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541.
Summary Microfibrils composed of mannan have been shown to occur in the cells walls of the green algae Codium fragile and Acetabularia crenulata. Unlike cellulosic microfibrils, these structures were exceedingly sensitive to the usual physical and chemical procedures used for isolating cell walls, and were preserved in electron microscope preparations only when mild treatments were employed. 相似文献
542.
Mannan-rich plant cell walls were mechanically disintegrated and chemically extracted in order to ascertain their morphology and structure by electron microscopy and electron diffraction. For Acetabularia crenulata and Codium fragile, the cell-wall fragments were found to consist of alkali-resistant fibrillar mannan II encrusted with alkali-soluble granular mannan I. In the case of ivory nuts (Phytelephas macrocarpa) there is, in addition, a microfibrillar cellulose component which was also identified. The mannan I—mannan II polymorphism was also obtained when various mannan fractions were recrystallized from solution. In these recrystallizations, the occurrence of one or the other polymorph was found to depend on several parameters: the molecular weight of the mannan, the temperature of crystallization and the polarity of the crystallization medium.Abbreviations DP
degree of polymerization
- EDTA
ethylenediaminetetraacetic acid
Affiliated with the Scientific and Medical University of Grenoble 相似文献
543.
544.
By using the fluorescence enhancement of ethidium bromide when it binds to RNA, a very rapid, simple and sensitive assay for the concentration of ribosomal RNA in complex mixtures has been devised. 相似文献
545.
Semi-quantitative estimation of the composition of alginates by infra-red spectroscopy 总被引:3,自引:0,他引:3
W. Mackie 《Carbohydrate research》1971,20(2):413-415
546.
The influence of nature of the feed sample, feeding frequency and pore size on the influx of bacteria and protozoa into synthetic fiber bags suspended in the rumens of sheep fed different diets was studied. Counts of total culturable bacteria in bags with a pore size of 10 microns were less than 30% of the ruminal counts for animals that were fed the lucerne hay and high-roughage diets. The maximum count (62 and 82% of the ruminal count) for these specific diets was obtained by using bags with a pore size of 53 microns. Protozoal counts in bags with pore sizes of 30 and 53 microns were equal to or higher than the ruminal counts for the lucerne hay and high-roughage diets but less than half of the ruminal count for the low-roughage diet. An interaction between incubation time, feeding frequency of the host animals, and the microbial populations developing inside the bags was also demonstrated. The results clearly show that the microbial population inside the bag differed from that of the surrounding ruminal ingesta and that caution must be taken in interpreting results on feed evaluation and especially on rates of degradation when using the in sacculus technique. Factors influencing the influx of bacteria and protozoa into bags with different pore sizes and containing a variety of substrates are discussed together with suggestions for the use of this technique. 相似文献
547.
A I Mitchell A M Mackie 《Comparative biochemistry and physiology. A, Comparative physiology》1983,75(3):471-474
Reversible specific binding of [14C]inosine has been demonstrated in turbot (Scophthalmus maximus) buccal tissues rich in taste buds. A highly significant correlation was found for a series of nucleosides and nucleotides between their feeding stimulant activity and their ability to displace bound [14C]inosine. It is concluded that the binding of inosine is the first step in the gustatory process. 相似文献
548.
D S Riddick J E Mackie T E Massey G S Marks 《Canadian journal of physiology and pharmacology》1990,68(3):370-373
Various rat liver cytochrome P-450 (P-450) isozymes are targets for mechanism-based inactivation by 3,5-diethoxycarbonyl-2,6-dimethyl-4-ethyl-1,4- dihydropyridine (4-ethyl DDC). Unlike rat liver, which contains multiple P-450 isozymes, rabbit lung contains only three major isozymes referred to as forms 2, 5, and 6. We have examined the ability of 4-ethyl DDC to destroy P-450 heme in hepatic and pulmonary microsomes from untreated and beta-naphthoflavone (beta NF)-treated rabbits. This compound destroyed 31% of the P-450 in either hepatic microsomal preparation, but was ineffective at lowering P-450 and heme levels in pulmonary microsomes when examined at a range of concentrations (0.45-5.0 mM). These data suggest that rabbit pulmonary P-450 forms 2, 5, and 6 are not targets for destruction by 4-ethyl DDC, despite the ability of this compound to inactivate rat liver P-450c, the orthologue of rabbit lung form 6. 相似文献
549.
Silver stained Cordylophora were examined by light and electron microscopy, which provided a general picture of nerve cell forms and distribution for comparison with electron micrographs of osmium-fixed tissues from the same hydroid. Muscle, nerve and neurosensory components were studied in the nectophore of Nanomia (O. Siphonophora) and in the hydromedusae Sarsia and Euphysa by means of vital staining and optical and electron microscopy of epon sections; particular attention was given to relationships and interconnections between the cellular elements of the two marginal nerve rings. Mitochondrial size, numbers and types of vesicles and the occurrence of neurotubules and of parts of sensory cilia may provide useful ultrastructural clues for recognizing nerve elements, but serial sections are often needed to make identification conclusive. In Cordylophora and Nanomia, some neurites contain massed A vesicles (membrane-bounded dense granules) suggestive of neurosecretion (cf. reports on Hydra). However, a small type of A vesicle also occurs at synapses in Sarsia, indicating a probable role here in junctional transmission. Vesicles occur on both sides of some synapses (as previously reported for Cyanea) but on one side only in others, these being the first examples of polarized junctional ultrastructure in coelenterates. 相似文献
550.