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51.
Muskoxen are large herbivores living in Arctic environments. Lack of genetic variation in allozymes has made it difficult to study the social and genetic structure of this species. In this study, we have tried to find polymorphic microsatellite loci using both cattle-derived microsatellite primers and primers developed from a genomic plasmid library of muskoxen. Only limited variation was found for both sets of microsatellite loci. We conclude that this consistent low genetic variation is probably due to demographic features of the muskoxen populations rather than to methodological constraints caused by the transfer of microsatellites between species. 相似文献
52.
The hypothesis was tested that monozygotic (MZ) and dizygotic (DZ) twins, with their lower average birth weight, have higher adult blood pressure than their singleton brothers or sisters. From the Netherlands Twin Registry, 261 twin families were recruited from a young adult and an older adult cohort with mean ages of 26.2 and 50.4 respectively. These families yielded 204 MZ twins with 71 singleton siblings and 271 DZ twins with 103 of their singleton siblings. Anti-hypertensive medication use of these 649 participants was assessed twice with a two-year interval. Resting blood pressure was measured thrice during a standardized laboratory protocol. In spite of a significant difference in birth weight (1036 gram), no differences were found in anti-hypertensive medication use at both time points between twins and singletons nor between their resting laboratory diastolic or systolic blood pressure. These results applied to each gender and to both age cohorts. Limiting the analyses to matched twin-sibling pairs of the same families and taking current weight and height into account did not change the results; no evidence was found for a twin-singleton difference. It was concluded that estimates of genetic and environmental contributions to blood pressure deriving from twin studies do not appear to be biased and may be generalized to singletons. Our results suggest that the lower birth weight in twins does not reflect the intrauterine disadvantage described by the Barker hypothesis. 相似文献
53.
Lucas R Lopes Vitor AR Miranda Rodrigo A Goes Gabriel GA Souza Giuliana R Souza Jessica CS Rocha Victor RA Cossich Jamila A Perini 《Biology of sport / Institute of Sport》2021,38(4):703
The COVID-19 pandemic has presented significant challenges and implications for the sports community. Thus, this study aimed to describe the prevalence of COVID-19 in Brazilian athletes and identify the epidemiological, clinical, athletic, life and health factors associated with the disease in these individuals. A cross-sectional study was performed involving 414 athletes from 22 different sports using an online questionnaire from August to November 2020. The association between the athletes’ characteristics and COVID-19 was evaluated using a logistic regression model. The prevalence of COVID-19 was 8.5%, although only 40% of athletes reported having been tested. Being under 27 years of age (3-fold), having children (~5-fold), having a teammate test positive for COVID-19 (2.5-fold), and smoking (14-fold) were associated with a possible higher risk of disease. Almost 20% of athletes self-reported musculoskeletal injuries during the period of the pandemic that was studied. Athletes with a university education (P = 0.02), a profession other than sports (P < 0.001), those from a low-income family (P = 0.01), and public health system users (P = 0.04) were significantly less frequently tested for COVID-19, whereas international competitors, athletes who received a wage, and athletes who had a teammate who tested positive for COVID-19 were 2-, 3-, and 15-fold more likely to be tested for COVID-19, respectively. Approximately 26% of the athletes who tested negative or were untested reported more than three characteristic COVID-19 symptoms, and 11% of athletes who tested positive for COVID-19 were asymptomatic. The identification of modifiable (have children, smoking, and teammates positively tested) and non-modifiable (age under 27 years) factors related to COVID-19 in athletes can contribute to implementing surveillance programmes to decrease the incidence of COVID-19 in athletes and its negative impacts in sports. 相似文献
54.
Background
Leaf-cutting ants live in symbiosis with a fungus that they rear for food by providing it with live plant material. Until recently the fungus' main inferred function was to make otherwise inaccessible cell wall degradation products available to the ants, but new studies have shed doubt on this idea. To provide evidence for the cell wall degrading capacity of the attine ant symbiont, we designed PCR primers from conserved regions of known xylanase genes, to be used in PCR with genomic DNA from the symbiont as template. We also measured xylanase, cellulase and proteinase activities in the fungus gardens in order to investigate the dynamics of degradation activities. 相似文献55.
A recent study has discovered a novel extended phenotype of a nematode which alters its ant host to resemble ripe fruit. The infected ants are in turn eaten by frugivorous birds that disperse the nematode's eggs. 相似文献
56.
57.
Hymenopteran inquiline species have been proposed to originate by sympatric speciation through intraspecific social parasitism.
One such parasite, Myrmica microrubra, was recently synonymized with its Myrmica rubra host, because comparisons across Europe indicated insufficient genetic differentiation. Here, we use microsatellite markers
to study genetic differentiation more precisely in a sample of Finnish M. rubra and its inquilines collected at two localities, supplemented with mitochondrial DNA sequences. The parasite had much lower
genetic variation than the host at three of the four loci studied. Genetic differentiation between the host populations was
moderate (F
ST = 0.089), whereas the parasite populations were more strongly subdivided (F
ST = 0.440). The host and parasite were highly genetically differentiated both across populations (F
ST = 0.346) and in strict sympatry (0.327, 0.364), a result that remained robust both in a haplotype network and in PCA ordination.
Individual assignments of genotypes indicated that gene flow between sympatric host and inquiline populations is reduced by
about an order of magnitude relative to the gene flow within the morphs. Our results suggest that the parasitic morph of M. rubra may be an incipient species, but it remains unclear to what extent the observed genetic differentiation between host and
inquiline is due to possible assortative mating and selection against hybrids or to recurrent bottlenecking and genetic drift.
We conclude that an explicitly functional species concept would be unambiguous in treating this inquiline as a full species,
as it begets its own kind and maintains its integrity in spite of occasional interbreeding with the host. 相似文献
58.
B. Baer S. P. A. den Boer D. J. C. Kronauer D. R. Nash J. J. Boomsma 《Insectes Sociaux》2009,56(3):289-291
Attine ants are well known for their mutualistic symbiosis with fungus gardens, but many other symbionts and commensals have
been described. Here, we report the discovery of two clusters of large snake eggs in neighboring fungus gardens of a mature
Atta colombica colony. The eggs were completely embedded within the fungus garden and were ignored by the host ants, even when we placed
them into another, freshly excavated fungus garden of the same colony. All five eggs contained embryos and two snakes eventually
hatched, which we identified as being banded cat eyed snakes Leptodeira annulata L. Ant fungus gardens are likely to provide ideal climatic conditions for developing snake eggs and almost complete protection
from egg predation. Our observations therefore indicate that mature banded cat eyed snakes are able to enter and oviposit
in large and well defended Atta colonies without being attacked by ant soldiers and that also newly hatched snakes manage to avoid ant attacks when they
leaving their host colony. We speculate that L. annulata might use Atta and Acromyrmex leafcutter ant colonies as egg nurseries by some form of chemical insignificance, but more work is needed to understand the
details of this interaction.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
59.
JF Yuan SJ Zhang O Jafer RA Furlong OE Chausiaux CA Sargent GH Zhang NA Affara 《BMC microbiology》2009,9(1):246
Background
Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult. 相似文献60.