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91.
92.
Summary The study of dependence between random variables is a mainstay in statistics. In many cases, the strength of dependence between two or more random variables varies according to the values of a measured covariate. We propose inference for this type of variation using a conditional copula model where the copula function belongs to a parametric copula family and the copula parameter varies with the covariate. In order to estimate the functional relationship between the copula parameter and the covariate, we propose a nonparametric approach based on local likelihood. Of importance is also the choice of the copula family that best represents a given set of data. The proposed framework naturally leads to a novel copula selection method based on cross‐validated prediction errors. We derive the asymptotic bias and variance of the resulting local polynomial estimator, and outline how to construct pointwise confidence intervals. The finite‐sample performance of our method is investigated using simulation studies and is illustrated using a subset of the Matched Multiple Birth data. 相似文献
93.
94.
Genetic factors that contribute to the risk of breast cancer are largely not known and association studies have revealed several
genes with low penetrance risk alleles for breast cancer. Analysis of these genes may provide important information on the
risk factors affecting carcinogenesis. Variations in the ARLTS1, RAD51 and MDM2 genes have been associated with increased
risk of different cancer types but for breast cancer the results are not consistent. In this study we investigated the role
of the allelic variants in candidate genes acting in the tumor suppressor, DNA repair and p53 pathways as risk factors for
familial breast cancer in 147 patients displaying characteristics of familial disease. Presence of the polymorphic variants
were investigated by amplification of the corresponding regions and restriction fragment length polymorphism analysis. Genotype
and allele frequencies in the patients were significantly different for all three variants. Our results indicate that the
polymorphic variants might affect individual susceptibility towards breast cancer. 相似文献
95.
Familial Mediterranean Fever (FMF) is an autosomal recessive autoinflammatory disorder with the responsible gene of MEFV which
primarily affects Jewish, Armenian, Turkish and Arab populations. The FMF gene (MEFV) has recently been cloned to chromosome
16p, which encodes pyrin. In the present study, we enrolled 2,067 unrelated patients with the suspicion of FMF in Middle Anatolia
between the years 2006–2009 and identified the 12 MEFV mutations. DNA was amplified by PCR and subjected to reverse hybridization
for the detection of MEFV gene mutations. Among the 2,067 patients, 866 (41.9%) were males and 1,201 (58.1%) were females.
The mutations were homozygous in 176 (16.85%) patients, compound heterozygous in 314 (30.1%) patients, heterozygous in 546
(52.25%) patients and the other forms of mutations were found in 8 patients (0.76%). No mutation was detected in 1,023 (49.5%)
patients. The most frequent mutations were M694V, M680I (G/C), E148Q and V726A. We could not find any significant differences
between the two common mutations according to the gender. The high incidence of MEFV gene mutations in the Turkish population
indicated that newborn screening may be discussed in the future. Because of the ethnic origin of Anatolia, larger serial analyses
are necessary to investigate the rate and coexistence of these mutations. 相似文献
96.
Age and growth of Alburnus tarichi (Güldenstädt, 1814): an endemic fish species of Lake Van (Turkey)
In total, 240 tarek, Alburnus tarichi, specimens were caught throughout February 2008 in Lake Van, Turkey, a lake with highly salty‐alkaline conditions. Ages, lengths and weights of A. tarichi were determined to estimate length–weight relationships and age composition. Otolith dimensions were also determined. Female : male ratio was 1.47 : 1. Fork length and total weight of specimens ranged from 14.3 to 19.2 cm and 45.76 to 99.63 g, respectively. Maximum age observed was 6 years. Length–weight relationships were calculated for female, male and combined sexes as, W = 0.057FL2.582W = 0.102FL2.513 W = 0.074FL2.544, respectively. Concerning types of growth, negative allometric growth (b < 3) was observed for all tarek specimens. The lagenar otolith was large and flat and marks on otoliths were typically clear, consistent and easy to interpret. Mean otolith length, breadth and weight were determined as 2.592 mm, 2.381 mm, 0.0026 g, respectively. While the otolith weight displayed a curvilinear relationship with the fork length, otolith length and breadth were linearly related to the fork length by height correlation coefficients. 相似文献
97.
Vedat Cinar Yahya Polat Abdulkerim Kasim Baltaci Rasim Mogulkoc 《Biological trace element research》2011,140(1):18-23
This study was performed to assess how 4 weeks of magnesium supplementation and exercise affect the free and total plasma
testosterone levels of sportsmen practicing tae kwon do and sedentary controls at rest and after exhaustion. The testosterone
levels were determined at four different periods: resting before supplementation, exhaustion before supplementation, resting
after supplementation, and exhaustion after supplementation in three study groups, which are as follows: Group 1—sedentary
controls supplemented with 10 mg magnesium per kilogram body weight. Group 2—tae kwon do athletes practicing 90–120 min/day
supplemented with 10 mg magnesium per kilogram body weight. Group 3—tae kwon do athletes practicing 90–120 min/day receiving
no magnesium supplements. The free plasma testosterone levels increased at exhaustion before and after supplementation compared
to resting levels. Exercise also increased testosterone levels relative to sedentary subjects. Similar increases were observed
for total testosterone. Our results show that supplementation with magnesium increases free and total testosterone values
in sedentary and in athletes. The increases are higher in those who exercise than in sedentary individuals. 相似文献
98.
Changes in essential trace elements and heavy metals may affect the atherosclerotic state of patients on maintenance hemodialysis (HD). The aim of the study was to evaluate the relation between the serum levels of some trace elements and heavy metals (iron, zinc, manganese, copper, magnesium, cobalt, cadmium, lead, and copper/zinc ratio) and carotid artery intima-media thickness (CIMT) in HD patients. Fifty chronic HD patients without known atherosclerotic disease and 48 age- and sex-matched healthy individuals were included in the study. The serum levels of trace elements (iron, zinc, manganese, copper, and magnesium) and heavy metals (cobalt, cadmium, and lead) were measured by Atomic Adsorption Spectrophotometer (UNICAM-929). CIMT was assessed by carotid artery ultrasonography. The serum levels of iron, zinc, and manganese were lower; levels of copper, magnesium, cobalt, cadmium, lead, and copper/zinc ratio were higher in HD patients compared to controls. CIMT in HD patients were higher than the control group (0.64?±?0.11 vs 0.42?±?0.05, p?0.001). There was a significant negative correlation between CIMT and serum levels of zinc (r?=?-0.70, p?0.01), iron (r?=?-0.71, p?0.01), and manganese (r?=?-0.47, p?0.01), while there was a significant positive correlation between CIMT and serum levels of copper (r?=?0.63, p?0.01), magnesium (r?=?0.77, p?0.01), cobalt (r?=?0.63, p?0.01), cadmium (r?=?0.48, p?0.01), lead (r?=?0.38, p?0.01), and copper/zinc ratio (r?=?0.68, p?0.01). A linear regression analysis showed that serum levels of magnesium, cadmium, lead, and copper/zinc ratio were still significantly and positively correlated with CIMT. We propose that copper/zinc ratio, magnesium and toxic metals cadmium and lead are independent determinants of CIMT in maintenance HD patients without known atherosclerotic disease. 相似文献
99.
The C-terminus of Protein Tyrosine Phosphatase 1B (PTP1B) includes an α-helix α7), which forms an allosteric binding site 20 ? away from the active site. This helix is specific to PTP1B and its truncation decreases the catalytic activity significantly. Here, molecular dynamics (MD) simulations in the presence and absence of α7 were performed to investigate the role played by α7. The highly mobile α7 was found to maintain its contacts with loop 11 (L11)α3 helix throughout the simulations. The interactions of Tyr152 on L11, Tyr176, Thr177 on the catalytically important WPD loop and Ser190 on α3 are important for the conformational stability and the concerted motions of the regions surrounding the WPD loop. In the absence of α7, L11 and WPD loop move away from their crystal structure conformations, resulting in the loss of the interactions in this region, and a decrease in the residue displacement correlations in the vicinity of WPD loop. Therefore, we suggest that one of the functionally important roles of α7 may be to limit the L11 and α3 motions, and, facilitate the WPD loop motions. Truncation of α7 in PTP1B is found to affect distant regions as well, such as the substrate recognition site and the phosphate binding-loop (P-loop), changing the conformations of these regions significantly. Our results show that the PTP1B specific α7 is important for the conformation and dynamics of the WPD loop, and also may play a role in ligand binding. 相似文献
100.