全文获取类型
收费全文 | 1870篇 |
免费 | 100篇 |
专业分类
1970篇 |
出版年
2023年 | 11篇 |
2022年 | 21篇 |
2021年 | 52篇 |
2020年 | 30篇 |
2019年 | 40篇 |
2018年 | 61篇 |
2017年 | 57篇 |
2016年 | 86篇 |
2015年 | 105篇 |
2014年 | 142篇 |
2013年 | 136篇 |
2012年 | 183篇 |
2011年 | 176篇 |
2010年 | 90篇 |
2009年 | 73篇 |
2008年 | 94篇 |
2007年 | 81篇 |
2006年 | 83篇 |
2005年 | 72篇 |
2004年 | 59篇 |
2003年 | 53篇 |
2002年 | 43篇 |
2001年 | 17篇 |
2000年 | 24篇 |
1999年 | 21篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1967年 | 3篇 |
1966年 | 5篇 |
1957年 | 2篇 |
排序方式: 共有1970条查询结果,搜索用时 10 毫秒
111.
Gorodkin J Cirera S Hedegaard J Gilchrist MJ Panitz F Jørgensen C Scheibye-Knudsen K Arvin T Lumholdt S Sawera M Green T Nielsen BJ Havgaard JH Rosenkilde C Wang J Li H Li R Liu B Hu S Dong W Li W Yu J Wang J Staefeldt HH Wernersson R Madsen LB Thomsen B Hornshøj H Bujie Z Wang X Wang X Bolund L Brunak S Yang H Bendixen C Fredholm M 《Genome biology》2007,8(4):R45-16
112.
Eric?Roberto?Guimar?es?Rocha Aguiar Roenick Proveti Olmo Simona Paro Flavia Viana Ferreira Isaque?Jo?o?da?Silva de?Faria Yaovi?Mathias?Honore Todjro Francisco Pereira Lobo Erna Geessien Kroon Carine Meignin Derek Gatherer Jean-Luc Imler Jo?o Trindade Marques 《Nucleic acids research》2015,43(13):6191-6206
Virus surveillance in vector insects is potentially of great benefit to public health. Large-scale sequencing of small and long RNAs has previously been used to detect viruses, but without any formal comparison of different strategies. Furthermore, the identification of viral sequences largely depends on similarity searches against reference databases. Here, we developed a sequence-independent strategy based on virus-derived small RNAs produced by the host response, such as the RNA interference pathway. In insects, we compared sequences of small and long RNAs, demonstrating that viral sequences are enriched in the small RNA fraction. We also noted that the small RNA size profile is a unique signature for each virus and can be used to identify novel viral sequences without known relatives in reference databases. Using this strategy, we characterized six novel viruses in the viromes of laboratory fruit flies and wild populations of two insect vectors: mosquitoes and sandflies. We also show that the small RNA profile could be used to infer viral tropism for ovaries among other aspects of virus biology. Additionally, our results suggest that virus detection utilizing small RNAs can also be applied to vertebrates, although not as efficiently as to plants and insects. 相似文献
113.
The encapsulated fungus Cryptococcus neoformans is a common cause of life-threatening disease in immunocompromised individuals. Its major virulence determinant is the polysaccharide (PS) capsule. An unsolved problem in cryptococcal biology is whether the PSs composing the capsule are linear or complex branched polymers, as well as the implications of this structural composition in pathogenesis. In this study we approached the problem by combining static and dynamic light scattering, viscosity analysis, and high-resolution microscopy and correlated the findings with biological properties. Analysis of the dependence of capsular PS molecular mass and the radius of gyration provided strong evidence against a simple linear PS configuration. Shape factors calculated from light scattering measurements in solution revealed values consistent with polymer branching. Furthermore, viscosity measurements provided complementary evidence for structural branching. Electron microscopy showed PS spherical-like structures similar to other branched PS. Finally, we show that the capacity of capsular PS to interfere in complement-mediated phagocytosis, inhibit nitric oxide production by macrophage-like cells, protect against reactive oxygen species, antibody reactivity and half-life in serum were influenced by the degree of branching, providing evidence for the notion that PS branching is an important parameter in determining the biological activity of C. neoformans PS. 相似文献
114.
Milena R. Martelli Fran?ois Brygo Philippe Delaporte Xavier Rouau C??cile Barron 《Food biophysics》2011,6(4):433-439
During the wheat milling process, the bran fractionation is related to its mechanical properties, which are measured using
tensile tests on hand-isolated tissues. However, the dissection of wheat tissues implies a soaking stage in water that can
modify tissue properties. New methodologies are required to evaluate wheat tissue properties directly on native grains. The
aim of this work was to estimate wheat grain tissue cohesion by the ionization effectiveness via laser-induced breakdown spectroscopy
(LIBS) technique. Isolated bran tissues and wheat grains were submitted to LIBS analysis using a pulsed argon fluoride (193 nm,
15 ns, 1 Hz, 2 J cm−2) excimer laser and a compact optic fiber spectrometer (HR2000). The first approach was to correlate the ratios of ionic to
atomic emission lines (MgII/MgI and CaII/CaI) of isolated tissues to their mechanical measurements. The energy needed to rupture
the tissue was correlated to MgII/MgI (R
2 = 0.72). Secondly, native grains were irradiated and chemometrics was applied to discriminate tissue spectra. The aleurone
layer isolated after the soaking step presented a higher MgII/MgI than the aleurone layer from native grains, indicating a
possible water effect on the tissue cohesion. In conclusion, the LIBS technique may be a potential method for rapid structural
analysis of vegetal material allowing wheat population screening of both compositional and mechanical properties. 相似文献
115.
Amir Malaki Nik Marcela Alexander Vaino Poysa Lorna Woodrow Milena Corredig 《Food biophysics》2011,6(1):26-36
The effect of soy protein subunit composition on the acid-induced aggregation of soymilk was investigated by preparing soymilk
from different soybean lines lacking specific glycinin and β-conglycinin subunits. Acid gelation was induced by glucono-δ-lactone
(GDL) and analysis was done using diffusing wave spectroscopy and rheology. Aggregation occurred near pH 5.8 and the increase
in radius corresponded to an increase in the elastic modulus measured by small deformation rheology. Diffusing wave spectroscopy
was also employed to follow acid gelation, and data indicated that particle interactions start to occur at a higher pH than
the pH of onset of gelation (corresponding to the start of the rapid increase in elastic modulus). The protein subunit composition
significantly affected the development of structure during acidification. The onset of aggregation occurred at a higher pH
for soymilk samples containing group IIb (the acidic subunit A3) of glycinin, than for samples prepared from Harovinton (a commercial variety containing all subunits) or from genotypes
null in glycinin. The gels made from lines containing group I (A1, A2) and group IIb (A3) of glycinin resulted in stiffer acid gels compared to the lines containing only β-conglycinin. These results confirmed that
the ratio of glycinin/β-conglycinin has a significant effect on gel structure, with an increase in glycinin causing an increase
in gel stiffness. The type of glycinin subunits also affected the aggregation behavior of soymilk. 相似文献
116.
A canonical correlation analysis of the association between carcass and ham traits in pigs used to produce dry-cured ham 总被引:1,自引:0,他引:1
Ventura HT Lopes PS Peloso JV Guimarães SE Carneiro AP Carneiro PL 《Genetics and molecular biology》2011,34(3):451-455
The association between carcass and ham traits in a pig population used to produce dry-cured ham was studied using canonical correlation analysis. The carcass traits examined were hot carcass weight (HCW), backfat thickness (BT) and loin depth (LD), and the ham traits studied were gross ham weight (GHW), trimmed ham weight (THW), ham inner layer fat thickness (HIFT), ham outer layer fat thickness (HOFT), pH (pH) and the Göfo value. Carcass and ham traits are not independent. The canonical correlations (r) between the carcass and ham traits at 130 kg were 0.77, 0.24 and 0.20 for the first, second and third canonical pair, respectively, and were all significant (p < 0.01) by the Wilks test. The corresponding canonical correlations between the three canonical variate pairs for the carcass and ham traits at 160 kg were 0.88, 0.42 and 0.14, respectively (p < 0.05 for all, except the third). The correlations between the traits and their canonical variate showed an association among HCW, GHW and THW, and between BT and HOFT. These results indicate that carcass traits should be used to cull pigs that are not suitable for dry-cured ham production. 相似文献
117.
Ruiz JC D'Afonseca V Silva A Ali A Pinto AC Santos AR Rocha AA Lopes DO Dorella FA Pacheco LG Costa MP Turk MZ Seyffert N Moraes PM Soares SC Almeida SS Castro TL Abreu VA Trost E Baumbach J Tauch A Schneider MP McCulloch J Cerdeira LT Ramos RT Zerlotini A Dominitini A Resende DM Coser EM Oliveira LM Pedrosa AL Vieira CU Guimarães CT Bartholomeu DC Oliveira DM Santos FR Rabelo ÉM Lobo FP Franco GR Costa AF Castro IM Dias SR Ferro JA Ortega JM Paiva LV Goulart LR Almeida JF Ferro MI Carneiro NP 《PloS one》2011,6(4):e18551
Background
Corynebacterium pseudotuberculosis, a Gram-positive, facultative intracellular pathogen, is the etiologic agent of the disease known as caseous lymphadenitis (CL). CL mainly affects small ruminants, such as goats and sheep; it also causes infections in humans, though rarely. This species is distributed worldwide, but it has the most serious economic impact in Oceania, Africa and South America. Although C. pseudotuberculosis causes major health and productivity problems for livestock, little is known about the molecular basis of its pathogenicity.Methodology and Findings
We characterized two C. pseudotuberculosis genomes (Cp1002, isolated from goats; and CpC231, isolated from sheep). Analysis of the predicted genomes showed high similarity in genomic architecture, gene content and genetic order. When C. pseudotuberculosis was compared with other Corynebacterium species, it became evident that this pathogenic species has lost numerous genes, resulting in one of the smallest genomes in the genus. Other differences that could be part of the adaptation to pathogenicity include a lower GC content, of about 52%, and a reduced gene repertoire. The C. pseudotuberculosis genome also includes seven putative pathogenicity islands, which contain several classical virulence factors, including genes for fimbrial subunits, adhesion factors, iron uptake and secreted toxins. Additionally, all of the virulence factors in the islands have characteristics that indicate horizontal transfer.Conclusions
These particular genome characteristics of C. pseudotuberculosis, as well as its acquired virulence factors in pathogenicity islands, provide evidence of its lifestyle and of the pathogenicity pathways used by this pathogen in the infection process. All genomes cited in this study are available in the NCBI Genbank database (http://www.ncbi.nlm.nih.gov/genbank/) under accession numbers and CP001809. CP001829相似文献118.
Chakravorty A Awad MM Hiscox TJ Cheung JK Carter GP Choo JM Lyras D Rood JI 《PloS one》2011,6(7):e22762
Clostridium perfringens is the causative agent of clostridial myonecrosis or gas gangrene and produces many different extracellular toxins and enzymes, including the cysteine protease α-clostripain. Mutation of the α-clostripain structural gene, ccp, alters the turnover of secreted extracellular proteins in C. perfringens, but the role of α-clostripain in disease pathogenesis is not known. We insertionally inactivated the ccp gene C. perfringens strain 13 using TargeTron technology, constructing a strain that was no longer proteolytic on skim milk agar. Quantitative protease assays confirmed the absence of extracellular protease activity, which was restored by complementation with the wild-type ccp gene. The role of α-clostripain in virulence was assessed by analysing the isogenic wild-type, mutant and complemented strains in a mouse myonecrosis model. The results showed that although α-clostripain was the major extracellular protease, mutation of the ccp gene did not alter either the progression or the development of disease. These results do not rule out the possibility that this extracellular enzyme may still have a role in the early stages of the disease process. 相似文献
119.
Soto-De Leon S Camargo M Sanchez R Munoz M Perez-Prados A Purroy A Patarroyo ME Patarroyo MA 《PloS one》2011,6(2):e14705
Background
Infection with multiple types of human papillomavirus (HPV) is one of the main risk factors associated with the development of cervical lesions. In this study, cervical samples collected from 1,810 women with diverse sociocultural backgrounds, who attended to their cervical screening program in different geographical regions of Colombia, were examined for the presence of cervical lesions and HPV by Papanicolau testing and DNA PCR detection, respectively.Principal Findings
The negative binomial distribution model used in this study showed differences between the observed and expected values within some risk factor categories analyzed. Particularly in the case of single infection and coinfection with more than 4 HPV types, observed frequencies were smaller than expected, while the number of women infected with 2 to 4 viral types were higher than expected. Data analysis according to a negative binomial regression showed an increase in the risk of acquiring more HPV types in women who were of indigenous ethnicity (+37.8%), while this risk decreased in women who had given birth more than 4 times (−31.1%), or were of mestizo (−24.6%) or black (−40.9%) ethnicity.Conclusions
According to a theoretical probability distribution, the observed number of women having either a single infection or more than 4 viral types was smaller than expected, while for those infected with 2–4 HPV types it was larger than expected. Taking into account that this study showed a higher HPV coinfection rate in the indigenous ethnicity, the role of underlying factors should be assessed in detail in future studies. 相似文献120.