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511.
GEORGE G. BURBA DAYLE K. McDERMITT ACHIM GRELLE† DANIEL J. ANDERSON LIUKANG XU 《Global Change Biology》2008,14(8):1854-1876
There is a growing concern in the flux community that using the eddy covariance method with open‐path CO2 analyzers often leads to measurements of an apparent ecosystem CO2 uptake during off‐season periods, especially in cold climates. Such uptake has not been observed when measurements were made with closed‐path analyzers, chambers, or profile methods, suggesting it is an artifact due in some way to the use of open‐path analyzers. In this study, a series of laboratory tests and field experiments were conducted to determine the magnitude of the instrument surface heat exchange in the open path and its relationship with the measured CO2 flux. Results showed that (1) the surface of an open‐path instrument became substantially warmer than ambient due to electronics and radiation load during daytime, while at night, radiative cooling moderated temperature increases in the path; (2) high‐frequency temperature measurements inside the path were correlated with vertical wind speed producing sensible heat flux inside the instrument path exceeding the ambient heat flux by up to 14%; (3) enclosing the open‐path instrument eliminated the sensible heat flux in the path, and caused measured CO2 flux to match a closed‐path reference; (4) using sensible heat flux measured directly inside the open path in the WPL term instead of the ambient sensible heat flux also led to a match in CO2 flux between open‐path instrument and closed‐path reference; and (5) correcting previously collected open‐path CO2 flux data was possible by estimating the instrument heating effect with a semi‐empirical model using standard weather variables. Results showed that all proposed techniques led to a significant reduction in apparent CO2 uptake during off‐season periods and to a reduction of the underestimation of CO2 release in other periods. Close agreement between the open‐path measurements and closed‐path references was achieved in all cases. 相似文献
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Five new didymozoid trematodes are described from two species of platycephalid fish collected in Moreton Bay. Australia. Indodidymozoon moretonensis sp. n. from the buccal cavity and branchial arches and 1. suttiei sp. n. from the flesh are described from Platycephalus fuscus. Indodidymozoon lesteri sp. n. from the belly skin. I. pearsoni sp. n. from the eye, and Helicodidymozoon tortor gen. n., sp. n. from the buccal cavity. branchial arches and operculum are described from Platycephalus endrachtensis. The taxonomic composition of the genus Didymozoon is discussed. Five species. D. branchiale. D. brevicolle, D. koti, D. musculi and D. Platycephali are moved to Indodidymozoon ; the generic diagnosis of Indodidymozoon is revised. One species. D. spirale , and one species from Neometadidymozoon, N. helicis. are moved to the newly creeted Helicodidymozoon. Helicodidymozoon differs from Didymozoon, Indodidymozoon and metadidymozoon in the structure of the hindbody which is spirally twisted. 相似文献
518.
O. ROGER ANDERSON 《The Journal of eukaryotic microbiology》1994,41(2):124-128
ABSTRACT. Amoebae cultured from seawater collected at a coastal site near Barbados were largely a lobose amoeba with long tapered subpseudopodia identified as Vexillifera telmathalassa. Vexillifera telmathalassa occurs widely in marine environments and additional information is presented here on its fine structure, salinity tolerance, and feeding behavior toward clarification of its taxonomic characteristics and ecological niche. The amoebae were able to adjust to a gradual decline in salinity from 36‰ to 16‰, but at a salinity of 12‰. They all became immobilized and discoidal. The fine structure showed a centrally located nucleus (2.1 μ m) with a prominent nucleolus. The plasma membrane is coated with glycostyles 17 nm long and 14 nm apart, and may be derived from secretory vesicles with similar glycocalyx lining. Bacteria and occasional eukaryotic remains occur in digestive vacuoles or membrane-enclosed spaces. Some vacuoles (2.0–2.5 μ m) are filled with scattered masses of digested material and resemble the "glanzkörper" previously identified by light microscopy. In addition to bacterial prey, microflagellates were also ingested in laboratory culture as observed by light microscopy. Vexillifera telmathalassa may be more closely linked trophically to the microbial loop than previously recognized. 相似文献
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Abstract. Receptor neurones with high selectivity and sensitivity to plant odours were found within short sensilla trichodea on the antenna of both female and male Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) by using single-sensillum recording techniques. In 112 sensilla from females and forty-one from males, twenty-four different receptor neurone types were characterized according to their specificity. Altogether, twenty-six plant and three sex pheromone compounds were tested. Receptor neurones responding with high specificity to flower odours, green leaf volatiles, oviposition deterrents and other general host plant odours were identified. In twenty-one receptor neurone types, responses were elicited by one or several plant compounds, and in three types responses were elicited by sex pheromone compounds. The majority of the receptor neurones responded to only one or two of the tested compounds. In general, only one of the two receptor neurones in a sensillum responded to any of the compounds tested. An exception was a receptor neurone responding to plant odours (green leaf volatiles) and another receptor neurone responding to a sex pheromone compound ([Z]-7-dodecenyl (acetate), which occurred in the same sensillum. The majority of the receptor neurones displayed a high sensitivity to plant odours. No morphological difference was identified the different sensillum types. 相似文献
520.
Abstract. At 340–360 km North of the Arctic Circle in Norway, Hypoderma tarandi (L.) and Cephenemyia trompe (Modeer) females were caught in baited traps from 10 July to 21 August. During three summers, adverse climatic conditions inhibited flight activity of these oestrids on 56–68% of the days. Flies were not caught prior to or after these dates, nor at winds above 8 m/s, temperatures below 10C, light intensities below 20,000 lux, or during periods of rain or snow. C02 -baited insect flight traps caught significantly more H. tarandi females than non-baited traps. However, neither a white reindeer hide or reindeer interdigital pheromone glands enhanced the attraction of C02 to H. tarandi or C. trompe. Hypoderma tarandi females also were attracted to mobile people, but not to stationary individuals. There were no significant differences in the numbers of C.trompe or H.tarandi caught in C02 -baited traps in a birch/willow woods, on the treeless vidda (=tundra-like biome), or at woodsrvidda ecotone sites. Flies were caught in traps on days when the nearest reindeer herds were 25–100 km away. Significantly more H.tarandi and C.trompe were caught from 09.30 to 14.30 hours than from 14.30 to 19.30 hours; no flies were caught from 20.00 to 07.00 hours (Norwegian Standard Time = NST). Because COz -baited traps caught from hundreds to thousands of mosquitoes, blackflies and Culicoides midges, when climatic conditions inhibited oestrid activity, reindeer aggregations and movements attributed to insect attacks during warm sunny days may be largely in response to attacks by H.tarandi and C.trompe. 相似文献