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   357篇
  免费   34篇
  2022年   6篇
  2021年   6篇
  2020年   5篇
  2019年   5篇
  2018年   6篇
  2017年   7篇
  2016年   7篇
  2015年   24篇
  2014年   24篇
  2013年   27篇
  2012年   34篇
  2011年   22篇
  2010年   16篇
  2009年   9篇
  2008年   9篇
  2007年   15篇
  2006年   8篇
  2005年   9篇
  2004年   10篇
  2003年   13篇
  2002年   6篇
  2001年   4篇
  2000年   4篇
  1999年   4篇
  1998年   2篇
  1996年   5篇
  1995年   4篇
  1994年   2篇
  1993年   2篇
  1992年   5篇
  1991年   6篇
  1990年   5篇
  1989年   4篇
  1988年   3篇
  1987年   5篇
  1986年   6篇
  1985年   9篇
  1984年   3篇
  1983年   3篇
  1981年   4篇
  1979年   5篇
  1978年   2篇
  1977年   4篇
  1974年   2篇
  1973年   3篇
  1972年   4篇
  1971年   2篇
  1966年   2篇
  1965年   2篇
  1919年   1篇
排序方式: 共有391条查询结果,搜索用时 833 毫秒
51.
One of the main characteristics of Autism Spectrum Disorder (ASD) are problems with social interaction and communication. Here, we explored ASD-related alterations in 'reading' body language of other humans. Accuracy and reaction times were assessed from two observational tasks involving the recognition of 'biological motion' and 'emotions' from point-light displays (PLDs). Eye movements were recorded during the completion of the tests. Results indicated that typically developed-participants were more accurate than ASD-subjects in recognizing biological motion or emotions from PLDs. No accuracy differences were revealed on two control-tasks (involving the indication of color-changes in the moving point-lights). Group differences in reaction times existed on all tasks, but effect sizes were higher for the biological and emotion recognition tasks. Biological motion recognition abilities were related to a person's ability to recognize emotions from PLDs. However, ASD-related atypicalities in emotion recognition could not entirely be attributed to more basic deficits in biological motion recognition, suggesting an additional ASD-specific deficit in recognizing the emotional dimension of the point light displays. Eye movements were assessed during the completion of tasks and results indicated that ASD-participants generally produced more saccades and shorter fixation-durations compared to the control-group. However, especially for emotion recognition, these altered eye movements were associated with reductions in task-performance.  相似文献   
52.
Little is known about mate choice preferences outside Western, educated, industrialised, rich and democratic societies, even though these Western populations may be particularly unrepresentative of human populations. To our knowledge, this is the first study to test which facial cues contribute to African perceptions of African female attractiveness and also the first study to test the combined role of facial adiposity, skin colour (lightness, yellowness and redness), skin homogeneity and youthfulness in the facial attractiveness preferences of any population. Results show that youthfulness, skin colour, skin homogeneity and facial adiposity significantly and independently predict attractiveness in female African faces. Younger, thinner women with a lighter, yellower skin colour and a more homogenous skin tone are considered more attractive. These findings provide a more global perspective on human mate choice and point to a universal role for these four facial cues in female facial attractiveness.  相似文献   
53.
Dendritic cells (DCs) are the quintessential antigen-presenting cells of the human immune system and play a prime role in coordinating innate and adaptive immune responses, explaining the strong and still growing interest in their application for cancer immunotherapy. Much current research in the field of DC-based immunotherapy focuses on optimizing the culture conditions for in vitro DC generation in order to assure that DCs with the best possible immunogenic qualities are being used for immunotherapy. In this context, monocyte-derived DCs that are alternatively induced by interleukin-15 (IL-15 DCs) have attracted recent attention due to their superior immunostimulatory characteristics. In this study, we show that IL-15 DCs, in addition to potent tumor antigen-presenting function, possess tumoricidal potential and thus qualify for the designation of killer DCs. Notwithstanding marked expression of the natural killer (NK) cell marker CD56 on a subset of IL-15 DCs, we found no evidence of a further phenotypic overlap between IL-15 DCs and NK cells. Allostimulation and antigen presentation assays confirmed that IL-15 DCs should be regarded as bona fide myeloid DCs not only from the phenotypic but also from the functional point of view. Concerning their cytotoxic activity, we demonstrate that IL-15 DCs are able to induce apoptotic cell death of the human K562 tumor cell line, while sparing tumor antigen-specific T cells. The cytotoxicity of IL-15 DCs is predominantly mediated by granzyme B and, to a small extent, by tumor necrosis factor-α (TNF-α)-related apoptosis-inducing ligand (TRAIL) but is independent of perforin, Fas ligand and TNF-α. In conclusion, our data provide evidence of a previously unappreciated role for IL-15 in the differentiation of human monocytes towards killer DCs. The observation that IL-15 DCs have killer DC capacity lends further support to their implementation in DC-based immunotherapy protocols.  相似文献   
54.
The prognosis of patients with acute myeloid leukemia (AML) remains dismal, with a 5-year overall survival rate of only 5.2% for the continuously growing subgroup of AML patients older than 65 years. These patients are generally not considered eligible for intensive chemotherapy and/or allogeneic hematopoietic stem cell transplantation because of high treatment-related morbidity and mortality, emphasizing the need for novel, less toxic, treatment alternatives. It is within this context that immunotherapy has gained attention in recent years. In this review, we focus on the use of dendritic cell (DC) vaccines for immunotherapy of AML. DC are central orchestrators of the immune system, bridging innate and adaptive immunity and critical to the induction of anti-leukemic immunity. We discuss the rationale and basic principles of DC-based therapy for AML and review the clinical experience that has been obtained so far with this form of immunotherapy for patients with AML.  相似文献   
55.
A microwave-assisted three-component one-pot cyclocondensation method was applied for the synthesis of novel N-(1-thia-4-azaspiro[4.5]decan-4-yl)carboxamide compounds carrying an adamantyl moiety. The structures of the compounds were confirmed by spectral and elemental analysis. All compounds were evaluated for antiviral activity against influenza A (H1N1 and H3N2) and influenza B virus in MDCK cell cultures. The compounds displayed a confined structure-activity relationship. The N-(2,8-dimethyl-3-oxo-1-thia-4-azaspiro[4.5]dec-4-yl)adamantane-1-carboxamide 3b was the most potent inhibitor [antiviral EC50: 1.4 μM against influenza A/H3N2 virus]. Its strong inhibitory effect in a virus hemolysis assay supports that 3b acts as an influenza virus fusion inhibitor by preventing the conformational change of the influenza virus hemagglutinin at low pH.  相似文献   
56.
Commensal symbionts, thought to be intermediary amid obligate mutualists and facultative parasites, offer insight into forces driving the evolutionary transition into mutualism. Using macroarrays developed for a close relative, Escherichia coli, we utilized a heterologous array hybridization approach to infer the genomic compositions of a clade of bacteria that have recently established symbiotic associations: Sodalis glossinidius with the tsetse fly (Diptera, Glossina spp.) and Sitophilus oryzae primary endosymbiont (SOPE) with the rice weevil (Coleoptera, Sitophilus oryzae). Functional biologies within their hosts currently reflect different forms of symbiotic associations. Their hosts, members of distant insect taxa, occupy distinct ecological niches and have evolved to survive on restricted diets of blood for tsetse and cereal for the rice weevil. Comparison of genome contents between the two microbes indicates statistically significant differences in the retention of genes involved in carbon compound catabolism, energy metabolism, fatty acid metabolism, and transport. The greatest reductions have occurred in carbon catabolism, membrane proteins, and cell structure-related genes for Sodalis and in genes involved in cellular processes (i.e., adaptations towards cellular conditions) for SOPE. Modifications in metabolic pathways, in the form of functional losses complementing particularities in host physiology and ecology, may have occurred upon initial entry from a free-living to a symbiotic state. It is possible that these adaptations, streamlining genomes, act to make a free-living state no longer feasible for the harnessed microbe.  相似文献   
57.
Metachromatic leukodystrophy (MLD) is a recessive autosomal disease which is biochemically characterized by an accumulation of sulfatides (sulfogalactosylceramides) mainly in oligodendrocytes and macrophages/microglia. The deficient enzyme is a lysosomal hydrolase, cerebroside sulfate sulfatase (arylsulfatase A). MLD is both a dysmyelinating and a demyelinating disease. The main clinical forms are infantile or juvenile, but some forms appear at adulthood. This disease involves also neuronal cells as sulfatides are also present in neurons in which the defect in degradation occurs also. We have studied 12 cases of adult MLD and clearly distinguished two clinical forms. One of them was characterized by mainly central nervous system motor signs (pyramidal, cerebellar, and seldom dystonia) and a peripheral neuropathy. The other form always started by behavioural abnormalities with modifications of mood, peculiar social reactions; a progressive mental deterioration occurred also. The diagnosis of schizophrenia was often mentioned. Most of these patients remained for many years without any neurological symptoms, and the diagnosis was only made when neurological signs appeared, or when Magnetic Resonance Imaging (MRI) was performed. MRI showed a diffuse demyelination, bilateral and often symmetrical, which could be temporarily limited to the periventricular areas. The diagnosis of adult MLD was biochemical, evidencing the low activity of arylsulfatase A (ASA) and sulfatide accumulation. To determine the respective participation of neurons and glial cells in the physiopathology of both the motor forms and the psycho-cognitive forms, our first approach was to search for mutations differing according to the clinical status. Motor forms involved the major adult ASA mutation P426L in a homozygote form in contrast to psycho-cognitive forms which involved as a compound heterozygote a specific I179S mutation.  相似文献   
58.
To better understand hypercoagulability as an underlying cause for thrombosis, the leading cause of death in the Western world, new assays to study ex vivo coagulation are essential. The zebrafish is generally accepted as a good model for human hemostasis and thrombosis, as the hemostatic system proved to be similar to that in man. Their small size however, has been a hurdle for more widespread use in hemostasis related research. In this study we developed a method that enables the measurement of thrombin generation in a single drop of non-anticoagulated zebrafish blood. Pre-treatment of the fish with inhibitors of FXa and thrombin, resulted in a dose dependent diminishing of thrombin generation, demonstrating the validity of the assay. In order to establish the relationship between whole blood thrombin generation and fibrin formation, we visualized the resulting fibrin network by scanning electron microscopy. Taken together, in this study we developed a fast and reliable method to measure thrombin generation in whole blood collected from a single zebrafish. Given the similarities between coagulation pathways of zebrafish and mammals, zebrafish may be an ideal animal model to determine the effect of novel therapeutics on thrombin generation. Additionally, because of the ease with which gene functions can be silenced, zebrafish may serve as a model organism for mechanistical research in thrombosis and hemostasis.  相似文献   
59.
60.
The quantitative differentiation of liposomal encapsulated and non-encapsulated drug tissue concentrations is desirable, since the efficacy and toxicity are only related to the level of non-encapsulated drug. However, such separate concentration profiles in tissues have still not been reported due to lacking analytical methodology. The encapsulation of prodrugs like prednisolone phosphate (PP) in liposomes offers new, analytical opportunities. Instantaneous dephosphorylation of PP into prednisolone (P) by phosphatases after its release from the liposome in vivo makes it possible to differentiate between the encapsulated and the non-encapsulated drug for such preparations of liposomal PP: PP represents the encapsulated drug, while P represents the non-encapsulated drug. In the here described study, the instantaneous dephosphorylation of PP by murine liver and kidney phosphatases has been verified by incubation of PP in liver and kidney homogenates followed by estimation of the dephosphorylation rate constants k and the dephosphorylation time of the expected maximal in vivo non-encapsulated drug concentrations. In vitro PP has been rapidly converted into P in the presence of homogenate from the excretory organs. The calculated values for k have shown that the liver contains more active sites per gram of tissue than the kidneys. However, the dephosphorylation of PP by these active sites is slower compared with the kidneys. Compared with other pharmacokinetic processes of P, the estimated dephosphorylation times of the expected maximal in vivo non-encapsulated drug concentrations in the liver and the kidneys are considered to be instantaneous. This enables the separate determination of the encapsulated and non-encapsulated drug concentrations in the excretory organs after administration of liposomal PP in mice generating the first pharmacokinetic profile of a liposomal preparation, in which the in vivo encapsulated and free drug tissues concentrations are measured separately. This can also gain important insights into the pharmacokinetics of liposomal formulations in general.  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