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391.
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Dark-grown cells of mutant C-2A' of Scenedesmus obliquus accumulate monovinyl-and mainly divinyl-protochlorophyllide (PChlide). Both PChlide-forms are equally well photoconverted in vitro by the NADPH-protochlorophyllide oxidoreductase of the light-dependent greening mutant C-2A'of Scenedesmus obliquus. The chlorophyllide (Chlide) resulting from this photoconversion in vivo has a predominantly monovinyl character. Only small traces of a transient Chlide-form with divinyl fluorescence could be detected. 相似文献
393.
Krijn Baptist Trimbos Joyce Broekman Rosemarie Kentie Cees J. M. Musters Geert R. de Snoo 《Journal of Ornithology》2009,150(4):915-920
In the context of population genetic research, a faster and less invasive method of DNA sampling would allow large-scale assessments
of genetic diversity and genetic differentiation with the help of volunteer observers. The aim of this study was to investigate
the usefulness of eggshell membranes as a DNA source for population genetic research, by addressing eggshell membrane DNA
quality, degeneration and cross-contamination. To this end, a comparison was made with blood-derived DNA samples. We have
demonstrated 100% successful DNA extraction from post-hatched Black-tailed Godwit (Limosa limosa) eggshell membranes as well as from blood samples. Using 11 microsatellite loci, DNA amplification success was 99.1% for
eggshell membranes and 97.7% for blood samples. Genetic information within eggshell membrane DNA in comparison to blood DNA
was not affected (F
ST = −0.01735, P = 0.999) by degeneration or possible cross-contamination. Furthermore, neither degeneration nor cross-contamination was apparent
in total genotypic comparison of eggshell membrane DNA and blood sample DNA. Our research clearly illustrates that eggshell
membranes can be used for population genetic research. 相似文献
394.
Demographic rates such as recruitment and survival probability can vary considerably among populations of the same species due to variation in underlying environmental processes. If environmental processes are spatially correlated, nearby populations are expected to have more similar demographic rates than those further apart. Breeding populations and foraging ranges are spatially segregated in colonial seabirds, making them ideal for studying spatial patterns in demographic rates and their effects on local population dynamics. Here we explored variation in age-dependent survival probabilities across 14 colonies of Herring Gulls Larus argentatus breeding along the Dutch North Sea coast. We used long-term mark–recapture data of marked fledglings to estimate survival, and estimated spatial autocorrelation of survival probabilities. We assessed whether survival until recruitment age or until 10 years old (close to their expected lifespan) explained variation in population trajectories of each colony. Juvenile and adult survival showed a strong, but different, north-to-south gradient in survival probability, with lower juvenile but higher adult survival in northern colonies than southern colonies, whereas the spatial pattern of immature survival was less distinct. Neither recruitment nor the proportion of 10-year-old adults alive predicted whether a colony collapsed, declined, remained stable or increased. The distinct spatial pattern in survival suggests variation in regional food availability, which do not seem to drive local population dynamics. The absence of a link between survival and colony trajectories implies that connectivity between populations plays an important role affecting population dynamics. 相似文献
395.
Louis J. Ignarro Rosemarie A. Gross 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,541(2):170-180
Guanosine 5′-tetraphosphate (GTP4) stimulated mammalian adenylate cyclase activity at concentrations down to 1 μM. Greater stimulatory activity was apparent with lung than with heart, brain or liver from the rat. At a concentration of 0.1 mM, GTP4 stimulated lung adenylate cyclase activity from rat, guinea pig and mouse about four-fold. Other guanine nucleotides such as GTP, GDP, GMP, guanosine 3′, 5′-monophosphate and 5′-guanylylimidodiphosphate (GMP · PNP) also stimulated mammalian adenylate cyclase activity. GMP · PNP irreversibly activated, whereas GTP4 and GTP reversibly activated adenylate cyclase. Adenosine 5′-tetraphosphate (ATP4) stimulated rat lung and liver but inhibited rat heart and brain adenylate cyclase activities. Lung from guinea pig and mouse were not affected by ATP4. The formation of cyclic AMP by GTP4-stimulated rat lung adenylate cyclase was verified by Dowex-50 (H+), Dowex 1-formate and polyethyleneimine cellulose column chromatography. GTP4 was at least three times more potent than 1-isoproterenol in stimulating rat lung adenylate cyclase activity. The β-adrenergic receptor antagonist propranolol blocked the effect of 1-isoproterenol but not that of GTP4, thus, suggesting that GTP4 and β-adrenergic agonists interact with different receptor sites on membrane-bound adenylate cyclase. Stimulation of rat lung and liver adenylate cyclase activities with 1-isoproterenol was potentiated by either GTP4 or GMP. PNP, thus indicating that GTP4 resembles other guanine nucleotides in their capacity to increase the sensitivity of adenylate cyclase to β-adrenergic agonists. Stimulation of adenylate cyclase activity by guanine derivatives requires one or more free phosphate moieties on the 5 position of ribose, as no effect was elicited with guanine, guanosine, guanosine 2′-monophosphate, guanosine 3′-monophosphate or guanosine 2′,5′-monophosphate. Ribose, ribose 5-phosphate, phosphate and pyrophosphate were inactive. Pyrimidine nucleoside mono-, di-, tri- and tetraphosphates elicited negligible effects on mammalian adenylate cyclase activity. 相似文献
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399.
Do human platelets express COX-2? 总被引:4,自引:0,他引:4
Rosemarie Reiter Ulrike Resch Helmut Sinzinger 《Prostaglandins, leukotrienes, and essential fatty acids》2001,64(6):299-305
The rate-limiting enzyme in prostaglandin (PG)- and thromboxane (TX)-synthesis is known as cyclooxygenase (COX). The COX-enzyme family consists of the classical COX-1 and the inducible COX-2-enzyme. To investigate whether platelets contain COX-2, we measured thiobarbituric acid reactive substances (TBARS) after either blocking COX-1 or COX-2 or adding compounds known to affect COX-expression. To stimulate platelets' different reagents such as collagen, thrombin and arachidonic acid (AA) were used. The inhibitors used in this study were acetylsalicylic acid (ASA), indomethacin and NS-398. Using the western-blot technique, we failed to detect COX-2 in platelets while COX-1 was detectable. We were not able to discover COX-2 in platelets using the methods we applied. As the amount of COX-2 in platelets might be below the detection limit of the methods used, the biological relevance COX-2 in platelets, if even existing at low amounts, remains to be established. 相似文献