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排序方式: 共有357条查询结果,搜索用时 31 毫秒
1.
Torbjrg Bjelland 《植被学杂志》2003,14(4):525-534
Abstract. The effects of vegetation cover, radiation, micro‐habitat variables and maritime influence on the floristic composition of a saxicolous community in Vingen, western Norway were studied. Particular emphasis is put on the local distribution of Fuscidea cyathoides, Ochrolechia tartarea, Ophioparma ventosa and Pertusaria corallina. Very little of the variation in the lichen community composition is directly related to measured micro‐environmental variables but variance partitioning shows that vegetation cover explains more of the floristic variation than radiation, maritime influence and microhabitat variables. Logistic regression analyses nevertheless indicate that the micro‐environment influences the spatial distribution of the four species. The high fraction of unexplained floristic variation, 91%, is suggested to result from (1) lack of fit of data to the response model; (2) some influential environmental variables that have not been recorded; (3) local historical factors that affect present day distribution and/or (4) apparent randomness in colonization. The results also agree with the view that the four lichen species in this study are able to co‐exist in the long‐term because of different spatial distributions resulting from different strategies with respect to ecology, dispersion and interaction. 相似文献
2.
Dionisios Youlatos 《Primates; journal of primatology》1998,39(4):449-457
Recent studies on the positional behavior of primates reveal that significant seasonal variation occurs in both locomotion
and postures that is related to changes in diet and foraging techniques. Howling monkeys (genusAlouatta), which also have a seasonally varied diet, are predicted to have correspondingly varied positional behaviors. Two groups
of red howling monkeys were studied in a primary rain forest in French Guinana during the dry and wet seasons. During the
dry season, when howler diet is based mainly on leaves, howlers traveled more frequently by quadrupedal walking on large supports,
a mode of progression that is probably inexpensive energetically and relatively stable. During feeding, quadrupedal and tripedal
stand contributed considerably, a posture probably associated with the equal distribution of leaves within a tree crown. In
contrast, during the wet season, when fruit was abundant, howlers fed very frequently by sitting on large supports, probably
because fruit consumption required more time for special manipulation. However, most seasonal changes in feeding postures,
and in travel and feeding locomotion, were difficult to associate directly with dietary shifts. These behavioral changes may
be more highly correlated with slight modifications in microhabitat use (horizontal and vertical daily ranges, similar and
alternative arboreal pathways) that are not considered in this paper. 相似文献
3.
Synopsis Larval development commences with first exogenous feeding, and ends with final remodelling of caenogenetic structures into
the definitive organs of juvenile and adult. For the intertidal cyprinodontid Adinia xenica this generally corresponds to the interval between hatching and completion of scalation. The final step of the embryo period
is a resting interval of variable duration. Embryos were induced to hatch after 2 and 10 days of this near arrest. Although
the general pattern of larval development was the same for both groups, differences were observed in the rates and order of
calcification of skeletal elements, fin differentiation and growth, and scalation. For example, embryos hatching 8 days later
in the resting interval were already pattially calcified, but completed calcification at a slower rate than the group hatching
after 2 days. These differences may be due to effects of the duration of the resting interval itself; or they may reflect
genetic variation of which age at hatching is only one manifestation. 相似文献
4.
《Chronobiology international》2013,30(2):77-86
The locomotor activity rhythms of 24 isochromosomal strains of Drosophila melanogaster were recorded in constant conditions, using an experimental design suitable for the serial screening with so many strains using limited equipment. The data obtained were subjected to biometrical genetic analysis. The results show that four characteristics of the rhythms (period, phase, definition, and waveform) display genetically based variation in expression and that each appears to be affected by a range of genes. 相似文献
5.
In order to be able to simulate long time and large space scale properties of polymer melts one has to resort to coarse grained models, for example by subdividing all polymers into parts and restricting attention to the center of mass positions and velocities of these parts. The dynamics of these variables is governed by Langevin equations in which the free energy obtained by integrating the remaining variables provides the potential of the conservative forces. In general this leads to many particle interactions on the coarse-grained level. Methods suggested in the literature to represent these many particle interactions by effective two body interactions are reviewed and a new method, based on the Gibbs-Bogoliubov inequality, is proposed. The reason why none of these methods is able to reproduce the pressure of the underlying atomistic model is discussed. 相似文献
6.
James A. Wanner 《American journal of physical anthropology》1977,47(1):99-102
An analysis of the anterior patellar groove of the human femur shows considerable variation in its medial and lateral spects. The groove itself, measured by the angle it encloses, shows considerably less variation than its individual components. The suggested functional relationship between bicondylar angle and lateral elevation of the patellar groove does not obtain for this sample. 相似文献
7.
Luís Reino 《Journal of Ornithology》2005,146(4):377-382
The common waxbill Estrilda astrild was first introduced to Portugal, from Africa, in 1964, from where it has spread to much of the country and to Spain. We
modelled the expansion of this species on a 20×20-km UTM grid in 4-year periods from 1964 to 1999. Colonisation process on
a grid was modelled as a function of several biophysical and spatio-temporal variables through the fitting of several multiple
logistic equations. Variation partitioning confirmed the importance of the spatial-temporal component, explaining 33% of the
total variation, followed by the combined effects of both environmental and spatial-temporal variables (around 25%). Only
11% of the total variation can be attributed strictly to the considered environmental factors. 相似文献
8.
9.
Variations and similarities in our individual genomes are part of our history, our heritage, and our identity. Some human genomic variants are associated with common traits such as hair and eye color, while others are associated with susceptibility to disease or response to drug treatment. Identifying the human variations producing clinically relevant phenotypic changes is critical for providing accurate and personalized diagnosis, prognosis, and treatment for diseases. Furthermore, a better understanding of the molecular underpinning of disease can lead to development of new drug targets for precision medicine. Several resources have been designed for collecting and storing human genomic variations in highly structured, easily accessible databases. Unfortunately, a vast amount of information about these genetic variants and their functional and phenotypic associations is currently buried in the literature, only accessible by manual curation or sophisticated text text-mining technology to extract the relevant information. In addition, the low cost of sequencing technologies coupled with increasing computational power has enabled the development of numerous computational methodologies to predict the pathogenicity of human variants. This review provides a detailed comparison of current human variant resources, including HGMD, OMIM, ClinVar, and UniProt/Swiss-Prot, followed by an overview of the computational methods and techniques used to leverage the available data to predict novel deleterious variants. We expect these resources and tools to become the foundation for understanding the molecular details of genomic variants leading to disease, which in turn will enable the promise of precision medicine. 相似文献
10.
本文综述了IBDV的保护性抗原蛋白VP2与病毒形态、毒力变异、抗原变异间的关系及在诱导宿主细胞凋亡中的作用。同时也探讨了其在新型疫苗开发中的应用等方面的研究进展。 相似文献