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41.
Identification of alcaligin as the siderophore produced by Bordetella pertussis and B. bronchiseptica. 总被引:6,自引:5,他引:1 下载免费PDF全文
C H Moore L A Foster D G Gerbig Jr D W Dyer B W Gibson 《Journal of bacteriology》1995,177(4):1116-1118
The siderophores produced by iron-starved Bordetella pertussis and B. bronchiseptica were purified and were found to be identical. Using mass spectrometry and proton nuclear magnetic resonance, we determined that the siderophore produced by these organisms was identical to alcaligin, a siderophore produced by Alcaligenes denitrificans. 相似文献
42.
Structural heterogeneity of the various forms of apomyoglobin: implications for protein folding. 总被引:1,自引:1,他引:0 下载免费PDF全文
R. Gilmanshin R. B. Dyer R. H. Callender 《Protein science : a publication of the Protein Society》1997,6(10):2134-2142
Temperature-induced denaturation transitions of different structural forms of apomyoglobin were studied monitoring intrinsic tryptophan fluorescence. It was found that the tryptophans are effectively screened from solvent both in native and acid forms throughout most of the temperature range tested. Thus, the tryptophans' surrounding do not show a considerable change in structure where major protein conformational transitions have been found in apomyoglobin using other techniques. At high temperatures and under strong destabilizing conditions, the tryptophans' fluorescence parameters show sigmoidal thermal denaturation. These results, combined with previous studies, show that the structure of this protein is heterogeneous, including native-like (tightly packed) and molten globule-like substructures that exhibit conformation (denaturation) transitions under different conditions of pH and temperature (and denaturants). The results suggest that the folding of this protein proceeds via two "nucleation" events whereby native-like contacts are formed. One of these events, which involves AGH "core" formation, appears to occur very early in the folding process, even before significant hydrophobic collapse in the rest of the protein molecule. From the current studies and other results, a rather detailed picture of the folding of myoglobin is presented, on the level of specific structures and their thermodynamical properties as well as formation kinetics. 相似文献
43.
44.
Resting cells of Bacteroides melaninogenicus fermented L-[14C]aspartate as a single substrate. The 14C-labeled products included succinate, acetate, CO2, oxaloacetate, formate, malate, glycine, alanine, and fumarate in the relative percentages 68, 15, 9.9, 2.7, 1.8, 1.0, 0.7, 0.5, and 0.06, respectively, based on the total counts per minute of the L-[14C]aspartate fermented. Ammonia was produced in high amounts, indicating that 96% of the L-aspartate fermented was deaminated. These data suggest that L-aspartate is mainly being reduced through a number of intermediate reactions involving enzymes of the tricarboxylic acid cycle to succinate. L-[14C]asparagine was also fermented by resting cells of B. melaninogenicus to form L-aspartate, which was subsequently, but less actively, fermented. 相似文献
45.
This paper reviews the experience of the Workmen''s Compensation Board of Ontario in identifying cases of cancer that could be attributed to occupational hazards. Worker''s claims for compensation are allowed if there is reasonable medical evidence that their cancer was caused by exposure to risk factors associated with their occupation. Details of the types of cancer associated with specific carcinogens or fields of employment are discussed. About 50% of the cases were related to exposure in particular industrial operations that functioned for relatively brief periods. The number of deaths from cancer identified as being caused by occupational factors is compared with the total for cancer from all causes in Ontario during the period 1971 through 1975. Although all workers eligible for compensation may not have been identified, the data suggest that less than 1% of cancer is presently caused by occupational factors. 相似文献
46.
47.
Resting cells of Bacteroides melaninogenicus fermented L-[14C]aspartate as a single substrate. The 14C-labeled products included succinate, acetate, CO2, oxaloacetate, formate, malate, glycine, alanine, and fumarate in the relative percentages 68, 15, 9.9, 2.7, 1.8, 1.0, 0.7, 0.5, and 0.06, respectively, based on the total counts per minute of the L-[14C]aspartate fermented. Ammonia was produced in high amounts, indicating that 96% of the L-aspartate fermented was deaminated. These data suggest that L-aspartate is mainly being reduced through a number of intermediate reactions involving enzymes of the tricarboxylic acid cycle to succinate. L-[14C]asparagine was also fermented by resting cells of B. melaninogenicus to form L-aspartate, which was subsequently, but less actively, fermented. 相似文献
48.
Heart and scaphognathite beating activities of Crangon crangon (L.) have been monitored for several days under a fixed photoperiod regime. Freshly-captured animals, in particular, spend much of the light period buried in the substratum, and these periods are characterized by low heart rates and high scaphognathite beating rates. During the dark period, animals emerge from the sand. Swimming and walking excursions are most common during the first hours of the dark period, and such times are characterized by high heart rates and higher scaphognathite rates (both compared with daytime, buried rates). Periods of low activity, with the animals resting on the surface of the sand, extend over much of the remainder of the dark period, and at these times the animals had high heart rates but scaphognathite rates lower than those of buried animals. The increase in scaphognathite rates associated with the buried condition may be shown to be due to the gill ventilation system adopted by buried animals. 相似文献
49.
Buried Crangon crangon (L.) produce, anterior to their gill chambers, an inhalant and exhalant channel in the substratum. The combined shape and disposition of the maxillipeds effects separation of the inhalatory and exhalatory streams, and this channelling allows the maintenance of a posteroanteriorly directed flow of water over the gills of buried animals.Impedance techniques have been used to obtain qualitative data on the movements of scaphognathites. Reversals were identified and seen to occur particularly during burying and at the onset of walking. Reversals begin by the anterior region of the scaphognathite missing a beat, and end with the middle and anterior regions pausing.Analyses of movement patterns of individual scaphognathites show that a beat comprises equally-effective depression levation phases, but the timing sequence of the movements differs slightly from that reported in Carcinus maenas. 相似文献
50.