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排序方式: 共有433条查询结果,搜索用时 15 毫秒
1.
2.
Gerard Strecker Jean-Michel Wieruszeski Jean-Claude Michalski Jean Montreuil 《Glycoconjugate journal》1988,5(4):385-396
The structure of a new nonasaccharide isolated from human milk has been investigated. By using methylation analysis, FAB-MS and1H-and13C-NMR spectroscopy as basic methods of structural investigation, this oligosaccharide was identified as VI2--Fuc,V4-Fuc,III3--Fuc-p-lacto-n-hexaose: Fuc1-2Gal1-3[Fuc1-4]GlcNAc1-3Gal1-4[Fuc1-3]GlcNAc1-3Gal1-4Glc.Abbreviations COSY
correlation spectroscope
- DP
degree of polymerisation
- FAB-MS
fast atom bombardment-mass spectrometry
- HPLC
high performance liquid chromatography
- NMR
nuclear magnetic resonance
- GLC
gas-liquid chromatography 相似文献
3.
The time delay of oxygen probe response to the signal from a fermenter makes identification of the volumetric oxygen transfer coefficient kLa by the dynamic method more complicated. A coupled model involving the transient-state oxygen balance of the fermenter together with the dynamic model of the oxygen probe must be then formulated, solved and identified. In this paper two simple models of air-lift loop fermenters have been proposed and a coupled mathematical model of the fermenter – oxygen probe system has been developed. The identification procedure was used to estimate kLa values in the fermenter with internal circulation flow on the basis of experimental measurements. A comparison of evaluated and experimental indications of the probes placed at various heights of the column proves that the model presented gives a possibility of the first-step approximation of kLa in loop fermenters. 相似文献
4.
T Baussant G Strecker J M Wieruszeski J Montreuil J C Michalski 《European journal of biochemistry》1986,159(2):381-385
An endo-N-acetyl-beta-D-glucosaminidase active towards oligosaccharides with a reducing terminal [bis(N-acetylglucosamine)]residue has been characterized in rat liver. The primary structure of its reaction products was determined using high-resolution 1H-NMR spectroscopy. The enzyme is predominantly located in the lysosomal fraction, presents a maximum of activity at pH 3.5 and is completely inactive towards conjugated glycans, i.e. glycoproteins and glycopeptides as well as on glycoasparagines. These results support the existence of a new pathway for the degradation of glycoprotein glycans inside the lysosome. In particular, this enzymic activity may be the origin of oligosaccharides bearing a single terminal reducing N-acetylglucosamine residue which are excreted in the urine of patients with various exoglycosidase deficiencies. 相似文献
5.
Properties of human liver lysosomal sialidase 总被引:3,自引:0,他引:3
Sialidase in human liver was localized predominantly in the lysosomal fraction. Microsomal and nuclear fractions contained some activity but no cytosolic enzyme could be detected. The lysosomal enzyme fraction is active with gangliosides, fetuin, mucus glycoprotein, sialyllactose and other sialyloligosaccharides. The preferred rate of enzymic hydrolysis of sialyl linkages is alpha(2-3) greater than alpha(2-6) greater than alpha(2-8) and this is governed by the Vmax values, as Km values were similar for all substrates tested. N-Acetyl-neuraminic acid is released faster than N-glycoloylneuraminic acid. Using the inhibitors N-acetyl-2-deoxy-2,3-didehydroneuraminic acid and N-(4-nitrophenyl)oxamic acid with selected substrates the existence of at least two types of sialidase activity could be demonstrated. One is active preferentially with gangliosides and sialyllactose and the other with fetuin and sialyhexasaccharides. Strong inhibition by Cu2+ and Hg2+ was found with ganglioside and sialyllactose as substrates. The presence of a sialate O-acetylesterase acting on hematoside containing N-glycoloyl-4-O-acetylneuraminic acid was established. 相似文献
6.
J C Michalski J Montreuil G Strecker H van Halbeek L Dorland J F Vliegenthart B Cartigny J P Farriaux 《European journal of biochemistry》1983,132(2):375-381
Initial-rate measurements were made of the reduction of pyridine-3-aldehyde and p-carboxybenzaldehyde by NADPH catalyzed by pig liver aldehyde reductase I. The initial velocity analysis and product inhibition data suggest that aldehyde reductase I obeys a compulsory-order mechanism with pyridine-3-aldehyde as substrate but follows a partially random-order pathway with p-carboxybenzaldehyde. The partially random-order pathway would be operative only at high concentrations of p-carboxybenzaldehyde. In both cases, aldehydes and the corresponding alcohol substrates inhibit the enzyme at high concentration. Abortive ternary complexes are shown to be formed with pyridine-3-aldehyde and with p-carboxybenzaldehyde. Dissociation of the coenzyme from the abortive ternary complex seems only to be observed with p-carboxybenzaldehyde. This study suggests overall that an enzyme kinetic mechanism may be different, depending on whether specific interactions can occur between certain amino acid residue(s) of the protein active site and substrates. Finally, the mechanism of the inhibition of pyridine-3-aldehyde reduction by diacid derivatives is discussed. 相似文献
7.
Eight cylindrical enclosures (3 m diameter, 2.7 m long, V = 20m3) were installed in eutrophic Rice Lake (Ontario, Canada) in late spring of 1987. Fish (yearling yellow perch (Perca flavescens) and macrophytes (Potamogeton crispus) presence and absence were set at the beginning of the experiment to yield four combinations of duplicate treatments. The purpose of the experiment was to determine if the phytoplankton, zooplankton, macrophytes and fish species resident in the lake interact to influence water quality (major ions, phosphorus, algal densities and water clarity).The presence of fish was associated with: (1) decreased biomass of total zooplankton, (2) decreased number of species in the zooplankton, (3) decreased average size of several zooplankton taxa, (4) higher total phosphorus concentrations, (5) higher phytoplankton and chlorophyll a concentrations, (6) lower water clarity, (7) lower potassium levels during macrophyte die-back, (8) lower pH and higher conductivity in the presence of macrophytes. Biomass of large Daphnia species (but not total zooplankton) was highly correlated with the algal response (r
2 = 0.995) and was associated with reduced biomass of several algal taxa including some large forms (Mougeotia, Oedogonium) and several colonial blue-green algae. However, no significant control of late summer growth of the bloom-forming blue-green alga Anabaena planctonica Brun. was achieved by the Daphnia presence-fish absence treatment. Release of phosphorus to the water column during the die-back of P. crispus was not an important phenomenon. 相似文献
8.
Abstract: Changes of the main hydrodynamic and oxygen transfer parameters during Aspergillus niger cultivation in an external-loop air-lift bioreactor of 200 dm3 operating capacity were investigated. The final average concentrations of biomass and citric acid obtained in batch fermentations were about 17 g 1-1 and 90 g 1-1 , respectively. Significant influence of the increasing biomass concentration on the rheological properties of the broth and operating parameters was found. Volumetric oxygen transfer coefficient. k L a , was found to be dependent on the apparent viscosity of the broth with an exponent of -0.984. 相似文献
9.
10.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献