全文获取类型
收费全文 | 550篇 |
免费 | 34篇 |
国内免费 | 1篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 17篇 |
2016年 | 16篇 |
2015年 | 34篇 |
2014年 | 36篇 |
2013年 | 32篇 |
2012年 | 51篇 |
2011年 | 45篇 |
2010年 | 25篇 |
2009年 | 22篇 |
2008年 | 26篇 |
2007年 | 38篇 |
2006年 | 32篇 |
2005年 | 22篇 |
2004年 | 28篇 |
2003年 | 27篇 |
2002年 | 29篇 |
2001年 | 3篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有585条查询结果,搜索用时 156 毫秒
71.
Hilde Nybom Artur Mikiciński Larisa Garkava-Gustavsson Jasna Sehic Mariusz Lewandowski Piotr Sobiczewski 《Trees - Structure and Function》2012,26(1):199-213
Fire blight (Erwinia amylovora) causes serious damage to pome fruit orchards, and identification of germplasm with heritable disease resistance is therefore
crucial. Two dominant SCAR (sequence characterised amplified region) marker alleles (AE10-375 and GE-8019), flanking a previously
identified QTL (quantitative trait locus) for resistance to fire blight on ‘Fiesta’ linkage group 7 in apple cultivars related
to ‘Cox’s Orange Pippin’, were screened on 205 apple cultivars. Both marker alleles were present in 22% of the cultivars,
indicating presence of the QTL allele for tolerance, and both were lacking in 25%, indicating homozygosity for absence of
the QTL tolerance allele. However, 33% had only the marker allele AE10-375, while 20% had only GE-8019, suggesting that some
cultivars with the dominant alleles for both of the flanking markers can carry these on separate chromosomes and may lack
the QTL allele for tolerance. In 2009 and 2010, terminal shoots of greenhouse-grown grafted trees of 21 cultivars (only 20
in 2010) were inoculated with Erwinia amylovora. ‘Idared’ (susceptible) and ‘Enterprise’ (tolerant) were included as controls. Disease severity for each cultivar was expressed
as percentage of necrosis in relation to entire length of shoot, and the ranking of cultivars in 2009 and 2010 was compared
with a Spearman rank correlation test, P < 0.01. A relationship between presence of both flanking marker alleles for tolerance and level of fire blight tolerance
was confirmed with a Mann–Whitney U-test, P < 0.01 in 2009, and P < 0.05 in 2010. A PCO (principal coordinate) analysis based on band profiles obtained with 12 SSR (simple sequence repeat)
loci produced three loose clusters, two of which contained known offspring of ‘Cox’s Orange Pippin’, and one with cultivars
that were either unrelated or had an unknown origin. Cases where DNA markers did not predict level of fire blight damage as
expected, were, however, as common among descendants of ‘Cox’s Orange Pippin’ as among apparently unrelated cultivars. Obviously
the ‘Fiesta’ LG 7 QTL has some predictive value, both for known ‘Cox’ relatives and others, but more efficient markers would
be desirable for marker-assisted selection. 相似文献
72.
Bussenius J Anand NK Blazey CM Bowles OJ Bannen LC Chan DS Chen B Co EW Costanzo S DeFina SC Dubenko L Engst S Franzini M Huang P Jammalamadaka V Khoury RG Kim MH Klein RR Laird D Le DT Mac MB Matthews DJ Markby D Miller N Nuss JM Parks JJ Tsang TH Tsuhako AL Wang Y Xu W Rice KD 《Bioorganic & medicinal chemistry letters》2012,22(6):2283-2286
73.
A one-step synthesis of a curcumin-derived hydrogel (curcumin content of 25-75 mol %) is reported. Curcumin is incorporated into the hydrogel backbone and cross-linked through biodegradable carbonate linkages. Curcumin as a part of the polymer backbone is protected from oxidation and degradation, while hydrogel hydrolysis results in the release of active curcumin. Nontoxic poly(ethylene glycol) and desaminotyrosyl-tyrosine ethyl ester are used to tune the hydrophilic/hydrophobic hydrogel properties. In this way, hydrogels with a wide range of physical properties including water-uptake (100-550%) and compression moduli (7-100 kPa) were obtained. Curcumin release is swelling-controlled and could be extended to 80 days. In vitro, curcumin-derived hydrogels showed selective cytotoxicity against MDA-MB-231 (IC(50) 9 μM) breast cancer cells but no cytotoxicity to noncancerous quiescent human dermal fibroblasts even at high curcumin concentrations (160 μM). One possible application of these curcumin-derived hydrogels is as soft tissue filler after surgical removal of cancerous tissue. 相似文献
74.
AH Buschmann A Tomova A López MA Maldonado LA Henríquez L Ivanova F Moy HP Godfrey FC Cabello 《PloS one》2012,7(8):e42724
Antimicrobials used in salmon aquaculture pass into the marine environment. This could have negative impacts on marine environmental biodiversity, and on terrestrial animal and human health as a result of selection for bacteria containing antimicrobial resistance genes. We therefore measured the numbers of culturable bacteria and antimicrobial-resistant bacteria in marine sediments in the Calbuco Archipelago, Chile, over 12-month period at a salmon aquaculture site approximately 20 m from a salmon farm and at a control site 8 km distant without observable aquaculture activities. Three antimicrobials extensively used in Chilean salmon aquaculture (oxytetracycline, oxolinic acid, and florfenicol) were studied. Although none of these antimicrobials was detected in sediments from either site, traces of flumequine, a fluoroquinolone antimicrobial also widely used in Chile, were present in sediments from both sites during this period. There were significant increases in bacterial numbers and antimicrobial-resistant fractions to oxytetracycline, oxolinic acid, and florfenicol in sediments from the aquaculture site compared to those from the control site. Interestingly, there were similar numbers of presumably plasmid-mediated resistance genes for oxytetracycline, oxolinic acid and florfenicol in unselected marine bacteria isolated from both aquaculture and control sites. These preliminary findings in one location may suggest that the current use of large amounts of antimicrobials in Chilean aquaculture has the potential to select for antimicrobial-resistant bacteria in marine sediments. 相似文献
75.
U Bashir Aamir N Badar MR Mehmood N Nisar RM Suleman S Shaukat S Sharif J Kamran SS Zaidi BM Kazi L Gubareva X Xu R Garten A Klimov 《PloS one》2012,7(8):e41866
Background
In early 2009, a novel influenza A(H1N1) virus that emerged in Mexico and United States rapidly disseminated worldwide. The spread of this virus caused considerable morbidity with over 18000 recorded deaths. The new virus was found to be a reassortant containing gene segments from human, avian and swine influenza viruses.Methods/Results
The first case of human infection with A(H1N1)pdm09 in Pakistan was detected on 18th June 2009. Since then, 262 laboratory-confirmed cases have been detected during various outbreaks with 29 deaths (as of 31st August 2010). The peak of the epidemic was observed in December with over 51% of total respiratory cases positive for influenza. Representative isolates from Pakistan viruses were sequenced and analyzed antigenically. Sequence analysis of genes coding for surface glycoproteins HA and NA showed high degree of high levels of sequence identity with corresponding genes of regional viruses circulating South East Asia. All tested viruses were sensitive to Oseltamivir in the Neuraminidase Inhibition assays.Conclusions
Influenza A(H1N1)pdm09 viruses from Pakistan form a homogenous group of viruses. Their HA genes belong to clade 7 and show antigenic profile similar to the vaccine strain A/California/07/2009. These isolates do not show any amino acid changes indicative of high pathogenicity and virulence. It is imperative to continue monitoring of these viruses for identification of potential variants of high virulence or drug resistance. 相似文献76.
Larisa Chaustova Valė Miliukienė Aurelijus Zimkus Valdemaras Razumas 《Central European Journal of Biology》2008,3(4):417-421
The transformation efficiency of yeast cells during exponential growth might be characterised as undulatory. The aim of the
study was to investigate the reason for the fluctuation in transformation efficiency of yeast Saccharomyces cerevisiae p63-DC5 cells during exponential growth. The heightened response to exogenous DNA was observed with the growing yeast culture
when budded cells were predominant. To confirm this phenomenon we carried out synchronization of yeast cells with 10 mM hydroxyurea.
Results showed that synchronous yeast cells in the S-phase of cell cycle have enhanced transformation efficiency. Furthermore,
S. cerevisiae p63-DC5 cells in the S-phase were successfully transformed with plasmid pl13 in the absence of lithium acetate. We indicated
that the permeability of yeast cells in the S-phase to tetraphenylphosphonium (TPP) cations was significantly higher than
in asynchronous culture. The results of our study showed that the fluctuation in transformation efficiency was strictly dependent
on the metabolic state of yeast cells and the capacity of the yeast cells to become competent was related to the S-phase of
cell cycle. 相似文献
77.
Peter V. Oudemans Larisa Pozdnyakova Marilyn G. Hughes Faiz Rahman 《Journal of nematology》2002,34(3):207-212
The primary goal of our research is to develop key elements of a precision agriculture program applicable to high-value woody perennial crops, such as cranberries. These crop systems exhibit tremendous variability in crop yields and quality as imposed by variations in soil properties (water availability and nutrient deficiency) that lead to crop stress (disease development and weed competition). Some of the variability present in the growing environment results in persistent yield losses as well as crop-quality reductions. We are using state-of-the-art methodologies (GIS, GPS, remote sensing) to identify and map spatial variations of the crop. Through image-processing methods (NDVI and unsupervised classification), approximately 65% of the variation in yield was described using 4-m multispectral satellite data as a base image. 相似文献
78.
79.
Larisa A. Doguzhaeva Herbert Summesberger Harry Mutvei Franz Brandstaetter 《Palaeoworld》2007,16(4):272-284
Fragmentarily preserved shells – mainly pro-ostraca, in several cases also phragmocones – occurring together with arm hooks and the ink sac of the Carnian (Late Triassic) coleoid cephalopod Phragmoteuthis bisinuata (Bronn) from Lunz (Austria) are examined with the scanning electron microscope and energy-dispersive spectrometer. The pro-ostracum bears black, shiny, pitch-like sheets. The black sheets, the ink sac content and the arm hooks have a granular ultrastructure of 0.1–1 μm grain size. The arm hooks and black sheets are micro-laminated; each lamina consists of fibres. The ink consists of an agglomerate of grains. On the ventral (internal) side of the pro-ostracum, the black sheets occasionally bear agglomerates of homogeneous, ink-like material along with heterogeneous structures. The pro-ostracum has crystal-shaped units with lamello-columnar ultrastructure of the inner layer and plate ultrastructure of the outer layer. This resembles the Late Triassic Lunzoteuthis [Doguzhaeva, L.A., Mutvei, H., Summesberger, H., 2005a. A Late Triassic coleoid from the Austrian Alps: the pro-ostracum viewpoint. In: Kostak, M., Marek, J. (Eds.), Proceedings of the 2nd International Symposium on Coleoid Cephalopods Through Time. Short Papers/Abstracts Vol. Prague, 26–29 September, 2005, pp. 55–59] and Early Jurassic Belemnotheutis [Doguzhaeva, L.A., Donovan, D.T., Mutvei, H., 2005b. The rostrum, conotheca and pro-ostracum in the Jurassic coleoid Belemnotheutis Pearce from Wiltshire, England. In: Kostak, M., Marek, J. (Eds.), Proceedings of the 2nd International Symposium on Coleoid Cephalopods Through Time. Short Papers/Abstracts Vol. Prague, 26–29 September, 2005, pp. 45–49]. The black sheets, the material on their inner surface, the ink and the arm hooks consist of carbon, occasionally with minor amounts of sulfur. The shell is of calcium carbonate.Based on their organic composition, position in the shell and lamello-fibrillar ultrastructure, the black sheets are considered to be remains of the mantle, sometimes with ink sac and soft body debris. The carbon composition and granular ultrastructure of arm hooks, ink, and soft tissue remains indicate that the non-mineralized structures are pseudomorphosed by carbon (carbonization), possibly due to C-accumulating bacteria. 相似文献
80.