全文获取类型
收费全文 | 5185篇 |
免费 | 623篇 |
国内免费 | 1篇 |
出版年
2021年 | 51篇 |
2018年 | 62篇 |
2017年 | 51篇 |
2016年 | 92篇 |
2015年 | 156篇 |
2014年 | 157篇 |
2013年 | 202篇 |
2012年 | 223篇 |
2011年 | 237篇 |
2010年 | 149篇 |
2009年 | 129篇 |
2008年 | 185篇 |
2007年 | 163篇 |
2006年 | 183篇 |
2005年 | 155篇 |
2004年 | 151篇 |
2003年 | 124篇 |
2002年 | 184篇 |
2001年 | 170篇 |
2000年 | 159篇 |
1999年 | 148篇 |
1998年 | 68篇 |
1997年 | 45篇 |
1996年 | 62篇 |
1995年 | 82篇 |
1994年 | 59篇 |
1993年 | 72篇 |
1992年 | 134篇 |
1991年 | 117篇 |
1990年 | 137篇 |
1989年 | 98篇 |
1988年 | 119篇 |
1987年 | 109篇 |
1986年 | 91篇 |
1985年 | 100篇 |
1984年 | 81篇 |
1983年 | 74篇 |
1982年 | 76篇 |
1981年 | 73篇 |
1980年 | 67篇 |
1979年 | 95篇 |
1978年 | 91篇 |
1977年 | 67篇 |
1976年 | 64篇 |
1975年 | 56篇 |
1973年 | 49篇 |
1972年 | 58篇 |
1971年 | 50篇 |
1968年 | 40篇 |
1967年 | 43篇 |
排序方式: 共有5809条查询结果,搜索用时 859 毫秒
931.
932.
933.
934.
935.
Alberto Martín Patricia Miloslavich Yusbelly Díaz Ileana Ortega Eduardo Klein Jesús Troncoso Cristian Aldea Ana K. Carbonini 《Polar Biology》2016,39(2):207-220
Antarctic benthos has been a main target in Antarctic research, but very few quantitative studies have been carried out in the littoral zone, which may be seasonally covered by macroalgae. In this work, we studied (1) cover and biomass of the macroalgae Iridaea cordata and Adenocystis utricularis, and (2) composition of macrobenthic assemblage associated with these macroalgal species at three locations at King George Island: Mareograph Beach (1 M), Tank’s Bay (2R) and Ardley Bay (3R). Iridaea cordata was collected by completely detaching the algae from the substrate, while A. utricularis was scraped. Adenocystis utricularis covered more than 80 % of the substrate at all locations, while coverage of Iridaea cordata was below 53 % or absent (3R). Fresh biomass of I. cordata was 0.8–61.4 g/individual and 4.7–93.0 g/100 cm2 for A. utricularis. The assemblage associated with both macroalgae differed significantly between sites. The studied fauna was composed mainly of amphipods, gastropods and bivalves. Species diversity was higher in the community associated with A. utricularis. A total of ~27 ind/g DW were found associated with I. cordata, while ~112 ind/g DW were found associated with A. utricularis. The most abundant groups associated with I. cordata were amphipods at 1 M (57 %) and gastropods at 2R (46 %). Both groups were responsible for the dissimilarity between localities (62.50 %). The most abundant groups associated with A. utricularis were the gastropods at all localities reaching up to 82 % at 1 M. This study provides a first baseline on the diversity and abundance of benthic assemblages associated with intertidal macroalgae in the southwest of King George Island. 相似文献
936.
937.
Jun-Gu Kang Sungjin Ko Heung-Chul Kim Sung-Tae Chong Terry A. Klein Jeong-Byoung Chae Yong-Sun Jo Kyoung-Seong Choi Do-Hyeon Yu Bae-Keun Park Jinho Park Joon-Seok Chae 《The Korean journal of parasitology》2016,54(1):87-91
Deer serve as reservoirs of tick-borne pathogens that impact on medical and veterinary health worldwide. In the Republic of Korea, the population of Korean water deer (KWD, Hydropotes inermis argyropus) has greatly increased from 1982 to 2011, in part, as a result of reforestation programs established following the Korean War when much of the land was barren of trees. Eighty seven Haemaphysalis flava, 228 Haemaphysalis longicornis, 8 Ixodes nipponensis, and 40 Ixodes persulcatus (21 larvae, 114 nymphs, and 228 adults) were collected from 27 out of 70 KWD. A total of 89/363 ticks (266 pools, 24.5% minimum infection rate) and 5 (1.4%) fed ticks were positive for Anaplasma phagocytophilum using nested PCR targeting the 16S rRNA and groEL genes, respectively. The 16S rRNA gene fragment sequences of 88/89 (98.9%) of positive samples for A. phagocytophilum corresponded to previously described gene sequences from KWD spleen tissues. The 16S rRNA gene fragment sequences of 20/363 (5.5%) of the ticks were positive for A. bovis and were identical to previously reported sequences. Using the ITS specific nested PCR, 11/363 (3.0%) of the ticks were positive for Bartonella spp. This is the first report of Anaplasma and Bartonella spp. detected in ticks collected from KWD, suggesting that ticks are vectors of Anaplasma and Bartonella spp. between reservoir hosts in natural surroundings. 相似文献
938.
Antimicrobial susceptibility monitoring of dermatological bacterial pathogens isolated from diseased dogs and cats across Europe (ComPath results)
下载免费PDF全文
![点击此处可从《Journal of applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
C. Ludwig A. de Jong H. Moyaert F. El Garch R. Janes U. Klein I. Morrissey J. Thiry M. Youala 《Journal of applied microbiology》2016,121(5):1254-1267
939.
Exploration of the structural features defining the conduction properties of a synthetic ion channel. 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Biophysical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
G R Dieckmann J D Lear Q Zhong M L Klein W F DeGrado K A Sharp 《Biophysical journal》1999,76(2):618-630
The finite-difference Poisson-Boltzmann methodology was applied to a series of parallel, alpha-helical bundle models of the designed ion channel peptide Ac-(LSSLLSL)3-CONH2. This method is able to fully describe the current-voltage curves for this channel and quantitatively explains their cation selectivity and rectification. We examined a series of energy-minimized models representing different aggregation states, side-chain rotamers, and helical rotations, as well as an ensemble of structures from a molecular dynamics trajectory. Potential energies were computed for single, permeating K+ and Cl- ions at a series of positions along a central pathway through the models. A variable-electric-field Nernst-Planck electrodiffusion model was used, with two adjustable parameters representing the diffusion coefficients of K+ and Cl- to scale the individual ion current magnitudes. The ability of a given DelPhi potential profile to fit the experimental data depended strongly on the magnitude of the desolvation of the permeating ion. Below a pore radius of 3.8 A, the predicted profiles showed large energy barriers, and the experimental data could be fit only with unrealistically high values for the K+ and Cl- diffusion coefficients. For pore radii above 3.8 A, the desolvation energies were 2kT or less. The electrostatic calculations were sensitive to positioning of the Ser side chains, with the best fits associated with maximum exposure of the Ser side-chain hydroxyls to the pore. The backbone component was shown to be the major source of asymmetry in the DelPhi potential profiles. Only two of the energy-minimized structures were able to explain the experimental data, whereas an average of the dynamics structures gave excellent agreement with experimental results. Thus this method provides a promising approach to prediction of current-voltage curves from three-dimensional structures of ion channel proteins. 相似文献
940.
The receptor protein NOTCH and its ligands SERRATE and DELTA are involved in many developmental processes in invertebrates and vertebrates alike. Here we show that the expression of the Serrate and Delta genes patterns the segments of the leg in Drosophila by a combination of their signalling activities. Coincident stripes of Serrate and Delta expressing cells activate Enhancer of split expression in adjacent cells through Notch signalling. These cells form a patterning boundary from which a putative secondary signal leads to the development of leg joints. Elsewhere in the tarsal segments, signalling by DELTA and NOTCH is necessary for the development of non-joint parts of the leg. We propose that these two effects result from different thresholds of NOTCH activation, which are translated into different downstream gene expression effects. We propose a general mechanism for creation of boundaries by Notch signalling. 相似文献