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   249篇
  免费   13篇
医药卫生   262篇
  2023年   5篇
  2022年   2篇
  2021年   5篇
  2020年   5篇
  2019年   6篇
  2018年   2篇
  2017年   2篇
  2016年   1篇
  2015年   6篇
  2014年   6篇
  2013年   5篇
  2012年   15篇
  2011年   9篇
  2010年   6篇
  2009年   7篇
  2008年   14篇
  2007年   16篇
  2006年   24篇
  2005年   22篇
  2004年   15篇
  2003年   13篇
  2002年   13篇
  2001年   8篇
  2000年   9篇
  1999年   14篇
  1998年   4篇
  1997年   1篇
  1996年   3篇
  1995年   5篇
  1994年   4篇
  1992年   6篇
  1991年   3篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1986年   2篇
  1976年   1篇
排序方式: 共有262条查询结果,搜索用时 109 毫秒
1.
The study objectives were to analyze the changes in exhaled carbon monoxide (COex) induced by histamine provocation challenge in asthmatic patients and to evaluate the relationship between COex and airway sensitivity and reactivity. Levels of COex were measured in 105 nonsmoking mildly asthmatic subjects before and after histamine provocation challenge. Dose-response curves were characterized by their sensitivity (PD20) and reactivity. Dose-response slope (DRS), continuous index of responsiveness (CIR), and bronchial reactivity index (BRI) were determined as reactivity indices. Bronchial challenge was positive for 47 subjects and negative for 58. The COex levels rose significantly after bronchial challenge in the positive response group (4.49 ± 0.4 vs. 5.74 ± 0.57 ppm, p = 0.025) and in the negative response group (2.84 ± 0.25 vs 4.00 ± 0.41 ppm, p = 0.000). An inverse relation between basal COex and PD20 was found (r = - 0.318, p = 0.030). In all subjects, a proportional direct relationship between COex and DRS (r = 0.214, p = 0.015), CIR (r = 0.401, p = 0.000), and BRI (r = 0.208, p = 0.012) was observed. On stepwise multiple linear regression analysis, COex only significantly correlated with CIR (multiple r2 = 0.174, p = 0.000). In conclusion, exhaled CO determination is a noninvasive inflammatory marker of the respiratory tract, which shows an acceptable association with airway hyperresponsiveness.  相似文献   
2.
Progression of HIV disease is often accompanied by weight loss and wasting. Gestational weight gain is a strong determinant of maternal and neonatal outcomes; however, the pattern and predictors of weight gain during pregnancy among HIV-positive women are unknown. We obtained monthly anthropometric measurements in a cohort of 957 pregnant women from Tanzania who were HIV infected. We estimated the weekly rate of weight gain at various points during the second and third trimesters of pregnancy and computed rate differences between levels of sociodemographic, nutritional, immunologic, and parasitic variables at the first prenatal visit. The change in mid-upper arm circumference (MUAC) from baseline to delivery was also examined. The rate of weight gain decreased progressively during pregnancy. There was an average decline of 1 cm in MUAC between weeks 12 and 38. Lower level of education and helminthic infections at first visit were associated with decreased adjusted rates of weight gain during the third trimester. High baseline MUAC, not contributing to household income, lower serum retinol and selenium concentrations, advanced clinical stage of HIV disease, and malaria infection were related to decreased rates of weight gain during the second trimester. Low baseline CD4 T-cell counts were related to a poorer pattern of weight gain throughout pregnancy. Prevention and treatment of parasitic infections and improvement of nutritional status are likely to enhance the pattern of gestational weight gain among HIV-infected women.  相似文献   
3.
OBJECTIVES: To examine whether wasting during pregnancy, as measured by weight loss and low weight gain, is associated with increased mother-to-child transmission (MTCT) of HIV-1. METHODS: This was a cohort study in Dar es Salaam, Tanzania, among 957 HIV-1-infected pregnant women. Weight was measured at the first prenatal visit and every month thereafter until delivery. Weight loss was defined as a weekly rate of weight gain 0 and /=167 g/wk, weight loss during pregnancy was related to higher risk of intrauterine MTCT (adjusted relative risk [RR] = 2.32, 95% CI = 1.23-4.36, P = 0.009), HIV positive at birth or fetal death (RR = 2.13, 95% CI = 1.40-3.24, P = 0.0004), and HIV positive at birth or early neonatal death (RR = 1.96, 95% CI = 1.26-3.07, P = 0.003). The rate of weight gain during the 3rd trimester was inversely related to the risk of intrapartum/early breast-feeding transmission (adjusted P value, test for trend = 0.05). CONCLUSIONS: Weight loss during pregnancy increases the risk of early MTCT. Identifying causes of wasting during pregnancy may provide clues for new strategies to prevent MTCT.  相似文献   
4.
PURPOSE: To investigate whether allogeneic stem-cell transplantation (allo-SCT) may overcome the negative impact of unmutated VH genes in the outcome of patients with chronic lymphocytic leukemia (CLL). PATIENTS AND METHODS: We analyzed the outcome of patients who underwent SCT according to their VH mutational status. RESULTS: Thirty-four patients (14 allo-SCT and 20 autologous SCT [auto-SCT]) presented unmutated VH genes and 16 patients presented mutated VH genes (nine allo-SCT and seven auto-SCT). Tumoral burden pre-SCT was significantly higher in the allo-SCT patients independent of the VH mutational status. The risk of relapse was significantly higher after auto-SCT (5-year risk, 61%; 95% CI, 44% to 84%) than after allo-SCT (5-year risk 12%, 95% CI, 3% to 44%; P < .05). In the unmutated group, 13 of 20 auto-SCT and two of 14 allo-SCT patients experienced disease progression, with a risk of relapse at 5 years of 66% (95% CI, 48% to 93%) v 17% (95% CI, 5% to 60%), respectively (P = .01). CONCLUSION: These results show that allo-SCT may overcome the unfavorable effect of unmutated VH genes in patients with CLL.  相似文献   
5.
6.
BACKGROUND: Sputum microscopy for acid-fast bacilli (AFB) is the commonest diagnostic method for pulmonary tuberculosis (PTB) in developing countries. The method is reported to be less sensitive in human immunodeficiency virus (HIV) positive compared to negative patients. We determined the bacillary density in sputum of smear-positive PTB patients and related it to the patients' HIV status, CD4 cell count, clinical and demographic characteristics. METHODS: Three sputum samples per patient were examined using microscopy before initiating therapy. The AFB density was graded according to World Health Organization recommendations. The smear with the highest density was used. High bacillary density was defined as >10 AFB/field. HIV status and CD4 cell count were determined according to the national guidelines. RESULTS: Of 844 patients, 433 (51.3%) were HIV-positive. High bacillary density was significantly less common among HIV-positive (39.0%) than -negative (75.7%) patients (prevalence ratio 0.52; 95%CI 0.45-0.59, P < 0.0001). Among HIV-positive patients, the proportion of those with high bacillary density increased progressively with CD4 cell counts (P = 0.003). CONCLUSION: HIV is associated with lower AFB concentration in sputum. The AFB density falls with falling CD4 cell count. Microscopy for AFB in sputum may be less sensitive in diagnosing PTB when HIV infection is present, especially in severely immunocompromised patients.  相似文献   
7.
8.
Background: Age at menarche is an important developmental milestone known to be modified by social and environmental factors. The determinants and potential change over time of age at menarche in Colombia are not well documented.

Aims: To obtain a current estimate of age at menarche in Colombia and to examine the associations between socio-demographic characteristics and age at menarche.

Subjects and methods: Between 1998 and 2001, we obtained recalled age at menarche, socio-demographic characteristics, and physical activity information in a group of 3206 students at the National University of Colombia who completed a self-administered questionnaire. We examined the cross-sectional associations between mean age at menarche and migratory pattern, parental education, socio-economic status indicators, practice of physical activity, and year of birth using linear regression.

Results: Mean age at menarche (±?SD) was 12.68 ± 1.31. In a multivariate adjusted regression model, age at menarche was positively associated with family size and the practice of at least 2 daily hours of physical activity, and was inversely related to urbanization level, socio-economic status, and year of birth.

Conclusions: Socio-economic status is a strong predictor of menarche in this population. There appears to be a trend towards earlier menarche by year of birth.  相似文献   
9.

Background and aims

Polyunsaturated fatty acids (PUFA) may play a role in the etiology of the metabolic syndrome (MetS). The aim of the study was to examine the associations of adipose tissue PUFA biomarkers with MetS among parents and children in Mesoamerica.

Method and results

We conducted a cross-sectional study among 468 parents and 201 children aged 7–12 y from the capital cities of Guatemala, El Salvador, the Dominican Republic, Honduras, Nicaragua, Panama, Costa Rica, and Belize, and Tuxtla Gutiérrez in Mexico. We measured PUFA biomarkers in gluteal adipose tissue by gas chromatography. In adults, MetS was defined according to the National Cholesterol Education Program's Adult Treatment Panel III definition. In children, we created an age- and sex-standardized metabolic risk score using abdominal circumference, the homeostasis model of insulin resistance, blood pressure, serum HDL cholesterol, and triglycerides. We estimated prevalence ratios of MetS and mean differences in metabolic score across quartiles of PUFA using multivariable-adjusted Poisson and linear regression models, respectively. Among adults, MetS was associated with low alpha-linolenic acid (ALA), high eicosapentaenoic acid (EPA), and low gamma-linolenic acid (GLA). It was linearly, positively associated with dihomo-gamma-linolenic acid (DGLA) and estimated Δ6-desaturase (D6D) activity. Among children, the metabolic score was positively associated with docosapentaenoic acid (DPA), DGLA, and D6D activity.

Conclusions

Among Mesoamerican adults, MetS prevalence is inversely associated with adipose tissue ALA and GLA, and positively associated with EPA, DGLA, and the D6D index. Among children, metabolic risk score is positively associated with DPA, DGLA, and the D6D index.  相似文献   
10.
Prepregnancy overweight and obesity are associated with higher risk of perinatal complications. However, the effect of weight change prior to pregnancy on perinatal outcome is largely unknown. Therefore, it is aimed to examine the impact on perinatal outcomes of interpregnancy BMI change in women of different BMI categories. The MEDLINE, EMBASE, LILACS, and CINAHL databases were searched (1990‐August 2019). Observational studies on interpregnancy BMI change were selected. Outcomes evaluated were gestational diabetes mellitus (GDM), preeclampsia, gestational hypertension (GH), cesarean section, preterm birth, and newborns being large (LGA) or small (SGA) for gestational age. Meta‐analyses and meta‐regression analyses were executed. Thirty studies were included (n > 1 million). Interpregnancy BMI gain was associated with a higher risk of GDM (for BMI gain ≥3 kg/m2: OR 2.21; [95%CI 1.53‐3.19]), preeclampsia (1.77 [1.53‐2.04]), GH (1.78 [1.61‐1.97]), cesarean section (1.32 [1.24‐1.39]), and LGA (1.54 [1.28‐1.86]). The effects of BMI gain were most pronounced in women with BMI <25 kg/m2 before the first pregnancy regarding GDM, GH, and cesarean section. Except for LGA, interpregnancy BMI loss did not result in a decreased risk of perinatal complications. In this study, women of normal weight who gain weight before pregnancy were identified as a high‐risk population for perinatal complications. This emphasizes that weight management is important for women of all BMI categories and a pregnancy wish.  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