全文获取类型
收费全文 | 102篇 |
免费 | 7篇 |
国内免费 | 4篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有113条查询结果,搜索用时 93 毫秒
101.
Vera Isvnovics Hesham M. Shafik Mtys Prsing Szilveszter Juhos 《Freshwater Biology》2000,43(2):257-275
- 1 Cylindrospermopsis raciborskii occupies a rapidly expanding geographical area. Its invasive success challenges eutrophication control in many lakes. To understand better the load‐dependent behaviour of this nitrogen fixing cyanobacterium under in situ conditions, we studied P‐dependent growth of a C. raciborskii strain under continuous and pulsed P supply.
- 2 The Droop model reasonably described P‐dependent growth in the continuously supplied chemostats. Large P pulses, however, caused a delay in growth and cells subject to P pulses grew slower than their counterparts with the same P quota supplied continuously.
- 3 The kinetics of P uptake indicated that C. raciborskii is opportunistic with respect to P. Its high excess P storage capacity after a saturating P pulse (Qex=95 µg P [mg C]‐1) and P‐specific uptake capacity (Umax = Vmax/QP=150–1200) are indicative of storage adaptation. At the same time, the affinity of the P uptake system (Umax/K = 800–4000) is also high.
- 4 Rate of leakage exceeded that of the steady state net P uptake by one to two orders of magnitude. Growth affinity of C. raciborskii (µmax/Kµ≈ 20) was relatively low, presumably due to the substantial leakage.
- 5 The dynamics of the particular water body determine which trait contributes most to competitive success of C. raciborskii. In deep lakes with vertical nutrient gradients, the cyanobacterium may rely primarily on its high P storage capacity, which is coupled to a lack of short‐term feedback inhibition and efficient buoyancy regulation. In lakes without such gradients, high P uptake affinity may be vitally important.
102.
RD Calixto R Verlengia AH Crisp TB Carvalho MD Crepaldi AA Pereira AK Yamada GR da Mota CR Lopes 《Biology of sport / Institute of Sport》2014,31(4):289-294
This study aimed to compare the effects of different velocities of eccentric muscle actions on acute blood lactate and serum growth hormone (GH) concentrations following free weight bench press exercises performed by resistance-trained men. Sixteen healthy men were divided into two groups: slow eccentric velocity (SEV; n = 8) and fast eccentric velocity (FEV; n = 8). Both groups performed four sets of eight eccentric repetitions at an intensity of 70% of their one repetition maximum eccentric (1RMecc) test, with 2-minute rest intervals between sets. The eccentric velocity was controlled to 3 seconds per range of motion for SEV and 0.5 seconds for the FEV group. There was a significant difference (P < 0.001) in the kinetics of blood lactate removal (at 3, 6, 9, 15, and 20 min) and higher mean values for peak blood lactate (P = 0.001) for the SEV group (9.1 ± 0.5 mM) compared to the FEV group (6.1 ± 0.4 mM). Additionally, serum GH concentrations were significantly higher (P < 0.001) at 15 minutes after bench press exercise in the SEV group (1.7 ± 0.6 ng · mL−1) relative to the FEV group (0.1 ± 0.0 ng · mL−1). In conclusion, the velocity of eccentric muscle action influences acute responses following bench press exercises performed by resistance-trained men using a slow velocity resulting in a greater metabolic stress and hormone response. 相似文献
103.
Andre M Siqueira Janieldo A Cavalcante Shelia Vítor-Silva Roberto C Reyes-Lecca Aline C Alencar Wuelton M Monteiro Márcia AA Alexandre Mour?o Maria Paula G Caterina Guinovart Quique Bassat Maria das Gra?as C Alecrim Marcus VG Lacerda 《Memórias do Instituto Oswaldo Cruz》2014,109(5):569-576
Anaemia is amongst the major complications of malaria, a major public health problem
in the Amazon Region in Latin America. We examined the haemoglobin (Hb)
concentrations of malaria-infected patients and compared it to that of
malaria-negative febrile patients and afebrile controls. The haematological
parameters of febrile patients who had a thick-blood-smear performed at an infectious
diseases reference centre of the Brazilian Amazon between December 2009-January 2012
were retrieved together with clinical data. An afebrile community control group was
composed from a survey performed in a malaria-endemic area. Hb concentrations and
anaemia prevalence were analysed according to clinical-epidemiological status and
demographic characteristics. In total, 7,831 observations were included. Patients
with Plasmodium falciparum infection had lower mean Hb
concentrations (10.5 g/dL) followed by P. vivax-infected individuals
(12.4 g/dL), community controls (12.8 g/dL) and malaria-negative febrile patients
(13.1 g/dL) (p < 0.001). Age, gender and clinical-epidemiological status were
strong independent predictors for both outcomes. Amongst malaria-infected
individuals, women in the reproductive age had considerably lower Hb concentrations.
In this moderate transmission intensity setting, both vivax and falciparum malaria
are associated with reduced Hb concentrations and risk of anaemia throughout a wide
age range. 相似文献
104.
Sajin Bae Cornelia M Ulrich Lynn B Bailey Olga Malysheva Elissa C Brown David R Maneval Marian L Neuhouser Ting-Yuan David Cheng Joshua W Miller Yingye Zheng Liren Xiao Lifang Hou Xiaoling Song Katharina Buck Shirley AA Beresford Marie A Caudill 《Epigenetics》2014,9(3):396-403
DNA methylation is an epigenetic mechanism that regulates gene expression and can be modified by one-carbon nutrients. The objective of this study was to investigate the impact of folic acid (FA) fortification of the US food supply on leukocyte global DNA methylation and the relationship between DNA methylation, red blood cell (RBC) folate, and other one-carbon biomarkers among postmenopausal women enrolled in the Women's Health Initiative Observational Study. We selected 408 women from the highest and lowest tertiles of RBC folate distribution matching on age and timing of the baseline blood draw, which spanned the pre- (1994–1995), peri- (1996–1997), or post-fortification (1998) periods. Global DNA methylation was assessed by liquid chromatography-tandem mass spectrometry and expressed as a percentage of total cytosine. We observed an interaction (P = 0.02) between fortification period and RBC folate in relation to DNA methylation. Women with higher (vs. lower) RBC folate had higher mean DNA methylation (5.12 vs. 4.99%; P = 0.05) in the pre-fortification period, but lower (4.95 vs. 5.16%; P = 0.03) DNA methylation in the post-fortification period. We also observed significant correlations between one-carbon biomarkers and DNA methylation in the pre-fortification period, but not in the peri- or post-fortification period. The correlation between plasma homocysteine and DNA methylation was reversed from an inverse relationship during the pre-fortification period to a positive relationship during the post-fortification period. Our data suggest that (1) during FA fortification, higher RBC folate status is associated with a reduction in leukocyte global DNA methylation among postmenopausal women and; (2) the relationship between one-carbon biomarkers and global DNA methylation is dependent on folate availability. 相似文献
105.
Sarfraz A Tunio Neil J Oldfield Dlawer AA Ala'Aldeen Karl G Wooldridge David PJ Turner 《BMC microbiology》2010,10(1):280
Background
Glyceraldehyde 3-phosphate dehydrogenases (GAPDHs) are cytoplasmic glycolytic enzymes, which although lacking identifiable secretion signals, have also been found localized to the surface of several bacteria (and some eukaryotic organisms); where in some cases they have been shown to contribute to the colonization and invasion of host tissues. Neisseria meningitidis is an obligate human nasopharyngeal commensal which can cause life-threatening infections including septicaemia and meningitis. N. meningitidis has two genes, gapA-1 and gapA-2, encoding GAPDH enzymes. GapA-1 has previously been shown to be up-regulated on bacterial contact with host epithelial cells and is accessible to antibodies on the surface of capsule-permeabilized meningococcal cells. The aims of this study were: 1) to determine whether GapA-1 was expressed across different strains of N. meningitidis; 2) to determine whether GapA-1 surface accessibility to antibodies was dependant on the presence of capsule; 3) to determine whether GapA-1 can influence the interaction of meningococci and host cells, particularly in the key stages of adhesion and invasion. 相似文献106.
Albert Eduardo Silva Martins Norma Lucena-Silva Renan Gomes Garcia Stefan Welkovic Aureliana Barboza Maria Luiza Bezerra Menezes Magda Maruza Terezinha Tenório Ricardo AA Ximenes 《Memórias do Instituto Oswaldo Cruz》2014,109(6):738-747
Human immunodeficiency virus (HIV)-positive patients have a greater prevalence of
coinfection with human papillomavirus (HPV) is of high oncogenic risk. Indeed, the
presence of the virus favours intraepithelial squamous cell lesion progression and
may induce cancer. The aim of this study was to evaluate the prevalence of HPV
infection, distribution of HPV types and risk factors among HIV-positive patients.
Cervical samples from 450 HIV-positive patients were analysed with regard to oncotic
cytology, colposcopy and HPV presence and type by means of polymerase chain reaction
and sequencing. The results were analysed by comparing demographic data and data
relating to HPV and HIV infection. The prevalence of HPV was 47.5%. Among the
HPV-positive samples, 59% included viral types of high oncogenic risk. Multivariate
analysis showed an association between HPV infection and the presence of cytological
alterations (p = 0.003), age greater than or equal to 35 years (p = 0.002), number of
partners greater than three (p = 0.002), CD4+ lymphocyte count <
200/mm3 (p = 0.041) and alcohol abuse (p = 0.004). Although high-risk
HPV was present in the majority of the lesions studied, the low frequency of HPV 16
(3.3%), low occurrence of cervical lesions and preserved immunological state in most
of the HIV-positive patients were factors that may explain the low occurrence of
precancerous cervical lesions in this population. 相似文献
107.
Hyperlipidemia is one of the major risk factors for atherosclerosis and ischemic heart disease. Chromium (Cr) mineral is playing a crucial role in glucose and lipid homeostasis. The aim of this study was to evaluate the protective effects of combined chromium picolinate (CrPic) and atorvastatin treatment against hyperlipidemia-induced cardiac injury. Seventy-five male albino rats were divided into five groups (15 rats each). Hyperlipidemia was induced by intraperitoneal injection of a single dose of Triton X-100 (300 mg/kg body weight (b.w) (group ??). Treatment of hyperlipidemic rats was induced by daily administration of CrPic at a dose of 200 μg/kg b.w/day (group ???), atorvastatin at a dose of 10?mg/kg/day (group IV), and combined treatment with both (group V) by gavage for 7 days. At the end of experiment, serum and heart tissues were obtained. Hyperlipidemia was confirmed by histopathology of heart tissues, marked serum dyslipidemia, increased atherogenic indices, and values of ischemia-modified albumin. In addition to increased values of proprotein convertase subtilisin/kexin type 9, activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase enzyme and high relative expression levels of pentraxin-3 were observed. However, paraoxonase-1 activity was markedly decreased in the hyperlipidemic group. Significant improvement in all assessed parameters was observed in the rat group treated with both CrPic and atorvastatin. It can be concluded that combined CrPic and atorvastatin treatments had synergistic cardioprotective effects against hyperlipidemia which may be through modulating atherosclerosis as well as cardiac and aortic damage and/or activation of anti-inflammatory and anti-oxidant pathways, thus reversing endothelial dysfunction. 相似文献
108.
Archives of Microbiology - 相似文献
109.
Rongwei Teng Adele?M. Lehane Markus Winterberg Sarah?H. Shafik Robert?L. Summers Rowena?E. Martin Donelly?A. van Schalkwyk Pauline?R. Junankar Kiaran Kirk 《Bioscience reports》2014,34(6)
Although efforts to understand the basis for inter-strain phenotypic variation in the most virulent malaria species, Plasmodium falciparum, have benefited from advances in genomic technologies, there have to date been few metabolomic studies of this parasite. Using 1H-NMR spectroscopy, we have compared the metabolite profiles of red blood cells infected with different P. falciparum strains. These included both chloroquine-sensitive and chloroquine-resistant strains, as well as transfectant lines engineered to express different isoforms of the chloroquine-resistance-conferring pfcrt (P. falciparum chloroquine resistance transporter). Our analyses revealed strain-specific differences in a range of metabolites. There was marked variation in the levels of the membrane precursors choline and phosphocholine, with some strains having >30-fold higher choline levels and >5-fold higher phosphocholine levels than others. Chloroquine-resistant strains showed elevated levels of a number of amino acids relative to chloroquine-sensitive strains, including an approximately 2-fold increase in aspartate levels. The elevation in amino acid levels was attributable to mutations in pfcrt. Pfcrt-linked differences in amino acid abundance were confirmed using alternate extraction and detection (HPLC) methods. Mutations acquired to withstand chloroquine exposure therefore give rise to significant biochemical alterations in the parasite. 相似文献
110.