全文获取类型
收费全文 | 629篇 |
免费 | 66篇 |
专业分类
695篇 |
出版年
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 31篇 |
2012年 | 29篇 |
2011年 | 37篇 |
2010年 | 37篇 |
2009年 | 27篇 |
2008年 | 22篇 |
2007年 | 27篇 |
2006年 | 28篇 |
2005年 | 24篇 |
2004年 | 17篇 |
2003年 | 23篇 |
2002年 | 24篇 |
2001年 | 19篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1967年 | 5篇 |
1965年 | 5篇 |
排序方式: 共有695条查询结果,搜索用时 15 毫秒
61.
Ricardo A. Scrosati Amanda S. Knox Nelson Valdivia Markus Molis 《Helgoland Marine Research》2011,65(2):91-102
Environmental stress affects species richness and diversity in communities, but the precise form of the relationship is unclear.
We tested an environmental stress model (ESM) that predicts a unimodal pattern for total richness and diversity in local communities
across the full stress gradient where a regional biota can occur. In 2008, we measured richness and diversity (considering
all macrobenthic species) across the entire intertidal range on three rocky shores on Helgoland Island, Germany. Intertidal
elevation is known to be positively related to abiotic stress. Since Helgoland is between the northern and southern biogeographic
boundaries for the cold-temperate NE Atlantic intertidal biota, it exhibits low stress levels for this biota at low elevations
and high stress at high elevations because of long (>6 h) emersion times. Thus, we predicted a unimodal trend for richness
and diversity across elevation. On all three shores, richness increased from high to middle elevations, but remained similar
between middle and low elevations. Diversity followed the same trend on one shore and different trends (although also non-unimodal)
on the other two. Evenness explained the trend differences between richness and diversity. Overall, our study yielded little
support for the ESM. Reasons for richness and diversity not decreasing at low elevations may be related to influences of mostly
subtidal species, Helgoland’s intertidal range, or sampling resolution. Our study also suggests that the ESM must be developed
further to differentiate between richness and diversity. We offer recommendations to improve future ESM research using intertidal
systems. 相似文献
62.
Sikorski J Teshima H Nolan M Lucas S Hammon N Deshpande S Cheng JF Pitluck S Liolios K Pagani I Ivanova N Huntemann M Mavromatis K Ovchinikova G Pati A Tapia R Han C Goodwin L Chen A Palaniappan K Land M Hauser L Ngatchou-Djao OD Rohde M Pukall R Spring S Abt B Göker M Detter JC Woyke T Bristow J Markowitz V Hugenholtz P Eisen JA Kyrpides NC Klenk HP Lapidus A 《Standards in genomic sciences》2011,4(3):331-341
Mahella australiensis Bonilla Salinas et al. 2004 is the type species of the genus Mahella, which belongs to the family Thermoanaerobacteraceae. The species is of interest because it differs from other known anaerobic spore-forming bacteria in its G+C content, and in certain phenotypic traits, such as carbon source utilization and relationship to temperature. Moreover, it has been discussed that this species might be an indigenous member of petroleum and oil reservoirs. This is the first completed genome sequence of a member of the genus Mahella and the ninth completed type strain genome sequence from the family Thermoanaerobacteraceae. The 3,135,972 bp long genome with its 2,974 protein-coding and 59 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project. 相似文献
63.
Huntemann M Lu M Nolan M Lapidus A Lucas S Hammon N Deshpande S Cheng JF Tapia R Han C Goodwin L Pitluck S Liolios K Pagani I Ivanova N Ovchinikova G Pati A Chen A Palaniappan K Land M Hauser L Jeffries CD Detter JC Brambilla EM Rohde M Spring S Göker M Woyke T Bristow J Eisen JA Markowitz V Hugenholtz P Kyrpides NC Klenk HP Mavromatis K 《Standards in genomic sciences》2011,4(3):303-311
Hippea maritima (Miroshnichenko et al. 1999) is the type species of the genus Hippea, which belongs to the family Desulfurellaceae within the class Deltaproteobacteria. The anaerobic, moderately thermophilic marine sulfur-reducer was first isolated from shallow-water hot vents in Matipur Harbor, Papua New Guinea. H. maritima was of interest for genome sequencing because of its isolated phylogenetic location, as a distant next neighbor of the genus Desulfurella. Strain MH(2) (T) is the first type strain from the order Desulfurellales with a completely sequenced genome. The 1,694,430 bp long linear genome with its 1,723 protein-coding and 57 RNA genes consists of one circular chromosome and is a part of the Genomic Encyclopedia of Bacteria and Archaea project. 相似文献
64.
Sedegah M Tamminga C McGrath S House B Ganeshan H Lejano J Abot E Banania GJ Sayo R Farooq F Belmonte M Manohar N Richie NO Wood C Long CA Regis D Williams FT Shi M Chuang I Spring M Epstein JE Mendoza-Silveiras J Limbach K Patterson NB Bruder JT Doolan DL King CR Soisson L Diggs C Carucci D Dutta S Hollingdale MR Ockenhouse CF Richie TL 《PloS one》2011,6(10):e24586
65.
Pauly C Spring P Gahan D O'Doherty JV 《Animal : an international journal of animal bioscience》2011,5(3):378-386
A 2 × 2 factorial experiment was conducted to investigate the effects of cereal type (barley v. oat) and exogenous enzyme supplementation (with or without) on intestinal fermentation, and on indole and skatole levels in the intestinal content and the adipose tissue in finisher boars. The experimental treatments were as follows: (i) barley-based diet, (ii) barley-based diet with enzyme supplement, (iii) oat-based diet and (iv) oat-based diet with enzyme supplement. The enzyme supplement contained endo-1,3(4)-β-glucanase (EC 3.2.1.6) and endo-1,4-β-xylanase (EC 3.2.1.8). The animals were fed ad libitum for 45 days from 76.0 to 113.6 kg live weight. Feeding barley-based diets led to higher (P < 0.05) total volatile fatty acids concentrations in the large intestine. Proportions of propionic- and butyric-acids were higher and that of acetic acid lower in digesta from barley-based in comparison to oat-based diets (P < 0.001). Consequently, pH in the large intestine was higher after feeding oat-based in comparison to barley-based diets. Animals fed unsupplemented oat-based diet had higher (P < 0.01) indole concentrations in the digesta from the proximal colon than those fed barley-based diets. Feeding oat-based diets led to lower (P < 0.01) skatole and higher (P < 0.001) indole concentrations in the digesta from the terminal colon than barley-based diets. skatole concentrations in the adipose tissue did not differ (P > 0.05) between the experimental treatments. Pigs offered the barley-based diets had lower (P < 0.001) indole concentrations in the adipose tissue compared with those fed the oat-based diet. In conclusion, barley-based diets were more efficient than oat-based diets in limiting concentrations of indole in the adipose tissue. 相似文献
66.
Molecular Ecology Resources Primer Development Consortium Austin JD Bertin A Bórquez JP Cárdenas L Cardoza TB Chapman F De Sousa AC De Souza AP Douglas KC Ellwood SR Ferriol M Garmendia A Gouin N Hargrove J Jasti M Keränen I Knott KE Konec M Kuitunen K Lima MP Linde CC Merle H Oliva ME Pérez M Saarinen E Samollow PB Scarpassa VM Segura I Smith L Trontelj P Valdivia IM Wallwork H Wellenreuther M 《Molecular ecology resources》2011,11(4):757-758
This article documents the addition of 111 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Acipenser oxyrinchus desotoi, Anopheles nuneztovari sensu lato, Asellus aquaticus, Calopteryx splendens, Calopteryx virgo, Centaurea aspera, Centaurea seridis, Chilina dombeyana, Proctoeces cf. lintoni and Pyrenophora teres f. teres. 相似文献
67.
68.
Inhibition of dihydropyridine-sensitive calcium channels by the plant alkaloid ryanodine 总被引:4,自引:0,他引:4
At micromolar concentrations, ryanodine interacts with the dihydropyridine receptor of rabbit skeletal muscle transverse tubules. Ryanodine displaces specifically bound [3H]PN200-110 with an apparent inhibition constant of approx. 95 microM and inhibits dihydropyridine-sensitive calcium channels in the same preparation with an IC50 of approx. 45 microM. These concentrations of ryanodine are approximately three orders of magnitude higher than those required to saturate binding of the alkaloid to the ryanodine receptor of sarcoplasmic reticulum and to open the calcium release channel of sarcoplasmic reticulum (i.e. 20 nM (1988) J. Gen. Physiol. 92, 1-26). Thus at sufficiently high dose, ryanodine may affect SR as well as plasma membrane Ca permeabilities. 相似文献
69.
In Escherichia coli the codons CGG, AGG, UGG or GGG (NGG codons) but not GGN or GNG (where N is non-G) are associated with low expression of a reporter gene, if located at positions +2 to +5. Induction of a lacZ reporter gene with any one of the NGG codons at position +2 to +5 does not influence growth of a normal strain, but growth of a strain with a defective peptidyl-tRNA hydrolase (Pth) enzyme is inhibited. The same codons, if placed at position +7, did not give this effect. Other codons, such as CGU and AGA, at location +2 to +5, did not give any growth inhibition of either the wild-type or the mutant strain. The inhibitory effect on the pth mutant strain by NGG codons at location +5 was suppressed by overexpression of the Pth enzyme from a plasmid. However, the overexpression of cognate tRNAs for AGG or GGG did not rescue from the growth inhibition associated with these codons early in the induced model gene. The data suggest that the NGG codons trigger peptidyl-tRNA drop-off if located at early coding positions in mRNA, thereby strongly reducing gene expression. This does not happen if these codons are located further down in the mRNA at position +7, or later. 相似文献
70.
R.?Fernández-Pacheco M.?R.?IbarraEmail author J.?G.?Valdivia C.?Marquina D.?Serrate M.?S.?Romero M.?Gutiérrez J.?Arbiol 《NanoBioTechnology》2005,1(3):300-303
Bioferrofluids obtained from carbon coated iron nanoparticles are promising candidates for magnetic drug delivery. The carbon
cages render the particles biocompatible, and provide a good support for drug adsorption. We propose a method in which gold
plated permanent magnets are implanted directly in the affected organ, close to the tumour, by endoscopic techniques. The
bioferrofluid charged with the chemotherapeutic agent is injected and the particles attracted to the magnet, then desorption
of the drug takes place at the tumoral region. This method seems to be more promising, costless and effective than that based
on the application of external magnetic fields. Preliminary results of drug adsorption and a preclinical experimental animal
model are described. 相似文献