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41.
Some properties of Saccharomyces kluyveri 总被引:2,自引:0,他引:2
42.
Barker D Stacey MJ Adal MN 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1970,258(825):315-346
The motor innervation of cat spindles was examined in hindlimb muscles using a variety of techniques employed in light and electron microscopy. Observations were made on teased, silver preparations of 267 spindles sampled from the peroneal, flexor hallucis longus, and soleus muscles, hereafter referred to as the PER/FHL/SOL series. The γ innervation. Trail endings are almost invariably present, and innervate both bag and chain muscle fibres. Trail fibres accounted for 64.6 to 74.8% of the total fusimotor supply to samples of spindle poles in the PER/FHL/SOL series, the mean number of fibres per pole varying from 2.7 to 5.0 in the different muscles, and the mean number of ramifications (areas of synaptic contact) per fibre being 3.7. By contrast, the p?innervation of a spindle pole generally consists of a single fibre supplying only one plate. In the above samples p(2) fibres accounted for 4.1 to 28.0% of the total fusimotor supply, and the mean number of fibres per pole varied from 0.3 to 1.2 in the different muscles. Ninety per cent of p(2) plates innervate bag fibres. The α innervation. The structure of p?plates as seen in both light and electron microscopy compares very closely with that of extrafusal plates. After nerve section p?plates degenerate at the same time as extrafusal plates, being the first of the three types of fusimotor ending to disappear. The frequency of the p?innervation is similar to that of the p?innervation. In the same samples of PER/FHL/SOL spindle poles as above p? fibres accounted for 6.0 to 28.8% of the total fusimotor supply, the mean number of fibres per pole varying from 0.25 to 2.1 in the different muscles. The majority of p? fibres enter a pole to terminate in one plate only. Seventy-five per cent of the plates innervate bag fibres. The three types of fusimotor ending are thus not selectively distributed to the two types of intrafusal muscle fibre. All three types of fusimotor fibre may branch within the spindle so as to innervate both bag and chain fibres. Bag fibres receive both types of plate ending as well as trail endings. Most chain fibres receive trail endings only; the rest receive either a p?or a p?plate innervation in addition, 25% of the p?and 10% of the p?innervation being distributed to chain fibres. The significance of this nonselective innervation is interpreted as indicating that the type of contraction elicited by stimulating a fusimotor fibre depends upon the type of ending initiating it rather than upon the type of muscle fibre executing it. Reasons are given for concluding that the dynamic response is controlled via the p?and p?plates, and that the static response is controlled by the trail endings. The participation of the α fibres in mammalian fusimotor innervation, previously regarded as a vestigial feature, proved to be widespread in the muscles studied and more prevalent in fast muscles (FHL, peroneus digiti quinti) than slow (soleus). A low frequency of p?innervation is offset by a high frequency of p?(as in peroneus longus), and vice versa (as in FHL). It is unlikely that collaterals from slow α fibres innervating type B muscle fibres are wholly responsible for the high frequency of the p?innervation in FHL, and it is suggested that collaterals may also be derived from fast α fibres innervating type C muscle fibres. The possibility of there being some motor fibres of α conduction velocity and with an exclusively fusimotor distribution is also taken into account. 相似文献
43.
Separations of isomeric polyols 总被引:1,自引:0,他引:1
44.
A. K. Sheridan R. Frankham L. P. Jones K. A. Rathie J. S. F. Barker 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1968,38(5):179-187
Summary Phenotypic variance for each of several bristle number characters (abdominal, sternopleural, second and third coxal) was partitioned using both hierarchal and dialled designs. Heritabilities and genetic correlations were estimated from parent-offspring regressions and correlations and half-sib correlations.A high proportion of the genetic variance for abdominal bristle number was due to epistatic and sex-linked gene action, but most of the genetic variance for the other characters was additive autosomal.The genetic correlations among sternopleural, and second and third coxal bristle numbers were all high, but that between abdominals and sternopleurals was low, while those between abdominals and either second or third coxals were virtually zero. An appreciable proportion of the covariance between abdominal and sternopleural bristle numbers was non-additive genetic.The diallel method gave more reliable estimates of genetic parameters when non-additive or sex-linked genetic variation was present.
Zusammenfassung Für eine Anzahl verschiedener Borstenzahl-Charaktere (abdominales, sternopleurales, 2. und 3. coxales Segment) wurde die phänotypische Varianz unter Verwendung hierarchischer und dialleler Versuchsanlagen unterteilt. Anhand von Elter-Nachkommen-Regressionen und-Korrelationen und von Halbgeschwister-Korrelationen wurden Heritabilitäten und genetische Korrelation geschätzt.Ein hoher Anteil der genetischen Varianz für die Zahl abdominaler Borsten wurde durch epistatische Effekte und die Wirkung geschlechtsgekoppelter Gene bedingt. Bei den anderen Charakteren war der größte Anteil der genetischen Varianz additiv autosomal.Die genetische Korrelation zwischen der Zahl der Borsten sternopleural und 2. und 3. Segment coxal war durchweg hoch, zwischen abdominal und sternopleural niedrig und zwischen abdominal und sowohl 2. und 3. coxal praktisch gleich null.Ein bemerkenswerter Anteil der Covarianz zwischen der Zahl abdominaler und sternopleuraler Borsten war nicht-additiv genetisch.Die Diallel-Methode ergab zuverlässigere Schätzungen der genetischen Parameter, wenn nicht-additive oder geschlechtsgebundene genetische Variation vorlag.相似文献
45.
Fractionation of native and denatured transforming deoxyribonucleic acid from Bacillus subtilis 总被引:2,自引:2,他引:0 下载免费PDF全文
1. Native DNA from Bacillus subtilis was fractionated by stepwise elution from methylated albumin, the transforming activity being confined to two out of four fractions. Partial separation of DNA active in transformation for the arginine marker from that showing activity for the histidine and tryptophan markers was achieved. 2. Partial denaturation of DNA at 90 degrees and 93.5 degrees resulted in the preferential destruction of transforming activity for the histidine and tryptophan markers. 3. Denaturation of DNA at 100 degrees followed by chromatography on methylated albumin yielded five fractions, two of which exhibited residual activity. Redenaturation at 100 degrees resulted in the interconversion of four out of the five fractions. Redenaturation of fractions labelled with (15)N and (2)H suggested the presence of a specific component that did not readily take part in the interconversions. 相似文献
46.
A bacterium was isolated from soil which utilizes threo-beta-methyl-l-aspartate, certain other amino acids, and a variety of organic substances as single energy sources. It is, or closely resembles, Pseudomonas putida biotype B. The ability of this organism to rapidly decompose such amino acids is dependent on inducible enzyme systems. Dialyzed cell-free extracts of this bacterium metabolize beta-methylaspartate only when catalytic amounts of alpha-ketoglutarate, or pyruvate, and pyridoxal phosphate are also present. The main products formed from beta-methylaspartate under these conditions are alpha-aminobutyrate, carbon dioxide, and alpha-ketobutyrate. When l-aspartate is substituted for beta-methylaspartate in this system, it is converted mainly to alanine and carbon dioxide. beta-Methyloxalacetate is decarboxylated, and the resulting alpha-ketobutyrate is converted enzymatically in the presence of glutamate to alpha-aminobutyrate which accumulates. The added keto acids are converted, in part, to the corresponding amino acids probably by transamination. The data indicate that beta-methylaspartate is converted to alpha-aminobutyrate, and aspartate to alanine, by a circuitous transamination-beta-decarboxylation-transamination sequence rather than by a direct beta-decarboxylation. 相似文献
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