全文获取类型
收费全文 | 1202篇 |
免费 | 95篇 |
出版年
2022年 | 17篇 |
2021年 | 24篇 |
2020年 | 9篇 |
2019年 | 18篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 28篇 |
2015年 | 65篇 |
2014年 | 61篇 |
2013年 | 76篇 |
2012年 | 95篇 |
2011年 | 83篇 |
2010年 | 62篇 |
2009年 | 47篇 |
2008年 | 69篇 |
2007年 | 65篇 |
2006年 | 55篇 |
2005年 | 55篇 |
2004年 | 55篇 |
2003年 | 40篇 |
2002年 | 34篇 |
2001年 | 23篇 |
2000年 | 26篇 |
1999年 | 19篇 |
1998年 | 26篇 |
1997年 | 16篇 |
1996年 | 21篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1968年 | 3篇 |
1961年 | 3篇 |
排序方式: 共有1297条查询结果,搜索用时 15 毫秒
71.
Tong TY Goh VH Tain CF Mok H Tsang S 《Canadian journal of physiology and pharmacology》2000,78(6):453-456
Hyperstimulation in the rat using pregnant mares' serum gonadotrophin (PMSG) has been known to cause death in pre-implantation embryos, as well as enhancement of oestradiol production. This study examines the effect of oestradiol, in levels that are found in hyperstimulated pregnant rats, on pre-implantation embryonic development. Using a simplified in vitro system, 2-cell embryos retrieved from rats on the 2nd day of pregnancy were cultured in rat two-cell embryo culture medium (R2ECM) containing pharmacological doses of oestradiol for 96 h and scored daily in the morning. Three ngxmL(-1) oestradiol reduced the incidence of >8-cell embryos to morulae on the 5th day and blastocysts on the 6th day of development. Most embryos were retarded at the lower cell stages on the 5th day and degenerated by the 6th day. None of the blastocysts expanded on the last day of culture. Fifteen ngxmL(-1) oestradiol accelerated embryo development on the 3rd day but retarded development on the 4th day, and increased the incidence of degenerated embryos by the 5th and 6th day of development. These results suggest that the elevated oestradiol may constitute a mechanism by which PMSG induces death in pre-implantation rat embryos, possibly via a direct action on the embryos. 相似文献
72.
73.
Two directly repeated sequences of the IS elements IS1489v1 and IS1489v2 flank the benzene dioxygenase (bedC1C2BA) and the cis-benzene dihydrodiol dehydrogenase (bedD) genes on the catabolic plasmid pHMT112 in Pseudomonas putida ML2, forming a Class-I-type composite transposon, Tn5542. Both IS1489v1 and IS1489v2 contain an identical 1371-bp open reading frame, tnpA, that is preceded by a possible ribosome binding site. The tnpA gene of IS1489v1 is bound by a pair of 40-bp imperfect inverted repeats while that of IS1489v2 is flanked only by the left inverted repeat. The tnpA gene codes for a putative 53-kDa polypeptide of 456 amino acids bearing similarity to transposases encoded on IS elements of P. alcaligenes, P. aeruginosa, P. stutzeri, and Serratia marcescens. The basic nature of the putative TnpA protein with a deduced pI of 8.93 is typical of IS-encoded transposases. Similar to other IS elements, an outward facing promoter was detected at the right end of IS1489v1. Experiments involving the suicide vector, pKNG101, failed to show transposition of Tn5542. 相似文献
74.
Genetic variation among 12 populations of the American chestnut (Castanea dentata) was investigated. Population genetic parameters estimated from allozyme variation suggest that C. dentata at both the population and species level has narrow genetic diversity as compared to other species in the genus. Average expected heterozygosity was relatively low for the population collected in the Black Rock Mountain State Park, Georgia (He = 0.096 +/- 0.035), and high for the population in east central Alabama (He = 0.196 +/- 0.048). Partitioning of the genetic diversity based on 18 isozyme loci showed that ~10% of the allozyme diversity resided among populations. Cluster analysis using unweighted pair-group method using arithmetric averages of Rogers' genetic distance and principal components analysis based on allele frequencies of both isozyme and RAPD loci revealed four groups: the southernmost population, south-central Appalachian populations, north-central Appalachian populations, and northern Appalachian populations. Based on results presented in this study, a conservation strategy and several recommendations related to the backcross breeding aimed at restoring C. dentata are discussed. 相似文献
75.
76.
S.H.M. Goh A.N. Mabbett J.P. Welch S.J. Hall A.G. McEwan 《Letters in applied microbiology》2009,48(4):486-492
Aims: To investigate the microbial ecology of three facultative swine waste lagoons.
Methods and Results: Phylogenetic analysis of sequences in a 16S rRNA gene clone library and fluorescence in situ hybridization (FISH) analyses were used to assess bacterial diversity in a swine waste lagoon. FISH analysis and Gram-staining were used to compare the microbial communities of all three swine waste lagoons. Six operational taxonomic units were in high relative abundance and corresponded to the following phylotypes; Thiolamprovum , Verrucomicrobia , Acholeplasma , Turicibacter , Clostridium and Bacteroides . PCR was employed to detect the genes apsA and dsrAB which encode for enzymes specifically associated with dissimilatory sulfate-reduction within sulfate-reducing bacteria (SRB). Amplification of these genes confirmed their presence within the lagoons.
Conclusions: All lagoons were dominated by purple sulfur bacteria, affiliated to Thiolamprovum pedioforme . The molecular identification of fermentative bacteria and SRB indicate the following metabolic processes within such facultative ponds: sulfur-cycling, fermentation, inter-species hydrogen transfer and carbon cycling.
Significance and Impact of the Study: This study provides the first molecular evidence for the existence of a sulfur cycle which is linked to phototrophic sulfide oxidation by purple bacteria and organotrophic sulfate-reduction by SRB. 相似文献
Methods and Results: Phylogenetic analysis of sequences in a 16S rRNA gene clone library and fluorescence in situ hybridization (FISH) analyses were used to assess bacterial diversity in a swine waste lagoon. FISH analysis and Gram-staining were used to compare the microbial communities of all three swine waste lagoons. Six operational taxonomic units were in high relative abundance and corresponded to the following phylotypes; Thiolamprovum , Verrucomicrobia , Acholeplasma , Turicibacter , Clostridium and Bacteroides . PCR was employed to detect the genes apsA and dsrAB which encode for enzymes specifically associated with dissimilatory sulfate-reduction within sulfate-reducing bacteria (SRB). Amplification of these genes confirmed their presence within the lagoons.
Conclusions: All lagoons were dominated by purple sulfur bacteria, affiliated to Thiolamprovum pedioforme . The molecular identification of fermentative bacteria and SRB indicate the following metabolic processes within such facultative ponds: sulfur-cycling, fermentation, inter-species hydrogen transfer and carbon cycling.
Significance and Impact of the Study: This study provides the first molecular evidence for the existence of a sulfur cycle which is linked to phototrophic sulfide oxidation by purple bacteria and organotrophic sulfate-reduction by SRB. 相似文献
77.
J. Andy Rakestraw Stephen L. Sazinsky Andrea Piatesi Eugene Antipov K. Dane Wittrup 《Biotechnology and bioengineering》2009,103(6):1192-1201
Because of its eukaryotic nature, simple fermentation requirements, and pliable genetics, there have been many attempts at improving recombinant protein production in Saccharomyces cerevisiae. These strategies typically involve altering the expression of a native protein thought to be involved in heterologous protein trafficking. Usually, these approaches yield three‐ to tenfold improvements over wild‐type strains and are almost always specific to one type of protein. In this study, a library of mutant alpha mating factor 1 leader peptides (MFα1pp) is screened for the enhanced secretion of a single‐chain antibody. One of the isolated mutants is shown to enhance the secretion of the scFv up to 16‐fold over wild type. These leaders also confer a secretory improvement to two other scFvs as well as two additional, structurally unrelated proteins. Moreover, the improved leader sequences, combined with strain engineering, allow for a 180‐fold improvement over previous reports in the secretion of full‐length, functional, glycosylated human IgG1. The production of full‐length IgG1 at milligram per liter titers in a simple, laboratory‐scale system will significantly expedite drug discovery and reagent synthesis while reducing antibody cloning, production, and characterization costs. Biotechnol. Bioeng. 2009;103: 1192–1201. © 2009 Wiley Periodicals, Inc. 相似文献
78.
Developing core outcome set for vitiligo clinical trials: international e‐Delphi consensus
下载免费PDF全文
![点击此处可从《Pigment cell & melanoma research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Viktoria Eleftheriadou Kim Thomas Nanja van Geel Iltefat Hamzavi Henry Lim Tamio Suzuki Ichiro Katayama Tag Anbar Marwa Abdallah Laïla Benzekri Yvon Gauthier John Harris Caio Cesar Silva de Castro Amit Pandya Boon Kee Goh Cheng‐Che E. Lan Naoki Oiso Ahmed Al Issa Samia Esmat Caroline Le Poole Ai‐Young Lee Davinder Parsad Alain Taieb Mauro Picardo Khaled Ezzedine 《Pigment cell & melanoma research》2015,28(3):363-369
79.
Ryan Haryadi Steven Ho Yee Jiun Kok Helen X. Pu Lu Zheng Natasha A. Pereira Bin Li Xuezhi Bi Lin-Tang Goh Yuansheng Yang Zhiwei Song 《PloS one》2015,10(2)
Translocation of a nascent protein from the cytosol into the ER mediated by its signal peptide is a critical step in protein secretion. The aim of this work was to develop a platform technology to optimize the signal peptides for high level production of therapeutic antibodies in CHO cells. A database of signal peptides from a large number of human immunoglobulin (Ig) heavy chain (HC) and kappa light chain (LC) was generated. Most of the HC signal peptides contain 19 amino acids which can be divided into three domains and the LC signal peptides contain 22 amino acids. The signal peptides were then clustered according to sequence similarity. Based on the clustering, 8 HC and 2 LC signal peptides were analyzed for their impacts on the production of 5-top selling antibody therapeutics, namely, Herceptin, Avastin, Remicade, Rituxan, and Humira. The best HC and LC signal peptides for producing these 5 antibodies were identified. The optimized signal peptides for Rituxan is 2-fold better compared to its native signal peptides which are available in the public database. Substitution of a single amino acid in the optimized HC signal peptide for Avastin reduced its production significantly. Mass spectrometry analyses revealed that all optimized signal peptides are accurately removed in the mature antibodies. The results presented in this report are particularly important for the production of these 5 antibodies as biosimilar drugs. They also have the potential to be the best signal peptides for the production of new antibodies in CHO cells. 相似文献
80.
Dane A. Crossley II Sonnet S. Jonker James W. Hicks Kent L. Thornburg 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(7):1057-1065
Angiotensin II (Ang II) is an important regulator of cardiovascular function in adult vertebrates. Although its role in regulating
the adult system has been extensively investigated, the cardiovascular response to Ang II in embryonic vertebrates is relatively
unknown. We investigated the potential of Ang II as a regulator of cardiovascular function in embryonic chickens, which lack
central nervous system control of cardiovascular function throughout the majority of incubation. The cardiovascular response
to Ang II in embryonic chickens was investigated over the final 50% of their development. Ang II produced a dose-dependent
increase in arterial pressure on each day of development studied, and the response increased in intensity as development progressed.
The Ang II type-1 receptor nonspecific competitive peptide antagonist [Sar1 ile8] Ang II blocked the cardiovascular response to subsequent injections of Ang II on day 21 only. The embryonic pressure response
to Ang II (hypertension only) differed from that of adult chickens, in which initial hypotension is followed by hypertension.
The constant level of gene expression for the Ang II receptor, in conjunction with an increasing pressure response to the
peptide, suggests that two Ang II receptor subtypes are present during chicken development. Collectively, the data indicate
that Ang II plays an important role in the cardiovascular development of chickens; however, its role in maintaining basal
function requires further study. 相似文献