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   188篇
  免费   15篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2020年   3篇
  2019年   7篇
  2018年   10篇
  2017年   11篇
  2016年   8篇
  2015年   12篇
  2014年   13篇
  2013年   12篇
  2012年   16篇
  2011年   15篇
  2010年   7篇
  2009年   8篇
  2008年   6篇
  2007年   9篇
  2006年   8篇
  2005年   9篇
  2004年   9篇
  2003年   10篇
  2002年   5篇
  1999年   4篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1994年   2篇
  1993年   1篇
  1990年   1篇
  1988年   2篇
  1987年   1篇
  1978年   1篇
  1973年   1篇
排序方式: 共有203条查询结果,搜索用时 328 毫秒
1.
Summary In two patients with testicular feminization syndrome, one Yq12-positive and the other Yq12-negative, we compared phenotype, gonadal histology and ultrastructure, in vivo steroid response of the testes to the administration of exogenous gonadotropin during adrenal suppression, and of the adrenal gland to ACTH. The assumption that the constitutive Y heterochromatin could function as a regulator of steroid biosynthesis and metabolism, with or without effect at other levels, was not firmly supported by the observations reported here. However, further studies along this line may help elucidate the biologic role of this portion of the Y chromosome in humans.  相似文献   
2.
CD4-like molecules in human sperm   总被引:5,自引:0,他引:5  
The expression of a molecule recognized by CD4 monoclonal antibodies was investigated on human sperm using immunolabelling, biochemical and immunochemical methods. Flow cytometry detected a significant fluorescence signal. SDS-PAGE analysis and Western blotting identified a molecule of 60 kDa, consistent with a CD4-like structure as confirmed after selective immunoseparation. Additional bands reacting with anti-CD4 were found in sperm extracts (73 kDa) and seminal fluid (90 kDa). These data indicate that sperm express a molecule similar to the receptor for HIV described on mononuclear cells.  相似文献   
3.
We have standardized a method to assess the total effective xenoestrogen burden (TEXB) in human placentas by the extraction and separation by high-performance liquid chromatography of two fractions containing lipophilic xenoestrogens (alpha) and endogenous hormones (beta), followed by assessing their estrogenicity in MCF-7 breast cancer cell-based E-Screen and Yeast Estrogen Screen (YES) bioassays. The means of TEXB alpha concentrations (in estradiol equivalent (Eeq) units) were 1.32 and 0.77 Eeq pM g?1 placenta in the E-Screen and YES, respectively; TEXB beta concentrations were 6.97 and 11.56 Eeq pM g?1 placenta, respectively. The interclass correlation coefficient was low and a fair level of agreement was observed after kappa test correction. According to the E-Screen and YES, TEXB alpha was ≥LOD in 70.0 and 55.0% of the placentas and 92.5 and 82.5% in beta, respectively. Although both bioassays can be recommended for assessing TEXB, there is greater experience with the use of the E-Screen for estrogenic assessment after extensive extraction of complex human matrices.  相似文献   
4.
Biological Trace Element Research - Chromium (Cr) is a micromineral that is involved in the metabolism of carbohydrates, lipids, ammonia, and nucleic acids; thus, its supplementation can influence...  相似文献   
5.

Background

This study evaluated the effects of acute high-dose and chronic lifetime exposure to alcohol and exposure patterns on the development of differentiated thyroid cancer (DTC).

Methods

The Thyroid Cancer Longitudinal Study (T-CALOS) included 2,258 DTC patients (449 men and 1,809 women) and 22,580 healthy participants (4,490 men and 18,090 women) who were individually matched by age, gender, and enrollment year. In-person interviews were conducted with a structured questionnaire to obtain epidemiologic data. Clinicopathologic features of the patients were obtained by chart reviews. Odds ratios (ORs) and 95% confidence intervals (95%CI) were estimated using conditional regression models.

Results

While light or moderate drinking behavior was related to a reduced risk of DTC, acute heavy alcohol consumption (151 g or more per event or on a single occasion) was associated with increased risks in men (OR = 2.22, 95%CI = 1.27–3.87) and women (OR = 3.61, 95%CI = 1.52–8.58) compared with never-drinkers. The consumption of alcohol for 31 or more years was a significant risk factor for DTC for both men (31–40 years: OR = 1.58, 95%CI = 1.10–2.28; 41+ years: OR = 3.46, 95%CI = 2.06–5.80) and women (31–40 years: OR = 2.18, 95%CI = 1.62–2.92; 41+ years: OR = 2.71, 95%CI = 1.36–5.05) compared with never-drinkers. The consumption of a large amount of alcohol on a single occasion was also a significant risk factor, even after restricting DTC outcomes to tumor size, lymph node metastasis, extrathyroidal extension and TNM stage.

Conclusion

The findings of this study suggest that the threshold effects of acute high-dose alcohol consumption and long-term alcohol consumption are linked to an increased risk of DTC.  相似文献   
6.

Introduction

Raspberries are becoming increasingly popular due to their reported health beneficial properties. Despite the presence of only trace amounts of anthocyanins, yellow varieties seems to show similar or better effects in comparison to conventional raspberries.

Objectives

The aim of this work is to characterize the metabolic differences between red and yellow berries, focussing on the compounds showing a higher concentration in yellow varieties.

Methods

The metabolomic profile of 13 red and 12 yellow raspberries (of different varieties, locations and collection dates) was determined by UPLC–TOF-MS. A novel approach based on Pearson correlation on the extracted ion chromatograms was implemented to extract the pseudospectra of the most relevant biomarkers from high energy LC–MS runs. The raw data will be made publicly available on MetaboLights (MTBLS333).

Results

Among the metabolites showing higher concentration in yellow raspberries it was possible to identify a series of compounds showing a pseudospectrum similar to that of A-type procyanidin polymers. The annotation of this group of compounds was confirmed by specific MS/MS experiments and performing standard injections.

Conclusions

In berries lacking anthocyanins the polyphenol metabolism might be shifted to the formation of a novel class of A-type procyanidin polymers.
  相似文献   
7.
8.
Ichthyological Research - The spatial and seasonal dynamics of shallow water fish assemblages and their relationship with physical-chemical variables were investigated on Guanabara Bay, one of the...  相似文献   
9.
Postinfarct congestive heart failure is one of the leading causes of morbidity and mortality in developed and developing countries. The main purpose of this study was to investigate whether transplantation of bone marrow stromal cells (BMSC) directly into the myocardium could improve the performance of healed infarcted rat hearts. Cell culture medium with or without BMSC was injected into borders of cardiac scar tissue 4 wk after experimental infarction. Cardiac performance was evaluated 2 wk after cellular (n = 10) or medium (n = 10) injection by electro- and echocardiography. Histological study was performed 3 wk after treatment. Electrocardiography of BMSC-treated infarcted rats showed electrical and mechanical parameters more similar to those in control than in medium-treated animals: a normal frontal QRS axis in 6 of 10 BMSC-treated and all control rats and a rightward deviation of the QRS axis in all 10 medium-treated animals. BMSC treatment, assessed by echocardiography, improved fractional shortening (39.00 +/- 4.03%) compared with medium-treated hearts (18.20 +/- 0.74%) and prevented additional changes in cardiac geometry. Immunofluorescence microscopy revealed colocalization of 4',6-diamidino-2-phenylindole-labeled nuclei of transplanted cells with cytoskeletal markers for cardiomyocytes and smooth muscle cells, indicating regeneration of damaged myocardium and angiogenesis. These data provide strong evidence that BMSC implantation can improve cardiac performance in healed infarctions and open new promising therapeutic opportunities for patients with postinfarction heart failure.  相似文献   
10.
Amburana cearensis a common tree found in Northeastern Brazil is widely used in folk medicine. The present work evaluated the cytotoxicity of kaempferol, isokaempferide, amburoside A and protocatechuic acid isolated from the ethanol extract of the trunk bark of A. cearensis. The compounds were tested for their cytotoxicity on the sea urchin egg development, hemolysis assay and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay using tumor cell lines. Isokaempferide and kaempferol, but not amburoside A and protocatechuic acid, inhibited the sea urchin egg development as well as tumor cell lines, but in this assay isokaempferide was more potent than kaempferol. Protocatechuic acid was the only compound able to induce hemolysis of mouse erythrocytes, suggesting that the cytotoxicity of kaempferol and isokaempeferide was not related to membrane damage.  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