全文获取类型
收费全文 | 92篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
102篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 8篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1969年 | 2篇 |
排序方式: 共有102条查询结果,搜索用时 15 毫秒
1.
2.
3.
微生物多样性对土壤氮磷钾转化、酶活性及油菜生长的影响 总被引:8,自引:0,他引:8
采用灭菌土壤分别接种不同稀释倍数(1、10~(-2)、10~(-4)和10~(-6))未灭菌土壤悬浊液的方法,研究了土壤微生物多样性降低对油菜生长和养分吸收、土壤养分有效性和酶活性的影响。结果表明:(1)随着接种土壤悬浊液稀释倍数增加,油菜生物量逐渐降低,10-4的油菜生物量显著低于1和10~(-2),10~(-6)仅为1的26%;(2)油菜氮、磷和钾的吸收量与油菜生物量呈现相同的变化规律;(3)土壤铵态氮浓度随接种土壤悬浊液稀释倍数增加而降低;而土壤硝态氮则以10~(-4)为最高,其它处理间没有显著差异;土壤有效磷未发生显著变化;有效钾反而有上升趋势;(4)土壤多酚氧化酶(PhO X)活性随接种土壤悬浊液稀释倍数增加逐渐升高;β-1,4-葡萄糖苷酶(βG)活性以10~(-6)为最高,而其它处理差异不显著;土壤亮氨酸酶氨肽酶(LAP)活性和酸性磷酸酶(AP)活性变化不显著;(5)相关分析表明,油菜生物量与土壤铵态氮浓度的对数显著正相关;与多酚氧化酶、葡萄糖苷酶和亮氨酸氨肽酶活性显著负相关。研究表明,微生物多样性降低主要通过抑制土壤氮素释放影响植物生长。 相似文献
4.
5.
Andrew T. Taylor Thomas Hafen Colt T. Holley Alin Gonzlez James M. Long 《Ecology and evolution》2020,10(2):705-717
Leveraging existing presence records and geospatial datasets, species distribution modeling has been widely applied to informing species conservation and restoration efforts. Maxent is one of the most popular modeling algorithms, yet recent research has demonstrated Maxent models are vulnerable to prediction errors related to spatial sampling bias and model complexity. Despite elevated rates of biodiversity imperilment in stream ecosystems, the application of Maxent models to stream networks has lagged, as has the availability of tools to address potential sources of error and calculate model evaluation metrics when modeling in nonraster environments (such as stream networks). Herein, we use Maxent and customized R code to estimate the potential distribution of paddlefish (Polyodon spathula) at a stream‐segment level within the Arkansas River basin, USA, while accounting for potential spatial sampling bias and model complexity. Filtering the presence data appeared to adequately remove an eastward, large‐river sampling bias that was evident within the unfiltered presence dataset. In particular, our novel riverscape filter provided a repeatable means of obtaining a relatively even coverage of presence data among watersheds and streams of varying sizes. The greatest differences in estimated distributions were observed among models constructed with default versus AICC‐selected parameterization. Although all models had similarly high performance and evaluation metrics, the AICC‐selected models were more inclusive of westward‐situated and smaller, headwater streams. Overall, our results solidified the importance of accounting for model complexity and spatial sampling bias in SDMs constructed within stream networks and provided a roadmap for future paddlefish restoration efforts in the study area. 相似文献
6.
Ion-Nedelcu N Velea L Ulmeanu V Dragomirescu C Dumitrache-Marian R Gherasim P Iordăchescu C Mihailovici R Radu L 《Roumanian archives of microbiology and immunology》2001,60(1):55-67
The main objective of the study was to calculate and report the prevalence of probable risk factors involved in the transmission of pathogenic agents among type B and C acute viral hepatitis cases confirmed in Bucharest (1998-2000). The standardized values of the risks detected in the 45-180 days preceding the onset of illness suggest that in both types of acute viral hepatitis considered in our study transmission associated to the individuals' behaviour (19.0%-hepatitis B and 20.1%-hepatitis C) seems more frequent than "iatrogenic" transmission; in case of hepatitis B, sexual contacts with more than one partner coming first (15.7%), whilst in case of hepatitis C the use of i.v. drugs (heroine) was most frequently incriminated (12.4%). The study reviews the present knowledge of the risk factors involved in the transmission of the disease and approaches prevention strategies. 相似文献
7.
The carboxy-terminal fragment of nucleolin interacts with the nucleocapsid domain of retroviral gag proteins and inhibits virion assembly
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A yeast two-hybrid screen for cellular proteins that interact with the murine leukemia virus (MuLV) Gag protein resulted in the identification of nucleolin, a host protein known to function in ribosome assembly. The interacting fusions contained the carboxy-terminal 212 amino acids of nucleolin [Nuc(212)]. The nucleocapsid (NC) portion of Gag was necessary and sufficient to mediate the binding to Nuc(212). The interaction of Gag with Nuc(212) could be demonstrated in vitro and was manifested in vivo by the NC-dependent incorporation of Nuc(212) inside MuLV virions. Overexpression of Nuc(212), but not full-length nucleolin, potently and specifically blocked MuLV virion assembly and/or release. A mutant of MuLV, selected to specifically disrupt the binding to Nuc(212), was found to be severely defective for virion assembly. This mutant harbors a single point mutation in capsid (CA) adjacent to the CA-NC junction, suggesting a role for this region in Moloney MuLV assembly. These experiments demonstrate that selection for proteins that bind assembly domain(s) can yield potent inhibitors of virion assembly. These experiments also raise the possibility that a nucleolin-Gag interaction may be involved in virion assembly. 相似文献
8.
Alin M. Puinean Stephen P. Foster Linda Oliphant Ian Denholm Linda M. Field Neil S. Millar Martin S. Williamson Chris Bass 《PLoS genetics》2010,6(6)
The aphid Myzus persicae is a globally significant crop pest that has evolved high levels of resistance to almost all classes of insecticide. To date, the neonicotinoids, an economically important class of insecticides that target nicotinic acetylcholine receptors (nAChRs), have remained an effective control measure; however, recent reports of resistance in M. persicae represent a threat to the long-term efficacy of this chemical class. In this study, the mechanisms underlying resistance to the neonicotinoid insecticides were investigated using biological, biochemical, and genomic approaches. Bioassays on a resistant M. persicae clone (5191A) suggested that P450-mediated detoxification plays a primary role in resistance, although additional mechanism(s) may also contribute. Microarray analysis, using an array populated with probes corresponding to all known detoxification genes in M. persicae, revealed constitutive over-expression (22-fold) of a single P450 gene (CYP6CY3); and quantitative PCR showed that the over-expression is due, at least in part, to gene amplification. This is the first report of a P450 gene amplification event associated with insecticide resistance in an agriculturally important insect pest. The microarray analysis also showed over-expression of several gene sequences that encode cuticular proteins (2–16-fold), and artificial feeding assays and in vivo penetration assays using radiolabeled insecticide provided direct evidence of a role for reduced cuticular penetration in neonicotinoid resistance. Conversely, receptor radioligand binding studies and nucleotide sequencing of nAChR subunit genes suggest that target-site changes are unlikely to contribute to resistance to neonicotinoid insecticides in M. persicae. 相似文献
9.
10.
Robert Gradinaru Alin Ionas Aurel Pui Gheorghita Zbancioc Gabi Drochioiu 《Biometals》2011,24(6):1115-1121
Sulfur containing biomolecules are involved in complexes with mercury. CoA is an important cofactor for many enzymes involved in metabolic processes. Fatty acyl-CoA-thioesters, substrates of mitochondrial ß-oxidation, are sulfur containing compounds and potential mercury ligands. The CoA-Hg2+ complex can be easily assessed by UV-Vis spectroscopy or indirectly by antibacterial tests that reconfirmed the protective role of CoA on E. coli. The characteristics of these complexes were determined by means of FTIR spectroscopy. The reverse phase liquid chromatography combined with electrospray ionization tandem mass spectrometry was used for detection of the side-product that resulted through the cleavage of thioesters in the presence of mercury. An unexpected result was the detection of octathioic acid as a product. Our study shows that mitochondrial β-oxidation can be affected by thioesters depletion assisted by Hg2+. The GC-MS technique could be used to detect some possible mitochondrial injuries due to the heavy metal ions. 相似文献