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991.
992.
The detergent solubilization and reformation of phospholipid vesicles was studied for various detergents. Two distinct mechanisms of vesicle-to-micelle and micelle-to-vesicle transition were observed by turbidimetry and cryo-electron microscopy. The first mechanism involves fast solubilization of phospholipids and occurs via open vesicular intermediates. The reverse process, micelle-to-vesicle transition, mimics the vesicle-to-micelle transition. In the second mechanism the solubilization is a slow process that proceeds via micelles that pinch off from closed vesicles. During vesicle reformation, the micelle-to-vesicle transition, a large number of densely packed multilamellar vesicles are formed. The route used, for solubilization and reformation, by a given detergent-phospholipid combination is critically dependent on the overall packing parameter of the detergent-saturated phospholipid membranes. By a change of the overall packing parameter the solubilization and or reformation mechanism could be changed. All five detergents tested fit within the proposed model. With two detergents the mechanism could be changed by changing the phospholipid composition or the medium conditions. 相似文献
993.
Two forms of the equation for expression of the rate constant for electron transfer through a Marcus-type treatment are discussed. In the first (exergonic) form, the Arrhenius exponential term was replaced by its classical Marcus term; in the second (endergonic) form, the forward rate constant was replaced by the reverse rate constant (the forward rate constant in the exergonic direction), which was expanded to an equivalent Marcus term and multiplied by the equilibrium constant. When the classical Marcus treatment was used, these two forms of the rate equation give identical curves relating the logarithm of the rate constant to the driving force. The Marcus term for the relation between activation free-energy, ΔG#, reorganization energy, λ, and driving force, ΔGo, derived from parabolas for the reactant and product states, was identical when starting from exergonic or endergonic parabolas. Moser and colleagues introduced a quantum mechanical correction factor to the Marcus term in order to fit experimental data. When the same correction factor was applied in the treatment for the endergonic direction by Page and colleagues, a different curve was obtained from that found with the exergonic form. We show that the difference resulted from an algebraic error in development of the endergonic equation. 相似文献
994.
Stuart Swanston J. Thomas William T.B. Powell Wayne Young George R. Lawrence Patricia E. Ramsay Luke Waugh Robbie 《Molecular breeding : new strategies in plant improvement》1999,5(2):103-109
Two barley quality characters of specific interest to whisky distillers are fermentability and production of the ethyl carbamate
precursor, epi-heterodendrin. The former is a quantitative trait, while the latter may be determined by a single Mendelian
genetic factor. Molecular markers have been used to map, to barley chromosome 5(1H), the locus responsible for epi-heterodendrin
synthesis and the inheritance of this character and a closely linked microsatellite have been followed through the pedigrees
of several contemporary cultivars. Six loci, which affected fermentability in random inbred lines from a barley cross, have
been mapped to chromosomes 2(2H), 3(3H) and 7(5H). This would permit the use of molecular markers in a breeding programme,
to select barleys best suited for distilling. In addition, one of the loci related to fermentability mapped to an area of
the genome indicated, by a previous study, to affect the activity of β-amylase, a character likely to influence fermentability.
Molecular markers may, therefore, be powerful tools in exploring the contribution and detecting the mode of action of the
genetical components influencing malt whisky distilling.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
995.
Alteration of the Repressor Activity of MarR, the Negative Regulator of the Escherichia coli marRAB Locus, by Multiple Chemicals In Vitro 下载免费PDF全文
MarR negatively regulates expression of the multiple antibiotic resistance operon (marRAB) in Escherichia coli. In this study, it was demonstrated that sodium salicylate, plumbagin, 2, 4-dinitrophenol, and menadione-inducers of the marRAB operon in whole cells-all interfered with the repressor activity of MarR in vitro. It is proposed that these compounds can interact directly with MarR to affect its repressor activity. 相似文献
996.
997.
998.
Hargreaves Mark; McKenna Michael J.; Jenkins David G.; Warmington Stuart A.; Li Jia L.; Snow Rodney J.; Febbraio Mark A. 《Journal of applied physiology》1998,84(5):1687-1691
Six men werestudied during four 30-s "all-out" exercise bouts on anair-braked cycle ergometer. The first three exercise bouts wereseparated by 4 min of passive recovery; after the third bout, subjectsrested for 4 min, exercised for 30 min at 30-35% peakO2 consumption, and rested for afurther 60 min before completing the fourth exercise bout. Peak powerand total work were reduced (P < 0.05) during bout 3 [765 ± 60 (SE) W; 15.8 ± 1.0 kJ] compared withbout 1 (1,168 ± 55 W, 23.8 ± 1.2 kJ), but no difference in exercise performance was observed betweenbouts 1 and4 (1,094 ± 64 W, 23.2 ± 1.4 kJ). Before bout 3, muscle ATP,creatine phosphate (CP), glycogen, pH, and sarcoplasmic reticulum (SR)Ca2+ uptake were reduced, whilemuscle lactate and inosine 5'-monophosphate wereincreased. Muscle ATP and glycogen before bout4 remained lower than values beforebout 1 (P < 0.05), but there were no differences in muscle inosine 5'-monophosphate, lactate, pH, and SR Ca2+ uptake. Muscle CP levelsbefore bout 4 had increased aboveresting levels. Consistent with the decline in muscle ATP wereincreases in hypoxanthine and inosine before bouts3 and 4. The decline in exercise performance does not appear to be related to a reduction inmuscle glycogen. Instead, it may be caused by reduced CP availability, increased H+ concentration,impairment in SR function, or some other fatigue-inducing agent. 相似文献
999.
1000.