全文获取类型
收费全文 | 479篇 |
免费 | 27篇 |
国内免费 | 3篇 |
专业分类
509篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 30篇 |
2020年 | 24篇 |
2019年 | 61篇 |
2018年 | 34篇 |
2017年 | 26篇 |
2016年 | 32篇 |
2015年 | 26篇 |
2014年 | 33篇 |
2013年 | 49篇 |
2012年 | 48篇 |
2011年 | 33篇 |
2010年 | 18篇 |
2009年 | 11篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 2篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有509条查询结果,搜索用时 15 毫秒
461.
Chandirasegaran Massilamany Vahid Khalilzad-Sharghi Arunakumar Gangaplara David Steffen Shadi F. Othman Jay Reddy 《Journal of visualized experiments : JoVE》2014,(88)
Myocarditis is an inflammation of the myocardium, but only ~10% of those affected show clinical manifestations of the disease. To study the immune events of myocardial injuries, various mouse models of myocarditis have been widely used. This study involved experimental autoimmune myocarditis (EAM) induced with cardiac myosin heavy chain (Myhc)-α 334-352 in A/J mice; the affected animals develop lymphocytic myocarditis but with no apparent clinical signs. In this model, the utility of magnetic resonance microscopy (MRM) as a non-invasive modality to determine the cardiac structural and functional changes in animals immunized with Myhc-α 334-352 is shown. EAM and healthy mice were imaged using a 9.4 T (400 MHz) 89 mm vertical core bore scanner equipped with a 4 cm millipede radio-frequency imaging probe and 100 G/cm triple axis gradients. Cardiac images were acquired from anesthetized animals using a gradient-echo-based cine pulse sequence, and the animals were monitored by respiration and pulse oximetry. The analysis revealed an increase in the thickness of the ventricular wall in EAM mice, with a corresponding decrease in the interior diameter of ventricles, when compared with healthy mice. The data suggest that morphological and functional changes in the inflamed hearts can be non-invasively monitored by MRM in live animals. In conclusion, MRM offers an advantage of assessing the progression and regression of myocardial injuries in diseases caused by infectious agents, as well as response to therapies. 相似文献
462.
Species often exhibit different levels of genetic structuring correlated to their environment. However, understanding how environmental heterogeneity influences genetic variation is difficult because the effects of gene flow, drift and selection are confounded. We investigated the genetic variation and its ecological correlates in an endemic and critically endangered stream breeding mountain newt, Neurergus kaiseri, within its entire range in southwestern Iran. We identified two geographic regions based on phylogenetic relationships using Bayesian inference and maximum likelihood of 779 bp mtDNA (D-loop) in 111 individuals from ten of twelve known breeding populations. This analysis revealed a clear divergence between northern populations, located in more humid habitats at higher elevation, and southern populations, from drier habitats at lower elevations regions. From seven haplotypes found in these populations none was shared between the two regions. Analysis of molecular variance (AMOVA) of N. kaiseri indicates that 94.03% of sequence variation is distributed among newt populations and 5.97% within them. Moreover, a high degree of genetic subdivision, mainly attributable to the existence of significant variance among the two regions is shown (θCT = 0.94, P = 0.002). The positive and significant correlation between geographic and genetic distances (r = 0.61, P = 0.002) following controlling for environmental distance suggests an important influence of geographic divergence of the sites in shaping the genetic variation and may provide tools for a possible conservation based prioritization policy for the endangered species. 相似文献
463.
Three new species of the genus Caesarodispus (Acari: Microdispidae) associated with ants (Hymenoptera: Formicidae), with a key to species 下载免费PDF全文
Three new species of the genus Caesarodispus (Acari: Heterostigmatina: Microdispidae) phoretic on ants are described from Iran: C. khaustovi Rahiminejad & Hajiqanbar sp. nov. , C. pheidolei Rahiminejad & Hajiqanbar sp. nov. and C. nodijensis Rahiminejad & Hajiqanbar sp. nov. All species were associated with alate ants of the subfamily Myrmicinae (Hymenoptera: Formicidae) from northern Iran. A key to all species of Caesarodispus is provided. 相似文献
464.
Moghimifam Roya Niknam Vahid Ebrahimzadeh Hassan Hejazi Mohammad Amin 《Bioprocess and biosystems engineering》2020,43(9):1587-1597
Bioprocess and Biosystems Engineering - Global warming, as a result of atmospheric CO2 increase, is regarded as an important universal concern. Microalgae are considered as appropriate... 相似文献
465.
Maryam Abolghasemi Sadra Samavarchi Tehrani Tooba Yousefi Ansar Karimian Ata Mahmoodpoor Aliakbar Ghamari Farhad Jadidi-Niaragh Mehdi Yousefi Hossein Samadi Kafil Milad Bastami Mahdi Edalati Shirin Eyvazi Mohsen Naghizadeh Niloufar Targhazeh Bahman Yousefi Amin Safa Maryam Majidinia Vahid Rameshknia 《Journal of cellular physiology》2020,235(6):5008-5029
Breast cancer is one of the most lethal malignancies in women in the world. Various factors are involved in the development and promotion of the malignancy; most of them involve changes in the expression of certain genes, such as microRNAs (miRNAs). MiRNAs can regulate signaling pathways negatively or positively, thereby affecting tumorigenesis and various aspects of cancer progression, particularly breast cancer. Besides, accumulating data demonstrated that miRNAs are a novel tool for prognosis and diagnosis of breast cancer patients. Herein, we will review the roles of these RNA molecules in several important signaling pathways, such as transforming growth factor, Wnt, Notch, nuclear factor-κ B, phosphoinositide-3-kinase/Akt, and extracellular-signal-regulated kinase/mitogen activated protein kinase signaling pathways in breast cancer. 相似文献
466.
Background music is one of the most frequently encountered contextual factors that affect cognitive and emotional functions in humans. However, it is still unclear whether music induces similar effects in nonhuman primates. Answering this question might bring insight to the long‐lasting question regarding the ability of nonhuman primates in perceiving and dissociating music from other nonmusical acoustic information. In the present study, macaque monkeys were trained to perform a working memory task that required matching visual stimuli. These stimuli had different emotional content (neutral, negative, and positive). Monkeys performed the task within different background acoustic conditions (music, same‐intensity noise, and silence). We hypothesized that the auditory stimuli might interact with emotional information of visual stimuli and modulate monkeys’ performance. Furthermore, if the effects of music and noise on monkeys’ behavioral measures differ it would mean that monkeys perceived and processed music differently. We found that, monkeys committed more errors and were slower when they encountered stimuli with negative or positive emotional content. In the presence of music, the influence of emotional stimuli on monkeys’ performance significantly differed from those of the neutral stimuli, however, in the presence of noise, the effects of emotional stimuli on monkeys’ performance were not distinguishable. The dissociable effects of music and noise on monkeys’ performance show that the effects of emotional stimuli were dependent on the background acoustic conditions. Our findings indicate that background music and the same‐intensity noise were differentially perceived by monkeys and influenced their cognitive functions. 相似文献
467.
Inga Strodtkotter ;Kollipara Padmasree ;Challabathula Dinakar ;Birgit Speth ;Pamela S. Niazi ;Joanna Wojtera ;Ingo Voss ;Phuc Thi Do ;Adriano Nunes-Nesi ;Alisdair R. Fernie ;Vera Linke ;Agepati S. Raghavendra ;Renate Scheibe 《植物生理学报》2009,(2):284-297
Plant respiration is characterized by two pathways for electron transfer to O2, namely the cytochrome pathway (CP) that is linked to ATP production, and the alternative pathway (AP), where electrons from ubiquinol are directly transferred to O2 via an alternative oxidase (AOX) without concomitant ATP production. This latter pathway is well suited to dispose of excess electrons in the light, leading to optimized photosynthetic performance. We have characterized T- DNA-insertion mutant lines of Arabidopsis thaliana that do not express the major isoform, AOXIA. In standard growth conditions, these plants did not show any phenotype, but restriction of electron flow through CP by antimycin A, which induces AOXIA expression in the wild-type, led to an increased expression of AOXID in leaves of the aoxla-knockout mutant. Despite the increased presence of the AOX1D isoform in the mutant, antimycin A caused inhibition of photosyn- thesis, increased ROS, and ultimately resulted in amplified membrane leakage and necrosis when compared to the wild- type, which was only marginally affected by the inhibitor. It thus appears that AOX1 D was unable to fully compensate for the loss of AOXIA when electron flow via the CP is restricted. A combination of inhibition studies, coupled to metabolite profiling and targeted expression analysis of the P-protein of glycine decarboxylase complex (GDC), suggests that the aoxla mutants attempt to increase their capacity for photorespiration. However, given their deficiency, it is intriguing that increase in expression neither of AOX1D nor of GDC could fully compensate for the lack of AOXIA to optimize pho- tosynthesis when treated with antimycin A. We suggest that the aoxla mutants can further be used to substantiate the current models concerning the influence of mitochondrial redox on photosynthetic performance and gene expression. 相似文献
468.
V Tiziani E Reichenberger C L Buzzo S Niazi N Fukai M Stiller H Peters F M Salzano C M Raposo do Amaral B R Olsen 《American journal of human genetics》1999,65(1):158-166
Cherubism is an autosomal dominant disorder that may be related to tooth development and eruption. It is a disorder of age-related bone remodeling, mostly limited to the maxilla and the mandible, with loss of bone in the jaws and its replacement with large amounts of fibrous tissue. We have used a genomewide search with a three-generation family and have established linkage to chromosome 4p16. Three other families affected with cherubism were also genotyped and were mapped to the same locus. The combined LOD score is 4.21 at a recombination fraction of 0, and the locus spans an interval of approximately 22 cM. 相似文献
469.
Vahid Felehgari Zohreh Rahimi Hadi Mozafari Asad Vaisi-Raygani 《Molecular and cellular biochemistry》2011,346(1-2):23-30
There are controversial results related to the contribution of insertion (I)/deletion (D) polymorphism of the angiotensin I-converting enzyme (ACE) in the development of diabetic nephropathy. To assess the distribution of this polymorphism in diabetic patients with and without nephropathy we studied 140 unrelated type 2 diabetic patients from the Kermanshah Province of Iran with ethnic background of Kurds including 68 patients with macroalbuminuria and 72 normoalbuinuric diabetic patients as controls. Genotyping was done by polymerase chain reaction (PCR). The frequency of D allele in nephropathic and normoalbuminuric patients were 69.1 and 58.3%, respectively (P = 0.061). In individuals with DD genotype the risk of macroalbuminuria increased 2.87-fold (P = 0.057). Significant lower level of serum ACE activity was found in the normoalbuminuric (59.76 IU/l) compared to macroalbuminuric (97.43 IU/l) patients. The serum ACE activity was significantly higher in macroalbuminuric patients with ID (105.7 IU/l) and ID + DD (100.7 IU/l) genotypes compared to normoalbuminuric patients with the same genotypes (63.5 and 64.2 IU/l, respectively). Treatment with captopril significantly (P = 0.045) reduced the serum ACE activity in normoalbuminuric patients with DD genotype compared to macroalbuminuric patients with the same genotype (33.6 vs. 73.8 IU/l). However, the greatest benefit effect of losartan therapy on ACE activity was observed only in macroalbuminuric patients with DD genotype compared to that in normoalbuminuric patients (61.0 vs. 109.0 IU/l, P = 0.06). Our study suggests the importance of ethnic origin in the development of diabetic nephropathy and demonstrates different responses to therapy according to genotype and stage of diabetes. 相似文献
470.
Vahid Niknam Ali Akbar Meratan Seyed Mahmood Ghaffari 《In vitro cellular & developmental biology. Plant》2011,47(2):297-308
The changes in lipid peroxidation and the involvement of the antioxidant system in relation to salt stress tolerance were
investigated in the callus of Acanthophyllum glandulosum and Acanthophyllum sordidum. The callus was subjected to NaCl stress (50–200 mM) for 40 d. The callus of A. glandulosum was less sensitive to NaCl stress than that of A. sordidum. Increasing concentrations of NaCl from 50 to 200 mM correlated to increased proline content in A. glandulosum. Total protein content was higher in extracts of A. glandulosum than in extracts of A. sordidum under both control and salinity treatments. Compared with A. sordidum, lipid peroxidation and H2O2 content were lower and the activities of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), ascorbate
peroxidase, and glutathione reductase were higher in A. glandulosum under salt stress. Activity staining of antioxidant enzymes separated by native polyacrylamide gel electrophoresis (PAGE)
revealed that callus of A. sordidum had five Fe-SOD isoforms and one Mn-SOD isoform, all of which were reduced by salinity. In A. glandulosum, two Mn-SOD, three Fe-SOD, and one Cu/Zn-SOD isoforms were detected. Out of these six SOD isoforms, expression of the Mn-SOD
and Fe-SOD isoforms was enhanced at 100 mM and higher NaCl concentrations. Two and six GPX isoforms were detected in A. sordidum and A. glandulosum, respectively. Expression of the single CAT isoform in A. sordidum was preferentially reduced by salinity. In A. glandulosum, the two CAT isoforms showed differential down regulation under NaCl stress, with the CAT2 isoform detected only under control
condition. These results suggest that A. glandulosum callus is better protected against salinity-induced oxidative damage by maintaining higher activities of antioxidant enzymes
than the callus of A. sordidum. 相似文献