全文获取类型
收费全文 | 125篇 |
免费 | 12篇 |
国内免费 | 3篇 |
专业分类
140篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 3篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 1篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1966年 | 1篇 |
1955年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有140条查询结果,搜索用时 15 毫秒
1.
2.
While long-term fixation and storage of specimens is common and useful for many research projects, it is particularly important for space flight investigations where samples may not be returned to Earth for several months (International Space Station) or years (manned mission to Mars). We examined two critical challenges of space flight experimentation: the effect of long-term fixation on the quality of mouse bone preservation and the preservation of antigens and enzymes for both histochemical and immunohistochemical analyses, and how the animal/sample processing affects the preservation. We show that long-term fixation minimally affects standard histological staining, but that enzyme histochemistry and immunolabeling are greatly compromised. Further, we demonstrate that whole animal preservation is not as suitable as whole leg or stripped leg preservation for long-term fixation and all histological analyses. Overall, we recommend whole leg processing for long-term storage of bone specimens in fixative prior to embedding in plastic for histological examination. 相似文献
3.
4.
MARTIN CLÉMENT CAROLINE CHAMBERLAND JACQUELINE PÉRODIN RICHARD LEDUC GAÉTAN GUILLEMETTE EMANUEL ESCHER 《Journal of receptor and signal transduction research》2013,33(5-6):417-433
Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT1)1 receptor mutant N111G-hAT1 which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT1 receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT1 series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form. 相似文献
5.
Vesna Gagic Laura GA Riggi Barbara Ekbom Gerard Malsher Adrien Rusch Riccardo Bommarco 《Ecology and evolution》2016,6(7):2149-2157
Loss in seed yield and therefore decrease in plant fitness due to simultaneous attacks by multiple herbivores is not necessarily additive, as demonstrated in evolutionary studies on wild plants. However, it is not clear how this transfers to crop plants that grow in very different conditions compared to wild plants. Nevertheless, loss in crop seed yield caused by any single pest is most often studied in isolation although crop plants are attacked by many pests that can cause substantial yield losses. This is especially important for crops able to compensate and even overcompensate for the damage. We investigated the interactive impacts on crop yield of four insect pests attacking different plant parts at different times during the cropping season. In 15 oilseed rape fields in Sweden, we estimated the damage caused by seed and stem weevils, pollen beetles, and pod midges. Pest pressure varied drastically among fields with very low correlation among pests, allowing us to explore interactive impacts on yield from attacks by multiple species. The plant damage caused by each pest species individually had, as expected, either no, or a negative impact on seed yield and the strongest negative effect was caused by pollen beetles. However, seed yield increased when plant damage caused by both seed and stem weevils was high, presumably due to the joint plant compensatory reaction to insect attack leading to overcompensation. Hence, attacks by several pests can change the impact on yield of individual pest species. Economic thresholds based on single species, on which pest management decisions currently rely, may therefore result in economically suboptimal choices being made and unnecessary excessive use of insecticides. 相似文献
6.
7.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
相似文献
8.
目的:探讨急性心肌梗死患者冠脉搭桥(CABG)术前中性粒细胞.淋巴细胞比率(NLR)与围术期心肌损伤的关系,为,临床CABG围术期心肌保护提供参考依据。方法:选取2012年1月至2012年6月于首都医科大学附属北京安贞医院因急性心肌梗死接受冠脉搭桥手术(CABG)患者210例,收集术前血常规及术后肌钙蛋白I(cTnI)?Life酸激酶同工酶(CK-MB),计算NLR;采用四分位法根据NLR水平将患者分为四组,比较各组cTnI及CK—MB峰值,多元逐步回归分析NLR与cTnI及CK-MB峰值的相关性。结果:随着NLR水平升高,高血压病史和射血分数〈50%患者比例逐渐增多;白细胞计数、术后CK-MB及cTnI峰值、术后血肌酐值均逐渐增加;多元逐步回归分析显示,NLR、WBC分别与cTnI峰值呈正相关(r=0.526,r=0.186,P〈0.05)。结论:术前NLR、WBC与cTnI峰值呈正相关,NLR可能是反应急性心肌梗死患者冠脉搭桥围术期心肌损伤的良好标志物。 相似文献
9.
Objectives To explore whether the angiotensin T -converting enzyme (ACE) I/D (insertion/ deletion) polymorphism is associated with the susceptibility to high altitude pulmonary edema (HAPE) in the Han Chinese. Methods One hundred and forty-seven HAPE-p (HAPE patients) and 193 HAPE-r (HAPE resistants) were enrolled from the Yushu earthquake reconstruction workers in Qinghai province where the altitude is over 3 500 m above sea level. Blood samples were collected from each of the HAPE-p and HAPE-r groups. Information about physiological phenotypes was obtained via fieldwork investigation. The ACE-I/D polymorphism in HAPE-p and HAPE-r was detected by polymerase chain reaction (PCR). Results The SaO2 was significantly lower while HR was significantly higher in HAPE-p group than those in HAPE-r group. The genotype frequencies of ACE-I/D for II, ID, DD in HAPE-r and HAPE-p groups were 0.430, 0.446, 0.124 and 0.435, 0.469, 0.095, respectively, the allelic frequencies of I and D were 0.650, 0.350 and 0.670, 0.330, respectively. The OR of ID, DD and D alleles relative to II for HAPE was 0.961 (0.610-1.514), 1.322 (0.634-2.758) and 1.080 (0.783-1.489). There was no significant difference of the genotypic and the allelic frequencies in ACE-I/D polymorphism between HAPE-p and HAPE-r groups. Conclusions There is no relation between ACE-I/D polymorphism and HAPE in the Han Chinese. 相似文献
10.
Philippe-Alexandre Gilbert Lacrimioara Comanita John Barrett Andrew Peters Marta Szabat Grant McFadden Gregory A. Dekaban 《Cytotechnology》2005,48(1-3):79-88
In light of the recent detection of BSE in North America and its endemic nature in other regions of the world, there is a
real need to employ cell culture conditions that do not require any animal-derived material. Here we report the use of an
ultra-low protein serum-free medium (VP-SFM, Invitrogen) for the amplification of poxviruses in primary chicken embryo fibroblasts
(CEF). We compared the amplification of four different poxviruses (canarypox, modified Ankara Virus (MVA), vaccinia virus
strain Copenhagen and myxoma strain Lausanne) in three different media: DMEM 10%, DMEM 2% and serum-free medium VP-SFM. VP-SFM
is a serum-free, ultra-low protein medium containing no proteins or peptides of human or animal origin designed to support
the replication of viruses and the production of recombinant proteins and monoclonal antibodies. Our results show that high
titre poxvirus stocks can be prepared in VP-SFM equivalent to that prepared in serum containing medium. 相似文献