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1.
Turtles are among the most intriguing amniotes but their communication and signaling have rarely been studied. Traditionally, they have been seen as basically just silent armored ‘walking stones’ with complex physiology but no altruism, maternal care, or aesthetic perception. Recently, however, we have witnessed a radical change in the perception of turtle behavioral and cognitive skills. In our study, we start by reviewing some recent findings pertaining to various highly developed behavioral and cognitive patterns with special emphasis on turtles. Then we focus on freshwater turtles and use data about their sexual behavior and size sexual dimorphism (SSD) to test whether conspicuous coloration of the head is in these animals related to sexual processes. We found that absence of aggressive mating behavior is statistically associated with the presence of conspicuous coloration on turtles’ heads. It also seems that while species with female-biased SSD are characterised by conspicuously colored head ornaments, in species with male-biased SSD conspicuous coloration is absent. Unlike large females, males thus seem to be under pressure to develop conspicuous coloration and engage in non-aggressive behavior using signaling to succeed in courtship. And finally, we discuss possible roles of head color patterns in turtle communication during mating. 相似文献
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Saxifraga marginata Sternb. is divided into three subspecies:S. m. subsp.marginata, S. m. subsp.bubakii (Rohlena)Chrtek etSoják,S. m. subsp.karadzicensis (Degen etKo?anin)Chrtek etSoják (environments of Skopje, Macedonia). 相似文献
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In total 73 species of Euglena were ordered according to their saprobic index (S) and saprobic valency starting with species tolerating a heavy organic pollution and ending with those from most clean water. This paper is meant as an addition to the Ergebnisse der Limnologie, Heft 7 (Sládeek, 1973). 相似文献
5.
Kevin E. Riley Jane S. Murray Jindřich Fanfrlík Jan Řezáč Ricardo J. Solá Monica C. Concha Felix M. Ramos Peter Politzer 《Journal of molecular modeling》2013,19(11):4651-4659
In a previous study we investigated the effects of aromatic fluorine substitution on the strengths of the halogen bonds in halobenzene…acetone complexes (halo?=?chloro, bromo, and iodo). In this work, we have examined the origins of these halogen bonds (excluding the iodo systems), more specifically, the relative contributions of electrostatic and dispersion forces in these interactions and how these contributions change when halogen σ-holes are modified. These studies have been carried out using density functional symmetry adapted perturbation theory (DFT-SAPT) and through analyses of intermolecular correlation energies and molecular electrostatic potentials. It is found that electrostatic and dispersion contributions to attraction in halogen bonds vary from complex to complex, but are generally quite similar in magnitude. Not surprisingly, increasing the size and positive nature of a halogen’s σ-hole dramatically enhances the strength of the electrostatic component of the halogen bonding interaction. Not so obviously, halogens with larger, more positive σ-holes tend to exhibit weaker dispersion interactions, which is attributable to the lower local polarizabilities of the larger σ-holes. Figure
In this work we investigate the roles played by electrostatic and dispersion forces in stabilizing halogen bonding interactions. 相似文献
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Spiwok V Lipovová P Skálová T Dusková J Dohnálek J Hasek J Russell NJ Králová B 《Journal of molecular modeling》2007,13(4):485-497
Enzymes from cold-adapted species are significantly more active at low temperatures, even those close to zero Celsius, but
the rationale of this adaptation is complex and relatively poorly understood. It is commonly stated that there is a relationship
between the flexibility of an enzyme and its catalytic activity at low temperature. This paper gives the results of a study
using molecular dynamics simulations performed for five pairs of enzymes, each pair comprising a cold-active enzyme plus its
mesophilic or thermophilic counterpart. The enzyme pairs included α-amylase, citrate synthase, malate dehydrogenase, alkaline
protease and xylanase. Numerous sites with elevated flexibility were observed in all enzymes; however, differences in flexibilities
were not striking. Nevertheless, amino acid residues common in both enzymes of a pair (not present in insertions of a structure
alignment) are generally more flexible in the cold-active enzymes. The further application of principle component analysis
to the protein dynamics revealed that there are differences in the rate and/or extent of opening and closing of the active
sites. The results indicate that protein dynamics play an important role in catalytic processes where structural rearrangements,
such as those required for active site access by substrate, are involved. They also support the notion that cold adaptation
may have evolved by selective changes in regions of enzyme structure rather than in global change to the whole protein.
Figure Collective motions in Cα atoms of the active site of cold-active xylanase
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
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Riley KE Murray JS Fanfrlík J Rezáč J Solá RJ Concha MC Ramos FM Politzer P 《Journal of molecular modeling》2011,17(12):3309-3318
In the past several years, halogen bonds have been shown to be relevant in crystal engineering and biomedical applications.
One of the reasons for the utility of these types of noncovalent interactions in the development of, for example, pharmaceutical
ligands is that their strengths and geometric properties are very tunable. That is, substitution of atoms or chemical groups
in the vicinity of a halogen can have a very strong effect on the strength of the halogen bond. In this study we investigate
halogen-bonding interactions involving aromatically-bound halogens (Cl, Br, and I) and a carbonyl oxygen. The properties of
these halogen bonds are modulated by substitution of aromatic hydrogens with fluorines, which are very electronegative. It
is found that these types of substitutions have dramatic effects on the strengths of the halogen bonds, leading to interactions
that can be up to 100% stronger. Very good correlations are obtained between the interaction energies and the magnitudes of
the positive electrostatic potentials (σ-holes) on the halogens. Interestingly, it is seen that the substitution of fluorines
in systems containing smaller halogens results in electrostatic potentials resembling those of systems with larger halogens,
with correspondingly stronger interaction energies. It is also shown that aromatic fluorine substitutions affect the optimal
geometries of the halogen-bonded complexes, often as the result of secondary interactions. 相似文献