全文获取类型
收费全文 | 2675篇 |
免费 | 176篇 |
出版年
2023年 | 13篇 |
2022年 | 36篇 |
2021年 | 80篇 |
2020年 | 37篇 |
2019年 | 53篇 |
2018年 | 69篇 |
2017年 | 48篇 |
2016年 | 81篇 |
2015年 | 126篇 |
2014年 | 139篇 |
2013年 | 192篇 |
2012年 | 229篇 |
2011年 | 248篇 |
2010年 | 138篇 |
2009年 | 121篇 |
2008年 | 159篇 |
2007年 | 126篇 |
2006年 | 116篇 |
2005年 | 108篇 |
2004年 | 118篇 |
2003年 | 89篇 |
2002年 | 85篇 |
2001年 | 34篇 |
2000年 | 33篇 |
1999年 | 28篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 23篇 |
1991年 | 22篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 6篇 |
排序方式: 共有2851条查询结果,搜索用时 78 毫秒
21.
Manju Basu Shu-Ai Weng Hongyu Tang Farhat Khan Federica Rossi Subhash Basu 《Glycoconjugate journal》1996,13(3):423-432
The galactosyltransferase, GalT-4, which catalyses the biosynthesisin vitro of neolactotetraosylceramide, nLcOse4Cer (Gal1-4GleNAc1-3Gal1-4Glc-Cer) from lactotriaosylceramide, LcOse3Cer (GlcNAc1-3Gal1-4Glc-Cer), and UDP-galactose has been purified 107 500-fold from a mineral oil induced mouse T-lyphoma P-1798, using affinity columns. The purified enzyme is partially stabilized in the presence of phospholipid liposomes. Two closely migrating protein bands of apparent molecular weights 56 kDa and 63 kDa were observed after sodium dodecyl sulfate polyacrylamide gel electrophoresis of highly purified mouse GalT-4. These two protein bands, when subjected to limited proteolysis, resulted in three peptides with identical mobilities indicating amino acid sequence identity between the proteins. Both protein bands from P-1798 gave a positive immunostain when tested with polyclonal antibody against bovine lactose synthetase (UDP-Gal:Glc 4-galactosyltransferase) following Western blot analysis on nitrocellulose paper. The enzyme has a pH optimum between 6.5 and 7.0 and like all other galactosyltransferases, GalT-4 has absolute requirements for divalent cation (Mn2+). TheK
m values for the substrate LcOse3Cer and donor UDP-galactose are 110 and 250 µm, respectively. Substrate competition studies with LcOse3Cer and either asialo-agalacto-1-acid glycoprotein orN-acetylglucosamine revealed that these reactions might be catalysed by the same protein. The only other glycolipid which showed acceptor activity toward the purified GalT-4 was iLcOse5Cer (GlcNAc1-1-3Gal1-4Lc3), the precursor for polylactosamine antigens. However, competition studies with these two active substrates using the most purified enzyme fraction, revealed that these two reactions might be catalysed by two different proteins since the experimental values were closer to the theoretical values calculated for two enzymes. Interestingly however, it seems that the GalT-4 from P-1798 has an absolute requirement for anN-acetylglucosamine residue in the substrate since the lyso-derivative (GlcNH21-3Gal1-4Glc-sphingosine) of the acceptor glycolipid LcOse3Cer is completely inactive as substrate while theK
m andV
max of the reacetylated substrate (GlcNac1-3Gal1-4Glc-acetylsphingosine) was comparable with LcOse3Cer. Autoradiography of the radioactive product formed by purified P-1798 GalT-4 confirmed the presence of nLcOse4Cer, as the product cochromatographed with authentic glycolipid. The monoclonal antibody IB-2, specific for nLcOse4Cer, also produced a positive immunostained band on TLC as well as giving a positive ELISA when tested with radioactive product obtained using a highly purified enzyme from mouse P-1798 T-lymphoma.Abbreviations EDTA
ethylenediamine tetraacetate
- ME
-mercaptoethanol
- PEG
polyethylene glycol
- PBS
phosphate buffered saline
- Suc
sucrose
- Mn2+
manganese
- Gal
galactose
- GlcNAc
N-acetylglucosamine
- UDP-Gal
Uridine diphosphate galactose
- Ab
antibody
- SDS
sodium dodecyl sulphate
- PAGE
polyacrylamide gel electrophoresis
- ECB
embryonic chicken brain
- Cer
ceramide
- nLc4 or NlcOse4Cer
Gal1-4GleNac1-3Gal1-4Glc-Cer, neoLactotetraosylceramide
- Lc3 or LcOse3Cer
GlcNac1-3Gal1-4Glc-Cer, lactotriaosylceramide
- iLc5
iLcOse5Cer, GlcNAc1-3nLcOse4Cer
- nLc6
nLcOse6Cer, Gal1-4iLcOse5Cer
- SA–Gal–1AGP
asialo-agalacto1-acid glycoprotein
- TLC
thin layer chromatography 相似文献
22.
X-linked Alport syndrome: an SSCP-based mutation survey over all 51 exons of the COL4A5 gene. 总被引:13,自引:1,他引:12
下载免费PDF全文
![点击此处可从《American journal of human genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A. Renieri M. Bruttini L. Galli P. Zanelli T. Neri S. Rossetti A. Turco N. Heiskari J. Zhou R. Gusmano L. Massella G. Banfi F. Scolari A. Sessa G. Rizzoni K. Tryggvason P. F. Pignatti M. Savi A. Ballabio M. De Marchi 《American journal of human genetics》1996,58(6):1192-1204
The COL4A5 gene encodes the alpha5 (type IV) collagen chain and is defective in X-linked Alport syndrome (AS). Here, we report the first systematic analysis of all 51 exons of COL4A5 gene in a series of 201 Italian AS patients. We have previously reported nine major rearrangements, as well as 18 small mutations identified in the same patient series by SSCP analysis of several exons. After systematic analysis of all 51 exons of COL4A5, we have now identified 30 different mutations: 10 glycine substitutions in the triple helical domain of the protein, 9 frameshift mutations, 4 in-frame deletions, 1 start codon, 1 nonsense, and 5 splice-site mutations. These mutations were either unique or found in two unrelated families, thus excluding the presence of a common mutation in the coding part of the gene. Overall, mutations were detected in only 45% of individuals with a certain or likely diagnosis of X-linked AS. This finding suggests that mutations in noncoding segments of COL4A5 account for a high number of X-linked AS cases. An alternative hypothesis is the presence of locus heterogeneity, even within the X-linked form of the disease. A genotype/phenotype comparison enabled us to better substantiate a significant correlation between the degree of predicted disruption of the alpha5 chain and the severity of phenotype in affected male individuals. Our study has significant implications in the diagnosis and follow-up of AS patients. 相似文献
23.
Characterization of two virulent Lactobacillus fermentum bacteriophages isolated from sour dough 总被引:2,自引:2,他引:0
Two different bacteriophages, FE5-B1 and Z63-B1, active against strains of Lactobacillus fermentum were isolated from a sample of sour dough of a regional wheat bread. They showed different host specificities when tested against 58 strains of obligately heterofermentative lactic acid bacteria, as well as differences in adsorption and one-step growth kinetics. The burst size of FE5-B1 was about 100 pfu cell−1 . This phage belonged to the A1 morphotype of Myoviridae family, having an icosahedral head (83 nm diam.) and a sheathed contractile tail (170 nm in length). The phage consisted of five major structural proteins and had a genome of 86 kbp. Z63-B1 showed a burst size of 10 pfu cell−1 and belonged to the B1 morphotype or Siphoviridae family. Z63-B1 had an isometric head (60 nm diam.) and a non-contractile tail (160 nm in length), with eight major different structural proteins and a genome of 32 kbp. 相似文献
24.
A genetic system selecting for deletion events (DEL recombination) due to intrachromosomal recombination has previously been constructed in the yeastSaccharomyces cerevisiae. Intrachromosomal recombination is inducible by chemical and physical carcinogens. We wanted to understand better the mechanism of induced DEL recombination and to attempt to determine in which phase of the cell cycle DEL recombination is inducible. Yeast cells were arrested at specific phases of the cell cycle, irradiated with UV or γ-rays, and assayed for DEL recombination and interchromosomal recombination. In addition, the contribution of intrachromatid crossing-over to the number of radiation induced DEL recombination events was directly investigated at different phases of the cell cycle. UV irradiation induced DEL recombination preferentially in S phase, while γ-rays induced DEL recombination in every phase of the cell cycle including G1. UV and γ-radiation induced intrachromatid crossing over preferentially in G1, but it accounted at the most for only 14% of the induced DEL recombination events. The possibility is discussed that single-strand annealing or one-sided invasion events, which can occur in G1 and may be induced by a double-strand break intermediate, may be responsible for a large proportion of the induced DEL recombination events. 相似文献
25.
G. Bestetti P. Di Gennaro E. Galli B. Leoni F. Pelizzoni G. Sello D. Bianchi 《Applied microbiology and biotechnology》1994,40(6):791-793
The Pseudomonas fluorescens N3 was isolated from soil for its ability to utilize naphthalene as a carbon source. The strain transforms 2,3-dimethyl-, 2-methoxy-, 1- and 2-ethylnaphthalenes to the corresponding salicylic acids competitively with chemical synthesis. The identification of 2-hydroxy-2-carboxy-7-ethylchromane by biotransformation of 2-ethylnaphthalene, contributes to elucidating the steps involved in the catabolic pathways of naphthalenes to salicylaldehydes.
Correspondence to: F. Pelizzoni 相似文献
26.
We used a computer-assisted morphometry approach to analyze quantitatively the process of cytoplasmic granule formation in mouse pancreatic acinar cells stimulated with pilocarpine to induce secretion. Our findings suggest that each condensing vacuole/immature granule of pancreatic acinar cells is formed by the progressive aggregation of 106 to 128 unit progranules of narrowly fixed volume, define a range of 7.7 to 9.2 for the factor of volume condensation between the largest immature granules and the mature unit granule, and predict that the formation of a single mature unit granule by the aggregation and fusion of unit progranules involves a net reduction of at least 95% in the amount of membrane surface area associated with these structures. 相似文献
27.
The salivary gland secretion in the dipteran Chironomus tentans is composed of approximately 15 different secretory proteins. The most well known of the corresponding genes are the four
closely related Balbiani ring (BR) genes, in which the main part of each approximately 40-kb gene is composed of tandemly
arranged repetitive units. Six of the seven additional secretory protein genes described share structural similarities with
the BR genes and are members of the same BR multigene family. Here we report the identification of a new secretory protein
gene, the spl2 gene, encoding the smallest component of the C. tentans salivary gland secretion. The gene has a corresponding mRNA length of approximately 0.7 kb and codes for a protein with a
calculated molecular weight of 7,619 Da. The sp12 gene was characterized in seven Chironomus species. Based on a comparison of the orthologous gene sequences, we conclude that the sp12 gene has a repetitive structure
consisting of diverged 21-by-long repeats. The repeat structure and the codon composition are similar to the so-called SR
regions of the BR genes and the sp 12 gene may represent a diverged member of the BR multigene family.
Correspondence to: L. Wieslander 相似文献
28.
Federica Rossi Rita Baraldi Osvaldo Facini Bartolomeo Lereari 《Plant Cell, Tissue and Organ Culture》1993,32(2):145-151
The morphogenic effect of different light wavelengths on in vitro rooting of Prunus insititia GF655-2 in relation to the presence of napthaleneacetic acid (NAA) in the culture medium was investigated. Results of experiments in which plantlets were rooted in NAA enriched medium showed that the presence of auxin induced rooting even in the dark after an initial lag period. Illumination of the cultures with Red light was as effective in promoting rooting as treatment with 0.5 M NAA; Red was more active in stimulating rooting in the short term than was NAA. The pattern of root formation resulting from the addition of NAA appeared to dominate development under White, Blue and Far Red treatments. Although it was possible to correlate the rooting response to the phytochrome photoequilibrium induced by the light treatments used, there arises a possible interference of specific Blue absorbing photoreceptors.Abbreviations B
Blue
- FR
Far Red
- HIR
High Irradiance Response
- Pfr
active (far-red absorbing) form of phytochrome
- Ptot
total phytochrome
- R
Red
- W
White
- NAA
-naphtaleneacetic acid
- BA
benzyladenine
- IAA
indole 3-acetic acid 相似文献
29.
Diana Fiorentini Marta Cipollone Maria Cristina Galli Armanda Pugnaloni Graziella Biagini Laura Landi 《Free radical research》1994,21(5):329-339
The aim of this work was to characterize large unilamellar vesicles (LUVETs) prepared by a hand-driven extrusion device in order to use them for studies of lipid peroxidation and antioxidant activity. Vesicle structure and size were examined by electron microscopy. Lipid and antioxidant content was determined before and after the extrusion procedure. Then LUVETs were subjected to autoxidation initiated by both the lipid-soluble 2,2'-azobis(2,4-dimethylvaleronitrile) and the water-soluble 2,2'-azobis(2-amidinopropane hydrochloride) azocompounds. The results demonstrated that: i) LUVETs prepared with lipid concentrations ranging between 25 and 150 mM were essentially unilamellar and reasonably homogeneous, with an average diameter of 90 nm; ii) the phospholipid, cholesterol and antioxidant amounts retained by filters were about 10-15%; iii) LUVETs were suitable for autoxidation studies initiated by the water-soluble azocompound both in the absence and presence of antioxidants. The lipid-soluble azocompound could be used only at low concentrations and its vesicle content had to be determined since part of the initiator was not incorporated into the lipid bilayer. These data suggest that LUVETs seem to be recommended for studies of lipid peroxidation and antioxidant activity. 相似文献
30.
Ilan Hammel Joseph Alroy Vibha Goyal Stephen J. Galli 《Virchows Archiv. B, Cell pathology including molecular pathology》1993,64(1):83-89
The effect of lysosomal storage diseases on the ultrastructure of human mast cells has not previously been reported. Indeed,
there has been little published evidence indicating that mast cells contain typical lysosomes. However, mast cell cytoplasmic
granules contain hydrolases similar to those found in lysosomes, but which differ from lysosomal hydrolases in exhibiting
optimal activity at higher pH. We therefore examined by transmission electron microscopy the dermal mast cells in 58 biopsies
of patients exhibiting 1 of 29 different lysosomal storage diseases. We found mast cells containing abnormal lysosomes in
16 of these disorders. In 6 of these 16 diseases, the mast cells' cytoplasmic granules appeared normal. These observations
indicate that human mast cells can contain lysosomes, and provide evidence that the enzymes affected by lysosomal storage
diseases are active in mast cells. 相似文献