全文获取类型
收费全文 | 3242篇 |
免费 | 245篇 |
国内免费 | 1篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 39篇 |
2021年 | 79篇 |
2020年 | 59篇 |
2019年 | 59篇 |
2018年 | 95篇 |
2017年 | 77篇 |
2016年 | 101篇 |
2015年 | 185篇 |
2014年 | 181篇 |
2013年 | 224篇 |
2012年 | 294篇 |
2011年 | 288篇 |
2010年 | 165篇 |
2009年 | 169篇 |
2008年 | 221篇 |
2007年 | 225篇 |
2006年 | 169篇 |
2005年 | 153篇 |
2004年 | 141篇 |
2003年 | 136篇 |
2002年 | 124篇 |
2001年 | 28篇 |
2000年 | 12篇 |
1999年 | 24篇 |
1998年 | 26篇 |
1997年 | 23篇 |
1996年 | 14篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1969年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有3488条查询结果,搜索用时 218 毫秒
61.
62.
Marie Collet Isabelle Amat Sandrine Sauzet Alexandra Auguste Xavier Fauvergue Laurence Mouton Emmanuel Desouhant 《Molecular ecology》2020,29(3):596-609
Sib‐mating avoidance is a pervasive behaviour that is expected to evolve in species subject to inbreeding depression. Although laboratory studies provide elegant demonstrations, small‐scaled bioassays minimize the costs of mate finding and choice, and thus may produce spurious findings. We therefore combined laboratory experiments with field observations to examine the existence of inbreeding avoidance using the parasitoid wasp Venturia canescens. In the laboratory, our approach consisted of mate‐choice experiments to assess kin discrimination in population cages with competitive interactions. A higher mating probability after sib rejections suggested that females could discriminate their sibs; however, in contrast to previous findings, sib‐mating avoidance was not observed. To compare our laboratory results to field data, we captured 241 individuals from two populations. Females laid eggs in the lab, and 226 daughters were obtained. All individuals were genotyped at 18 microsatellite loci, which allowed inference of the genotype of each female's mate and subsequently the relatedness within each mating pair. We found that the observed rate of sib‐mating did not differ from the probability that sibs encountered one another at random in the field, which is consistent with an absence of sib‐mating avoidance. In addition, we detected a weak but significant male‐biased dispersal, which could reduce encounters between sibs. We also found weak fitness costs associated with sib‐mating. As such, the sex‐biased dispersal that we found is probably sufficient to mitigate these costs. These results imply that kin discrimination has probably evolved for purposes other than mate choice, such as superparasitism avoidance. 相似文献
63.
Micaela Santos Luciano Cagnolo Tomas Roslin Emmanuel F. Ruperto María Laura Bernaschini Diego P. Vázquez 《Oikos》2021,130(1):133-142
Studying how habitat loss affects the tolerance of ecological networks to species extinction (i.e. their robustness) is key for our understanding of the influence of human activities on natural ecosystems. With networks typically occurring as local interaction networks interconnected in space (a meta-network), we may ask how the loss of specific habitat fragments affects the overall robustness of the meta-network. To address this question, for an empirical meta-network of plants, herbivores and natural enemies we simulated the removal of habitat fragments in increasing and decreasing order of area, age and connectivity for plant extinction and the secondary extinction of herbivores, natural enemies and their interactions. Meta-network robustness was characterized as the area under the curve of remnant species or interactions at the end of a fragment removal sequence. To pinpoint the effects of fragment area, age and connectivity, respectively, we compared the observed robustness for each removal scenario against that of a random sequence. The meta-network was more robust to the loss of old (i.e. long-fragmented), large, connected fragments than of young (i.e. recently fragmented), small, isolated fragments. Thus, young, small, isolated fragments may be particularly important to the conservation of species and interactions, while contrary to our expectations larger, more connected fragments contribute little to meta-network robustness. Our findings highlight the importance of young, small, isolated fragments as sources of species and interactions unique to the regional level. These effects may largely result from an unpaid extinction debt, whereby younger fragments are likely to lose species over time. Yet, there may also be more long-lasting effects from cultivated lands (e.g. water, fertilizers and restricted cattle grazing) and network complexity in small, isolated fragments. Such fragments may sustain important biological diversity in fragmented landscapes, but maintaining their conservation value may depend on adequate restoration strategies. 相似文献
64.
Faisan Joseph P. Luhan Ma. Rovilla J. Sibonga Rema C. Mateo Jonalyn P. Ferriols Victor Marco Emmanuel N. Brakel Janina Ward Georgia M. Ross Stuart Bass David Stentiford Grant D. Brodie Juliet Hurtado Anicia Q. 《Journal of applied phycology》2021,33(4):2391-2405
Journal of Applied Phycology - Farmed eucheumatoids are the top aquaculture commodity in the Philippines, contributing more than 60% of total national aquaculture production by volume. Despite... 相似文献
65.
Ahmed Hamraoui Océane Sénépart Maxime Schneider Sophie Malaquin Emmanuel Péronne Loïc Becerra Fannie Semprez Claire Legay Laurent Belliard 《Biophysical journal》2021,120(3):402-408
Because of their role of information transmitter between the spinal cord and the muscle fibers, motor neurons are subject to physical stimulation and mechanical property modifications. We report on motoneuron elasticity investigated by time-resolved pump and probe spectroscopy. A dual picosecond geometry simultaneously probing the acoustic impedance mismatch at the cell-titanium transducer interface and acoustic wave propagation inside the motoneuron is presented. Such noncontact and nondestructive microscopy, correlated to standard atomic force microscopy or a fluorescent labels approach, has been carried out on a single cell to address some physical properties such as bulk modulus of elasticity, dynamical longitudinal viscosity, and adhesion. 相似文献
66.
Hassan A. H. A. Ismail Abed el Aziz A. el R. M. Ahmed Young-Ha Lee Mousab Siddig Elhag Youngjin Kim Seungman Cha Yan Jin 《The Korean journal of parasitology》2021,59(2):121
We aimed to explore the population dynamics of snail in 3 sites of the White Nile in Sudan. More specifically, we aimed to investigate the annual patterns of snail populations that act as intermediate hosts of schistosomes and monthly snail infection rates and ecological characteristics presumably related to snail populations. We collected snails for 1 year monthly at 3 different shore sites in the vicinity of El Shajara along the White Nile river in Khartoum State, Sudan. In addition, we measured air and water temperatures, water turbidities, vegetation coverages, and water depths and current speeds. Most of the collected snails were Biomphalaria pfeifferi and Bulinus truncatus. The population densities of snails and their infection rates varied across survey sites. The collected snails liberated S. mansoni and S. haematobium cercariae as well as Amphistome and Echinostome cercariae. Infected snails were found during March–June. The ecological characteristics found to be associated with the absence of snails population were: high turbidity, deep water, low vegetation coverage (near absence of vegetation), high water temperature, and high current speed. To our knowledge, this is the first longitudinal study of the snail population and ecological characteristics in the main basin of the White Nile river. 相似文献
67.
Stéphane Guyot Laurence Pottier Lucie Bertheau Jennifer Dumont Eminence Dorelle Hondjuila Miokono Sébastien Dupont Mélanie Ragon Emmanuel Denimal Ambroise Marin John E. Hallsworth Laurent Beney Patrick Gervais 《Microbial biotechnology》2021,14(4):1445-1461
Although mechanisms involved in response of Saccharomyces cerevisiae to osmotic challenge are well described for low and sudden stresses, little is known about how cells respond to a gradual increase of the osmotic pressure (reduced water activity; aw) over several generations as it could encounter during drying in nature or in food processes. Using glycerol as a stressor, we propagated S. cerevisiae through a ramp of the osmotic pressure (up to high molar concentrations to achieve testing-to-destruction) at the rate of 1.5 MPa day-1 from 1.38 to 58.5 MPa (0.990–0.635 aw). Cultivability (measured at 1.38 MPa and at the harvest osmotic pressure) and glucose consumption compared with the corresponding sudden stress showed that yeasts were able to grow until about 10.5 MPa (0.926 aw) and to survive until about 58.5 MPa, whereas glucose consumption occurred until 13.5 MPa (about 0.915 aw). Nevertheless, the ramp conferred an advantage since yeasts harvested at 10.5 and 34.5 MPa (0.778 aw) showed a greater cultivability than glycerol-shocked cells after a subsequent shock at 200 MPa (0.234 aw) for 2 days. FTIR analysis revealed structural changes in wall and proteins in the range 1.38–10.5 MPa, which would be likely to be involved in the resistance at extreme osmotic pressure. 相似文献
68.
Keymanthri Moodley Stuart Rennie Frieda Behets Adetayo Emmanuel Obasa Robert Yemesi Laurent Ravez Patrick Kayembe Darius Makindu Alwyn Mwinga Walter Jaoko 《Developing world bioethics》2021,21(1):36-43
The COVID‐19 pandemic has raised important universal public health challenges. Conceiving ethical responses to these challenges is a public health imperative but must take context into account. This is particularly important in sub‐Saharan Africa (SSA). In this paper, we examine how some of the ethical recommendations offered so far in high‐income countries might appear from a SSA perspective. We also reflect on some of the key ethical challenges raised by the COVID‐19 pandemic in low‐income countries suffering from chronic shortages in health care resources, and chronic high morbidity and mortality from non‐COVID‐19 causes. A parallel is drawn between the distribution of severity of COVID‐19 disease and the classic “Fortune at the bottom of the pyramid” model that is relevant in SSA. Focusing allocation of resources during COVID‐19 on the ‘thick’ part of the pyramid in Low‐to‐Middle Income Countries (LMICs) could be ethically justified on utilitarian and social justice grounds, since it prioritizes a large number of persons who have been economically and socially marginalized. During the pandemic, importing allocation frameworks focused on the apex of the pyramid from the global north may therefore not always be appropriate. In a post‐COVID‐19 world, we need to think strategically about how health care systems can be financed and structured to ensure broad access to adequate health care for all who need it. The root problems underlying health inequity, exposed by COVID‐19, must be addressed, not just to prepare for the next pandemic, but to care for people in resource poor settings in non‐pandemic times. 相似文献
69.
70.