全文获取类型
收费全文 | 1669篇 |
免费 | 130篇 |
国内免费 | 3篇 |
出版年
2023年 | 16篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 10篇 |
2019年 | 20篇 |
2018年 | 50篇 |
2017年 | 24篇 |
2016年 | 46篇 |
2015年 | 99篇 |
2014年 | 92篇 |
2013年 | 104篇 |
2012年 | 109篇 |
2011年 | 126篇 |
2010年 | 72篇 |
2009年 | 67篇 |
2008年 | 98篇 |
2007年 | 91篇 |
2006年 | 71篇 |
2005年 | 76篇 |
2004年 | 70篇 |
2003年 | 68篇 |
2002年 | 45篇 |
2001年 | 21篇 |
2000年 | 24篇 |
1999年 | 25篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 21篇 |
1991年 | 25篇 |
1990年 | 19篇 |
1989年 | 22篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1974年 | 7篇 |
1973年 | 13篇 |
1972年 | 11篇 |
1971年 | 6篇 |
1970年 | 8篇 |
排序方式: 共有1802条查询结果,搜索用时 15 毫秒
151.
Hemery G Chevalier S Bellon-Fontaine MN Haras D Orange N 《Journal of industrial microbiology & biotechnology》2007,34(1):49-54
Pseudomonads adapt to various ecological niches by forming biofilms, which first requires bacterial adhesion on surfaces. We studied the influence of growth temperature on surface physicochemical properties of Pseudomonas fluorescens MF37 and on its adhesive capacities onto inert surfaces. It presented a global hydrophilic character, measured by microbial adhesion to solvent (MATS), and showed a cell surface more hydrophilic at 8 and 28°C than at 17°C. Moreover, P.
fluorescens MF37 was more adhesive at 17°C. This critical temperature thus should be carefully taken into account in food safety. Adhesion onto inert surfaces is thus influenced by the growth temperature, which modifies the bacteria cell wall properties through changes in the outer membrane components. Therefore, we studied the effect of the loss of OprF, the major outer membrane protein, known to act as an adhesin (root, and endothelial cells). The OprF-deficient mutant was able to adhere to surfaces, but showed the same physicochemical and adhesion properties on abiotic surfaces whatever the growth temperature. OprF is thus not essential in this adhesion process. However, we suggest that OprF is involved in the bacterial environmental temperature sensing by P. fluorescens.This work was supported by a grant from the Région Bretagne (Doctoral fellowship to G.H.). 相似文献
152.
Sex and clonality in the little fire ant 总被引:2,自引:0,他引:2
Foucaud J Fournier D Orivel J Delabie JH Loiseau A Le Breton J Kergoat GJ Estoup A 《Molecular biology and evolution》2007,24(11):2465-2473
Reproduction systems are controlling the creation of new genetic variants as well as how natural selection can operate on these variants. Therefore, they had historically been one of the main foci of evolutionary biology studies. The little fire ant, Wasmannia auropunctata, has been found to display an extraordinary reproduction system, in which both males and female queens are produced clonally. So far, native sexual populations of W. auropunctata have not been identified. Our goals were to identify such sexual populations and investigate the origins of female parthenogenesis and male clonality. Using mitochondrial DNA and microsatellite markers in 17 native populations, we found that traditional sexual populations occurred in W. auropunctata and are likely the recent source of neighboring clonal populations. Queen parthenogenesis has probably evolved several times through mutational events. Male clonality is tightly linked to queen parthenogenesis and thus appears to be female controlled. Its origin could be accounted for by 2 mutually exclusive hypotheses: either by the expected coevolution of the 2 sexes (i.e., a variant of the maternal genome elimination hypothesis) or by a shared mechanistic origin (i.e., by the production of anucleate ovules by parthenogenetic queens). Our results also show that W. auropunctata males and females do not form separate evolutionary units and are unlikely to be engaged in an all-out battle of sexes. This work opens up new perspectives for studies on the adaptive significance and evolutionary stability of mixed sexual and clonal reproduction systems in living organisms. 相似文献
153.
Gaël Ruiz Vincent Gloaguen Robert Granet Annette Roy Aziza Mouradi-Givernaud François Louvet Pierre Krausz 《Journal of applied phycology》2007,19(1):1-13
The synthesis of hydrophobic plastic films was performed by acylation of agaroids with lauroyl chloride in the N,N-dimethylacetamide
homogeneous system. All the plastic films were characterized by FT-IR spectroscopy and their degrees of substitution (DS)
was deduced from their 1H-NMR spectra. In addition, thermomechanical feature of plastic films were analyzed and compared to those obtained from other
kinds of hydrophobic plastic films. Latin square design of experiments helped us to determine optimized experimental conditions
and identify the most important factors. Hence, mild conditions of acylation (90∘C, 1 eq/OH of lauroyl chloride, 1 eq/OH of
4-dimethylaminopyridine, 5,min) led to the production of highly substituted plastic films (DS = 3.62; maximum 4) with a high
weight yield (211%) displaying mechanical properties close to polyethylene low density. 相似文献
154.
Dowling AJ Waterfield NR Hares MC Le Goff G Streuli CH ffrench-Constant RH 《Cellular microbiology》2007,9(10):2470-2484
Photorhabdus are Gram-negative, nematode-vectored bacteria that produce toxins to kill their insect hosts. The expression of one of these, Makes caterpillars floppy 1 (Mcf1), is sufficient to allow Escherichia coli to survive within, and kill, caterpillars which are otherwise able to clear E. coli infection. Mcf1 treated caterpillars show rapid loss of body turgor (the 'floppy' phenotype) and death is associated with massive apoptosis of both the midgut epithelium and insect phagocytes. Mammalian tissue culture cells treated with Mcf1 also display key features of apoptosis including zeiosis, apoptotic nuclear morphology, DNA laddering, activation of the effector caspase-3 and PARP cleavage. As Mcf1 carries a single BH3-like domain, here we investigate the hypothesis that this toxin promotes apoptosis via the mitochondrial pathway by mimicking a BH3 domain-only protein. Consistent with this hypothesis, a double mutant within the BH3-like domain causes a dramatic decline in apoptosis. Mcf1 also alters mitochondrial membrane potential and triggers the release of cytochrome c. Cells overexpressing Bcl-x(L), an anti-apoptotic Bcl-2 family member, are resistant to Mcf1-mediated apoptosis, as are cells deficient in Bax. In addition, translocation of Bax to the mitochondrion is observed in response to Mcf1 treatment. Together, these results show that Mcf1 mediates apoptosis via the mitochondrial pathway, and are consistent with the hypothesis that the BH3-like domain in Mcf1 is a functional requirement for the pro-apoptotic activity of Mcf1. 相似文献
155.
Phytophagous insects have many strategies to escape parasitoids, for example by hiding eggs into plant tissues, but oviposition
in holes made by another insect is rather scarce. The cypress seed bug Orsillus maculatus Fieber (Heteroptera: Lygaeidae) is strictly dependent on the availability of cones of Cupressus sempervirens L. to oviposit. Females lay eggs either in exit holes cut through the cone scale by emerging adults of the cypress seed chalcid,
Megastigmus wachtli Seitner (Hymenoptera: Torymidae), or on the inner side of scales of partly open cones. A recently discovered egg parasitoid
belonging to the genus Telenomus has been shown to attack bug eggs in both oviposition sites. In this paper we investigated the parasitoid performance according
to oviposition sites. Field samplings were conducted in two evergreen cypress orchards located in the south of France. The
distribution and condition of the egg patches were compared between the two locations and oviposition sites. Seed bugs preferred
to oviposit in emergence holes of M. wachtli, and parasitoid performance was higher in eggs laid on cone scales. The chalcid emergence holes seemed to ensure bug eggs
with enemy-free space. Oviposition site selection could be an adaptive strategy to escape parasitoid attack. 相似文献
156.
157.
Novosel N. Mišić Radić T. Levak Zorinc M. Zemla J. Lekka M. Vrana I. Gašparović B. Horvat L. Kasum D. Legović T. Žutinić P. Gligora Udovič M. Ivošević DeNardis N. 《Journal of applied phycology》2022,34(3):1293-1309
Journal of Applied Phycology - This study examines how salinity reduction triggers the response of three marine microalgae at the molecular and unicellular levels in terms of chemical, mechanical,... 相似文献
158.
Characterization of postdive recovery using sound recordings and its relationship to dive duration,exertion, and foraging effort of southern elephant seals (Mirounga leonina)
下载免费PDF全文
![点击此处可从《Marine Mammal Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alexandre Génin Gaëtan Richard Joffrey Jouma'a Baptiste Picard Nory El Ksabi Jade Vacquié Garcia Christophe Guinet 《Marine Mammal Science》2015,31(4):1452-1470
It is notoriously difficult to measure physiological parameters in cryptic free‐ranging marine mammals. However, it is critical to understand how marine mammals manage their energy expenditure and their diving behavior in environments where the predation risks are low and where survival is mainly linked to capacities to maintain physiological homeostasis and energy budget balance. Elephant seals are top marine predators that dive deeply and continuously when at sea. Using acoustic recorders deployed on two postbreeding southern elephant seals (SES) females, we developed methods to automatically estimate breathing frequency at the surface. Using this method, we found that seals took successive identical breaths at high frequency (0.29 Hz) when recovering at the surface and that breath count was strongly related to postdive surfacing time. In addition, dive depth was the main factor explaining surfacing time through the effects of dive duration and total underwater swimming effort exerted. Finally, we found that recovery does not only occur over one dive timescale, but over a multidive time scale for one individual. The way these predators manage their recovery will determine how they respond to the change in oceanic water column structure in the future. 相似文献
159.
160.
Climate change is expected to bring about profound rearrangement of ecological communities by affecting individual species distributions. The resulting communities arise from the idiosyncratic responses of species to future changes, which ultimately relate to both shrinking and expanding species ranges. While spatial patterns of colonisation and extirpation events have received great attention, the identification of specific drivers remains poorly explored. This study aims to investigate the relative contribution of species gain and loss to the turnover of fish assemblages in French rivers under future climate change, and to identify their principal drivers. Future projections of potential habitat suitability in 2080 derived from species distribution models for 40 fish species showed that colonisations and extirpations could play counterbalancing roles in the reshuffling of communities. Simultaneously, these two processes exhibited patchy spatial patterns, segregated along the longitudinal and altitudinal gradients, resulting in dramatic species turnover of ~ 60% of the current composition of species assemblages. Beyond the effect of topographic location, colonisations were found to be driven by temperature seasonality while extirpations were affected by modifications in both thermal and precipitation regimes. These results generate the possibility of developing ecosystem‐based management tools focused on the early identification of areas where particular species may be sensitive to climate changes. Disentangling the drivers of colonisation and extirpation processes provides ready‐to‐use information that may be easily integrated into conservation planning. This information could be used to identify potential hotspots of species gain and loss and to then compare these hotspots with newly favourable areas so as to consider their actual accessibility in order to facilitate future range shifts. 相似文献