocarcinoma is a lethal disease with a 5-year survival rate of 4% and typically presents in an advanced stage. In this setting, prognostic markers identifying the more agrressive tumors could aid in managment decisions. Insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3, also known as IMP3 or KOC) is an oncofetal RNA-binding protein that regulates targets such as insulin-like growth factor-2 (IGF-2) and ACTB (beta-actin).  相似文献   
957.
Fish consumption during gestation can provide the fetus with long-chain polyunsaturated fatty acids (LCPUFA) and other nutrients essential for growth and development of the brain. However, fish consumption also exposes the fetus to the neurotoxicant, methyl mercury (MeHg). We studied the association between these fetal exposures and early child development in the Seychelles Child Development Nutrition Study (SCDNS). Specifically, we examined a priori models of Omega-3 and Omega-6 LCPUFA measures in maternal serum to test the hypothesis that these LCPUFA families before or after adjusting for prenatal MeHg exposure would reveal associations with child development assessed by the BSID-II at ages 9 and 30 months. There were 229 children with complete outcome and covariate data available for analysis. At 9 months, the PDI was positively associated with total Omega-3 LCPUFA and negatively associated with the ratio of Omega-6/Omega-3 LCPUFA. These associations were stronger in models adjusted for prenatal MeHg exposure. Secondary models suggested that the MeHg effect at 9 months varied by the ratio of Omega-6/Omega-3 LCPUFA. There were no significant associations between LCPUFA measures and the PDI at 30 months. There were significant adverse associations, however, between prenatal MeHg and the 30-month PDI when the LCPUFA measures were included in the regression analysis. The BSID-II mental developmental index (MDI) was not associated with any exposure variable. These data support the potential importance to child development of prenatal availability of Omega-3 LCPUFA present in fish and of LCPUFA in the overall diet. Furthermore, they indicate that the beneficial effects of LCPUFA can obscure the determination of adverse effects of prenatal MeHg exposure in longitudinal observational studies.  相似文献   
958.
The Seychelles Child Development Study was designed to test the hypothesis that prenatal exposure to MeHg from maternal consumption of a diet high in fish is detrimental to child neurodevelopment. To date, no consistent pattern of adverse associations between prenatal exposure and children's development has appeared. In a comprehensive review of developmental studies involving MeHg, a panel of experts recommended a more consistent use of the same endpoints across studies to facilitate comparisons. Both the SCDS and the Faeroe Islands studies administered the Bender Visual Motor Gestalt Test. However, the method of test administration and scoring used was different. We repeated the test on the SCDS Main Study children (mean age 10.7 years) using the same testing and scoring procedure reported by the Faeroe studies to obtain Copying Task and Reproduction Task scores. We found no association between prenatal MeHg exposure and Copying Task scores which was reported from the Faeroese study. However, our analysis did show a significant adverse association between MeHg and Reproduction Task scores with all the data (p=0.04), but not when the single outlier was removed (p=0.07). In a population whose exposure to MeHg is from fish consumption, we continue to find no consistent adverse association between MeHg and visual motor coordination.  相似文献   
959.
Colon cancer stem cells are believed to originate from a rare population of putative CD133+ intestinal stem cells. Recent publications suggest that a small subset of colon cancer cells expresses CD133, and that only these CD133+ cancer cells are capable of tumor initiation. However, the precise contribution of CD133+ tumor-initiating cells in mediating colon cancer metastasis remains unknown. Therefore, to temporally and spatially track the expression of CD133 in adult mice and during tumorigenesis, we generated a knockin lacZ reporter mouse (CD133lacZ/+), in which the expression of lacZ is driven by the endogenous CD133 promoters. Using this model and immunostaining, we discovered that CD133 expression in colon is not restricted to stem cells; on the contrary, CD133 is ubiquitously expressed on differentiated colonic epithelium in both adult mice and humans. Using Il10-/-CD133lacZ mice, in which chronic inflammation in colon leads to adenocarcinomas, we demonstrated that CD133 is expressed on a full gamut of colonic tumor cells, which express epithelial cell adhesion molecule (EpCAM). Similarly, CD133 is widely expressed by human primary colon cancer epithelial cells, whereas the CD133- population is composed mostly of stromal and inflammatory cells. Conversely, CD133 expression does not identify the entire population of epithelial and tumor-initiating cells in human metastatic colon cancer. Indeed, both CD133+ and CD133- metastatic tumor subpopulations formed colonospheres in in vitro cultures and were capable of long-term tumorigenesis in a NOD/SCID serial xenotransplantation model. Moreover, metastatic CD133- cells form more aggressive tumors and express typical phenotypic markers of cancer-initiating cells, including CD44 (CD44+CD24-), whereas the CD133+ fraction is composed of CD44lowCD24+ cells. Collectively, our data suggest that CD133 expression is not restricted to intestinal stem or cancer-initiating cells, and during the metastatic transition, CD133+ tumor cells might give rise to the more aggressive CD133(- )subset, which is also capable of tumor initiation in NOD/SCID mice.  相似文献   
960.
Hot flashes are experienced by over 70% of menopausal women. Criteria to classify hot flashes from physiologic signals show variable performance. The primary aim was to compare conventional criteria to Support Vector Machines (SVMs), an advanced machine learning method, to classify hot flashes from sternal skin conductance. Thirty women with ≥4 hot flashes/day underwent laboratory hot flash testing with skin conductance measurement. Hot flashes were quantified with conventional (≥2 μmho, 30 s) and SVM methods. Conventional methods had poor sensitivity (sensitivity=0.41, specificity=1, positive predictive value (PPV)=0.94, negative predictive value (NPV)=0.85) in classifying hot flashes, with poorest performance among women with high body mass index or anxiety. SVM models showed improved performance (sensitivity=0.89, specificity=0.96, PPV=0.85, NPV=0.96). SVM may improve the performance of skin conductance measures of hot flashes.  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-23

京公网安备 11010802026262号