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101.
102.
Assessment of Changes in Biodiversity when a Community of Ultramicrobacteria Isolated from Groundwater Is Stimulated to Form a Biofilm 总被引:5,自引:0,他引:5
With the continuing increase of ultraviolet-B radiation (UVBR: 280-320 nm) fluxes toward the Earth's surface, there is concern
regarding a possible negative impact on heterotrophic bacterioplankton. The effects of enhanced UVBR on a natural bacterioplankton
community were studied during a 7-day experiment conducted in mesocosms (1500 L). Four light regimes were tested: natural
light, 280 to 313 nm excluded UVBR, and two levels of UVBR enhancement. During the first 3 days of the experiment characterized
by high inorganic nutrient concentrations (nitrates > 1 μmol L-1 and ammonium > 0.1 μmol L-l), UVBR had no effect on both
bacterial abundances and activities. From day 4 to the end of the experiment, nitrate concentrations remained low (<1 μmol
L-1) and those of ammonium varied with a general tendency of decrease. During this period, bacterial abundances increased
more rapidly in the UVBR enhanced treatments, reaching on the last day of the experiment values that were 39 to 73% higher
than those observed in the natural UVBR treatment. 3H-Thymidine (TdR) incorporation rarely showed a significant inhibiting
effect of UVBR. However, when expressed per bacterium, TdR incorporation decreased by approximately 40% with the UVBR enhancement
above natural levels. Two explanations are possible. First, we know that UVBR reduced protozooplankton bacterivory, leading
to an increase in the bacterial abundance. It may be that this increase in community abundance compensated for the UVBR inhibition
of bacterial activity at the cellular level. Alternatively, community production may have been set by constant nutrient supply
rates; UVBR "inhibition" was then a result of accumulating dead cells, a taxonomic shift, or increased competition among the
more abundant cells. 相似文献
103.
Intergeneric gene transfer mediated by plant protoplast fusion 总被引:1,自引:0,他引:1
Dénes Dudits Olga Fejér Gyula Hadlaczky Csaba Koncz Gábor B. Lázár Gábor Horváth 《Molecular & general genetics : MGG》1980,179(2):283-288
Summary In attempts at somatic transfer of plant genomes of reduced size, X-irradiated leaf protoplasts of parsley (Petroselinum hortense, 2n=22) were fused with cell culture protoplasts of a nuclear albino mutant of carrot (Daucus carota, 2n=18). Introduction of genes from the irradiated parsley nuclei into the carrot genome was shown by the correction of the albino defect and by the appearance of parsley isoenzymes in selected green tissues and plants. The cytological studies provided information on significant deviation from the amphidiploid chromosome number. The high frequency of cells with 2n=19, 2n=38 and regeneration of plants with 2n=19 chromosomes can indicate that the elimination of parsley chromosomes is incomplete. A correlation was found between the lethality of selected tissues and differentiated or undifferentiated stages of the cells. 相似文献
104.
Zeineb Bouhlel Alexandre A. Arnold Jean-Sébastien Deschênes Jean-Luc Mouget Dror E. Warschawski Réjean Tremblay Isabelle Marcotte 《生物化学与生物物理学报:生物膜》2021,1863(9):183642
This work investigates the potential probiotic effect of marennine - a natural pigment produced by the diatom Haslea ostrearia - on Vibrio splendidus. These marine bacteria are often considered a threat for aquaculture; therefore, chemical antibiotics can be required to reduce bacterial outbreaks. In vivo 2H solid-state NMR was used to probe the effects of marennine on the bacterial membrane in the exponential and stationary phases. Comparisons were made with polymyxin B (PxB) - an antibiotic used in aquaculture and known to interact with Gram(?) bacteria membranes. We also investigated the effect of marennine using 31P solid-state NMR on model membranes. Our results show that marennine has little effect on phospholipid headgroups dynamics, but reduces the acyl chain fluidity. Our data suggest that the two antimicrobial agents perturb V. splendidus membranes through different mechanisms. While PxB would alter the bacterial outer and inner membranes, marennine would act through a membrane stiffening mechanism, without affecting the bilayer integrity. Our study proposes this microalgal pigment, which is harmless for humans, as a potential treatment against vibriosis. 相似文献
105.
LeChasseur Y Dufour S Lavertu G Bories C Deschênes M Vallée R De Koninck Y 《Nature methods》2011,8(4):319-325
Recording electrical activity from identified neurons in intact tissue is key to understanding their role in information processing. Recent fluorescence labeling techniques have opened new possibilities to combine electrophysiological recording with optical detection of individual neurons deep in brain tissue. For this purpose we developed dual-core fiberoptics-based microprobes, with an optical core to locally excite and collect fluorescence, and an electrolyte-filled hollow core for extracellular single unit electrophysiology. This design provides microprobes with tips < 10 μm, enabling analyses with single-cell optical resolution. We demonstrate combined electrical and optical detection of single fluorescent neurons in rats and mice. We combined electrical recordings and optical Ca2(+) measurements from single thalamic relay neurons in rats, and achieved detection and activation of single channelrhodopsin-expressing neurons in Thy1::ChR2-YFP transgenic mice. The microprobe expands possibilities for in vivo electrophysiological recording, providing parallel access to single-cell optical monitoring and control. 相似文献
106.
Cserháti M Turóczy Z Zombori Z Cserzo M Dudits D Pongor S Györgyey J 《Molecular genetics and genomics : MGG》2011,285(5):375-391
107.
José C. Carvalho Pedro Cardoso Paulo A. V. Borges Dénes Schmera János Podani 《Oikos》2013,122(6):825-834
Beta diversity and nestedness are central concepts of ecology and biogeography and evaluation of their relationships is in the focus of contemporary ecological and conservation research. Beta diversity patterns are originated from two distinct processes: the replacement (or turnover) of species and the loss (or gain) of species leading to richness differences. Nested distributional patterns are generally thought to have a component deriving from beta diversity which is independent of replacement processes. Quantification of these phenomena is often made by calculating a measure of beta diversity, and the resulting value being subsequently partitioned into a contribution by species replacement plus a fraction shared by beta diversity and nestedness. Three methods have been recently proposed for such partitioning, all of them based on pairwise comparisons of sites. In this paper, the performance of these methods was evaluated on theoretical grounds and tested by a simulation study in which different gradients of dissimilarity, with known degrees of species replacement and species loss, were created. Performance was also tested using empirical data addressing land‐use induced changes in endemic arthropod communities of the Terceira Island in the Azores. We found that the partitioning of βcc (dissimilarity in terms of the Jaccard index) into two additive fractions, β‐3 (dissimilarity due to species replacement) plus βrich (dissimilarity due to richness differences) reflects the species replacement and species loss processes across the simulated gradients in an ecologically and mathematically meaningful way, whilst the other two methods lack mathematical consistency and prove conceptually self‐contradictory. Moreover, the first method identified a selective local extinction process for endemic arthropods, triggered by land‐use changes, while the latter two methods overweighted the replacement component and led to false conclusions. Their basic flaw derives from the fact that the proposed replacement and nestedness components (deemed to account for species loss) are not scaled in the same way as the measure that accounts for the total dissimilarity (Sørensen and Jaccard indices). We therefore recommend the use of βcc=β‐3+βrich, since its components are scaled in the same units and their responses are proportional to the replacement and the gain/loss of species. 相似文献
108.
109.
AbstractA unique form of optical ecological traps is polarised light pollution. Typical sources of this phenomenon is asphalt roads that attract a variety of polarotactic aquatic adult insects seeking horizontally polarised sources recognized as water surfaces. Several harmful effects of polarised light pollution have been previously demonstrated but no quantitative data are available in regard to the loss of a given adult population under these conditions. Our objective was to study the impact of an asphalt road parallel to a creek on the stonefly Perla abdominalis (Guérin-Méneville, 1838). Throughout a three-year study, by comparing the number of exuviae along a stream and the number of adult individuals attracted by the road, we established that 19.6% of the females were trapped by the nearby road. By measuring the reflection–polarisation characteristics of the stream and asphalt surface, we demonstrated that the road may act as attractive, supernormal stimulus for adult females. 相似文献
110.
Salamon Andras Maszlag-Török Rita Veres Gábor Boros Fanni Annamária Vágvölgyi-Sümegi Evelin Somogyi Anett Vécsei László Klivényi Péter Zádori Dénes 《Neurochemical research》2020,45(9):2072-2081
Neurochemical Research - The potential role of Sirt1 and Sirt2 subtypes of Sirtuins (class III NAD+-dependent deacetylases) in the pathogenesis of Huntington’s disease (HD) has been... 相似文献