全文获取类型
收费全文 | 890篇 |
免费 | 72篇 |
国内免费 | 2篇 |
出版年
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2016年 | 17篇 |
2015年 | 20篇 |
2014年 | 30篇 |
2013年 | 40篇 |
2012年 | 52篇 |
2011年 | 35篇 |
2010年 | 20篇 |
2009年 | 19篇 |
2008年 | 35篇 |
2007年 | 34篇 |
2006年 | 32篇 |
2005年 | 31篇 |
2004年 | 24篇 |
2003年 | 30篇 |
2002年 | 20篇 |
2001年 | 22篇 |
2000年 | 33篇 |
1999年 | 22篇 |
1998年 | 20篇 |
1997年 | 17篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 19篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1979年 | 10篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1972年 | 10篇 |
1971年 | 9篇 |
1970年 | 8篇 |
1969年 | 9篇 |
1968年 | 9篇 |
排序方式: 共有964条查询结果,搜索用时 31 毫秒
121.
McGough R Paterson K Bradshaw EJ Bryant AL Clark RA 《Journal of strength and conditioning research / National Strength & Conditioning Association》2012,26(1):47-52
Weight-bearing asymmetry (WBA) may be detrimental to performance and could increase the risk of injury; however, detecting and reducing it is difficult in a field setting. This study assessed whether a portable and simple-to-use system designed with multiple Nintendo Wii Balance Boards (NWBBs) and customized software can be used to evaluate and improve WBA. Fifteen elite Australian Rules Footballers and 32 age-matched, untrained participants were tested for measures of WBA while squatting. The NWBB and customized software provided real-time visual feedback of WBA during half of the trials. Outcome measures included the mean mass difference (MMD) between limbs, interlimb symmetry index (SI), and percentage of time spent favoring a single limb (TFSL). Significant reductions in MMD (p = 0.028) and SI (p = 0.007) with visual feedback were observed for the entire group data. Subgroup analysis revealed significant reductions in MMD (p = 0.047) and SI (p = 0.026) with visual feedback in the untrained sample; however, the reductions in the trained sample were nonsignificant. The trained group showed significantly less WBA for TFSL under both visual conditions (no feedback: p = 0.015, feedback: p = 0.017). Correlation analysis revealed that participants with high levels of WBA had the greatest response to feedback (p < 0.001, ρ = 0.557). In conclusion, WBA exists in healthy untrained adults, and these asymmetries can be reduced using real-time visual feedback provided by an NWBB-based system. Healthy, well-trained professional athletes do not possess the same magnitude of WBA. Inexpensive, portable, and widely available gaming technology may be used to evaluate and improve WBA in clinical and sporting settings. 相似文献
122.
Robin A. Ohm Nicolas Feau Bernard Henrissat Conrad L. Schoch Benjamin A. Horwitz Kerrie W. Barry Bradford J. Condon Alex C. Copeland Braham Dhillon Fabian Glaser Cedar N. Hesse Idit Kosti Kurt LaButti Erika A. Lindquist Susan Lucas Asaf A. Salamov Rosie E. Bradshaw Lynda Ciuffetti Richard C. Hamelin Gert H. J. Kema Christopher Lawrence James A. Scott Joseph W. Spatafora B. Gillian Turgeon Pierre J. G. M. de Wit Shaobin Zhong Stephen B. Goodwin Igor V. Grigoriev 《PLoS pathogens》2012,8(12)
The class Dothideomycetes is one of the largest groups of fungi with a high level of ecological diversity including many plant pathogens infecting a broad range of hosts. Here, we compare genome features of 18 members of this class, including 6 necrotrophs, 9 (hemi)biotrophs and 3 saprotrophs, to analyze genome structure, evolution, and the diverse strategies of pathogenesis. The Dothideomycetes most likely evolved from a common ancestor more than 280 million years ago. The 18 genome sequences differ dramatically in size due to variation in repetitive content, but show much less variation in number of (core) genes. Gene order appears to have been rearranged mostly within chromosomal boundaries by multiple inversions, in extant genomes frequently demarcated by adjacent simple repeats. Several Dothideomycetes contain one or more gene-poor, transposable element (TE)-rich putatively dispensable chromosomes of unknown function. The 18 Dothideomycetes offer an extensive catalogue of genes involved in cellulose degradation, proteolysis, secondary metabolism, and cysteine-rich small secreted proteins. Ancestors of the two major orders of plant pathogens in the Dothideomycetes, the Capnodiales and Pleosporales, may have had different modes of pathogenesis, with the former having fewer of these genes than the latter. Many of these genes are enriched in proximity to transposable elements, suggesting faster evolution because of the effects of repeat induced point (RIP) mutations. A syntenic block of genes, including oxidoreductases, is conserved in most Dothideomycetes and upregulated during infection in L. maculans, suggesting a possible function in response to oxidative stress. 相似文献
123.
Clive R. McMahon Iain C. Field Corey J.A. Bradshaw Gary C. White Mark A. Hindell 《Journal of experimental marine biology and ecology》2008,360(2):71-77
Understanding the cryptic lives of wide–ranging wild animals such as seals can be challenging, but with the advent of miniaturised telemetry and data–logging devices this is now possible and relatively straightforward. However, because marine animals have streamline bodies to reduce drag in their aquatic habitats, attaching external devices to their back or head may affect swimming performance, prey capture efficiency and ultimately, fitness. Given this, and allied welfare concerns, we assessed the short- and long-term consequences of external devices attached to southern elephant seal juveniles and adults under varying environmental conditions. We also assessed the effects of multiple deployments on individuals. There was no evidence for short-term differences in at-sea mass gain (measured as mass on arrival from a foraging trip) or long-term survival rate. The number of times that a seal carried a tracking device (ranging from 1 to 8 times) did not affect mass or estimated survival. Further, there were no tracking device effects in years of contrasting environmental conditions measured as ENSO anomalies. Consequently, we conclude that the current tracking devices available to researchers are valuable conservation tools that do not adversely affect the performance of a large marine mammal in terms of mass gain or survival probability over short (seasonal) or long (years) temporal scales. 相似文献
124.
Evolved patterns of resource expenditure for reproduction have resulted in a life history continuum across species. A strictly
capital-breeding strategy relies extensively on stored energy for reproduction, whereas income breeding uses energy acquired
throughout the reproductive period. However, facultative income breeding has been shown in some classically capital-breeding
animals, and was originally thought to provide a nutritional refuge for smaller females incapable of securing sufficient reserves
during pre-partum foraging. We examined milk composition and milk output for the Weddell seal to determine to what degree
lactation was aided by food intake, and what factors contributed to its manifestation. Milk composition was independent of
maternal post-partum mass and condition, but did change over lactation. Changes were most likely in response to energetic
and nutritional demands of the pup at different stages of development. During early lactation, females fasted and devoted
54.9% of total energy loss to milk production. Later in lactation 30.5% more energy was devoted to milk production and evidence
suggested that larger females fed more during lactation than smaller females. It appears that Weddell seals may exhibit a
flexible strategy to adjust reproductive investment to local resource levels by taking advantage of periods when prey are
occasionally abundant, although it is restricted to larger females possessing the physiological capacity to dive for longer
and exploit different resources during lactation. This supports the assumption that although body mass and phylogenetic history
explain most of the variation in lactation patterns (20–69%), the remaining variation has likely resulted from physiological
adaptations to local environmental conditions. Our study confirms that Weddell seals use a mixed capital–income breeding strategy,
and that considerable intraspecific variation exists. Questions remain as to the amount of energy gain derived from the income
strategy, and the consequences for pup condition and survival.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
125.
QTL mapping of yield, agronomic and quality traits in tetraploid potato (Solanum tuberosum subsp. tuberosum) 总被引:2,自引:0,他引:2
Bradshaw JE Hackett CA Pande B Waugh R Bryan GJ 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,116(2):193-211
Interval mapping of quantitative trait loci (QTL) for 16 yield, agronomic and quality traits in potato was performed on a
tetraploid full-sib family comprising 227 clones from a cross between processing clone 12601ab1 and table cultivar Stirling.
Thirty-eight AFLP primer combinations and six SSRs provided 514 informative markers which formed a molecular marker map comprising
12 linkage groups (LGs) in 12601ab1 (nine with four homologous chromosomes) which were aligned with 12 in Stirling (11 with
four homologous chromosomes), with four partial groups remaining in 12601ab1. Two LGs were identified unequivocally as chromosomes
IV and V and eight others were tentatively assigned with chromosomes VII and X unidentified. All of the traits scored had
moderately high heritabilities with 54–92% of the variation in clone means over 3 years and two replicates being due to genetic
differences. A total of 39 QTLs were identified. A QTL for maturity was identified on chromosome V which explained 56% of
the phenotypic variance, whereas the other QTLs individually explained between 5.4 and 16.5%. However, six QTLs were detected
for after-cooking blackening and four for each of regularity of tuber shape, fry colour both after storage at 4 and 10°C and
sprouting. Just two QTLs were found for each of yield, the two ‘overall’ scores, crop emergence, tuber size and common scab
and just one QTL was detected for each of dry matter content, keeping quality, growth cracks and internal condition. The implications
for practical potato breeding and for practical linkage and QTL analysis in autotetraploids are discussed. 相似文献
126.
Sodhi NS Bickford D Diesmos AC Lee TM Koh LP Brook BW Sekercioglu CH Bradshaw CJ 《PloS one》2008,3(2):e1636
Habitat loss, climate change, over-exploitation, disease and other factors have been hypothesised in the global decline of amphibian biodiversity. However, the relative importance of and synergies among different drivers are still poorly understood. We present the largest global analysis of roughly 45% of known amphibians (2,583 species) to quantify the influences of life history, climate, human density and habitat loss on declines and extinction risk. Multi-model Bayesian inference reveals that large amphibian species with small geographic range and pronounced seasonality in temperature and precipitation are most likely to be Red-Listed by IUCN. Elevated habitat loss and human densities are also correlated with high threat risk. Range size, habitat loss and more extreme seasonality in precipitation contributed to decline risk in the 2,454 species that declined between 1980 and 2004, compared to species that were stable (n = 1,545) or had increased (n = 28). These empirical results show that amphibian species with restricted ranges should be urgently targeted for conservation. 相似文献
127.
In Iowa, the management of insect pests in soybean, Glycine max (L.) Merr., has been complicated by the arrival of the invasive species soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), and occasional outbreaks of bean leaf beetle, Cerotoma trifurcata (F?rster) (Coleoptera: Chrysomelidae), populations leading to economic losses. Several insecticide programs designed to reduce abundance of the overwintered and first generation C. trifurcata and the incidence of bean pod mottle virus were evaluated over 3 yr (2004-2006) for their impacts on A. glycines populations, at three locations in Iowa (Floyd, Lucas, and Story counties). There was no significant overlap of either overwintered (early May) or the first (early July) generations of C. trifurcata with A. glycines, because aphids were first detected in June and they did not reach economically damaging levels until August, if at all. During this study, insecticides targeting the overwintered population or the first generation of C. trifurcata provided a limited impact on A. glycines populations compared with untreated controls, and they did not prevent economic populations from occurring. Furthermore, the highest populations of A. glycines were frequently observed when a low rate of lambda-cyhalothrin (178 ml/ha) was applied targeting the overwintered population of C. trifurcata. Soybean yields were not protected by any of the insecticide treatments. Our results indicate that the use of either early season foliar or seed-applied insecticides for C. trifurcata management is of limited value for A. glycines management. 相似文献
128.
129.
Microbiological Evaluation of a Range of Disinfectant Products To Control Mixed-Species Biofilm Contamination in a Laboratory Model of a Dental Unit Water System 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dental unit water system (DUWS) tubing harbors complex multispecies biofilms that are responsible for high microbial levels at the distal outlet. The aim of this study was to use an established biofilm laboratory model to simulate biofouling of DUWS to evaluate practical, cost-effective, and evidence-based methods of microbial decontamination. Reproducible biofilms were developed in the model over 14 days; decontamination was assessed using total viable counts (TVC) and microscopic-image analysis techniques to view the inner surface of tubing. Flushing did not reduce the biofilm coverage or TVC. Combizyme and ozone did not completely eliminate the viable bacteria (70 and 65% reduction in biofilm TVC, respectively), nor did they remove the biofilm (45 and 57% reduction in biofilm coverage, respectively). Chlorhexidine and Bio2000 (active agent: ethanol and chlorhexidine), Tegodor and Gigasept Rapid (aldehyde based), and Grotanol (hydroxide based) completely eliminated the TVC but did not completely remove biofilm (31, 53 33, 34, and 64.9% reduction of biofilm coverage, respectively). Other products including Grotanol Flussig (phenol based), Betadine (povidone-iodine based), Alpron (chlorite based), and the hydroxide-containing products Sporklenz, Sterilex Ultra, Dialox, Sterilox, Sanosil, Oxigenal, and Grotanat Bohrerbad resulted in a 100% reduction in the biofilm TVC and a >95% reduction in biofilm coverage. The study demonstrated that while many disinfectants achieve a sufficient reduction in TVC they may not necessarily remove unwanted biofilm from the tubing surfaces as tested in this laboratory-controlled biofilm model. 相似文献
130.
Xavier Bonnet David Pearson Mitchell Ladyman Olivier Lourdais Don Bradshaw 《Austral ecology》2002,27(4):442-450
Abstract Animals resident on small islands provide excellent opportunities to carry out detailed mark–recapture studies. Populations are closed and ecosystems are often simpler than those of mainland sites. These factors enable the study of cryptic species that have otherwise been neglected. Snakes are notable for their secretive nature and, as a result, few natural populations have been accurately described through long‐term mark–recapture monitoring. A population of tiger snakes (Notechis scutatus) was studied on Carnac Island, a small limestone island (16 ha) off the coast of Western Australia. Population estimates show that snake density is very high, with more than 20 adult snakes per ha. This equates to a biomass of more than 100 kg of a top predator concentrated in a very small area. Such a high predator density can be explained because adult snakes feed mainly on chicks of nesting birds that breed in large colonies on Carnac but forage elsewhere. Substantial annual growth rates in body size in most individuals suggest that food availability is high on Carnac. Growth rates decreased more sharply in adult females than in males, whereas annual changes in body mass were similar in both sexes, probably because of the high energetic costs of reproduction experienced by females. Surprisingly, the sex ratio was highly biased, with males largely outnumbering females. 相似文献