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A Van Aerschot J Rozenski D Loakes N Pillet G Schepers P Herdewijn 《Nucleic acids research》1995,23(21):4363-4370
Acyclic nucleoside analogues with carboxamido- or nitro-substituted heterocyclic bases have been evaluated for their possible use as universal bases in oligodeoxynucleotides. The acyclic moiety endows the constructs with enough flexibility to allow good base stacking. The 5-nitroindazole analogue afforded the most stable duplexes among the acyclic derivatives with the least spread in Tm versus the four natural bases. In spite of the acyclic moiety, stabilities are comparable with those of duplexes incorporating the recently described 5-nitroindole nucleoside analogue, but considerably exceed those for the 3-nitropyrrole analogue. 相似文献
23.
The present report describes the bulk isolation of pluripotent stem cells (PSC) (assayed as day-9 CFU-S, colony-forming-units-spleen). As starting material, spleens, highly enriched with PSC, were used from mice that were bled and treated with thiamphenicol (TAP). In subjecting the spleen cells to a two-stage centrifugal elutriation procedure and a subsequent Percoll gradient centrifugation stage a 30-fold enrichment in the CFU-S concentration was achieved. The splenic PSC seeded with a characteristic low efficiency in the spleens of irradiated mice (f = 2%). Correcting the colony number for this, we obtained a cell mixture consisting of 88% PSC, contaminated with 4% committed precursor cells and about 10% ganuloid cells. 相似文献
24.
Kerstin Huss-Danell Wim Roelofsen Antoon D. L. Akkermans Piet Meijer 《Physiologia plantarum》1982,54(4):461-466
The occurrence and localization of enzymes involved in glycolysis, tricarboxylic acid cycle and glyoxylate cycle in root nodules of Alnus glutinosa (L.) Vill. and Hippophaë rhamnoides L. ssp. rhamnoides were studied. The following enzymes, catalyzing reversible steps in the glycolysis, were found in both the endophyte Frankia spp. and the plant cytosol of Alnus nodules: fructose-1,6-diphosphate aldolase, glyceralde-hyde-3-phosphate dehydrogenase, phosphoglycerate kinase and enolase. The enzymes catalyzing irreversible steps in glycolysis, viz. hexokinase and pyruvate kinase, were detectable only in the plant cytosol. Similar results were obtained with nodule homogenates of Hippophaë. This indicates the absence of a complete glycolysis in the endophyte. Vesicle clusters of the nodule endophyte of Alnus contained various dehydrogenases of the tricarboxylic acid cycle and showed activity of glutamate oxaloacetate transaminase. Respiration studies showed that vesicle clusters take up oxygen when supplied with NAD, glutamate and malate together. No oxygen uptake was found when any of these compounds was omitted. Vesicle clusters from both Alnus and Hippophaë nodules showed no detectable activity of the glyoxylate cycle enzymes isocitrate lyase and malate synthase. Since these enzymes are known to be present in Frankia Avcll, when grown in a medium with Tween 80 as carbon source, it is suggested that the glyoxylate cycle enzymes are repressed in the root-nodule symbioses. 相似文献
25.
Piet F. M. Verdonschot 《Hydrobiologia》1992,232(2):111-132
A survey was carried out at 157 sites, situated in pools and small lakes in the province of Overijssel (The Netherlands), to describe the macro-invertebrate community and their environment. A total of 61 environmental viriables was measured at each sampling site. The main aim was to described a regional ecological typology of ponds and small lakes. Multivariate analysis techniques are appropriate in data analysis for typological purposes. Different multivariate analysis techniques (FLEXCLUS, NODES, DCCA, PCA) were used in combination with ecological information on individual taxa to derive and describe site groups in terms of taxon composition and mean environmental conditions. The resulting site groups were termed cenotypes. Nine cenotypes were distinguished among the ponds and small lakes. The main differences between the cenotypes were related to duration of drought, acidity, morphology and nutrient load. In particular, the four cenotypes within the group of stagnant, pH-neutral ponds/lakes showed an overlap in taxon composition. These cenotypes represent a web-shaped continuum dominated by dimensions (relation of width to depth), nutrient load, and bottom composition (especially mesotrophic peat). The most important anthropogenic processes are acidification, eutrophication, and changes in the original hydrology. 相似文献
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Inge Santman-Berends Saskia Luttikholt René Van den Brom Gerdien Van Schaik Maaike Gonggrijp Han Hage Piet Vellema 《PloS one》2014,9(8)
The aim of this study was to estimate the quantity of antibiotics and classes of antibiotics used in the small ruminant industry in the Netherlands in 2011 and 2012. Twelve large veterinary practices, located throughout the Netherlands were selected for this study. All small ruminant farms associated with these practices that had complete records on the quantity of antibiotics prescribed were included. The veterinary practices provided data on all antibiotics prescribed, and the estimated animal used daily dose of antibiotics per year (AUDD/Y) was calculated for each farm. The median AUDD/Y in small ruminant farms was zero in both years (mean 0.60 in 2011, and 0.62 in 2012). The largest quantity of antibiotic use was observed in the professional goat industry (herds of ≥32 goats) with a median AUDD/Y of 1.22 in 2011 and 0.73 in 2012. In the professional sheep industry (flocks of ≥32 sheep), the median AUDD/Y was 0 in 2011 and 0.10 in 2012. In the small scale industry (flocks or herds of <32 sheep or goats), the median AUDD/Y never exceeded 0. The most frequently prescribed antibiotics in the small scale industry and professional sheep farms belonged to the penicillin class. In professional goat farms, antibiotics of the aminoglycoside class were most frequently prescribed. This study provides the first assessment on the quantity of antibiotic use in the small ruminant industry. Given a comparable attitude towards antibiotic use, these results might be valid for small ruminant populations in other north-western European countries as well. The antibiotic use in the small ruminant industry appeared to be low, and is expected to play a minor role in the development of antibiotic resistance. Nevertheless, several major zoonotic bacterial pathogens are associated with the small ruminant industry, and it remains important that antibiotics are used in a prudent way. 相似文献
28.
Marijn Bauters Sofie Meeus Matti Barthel Piet Stoffelen Hannes P. T. De Deurwaerder Flicien Meunier Travis W. Drake Quentin Ponette Jerme Ebuy Pieter Vermeir Hans Beeckman Francis wyffels Samuel Bod Hans Verbeeck Filip Vandelook Pascal Boeckx 《Global Change Biology》2020,26(8):4449-4461
Forests exhibit leaf‐ and ecosystem‐level responses to environmental changes. Specifically, rising carbon dioxide (CO2) levels over the past century are expected to have increased the intrinsic water‐use efficiency (iWUE) of tropical trees while the ecosystem is gradually pushed into progressive nutrient limitation. Due to the long‐term character of these changes, however, observational datasets to validate both paradigms are limited in space and time. In this study, we used a unique herbarium record to go back nearly a century and show that despite the rise in CO2 concentrations, iWUE has decreased in central African tropical trees in the Congo Basin. Although we find evidence that points to leaf‐level adaptation to increasing CO2—that is, increasing photosynthesis‐related nutrients and decreasing maximum stomatal conductance, a decrease in leaf δ13C clearly indicates a decreasing iWUE over time. Additionally, the stoichiometric carbon to nitrogen and nitrogen to phosphorus ratios in the leaves show no sign of progressive nutrient limitation as they have remained constant since 1938, which suggests that nutrients have not increasingly limited productivity in this biome. Altogether, the data suggest that other environmental factors, such as increasing temperature, might have negatively affected net photosynthesis and consequently downregulated the iWUE. Results from this study reveal that the second largest tropical forest on Earth has responded differently to recent environmental changes than expected, highlighting the need for further on‐ground monitoring in the Congo Basin. 相似文献
29.
María-Jesús Péarez-Péarez Bogdan Doboszewski Erik De Clercq P. Herdewijn 《Nucleosides, nucleotides & nucleic acids》2013,32(3-5):707-710
Abstract Adenine and thymine derivatives of 2′,3′-dideoxy-2′,3′-didehydropento-pyranosyl nucleosides carrying a phosphonomethyl moiety at their 4′-O-position and in a cis relationship with the heterocyclic base have been synthesized. 相似文献
30.
A. Van Aerschot C. Hendrix G. Schepers N. Pillet P. Herdewijn 《Nucleosides, nucleotides & nucleic acids》2013,32(3-5):1053-1056
Abstract Five acyclic nucleoside analogues with unnatural base moieties have been synthesized of which three successfully were incorporated into oligonucleotides. The acyclic analogue containing the base 5-nitroindazole was the least discriminating and should be further pursued for use as a universal nucleoside analogue. 相似文献