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91.
J M Steim C Camaioni Neto P S Sarin D K Sun R K Sehgal J G Turcotte 《Biochemical and biophysical research communications》1990,171(1):451-457
3'-Azido-3'-deoxythymidine-5'-phosphate diglyceride (16:0/18:1 omega 9), a phosphatic acid conjugate of AZT, is active against HIV replication in H9 cells and syncytia formation in MOLT-3 cells. The activities rank as AZT greater than pure conjugate greater than conjugate in mixed liposomes, with the pure conjugate having about one-third the activity of free AZT. The compound binds very rapidly to serum lipoproteins, but not to serum albumin, alpha and beta globulins, or red cells. Pancreatic phospholipase A2 hydrolyzes it to the lysophosphatidic acid conjugate. 相似文献
92.
Recognizing the forest for the trees: testing temporal patterns of cladogenesis using a null model of stochastic diversification 总被引:2,自引:1,他引:1
Computer simulations are developed and employed to examine the expected
temporal distributions of nodes under a null model of stochastic lineage
bifurcation and extinction. These Markovian models of phylogenetic process
were constructed so as to permit direct comparisons against empirical
phylogenetic trees generated from molecular or other information available
solely from extant species. For replicate simulated phylads with n extant
species, cumulative distribution functions (cdf's) of branching times were
calculated, and compared (using the Kolmogorov-Smirnov test statistic D) to
those from three published empirical trees. Molecular phylogenies for
columbine plants and avian cranes showed statistically significant
departures from the null expectations, in directions indicating recent and
ancient species' radiations, respectively, whereas a molecular phylogeny
for the Drosophila virilis species group showed no apparent historical
clustering of branching events. Effects of outgroup choice and phylogenetic
frame of reference were investigated for the columbines and found to have a
predictable influence on the types of conclusions to be drawn from such
analyses. To enable other investigators to statistically test for
nonrandomness in temporal cladogenetic pattern in empirical trees generated
from data on extant species, we present tables of mean cdf's and associated
probabilities under the null model for expected branching times in phylads
of varying size. The approaches developed in this report complement and
extend those of other recent methods for employing null models to assess
the statistical significance of pattern in evolutionary trees.
相似文献
93.
94.
Stimulation of monoacylglycerophosphate formation by Z protein 总被引:5,自引:0,他引:5
Z protein has been purified from 110,000 × g rat liver supernatant using Sephadex G-100 and DEAE Sephadex. Z protein obtained in this manner was superior to albumin in stimulating the esterification of sn-glycerol-3-phosphate in the presence of palmityl-CoA and rat liver microsomes. These observations constitute direct evidence for the possible role of Z protein in fatty acid metabolism. 相似文献
95.
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97.
Oxidative stress-activated zinc cluster protein Stb5 has dual activator/repressor functions required for pentose phosphate pathway regulation and NADPH production 下载免费PDF全文
In Saccharomyces cerevisiae, zinc cluster protein Pdr1 can form homodimers as well as heterodimers with Pdr3 and Stb5, suggesting that different combinations of these proteins may regulate the expression of different genes. To gain insight into the interplay among these regulators, we performed genome-wide location analysis (chromatin immunoprecipitation with hybridization to DNA microarrays) and gene expression profiling. Unexpectedly, we observed that Stb5 shares only a few target genes with Pdr1 or Pdr3 in rich medium. Interestingly, upon oxidative stress, Stb5 binds and regulates the expression of most genes of the pentose phosphate pathway as well as of genes involved in the production of NADPH, a metabolite required for oxidative stress resistance. Importantly, deletion of STB5 results in sensitivity to diamide and hydrogen peroxide. Our data suggest that Stb5 acts both as an activator and as a repressor in the presence of oxidative stress. Furthermore, we show that Stb5 activation is not mediated by known regulators of the oxidative stress response. Integrity of the pentose phosphate pathway is required for the activation of Stb5 target genes but is not necessary for the increased DNA binding of Stb5 in the presence of diamide. These data suggest that Stb5 is a key player in the control of NADPH production for resistance to oxidative stress. 相似文献
98.
JC Biro 《Theoretical biology & medical modelling》2006,3(1):15-12
Background
Prediction of protein folding and specific interactions from only the sequence (ab initio) is a major challenge in bioinformatics. It is believed that such prediction will prove possible if Anfinsen's thermodynamic principle is correct for all kinds of proteins, and all the information necessary to form a concrete 3D structure is indeed present in the sequence. 相似文献99.
Prospecting in a solitary breeder: chick production elicits territorial intrusions in common loons 总被引:2,自引:0,他引:2
Piper Walter H.; Walcott Charles; Mager John N. III; Perala Margaret; Tischler Keren B.; Harrington Erin; Turcotte Amy J.; Schwabenlander Marc; Banfield Nathan 《Behavioral ecology》2006,17(6):881-888
In many species, young animals learn about various breedingpatches in one year and use what they have learned to settlein a promising patch the next. Common loons (Gavia immer) seemgood candidates for such prospecting as prebreeders and displacedbreeders intrude frequently into breeding territories defendedby monogamous pairs yet engage in no extrapair copulations.We tested 3 hypotheses for prospecting in loons. The permanentattributes hypothesis gained little support as we found no consistentdifferences in quality between territories and no physical orbiotic trait that predicted reproductive success in a territory.We found some support for the conspecific attraction hypothesisas intruders were attracted to conspecifics in a lake in theshort term; however, intrusions were not more frequent in territoriesthat had experienced regular use by a pair the previous yearthan in territories that had previously been vacant. Instead,the increase in intrusion rate after a year of chick productionsupported the habitat-copying hypothesis, which states thatfloaters use the presence of chicks as a cue to target territoriesfor future attempts at territorial takeover. Despite this systemof prospecting, founding of new territories was common. Onestriking finding was the tendency of territorial breeders toconceal chicks from flying intruders, perhaps to avoid futureterritorial takeover. 相似文献
100.
Tucker MZ Turcotte LP 《American journal of physiology. Endocrinology and metabolism》2003,285(4):E827-E835
The purpose of the present study was to examine the utilization of fatty acids (FA) and muscle substrates by skeletal muscle in young, middle-aged, and old adult rats under hyperglycemic and hyperinsulinemic conditions. Male Fischer 344 x Brown Norway rats aged 5, 15, or 24 mo underwent hindlimb perfusion with a medium of 20 mM glucose, 1 mM palmitate, 1,000 microU/ml insulin, [1-14C]palmitate, and [3-3H]glucose. Glucose uptake and palmitate delivery were similar among age groups. Palmitate uptake and oxidation as well as muscle protein concentration of fatty acid translocase (FAT/CD36) and plasma membrane fatty acid-binding protein (FABPPM) were significantly increased (P < or = 0.05) in 24- vs. 5- and 15-mo-old animals. Compared with 5- and 15-mo-old animals, pre- and postperfusion muscle triglyceride (TG) levels were significantly (P < 0.05) elevated 72-145% in red and 112-129% in white muscles of 24-mo-old animals. Palmitate uptake was associated with total preperfusion TG concentration (r2 = 0.27, P < 0.05) and total TG synthesis rate (r2 = 0.68, P < 0.05). These results indicate that, under insulin-stimulated conditions, FA uptake is significantly increased in old animals, which is associated with increased rates of TG synthesis and may contribute to the accumulation of TG in muscle of old animals. 相似文献