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991.
992.
Linte CA Wierzbicki M Peters TM Samani A 《Computer methods in biomechanics and biomedical engineering》2008,11(3):243-255
This work presents the initial development and implementation of a novel 3D biomechanics-based approach to measure the mechanical activity of myocardial tissue, as a potential non-invasive tool to assess myocardial function. This technique quantifies the myocardial contraction forces developed within the ventricular myofibers in response to electro-physiological stimuli. We provide a 3D finite element formulation of a contraction force reconstruction algorithm, along with its implementation using magnetic resonance (MR) data. Our algorithm is based on an inverse problem solution governed by the fundamental continuum mechanics principle of conservation of linear momentum, under a first-order approximation of elastic and isotropic material conditions. We implemented our technique using a subject-specific ventricle model obtained by extracting the left ventricular anatomical features from a set of high-resolution cardiac MR images acquired throughout the cardiac cycle using prospective electrocardiographic gating. Cardiac motion information was extracted by non-rigid registration of the mid-diastole reference image to the remaining images of a 4D dataset. Using our technique, we reconstructed dynamic maps that show the contraction force distribution superimposed onto the deformed ventricle model at each acquired frame in the cardiac cycle. Our next objective will consist of validating this technique by showing the correlation between the presence of low contraction force patterns and poor myocardial functionality. 相似文献
993.
Price AL Butler J Patterson N Capelli C Pascali VL Scarnicci F Ruiz-Linares A Groop L Saetta AA Korkolopoulou P Seligsohn U Waliszewska A Schirmer C Ardlie K Ramos A Nemesh J Arbeitman L Goldstein DB Reich D Hirschhorn JN 《PLoS genetics》2008,4(1):e236
European Americans are often treated as a homogeneous group, but in fact form a structured population due to historical immigration of diverse source populations. Discerning the ancestry of European Americans genotyped in association studies is important in order to prevent false-positive or false-negative associations due to population stratification and to identify genetic variants whose contribution to disease risk differs across European ancestries. Here, we investigate empirical patterns of population structure in European Americans, analyzing 4,198 samples from four genome-wide association studies to show that components roughly corresponding to northwest European, southeast European, and Ashkenazi Jewish ancestry are the main sources of European American population structure. Building on this insight, we constructed a panel of 300 validated markers that are highly informative for distinguishing these ancestries. We demonstrate that this panel of markers can be used to correct for stratification in association studies that do not generate dense genotype data. 相似文献
994.
Ceramide-induced formation of ROS and ATP depletion trigger necrosis in lymphoid cells 总被引:2,自引:0,他引:2
Villena J Henriquez M Torres V Moraga F Díaz-Elizondo J Arredondo C Chiong M Olea-Azar C Stutzin A Lavandero S Quest AF 《Free radical biology & medicine》2008,44(6):1146-1160
In lymphocytes, Fas activation leads to both apoptosis and necrosis, whereby the latter form of cell death is linked to delayed production of endogenous ceramide and is mimicked by exogenous administration of long- and short-chain ceramides. Here molecular events associated with noncanonical necrotic cell death downstream of ceramide were investigated in A20 B lymphoma and Jurkat T cells. Cell-permeable, C6-ceramide (C6), but not dihydro-C6-ceramide (DH-C6), induced necrosis in a time- and dose-dependent fashion. Rapid formation of reactive oxygen species (ROS) within 30 min of C6 addition detected by a dihydrorhodamine fluorescence assay, as well as by electron spin resonance, was accompanied by loss of mitochondrial membrane potential. The presence of N-acetylcysteine or ROS scavengers like Tiron, but not Trolox, attenuated ceramide-induced necrosis. Alternatively, adenovirus-mediated expression of catalase in A20 cells also attenuated cell necrosis but not apoptosis. Necrotic cell death observed following C6 exposure was associated with a pronounced decrease in ATP levels and Tiron significantly delayed ATP depletion in both A20 and Jurkat cells. Thus, apoptotic and necrotic death induced by ceramide in lymphocytes occurs via distinct mechanisms. Furthermore, ceramide-induced necrotic cell death is linked here to loss of mitochondrial membrane potential, production of ROS, and intracellular ATP depletion. 相似文献
995.
996.
Burkitt WI Pritchard C Arsene C Henrion A Bunk D O'Connor G 《Analytical biochemistry》2008,376(2):242-251
Here we present a demonstration of the proof of principle that absolute concentration of a protein within a mixture of other proteins can be measured with SI traceability. The method used was based on tryptic digestion of a protein followed by quantification using double exact matching isotope dilution mass spectrometry (IDMS) of the peptides released. To provide full SI traceability to measurements of protein concentration we demonstrated a method of SI traceable peptide quantification in which the peptide standards used were quantified by an amino acid analysis method that incorporated double exact matching IDMS and amino acid standards of known purity. The concentration of the protein was therefore determined based upon the concentration of tryptic peptides, which in turn had been quantified based upon amino acid standards. This allowed fully SI-traceable measurements of protein concentration to be made. Important caveats in the implementation of this approach are also discussed and examples of how these can have detrimental effects on the measurements are shown. 相似文献
997.
Background
Gene duplication provides opportunities for lineage diversification and evolution of developmental novelties. Duplicated genes generally either disappear by accumulation of mutations (nonfunctionalization), or are preserved either by the origin of positively selected functions in one or both duplicates (neofunctionalization), or by the partitioning of original gene subfunctions between the duplicates (subfunctionalization). The Pax2/5/8 family of important developmental regulators has undergone parallel expansion among chordate groups. After the divergence of urochordate and vertebrate lineages, two rounds of independent gene duplications resulted in the Pax2, Pax5, and Pax8 genes of most vertebrates (the sister group of the urochordates), and an additional duplication provided the pax2a and pax2b duplicates in teleost fish. Separate from the vertebrate genome expansions, a duplication also created two Pax2/5/8 genes in the common ancestor of ascidian and larvacean urochordates.Results
To better understand mechanisms underlying the evolution of duplicated genes, we investigated, in the larvacean urochordate Oikopleura dioica, the embryonic gene expression patterns of Pax2/5/8 paralogs. We compared the larvacean and ascidian expression patterns to infer modular subfunctions present in the single pre-duplication Pax2/5/8 gene of stem urochordates, and we compared vertebrate and urochordate expression to infer the suite of Pax2/5/8 gene subfunctions in the common ancestor of olfactores (vertebrates + urochordates). Expression pattern differences of larvacean and ascidian Pax2/5/8 orthologs in the endostyle, pharynx and hindgut suggest that some ancestral gene functions have been partitioned differently to the duplicates in the two urochordate lineages. Novel expression in the larvacean heart may have resulted from the neofunctionalization of a Pax2/5/8 gene in the urochordates. Expression of larvacean Pax2/5/8 in the endostyle, in sites of epithelial remodeling, and in sensory tissues evokes like functions of Pax2, Pax5 and Pax8 in vertebrate embryos, and may indicate ancient origins for these functions in the chordate common ancestor.Conclusion
Comparative analysis of expression patterns of chordate Pax2/5/8 duplicates, rooted on the single-copy Pax2/5/8 gene of amphioxus, whose lineage diverged basally among chordates, provides new insights into the evolution and development of the heart, thyroid, pharynx, stomodeum and placodes in chordates; supports the controversial conclusion that the atrial siphon of ascidians and the otic placode in vertebrates are homologous; and backs the notion that Pax2/5/8 functioned in ancestral chordates to engineer epithelial fusions and perforations, including gill slit openings. 相似文献998.
Cristian Gurzu Vlad Artenie Lucian Hritcu Alin Ciobica 《Central European Journal of Biology》2008,3(1):39-47
The high density of the steroid hormone receptors in the structures of temporal lobe involved in learning and memory, such
as the hippocampus, perirhinal cortex, entorhinal cortex and amigdaloid complex, shows that there must be a direct relationship
between gonadal hormones and organizational effects of steroid hormones in those structures during development of the nervous
system. The present study was undertaken in order to investigate the effect of testosterone administration during the third
week of gestation on the spatial memory formation of the offspring rats and the level of soluble proteins in the temporal
lobe and frontal lobe of brain, as evidence of important organizational effects of androgens during prenatal development in
brain sexual dimorphism. Animals have received testosterone undecanoate on days 14, 15, 16 and 19, 20, 21 of gestation. Learning
and memory tests were started 100 days after the testosterone treatment. At the end of the experiments, the temporal and frontal
lobes of brain were removed for assessing the level of soluble proteins. Testosterone treatment significantly improved spontaneous
alternations percentage of male offspring in Y-maze task comparative with female offspring and reference memory in radial
8 arm-maze task (decreasing in number of reference memory errors in both male and female offspring groups), suggesting effects
of both short and long-term memory. Also, testosterone significantly increased the brain soluble protein level of treated
female rats in 14–16 prenatal days compared with the control group as well as the brain soluble protein level of treated male
rats. These results suggest that steroid hormones play an important role in the spatial learning and memory formation by means
of protein synthesis in different lobes of the brain. 相似文献
999.
1000.
De La Fuente IM Martínez L Pérez-Samartín AL Ormaetxea L Amezaga C Vera-López A 《PloS one》2008,3(8):e3100