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排序方式: 共有374条查询结果,搜索用时 15 毫秒
1.
Ken Walder Carolyn R. Dascaliuc Paul A. Lewandowski Andrew J. Sanigorski Paul Zimmet Greg R. Collier 《Obesity (Silver Spring, Md.)》1997,5(3):193-200
Food intake was restricted to 75% of ad libitum levels in 37 male Psammomys obesus (Israeli Sand Rats) from the ages of 4 (weaning) to 10 weeks. Energy restriction reduced the mean body weight at 10 weeks by 29% compared with 44 ad libitum fed controls. Hyperglycemia was prevented completely in the food-restricted group, and mean blood glucose concentrations were significantly reduced (3.8 ± 0.2 vs. 5.5 ± 0.4 μmol/L; p<0.05) compared with control animals. Plasma insulin concentrations were also decreased significantly compared with ad libitum fed controls (105 ± 13 vs. 241 ± 29 mU/L;p<0.05). Although energy restriction prevented hyperglycemia from developing in 10-week-old P. obesus, 19% of the food restricted animals still developed hyperinsu-linemia. We concluded that hyperphagia between the ages of 4 to 10 weeks may be essential for the development of noninsulin-dependent diabetes mellitus in P. obesus, but that hyperinsulinemia may still occur in the absence of hyperphagia and hyperglycemia, suggesting a significant genetic influence on the development of hyperinsulinemia in this animal model. 相似文献
2.
Characterization of the Subunit Structure of the Ribonucleic Acid Genome of Influenza Virus 总被引:18,自引:12,他引:6
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Ribonucleic acid extracted from influenza virus was labeled at the 3' termini with (3)H and analyzed by polyacrylamide gel electrophoresis. Influenza virus was found to contain a minimum of seven and possibly as many as 10 polynucleotide chains, most of which appear to terminate at the 3' end in uridine. 相似文献
3.
Isolation and characterization of a large,neurite-associated glycoconjugate from neuroblastoma cells
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A high molecular weight glycoconjugate has been isolated from neurite-producing neuronal tumor cells in culture and has been designated as I(0) based on its elution characteristics in gel filtration chromatography. This molecule cannot be found in a variety of nonneuronal cells. I(0) is found in the substratum-attached material or cell fraction of neurite-producing neuroblastoma cells, depending upon culture conditions. It is found in the substratum-bound fraction of B104 rat neuroblastoma cells during serum starvation and in the EGTA-detached cell fraction of B104 cells grown in chemically defined N2 medium. It occurs only in the cell fraction of the human neuroblastoma line Platt. Examination of behavioral variants of the B104 rat line further strengthens the association of I(0) with neurite production; the constitutive neurite-producing E(R)B9 variant contains I(0) while the non-neurite-producing E(R)A11 variant does not. I(0) is large, eluting in the void volume of sepharose-CL2B columns. Radioiodination of intact cells with lactoperoxidase shows I(0) to be a cell surface component. Metabolic radiolabeling studies show that it contains a high proportion of polysaccharide to protein, does not contain mannose, and is unsulfated. Alkaline borohydride reduction release two size classes of large polysaccharide chain. The alkaline reduction results, along with the mannose incorporation studies, show the presence of O-glycosidic linkages and few, if any, N-linkages. Resistance to nitrous acid deamination, insensitivity to glycosaminoglycan lyases, and the absence of sulfation, indicate that I(0) does not contain the glycosaminoglycans hyaluronic acid, chondroitin-, dermatan-, or heparin- sulfates. Affinity column chromatography reveals high binding affinity of I(0) to polyornithine and no binding to gelatin (collagen) or the glycosaminoglycans hyaluronate and heparin. These studies describe a unique high molecular weight glycoconjugate on the surface of neurite-producing neuroblastoma cell lines from two species. 相似文献
4.
5.
The effect of the insecticides, mirex and chordecone (Kepone), on the cytochrome P-450 monooxygenase system in C57BL/6N mouse liver microsomes was studied. Mice were treated intraperitoneally with low (6 mg/kg) and high (30 mg/kg) doses of mirex and chlordecone in corn oil for 2 days. For comparison, mice were also treated with either phenobarbital (PB) or 3-methylcholanthrene (3-MC). All treatments significantly increased the hepatic microsomal P-450 content over that of controls. Benzphetamine N-demethylase, ethoxyresorufin O-deethylase, benzo[a]pyrene hydroxylase, and acetanilide hydroxylase activities were also determined. Mirex and chlordecone resembled phenobarbital with respect to the induction of monooxygenase activities. Immunoquantitation with antibodies to purified P-450 IIB1 (Pb-induced P-450) and P-450 IA1 (3-MC-induced P-450) indicated that mirex and chlordecone induced P-450 IIB1 in a dose-dependent manner. The high dose of mirex also induced a small amount of a protein cross reacting with the antibody to IA1. The induction of this isozyme did not, however, contribute significantly to the monooxygenase activities measured. 相似文献
6.
Margaret Lewandowski Y. C. Chui Patricia E. Levi Ernest Hodgson 《Journal of biochemical and molecular toxicology》1990,5(1):47-55
Eight methylenedioxyphenyl (MDP) compounds were examined for their ability to induce cytochrome P450 (P450) in mouse liver. Induction by safrole, isosafrole, and dihydrosafrole was studied in both C57BL/6N (Ah-responsive) and DBA/2N (Ahnonresponsive) male mice after IP administration of 200 mg/kg/day MDP compound for 3 days. Hepatic P450 content, ethylmorphine N-demethylase, ethoxy-resorufin O-deethylase, and acetanilide hydroxylase activities were induced to the same extent in both strains of mice. Benzo(a)pyrene hydroxylase activity, however, was not induced in either C57 or DBA mice. The similarity of results in both strains of mice indicated induction of these P450 isozymes by these three MDP compounds is not mediated by the Ah receptor. Induction of P450 by butylbenzodioxole (n-butyl-BD), tertiarybutylbenzodioxole (t-butyl-BD), methylbenzodioxole (methyl-BD), nitrobenzodioxole (nitro-BD), and bromobenzodioxole (bromo-BD) was examined only in C57BL/6N mice. Methyl-BD, nitro-BD, and bromo-BD did not induce hepatic microsomal proteins or selected P450 monooxygenase activities. In contrast, n-butyl-BD, and t-butyl-BD induced P450 content, ethylmorphine N-demethylase, acetanilide hydroxylase, and ethoxyresorufin O-deethylase activities. Benzo(a)pyrene hydroxylase was not induced by any of the treatments. Induction of these P450 activities is consistent with induction of P450 IIB1 and P450 IA2, but not induction of P450 IA1. Western blot analysis with antibodies to P450 isozymes induced with either phenobarbital (Pb) or 3-methylcholanthrene (3-MC) confirmed that both IIB1 and IA2 were induced, but that IA1 was not induced. 相似文献
7.
Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal 总被引:10,自引:9,他引:1
We have developed a new approach to the measurement of phylogenetic signal
in character state matrices called relative apparent synapomorphy analysis
(RASA). RASA provides a deterministic, statistical measure of natural
cladistic hierarchy (phylogenetic signal) in character state matrices. The
method works by determining whether a measure of the rate of increase of
cladistic similarity among pairs of taxa as a function of phenetic
similarity is greater than a null equiprobable rate of increase. Our
investigation of the utility and limitations of RASA using simulated and
bacteriophage T7 data sets indicates that the method has numerous
advantages over existing measures of signal. A first advantage is
computational efficiency. A second advantage is that RASA employs known
methods of statistical inference, providing measurable sensitivity and
power. The performance of RASA is examined under various conditions of
branching evolution as the number of characters, character states per
character, and mutations per branch length are varied. RASA appears to
provide an unbiased and reliable measure of phylogenetic signal, and the
general approach promises to be useful in the development of new techniques
that should increase the rigor and reliability of phylogenetic estimates.
相似文献
8.
Liquid flow in heterogeneous biofilms 总被引:10,自引:0,他引:10
Liquid flow was studied in aerobic biofilms, consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. Fluorescein microinjection was used as a qualitative technique to determine the presence of flow in cell clusters and voids. Flow velocity profiles were determined by tracking fluorescent latex spheres using confocal microscopy. Liquid was flowing through the voids and was stagnant in the cell clusters. Consequently, in voids both diffusion and convection may contribute to mass transfer, whereas in cell clusters diffusion is the dominant factor. The flow velocity in the biofilm depended on the average flow velocity of the bulk liquid. The velocity profiles in biofilms were linear and the velocity was zero at the substratum surface. The velocity gradients within biofilms were 50% of that near walls without biofilm coverage. The influence of the biofilm roughness on the flow velocity profiles was similar to that caused by rigid roughness elements. (c) 1994 John Wiley & Sons, Inc. 相似文献
9.
Molecular evolution of voltage-sensitive ion channel genes: on the origins of electrical excitability 总被引:14,自引:0,他引:14
We have analyzed nucleic acid and amino acid sequence alignments of a
variety of voltage-sensitive ion channels, using several methods for
phylogenetic tree reconstruction. Ancient duplications within this family
gave rise to three distantly related groups, one consisting of the Na+ and
Ca++ channels, another the K+ channels, and a third including the cyclic
nucleotide-binding channels. A series of gene duplications produced at
least seven mammalian homologues of the Drosophila Shaker K+ channel;
clones of only three of these genes are available from all three mammalian
species examined (mouse, rat, and human), pointing to specific genes that
have yet to be recovered in one or another of these species. The
Shaw-related K+ channels and the Na+ channel family have also undergone
considerable expansion in mammals, relative to flies. These expansions
presumably reflect the needs of the high degree of physiological and
neuronal complexity of mammals. Analysis of the separate domains of the
four-domain channels (Ca++ and Na+) supports their having evolved by two
sequential gene duplications and implies the historical existence of a
functional two-domain channel.
相似文献
10.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
相似文献