全文获取类型
收费全文 | 563篇 |
免费 | 26篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 14篇 |
2014年 | 24篇 |
2013年 | 27篇 |
2012年 | 44篇 |
2011年 | 31篇 |
2010年 | 29篇 |
2009年 | 33篇 |
2008年 | 35篇 |
2007年 | 38篇 |
2006年 | 30篇 |
2005年 | 34篇 |
2004年 | 36篇 |
2003年 | 30篇 |
2002年 | 33篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有589条查询结果,搜索用时 109 毫秒
1.
Koji Yamada Masumi Ohtsu Genki Kimura 《In vitro cellular & developmental biology. Plant》1985,21(8):428-432
Summary Sodium butyrate causes proliferation arrest with a G2 (4C) DNA content and induces formation of tetraploid cells upon removal
of the inhibitor, in rat 3Y1 diploid fibroblasts. We isolated tetraploid clones from the butyrate-treated 3Y1 cells with high
efficiency; among 21 clones randomly isolated, 5 were pure diploid, 7 were mainly tetraploid with a small contaminating diploid
population, and 7 were pure tetraploid. Among the pure tetraploid clones, two showed doubled chromosome numbers with slightly
broader distributions than that seen in parental 3Y1 cells. Butyrate further induced polyploid formation in the tetraploid
cells thus produced, but octaploid cells that resulted could not be maintained for prolongeed, cultivation. We found no difference
between the tetraploid and the (parental and parallel isolated) diploid clones in terms of colony-forming ability, proliferation
rate, and sensitivity to density-dependent inhibition of proliferation. These results suggest that doubling of chromosome
number by itself does not cause a change in proliferation property. The tetraploid clones had lower average saturation densities
possibly due to enlargement of cell size represented by higher cellular protein content. 相似文献
2.
3.
12-O-Tetradecanoylphorbol-13-acetate (TPA) is a well-known tumor promoter in mouse-skin carcinogenesis. Its effects on mutagenesis in a soybean test system were examined, and the effects were judged from the appearance of spots of various colors on the leaves. When soybean seeds were treated with TPA plus 0.03% caffeine, the frequency of spots per leaf decreased significantly and in proportion to the concentration of TPA. TPA alone at concentrations of 1–20 μg/ml did not induce any mutations. Mutations induced by γ-rays were not affected by administration of TPA either before or after exposure to γ-rays. The mechanism of suppression by TPA of mutations induced by caffeine is discussed. 相似文献
4.
During photoreactivation of the O2-evolving center in Tris-inactivated/Mn-depletedthylakoids, a slow O2-consumption occurred. This O2-consumptionbecame detectable when the O2-evolving activity of thylakoidswas inactivated by Tris-treatment and decreased as photoreactivationproceeded. The O2-consumption and photoreactivation similarlyrequired Mn2+ at µM levels in addition to PSII electrondonors and shared severa common characteristics. Stimulationof O2-consumption and photoreactivation by these cofactors werealways accompanied by enhancement in chlorophyll fluorescenceinduction, suggesting the involvement of a Mehler-type reactionin photoreactivation. Although the electron transport due tothis O2-consumption was rapid enough to oxidize 4 Mn2+ ionsto reconstitute the tetranuclear Mn-cluster in each O2-evolvingcenter in a few seconds, actual recovery of O2-evolving activityoccurred more slowly in a few minutes. It was inferred thatphotoreactivation in Tris-inactivated thylakoids is not a simplephotooxidation of Mn22+ but involves more complicated processeswhich are coupled to the Mehlertype electron transport fromPSII to oxygen via PSI. (Received July 11, 1994; Accepted August 23, 1996) 相似文献
5.
Takashi Ninomiya Masumi Hirabayashi Junko Sagara Atsushi Yuki 《Molecular reproduction and development》1994,37(3):276-283
Fragments containing 5′ flanking regions of four bovine milk protein genes—alpha lactalbumin (bαLA), alpha S1 casein (bαS1CN), beta casein (bβCN), kappa casein (bkCN)—and mouse whey acidic protein (mWAP) gene were prepared by PCR and ligated to human growth hormone (hGH) gene. These recombinant DNAs were microinjected into rat embryos to produce transgenic rats, and the functions of the 5′ regions to direct secretion of hGH in the milk were tested. Although milk was obtained only in 5 of 19 mWAP/hGH rat lines, more than two-thirds of the rats carrying the other four DNAs produced milk. More than 80% of the lactated rats carrying bαLA/, bβCN/, and mWAP/hGH, and 33% of the laclated bαS1CN/hGH rats secreted detectable amounts of hGH (> 0.05 μg/ml) in the milk. In some rats, the hGH concentrations in the milk were comparable to or more than that of the corresponding milk protein in bovine milk. The ranges of hGH concentrations in the milk of bαLA/, bβCN/, bαS1CN/, and mWAP/hGH rats were 1.13–4,360 μg/ml, 0.11–10,900 μg/ml, 86.8–6,480 μg/ml, and 6.87–151 μg/ml, respectively. HGH was also detected in the sera of these rats, and some abnormalities of growth and reproduction were observed. All but one virgin mWAP/hGH rat secreted up to 0.0722 μg/ml of hGH in the serum, and more than half of them showed abnormal fat accumulations at their abdomen. None of the bαCN/hGH rats secreted detectable amount of hGH into their milk, whereas 8 of the 11 lines secreted hGH into their sera. For the production of hGH in transgenic rat milk, the 5′ region of bαS1CN was shown most suitable, because the bαS1CN/hGH rat secreted > 6,000 μg/ml of hGH into the milk and could be reproduced. © 1994 Wiley-Liss, Inc. 相似文献
6.
Hideo Nishitani Masumi Hidaka Takashi Horiuchi 《Molecular genetics and genomics : MGG》1993,240(3):307-314
To clone new replication origin(s) activated under RNase H-defective (rnh ?) conditions in Escherichia coli cells, whole chromosomal DNA digested with EcoRI was to with a Kmr DNA fragment and transformed into an rnh? derivative host. From the Kmr transformants, we obtained eight kinds of plasmid-like DNA, each of which contained a specific DNA fragment, termed “Hot”, derived from the E. coli genome. Seven of the Hot DNAs (HotA-G) mapped to various sites within a narrow DNA replication termination region (about 280 kb), without any particular selection. Because Hot DNA could not be transformed into a mutant strain in which the corresponding Hot region had been deleted from the chromosome, the Hot DNA, though obtained as covalently closed circular (ccc) DNA, must have arisen by excision from the host chromosome into which it had initially integrated, rather than by autonomous replication of the transformed species. While Hot DNA does not have a weak replication origin it does have a strong recombinational hotspot active in the absence of RNase H. This notion is supported by the finding that Chi activity was present on all Hot DNAs tested and no Hot-positive clone without Chi activity was obtained, with the exception of a DNA clone carrying the dif site. 相似文献
7.
Hirohiko Iwatsuki Kazunobu Sasaki Masumi Suda Chikako Itano 《Histochemistry and cell biology》1995,104(4):277-286
Using lectin and colloidal iron (CI) stainings in combination with neuraminidase digestion, glycoconjugates on the surface of erythropoietic cells of the yolk sac and liver in fetal mice were examined. Fetal hepatic macrophages were capable of distinguishing between phagocytozed and non-phagocytozed erythroid elements as described in our previous study. Marked differences between these two elements could be ultrahistochemically detected on their cell surface. The phagocytozed elements, such as nuclei expelled from erythroblasts and degenerating primitive erythroblasts, faintly bound neuraminidase-sensitive CI, and neuraminidase digestion imparted a weak peanut agglutinin (PNA) binding. In contrast, erythroblasts at various maturation stages, erythrocytes and normal primitive erythroblasts heavily bound neuraminidase-sensitive CI, and neuraminidase digestion imparted a moderate PNA binding. No differences in binding of either concanavalin agglutinin,Ricinus communis agglutinin-I or PNA were noted between phagocytozed and non-phagocytozed erythroid elements. Desialylation appears to be one of the most important signs for the recognition mechanism of fetal macrophage phagocytosis. During maturation of hepatic erythroblasts, sialic acid changes its affinity forLimax flavus agglutinin from strong to weak, and soybean agglutinin binding sites disappear at the basophilic erythroblast stage. Glycoconjugates on polychromatophilic erythroblasts acquire similar compositions to those of erythrocytes. 相似文献
8.
9.
Kei Sasaoka Tadashi Ogawa Masumi Kimoto 《Archives of biochemistry and biophysics》1982,219(2):454-458
Ninhydrin-negative conjugates of basic amino acids were isolated from rat urine and were characterized. The following conjugates of basic amino acids are the compounds newly identified in animal urine specimens, Nα-acetyl-Nπ-methylhistidine, Nα-(N-acetyl-β-alanyl)histidine (N-acetylcarnosine), Nα-acetyl-NG,N′G-dimethylarginine, Nα-acetyl-NG,NG-dimethylarginine, and Nα-acetyl-N?,N?,N?-trimethyllysine. 相似文献
10.
Pea dehydrins: identification,characterisation and expression 总被引:3,自引:0,他引:3
An antiserum raised against dehydrin from maize (Zea mays) recognised several polypeptides in extracts of pea (Pisum sativum) cotyledons. A cDNA expression library was prepared from mRNA of developing cotyledons, screened with the antiserum and positive clones were purified and characterised. The nucleotide sequence of one such clone, pPsB12, contained an open reading frame which would encode a polypeptide with regions of significant amino acid sequence similarity to dehydrins from other plant species.The deduced amino acid sequence of the pea dehydrin encoded by B12 is 197 amino acids in length, has a high glycine content (25.9%), lacks tryptophan and is highly hydrophilic. The polypeptide has an estimated molecular mass of 20.4 kDa and pI=6.4. An in vitro synthesised product from the clone comigrates with one of the in vivo proteins recognised by the antiserum.A comparison of the pea dehydrin sequence with sequences from other species revealed conserved amino acid regions: an N-terminal DEYGNP and a lysine-rich block (KIKEKLPG), both of which are present in two copies. Unexpectedly, pea dehydrin lacks a stretch of serine residues which is conserved in other dehydrins.B12 mRNA and dehydrin proteins accumulated in dehydration-stressed seedlings, associated with elevated levels of endogenous abscisic acid (ABA). Applied ABA induced expression of dehydrins in unstressed seedlings. Dehydrin expression was rapidly reversed when seedlings were removed from the stress or from treatment with ABA and placed in water.During pea cotyledon development, dehydrin mRNA and proteins accumulated in mid to late embryogenesis. Dehydrin proteins were some of the most actively synthesised at about the time of maximum fresh weight and represent about 2% of protein in mature cotyledons. 相似文献