全文获取类型
收费全文 | 5756篇 |
免费 | 465篇 |
出版年
2023年 | 20篇 |
2022年 | 48篇 |
2021年 | 102篇 |
2020年 | 59篇 |
2019年 | 84篇 |
2018年 | 93篇 |
2017年 | 103篇 |
2016年 | 124篇 |
2015年 | 243篇 |
2014年 | 269篇 |
2013年 | 396篇 |
2012年 | 463篇 |
2011年 | 454篇 |
2010年 | 323篇 |
2009年 | 272篇 |
2008年 | 388篇 |
2007年 | 396篇 |
2006年 | 372篇 |
2005年 | 326篇 |
2004年 | 320篇 |
2003年 | 279篇 |
2002年 | 279篇 |
2001年 | 67篇 |
2000年 | 61篇 |
1999年 | 62篇 |
1998年 | 68篇 |
1997年 | 48篇 |
1996年 | 37篇 |
1995年 | 34篇 |
1994年 | 26篇 |
1993年 | 22篇 |
1992年 | 37篇 |
1991年 | 22篇 |
1990年 | 29篇 |
1989年 | 22篇 |
1988年 | 30篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1966年 | 8篇 |
排序方式: 共有6221条查询结果,搜索用时 15 毫秒
51.
Regis Vanderesse Laurent Thevenet Michel Marraud Nicole Boggetto Michele Reboud Catherine Corbier 《Journal of peptide science》2003,9(5):282-299
The aminoxy acids NH2-O-C(alpha)HR-CO2H are much more easily obtained in the enantiomerically pure form than the analogous hydrazino acids NH2-NH-C(alpha)HR-CO2H, and it has been shown that the isosteric amidoxy psi[CO-NH-O] and hydrazide psi[CO-NH-NH] amide surrogates Induce two quite similar gamma-like folded structures. An aminoxy acid can also be N-coupled to a peptide aldehyde to give the aldoxime psi[CH = N-O] link or to a peptide ketone to form the ketoxime psi[CR= N-O] link. The former can be further reduced into the hydroxylamine psi[CH2-NH-O] link which gives rise to reduced amidoxy peptides. The structural properties Induced by these amide surrogates were studied, using IR and NMR spectroscopy, paying particular attention to the Z/E-isomerism of the oxime link. In order to investigate their inhibitory potency, the three amide surrogates were introduced in the Pro3-Val4 and Val4-Ala5 position of Z-Ala1-Ala2-Pro3-Val4-Ala5-Ala6-NHiPr, a substrate which is cleaved in the Val4-Ala5 position by human leukocyte elastase (HLE). The [Val4psi[CO-NH-O]Ala5] analogue was still a substrate, while the [Pro3psi[CO-NH-O]Val4] and [Val4psi[CH = N-O]Ala5] pseudopeptides acted as HLE competitive inhibitors. 相似文献
52.
Rémy Kachadourian Alia Dellagi Jacqueline Laurent Laurent Bricard Gerhard Kunesch Dominique Expert 《Biometals》1996,9(2):143-150
Iron deprivation of Erwinia amylovora CFBP1430, a species causing fire blight on Pomoïdeae, was shown to induce the production of siderophores of the desferrioxamine (dfo) family and two outer membrane polypeptides with apparent molecular weight of about 70 and 80 kDa, respectively. Cyclic dfo E was characterized as the major metabolite. Phage MudIIpR13 insertional mutagenesis and screening on CAS-agar medium yielded three dfo non-producing and one overproducing clones. These clones failed to grow in the presence of the Fe(III) chelator EDDHA and were determined further as dfo and ferrioxamine transport negative mutants, respectively. The transport mutant which appeared to lack the 70 kDa polypeptide in the outer membrane allowed the purification of dfo E. Growth under iron limitation of dfo negative mutants was stimulated with ferrioxamine E and B but not with other ferrisiderophores tested. The host DNA sequence flanking the left terminal part of the MudIIpR13 prophage responsible for the transport mutation was cloned and used to probe a parental gene library by DNA-DNA hybridization. Two recombinant cosmids restoring the transport mutation to normal were identified. Both cosmids also conferred the ability to utilize ferrioxamine B and E as iron sources on a FhuE1 mutant of Escherichia coli. This correlated with the production of an additional polypeptide of 70 kDa in the outer membrane of E. coli transconjugants, thus confirming that this protein serves the ferrioxamine receptor function (FoxR) in E. amylovora.R. Kachadourian and A. Dellagi have contributed equally to this work. 相似文献
53.
54.
Statistical analysis of vertebrate sequences reveals that long genes are scarce in GC-rich isochores 总被引:9,自引:0,他引:9
Laurent Duret Dominique Mouchiroud Christian Gautier 《Journal of molecular evolution》1995,40(3):308-317
We compared the exon/intron organization of vertebrate genes belonging to different isochore classes, as predicted by their GC content at third codon position. Two main features have emerged from the analysis of sequences published in GenBank: (1) genes coding for long proteins (i.e., 500 aa) are almost two times more frequent in GC-poor than in GC-rich isochores; (2) intervening sequences (=sum of introns) are on average three times longer in GC-poor than in GC-rich isochores. These patterns are observed among human, mouse, rat, cow, and even chicken genes and are therefore likely to be common to all warm-blooded vertebrates. Analysis of Xenopus sequences suggests that the same patterns exist in cold-blooded vertebrates. It could be argued that such results do not reflect the reality because sequence databases are not representative of entire genomes. However, analysis of biases in GenBank revealed that the observed discrepancies between GC-rich and GC-poor isochores are not artifactual, and are probably largely underestimated. We investigated the distribution of microsatellites and interspersed repeats in introns of human and mouse genes from different isochores. This analysis confirmed previous studies showing that Ll repeats are almost absent from GC-rich isochores. Microsatellites and SINES (Alu, B1, B2) are found at roughly equal frequencies in introns from all isochore classes. Globally, the presence of repeated sequences does not account for the increased intron length in GC-poor isochores. The relationships between gene structure and global genome organization and evolution are discussed. 相似文献
55.
Laurent TC 《Biophysical chemistry》1995,57(1):7-14
Interest in the interaction between proteins and polysaccharides in semidilute systems developed in the late 1950's and early 1960's both in the field of matrix biology and in the construction of new separation techniques. The author gives an account of how his work in the 50's on the characterization of a connective tissue polysaccharide, hyaluronan, led him into studies on polysaccharide networks, sieve effects, molecular exclusion, a theory of gel filtration, solubility of proteins and chemical equilibria in polymer solutions, water and protein homeostatis in vivo, and ordered convectional flow in concentrated polymer systems. 相似文献
56.
Christelle David Laurent Bischoff Hervé Meudal Catherine Llorens-Cortes Bernard Pierre Roques Marie-Claude Fournié-Zaluski 《Letters in Peptide Science》1997,4(4-6):411-414
In order to study the physiological role of aminopeptidase A (APA),several -mercapto--amino acyl dipeptides were synthesized toobtain compounds having a high affinity for APA and a high selectivityversus aminopeptidase N (APN). Sulfonamide and carboxylate moieties whichhave been shown to be recognized by the S1 subsite of theenzyme were introduced on the side chain of the -mercapto--aminoacyl sub-unit, the latter being coupled to dipeptides optimized to interactwith the S1 andS2 subsites by means of combinatorialchemistry. Good affinities (16 nM) were obtained, the selectivity factorsbeing up to 160-fold versus APN. 相似文献
57.
R. L. Wolff Bernard Comps Anne M. Marpeau Laurent G. Deluc 《Trees - Structure and Function》1997,12(2):113-118
The fatty acid compositions of the seed oils from ten pine species have been established by capillary gas-liquid chromatography
of the methyl esters. With regard to either normal fatty acids or Δ5-olefinic acids, the general pattern of fatty acids did
not differ from that of other pine seed oils reported previously. The main fatty acid was linoleic (9,12–18:2) acid (44.4–57.1%),
followed by either oleic (9–18:1) acid (13.4–24.5%) or pinolenic (5,9,12–18:3) acid (1.5–25.2%). When applying multivariate
analyses to the chemometric data (13 variables) of 49 pine species (ca. 40% of the living pine species), it was possible to
distinguish between several sections: Pinea, Longifolia, Halepensis, Ponderosa-Banksiana, Sylvestris, and Cembra. The latter section was clearly divided into two sub-groups. A few species that presented a low overall content of Δ5-olefinic
acids, and that grow in warm-temperate regions, were isolated from the bulk of other pine species. It is hypothesized that
Δ5-olefinic acids might be related to cold-acclimation.
Received: 5 June 1997 / Accepted: 17 August 1997 相似文献
58.
Marc Lecouvey Céline Frochot Laurent Miclo Piotr Orlewski Michel Marraud Jean-Luc Gaillard Manh Thong Cung Régis Vanderesse 《Letters in Peptide Science》1997,4(4-6):359-364
The conformation of a benzodiazepine-like decapeptide corresponding tothe YLGYLEQLLR fragment of a casein has been examined in a sodium dodecylsulfate micellar medium using circular dichroism, two-dimensional1H NMR spectroscopy and restrained molecular dynamicssimulation. The decapeptide adopts an amphipathic 310-helicoidstructure in which theE6···R10 ionic bridgestabilizes the C-terminus. 相似文献
59.
60.