全文获取类型
收费全文 | 3486篇 |
免费 | 293篇 |
国内免费 | 4篇 |
出版年
2023年 | 14篇 |
2022年 | 16篇 |
2021年 | 52篇 |
2020年 | 46篇 |
2019年 | 57篇 |
2018年 | 59篇 |
2017年 | 58篇 |
2016年 | 88篇 |
2015年 | 127篇 |
2014年 | 168篇 |
2013年 | 179篇 |
2012年 | 240篇 |
2011年 | 304篇 |
2010年 | 182篇 |
2009年 | 149篇 |
2008年 | 203篇 |
2007年 | 237篇 |
2006年 | 190篇 |
2005年 | 196篇 |
2004年 | 171篇 |
2003年 | 169篇 |
2002年 | 161篇 |
2001年 | 51篇 |
2000年 | 25篇 |
1999年 | 47篇 |
1998年 | 42篇 |
1997年 | 30篇 |
1996年 | 25篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 40篇 |
1992年 | 17篇 |
1991年 | 28篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 18篇 |
1982年 | 19篇 |
1981年 | 29篇 |
1980年 | 20篇 |
1979年 | 15篇 |
1977年 | 18篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1974年 | 16篇 |
1973年 | 13篇 |
排序方式: 共有3783条查询结果,搜索用时 217 毫秒
51.
Arnold Coffer Vincent Cavailles Phillip Knowles Darryl Pappin 《The Journal of steroid biochemistry and molecular biology》1996,58(5-6):467-477
Biologically active, mouse estrogen receptor hormone-binding domain (residues 313–599) overexpressed in Escherichia coli was purified to apparent homogeneity as a single component with a molecular mass of 32.831 kDa determined by electrospray ionization mass spectrometry, and was identical to the mass predicted from the amino acid sequence. The intact domain was isolated using a novel, rapid purification scheme without recourse to any chromatographic process. Pure ERhbd maintained both high affinity estradiol binding (at optimum pH 8.0) and specificity for estrogens and anti-estrogens. The steroid-binding domain sedimented as a 4S component in the presence or absence of bound [3H]estradiol and at 2S in the presence of urea. The molecular mass of the 4S steroid unoccupied ERhbd (from dynamic light scattering) was 72 kDa, suggesting that the pure, unlabelled ERhbd formed homodimers. Steroid-labelled ERhbd electrofocussed as a single, acidic component at a pI of 5.6. Binding of ERhbd to [3H]estradiol was unaffected by Ca2+ and Mg2+ ions up to 1 mM but was significantly inhibited by Zn2+ ions at concentrations above 10 μM, an effect reversed by EDTA. 相似文献
52.
Gene identification in a complex chromosomal continuum by local genomic cross-referencing 总被引:8,自引:0,他引:8
Zoya Avramova Alexander Tikhonov Phillip SanMiguel Young-Kwan Jin Changnong Liu Sung-Sick Woo Rod A. Wing Jeffrey L. Bennetzen 《The Plant journal : for cell and molecular biology》1996,10(6):1163-1168
Most higher plants have complex genomes containing large quantities of repetitive DNA interspersed with low-copy-number sequences. Many of these repetitive DNAs are mobile and have homology to RNAs in various cell types. This can make it difficult to identify the genes in a long chromosomal continuum. It was decided to use genic sequence conservation and grass genome co-linearity as tools for gene identification. A bacterial artificial chromosome (BAC) clone containing sorghum genomic DNA was selected using a maize Adh1 probe. The 165 kb sorghum BAC was tested for hybridization to a set of clones representing the contiguous 280 kb of DNA flanking maize Adh1. None of the repetitive maize DNAs hybridized, but most of the low-copy-number sequences did. A low-copy-number sequence that did cross-hybridize was found to be a gene, while one that did not was found to be a low-copy-number retrotransposon that was named Reina. Regions of cross-hybridization were co-linear between the two genomes, but closer together in the smaller sorghum genome. These results indicate that local genomic cross-referencing by hybridization of orthologous clones can be an efficient and rapid technique for gene identification and studies of genome organization. 相似文献
53.
Rudge Simon A. Hughes Phillip J. Brown Graham R. Michell Robert H. Kirk Christopher J. 《Molecular and cellular biochemistry》1995,149(1):161-174
Molecular and Cellular Biochemistry - The testis is a complex organ in which local control is achieved by signalling between its constituent cells. Herein we describe the responses of cultured rat... 相似文献
54.
Phillip A Patten Russell J Howard Willem PC Stemmer 《Current opinion in biotechnology》1997,8(6):724-733
DNA shuffling is a practical process for directed molecular evolution which uses recombination to dramatically accelerate the rate at which one can evolve genes. Single and multigene traits that require many mutations for improved phenotypes can be evolved rapidly. DNA shuffling technology has been significantly enhanced in the past year, extending its range of applications to small molecule pharmaceuticals, pharmaceutical proteins, gene therapy vehicles and transgenes, vaccines and evolved viruses for vaccines, and laboratory animal models. 相似文献
55.
Newt Myotubes Reenter the Cell Cycle by Phosphorylation of the Retinoblastoma Protein 总被引:4,自引:0,他引:4 下载免费PDF全文
Elly M. Tanaka Alexander A.F. Gann Phillip B. Gates Jeremy P. Brockes 《The Journal of cell biology》1997,136(1):155-165
Withdrawal from the cell cycle is an essential aspect of vertebrate muscle differentiation and requires the retinoblastoma (Rb) protein that inhibits expression of genes needed for cell cycle entry. It was shown recently that cultured myotubes derived from the Rb−/−mouse reenter the cell cycle after serum stimulation (Schneider, J.W., W. Gu, L. Zhu, V. Mahdavi, and B. Nadal-Ginard. 1994. Science (Wash. DC). 264:1467– 1471). In contrast with other vertebrates, adult urodele amphibians such as the newt can regenerate their limbs, a process involving cell cycle reentry and local reversal of differentiation. Here we show that myotubes formed in culture from newt limb cells are refractory to several growth factors, but they undergo S phase after serum stimulation and accumulate 4N nuclei. This response to serum is inhibited by contact with mononucleate cells. Despite the phenotypic parallel with Rb−/− mouse myotubes, Rb is expressed in the newt myotubes, and its phosphorylation via cyclin-dependent kinase 4/6 is required for cell cycle reentry. Thus, the postmitotic arrest of urodele myotubes, although intact in certain respects, can be undermined by a pathway that is inactive in other vertebrates. This may be important for the regenerative ability of these animals. 相似文献
56.
Characterization of Myelin Basic Protein Charge Microheterogeneity in Developing Mouse Brain and in the Transgenic Shiverer Mutant 总被引:2,自引:0,他引:2
Anthony E. Palma Phillip Owh Christopher Fredric Carol Readhead Mario A. Moscarello 《Journal of neurochemistry》1997,69(4):1753-1762
Abstract: Myelin basic protein (MBP) is a highly heterogeneous family of membrane proteins consisting of several isoforms resulting from alternative splicing and charge isomers arising from posttranslational modifications. Although well characterized in the bovine and human species, those in the mouse are not. With the availability of a number of transgenic and knockout mice, the need to understand the chemical nature of the MBPs has become very important. To isolate and characterize the MBP species in murine brain, two methods were adapted for use with the small amounts of MBP available from mice. The first was a scaled-down version of the preparative CM-52 chromatographic system commonly used to isolate MBP charge isomers; the second was an alkaline-urea slab gel technique that required five times less material than the conventional tube gel system and, from these gels, western blots were readily obtained. Murine MBP was resolved into two populations of charge isomers: the 18.5- and 14-kDa isoforms. Isolation and characterization of these charge isomers or components permitted us to assign possible posttranslational modifications to some of them. Component 1 (C-1), the most cationic isomer, had a molecular weight of 14,140.38 ± 0.79. C-2 consisted of two 14-kDa species, 14,136.37 ± 0.74 and 14,204.45 ± 0.70. Two variants, 14,215.57 ± 0.94 and 18,413.57 ± 0.76, constituted C-3. C-4, C-5, and C-8 (the least cationic isomer) each consisted of both 14- and 18.5-kDa isoforms. During myelinogenesis, the 18.5-kDa isoform appeared first (day 4); the 14-kDa isoform appeared at day 16 and subsequently became the dominant isoform. The transgenic shiverer mutant synthesized mainly the 18.5-kDa isoform, but none of the 14-kDa isoform, similar to the 4-day-old mouse. We concluded that the trangenic shiverer was able to initiate myelinogenesis with the 18.5-kDa isoform, but was unable to complete myelinogenesis because of the absence of the 14-kDa isoform. 相似文献
57.
Neville I. Passmore Robert R. Capranica Stephen R. Telford Phillip J. Bishop 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1984,154(2):189-197
Summary A detailed study was conducted of the three-dimensional accuracy of phonotaxis by femaleHyperolius marmoratus. This analysis involved videotape recordings of phonotactic approaches to an elevated loudspeaker through a three-dimensional grid. Females readily resolved the sound source elevation, but the jump error angles describing the precision of approach were considerably greater in this three-dimensional analysis than in the more conventional two-dimensional ground approach analysis. Extensive use was made of visual cues in elevated phonotactic approach and lateral head scanning prior to jumps, often accompanied by vertical changes in head orientation, was frequent. The ability of such small anurans to localize a sound source in both the horizontal and vertical plane is remarkable.On leave from the Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA 相似文献
58.
Robert M. Hudziak Frank A. Laski Uttam L. Rajbhandary Phillip A. Sharp Mario R. Capecchi 《Cell》1982,31(1):137-146
We describe the generation of mammalian cell lines carrying amber suppressor genes. Nonsense mutants in the herpes simplex virus thymidine kinase (HSV tk) gene, the Escherichia coli xanthine-guanine phosphoribosyl transferase (Eco-gpt) gene and the aminoglycoside 3′ phosphotransferase gene of the Tn5 transposon (NPT-II) were isolated and characterized. Each gene was engineered with the appropriate control signals to allow expression in both E. coli and mammalian cells. Expression in E. coli made possible the use of well developed bacterial and phage genetic manipulations to isolate and characterize the nonsense mutants. Once characterized, the nonsense mutants were transferred into mammalian cells by microinjection and used, in turn, to select for amber suppressor genes. Xenopus laevis amber suppressor genes, prepared by site-specific mutagenesis of a normal X. laevis tRNA gene, were microinjected into the above cell lines and selected for the expression of one or more of the amber mutant gene products. The resulting cell lines, containing functional amber suppressor genes, are stable and exhibit normal growth rates. 相似文献
59.
60.
Comparison of metal levels in invertebrate detritivores and their natural diets: Concentration factors reassessed 总被引:2,自引:0,他引:2
Phillip Williamson 《Oecologia》1979,44(1):75-79
Summary Concentration Factors (ppm in animal: ppm in diet) are presented for lead, zinc and cadmium in the snail Cepaea hortensis, and for lead and zinc in the woodlice Oniscus asellus and Philoscia muscorum, sampled at roadside sites. For each species such factors were found to be extremely variable, affected not only by season, and size and/or age of animals, but also by the choice of data used in estimating metal levels in the diet. It is concluded that factors other than seasonal changes in metal levels of senescent vegetation are primarily responsible for withinsite variation in the lead, zinc and cadmium concentrations of invertebrate detritivores. 相似文献