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81.
Kjell Sjöberg Gunnar Gunnarsson Hannu Pöysä Johan Elmberg Petri Nummi 《European Journal of Wildlife Research》2011,57(3):505-516
Two main hypotheses proposed to explain the seasonal decline in reproductive performance in birds are (1) deterioration of
environmental conditions and (2) lower parental quality of late breeders. Previous experimental work addressing these hypotheses
generally have problematic biases pertaining to delay of hatching, costs of re-laying and incubation, as well as variation
in the quality of eggs, territories, offspring and parental traits. We address these biases in an experimental test of the
timing hypothesis (i.e. (1) above) in a precocial bird. Using a 2-year cross-over design and game-farm mallard (Anas platyrhynchos) eggs originating from a number of hens and a standardised delay procedure, we introduced early and late broods with a foster
female onto boreal oligotrophic lakes and monitored subsequent duckling survival. Standardised invertebrate sampling was done
concurrently to get a measure of lake-level abundance of aquatic prey, a likely causative agent of putative seasonal difference
in duckling survival. Survival data and covariates (duckling age; days) were analysed by an information theoretic approach.
There was no effect of treatment (i.e. manipulation of hatching date) on duckling survival, which was higher in 2005 than
in 2004. In contrast to observational studies from more seasonal wetlands, our experiment demonstrates that duckling survival
on boreal lakes was not affected by a 12-day delay in hatching date. Since we did not find any consistent trends in abundance
of aquatic prey, i.e. neither clear peaks nor differences between treatment periods, we hypothesise that moderate climate
change has minor effects on resource abundance and hence also on mallard duckling survival in boreal environments. 相似文献
82.
83.
Diversity of airborne bacteria in samples collected using different devices for aerosol collection 总被引:2,自引:0,他引:2
Camilla Fahlgren Gunnar Bratbak Ruth-Anne Sandaa Runar Thyrhaug Ulla Li Zweifel 《Aerobiologia》2011,27(2):107-120
Bacteria are ubiquitous in the atmosphere, where they form a highly diverse community, albeit low in abundance. Several approaches
are available for collecting airborne particles, though few comparative studies have been conducted to date. This study examined
how different sampling strategies affect the apparent composition of the airborne community. Three devices were tested: an
impactor, a liquid impinger, and a Teflon membrane filter. Comparative studies were conducted at one mountainous location
in Norway and one seaside location in Sweden. At both locations, microbial samples were collected in parallel using the sampling
devices. DNA extraction, construction of 16S rRNA gene clone libraries, and subsequent sequencing were used to identify the
bacteria. The comparison between clone libraries retrieved using the different devices indicated good agreement regarding
dominant species, overall diversity, and distribution of species among phylogenetic groups. Among the less common species,
there were few shared sequences in different clone libraries, likely due to the high diversity of the assessed samples. Bacteria
belonging to the Bacteroidetes and Proteobacteria phyla dominated at both locations, and the most common genera were Sphingomonas sp. and Pantoea sp. Chloroplast-like 16S rRNA gene sequences were detected in all samples. 相似文献
84.
Forty-six volatile compounds were identified in the secretions from Dufour's gland of worker ants of the species Formica nigricans, F. rufa, and F. polyctena using combined gas chromatography-mass spectrometry and capillary gas chromatography. In both methods the natural volatile material has been driven off excised glands using a precolumn technique.The composition of the secretions from the three species are very similar but there are also some distinct differences, especially between F. nigricans on the one hand and F. rufa and F. polyctena on the other. Straight-chain, saturated hydrocarbons are the quantitatively dominating compounds, with undecane as the largest individual component, followed by tridecane, pentadecane, and heptadecane. Straight-chain, monounsaturated hydrocarbons and methyl-branched, saturated hydrocarbons are also present and a few straight-chain, doubly unsaturated hydrocarbons are present in trace amounts.In the region of lower volatility two isoprenoids identified as all-trans-geranylgeraniol and the corresponding acetate all-trans-geranylgeranyl acetate, have been found together with octadecyl acetate. The relative amounts between these compounds are the main difference between the secretions from the three species. Octadecyl acetate is thus present only in trace amounts in the secretion of F. nigricans.In addition to the compounds mentioned a few aliphatic acetates and alcohols present in small amounts have been identified.The secretions are thought to have many functions which are reflected in their complex composition. This is discussed in comparison with results from other formicine ants. The species specificity in the composition of the secretion from Dufour's gland and the taxonomic value of this specificity are also discussed. 相似文献
85.
86.
The pH Dependency of Relative Ion Permeabilities in the Crayfish Giant Axon 总被引:2,自引:0,他引:2 下载免费PDF全文
The dependence of the membrane potential on potassium, chloride, and sodium ions, was determined at the pH's of 6.0, 7.5, and 9.0 for the resting and depolarized crayfish ventral nerve cord giant axon. In normal saline (external potassium = 5.4 mM), the dependence of the membrane potential on the external potassium ions decreased with lowered pH while that for chloride increased. In contrast, in the potassium depolarized axon (external potassium = 25 mM), the dependence of the membrane potential on external potassium was minimum around pH 7.5 and increased in either more acidic or basic pH. In addition, the dependence of the membrane potential on external chloride in the depolarized axon was maximum at pH 7.5 and decreased in either more acidic or basic pH. The sodium dependency of the membrane potential was small and relatively unaffected by pH or depolarization. The data are interpreted as indicating a reversible surface membrane protein-phospholipid conformation change which occurs in the transition from the resting to the depolarized axon. 相似文献
87.
Abstract: The nature of [3 H]imipramine binding to human platelets was investigated. Desipramine and 5-hydroxytryptamine (5-HT) displaced the same amount of binding and the binding was sensitive to protease treatment. The nature of pharmacological inhibition of [3 H]imipramine binding was investigated in saturation experiments. Increases in K d without changes in B max were noted with the addition of 5-HT, desipramine, norzimeldine, or 5-methoxytryptoline. Reductions in B max without alterations in K D were obtained when citalopram or clomipramine was added. It is concluded that the [3 H]imipramine binding site in human platelets is of protein nature and that this binding site contains the substrate recognition site for 5-HT uptake. In addition, [3 H]imipramine and other 5-HT uptake inhibitors have bonds to other parts of the 5-HT uptake carrier or to the surrounding lipid membrane. This additional binding outside the substrate recognition site is not one single site but most likely represents sites that are specific for the chemical structure of each uptake inhibitor, respectively. 相似文献
88.
Ingo?Appelhagen Katharina?Thiedig Niclas?Nordholt Nina?Schmidt Gunnar?Huep Martin?Sagasser Bernd?WeisshaarEmail author 《Planta》2014,240(5):955-970
Main conclusion
We present a comprehensive overview on flavonoid-related phenotypes of A. thaliana tt and tds mutants, provide tools for their characterisation, increase the number of available alleles and demonstrate that tds3 is allelic to tt12 and tds5 to aha10.Flavonoid biosynthesis is one of the best-studied secondary metabolite pathways in plants. In the model system Arabidopsis thaliana it leads to the synthesis of three phenolic compound classes: flavonol glycosides, anthocyanins and proanthocyanidins (PAs). PAs appear brown in their oxidised polymeric forms, and most A. thaliana mutants impaired in flavonoid accumulation were identified through screens for lack of this seed coat pigmentation. These mutants are referred to as transparent testa (tt) or tannin-deficient seed (tds). More than 20 mutants of these types have been published, probably representing most of the genes relevant for PA accumulation in A. thaliana. However, data about the genes involved in PA deposition or oxidation are still rather scarce. Also, for some of the known mutants it is unclear if they represent additional loci or if they are allelic to known genes. For the present study, we have performed a systematic phenotypic characterisation of almost all available tt and tds mutants and built a collection of mutants in the genetic background of the accession Columbia to minimise effects arising from ecotype variation. We have identified a novel tt6 allele from a forward genetic screen and demonstrated that tds3 is allelic to tt12 and tds5 to aha10.89.
Matthias Kott Gunnar Elke Maike Reinicke Supandi Winoto-Morbach Dirk Sch?dler Günther Zick Inéz Frerichs Norbert Weiler Stefan Schütze 《PloS one》2014,9(11)
Introduction
Acid sphingomyelinase is involved in lipid signalling pathways and regulation of apoptosis by the generation of ceramide and plays an important role during the host response to infectious stimuli. It thus has the potential to be used as a novel diagnostic marker in the management of critically ill patients. The objective of our study was to evaluate acid sphingomyelinase serum activity (ASM) as a diagnostic and prognostic marker in a mixed intensive care unit population before, during, and after systemic inflammation.Methods
40 patients admitted to the intensive care unit at risk for developing systemic inflammation (defined as systemic inflammatory response syndrome plus a significant procalcitonin [PCT] increase) were included. ASM was analysed on ICU admission, before (PCTbefore), during (PCTpeak) and after (PCTlow) onset of SIRS. Patients undergoing elective surgery served as control (N = 8). Receiver-operating characteristics curves were computed.Results
ASM significantly increased after surgery in the eight control patients. Patients from the intensive care unit had significantly higher ASM on admission than control patients after surgery. 19 out of 40 patients admitted to the intensive care unit developed systemic inflammation and 21 did not, with no differences in ASM between these two groups on admission. In patients with SIRS and PCT peak, ASM between admission and PCTbefore was not different, but further increased at PCTpeak in non-survivors and was significantly higher at PCTlow compared to survivors. Survivors exhibited decreased ASM at PCTpeak and PCTlow. Receiver operating curve analysis on discrimination of ICU mortality showed an area under the curve of 0.79 for ASM at PCTlow.Conclusions
In summary, ASM was generally higher in patients admitted to the intensive care unit compared to patients undergoing uncomplicated surgery. ASM did not indicate onset of systemic inflammation. In contrast to PCT however, it remained high in non-surviving ICU patients after systemic inflammation. 相似文献90.