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121.
In deep water: a crinoid–brachiopod association in the Upper Oligocene of Antigua,West Indies 下载免费PDF全文
Stephen K. Donovan David A.T. Harper Roger W. Portell 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2015,48(3):291-298
Extant brachiopods and stalked crinoids are found together in the deeper waters of the Caribbean Sea. Analogous brachiopod/crinoid associations have been reported from diverse palaeoenvironments in the Neogene of the region. Studied examples include the Pleistocene of Jamaica (deeper water fore reef), and the Miocene of Jamaica (island slope chalks), Barbados (accretionary prism) and Carriacou (turbiditic siliciclastic shelf). Comparison with analogous modern environments indicates deposition in 150+m water depth. This association has now been extended back into the Late Oligocene. Crinoids and brachiopods both occur in the Antigua Formation of Antigua; both occur high in the formation, implying deeper water in this retrograde succession. They have received little attention from systematists, although the brachiopods Cistellarcula dubia Cooper and Tichosina foresti Cooper have previously been described from the Antigua Formation; to these, we add Cistellarcula sp., Argyrotheca sp. and Tichosina sp. At Half Moon Bay in southeast Antigua, high in the Antigua Formation, we have found columnals of isocrinid crinoids (cf. Isocrinus sp.) associated with rare brachiopods (Terebratulina sp.) in island slope deposits. These taxa provide independent evidence for the deeper water aspect of this part of the Antigua Formation, in beds that also yield large, thin‐walled fossil sponges. 相似文献
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Babot ED Rico A Rencoret J Kalum L Lund H Romero J del Río JC Martínez AT Gutiérrez A 《Bioresource technology》2011,102(12):6717-6722
The ability of two natural phenols to act as mediators of the recombinant Myceliophthora thermophila laccase (MtL) in eucalypt-pulp delignification was investigated. After alkaline peroxide extraction, the properties of the enzymatically-treated pulps improved with respect to the control. The pulp brightness increased (3.1 points) after the enzymatic treatment with MtL alone, but the highest improvements were obtained after the MtL treatment using syringaldehyde (4.7 points) and especially methyl syringate (8.3 points) as mediators. Likewise, a decrease in kappa number up to 2.7 points was obtained after the MtL-methyl syringate treatment, followed by decreases of 1.4 and 0.9 points after the treatments with MtL-syringaldehyde and MtL alone, respectively. On the other hand, removal of the main lipophilic extractives present in eucalypt pulp was observed after the above laccase-mediator treatments. Finally, the doses of both MtL and methyl syringate were reduced, and results compatible with industrial implementation were obtained. 相似文献
124.
R.G. Roberts K.E. Westaway J.-x. Zhao M.I. Bird W.J. Rink 《Journal of human evolution》2009,57(5):484-502
A robust timeframe for the extant cave deposits at Liang Bua, and for the river terraces in the adjoining Wae Racang valley, is essential to constrain the period of existence and time of extinction of Homo floresiensis and other biota that have been excavated at this hominin type locality. Reliable age control is also required for the variety of artifacts excavated from these deposits, and to assist in environmental reconstructions for this river valley and for the region more broadly. In this paper, we summarize the available geochronological information for Liang Bua and its immediate environs, obtained using seven numerical-age methods: radiocarbon, thermoluminescence, optically- and infrared-stimulated luminescence (collectively known as optical dating), uranium-series, electron spin resonance, and coupled electron spin resonance/uranium-series. We synthesize the large number of numerical age determinations reported previously and present additional age estimates germane to questions of hominin evolution and extinction. 相似文献
125.
The Permian–Triassic boundary and basal Triassic shallow-marine successions were studied and correlated in sections of two
structural units in Hungary (Transdanubian Range and Bükk units). Core sections in the Transdanubian Range unit recovered
inner ramp deposits whereas outcrops in the Bükk unit expose deposits of the deeper ramp area of the western Tethys. The inner
ramp section (studied ca. 10 m in thickness) is characterized by a succession of dolomites overlain by bioclastic limestones,
peloidal grainstones (which recorded the biotic decline) and oolites with finely crystalline limestone interlayers. The deeper
ramp section (studied ca. 15 m in thickness) is characterized by a succession of bioclastic limestones and marlstones, mudstone
beds (recording the first biotic decline), the ‘boundary shales’ (recording the second biotic decline and the stable carbon
isotope marker), mudstones with wackestone laminae, and stromatolite boundstones. Accordingly, oolite formation and microbial
micrite precipitation represent carbonate sedimentary responses of end-Permian mass extinction on the carbonate shelf. In
both successions, mudstones predominate the upsection, suggesting a relative sea-level rise. The succession of the deep ramp
area exhibits a continuous sediment accumulation and the diagenesis here was influenced by marine and marine-derived pore
water. The δ13C curve shows a continuous change towards more negative values, starting in bioclastic limestones, followed by a sharp symmetric
negative peak at the second biotic decline that is a chemostratigraphic marker of the boundary event. Facies and microfacies
trend of the inner ramp carbonates in the Transdanubian Range unit exhibits close similarities to that found in many South
Alpine sections. Relict peloidal deposits, formed cemented submarine hardground substrate, indicate the extinction level.
Sedimentary and diagenetic features of the overlying oolite bedset revealed slightly different depositional environments in
the two studied Transdanubian Range unit sections. Petrography of the oolites highlighted shallow burial diagenetic alterations
which includes marine cementation, marine-burial replacement and dolomitization. A lack of the specific negative peak in the
δ13C values is most likely due to the multiple redeposition events of the sedimentary grains. This led to the conclusion that
the deeper ramp deposits (e.g., in Bükk unit) have greater potential for recognizing trends in processes, affecting the marine
environments and related to the end-Permian mass extinction, at the western Tethys. 相似文献
126.
We assessed the effect of two pathogens (myxoma virus and Eimeria stiedae) and five macroparasites (gastrointestinal helminth species) of the wild rabbit (Oryctolagus cuniculus) upon total host body mass and abdominal fat level. Additionally, we assessed the effects of these organisms on the number of foetuses in adult females during the peak breeding period. Both mass of abdominal fat and total body mass of the rabbit were negatively associated with myxoma virus infection and increasing helminth species richness. Total body mass was also negatively associated with the protozoan parasite E. steidae. No relationship was found between any of the parasites/pathogens and the number of foetuses in adult females, although only relatively small sample sizes were available for this section of the analysis. Increasing host body mass was positively associated with number of foetuses and we propose that mass reduction caused by the pathogen and parasite species could also have the consequence of reducing foetal number. 相似文献
127.
128.
Ana Paula Zanatta Renata Gonçalves Leila Zanatta Geisel Túlio de Oliveria Ana Luiza Ludwig Moraes Ariane Zamoner Víctor Fernández-Dueñas Débora Lanznaster Francisco Ciruela Carla Inês Tasca Christelle Delalande Danusa Menegaz Fátima Regina Mena Barreto Silva 《生物化学与生物物理学报:生物膜》2019,1861(4):748-759
The functions of Sertoli cells, which structurally and functionally support ongoing spermatogenesis, are effectively modulated by thyroid hormones, amongst other molecules. We investigated the mechanism of action of rT3 on calcium (45Ca2+) uptake in Sertoli cells by means of in vitro acute incubation. In addition, we performed electrophysiological recordings of potassium efflux in order to understand the cell repolarization, coupled to the calcium uptake triggered by rT3. Our results indicate that rT3 induces nongenomic responses, as a rapid activation of whole-cell potassium currents in response to rT3 occurred in <5 min in Sertoli cells. In addition, the rT3 metabolite, T2, also exerted a rapid effect on calcium uptake in immature rat testis and in Sertoli cells. rT3 also modulated calcium uptake, which occurred within seconds via the action of selective ionic channels and the Na+/K+ ATPase pump. The rapid response of rT3 is essentially triggered by calcium uptake and cell repolarization, which appear to mediate the secretory functions of Sertoli cells. 相似文献
129.
Van Belleghem F Cuypers A Semane B Smeets K Vangronsveld J d'Haen J Valcke R 《The New phytologist》2007,173(3):495-508
We examined the subcellular cadmium (Cd) localization in roots and leaves of wild-type Arabidopsis thaliana (ecotype Columbia) exposed to environmentally relevant Cd concentrations. Energy-dispersive X-ray microanalysis (EDXMA) was performed on high-pressure frozen and freeze-substituted tissues. In the root cortex, Cd was associated with phosphorus (Cd/P) in the apoplast and sulfur (Cd/S) in the symplast, suggesting phosphate and phytochelatin sequestration, respectively. In the endodermis, sequestration of Cd/S was present as fine granular deposits in the vacuole and as large granular deposits in the cytoplasm. In the central cylinder, symplastic accumulation followed a distinct pattern illustrating the importance of passage cells for the uptake of Cd. In the apoplast, a shift of Cd/S granular deposits from the middle lamella towards the plasmalemma was observed. Large amounts of precipitated Cd in the phloem suggest retranslocation from the shoot. In leaves, Cd was detected in tracheids but not in the mesophyll tissue. Extensive symplastic and apoplastic sequestration in the root parenchyma combined with retranslocation via the phloem confirms the excluder strategy of Arabidopsis thaliana. 相似文献
130.