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排序方式: 共有515条查询结果,搜索用时 257 毫秒
1.
Strategies for signal amplification in nucleic acid detection 总被引:3,自引:0,他引:3
S. Calin Andras J. Brian Power Edward C. Cocking Michael R. Davey 《Molecular biotechnology》2001,19(1):29-44
Many aspects of molecular genetics necessitate the detection of nucleic acid sequences. Current approaches involving target
amplification (in situ PCR, Primed in situ Labeling, Self-Sustained Sequence Replication, Strand Displacement Amplification), probe amplification (Ligase Chain Reaction,
Padlock Probes, Rolling Circle Amplification) and signal amplification (Tyramide Signal Amplification, Branched DNA Amplification)
are summarized in the present review, together with their advantages and limitations. 相似文献
2.
Manfred Keller Andras Seregi Georg Hertting Rolf Jackisch 《Neurochemistry international》1987,10(4):433-443
Prostaglandin (PG) and thromboxane B2 (TXB2) biosynthesis was studied in cultured astrocytes from neonatal rat brain hemispheres. After two weeks of cultivation, prostanoids were formed with the spectrum: PGD2 > TXB2 > PGF2 > PGE2, as measured by specific radioimmunoassays. Under basal conditions PGD2 biosynthesis (9.55 ng/mg protein/15 min) was in the same order of magnitude as the sum of the other prostanoids. The formation of prostanoids was stimulated in a concentration dependent manner (up to 6–10 fold) by the calcium ionophore A 23187 (0.01–10 μM) as well as by melittin (0.01–5 μg/ml), phospholipase A2 (10–40 U/ml) and phospholipase C (0.01–1 U/ml). Basal and evoked PG and TXB2 biosynthesis depended on the availability of Ca2+, as demonstrated in Ca2+ free incubation medium containing Na2EDTA (1 μM), or with verapamil (100 μM) and 3,4,5-trimethoxybenzoic acid-8-(diethylamino)-octylester-HCl (TMB-8, 1–100 μM). Indomethacin (10 μM), mepacrine (100 μM) and p-bromophenacylbromide (50 μ M) inhibited basal and evoked PG formation. Thin-layer chromatography (TLC) detection after incubation of the cells with [3H]arachidonic acid (1 μCi/ml, for 60 min) confirmed the results obtained by radioimmunoassay. Incubation of [3H]arachidonic acid labelled cells with inonophore or phospholipases, followed by lipid extraction and TLC, showed that A 23187 liberated [3H]arachidonic acid predominantly from phosphatidylethanolamine, whereas phospholipase A2 and C reduced mainly the labelling of the phosphatidyl-inositol/-choline fraction. Potassium depolarization of the cells did not enhance prostanoid formation. Similarly, drugs with affinity to - or β-adrenoceptors, or to dopamine-, 5-hydroxytryptamine-, muscarine-, histamine-, glutamate-, aspartate-, GABA, adenosine- and opioid-receptors failed to stimulate prostanoid biosynthesis. Also compounds like angiotensin, bradykinin and thrombin were ineffective in this respect.
In conclusion, our results confirm that cultured astrocytes possess the complete pattern of enzymes necessary for prostanoid formation and hence might play a crucial role in brain prostanoid biosynthesis. Stimulation of prostanoid biosynthesis involves Ca2+-dependent activation of phospholipase A2, cyclooxygenase reaction and further PG metabolism. However, the endogenous stimulus for enhanced prostanoid synthesis in the brain still has to be established. 相似文献
3.
4.
Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
5.
Andras Schaefer Reinhard Zibirre Peter Kabus Jutta Kühne Gebhard Koch 《Bioscience reports》1982,2(8):613-615
After exposure of HeLa cells to poliovirus there is a rapid decline (within minutes) in fluorescence polarization of DPH (1,6-diphenyl-1,3,5-hexatriene). Within one hour after infection the (Na+/K+)ATPase activity of an isolated plasma-membrane-rich fraction is enhanced, the cell volume decreases, and the intracellular concentration of a potent low-molecular-weight inhibitor of host protein synthesis increases. 相似文献
6.
Peter Andras 《PloS one》2012,7(11)
Particle swarm optimization is a popular method for solving difficult optimization problems. There have been attempts to formulate the method in formal probabilistic or stochastic terms (e.g. bare bones particle swarm) with the aim to achieve more generality and explain the practical behavior of the method. Here we present a Bayesian interpretation of the particle swarm optimization. This interpretation provides a formal framework for incorporation of prior knowledge about the problem that is being solved. Furthermore, it also allows to extend the particle optimization method through the use of kernel functions that represent the intermediary transformation of the data into a different space where the optimization problem is expected to be easier to be resolved–such transformation can be seen as a form of prior knowledge about the nature of the optimization problem. We derive from the general Bayesian formulation the commonly used particle swarm methods as particular cases. 相似文献
7.
Studies of crayfish chemical ecology have been conducted in both day and night conditions. This variation may hinder the comparison of data among studies, if the responses by crayfish to chemical cues are dependent upon the time at which the cues are encountered. We tested the hypothesis that responses to chemical cues are dependent on observation time using the red swamp crayfish, Procambarus clarkii. Procambarus clarkii is known to exhibit a light-regulated circadian rhythm, with nocturnal activity peaks. Habitat use differed significantly between non-stimulated periods and periods of exposure to a food stimulus, but no effects of photoperiod (normal vs. reversed) or laboratory conditions (dark vs. light) were observed. The results suggest that, all else being equal, (1) studies of crayfish chemical ecology can be successfully conducted in a variety of experimental conditions, and (2) previous studies conducted at various times of the day should have comparable results. 相似文献
8.
James E. Polston Carolyn E. Pritchett Jonathan M. Tomasko Ann M. Rogers Lorenzo Leggio Panayotis K. Thanos Nora D. Volkow Andras Hajnal 《PloS one》2013,8(12)
Roux-en-Y gastric bypass surgery (RYGB) is an effective treatment for severe obesity. Clinical studies however have reported susceptibility to increased alcohol use after RYGB, and preclinical studies have shown increased alcohol intake in obese rats after RYGB. This could reflect a direct enhancement of alcohol’s rewarding effects in the brain or an indirect effect due to increased alcohol absorption after RGYB. To rule out the contribution that changes in alcohol absorption have on its rewarding effects, here we assessed the effects of RYGB on intravenously (IV) administered ethanol (1%). For this purpose, high fat (60% kcal from fat) diet-induced obese male Sprague Dawley rats were tested ∼2 months after RYGB or sham surgery (SHAM) using both fixed and progressive ratio schedules of reinforcement to evaluate if RGYB modified the reinforcing effects of IV ethanol. Compared to SHAM, RYGB rats made significantly more active spout responses to earn IV ethanol during the fixed ratio schedule, and achieved higher breakpoints during the progressive ratio schedule. Although additional studies are needed, our results provide preliminary evidence that RYGB increases the rewarding effects of alcohol independent of its effects on alcohol absorption. 相似文献
9.
Hoon-Ki Sung Kyung-Oh Doh Joe Eun Son Jin Gyoon Park Yunui Bae Soojeong Choi Seana Mary Lunney Nelson Rebecca Cowling Kristina Nagy Iacovos P. Michael Gou Young Koh S. Lee Adamson Tony Pawson Andras Nagy 《Cell metabolism》2013,17(1):61-72
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10.
Jason P Andras Peter D Fields Louis Du Pasquier Maridel Fredericksen Dieter Ebert 《Molecular biology and evolution》2020,37(12):3439
Knowledge of the genetic architecture of pathogen infectivity and host resistance is essential for a mechanistic understanding of coevolutionary processes, yet the genetic basis of these interacting traits remains unknown for most host–pathogen systems. We used a comparative genomic approach to explore the genetic basis of infectivity in Pasteuria ramosa, a Gram-positive bacterial pathogen of planktonic crustaceans that has been established as a model for studies of Red Queen host–pathogen coevolution. We sequenced the genomes of a geographically, phenotypically, and genetically diverse collection of P. ramosa strains and performed a genome-wide association study to identify genetic correlates of infection phenotype. We found multiple polymorphisms within a single gene, Pcl7, that correlate perfectly with one common and widespread infection phenotype. We then confirmed this perfect association via Sanger sequencing in a large and diverse sample set of P. ramosa clones. Pcl7 codes for a collagen-like protein, a class of adhesion proteins known or suspected to be involved in the infection mechanisms of a number of important bacterial pathogens. Consistent with expectations under Red Queen coevolution, sequence variation of Pcl7 shows evidence of balancing selection, including extraordinarily high diversity and absence of geographic structure. Based on structural homology with a collagen-like protein of Bacillus anthracis, we propose a hypothesis for the structure of Pcl7 and the physical location of the phenotype-associated polymorphisms. Our results offer strong evidence for a gene governing infectivity and provide a molecular basis for further study of Red Queen dynamics in this model host–pathogen system. 相似文献