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91.
A proteinase (called Proteinase I) present in myxamoebae of the cellular slime mold, , was labeled with [32P] by growth of cells on media containing [32P] orthophosphate. The labeled proteinase was purified to apparent homogeneity and characterized by dissociation chromatography and quantitative immune-precipitin analysis. Based upon the results of these studies it was concluded that phosphoryl moieties were tightly associated (presumably covalently bonded) with the polypeptide subunits of Proteinase I. 相似文献
92.
Acidophilic bacteria of the genera Thiobacillus and Sulfolobus are able to reduce ferric iron when growing on elemental sulfur as an energy source. It has been previously thought that ferric iron serves as a nonbiological oxidant in the formation of acid mine drainage and in the leaching of ores, but these results suggest that bacterial catalysis may play a significant role in the reactivity of ferric iron. 相似文献
93.
How disturbance,competition, and dispersal interact to prevent tree range boundaries from keeping pace with climate change 下载免费PDF全文
Yu Liang Matthew J. Duveneck Eric J. Gustafson Josep M. Serra‐Diaz Jonathan R. Thompson 《Global Change Biology》2018,24(1):e335-e351
Climate change is expected to cause geographic shifts in tree species' ranges, but such shifts may not keep pace with climate changes because seed dispersal distances are often limited and competition‐induced changes in community composition can be relatively slow. Disturbances may speed changes in community composition, but the interactions among climate change, disturbance and competitive interactions to produce range shifts are poorly understood. We used a physiologically based mechanistic landscape model to study these interactions in the northeastern United States. We designed a series of disturbance scenarios to represent varied disturbance regimes in terms of both disturbance extent and intensity. We simulated forest succession by incorporating climate change under a high‐emissions future, disturbances, seed dispersal, and competition using the landscape model parameterized with forest inventory data. Tree species range boundary shifts in the next century were quantified as the change in the location of the 5th (the trailing edge) and 95th (the leading edge) percentiles of the spatial distribution of simulated species. Simulated tree species range boundary shifts in New England over the next century were far below (usually <20 km) that required to track the velocity of temperature change (usually more than 110 km over 100 years) under a high‐emissions scenario. Simulated species` ranges shifted northward at both the leading edge (northern boundary) and trailing edge (southern boundary). Disturbances may expedite species' recruitment into new sites, but they had little effect on the velocity of simulated range boundary shifts. Range shifts at the trailing edge tended to be associated with photosynthetic capacity, competitive ability for light and seed dispersal ability, whereas shifts at the leading edge were associated only with photosynthetic capacity and competition for light. This study underscores the importance of understanding the role of interspecific competition and disturbance when studying tree range shifts. 相似文献
94.
Chondroitin sulphate, injected intravenously into rats and given prior to intravenous 125I-labelled hyaluronan with a mean Mw of about 400 kDa, was shown to inhibit the rapid receptor-mediated uptake of hyaluronan
by the liver. The labelled hyaluronan that remained in the circulation was shown, by size exclusion chromatography of serum
and urine, to be rapidly degraded down to fragments of lower Mw and filtered out into the urine and tissues. When the uptake
of 125I-hyaluronan was inhibited by unlabelled hyaluronan, only very low degradation and urinary excretion were found. Liver uptake
could also be inhibited by dextran sulphate but not by heparin. Unlabelled hyaluronan could inhibit the liver uptake of labelled
chondroitin sulphate but not labelled heparin. Unlabelled chondroitin sulphate and dextran sulphate inhibited cell association
of labelled hyaluronan to liver endothelial cells in culture more effectively than unlabelled hyaluronan. Our data show that
the liver hyaluronan receptors also recognize and effectively bind chondroitin sulphate and dextran sulphate but not heparin
and that a hyaluronan-specific saturable degradative mechanism exists in the circulation. Such a mechanism could explain why
hyaluronan in the general circulation has a much lower Mw than the hyaluronan in lymph. The results also indicate that increased
hyaluronan levels in serum, and increased urinary excretion of hyaluronan, may be secondary to increased outflow of chondroitin
sulphate from the tissues during some pathological conditions.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
95.
PCR primed with minisatellite core sequences yields DNA fingerprinting probes in wheat 总被引:1,自引:0,他引:1
P. J. Bebeli Z. Zhou D. J. Somers J. P. Gustafson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(1-2):276-283
Four minisatellite core sequences were used as primers in a polymerase chain reaction (PCR) technique, known as the directed
amplification of minisatellite-region DNA (DAMD), to detect polymorphisms in three pairs of hexaploid/tetraploid wheat cultivars.
In each pair, the tetraploid cultivar (genomic formula AABB) was extracted from its corresponding hexaploid (genomic formula
AABBDD) parent. Reproducible profiles of the amplified products revealed characteristic bands that were present only in the
hexaploid wheats but not in their extracted tetraploids. Some polymorphisms were observed among the hexaploid cultivars. Twenty-three
DAMD-PCR amplified fragments were isolated and screened as molecular probes on the genomic DNA of wild wheat species, hexaploid
wheat and triticale cultivars. Subsequently, 8 of the fragments were cloned and sequenced. The DAMD-PCR clones revealed various
degrees of polymorphism among different wild and cultivated wheats. Two clones yielded individual-specific DNA fingerprinting
patterns which could be used for species differentiation and cultivar identification. The results demonstrated the use of
DAMD-PCR as a tool for the isolation of informative molecular probes for DNA fingerprinting in wheat cultivars and species.
Received: 13 May 1996/Accepted: 11 October 1996 相似文献
96.
Amiloride does not alter NaCl avoidance in Fischer-344 rats 总被引:2,自引:2,他引:0
Fischer-344 (F-344) rats differ from other common rat strains in that they
fail to show any preference for NaCl at any concentration in two- bottle
preference tests. Because 100 microM amiloride partially blocks the
NaCl-evoked chorda tympani (CT) response in electrophysiological studies,
we tested NaCl preference (0.068-0.273 M) in F-344 rats with and without
100 microM amiloride solution as the solvent. A third group was tested with
unadulterated NaCl solutions following CT transection. Amiloride had no
significant effect on the NaCl preference-aversion function, whereas CT
transection significantly reduced NaCl avoidance. These results suggest
that the amiloride-sensitive component of the NaCl response is not
necessary for F-344 rats to display avoidance of NaCl, but the entire CT
input is.
相似文献
97.
98.
99.
Rational design of a monomeric and photostable far‐red fluorescent protein for fluorescence imaging in vivo 下载免费PDF全文
William Clay Gustafson Rubén Ruiz‐González Luca Signor Fanny Marzocca Franck Borel Matthew P. Klassen Kalpana Makhijani Antoine Royant Yuh‐Nung Jan William A. Weiss Su Guo Xiaokun Shu 《Protein science : a publication of the Protein Society》2016,25(2):308-315
Fluorescent proteins (FPs) are powerful tools for cell and molecular biology. Here based on structural analysis, a blue‐shifted mutant of a recently engineered monomeric infrared fluorescent protein (mIFP) has been rationally designed. This variant, named iBlueberry, bears a single mutation that shifts both excitation and emission spectra by approximately 40 nm. Furthermore, iBlueberry is four times more photostable than mIFP, rendering it more advantageous for imaging protein dynamics. By tagging iBlueberry to centrin, it has been demonstrated that the fusion protein labels the centrosome in the developing zebrafish embryo. Together with GFP‐labeled nucleus and tdTomato‐labeled plasma membrane, time‐lapse imaging to visualize the dynamics of centrosomes in radial glia neural progenitors in the intact zebrafish brain has been demonstrated. It is further shown that iBlueberry can be used together with mIFP in two‐color protein labeling in living cells and in two‐color tumor labeling in mice. 相似文献
100.
Gustafson P 《Biometrics》2007,63(1):69-77
Yin and Ibrahim (2005a, Biometrics 61, 208-216) use a Box-Cox transformed hazard model to acknowledge uncertainty about how a linear predictor acts upon the hazard function of a failure-time response. Particularly, additive and proportional hazards models arise for particular values of the transformation parameter. As is often the case, however, this added model flexibility is obtained at the cost of lessened parameter interpretability. Particularly, the interpretation of the coefficients in the linear predictor is intertwined with the value of the transformation parameter. Moreover, some data sets contain very little information about this parameter. To shed light on the situation, we consider average effects based on averaging (over the joint distribution of the explanatory variables and the failure-time response) the partial derivatives of the hazard, or the log-hazard, with respect to the explanatory variables. First, we consider fitting models which do assume a particular form of covariate effects, for example, proportional hazards or additive hazards. In some such circumstances, average effects are seen to be inferential targets which are robust to the effect form being misspecified. Second, we consider average effects as targets of inference when using the transformed hazard model. We show that in addition to being more interpretable inferential targets, average effects can sometimes be estimated more efficiently than the corresponding regression coefficients. 相似文献