全文获取类型
收费全文 | 965篇 |
免费 | 22篇 |
国内免费 | 8篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 30篇 |
2013年 | 33篇 |
2012年 | 25篇 |
2011年 | 17篇 |
2010年 | 13篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 35篇 |
2004年 | 64篇 |
2003年 | 36篇 |
2002年 | 19篇 |
2001年 | 40篇 |
2000年 | 26篇 |
1999年 | 31篇 |
1998年 | 30篇 |
1997年 | 25篇 |
1996年 | 48篇 |
1995年 | 41篇 |
1994年 | 36篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 20篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 15篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有995条查询结果,搜索用时 31 毫秒
1.
Sandhya Ravishankar Meera Pandey R. P. Tewari V. Krishna 《World journal of microbiology & biotechnology》2006,22(10):1021-1025
Summary The sporophores of Pleurotus are gymnocarpous and continuously release spores in the atmosphere causing respiratory allergies like hay fever and farmer’s lung disease among workers. The allergy is caused by the antigens present on the walls of the spores. Apart from this, during commercial production, these spores settle on the fruit bodies, germinate and form a velvety film which gives an unpleasant appearance to the mushrooms. The spores emitted may include new genotypes likely to attack wood or trees. Spore allergy is one of the most important limiting factors for the large scale cultivation of this species. Different approaches are being adopted at IIHR for the production of commercial sporeless/low-sporing strains of Pleurotus to alleviate the spore allergy problem. Attempts were made during the present investigation to produce sporeless or low-sporing mutants through u.v. mutation. Mutation of the mycelium did not yield the desired results. Mutation of the spores of Pleurotus sajor-caju yielded an extremely low-sporing mutant after 75 min exposure. The character has been found to be stable for more than 10 generations of subculturing. 相似文献
2.
Yongru Sun Berthold M. Heil Günter Kahl Hans Willy Kohlenbach 《Plant Cell, Tissue and Organ Culture》1987,8(1):91-100
Calli were initiated from flower buds, gynoecia and inflorescence segments of Haworthia magnifica v. Poelln. and subcultured on solid medium. Two liquid culture steps were necessary to prepare the calli for the isolation of protoplasts capable of sustained cell divisions. Plants were regenerated from protoplast-derived calli. The influence of both the osmolality of the culture media and exudates on the viability of protoplasts and protoplast-derived cell colonies is briefly discussed. 相似文献
3.
4.
Lars-G. Lundin 《Biochemical genetics》1987,25(7-8):603-610
A gene (Bmn) with a major effect on -mannosidase activity in kidney and liver of the house mouse was revealed by assay with the synthetic substratep-nitrophenyl--d-mannoside. Activity is low in DBA/2J and CSB mice and high in C57BL/6J mice. By the use of the BXD series of recombinant inbred strains and by crosses between C57BL and CSB, it was possible to map the gene to the distal part of chromosome 3 by demonstration of linkage to a gene for cadmium resistance,cdm, as well as to theAdh-3 locus.This work was supported by Swedish Natural Science Research Council Project B-BU 2992-108. 相似文献
5.
Summary Dissociated single cells from chicken retina or tectum kept in rotation-mediated cell culture aggregate, proliferate and establish a certain degree of histotypical cellto-cell relationships (sorting out), but these systems never form highly laminated aggregates (nonstratified R- and T-aggregates). In contrast, a mixture of retinal plus pigment epithelial cells forms highly stratified aggregates (RPE-aggregates, see Vollmer et al. 1984). The present comparative study of stratified and nonstratified aggregates enables us to investigate the process of cell proliferation uncoupled from that of tissue stratification. Here we try to relate these two basic neurogenetic processes with patterns of expression of cholinesterases (AChE, BChE) during formation of both types of aggregates.During early aggregate formation, in both stratified and nonstratified aggregates an increased butyrylcholinesterase activity is observed close to mitotically active cells. Quantitatively both phenomena show their maxima after 2–3 days in culture. In contrast, AChE-expression in all systems increases with incubation time. In nonproliferative areas, in the center of RPE-aggregates, the formation of plexiform layers is characterized initially by weak BChE and then strong AChE-activity. These areas correspond with the inner (IPL) and outer (OPL) plexiform layers of the retina in vivo. Although by sucrose gradient centrifugation we find that the 6S- and the fiber-associated 11S-molecules of AChE are present in all types of aggregates, during the culture period the ratio of 11S/6S-forms increases only in RPE-aggregates, which again indicates the advanced degree of differentiation within these aggregates.It is thus demonstrated that cholinesterases first correlate with neuronal cell proliferation and later with stratification, which indicates functions of both enzymes during both developmental periods.Abbreviations
AChE
acetylcholinesterase
-
BChE
butyrylcholinesterase
-
iso-OMPA
specific inhibitor of BChE
-
BW 284C51
specific inhibitor of AChE
-
IPL
inner plexiform layer
-
OPL
outer plexiform layer 相似文献
6.
T. de la Rubia J. Gonzalez-Lopez J. Moreno M. V. Martinez-Toledo A. Ramos-Cormenzana 《Archives of microbiology》1987,147(4):354-357
The effect of a low phosphate concentration on intracellular adenine nucleotide content, oxygen consumption and poly--hydroxybutyrate deposition was investigated with N-free and NH
4
+
batch cultures of Azotobacter vinelandii. When the microorganisms were cultured under low-phosphate concentrations the cells contained much larger amounts of poly--hydroxybutyrate, but displayed lower oxygen consumption activities and energy charge values than did control cells. Also, the ratio ATP to ADP was much higher in control cells and the intracellular levels of ATP were lower in low-phosphate cells. 相似文献
7.
Matilde Jose Isabelle Tratner Maryse Poiret Jean-Louis Nahon Jean-Louis Danan Jose Maria Sala-Trepat 《Molecular & general genetics : MGG》1989,215(2):225-230
Summary The distribution of middle repetitive sequences in the genic and extragenic regions of the rat albumin and -fetoprotein genes was analyzed. Their presence was determined by probing Southern blots of restriction fragments of albumin and -fetoprotein genomic subclones with 32P-labeled total rat DNA. Repetitive sequences were detected in both genes. They were classified as weak, moderate and intense hybridizing elements according to the intensity of hybridization. Weak repetitive sequences were characterized as dG·dT repeats by using 32P-labeled poly-(dG·dT)(dC·dA) oligomer probe. They occurred in 5 and 3 extragenic regions of the two genes and in introns 4 and 5 of the albumin gene. The moderate repetitive sequence present in intron 6 of the albumin gene was identified as the rat SINES element, 4D12. The intense repetitive sequence, localized in the 3 non-coding region of the albumin gene, corresponded to the terminal segment of a rat high repeat long interspersed DNA family, L1Rn. 4D12 and L1Rn sequences were also scattered throughout the -fetoprotein locus as moderate and intense repetitive elements, respectively, but their distribution was different from that of the albumin genomic region. These results indicate that repetitive sequences invaded the two loci in a non-conservative manner. 相似文献
8.
Cecilia PC Soh Alastair SR Donald James Feeney Walter TJ Morgan Winifred M Watkins 《Glycoconjugate journal》1989,6(3):319-332
The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and1H-500 MHz NMR spectroscopy. In Sda serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity. 相似文献
9.
Cellular origin and distribution of transforming growth factor-β1 in the normal rat myocardium 总被引:6,自引:0,他引:6
Dr. M. Eghbali 《Cell and tissue research》1989,256(3):553-558
Summary Transforming growth factor- (TGF-) is a biologically active polypeptide present in normal tissues as well as transformed cells. Two structurally related forms of this peptide are TGF-
1 and TGF-
2. Using freshly isolated cardiomyocytes and non-myocyte heart cells, and a [32P]-labelled cDNA probe to human TGF-
1, we demonstrated that mRNA for TGF-
1 could be detected only in the nonmyocyte fraction of heart cells. In the present study, the distribution of TGF-
1 in the heart was determined by immunofluorescence staining by use of a polyclonal antibody to porcine TGF-
1 in cryostat sections of rat heart. Immunofluorescence staining was intense around the blood vessels and radially diffuse in the surrounding myocardium. 相似文献
10.
E. Ann MacGregor 《Journal of Protein Chemistry》1988,7(4):399-415
Two computerized methods of predicting protein secondary structure from amino acid sequences are evaluated by using them on the -amylase ofAspergillus oryzae, for which the three-dimensional structure has been determined. The methods are then used, with amino acid alignments, to predict the structures of other -amylases. It is found that all -amylases of known amino acid sequence have the same basic structure, a barrel of eight parallel stretches of extended chain surrounded by eight helices. Strong similarities are found in those areas of the proteins believed to bind an essential calcium ion and at that part of the active site that catalyzes bond hydrolysis in the substrates. The active site, as a whole, is formed mainly of amino acids situated on loops joining extended chain to the adjacent helix. Variations in the length and amino acid sequence of these loops, from one -amylase to another, provide the differences in binding the substrates believed to account for the known variations in action pattern of -amylases of different biological origins. 相似文献