全文获取类型
收费全文 | 3790篇 |
免费 | 187篇 |
国内免费 | 2篇 |
出版年
2023年 | 10篇 |
2022年 | 27篇 |
2021年 | 64篇 |
2020年 | 38篇 |
2019年 | 52篇 |
2018年 | 78篇 |
2017年 | 74篇 |
2016年 | 105篇 |
2015年 | 157篇 |
2014年 | 185篇 |
2013年 | 254篇 |
2012年 | 260篇 |
2011年 | 267篇 |
2010年 | 165篇 |
2009年 | 155篇 |
2008年 | 216篇 |
2007年 | 204篇 |
2006年 | 213篇 |
2005年 | 184篇 |
2004年 | 196篇 |
2003年 | 207篇 |
2002年 | 170篇 |
2001年 | 47篇 |
2000年 | 47篇 |
1999年 | 43篇 |
1998年 | 41篇 |
1997年 | 27篇 |
1996年 | 34篇 |
1995年 | 28篇 |
1994年 | 18篇 |
1993年 | 27篇 |
1992年 | 30篇 |
1991年 | 23篇 |
1990年 | 24篇 |
1989年 | 14篇 |
1988年 | 39篇 |
1987年 | 21篇 |
1986年 | 33篇 |
1985年 | 21篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1979年 | 13篇 |
1977年 | 7篇 |
1975年 | 11篇 |
1974年 | 17篇 |
1973年 | 15篇 |
1972年 | 20篇 |
1971年 | 12篇 |
1967年 | 6篇 |
排序方式: 共有3979条查询结果,搜索用时 15 毫秒
41.
Zaw Lin Shinji Yamasaki Hisao Kurazono Mari Ohmura Tadahiro Karasawa Takahiro Inoue Seisuke Sakamoto Takahiro Suganami Tomohiro Takeoka Yoshihiro Taniguchi Yoshifumi Takeda 《Microbiology and immunology》1993,37(6):451-459
We cloned and sequenced two new Verotoxin 2 (VT2) variant genes: one from an Escherichia coli strain from a case of bovine diarrhea and the other from an E. coli strain from a patient with diarrhea. The nucleotide and amino acid sequences of these two genes were highly homologous with, but distinct from those of the VT2, VT2vha, VT2vhb, SLT-IIv (VT2vp1) and SLT-IIva (VT2vp2) genes. Their nucleotide sequences were much more closely homologous to that of VT2vh than to that of VT2vp. Search for these two new genes in other Verocytotoxin-producing E. coli strains resulted in the isolation of 2 strains carrying one of the new VT2 variant genes, one strain from Tokyo and the other from Canada. 相似文献
42.
Myoglobin was isolated from the radular muscle of the chitonLiolophura japonica, a primitive archigastropodic mollusc.Liolophura contains three monomeric myoglobins (I, II, and III), and the complete amino acid sequence of myoglobin I has been determined. It is composed of 145 amino acid residues, and the molecular mass was calculated to be 16,070 D. The E7 distal histidine, which is replaced by valine or glutamine in several molluscan globins, is conserved inLiolophura myoglobin. The autoxidation rate at physiological conditions indicated thatLiolophura oxymyoglobin is fairly stable when compared with other molluscan myoglobins. The amino acid sequence ofLiolophura myoglobin shows low homology (11–21%) with molluscan dimeric myoglobins and hemoglobins, but shows higher homology (26–29%) with monomeric myoglobins from the gastropodic molluscsAplysia, Dolabella, andBursatella. A phylogenetic tree was constructed from 19 molluscan globin sequences. The tree separated them into two distinct clusters, a cluster for muscle myoglobins and a cluster for erythrocyte or gill hemoglobins. The myoglobin cluster is divided further into two subclusters, corresponding to monomeric and dimeric myoglobins, respectively.Liolophura myoglobin was placed on the branch of monomeric myoglobin lineage, showing that it diverged earlier from other monomeric myoglobins. The hemoglobin cluster is also divided into two subclusters. One cluster contains homodimeric, heterodimeric, tetrameric, and didomain chains of erythrocyte hemoglobins of the blood clamsAnadara, Scapharca, andBarbatia. Of special interest is the other subcluster. It consists of three hemoglobin chains derived from the bacterial symbiont-harboring clamsCalyptogena andLucina, in which hemoglobins are supposed to play an important role in maintaining the symbiosis with sulfide bacteria. 相似文献
43.
Ota Yoko; Ario Takeshi; Hayashi Koji; Nakagawa Tsuyoshi; Hattori Tsukaho; Maeshima Masayoshi; Asahi Tadashi 《Plant & cell physiology》1992,33(3):225-232
Catalases purified from endosperm glyoxysomes and non-specializedmicrobodies from hypocotyls of castor bean seedlings differedin their specific activity [90164 and 0.894.9kunits (mg protein)1, respectively] and in their constituentsubunits [two subunits of 54 and 56 kDa for the endosperm enzymeand only one of 56 kDa for the hypocotyl enzyme]. Immunoblotanalysis also showed that particulate fractions from the endospermsand from etiolated and green cotyledons contained two catalasesubunits of 54 and 56 kDa, whereas such fractions from the hypocotylsand roots contained only the 56-kDa subunit. Leaf peroxisomesfrom green leaves had two catalase subunits of around 55 kDaeach. Results of translation in vitro indicated that the 54-and 56-kDa subunits were translated from distinct mRNAs andlevels of both mRNAs increased in the endosperms during germination,prior to increases in levels of catalase proteins. In the hypocotyls,the 56-kDa subunit seemed to be synthesized constitutively.
1Present addresses: YO, Toyota Central Institute, 31-9 Musashizuka,Nagabuchi, Nagakute, Aichi 480-11, Japan 相似文献
44.
Characterization of two mannose-binding protein cDNAs from rhesus monkey (Macaca mulatta): structure and evolutionary implications 总被引:3,自引:0,他引:3
Mannose-binding proteins (MBPs), members of the collectin family,have been implicated as lectin opsonins for various virusesand bacteria. Two distinct but related MBPs, MBP-A and MBP-C,with -55% identity at the amino acid level, have been previouslycharacterized from rodents. In humans, however, only one formof MBP has been characterized. In this paper we report studieselucidating the evolution of primate MBPs. ELISA and Westernblot analyses indicated that rhesus and cynomolgus monkeys havetwo forms of MBP in their sera, while chimpanzees have onlyone form, similar to humans. Two distinct MBP cDNA clones wereisolated and characterized from a rhesus monkey liver cDNA library.Rhesus MBP-A is closely related to the mouse and rat MBP-A,showing 77% and 75% identity at the amino acid level, respectively.Rhesus MBP-A also has three cysteines at the N-terminus, similarto mouse and rat MBP-A and human MBP. Rhesus MBP-C shares 90%identity with the human MBP at the amino acid level and hasthree cysteines at the N-terminus, in contrast to two cysteineresidues found in rodent MBP-C. A stretch of nine amino acidsclose to the N-terminus, absent in both mouse and rat MBP-A,but present in rodent MBP-C, chicken and human MBPs, is alsofound in the rhesus MBP-A. The phylogenetic analysis of rhesusand other mammalian MBPs, coupled with the serological datasuggest that at least two distinct MBP genes existed prior tomammalian radiation and the hominoid ancestor apparently lostone of these genes or failed to express it. collectin rhesus monkey mannose-binding protein MBP cDNA mannan-binding protein 相似文献
45.
The nucleotide sequence data reported in this paper have been submitted to the GSDB, DDBJ, EMBL, and NCBI nucleotide sequence databases and have been assigned the accession numbers D49841 (RCD28), D49844 (RCTLA-4), D49842 (RCD80), and D49843 (RCD86) 相似文献
46.
The nucleotide sequences of one constant (C), six variable (V), and two joining (J) gene segments coding for the rabbit T-cell receptor gamma chain (Tcrg) were determined by directly sequencing fragments amplified by the cassette-ligation mediated polymerase chain reaction. The Tcrg-C gene segment did not encode a cysteine residue for connection to the Tcr delta chain in the connecting region, and two variant forms of the Tcrg-C gene segment were generated by alternative splicing, like the human Tcrg-C2 gene. Five of six rabbit Tcrg-V gene segments belonged to the same family and displayed similarity to five productive human Tcrg-V1 family genes as well as the mouse Tcrg-V5 gene. The remaining rabbit Tcrg-V gene segment displayed similarity to the human Tcrg-V3 gene. Both rabbit Tcrg-J gene segments displayed similarity to the human Tcrg-J2.1 and 2.3, respectively. These findings suggested that the genomic organization of rabbit Tcrg genes is more similar to that of human than of mouse Tcrg genes.The nucleotide sequence data reported in this paper have been submitted to the GSDB, DDBJ, EMBL, and NCBI nucleotide sequence databases and have been assigned the accession numbers D38134-D38144 and D42090 相似文献
47.
Host range phenotype induced by mutations in the internal ribosomal entry site of poliovirus RNA. 总被引:3,自引:2,他引:1
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
K Shiroki T Ishii T Aoki Y Ota W X Yang T Komatsu Y Ami M Arita S Abe S Hashizume A Nomoto 《Journal of virology》1997,71(1):1-8
Most poliovirus strains infect only primates. The host range (HR) of poliovirus is thought to be primarily determined by a cell surface molecule that functions as poliovirus receptor (PVR), since it has been shown that transgenic mice are made poliovirus sensitive by introducing the human PVR gene into the genome. The relative levels of neurovirulence of polioviruses tested in these transgenic mice were shown to correlate well with the levels tested in monkeys (H. Horie et al., J. Virol. 68:681-688, 1994). Mutants of the virulent Mahoney strain of poliovirus have been generated by disruption of nucleotides 128 to 134, at stem-loop II within the 5' noncoding region, and four of these mutants multiplicated well in human HeLa cells but poorly in mouse TgSVA cells that had been established from the kidney of the poliovirus-sensitive transgenic mouse. Neurovirulence tests using the two animal models revealed that these mutants were strongly attenuated only in tests with the mouse model and were therefore HR mutants. The virus infection cycle in TgSVA cells was restricted by an internal ribosomal entry site (IRES)-dependent initiation process of translation. Viral protein synthesis and the associated block of cellular protein synthesis were not observed in TgSVA cells infected with three of four HR mutants and was evident at only a low level in the remaining mutant. The mutant RNAs were functional in a cell-free protein synthesis system from HeLa cells but not in those from TgSVA and mouse neuroblastoma NS20Y cells. These results suggest that host factor(s) affecting IRES-dependent translation of poliovirus differ between human and mouse cells and that the mutant IRES constructs detect species differences in such host factor(s). The IRES could potentially be a host range determinant for poliovirus infection. 相似文献
48.
Xiaoliang Liu Akemi Ota Michiko Watanabe Shigeharu Ueda Atsushi Saitoh Hideo Shinagawa Atsuo Nakata Takashi Kurimura Xiaoui Wang Yu Zhao Kiyoshi Kondo Jiro Seki Shinichi Miyake Nobuo Sakato Hajime Fujio 《Microbiology and immunology》1995,39(10):775-785
We investigated the murine antibody response to recombinant p17 (rp17) of human immunodeficiency virus type 1 (HIV-1) and the human antibody response directed to p17 in HIV-1 infection. Three large peptides covering residues 12-29, 53-87 and 87-115 of p17 were synthesized. The cysteine residues 57 and 87 of peptide 53-87 were reoxidized to form a disulfide bridge. Eighteen out of 19 murine monoclonal anti-rp17 antibodies had relatively high affinities (KA = 1.9 × 105?1.4 × 108 M?1) with one of the 3 p17 peptides in the liquid phase. Each monoclonal antibody reacted only with one particular peptide and had no reactivity with the other 2 p17 peptides. All the monoclonal antibodies reacted with rp17 in the liquid phase with a reasonable degree of affinity (KA = 2.0 × 105?1.8 × 107 M?1). Four HIV-1 carrier sera, which were positive in ELISA using rp17 as the antigen, reacted positively in an ELISA using 3 p17 peptides which were used to titrate murine monoclonal antibodies. Murine monoclonal antibodies having specificity for the 3 p17 peptides stained live HIV-1-infected cells by means of indirect membrane immunofluorescence, irrespective of their specificity. This suggests that the various portions of p17 (at least 3 regions of p17) were exposed on the surface of live infected cells, probably as short polypeptide chains. 相似文献
49.
Positive selection is a general phenomenon in the evolution of abalone sperm lysin 总被引:36,自引:21,他引:15
Lysin is a 16kDa acrosomal protein used by abalone sperm to create a hole
in the egg vitelline envelope (VE). The interaction of lysin with the VE is
species-selective and is one step in the multistep fertilization process
that restricts heterospecific (cross-species) fertilization. For this
reason, the evolution of lysin could play a role in establishing prezygotic
reproductive isolation between species. Previously, we sequenced sperm
lysin cDNAs from seven California abalone species and showed that positive
Darwinian selection promotes their divergence. In this paper an additional
13 lysin sequences are presented representing species from Japan, Taiwan,
Australia, New Zealand, South Africa, and Europe. The total of 20 sequences
represents the most extensive analysis of a fertilization protein to date.
The phylogenetic analysis divides the sequences into two major clades, one
composed of species from the northern Pacific (California and Japan) and
the other composed of species from other parts of the world. Analysis of
nucleotide substitution demonstrates that positive selection is a general
process in the evolution of this fertilization protein. Analysis of
nucleotide and codon usage bias shows that neither parameter can account
for the robust data supporting positive selection. The selection pressure
responsible for the positive selection on lysin remains unknown.
相似文献
50.
Takahiro Morio Hiroyuki Adachi Kazuo Sutoh Kaichiro Yanagisawa Yoshimasa Tanaka 《Journal of plant research》1995,108(1):111-114
Using a plasmid pBsr2 which carries a blasticidin S-resistant gene, we have improved the method of REMI (restriction enzyme-mediated
integration) provided for insertional mutagenesis inDictyostelium discoideum (bsr-REMI). To confirm usefulness of thebsr-REMI, transformation efficiency, copy number of integrated DNA, and randomness of integration into genome were examined. 相似文献