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51.
THE FINE STRUCTURE OF THE ABDOMINAL SENSE ORGANS OF PTERIOMORPHA (MOLLUSCA, BIVALVIA) 总被引:1,自引:0,他引:1
An ultrastructural study of the abdominal sense organs (ASO)of nine species, representing all three groups Of Pteriomorpha(Mytilina, Arcina, Pteriina), is offered. In all species investigated the sensory epithelium is high (40130µm) and possesses two predominant cell types: (a) electron-densesupporting cells with microvilli only, pigment granules, andoval distal nuclei; (b) sensory cells with round proximal nucleiand electron-lucent plasma. Their narrow processes, always bunched,reach the surface bearing long (100300 µm) stiffcilia. Each cilium has a polarized, orientated basal foot andseveral strong roots and is surrounded by nine specialized "stereo-microvilli"forming a basal plate in connexion with the basal body. Basalcontact of the sensory cells with nervous tissue proves theirreceptive nature. Structural uniformity as well as identical innervation provideevidence for the homology of the ASO in all Pteriomorpha. Thereis no homology between sensory cells and the similar, so-called"choanocyte-like cells". 相似文献
52.
Repellent effects of pongam oil on settlement and oviposition of the common greenhouse whitefly Trialeurodes vaporariorum on chrysanthemum 总被引:2,自引:0,他引:2
ROMAN PAVELA GERHARD HERDA 《Insect Science》2007,14(3):219-224
The repellent activities, including host deterrence and anti-oviposion, of pongam oil against the adults of the common greenhouse whitefly Trialeurodes vaporariorum Westwood in greenhouses were tested. Chrysanthemum plants treated with different concentrations (0.5%-2.0%) of water-suspended pongam oil showed relatively long-lasting host deterrent and anti-oviposition effects on the adults of greenhouse whitefly. Although the repellent effect declined in time and concentration, strong effects on the reduction of oviposition were found, which lasts, dependent on concentration at least 12 days after application. 相似文献
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Survival and development of five species of cyclopoid copepods in relation to food supply: experiments with algal food in a flow-through system 总被引:2,自引:0,他引:2
1. Cyclops spp. generally develop and grow during favourable food conditions in spring and undergo a diapause in summer, while Acanthocyclops robustus, Mesocyclops leuckarti and Thermocyclops crassus develop and grow in summer when they face poorer food conditions and more competition from Cladocera. Since nauplii are the bottleneck in copepod development, we tested the hypothesis that Cyclops abyssorum and C. vicinus nauplii have higher food requirements for survival and development than the nauplii of A. robustus, M. leuckarti and T. crassus. We also tested survivorship and development from hatching to adulthood. 2. Survivorship and development of the copepods was studied in a flow‐through system using five concentrations of the phytoflagellate Chlamydomonas reinhardtii in the range from 1 × 104 to 4.5 × 105 cells mL?1 (approximately 0.5–22.5 mg C L?1). 3. Nauplii of both species of Cyclops died at intermediate to low (C. abyssorum) and low (C. vicinus) food concentrations, while nauplii of A. robustus, M. leuckarti and T. crassus survived at all concentrations. 4. The negative effects of low food concentration were also reflected in development. In C. abyssorum and C. vicinus, development duration increased at low food concentration while development was much less affected in A. robustus and T. crassus. Mesocyclops leuckarti was intermediate between Cyclops spp. and A. robustus/T. crassus, with an increase in development duration at the lowest food concentration. 5. Our results support the hypothesis that summer diapause in Cyclops spp. has developed as a strategy to avoid a food bottleneck for nauplii. 相似文献
55.
STEFANIE DANIELA GOLDBERG KLAUS-HOLGER KNORR† CHRISTIAN BLODAU† GUNNAR LISCHEID‡ GERHARD GEBAUER 《Global Change Biology》2010,16(1):220-233
The impact of experimentally intensified summer drought and precipitation on N2O and NO turnover and fluxes was investigated in a minerotrophic fen over a 2‐year period. On three treatment plots, drought was induced for 6 and 10 weeks by means of roofs and drainage and decreased water table levels by 0.1–0.3 m compared with three nonmanipulated control plots. When averaged over the three treatment plots, both N2O and NO emission showed only little response to the drought. On the single plot scale, however, a clear impact of the treatment on N2O and NO fluxes could be identified. On the plot with the weakest water table reduction hardly any response could be observed, while on the plot with the greatest drainage effect, N2O and NO fluxes increased by 530% and 270%, respectively. Rewetting reduced NO emissions to background levels (0.05–0.15 μmol m?2 h?1), but heavily enhanced N2O emission (18–36 μmol m?2 h?1) for several days in the plots with largest water table reduction. These peaks contributed up to 40% to the cumulative N2O fluxes and were caused by rapid N2O production according to isotope abundance data. According to N2O concentrations and isotope abundance analysis N2O was mostly produced at depths between 0.3 and 0.5 m. During water table reduction net N2O production in 0.1 m depth steadily increased in the most effectively dried plot from 2 up to 44 pmol cm?3 day?1. Rewetting immediately increased net N2O production in the topsoil of the drought plots, showing rates of 18–174 pmol cm?3 day?1. This study demonstrates that drought and rewetting can temporarily increase N2O emission to levels that have to date only been reported from nutrient rich and degraded fens that have been drained for agricultural purposes. 相似文献
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A new genus of anascan lunulitiform bryozoan, Pseudolunularia . is introduced for two new species, P. enigma and P. unguis . It is inferred that live colonies both possess basal rhizoids and are supported and stabilized by elongate avicularian mandibles. The autozooids, brooding zooids and avicularia of both species bear a striking resemblance to a parallel pair of species belonging to the genus Lunularia, L. repandus and L. cupulus . 相似文献
58.
GERHARD MAIER 《Freshwater Biology》1994,31(1):77-86
- 1 Life history characters (body size of adults, egg diameter, egg sac length and breadth) of nineteen species of central European cyclopoid copepods were measured and sexual size dimorphism (adult female length x adult male length?1), relative egg size (egg weight X body weight?1), weight of adult females and of eggs, egg sac shape (egg sac length x egg sac breadth?1), and reproductive effort (clutch weight produced per female weight per day) were calculated to detect trends in life history strategies.
- 2 Typical planktonic species exhibited the lowest reproductive effort. Among planktonic species, the value for egg sac shape increased with clutch size.
- 3 Large species and small species exhibited different trends in life history characters. Large species had larger clutches, larger eggs, and a greater sex size dimorphism than small species. However, small species had a greater relative egg size.
- 4 Large species live in cold water and reproduce during the spring bloom of phytoplankton where the production of large clutches with relatively small eggs is advantageous. Reserves are unnecessary for juveniles because food is abundant. Small species generally are most abundant during the warm season, when conditions are less predictable, and relatively large eggs, possibly provided with reserves, are advantageous.
59.
GERHARD H. BUCK-SORLIN ADRIAN D. BELL 《Botanical journal of the Linnean Society. Linnean Society of London》1998,127(4):371-391
Almost 37 000 fragments (twigs, peduncles, inflorescences) were shed from a single mature oak tree over one year. Shedding showed strong seasonality with abrupt peaks in June and October, yet only weak correlations to weather parameters. The majority of shed twigs were short shoots, consisting of one or few extension units, which were not older than two years. In many twigs, shedding was preceded by the outgrowth of the terminal bud into either a male inflorescence or a defective extension unit. The large majority of shed twigs belong to a category of summer annual and biannual deciduous short shoots of an exploitative nature, only a minority are explorative long shoots. Implications for the architecture of the tree crown are that twigs of higher branching order are mostly affected by shedding, as they consist of short modules which exhibit a high proportion of flower buds. 相似文献
60.
CLAUDIA HEMP KLAUS‐GERHARD HELLER SIEGFRIED KEHL ELŻBIETA WARCHAłOWSKA‐ŚLIWA JOHANN WOLFGANG WÄGELE ANDREAS HEMP 《Systematic Entomology》2010,35(3):554-580
The tettigoniid genus Phlesirtes Bolivar and its allies are reviewed. Morphological, ecological and molecular data prompt the erection of the new genus Chortoscirtes gen.n. with type species Xiphidion meruense Sjöstedt. The genera Phlesirtes, Chortoscirtes, Karniella and Naskreckiella are characterized by morphological characters supported by molecular, acoustic, ecological and chromosomal data. Four species, Chortoscirtes pseudomeruensis sp.n. , C. masaicus sp.n. , C. puguensis sp.n. and C. serengeti sp.n. , are described from localities in northern and coastal Tanzania and one Karniella, K. crassicerca sp.n. , is described from Uganda. The following comb n. are proposed: Phlesirtes kibonotensis (Sjöstedt) and Phlesirtes kilimandjaricus (Sjöstedt). Subtribal status is proposed for the four investigated African genera. A key to the Chortoscirtes species is provided. 相似文献