全文获取类型
收费全文 | 402篇 |
免费 | 60篇 |
出版年
2024年 | 3篇 |
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 34篇 |
2012年 | 16篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 16篇 |
2008年 | 22篇 |
2007年 | 16篇 |
2006年 | 18篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 22篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 7篇 |
1971年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有462条查询结果,搜索用时 15 毫秒
31.
L. Pérez-Pardal L. J. Royo I. Álvarez F. A. Ponce de León I. Fernández R. Casais F. Goyache 《Animal genetics》2009,40(4):560-564
Here we tested the segregation and paternal compatibility of markers INRA124 and INRA126 on female DNA in 10 different cattle families, in order to clarify the usefulness of these microsatellites for the study of male-mediated population processes in cattle. Their performance was compared with that of four microsatellites located in the PAR-BTAY ( UMN0108 , UMN0803 , UMN0929 and UMN0905 ) and another one male-specific microsatellite ( INRA189 ). INRA124 and INRA126 amplified the same sized fragment in both sexes. Same size alleles were sequenced and the high homology found allowed us to rule out non-specific female amplification. INRA124 showed full parental compatibility, whilst the locus INRA126 showed 55% parental incompatibility. Based on these observations, it is recommended that markers INRA124 and INRA126 should not be used in studies to characterize male-mediated genetic events in cattle. 相似文献
32.
Jodi L. Vanden Eng Adeline Chan Ana Paula Abílio Adam Wolkon Gabriel Ponce de Leon John Gimnig Juliette Morgan 《PloS one》2015,10(6)
Background
The durability of Long Lasting Insecticidal Nets (LLINs) in field conditions is of great importance for malaria prevention and control efforts; however, the physical integrity of the net fabric is not well understood making it challenging to determine overall effectiveness of nets as they age. The 2011 World Health Organization Pesticide Evaluation Scheme (WHOPES) guidelines provide a simple, standardized method using a proportional hole index (PHI) for assessing net damage with the intent to provide national malaria control programs with guidelines to assess the useful life of LLINS and estimate the rate of replacement.Methods
We evaluated the utility of the PHI measure using 409 LLINs collected over three years in Nampula Province, Mozambique following a mass distribution campaign in 2008. For each LLIN the diameter and distance from the bottom of the net were recorded for every hole. Holes were classified into four size categories and a PHI was calculated following WHOPES guidelines. We investigate how the size, shape, and location of holes influence the PHI. The areas of the WHOPES defined categories were compared to circular and elliptical areas based on approximate shape and actual measured axes of each hole and the PHI was compared to cumulative damaged surface area of the LLIN.Results
The damaged area of small, medium, large, and extra-large holes was overestimated using the WHOPES categories compared to elliptical areas using the actual measured axes. Similar results were found when comparing to circular areas except for extra-large holes which were underestimated. (Wilcoxon signed rank test of differences p< 0.0001 for all sizes). Approximating holes as circular overestimated hole surface area by 1.5 to 2 times or more. There was a significant difference in the mean number of holes < 0.5 cm by brand and there were more holes of all sizes on the bottom of nets than the top. For a range of hypothetical PHI thresholds used to designate a “failed LLIN”, roughly 75 to 80% of failed LLINs were detected by considering large and extra-large holes alone, but sensitivity varied by brand.Conclusions
Future studies may refine the PHI to better approximate overall damaged surface area. Furthermore, research is needed to identify whether or not appropriate PHI thresholds can be used to deem a net no longer protective. Once a cutoff is selected, simpler methods of determining the effective lifespan of LLINs can help guide replacement strategies for malaria control programs. 相似文献33.
Herman Pontzer Campbell Rolian G. Philip Rightmire Tea Jashashvili Marcia S. Ponce de León David Lordkipanidze Christoph P.E. Zollikofer 《Journal of human evolution》2010,58(6):492-504
The Dmanisi hominins inhabited a northern temperate habitat in the southern Caucasus, approximately 1.8 million years ago. This is the oldest population of hominins known outside of Africa. Understanding the set of anatomical and behavioral traits that equipped this population to exploit their seasonal habitat successfully may shed light on the selection pressures shaping early members of the genus Homo and the ecological strategies that permitted the expansion of their range outside of the African subtropics. The abundant stone tools at the site, as well as taphonomic evidence for butchery, suggest that the Dmanisi hominins were active hunters or scavengers. In this study, we examine the locomotor mechanics of the Dmanisi hind limb to test the hypothesis that the inclusion of meat in the diet is associated with an increase in walking and running economy and endurance. Using comparative data from modern humans, chimpanzees, and gorillas, as well as other fossil hominins, we show that the Dmanisi hind limb was functionally similar to modern humans, with a longitudinal plantar arch, increased limb length, and human-like ankle morphology. Other aspects of the foot, specifically metatarsal morphology and tibial torsion, are less derived and similar to earlier hominins. These results are consistent with hypotheses linking hunting and scavenging to improved walking and running performance in early Homo. Primitive retentions in the Dmanisi foot suggest that locomotor evolution continued through the early Pleistocene. 相似文献
34.
35.
Priority threat management of invasive animals to protect biodiversity under climate change 下载免费PDF全文
Jennifer Firn Ramona Maggini Iadine Chadès Sam Nicol Belinda Walters Andy Reeson Tara G. Martin Hugh P. Possingham Jean‐Baptiste Pichancourt Rocio Ponce‐Reyes Josie Carwardine 《Global Change Biology》2015,21(11):3917-3930
Climate change is a major threat to global biodiversity, and its impacts can act synergistically to heighten the severity of other threats. Most research on projecting species range shifts under climate change has not been translated to informing priority management strategies on the ground. We develop a prioritization framework to assess strategies for managing threats to biodiversity under climate change and apply it to the management of invasive animal species across one‐sixth of the Australian continent, the Lake Eyre Basin. We collected information from key stakeholders and experts on the impacts of invasive animals on 148 of the region's most threatened species and 11 potential strategies. Assisted by models of current distributions of threatened species and their projected distributions, experts estimated the cost, feasibility, and potential benefits of each strategy for improving the persistence of threatened species with and without climate change. We discover that the relative cost‐effectiveness of invasive animal control strategies is robust to climate change, with the management of feral pigs being the highest priority for conserving threatened species overall. Complementary sets of strategies to protect as many threatened species as possible under limited budgets change when climate change is considered, with additional strategies required to avoid impending extinctions from the region. Overall, we find that the ranking of strategies by cost‐effectiveness was relatively unaffected by including climate change into decision‐making, even though the benefits of the strategies were lower. Future climate conditions and impacts on range shifts become most important to consider when designing comprehensive management plans for the control of invasive animals under limited budgets to maximize the number of threatened species that can be protected. 相似文献
36.
Mollá-Morales A Sarmiento-Mañús R Robles P Quesada V Pérez-Pérez JM González-Bayón R Hannah MA Willmitzer L Ponce MR Micol JL 《The Plant journal : for cell and molecular biology》2011,65(3):335-345
Arabidopsis thaliana reticulate mutants exhibit differential pigmentation of the veinal and interveinal leaf regions, a visible phenotype that often indicates impaired mesophyll development. We performed a metabolomic analysis of one ven6 (venosa6) and three ven3 reticulate mutants that revealed altered levels of arginine precursors, namely increased ornithine and reduced citrulline levels. In addition, the mutants were more sensitive than the wild-type to exogenous ornithine, and leaf reticulation and mesophyll defects of these mutants were completely rescued by exogenous citrulline. Taken together, these results indicate that ven3 and ven6 mutants experience a blockage of the conversion of ornithine into citrulline in the arginine pathway. Consistent with the participation of VEN3 and VEN6 in the same pathway, the morphological phenotype of ven3 ven6 double mutants was synergistic. Map-based cloning showed that the VEN3 and VEN6 genes encode subunits of Arabidopsis carbamoyl phosphate synthetase (CPS), which is assumed to be required for the conversion of ornithine into citrulline in arginine biosynthesis. Heterologous expression of the Arabidopsis VEN3 and VEN6 genes in a CPS-deficient Escherichia coli strain fully restored bacterial growth in minimal medium, demonstrating the enzymatic activity of the VEN3 and VEN6 proteins, and indicating a conserved role for CPS in these distinct and distant species. Detailed study of the reticulate leaf phenotype in the ven3 and ven6 mutants revealed that mesophyll development is highly sensitive to impaired arginine biosynthesis. 相似文献
37.
38.
39.
Arbuscular mycorrhizal colonization of tomato by Gigaspora and Glomus species in the presence of root flavonoids 总被引:2,自引:0,他引:2
Scervino JM Ponce MA Erra-Bassells R Vierheilig H Ocampo JA Godeas A 《Journal of plant physiology》2005,162(6):625-633
The effect of flavonoids isolated from arbuscular mycorrhizal (AM) colonized and noncolonized clover roots on the number of entry points and percentage of root colonization of tomato (Lycopersicum esculentum L.) by Gigaspora rosea, Gi margarita, Glomus mosseae and G. intrarradices symbionts was determined. With fungi of both genera, a correlation between the number of entry points and the percentage of root colonization was found in the presence of some of the tested flavonoids. The flavonoids acacetin and rhamnetin, present in AM clover roots, inhibited the formation of AM penetration structures and the AM colonization of tomato roots, whereas the flavonoid 5,6,7,8,9-hydroxy chalcone, which could not be detected in AM clover root, inhibited both parameters. The flavonoid quercetin, which was present in AM clover roots, stimulated the penetration and root colonization of tomato by Gigaspora. However, the flavonoids 5,6,7,8-hydroxy-4'-methoxy flavone and 3,5,6,7,4'-hydroxy flavone, which was not found in AM clover root, increased the number of entry points and the AM colonization of tomato roots by Gigaspora. These results indicated that flavonoids could be imnplicated in the process of regulation of AM colonization in plant root, but its role is highly complex and depend not only on flavonoids, but also on AM fungal genus or even species. 相似文献
40.
To date, the monospecific Dendrorchis is represented by D. neivai, reported from Brazil and parasitizing Brycon lundi. Dendrorchis retrobiloba n. sp. is described from the swim bladder of Astyanax fasciatus from Ca?ada del Dragón stream in Montevideo, southern Uruguay (34 degrees 47'S, 56 degrees 14'W), and the emended diagnosis of Dendrorchis is given. The diagnosis of Dendrorchis has been modified to include the following characters: Phyllodistominae with flattened body, wider in the region posterior to acetabulum. Intestinal ceca sinuous or not. Testes branched or with superficial lobes. Ovary with deep or superficial lobes. Seminal receptacle present or absent. Vitellaria ellongate or pyriform. Uterus extends to posterior region and to portion of body anterior to acetabulum. Eggs oval, variable size, thin-shelled, without opercula. Dendrorchis retrobiloba n. sp. differs from D. neivai by having pyriform vitellaria, ovary larger than the testes and not deeply lobed, wider distribution of the uterus, smaller egg size, testes with superficial lobes, oral sucker wider than the acetabulum, shorter esophagus, 2 terminal lobes at the posterior end of the body, and much smaller body length. Despite being found in different hosts, both species of Dendrorchis parasitize the swim bladder of freshwater Characidae. 相似文献