全文获取类型
收费全文 | 3180篇 |
免费 | 361篇 |
专业分类
3541篇 |
出版年
2022年 | 22篇 |
2021年 | 42篇 |
2020年 | 23篇 |
2019年 | 25篇 |
2018年 | 30篇 |
2017年 | 44篇 |
2016年 | 78篇 |
2015年 | 125篇 |
2014年 | 123篇 |
2013年 | 152篇 |
2012年 | 220篇 |
2011年 | 202篇 |
2010年 | 127篇 |
2009年 | 109篇 |
2008年 | 163篇 |
2007年 | 161篇 |
2006年 | 132篇 |
2005年 | 122篇 |
2004年 | 131篇 |
2003年 | 132篇 |
2002年 | 136篇 |
2001年 | 68篇 |
2000年 | 62篇 |
1999年 | 60篇 |
1998年 | 42篇 |
1997年 | 39篇 |
1996年 | 43篇 |
1995年 | 31篇 |
1994年 | 27篇 |
1993年 | 34篇 |
1992年 | 53篇 |
1991年 | 51篇 |
1990年 | 50篇 |
1989年 | 48篇 |
1988年 | 48篇 |
1987年 | 46篇 |
1986年 | 37篇 |
1985年 | 44篇 |
1984年 | 37篇 |
1983年 | 31篇 |
1982年 | 28篇 |
1981年 | 19篇 |
1980年 | 30篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1976年 | 20篇 |
1975年 | 30篇 |
1973年 | 23篇 |
1970年 | 18篇 |
1968年 | 24篇 |
排序方式: 共有3541条查询结果,搜索用时 15 毫秒
51.
Andrew R. J. Curtis Sophie Headland Susan Lindsay Nicholas S. T. Thomas Eileen Boye Smaragda Kamakari Paul Roustan Maria Anvret Jan Wahlstrom Gillian McCarthy Angus J. Clarke Shomi Bhattacharya 《Human genetics》1993,90(5):551-555
Four families, each with two individuals affectecd by Rett Syndrome (RS), were analysed using restriction fragment lenght polymorphisms and microsatellite markers from the X chromosome. In two of the families, X-linked dominant inheritance of the RS defect from a germinally mosaic mother could be assumed. Therefore, maternal X chromosome markers showing discordant inheritance were used to exclude regions of the X chromosome as locations of the RS gene. Much of the short arm could be excluded, including regions containing three candidate genes, OTC, synapsin 1 and synaptophysin. Although most of the long arm was inherited in common it was possible to exclude a centromeric region. Inheritance of X chromosome markers is also presented for two families with affected aunt-niece pairs, one of which has not been previously studied at the DNA level. 相似文献
52.
Abstract. Machair vegetation is reported for the first time from New Zealand. The habitat is similar to that of British machairs in climate, topography and generally in soil. pH and CaCO3 content are much lower through most of the sequence, though this difference may partly reflect the greater disturbance of British machair. Sea machair is present, predominantly comprising native species. This grades into machair proper, which contains many species found also in British machair. The machair includes Ammophila-occupied hillocks, a feature typical of British machair. Machair marsh is also present. 相似文献
53.
Shirley P. Tolley Gideon J. Davies Mark O'Shea Mark I. Cockett Andrew J. P. Docherty Gillian Murphy 《Proteins》1993,17(4):435-437
A nonglycosylated (N30QN78Q) form of the human tissue inhibitor of metalloproteinases, TIMP-1, has been prepared and crystallized in a form suitable for X-ray diffraction analysis. Small single crystals have been grown using sodium tartrate as a precipitant. The crystals are in space group P21, with cell dimensions a = 35.28, b = 53.95, c = 48.56, and β = 96.0°. There is a single molecule of TIMP-1 in the asymmetric unit. The crystals diffract to at least 2.3 Å resolution. Complete data have been collected to 2.9 Å and a search for heavymetal derivatives is in progress. © 1993 Wiley-Liss, Inc. 相似文献
54.
Jérémy Gauthier Joana Meier Fabrice Legeai Melanie McClure Annabel Whibley Anthony Bretaudeau Hélène Boulain Hugues Parrinello Sam T. Mugford Richard Durbin Chenxi Zhou Shane McCarthy Christopher W. Wheat Florence Piron-Prunier Christelle Monsempes Marie-Christine François Paul Jay Camille Noûs Emma Persyn Emmanuelle Jacquin-Joly Camille Meslin Nicolas Montagné Claire Lemaitre Marianne Elias 《Molecular ecology resources》2023,23(4):872-885
The ithomiine butterflies (Nymphalidae: Danainae) represent the largest known radiation of Müllerian mimetic butterflies. They dominate by number the mimetic butterfly communities, which include species such as the iconic neotropical Heliconius genus. Recent studies on the ecology and genetics of speciation in Ithomiini have suggested that sexual pheromones, colour pattern and perhaps hostplant could drive reproductive isolation. However, no reference genome was available for Ithomiini, which has hindered further exploration on the genetic architecture of these candidate traits, and more generally on the genomic patterns of divergence. Here, we generated high-quality, chromosome-scale genome assemblies for two Melinaea species, M. marsaeus and M. menophilus, and a draft genome of the species Ithomia salapia. We obtained genomes with a size ranging from 396 to 503 Mb across the three species and scaffold N50 of 40.5 and 23.2 Mb for the two chromosome-scale assemblies. Using collinearity analyses we identified massive rearrangements between the two closely related Melinaea species. An annotation of transposable elements and gene content was performed, as well as a specialist annotation to target chemosensory genes, which is crucial for host plant detection and mate recognition in mimetic species. A comparative genomic approach revealed independent gene expansions in ithomiines and particularly in gustatory receptor genes. These first three genomes of ithomiine mimetic butterflies constitute a valuable addition and a welcome comparison to existing biological models such as Heliconius, and will enable further understanding of the mechanisms of adaptation in butterflies. 相似文献
55.
56.
57.
Isotopic fractionation during nitrate uptake by phytoplankton grown in continuous culture 总被引:7,自引:0,他引:7
The isotopic fractionation associated with uptake of NO3by six species of phytoplankton (two diatoms, one cryptophyte,one chlorophyte and two haptophytes) was measured at a varietyof steady-state growth rates in nitrogen-limited continuousculture. The magnitude of the isotopic fractionation factor( 相似文献
58.
Julia C. McNaughton Craig J. Marshall Judith E. Broom Gillian Hughes Wyn A. Jones Peter A. Stockwell George B. Petersen 《Journal of molecular evolution》1995,40(2):127-135
A THE-1 sequence in intron 7 of the human dystrophin gene has been found to represent a new subfamily of THE-1 elements. The sequence is closely related to the MstII family of repetitive sequences and is more like single-copy sequences found in the galago genome than any other THE-1 sequence previously reported. This new THE-1 sequence has been compared with two other complete THE-1 sequences and three related long-terminal repeat elements that we have previously found in intron 7 of the dystrophin gene, and with members of the same family from elsewhere in the primate genome. Parsimony and deletion analysis show that the cluster of THE-1 sequences in intron 7 of the dystrophin gene has arisen from at least three individual insertion events, rather than from the insertion and duplication of a single progenitor sequence.
Correspondence to: G.B. Petersen 相似文献
59.
60.
Naveen Pathak Rodolfo Salas-Auvert Gaël Ruche Marie-hlne Janna David McCarthy Roger G. Harrison 《Proteins》1995,22(2):182-186
Multiple linear regression was used to quantify the dependence of the antimicrobial activity of 13 peptides upon three calculated or experimentally determined parameters: mean hydrophobicity, mean hydrophobic moment, and α-helix content. Mean hydrophobic moment is a measure of the amphiphilicity of peptides in an α-helical conformation. Antimicrobial activity was quantified as the reciprocal of the measured minimal inhibitory concentration (MIC) against Escherichia coli. One of the peptides was magainin 2, and the remainder were novel peptides designed for this study. The multiple linear regression results revealed that the amphiphilicity of the peptides was the most important factor governing anti-microbial activity compared to mean hydrophobicity orα-helix content. A better regression cf the data was obtained using In(1/MIC + constant) as the dependent variable than with either 1/MIC or In(1/MIC). These results should be useful in designing peptides with higher antimicrobial activity. © 1995 Wiley-Liss, Inc. 相似文献