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41.
The recurrent drying out of small streams in past decades has shown an urgent need to pay attention to the impact of global
climate change. The objectives of this study were to describe the effect of drying out on the composition of the mayfly taxocene
and evaluate the relevance of individual species traits for survival of mayflies to drying out. The mayfly taxocenes of two
model localities, one at an intermittent and one at a permanent brook, were investigated in 2002, 2003 and 2005. Compared
with the permanent stream, the taxocene of the intermittent stream was short of nine species, foremost rheobionts and high
oxygen demand species. To explain further differences between both stream types in survival and recolonisation ability, 15
species traits were evaluated. These included so-called “ecological traits” (e.g., habitat and substrate range, density, distribution,
current velocity adaptation) and “biological traits” connected with life cycle and larval/adult adaptations. Species showing
the highest number of advantageous traits (with only exception of Electrogena sp. cf. ujhelyii — species of taxonomically unclear status) were able to successfully survive under the unfavourable conditions of the intermittent
brook. Biological traits considered more important in many respects seem to be good predictors for assessing sensitivity to
extreme temperature changes, hydrological regime fluctuations and the survival/recolonisation ability of species in exposed
habitats. 相似文献
42.
43.
Evaluation and indirect estimation of nitrate losses from the agricultural microbasin Rybárik 总被引:1,自引:0,他引:1
The long-term trends of mean monthly nitrate concentrations in stream and drainage runoff were evaluated in the experimental
microbasin Rybárik (0.119 km2) at the Institute of Hydrology, Slovak Academy of Sciences, during the period 1987–2005. The results of analyses indicate
a decreasing trend of nitrate concentration after the year 1989, but with relatively high losses in some years and relatively
low losses in other years. This decreasing trend is mainly caused by a decrease in the use of nitrogen fertilizers. The nitrate
concentration in surface runoff strongly correlates with runoff and fertilization. Based on measured data, an empirical relation
was found describing the dependence of annual nitrate transport in the stream on annual runoff depth and on the annual amount
of applied nitrogen fertilizers.
Presented at the International Conference on Bioclimatology and Natural Hazards, Poľana nad Detvou, Slovakia, 17–20 September
2007. 相似文献
44.
Aryl sulfamates were originally developed as inhibitors of steroid sulfatase, and have recently been shown to be powerful inactivators of a bacterial sulfatase, PaAtsA from Pseudomonas aeruginosa. We demonstrate that a simple aryl sulfamate, 3-nitrophenyl sulfamate, can inactivate sulfatases from various sources including snail, limpet and abalone. In each case inactivation was time-dependent and active-site directed, as demonstrated by protection against inactivation by substrate. These results suggest that such easily acquired aryl sulfamates can be used as reliable biochemical reagents for the study of sulfatases from a diverse array of sources. 相似文献
45.
46.
Interaction of leukemia blasts with the bone marrow extracellular matrix often results in protection of leukemia cells from chemotherapy and in persistence of the residual disease which is on the basis of subsequent relapses. The adhesion signaling pathways have been extensively studied in adherent cells as well as in mature haematopoietic cells, but the adhesion structures and signaling in haematopoietic stem and progenitor cells, either normal or malignant, are much less explored. We analyzed the interaction of leukemia cells with fibronectin (FN) using interference reflection microscopy, immunofluorescence, measurement of adherent cell fraction, real-time microimpedance measurement and live cell imaging. We found that leukemia cells form very dynamic adhesion structures similar to early stages of focal adhesions. In contrast to adherent cells, where Src family kinases (SFK) belong to important regulators of focal adhesion dynamics, we observed only minor effects of SFK inhibitor dasatinib on leukemia cell binding to FN. The relatively weak involvement of SFK in adhesion structure regulation might be associated with the lack of cytoskeletal mechanical tension in leukemia cells. On the other hand, active Lyn kinase was found to specifically localize to leukemia cell adhesion structures and a less firm cell attachment to FN was often associated with higher Lyn activity (this unexpectedly occurred also after cell treatment with the inhibitor SKI-1). Lyn thus may be important for signaling from integrin-associated complexes to other processes in leukemia cells. 相似文献
47.
Sulfotransferases and sulfatases are the major enzymes responsible for sulfate transfer processes. The past two years have seen the elucidation of new functions for these enzymes, and a great progression in their structural characterization, which confirms that these two types of enzymes possess a highly conserved fold. For catalytic activity, sulfatases must contain a formylglycine residue, which is generated by various formylglycine-generating enzymes. Mechanistic and structural details have recently been obtained for a group of cofactor-independent formylglycine-generating enzymes termed FGEs. Finally, an increasing light has been cast upon the mechanism of sulfatase inactivation by a group of clinically important agents, the aryl sulfamates. 相似文献
48.
Jan Bartoš Etienne Paux Robert Kofler Miroslava Havránková David Kopecký Pavla Suchánková Jan Šafář Hana Šimková Christopher D Town Tamas Lelley Catherine Feuillet Jaroslav Doležel 《BMC plant biology》2008,8(1):1-12
Background
Thellungiella halophila (also known as Thellungiella salsuginea) is a model halophyte with a small plant size, short life cycle, and small genome. It easily undergoes genetic transformation by the floral dipping method used with its close relative, Arabidopsis thaliana. Thellungiella genes exhibit high sequence identity (approximately 90% at the cDNA level) with Arabidopsis genes. Furthermore, Thellungiella not only shows tolerance to extreme salinity stress, but also to chilling, freezing, and ozone stress, supporting the use of Thellungiella as a good genomic resource in studies of abiotic stress tolerance.Results
We constructed a full-length enriched Thellungiella (Shan Dong ecotype) cDNA library from various tissues and whole plants subjected to environmental stresses, including high salinity, chilling, freezing, and abscisic acid treatment. We randomly selected about 20 000 clones and sequenced them from both ends to obtain a total of 35 171 sequences. CAP3 software was used to assemble the sequences and cluster them into 9569 nonredundant cDNA groups. We named these cDNAs "RTFL" (RIKEN Thellungiella Full-Length) cDNAs. Information on functional domains and Gene Ontology (GO) terms for the RTFL cDNAs were obtained using InterPro. The 8289 genes assigned to InterPro IDs were classified according to the GO terms using Plant GO Slim. Categorical comparison between the whole Arabidopsis genome and Thellungiella genes showing low identity to Arabidopsis genes revealed that the population of Thellungiella transport genes is approximately 1.5 times the size of the corresponding Arabidopsis genes. This suggests that these genes regulate a unique ion transportation system in Thellungiella.Conclusion
As the number of Thellungiella halophila (Thellungiella salsuginea) expressed sequence tags (ESTs) was 9388 in July 2008, the number of ESTs has increased to approximately four times the original value as a result of this effort. Our sequences will thus contribute to correct future annotation of the Thellungiella genome sequence. The full-length enriched cDNA clones will enable the construction of overexpressing mutant plants by introduction of the cDNAs driven by a constitutive promoter, the complementation of Thellungiella mutants, and the determination of promoter regions in the Thellungiella genome. 相似文献49.
In a river, the flow directly affects the physical and chemical properties of its water, with further consequences for aquatic
biota. Land use practices and vegetation cover play a significant role in the water cycle. The wide-spread perception of forest
cover, in terms of hydrology is that forests may reduce water runoff: although in rare instances the contrary has been reported.
Water runoff varies seasonally and depends on the forest tree species. By no means can it be considered constant over large
expanses of area or for various rainfall patterns. In this paper, the results of a long-term hydrological survey conducted
in two experimental microbasins (operated by the Institute of Hydrology SAS, IH SAS) with different land use practices are
presented. The Rybárik microbasin (0.119 km2) is dominated by row crop production. The basin was 70% cultivated by the state farm and 30% by a private farm. The Lesny
microbasin (0.086 km2) is covered by a deciduous hornbeam regrowth forest (Carpinus betulus). The analysis revealed that the difference in the
runoff from the forest and the agricultural land increases with increasing precipitation; however, at some point (extreme
precipitations with low probability) the runoff from these basins is nearly equal. 相似文献
50.
Petr Kovář Miroslav Pospíšil Petr Malý Zdeněk Klika Pavla Čapková Petra Horáková Marta Valášková 《Journal of molecular modeling》2009,15(11):1391-1396
The surface area of various types of montmorillonites (MMT) with different values of layer charge plays a very important role
in surface arrangement of methylene blue cations (MB). Photoluminescence measurements can be strongly or partially influenced
by this surface arrangement of cations. For these reasons and on the basis of our previous results, molecular simulations
were performed for various types of montmorillonites covered with methylene blue cations. Adsorption of methylene blue cations
on Na-Wyoming MMT surface is different from Ca-Cheto MMT. In the case of Wyoming with a lower layer charge, MB cations lie
parallel to the silicate layer for all investigated samples. On the other hand, Cheto surface is covered with a higher amount
of MB cations. The results obtained from molecular modeling indicate that MB lies parallel to low loading case and become
tilted with respect to layer for a higher loading. Moreover, a higher amount of MB cations covering the silicate layer are
much less energy-stable. A higher loading of MB cations leads to aggregates but at low loading MB cations degrade to monomers. 相似文献