全文获取类型
收费全文 | 301篇 |
免费 | 27篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 23篇 |
2012年 | 31篇 |
2011年 | 27篇 |
2010年 | 19篇 |
2009年 | 18篇 |
2008年 | 19篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有328条查询结果,搜索用时 31 毫秒
81.
Lagaert S Pollet A Delcour JA Lavigne R Courtin CM Volckaert G 《Biochemical and biophysical research communications》2010,402(4):644-650
Bifidobacterium adolescentis possesses several arabinofuranosidases able to hydrolyze arabinoxylans (AX) and AX oligosaccharides (AXOS), the latter being bifidogenic carbohydrates with potential prebiotic properties. We characterized two new recombinant arabinofuranosidases, AbfA and AbfB, and AXH-d3, a previously studied arabinofuranosidase from B. adolescentis. AbfA belongs to glycoside hydrolase family (GH) 43 and removed arabinose from the C(O)2 and C(O)3 position of monosubstituted xylose residues. Furthermore, hydrolytic activity of AbfA was much larger towards substrates with a low amount of arabinose substitutions. AbfB from GH 51 only cleaved arabinoses on position C(O)3 of disubstituted xyloses, similar to GH 43 AXH-d3, making it to our knowledge, the first reported enzyme with this specificity in GH 51. AbfA acted synergistically with AbfB and AXH-d3. In combination with AXH-d3, it released 60% of arabinose from wheat AX. Together with recent studies on other AXOS degrading enzymes from B. adolescentis, these findings allowed us to postulate a mechanism for the uptake and hydrolysis of bifidogenic AXOS by this organism. 相似文献
82.
83.
Stijn van Eesbeek Jurriaan H. de Groot Frans C.T. van der Helm Erwin de Vlugt 《Journal of biomechanics》2010,43(13):2539-2547
Short-range stiffness (SRS) is a mechanical property of muscles that is characterized by a disproportionally high stiffness within a short length range during both lengthening and shortening movements. SRS is attributed to the cross-bridges and is beneficial for stabilizing a joint during, e.g., postural conditions. Thus far, SRS has been estimated mainly on isolated mammalian muscles. In this study we presented a method to estimate SRS in vivo in the human wrist joint.SRS was estimated at joint level in the angular domain (N m/rad) for both flexion and extension rotations of the human wrist in nine healthy subjects. Wrist rotations of 0.15 rad at 3 rad/s were imposed at eight levels of voluntary contraction ranging from 0 to 2.1 N m by means of a single axis manipulator.Flexion and extension SRS of the wrist joint was estimated consistently and accurately using a dynamic nonlinear model that was fitted onto the recorded wrist torque. SRS increased monotonically with torque in a way consistent with previous studies on isolated muscles.It is concluded that in vivo measurement of joint SRS represents the population of coupled cross-bridges in wrist flexor and extensor muscles. In its current form, the presented technique can be used for clinical applications in many neurological and muscular diseases where altered joint torque and (dissociated) joint stiffness are important clinical parameters. 相似文献
84.
Despite the presence of high nutrient concentrations, most ponds located around Brussels (Belgium) show a considerable variation
in turbidity. The importance of submerged macrophytes in maintaining the clear-water state requires identification of the
main factors determining macrophyte abundance and diversity in ponds and small lakes. In this study, the inter-relationships
between submerged macrophyte cover, fish abundance and turbidity were investigated in 13 eutrophic peri-urban ponds. Along
a turbidity gradient, vegetation switched from dominance by Stoneworts (Chara and Nitella spp.) in the clearest ponds, to dominance by Potamogeton pectinatus in ponds with a slightly lower water transparency. Despite the presence of both P. pectinatus and Stoneworts in each of the vegetated ponds, only one became dominant. Only a very low abundance (around 20%) of submerged
vegetation was found in ponds of intermediate turbidity, while macrophytes were absent in turbid ponds. Multi- and univariate
analysis showed a marked difference in chemical, physical and biological properties between ponds deliberately used for fish
stocking and ponds that were not. Macrophyte cover was significantly negatively correlated with turbidity and plankti-benthivorous
fish abundance. No such correlation was observed with piscivorous fish abundance, except for pike that were associated with
a charophyte vegetation in the study ponds. The strong relationship found between fish abundance and turbidity, its negative
effect on submerged vegetation cover, and the importance of submerged vegetation in controlling phytoplankton abundance, should
be taken into account when selecting ponds for fish stocking. It also suggests that the study ponds have a good potential
for ecological quality restoration by biomanipulation. 相似文献
85.
Caroline M.W. van Stijn Lonneke Vervelde Richard D. Cummings Boris Tefsen 《International journal for parasitology》2010,40(2):215-222
Lambs vaccinated with Haemonchus contortus excretory/secretory (ES) glycoproteins in combination with the adjuvant Alhydrogel are protected against H. contortus challenge infection. Using glycan micro-array analysis we showed that serum from such vaccinated lambs contains IgG antibodies that recognise the glycan antigen Galα1-3GalNAc-R and GalNAcβ1-4(Fucα1-3)GlcNAc-R. Our studies revealed that H. contortus glycoproteins contain Galα1-3Gal-R as well as significant levels of Galα1-3GalNAc-R, which has not been previously reported. Extracts from H. contortus adult worms contain a galactosyltransferase acting on glycan substrates with a terminal GalNAc, indicating that the worms possess the enzymatic potential to synthesise terminal Gal-GalNAc moieties. These data illustrate that glycan micro-arrays constitute a promising technology for fast and specific analysis of serum anti-glycan antibodies in vaccination studies. In addition, this approach facilitates the discovery of novel, antigenic parasite glycan antigens that may have potential for developing glycoconjugate vaccines or utilization in diagnostics. 相似文献
86.
Spinelli S Desmyter A Verrips CT de Haard HJ Moineau S Cambillau C 《Nature structural & molecular biology》2006,13(1):85-89
Lactococcus lactis is a Gram-positive bacterium used extensively by the dairy industry for the manufacture of fermented milk products. The double-stranded DNA bacteriophage p2 infects specific L. lactis strains using a receptor-binding protein (RBP) located at the tip of its noncontractile tail. We have solved the crystal structure of phage p2 RBP, a homotrimeric protein composed of three domains: the shoulders, a beta-sandwich attached to the phage; the neck, an interlaced beta-prism; and the receptor-recognition head, a seven-stranded beta-barrel. We used the complex of RBP with a neutralizing llama VHH domain to identify the receptor-binding site. Structural similarity between the recognition-head domain of phage p2 and those of adenoviruses and reoviruses, which invade mammalian cells, suggests that these viruses, despite evolutionary distant targets, lack of sequence similarity and the different chemical nature of their genomes (DNA versus RNA), might have a common ancestral gene. 相似文献
87.
Lundstrom K Wagner R Reinhart C Desmyter A Cherouati N Magnin T Zeder-Lutz G Courtot M Prual C André N Hassaine G Michel H Cambillau C Pattus F 《Journal of structural and functional genomics》2006,7(2):77-91
Production of recombinant receptors has been one of the major bottlenecks in structural biology on G protein-coupled receptors
(GPCRs). The MePNet (Membrane Protein Network) was established to overexpress a large number of GPCRs in three major expression
systems, based on Escherichia coli, Pichia pastoris and Semliki Forest virus (SFV) vectors. Evaluation by immunodetection demonstrated that 50% of a total of 103 GPCRs were
expressed in bacterial inclusion bodies, 94% in yeast cell membranes and 95% in SFV-infected mammalian cells. The expression
levels varied from low to high and the various GPCR families and subtypes were analyzed for their expressability in each expression
system. More than 60% of the GPCRs were expressed at milligram levels or higher in one or several systems, compatible to structural
biology applications. Functional activity was determined by binding assays in yeast and mammalian cells and the correlation
between immunodetection and binding activity was analyzed. 相似文献
88.
89.
90.