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121.
ROY AB 《Biochimica et biophysica acta》1958,29(1):193-201
122.
123.
ROY AB 《Biochimica et biophysica acta》1954,13(2):300-301
124.
Leverage, local influence and curvature in nonlinear regression 总被引:1,自引:0,他引:1
125.
The Juan Fernandez Firecrown Sephanoides fernandensis is an endangered endemic hummingbird that inhabits the Juan Fernandez Islands, 667 km off the coast of Chile. Its population has decreased from several thousand in the early part of this century to approximately 250–400 individuals at present. The reasons for its decline include habitat degradation by anthropogenic forest clearance and the introduction of grazing mammals and rodents. Another hummingbird, the Green-backed Firecrown Sephanoides sephaniodes, inhabits the Juan Fernandez Islands but is also found on the Chilean mainland. It currently numbers several thousand on the Juan Fernandez Islands but was considered rare during the late 19th and early 20th centuries. The sister relationship between the two species has not been critically tested, and so their evolutionary histories on the Juan Fernandez Islands remain uncertain. With the use of mtDNA cytochrome b and ND2 phylogenetic reconstructions, our study supports the two species as sister taxa. Moreover, the molecular data suggest that the genus Sephanoides is closely related to the higher altitude Andean hummingbirds typical of the paramo and puna habitats. The molecular divergence between the two species of Sephanoides indicates they may have become isolated from each other less than 1 million years ago, suggesting that S. fernandensis evolved in situ on the Juan Fernandez Islands. We find no evidence of genetic subdivision between populations of S. sephaniodes from the Juan Fernandez Islands and the mainland. In addition, high genetic variation of the Juan Fernandez Islands population does not indicate a long period of isolation of a limited number of S. sephaniodes but instead suggests a recent colonization event, perhaps from several mainland populations. As a result of molecular, morphological and apparent ecological similarities, we suggest that competition by S. sephaniodes may be an additional factor stifling the recovery of S. fernandensis. Possible conservation strategies include habitat restoration and the removal of introduced mammals; immediate implementation of such conservation management plans are necessary to save this species from extinction. 相似文献
126.
PAUL A. ROCHELLE DONNA M. FERGUSON TROY J. HANDOJO RICARDO DE LEON MIC H. STEWART ROY L. WOLFE 《The Journal of eukaryotic microbiology》1996,43(5):72S-72S
A detection, viability, and infectivity assay was developed for Cryptosporidiurn parvum. Oocysts or excysted sporozoites were inoculated onto monolayers of CaCo-2 cells grown on chamber slides. C. parvum infection was monitored by three methods: a) application of a fluorescein-labeled anti-sporozoite antibody; b) PCR of a heat-shock protein gene fragment; and c) detection of mRNA from the heat-shock protein gene by RT-PCR. 相似文献
127.
Bark banding of morphaction is an effective means of controling stem elongation in Pinus radiata D. Don (Monterey pine) but not Juglans regia L. (English walnut). Diffusion coefficients of 14C-labeled morphactin across excised disks of tree bark, measured in specially designed diffusion chambers, were 11 to 85 fold greater in pine than walnut. In seedlings of comparable age, the suberin layer of walnut bark is much thicker than that of pine; if the layer is removed, diffusion of 14C-morphactin is enhanced 39-fold in pine and 285-fold in walnut. Morphactin applied to the bark as an ester is rapidly hydrolyzed to its carboxylic acid derivative in both pine and walnut. This conversion occurs rapidly in the bark of both species and does not appear to limit the rate of morphactin movement across the bark. These results suggest that diffusion across the suberin layer and not metabolism limits morphactin transport across the bark. 相似文献
128.
LIEBERBURG IVAN; MACLUSKY NEIL J.; ROY EDWARD J.; MCEWEN BRUCE S. 《Integrative and comparative biology》1978,18(3):539-544
Many sex differences in the regulation of reproductive functionin rats are the result of a differentiation of the brain whichoccurs neonatally. Although injections of either androgens orestrogens are capable during the neonatal period of alteringhypothalamic systems involved in reproductive behavior and gonadotropinregulation, the physiological role of each type of hormone hasnot been clearly established. In both sexes, circulating estrogensare normally kept from interacting with estrogen receptors inthe limbic brain by the high levels of alpha-fetoprotein inthe blood. The local aromatization of androgens in the braincould circumvent alpha-fetoprotein, since androgens do not bindto this serum protein. The "paromatization hypothesis" statesthat testosterone, which is abundant in neonatal male circulationbut absent in females, is locally converted to estradiol inthe limbic brain. There it binds to estrogen receptor proteinsto produce tissue differentiation. The ontogeny of estradiolbinding proteins in limbic areas is consistent with the aromatizationhypothesis, with a rapid increase in receptor levels occurringshortly after birth. Also, the presence of endogenous estradiol-receptorcomplexes has been demonstrated in the cell nuclei of male neonatesbut not female neonales. Furthermore, the presence of estradiolbinding proteins in other regions of the neonatal male and femalebrain suggests an additional role of estradiol. unknown as ofyet. Several studies with agents which block the aromatizationof androgens to estrogens or the binding of estrogens to theirreceptors are consistent with the aromatization hypothesis,since these agents prevent the differentiation of intact neonatalmales. However, specific androgen binding proteins are alsopresent in neonatal brains, and androgen-receptor complexescan be found in cell nuclei of neonates after an injection oftritiated androgen. The possible involvement of these receptorsin sexual differentiation of the brain is suggested by the findingthat an antiandrogen inhibits both the binding of androgens(but not estrogens) and the differentiation of males. 相似文献
129.
BISWENDU B. GOSWAMI SYAMALIMA DUBE PRABIR BHATTACHARYYA SANDIP N. SINHA BIMAL K. RAY D. K. DUBE S. C. ROY 《Physiologia plantarum》1975,35(2):111-114
Proteins synthesized in vitro by mitochondria isolated from 48-h germinating seeds of Vigna sinensis (L.) Savi and incubated in the presence of 14C-labelled amino acids from Chlorella protein hydrolysate, have been found associated with nine products separable by acrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. Cytoplasmic contribution to these products was practically eliminated by the use of cycloheximide. Most of the radioactivity was incorporated into proteins having molecular weights between 10,000 and 65,000 as determined by comparing their electrophoretic mobilities with those of standard, reference proteins. 相似文献
130.
Nitrogen Metabolism in the Terrestrial Isopod, Oniscus asellus 总被引:2,自引:0,他引:2
The total diffusible content of ammonia in Oniscus asellus wasmeasured as 1.20 mg % body fluid. Daily excretions of ammoniaexceeded the total diffusible content in measurements on specimenstaken directly from nature. The content of uric acid in a groupof 35 specimens was 11.3 mg % body weight and 93% of this materialwas in the body wall. Urea was not measurable under conditionsthat would have allowed detection of at least 0.26 mg % bodyfluid. Only arginase of the enzymes in the ornithine-urea cycle wasmeasurable. Labeled urea was not detectable in aqueous extractsunder conditions where approximately 50,300 CPM of labeled carbonwas incorporated into metabolites. Labeled arginine was notdetectable under conditions where 9,100 CPM of KHC14O3 wereincorporated into the soluble protein fraction and more than3,340,000 CPM were incorporated into particulate protein andnon-protein fractions of the organism. All of the enzymes of uricolysis to ammonia were present, uricaseand urease being rate-limiting. Uricase was measurable as myeloperoxidase.Although high rates of glutamate-oxalacetate aminotransferaseand glutamate-pyruvate aminotransferase were readily measured,glutamic dehydrogenase activity proceeded slowly, suggestingsynthesis of needed amino acids as the key function of the transaminaseactivities. Amino acid oxidase activities, glutaminase, and asparaginaseactivities were low, too, whereas peroxidatic deaminase activitiesproceeded at rates sufficiently fast to account for the levelsof volatile ammonia emitted in vivo. Although molting may serve for excretion of end-products ofpurine catabolism, no central organ homologous to kidney orliver appears to be present with respect to detoxication orexcretion of ammonia. Inasmuch as O. asellus is not exposed to osmotic stresses, doesnot ordinarily face problems of dehydration, and tolerates levelsof ammonia generally ascribed as toxic to other organisms, itis proposed that retention of ammonotelism probably offers thermodynamicadvantages to the organism. The evolution of a system whereinammonia is excreted as a gas may have provided the organismwith an adaptive mechanism for colonizing land. 相似文献