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91.
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The taxonomic status of petrels from the North East Atlantic has long been a matter of debate. Breeding colonies of petrels occurring on the islands of Madeira, Bugio and Cape Verde were originally thought to be outlying populations of the polytypic species Pterodroma mollis . Subsequent taxonomic treatments have varied considerably in their classification of birds from these islands. The petrel populations on Madeira and Bugio represent some of Europe's rarest breeding birds and their exact species designation, and hence relation to conservation mandates, is a question of considerable importance. In this study we use molecular techniques alongside more traditional taxonomic characters to confirm the existence of two species of the genus Pterodroma in the Archipelago of Madeira. We also discuss identification of these species in the field and the implications for their conservation management. 相似文献
93.
BY A. d'A. BELLAIRS 《Journal of Zoology》1965,144(2):239-252
Six embryos of the eyed lizard ( Lacerta lepida ) with malformations such as short upper jaw, microphthalmia, abnormal fore-brain, cleft palate, absence or deficiency of the pituitary and tail defects are described. Embryos of the common lizard ( Lacerta vivipara ) and adder ( Vipera berus ) with microphthalmia and cleft palate, and of a sand lizard ( Lacerta agilis ) showing partial Siamese twinning are also reported. The aetiology of these malformations, and the well-known occurrence of similar conditions in birds and mammals, is discussed. 相似文献
94.
It has become common to distinguish between altruistic and commercial contract motherhood (or ‘surrogacy’). Altruistic arrangements are based on the ‘gift relationship’: a woman is motivated by altruism to have a baby for an infertile couple, who are free to reciprocate as they see fit. By contrast, in commercial arrangements both parties are motivated by personal gain to enter a legally enforceable agreement, which stipulates that the contract mother or ‘surrogate’ is to bear a child for the intending parents in exchange for a fee. She is required to undergo medical examinations and to refrain from behaviour that could harm the foetus. The intending parents are the child's legal parents from the outset. The parties to the contract can, but are not expected to, maintain contact after the transaction is completed. We argue that contract motherhood should not be organized according to the norms of the gift relationship, and that contract mothers should be compensated for their labour. However, we accept that there are good reasons for rejecting the commercial model as a suitable framework for contract pregnancy, and argue, instead, in favour of viewing it as a profession. 相似文献
95.
D. P. WHITFIELD ROBIN REID PAUL F. HAWORTH MIKE MADDERS MICK MARQUISS RUTH TINGAY & ALAN H. FIELDING 《Ibis》2009,151(2):255-264
Amongst raptor species, individuals with specialized diets are commonly observed to have higher reproductive output than those with general diets. A suggested cause is that foraging efficiency benefits accrue to diet specialists. This diet specificity hypothesis thus predicts that diet breadth and reproductive success should be inversely related within species. We highlight, however, that a prey availability hypothesis also makes the same prediction in some circumstances. Hence, when high diet specificity results from high encounter rates with an abundant, preferred prey, then prey availability may affect reproductive success, with diet specialization as an incidental correlate. Using three insular study areas in western Scotland, we examine diet specificity and reproductive success in Golden Eagles Aquila chrysaetos. Diet breadth and breeding productivity were not negatively related in any of our study areas, even though birds with specific diets did tend to have a higher incidence of preferred prey (grouse and lagomorphs) in the diet. Indeed, in two study areas there was evidence that diet generalists had higher breeding productivity. Our results therefore failed to support the diet specificity hypothesis but were consistent with the prey availability hypothesis. We highlight that although many other studies are superficially consistent with the diet specificity hypothesis, our study is not alone in failing to provide support and that the hypothesis does not provide a generic explanation for all relevant results. Diet specificity in predators can be at least partially a response to prey diversity, availability and distribution, and benefits associated with different prey types, so that being a generalist is not necessarily intrinsically disadvantageous. We suggest that the available evidence is more consistent with variation in prey abundance and availability as a more influential factor explaining spatial and temporal variation in breeding productivity of ‘generalist’ species such as the Golden Eagle. Under this argument, prey abundance and availability are the main drivers of variation in reproductive output. Diet specificity is a consequence of variation in prey availability, rather than a substantial cause of variation in reproductive success. 相似文献
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Remote sensing of sun-induced fluorescence to improve modeling of diurnal courses of gross primary production (GPP) 总被引:4,自引:0,他引:4
ALEXANDER DAMM JAN ELBERS† RÉ ERLER‡ BENIAMINO GIOLI§ KARIM HAMDI‡ RONALD HUTJES† MARTINA KOSVANCOVA¶ MICHELE MERONI FRANCO MIGLIETTA§ RÉ MOERSCH‡ JOSE MORENO ANKE SCHICKLING†† RUTH SONNENSCHEIN THOMAS UDELHOVEN‡‡ SEBASTIAN van der LINDEN PATRICK HOSTERT UWE RASCHER‡ 《Global Change Biology》2010,16(1):171-186
Terrestrial gross primary production (GPP) is an important parameter to explore and quantify carbon fixation by plant ecosystems at various scales. Remote sensing (RS) offers a unique possibility to investigate GPP in a spatially explicit fashion; however, budgeting of terrestrial carbon cycles based on this approach still remains uncertain. To improve calculations, spatio-temporal variability of GPP must be investigated in more detail on local and regional scales. The overarching goal of this study is to enhance our knowledge on how environmentally induced changes of photosynthetic light-use efficiency (LUE) are linked with optical RS parameters. Diurnal courses of sun-induced fluorescence yield ( F Syield ) and the photochemical reflectance index of corn were derived from high-resolution spectrometric measurements and their potential as proxies for LUE was investigated. GPP was modeled using Monteith's LUE-concept and optical-based GPP and LUE values were compared with synoptically acquired eddy covariance data. It is shown that the diurnal response of complex physiological regulation of photosynthesis can be tracked reliably with the sun-induced fluorescence. Considering structural and physiological effects, this research shows for the first time that including sun-induced fluorescence into modeling approaches improves their results in predicting diurnal courses of GPP. Our results support the hypothesis that air- or spaceborne quantification of sun-induced fluorescence yield may become a powerful tool to better understand spatio-temporal variations of fluorescence yield, photosynthetic efficiency and plant stress on a global scale. 相似文献
100.
Sporozoites of Mammalian Malaria: Attachment To, Interiorization and Fate Within Macrophages 总被引:8,自引:0,他引:8
HARRY D. DANFORTH MASAMICHI AIKAWA ALAN H. COCHRANE RUTH S. NUSSENZWEIG 《The Journal of eukaryotic microbiology》1980,27(2):193-202
Sporozoites of Plasmodium berghei and Plasmodium knowlesi, incubated in normal serum readily interact with peritoneal macrophages of mice or rhesus monkeys, respectively. Interiorization of the sporozoite requires that both serum and macrophages be obtained from an animal susceptible to infection by the malaria parasite. Serum requirements for sporozoite attachment to the macrophage are less specific. Phagocytosis is not essential for the parasites to become intracellular. Our findings indicate that active penetration of the sporozoites into the macrophages does occur. 相似文献