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   301篇
  免费   52篇
  国内免费   2篇
  2024年   1篇
  2023年   35篇
  2022年   23篇
  2021年   30篇
  2020年   19篇
  2019年   17篇
  2018年   13篇
  2017年   8篇
  2016年   15篇
  2015年   18篇
  2014年   27篇
  2013年   29篇
  2012年   16篇
  2011年   12篇
  2010年   4篇
  2009年   15篇
  2008年   9篇
  2007年   14篇
  2006年   9篇
  2005年   8篇
  2004年   6篇
  2003年   7篇
  2002年   3篇
  2001年   5篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1990年   1篇
  1989年   1篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1968年   1篇
排序方式: 共有355条查询结果,搜索用时 171 毫秒
81.
目的 了解TORCH感染情况,为妇幼保健提供参考依据.方法 采用捕获ELISA方法对1 253例孕妇和新生儿的血清进行TORCH-IgM抗体检测.结果 689例孕妇CMV、TOX、RV及HSVⅡ特异性IgM抗体阳性率分别为1.89%、0.87%、0.44%和0.73%;564例新生儿CMV-IgM、TOX-IgM、RV-IgM和HSVⅡ-IgM阳性率分别为6.91%、0.18%、0和0.35%.结论 检测TORCH特异性抗体对优生优育有重要关系.  相似文献   
82.
目的检测早产低体重儿(pretermlowbirthweight,PLBW)与正常体重儿(normalbirthweight,NBW)母亲的牙周临床状况及唾液中牙龈卟啉单胞菌(porphyromonasgingivalis,Pg)和直形弯曲菌(campylobacterrectus,Cr)检出率,探讨2种牙周病致病菌与PLBW发生的关系。方法选取北京四所医院产后1~1.5年的母亲99人,PLBW(试验组)母亲64人,NBW(对照组)母亲35人,收集母亲唾液样本,行全口牙周检查记录探诊深度(probingdepth,PD)、菌斑指数(plaqueindex,PLI)、出血指数(bleedingindex,BI)及临床附着丧失(clinicalattachmentloss,CAL)。用PCR检测唾液中的P岔和Cr;根据赡、Cr检出与否分为%、Cr阳性组、阴性组。结果(1)PLBW和NBW牙周临床指标及与Pg、cr水平:PLBW和NBW组CAL分别(0.06,0.62)mm(25%,75%)、(0.00,0.18)mm(25%,75%),差异有统计学意义;PLBW组心检出58人的PD2.49±2.0.37;未检出5人的PD2.03±0.54,差异有统计学意义,%检出率为92.06%;NBW组唯检出28人的PD(2.47±0.35)mm,未检出7人的PD(1.91±0.35)mm,差异有统计学意义,赡检出率为80%。PLBW与NBW的瞻检出率差异无统计学意义。PLBW组cr检出55人检出率为87.30%,检出与未检出之间4项临床指标差异均无统计学意义。NBW组D检出率为91.4%,PLBW与NBW间D检出率差异无统计学意义。(2)P譬、Cr阳性组与阴性组间临床指标及与PLBW关系:Pg阳性组86人,阴性组12人,两组4项临床指标分别为PD(2.48±0.36)mm,(1.96±0.40)mm;PLI1.71±0.46,1.37±0.38;BI(1.82,3.02)(25%,75%),(1.12,2.29)(25%,75%);CAL(0.03,0.56)ITIm(25%,75%),(0.00,0.11)mm(25%,75%)唯阳性组新生儿体重为(2482,78±833.85)g,阴性组为(3172.50±1190.1)g,差异均有统计学意义。cr阳性88人,D阳性11人,两组CAL值分别是(0.36±0.53)mm和(0.11±0.20)mm,差异有统计学意义,PD、PI、BI及新生儿体重差异均无统计学意义。结论珞、D在两组母亲唾液检出水平均高;Pg可能与PLBW发生有关;提示有必要进行孕前预防性牙周干预治疗。  相似文献   
83.
Liu LC  Hedeker D 《Biometrics》2006,62(1):261-268
A mixed-effects item response theory model that allows for three-level multivariate ordinal outcomes and accommodates multiple random subject effects is proposed for analysis of multivariate ordinal outcomes in longitudinal studies. This model allows for the estimation of different item factor loadings (item discrimination parameters) for the multiple outcomes. The covariates in the model do not have to follow the proportional odds assumption and can be at any level. Assuming either a probit or logistic response function, maximum marginal likelihood estimation is proposed utilizing multidimensional Gauss-Hermite quadrature for integration of the random effects. An iterative Fisher scoring solution, which provides standard errors for all model parameters, is used. An analysis of a longitudinal substance use data set, where four items of substance use behavior (cigarette use, alcohol use, marijuana use, and getting drunk or high) are repeatedly measured over time, is used to illustrate application of the proposed model.  相似文献   
84.
Body mass index (BMI) and waist-to-hip ratio (WHR) are two widely used anthropometric indices of body shape argued to convey different information about health and fertility. Both indices have also been shown to affect attractiveness ratings of female bodies. However, BMI and WHR are naturally positively correlated, complicating studies designed to identify their relative importance in predicting health and attractiveness outcomes. We show that the correlation between BMI and WHR depends on the assumed model of subcutaneous fat deposition. An additive model, whereby fat is added to the waist and hips at a constant rate, predicts a correlation between BMI and WHR because with increasing fat, the difference between the waist and hips becomes smaller relative to total width. This model is supported by longitudinal and cross-sectional data. We parameterised the function relating WHR to BMI for white UK females of reproductive age, and used this function to statistically decompose body shape into two independent components. We show that judgements of the attractiveness of female bodies are well explained by the component of curvaceousness related to BMI but not by residual curvaceousness. Our findings resolve a long-standing dispute in the attractiveness literature by confirming that although WHR appears to be an important predictor of attractiveness, this is largely explained by the direct effect of total body fat on WHR, thus reinforcing the conclusion that total body fat is the primary determinant of female body shape attractiveness.  相似文献   
85.
Summary .  In 2007, there were 33.2 million people around the world living with HIV/AIDS ( UNAIDS/WHO, 2007 ). In May 2003, the U.S. President announced a global program, known as the President's Emergency Plan for AIDS Relief (PEPFAR), to address this epidemic. We seek to estimate patient mortality in PEPFAR in an effort to monitor and evaluate this program. This effort, however, is hampered by loss to follow-up that occurs at very high rates. As a consequence, standard survival data and analysis on observed nondropout data are generally biased, and provide no objective evidence to correct the potential bias. In this article, we apply double-sampling designs and methodology to PEPFAR data, and we obtain substantially different and more plausible estimates compared with standard methods (1-year mortality estimate of 9.6% compared to 1.7%). The results indicate that a double-sampling design is critical in providing objective evidence of possible nonignorable dropout and, thus, in obtaining accurate data in PEPFAR. Moreover, we show the need for appropriate analysis methods coupled with double-sampling designs.  相似文献   
86.
Summary Evaluation of HIV vaccine candidates in nonhuman primates (NHPs) is a critical step toward developing a successful vaccine to control the HIV pandemic. Historically, HIV vaccine regimens have been tested in NHPs by administering a single high dose of the challenge virus. More recently, evaluation of candidate HIV vaccines has entailed repeated low‐dose challenges, which more closely mimic typical exposure in natural transmission settings. In this article, we consider evaluation of the type and magnitude of vaccine efficacy from such experiments. Based on the principal stratification framework, we also address evaluation of potential immunological surrogate endpoints for infection.  相似文献   
87.
1. Although several species of Peucetia (Oxyopidae) live strictly in association with plants bearing glandular trichomes worldwide, to date little is known about whether these associations are mutualistic. 2. In this study we manipulated the presence of Peucetia flava on the glandular plant Rhynchanthera dichotoma in the rainy and post‐rain season, to test the strength of its effects on leaf, bud, and flower damage and plant reproductive output. In addition, we ran independent field experiments to examine whether these sticky structures improve spider fidelity to plants. 3. Peucetia suppressed some species of foliar phytophages, but not others. Although spiders have reduced levels of leaf herbivory, this phenomenon was temporally conditional, i.e. occurred only in the post‐rain but not in the rainy season. Floral herbivory was also reduced in the presence of spiders, but these predators did not affect plant fitness components. 4. Plants that had their glandular trichomes removed retained fewer insects than those bearing such structures. Spiders remained longer on plants with glandular trichomes than on plants in which these structures had been removed. Isotopic analyses showed that spiders that fed on live and dead labelled flies adhered to the glandular hairs in similar proportions. 5. Spiders incurred no costs to the plants, but can potentially increase individual plant fitness by reducing damage to reproductive tissues. Temporal conditionality probably occurred because plant productivity exceeded herbivore consumption, thus dampening top‐down effects. Specialisation to live on glandular plants may have favoured scavenging behaviour in Peucetia, possibly an adaptation to periods of food scarcity.  相似文献   
88.
In many phase III clinical trials, it is desirable to separately assess the treatment effect on two or more primary endpoints. Consider the MERIT-HF study, where two endpoints of primary interest were time to death and the earliest of time to first hospitalization or death (The International Steering Committee on Behalf of the MERIT-HF Study Group, 1997, American Journal of Cardiology 80[9B], 54J-58J). It is possible that treatment has no effect on death but a beneficial effect on first hospitalization time, or it has a detrimental effect on death but no effect on hospitalization. A good clinical trial design should permit early stopping as soon as the treatment effect on both endpoints becomes clear. Previous work in this area has not resolved how to stop the study early when one or more endpoints have no treatment effect or how to assess and control the many possible error rates for concluding wrong hypotheses. In this article, we develop a general methodology for group sequential clinical trials with multiple primary endpoints. This method uses a global alpha-spending function to control the overall type I error and a multiple decision rule to control error rates for concluding wrong alternative hypotheses. The method is demonstrated with two simulated examples based on the MERIT-HF study.  相似文献   
89.
Decisions on public health measures to contain a pandemic are often based on parameters such as expected disease burden and additional mortality due to the pandemic. Both pandemics and non-pharmaceutical interventions to fight pandemics, however, produce economic, social, and medical costs. The costs are, for example, caused by changes in access to healthcare, social distancing, and restrictions on economic activity. These factors indirectly influence health outcomes in the short- and long-term perspective. In a narrative review based on targeted literature searches, we develop a comprehensive perspective on the concepts available as well as the challenges of estimating the overall disease burden and the direct and indirect effects of COVID-19 interventions from both epidemiological and economic perspectives, particularly during the early part of a pandemic. We review the literature and discuss relevant components that need to be included when estimating the direct and indirect effects of the COVID-19 pandemic. The review presents data sources and different forms of death counts, and discusses empirical findings on direct and indirect effects of the pandemic and interventions on disease burden as well as the distribution of health risks.  相似文献   
90.
摘要 目的:探讨LncRNA-NEAT1对妊娠期高血压大鼠JAK2/STAT3信号通路、炎症反应和妊娠结局的影响。方法:采用注射L-精氨酸甲酯的方法构建妊娠期高血压大鼠模型。采用Western blot检测JAK2/STAT3信号通路蛋白表达;采用ELISA法检测炎症因子和血管内皮损伤因子。观察并记录大鼠24 h蛋白尿、尾静脉压和死胎率。结果:与空白组相比,模型组、LncRNA-NEAT1过表达组、LncRNA-NEAT1抑制组JAK2、STAT3的蛋白表达水平明显更高(P<0.05);与模型组相比,LncRNA-NEAT1抑制组JAK2、STAT3的蛋白表达水平明显更低(P<0.05),而LncRNA-NEAT1过表达组JAK2、STAT3的蛋白表达水平明显更高(P<0.05);与空白组相比,模型组、LncRNA-NEAT1过表达组、LncRNA-NEAT1抑制组ET-1和sICAM-1水平明显更高,而NO水平明显更低(P<0.05);与模型组相比,LncRNA-NEAT1过表达组、LncRNA-NEAT1抑制组ET-1和sICAM-1水平明显更高(P<0.05),而NO水平明显更低(P<0.05),而LncRNA-NEAT1过表达组ET-1和sICAM-1表达水平明显更高,而NO明显更低(P<0.05);与空白组相比,模型组、LncRNA-NEAT1过表达组、LncRNA-NEAT1抑制组TNF-α、IL-1β、IL-18表达水平明显更高(P<0.05);与模型组相比,LncRNA-NEAT1抑制组TNF-α、IL-1β、IL-18表达水平明显更低(P<0.05),而LncRNA-NEAT1过表达组TNF-α、IL-1β、IL-18表达水平明显更高(P<0.05);与空白组相比,模型组、LncRNA-NEAT1过表达组、LncRNA-NEAT1抑制组尾静脉压和24h蛋白尿水平明显更高(P<0.05);与模型组相比,LncRNA-NEAT1抑制组尾静脉压和24 h蛋白尿表达水平明显更低(P<0.05),而LncRNA-NEAT1过表达组尾静脉压和24 h蛋白尿表达水平明显更高(P<0.05);LncRNA-NEAT1过表达组(21.56%)死胎率显著高于模型组(16.72%)和LncRNA-NEAT1抑制组(5.65%)。结论:妊娠期糖尿病大鼠LncRNA-NEAT1的表达下调可抑制JAK2/STAT3信号通路的表达并下调下游促炎因子的表达,进而缓解血管内皮损伤降低死胎率。  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