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   51篇
  免费   8篇
  2019年   3篇
  2018年   3篇
  2017年   1篇
  2016年   2篇
  2015年   1篇
  2014年   11篇
  2013年   1篇
  2012年   4篇
  2011年   10篇
  2010年   2篇
  2009年   1篇
  2006年   1篇
  2004年   1篇
  2000年   1篇
  1999年   4篇
  1996年   1篇
  1992年   1篇
  1988年   1篇
  1987年   3篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1981年   2篇
排序方式: 共有59条查询结果,搜索用时 625 毫秒
1.
Highly pathogenic influenza A/H5N1 has persistently but sporadically caused human illness and death since 1997. Yet it is still unclear how this pathogen is able to persist globally. While wild birds seem to be a genetic reservoir for influenza A, they do not seem to be the main source of human illness. Here, we highlight the role that domestic poultry may play in maintaining A/H5N1 globally, using theoretical models of spatial population structure in poultry populations. We find that a metapopulation of moderately sized poultry flocks can sustain the pathogen in a finite poultry population for over two years. Our results suggest that it is possible that moderately intensive backyard farms could sustain the pathogen indefinitely in real systems. This fits a pattern that has been observed from many empirical systems. Rather than just employing standard culling procedures to control the disease, our model suggests ways that poultry production systems may be modified.  相似文献   
2.
Mucuna pruriens seeds have relatively high crude protein (CP) concentrations, but little is known about their potential to replace commonly used CP supplements in ruminant rations. The aim of this experiment was to determine effects of replacing soybean meal (SB) with Mucuna on the performance of lambs. Forty Rambouillet lambs (33.2 ± 5.73 kg) fed a basal diet of maize grain, cottonseed hulls and urea were randomly assigned to one of four supplements formulated by substituting 0 (SB), 330 (Lo), 670 (Med) or 1000 g/kg (Hi) of soybean meal with rolled Mucuna seeds. Lambs were housed individually in metabolic crates and allowed ad libitum access to isocaloric (metabolizable energy=11.7 MJ/kg dry matter, DM) and isonitrogenous (CP = 146 g/kg, DM) diets for 14 d of adaptation and 7 d of total fecal collection. Fecal egg counts and coccidian oocyst scores were determined on d 14. Dry matter intake (1.7 kg/d versus 1.5 kg/d; P<0.05), CP digestibility (774 g/kg versus 714 g/kg DM; P<0.05) and N retention (28.0 g/d versus 20.4 g/d; P<0.01) were higher and amylase-pretreated neutral detergent fiber digestibility (617 g/kg versus 686 g/kg DM) was lower (P<0.05) in sheep fed SB versus Mucuna diets. However, supplementary protein source did not affect rumen pH, blood urea N or glucose concentration, or fecal egg counts. Increasing the level of Mucuna supplementation increased (P<0.05) level and efficiency of microbial protein synthesis, ruminal fluid acidity, total volatile fatty acid concentration, decreased (P<0.05) coccidian oocyst scores, and tended (P<0.10) to increase N retention. Therefore, SB is a better supplement than Mucuna to support performance of lambs. Nevertheless, Mucuna seeds are a promising CP supplement for situations where cost or availability precludes use of SB in ruminant rations.  相似文献   
3.
The association is still not clear between the common APOE polymorphism and coronary heart disease (CHD) risk, nor its modulation by diet. Thus, our aim was to study the association between the APOE genotypes and incident CHD and how dietary fat and alcohol consumption modify these effects. We performed a nested case-control study in the Spanish European Prospective Investigation into Cancer and Nutrition cohort. Healthy men and women (41?440, 30-69 years) were followed up over a 10-year period, with the incident CHD cases being identified. We analyzed 534 incident CHD cases and 1123 controls. APOE, dietary intake and plasma lipids were determined at baseline. The APOE polymorphism was significantly associated with low-density lipoprotein cholesterol (LDL-C), and gene-alcohol interactions in determining LDL-C were detected. In the whole population, the E2 allele was significantly associated with a lower CHD risk than E3/E3 subjects [odds ratio (OR), 0.58; 95% confidence interval (CI), 0.38-0.89]. The E4 allele did not reach statistical significance vs. E3/E3 (OR, 1.17; 95% CI, 0.88-1.58). However, saturated fat intake modified the effect of the APOE polymorphism in determining CHD risk. When saturated fat intake was low (<10% of energy), no statistically significant association between the APOE polymorphism and CHD risk was observed (P=.682). However, with higher intake (≥10%), the polymorphism was significant (P=.005), and the differences between E2 and E4 carriers were magnified (OR for E4 vs. E2, 3.33; 95% CI, 1.61-6.90). Alcohol consumption also modified the effect of the APOE on CHD risk.In conclusion, in this Mediterranean population, the E2 allele is associated with lower CHD risk, and this association is modulated by saturated fat and alcohol consumption.  相似文献   
4.
To our knowledge there has been no study of the effect of everyday air pollution on olfactory function. It was therefore the aim of this study to compare the olfactory performance of long-term residents of Mexico City, an environment with high air pollution, with the olfactory performance of residents of the Mexican state of Tlaxcala, a region geographically similar to Mexico City but with low air pollution. Healthy volunteers [82 Mexico City subjects (MEX), 86 Tlaxcala subjects (TLX)] 20-63 years of age and balanced for age and gender between the two localities were tested for the perception of the odors of everyday beverages presented in squeeze bottles. When tested with ascending concentrations of stimuli in a three-way oddball paradigm, residents of Tlaxcala detected the odors of instant coffee and of an orange drink at significantly lower concentrations than residents of Mexico City. They also performed significantly better in discriminating between the two similar-smelling Mexican beverages horchata and atole in an oddball test. Significant differences between the two populations in overall olfactory performance were apparent in three of the four age classes (20- to 29-, 30- to 39-, and 40- to 49-year-old subjects) but not in the 50-63 years age class. About 10% of MEX subjects compared to about 2% of TLX subjects were judged to have poor olfactory function; all were from the older age classes (mean age: 48.6 years). Thus, air pollution in Mexico City appears to have a substantial impact on olfactory function even in young and middle-aged residents.  相似文献   
5.

Background

Socio-economic inequalities in mortality are observed at the country level in both North America and Europe. The purpose of this work is to investigate the contribution of specific risk factors to social inequalities in cause-specific mortality using a large multi-country cohort of Europeans.

Methods

A total of 3,456,689 person/years follow-up of the European Prospective Investigation into Cancer and Nutrition (EPIC) was analysed. Educational level of subjects coming from 9 European countries was recorded as proxy for socio-economic status (SES). Cox proportional hazard model''s with a step-wise inclusion of explanatory variables were used to explore the association between SES and mortality; a Relative Index of Inequality (RII) was calculated as measure of relative inequality.

Results

Total mortality among men with the highest education level is reduced by 43% compared to men with the lowest (HR 0.57, 95% C.I. 0.52–0.61); among women by 29% (HR 0.71, 95% C.I. 0.64–0.78). The risk reduction was attenuated by 7% in men and 3% in women by the introduction of smoking and to a lesser extent (2% in men and 3% in women) by introducing body mass index and additional explanatory variables (alcohol consumption, leisure physical activity, fruit and vegetable intake) (3% in men and 5% in women). Social inequalities were highly statistically significant for all causes of death examined in men. In women, social inequalities were less strong, but statistically significant for all causes of death except for cancer-related mortality and injuries.

Discussion

In this European study, substantial social inequalities in mortality among European men and women which cannot be fully explained away by accounting for known common risk factors for chronic diseases are reported.  相似文献   
6.
7.
Summary Results from the operation of methanogenic reactors of three different sizes, using coffee pulp juice as raw material, are presented. All reactors were packed with unreticulated polyurethane foam and geometrical similarity was maintained. Pilot plant operation showed lower gas production per unit reactor volume but higher conversions per unit of organic load, even at lower temperatures.
Resumen Se presentan los resultados de la operación de tres reactores metano-génicos de differente tamaño, usando jugo de pulpa de café como materia prima. Los reactores fueron empacados con esponja de poliuretano no reticulado y se mantuvo una similitud geométrica. La operación de una planta piloto mostró una menor producción de gas por unidad volumétrica de reactor pero conversiones mejores, aún a más bajas temperaturas.

Résumé Les résultats présentés concernant le fonctionnement de trois réacteurs méthanogènes de dimensions différentes, utilisant comme matière première le jus de pulpe de café. Tous les réacteurs étaient compactés avec de la mousse de polyuréthane non réticulée, et avaient des formes géométriques similaires. Les opérations à l'échelle pilote ont donné une moindre production de gaz par unité de volume, mais un taux de conversion par unité de charge organique plus élevé, même à des températures inférieures.


Paper presented at the VII International Conference on the Global Impacts of Applied Microbiology, Helsinki, 12–16 August 1985.  相似文献   
8.
Psydrax multiflora, a new species of Vanguerieae collected in the Palawan, Luzon Island, Philippines is herein described and illustrated. Morphological observation showed that P. multilfora approaches three Malesian Psydrax species, namely P. amplifolia, P. nitida and P. puberula. However, P. multiflora can be delineated from these three by its caudate leaf apex, 20–30‐flowered umbellate inflorescences and broadly triangular corolla lobes.  相似文献   
9.
10.

Background

Based on the excellent results of the clinical trials with ALK-inhibitors, the importance of accurately identifying ALK positive lung cancer has never been greater. However, there are increasing number of recent publications addressing discordances between FISH and IHC. The controversy is further fuelled by the different regulatory approvals. This situation prompted us to investigate two ALK IHC antibodies (using a novel ultrasensitive detection-amplification kit) and an automated ALK FISH scanning system (FDA-cleared) in a series of non-small cell lung cancer tumor samples.

Methods

Forty-seven ALK FISH-positive and 56 ALK FISH-negative NSCLC samples were studied. All specimens were screened for ALK expression by two IHC antibodies (clone 5A4 from Novocastra and clone D5F3 from Ventana) and for ALK rearrangement by FISH (Vysis ALK FISH break-apart kit), which was automatically captured and scored by using Bioview''s automated scanning system.

Results

All positive cases with the IHC antibodies were FISH-positive. There was only one IHC-negative case with both antibodies which showed a FISH-positive result. The overall sensitivity and specificity of the IHC in comparison with FISH were 98% and 100%, respectively.

Conclusions

The specificity of these ultrasensitive IHC assays may obviate the need for FISH confirmation in positive IHC cases. However, the likelihood of false negative IHC results strengthens the case for FISH testing, at least in some situations.  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