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501.
502.
The small, exclusively Australasian, anomalodesmatan familyMychamidae comprises only two genera; the shallow-burrowingMyadora and the cementing Myochama. This paper describes theanatomy ad cementing behaviour of Myochama anomioides and drawscomparisons with Myadora. The anatomy of Myochama anomioides is little different fromthat previously described for Myadora, except that they aremirror images. Valve inequality is not reflected in the organsof the mantle cavity in either taxon. Such differences whichare present, for example the reduction of the foot in Myochama,mostly relate to the adoption of a sessile habit. There arefew idfferences in mantle folds of the cementing and non-cementinggenus, except that in M. anomioides the right mantle fold, whichsecretes the cemented valve, is thicker and less well-developedthan the left. During the cementation process, the periostracumsecreted by the right fold is thinner and has a quilted appearance. Individuals of Myochama anomioides cement by their right
valveonce they have recahed a size of 1.23.9 mm. They appear
tohave a preference for attaching to the posterior portions ofa
diversity of living, shallow infaunal bivalves. The pronounced
stereotypicorientation they adopt suggests that these hosts are most
oftenalive at the time of colonization and that the mychamids benefit
fromthe relationship. The relationship, however, is not obligate.
Theyare capable of attaching to other shelly or rock debris, butdo
so at a lager size, presumaby whe the preferred substrataare not
available. The thin layer of extra-periostracal cementlacks the
calcereous crystalline nature of oyster cement, insteadof being
largely composed of organic material. This cement ispresumably
secreted by glands within the mantle, but these havenot been
identified. Indeed, the mantle lacks arenophilic glandswhich might
have been thought a suitable candidate for supplyingcement. (Received 14 December 1999; accepted 4 February 2000) 相似文献
503.
BRIAN A. GILBERT KENNETH J. RAEDEKE JOHN R. SKALSKI ANGELA B. STRINGER 《The Journal of wildlife management》2007,71(1):144-154
Abstract: We used cohort analysis to reconstruct the female segment of a Columbian black-tailed deer (Odocoileus hemionus columbianus) population from 1979 to 2000 in the western Cascades of Washington, USA. We used reconstructed population estimates and age class representations to analyze relationships between population change and female density, forage availability, and weather influences. We applied stage structured and unstructured modeling approaches and used information-theoretic methods to select the best models. We used habitat covariates to develop predictive functions for fertility and survival parameters in structured models. The best structured and unstructured models were composed of combinations of factors including population density, forage availability, and winter weather. Structured and unstructured models could assist with management of black-tailed deer by providing the ability to predict deer population change given covariate values. 相似文献
504.
BRIAN W. STAINES 《The Annals of applied biology》1977,87(3):495-512
Part of a red deer herd found on an estate in north-east Scotland in summer spent more time on neighbouring ground during the winter where they damaged farms and woods. Factors associated with the deer's seasonal distribution were studied to help understand how to keep more deer on the estate in winter. There were no indications that food species or food quality were responsible for the observed changes in deer distribution, or that other animals or disturbance influenced distribution over a long period. Deer sought shelter from chilling winds, and areas occupied by deer in winter had more sheltered ground from wind, and the quality of this shelter was higher than on the areas little used. Home-range behaviour and tradition appeared to determine which areas particular deer occupied in winter. The main recommendation for management was to re-open mature woodland to provide more and better shelter on the estate in order to get more control over the deer stock and to reduce marauding. 相似文献
505.
GREGORY D. EDGECOMBE BRIAN D. E. CHATTERTON 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1987,20(4):337-351
Divergence of Silurian encrinurine trilobite clades from common ancestry may be modelled as hetero-chronic pattern. Comparing ontogenies of ancestral late Ordovician Encrinuroides and the descendant punctarus and uariolaris plexi of Silurian Encrinurus provides a test of this hypothesis. Heterochrony in the punctarus plexus is dissociated with respect to entire organisms, but regionally global throughout cranidia (paedomorphic states) and pygidia (peramorphic states). Regulatory dissociation may explain the apomorphous enrollment strategy of this group. The uariolaris plexus, for which a growth series of Balizoma dimitroui (Perry & Chatterton) provides ontogenetic data, shows a complex of peramorphic cephalic character states. Changes in developmental timing thus provide a mechanism by which morphologic and ecologic divergence of closely-related clades was catalyzed in the Llandovery encrinurine radiation. Paedomorphic and dissociated Lineages of the odontopleurid Leonaspis provide a comparable example of divergent heterochronic pattern associated with coexisting (in the same biofacies) species of comparatively recent common ancestry. 相似文献
506.
BRIAN E. SHARP 《Ibis》1996,138(2):222-228
The number of days between ringing and recovery of oiled, cleaned and released seabirds was extremely low, usually a matter of a few days or weeks, and for three species was 5–100 times lower than for non-oiled birds. For oiled, cleaned Guillemots Una aalge , postrelease life expectancy was 9.6 days and long-term recovery rates were 10–20% of those of non-oiled birds. Measures of survival were not greater for oiled birds treated in recent years with modern methods. The cost and effectiveness of rehabilitation efforts for oiled seabirds need to be reexamined in the light of results showing low post-release survival. 相似文献
507.
BRIAN HETERICK 《Austral ecology》1997,22(2):218-221
Abstract Sampling of invertebrate fauna was carried out on Mt Coot-tha, between 25 February and 11 March 1992, to determine whether the presence of the coastal brown ant, Pheidole megacephala (Fabricius), affected die abundance and diversity of other invertebrates. Four plots were sampled; in two the coastal brown ant was present and in two it was absent. The overall abundance of invertebrates did not differ significantly between plots. The abundance of Collembola did vary significantly, but intraplot variability was large. Mite numbers did not differ significantly between plots, except for the family Laelapidae. Abundance of other ant species did not differ significantly between plots, but there was a difference in species composition; Dolichoderinae and Ponerinae were absent or poorly represented in plots where the coastal brown ant was present. 相似文献
508.
WILLIAM A. GAHL BRIAN POTTERF DONNA DURHAM-PIERRE MURRAY H. BRILLIANT VINCENT J. HEARING 《Pigment cell & melanoma research》1995,8(5):229-233
Tyrosine is the endogenous substrate for melanin production within melanosomes, but the method of tyrosine transport into the melanosome has not been investigated. In the mouse, melanogenesis is disrupted by mutations in the p gene resulting in the pink-eyed dilution phenotype; it has been suggested that the p gene codes for a tyrosine transport protein. We determined that normal (melan-a) melanosome-rich granular fractions take up 10 μm [3H]tyrosine at 21.1 ± 6.1 (SEM, standard error of the mean) pmol/min/mg protein (N=7) compared with 21.3 ± 5.8 SEM pmol/min/mg protein (N=5) for pink-eyed dilution, whose plasma membrane tyrosine transport was also normal (Km 89 μM; Vmax 302 pmol/min/mg cell protein). We also demonstrated that pink-eyed dilution melanosomes are immature by virtue of their low density, high hexosaminidase activity, and lack of pigment. These data indicate that a tyrosine transport system exists in the melanosomal membrane and that the p gene does not encode a tyrosine transporter of critical importance. 相似文献