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931.
db—cAMP对转化细胞钙调素基因表达与细胞骨架的影响 总被引:5,自引:0,他引:5
We have demonstrated that the distribution of microtubules (MT), microfilaments (MF) and fibronectin (FN) were diminished, while the gene expression of the calmodulin and c-fos enhanced in the transformed C3 H10 T1/2 cells. After treatment with 1 mM db-cAMP for 1 hr. and 2 hrs., there was an early and rapidly reduced in gene expression of calmodulin and c-fos respectively. After db-cAMP treatment for 4-5 days, the number of Capping cells of ConA binding decreased significantly and the cell surface microvilli decreased also. The growth of treated cells was inhibited markedly. By using 4F1 cDNA probe, which is preferentially expressed in G1 phase, we have found that the db-cAMP treated cells were accumulated at G1 phase. Of particular interest is the fact that the distribution of microtubules, microfilaments and fibronectin were recovered after treatment with 1 mM db-cAMP for 6 days. It is suggested that the inhibition of proliferation, alteration of phenotype and recovery of cytoskeleton in transformed cells after treatment with db-cAMP are related to the inhibition of gene expression of calmodulin. 相似文献
932.
This paper makes an analysis and study on altogether 8 palyniferous samples from the volcano-sedimentary rock series in the Half Three Point area of the Fildes Peninsula, King George Island, Antarctica, the rock series being grey tuffaceous siltstone in lithological characters, about 5m in thickness. Only after making a number of analyses, could we find the relatively abundant sporopollen fossils from 4 samples (Nos. GWP 4—7). But the fossils are poorly preserved, and most of them can hardly be identifi... 相似文献
933.
Two strains which belong to the same serotype of Shigella were isolated from the bloody-pus stool of two patients (in 1986) and is reported in this paper. The results were identical both showing agglutination in low titer with serotype 8 of S. dysenteriae and serotype 4 of S. boydii when the two strains were checked well with all kinds of diagnostic antisera and vice versa, ie the antisera produced by the two strains were also checked well with sera prepared with the representative strains of all Shigella spp. No cross agglutination with O6, O7, and O150 of E. coli were found. Consequently, It appears to be a new serotype of Shigella. These two strains possess the ability of causing keratitis in guinea-pigs as well as invading epithelial cells, the DNA of both strains in agarose-electrophoresis showed a large plasmid, indicating that they are virulent strains possessing invasive ability. It was concluded that these two strains belonged to Shigella boydii as they fermented mannitol and non-related antigenically with Shigella flexneri. Since serotype 1-18 of S. boydii have been reported recently, we propose that this new serotype should be serotype 19 of Shigella boydii. 相似文献
934.
We examined various media and conditions to isolate symbiotic cyanobacteria from the leaf cavities of Azolla spp. Cyanobacteria survived and multiplied to a limited extent on a medium with fructose, Casamino Acids, yeast extract, and NaNO3 under 1% O2. These cyanobacteria were antigenically identical to the endosymbionts. 相似文献
935.
Stopped-flow ESR study on the reactivity of vitamin E, vitamin C and its lipophilic derivatives towards Fremy's salt in micellar systems 总被引:1,自引:0,他引:1
The reaction between Fremy's salt and alpha-tocopherol (VE), ascorbic acid (VC) and its lipophilic derivatives ascorbyl-6-caprylate (VC-8), 6-laurate (VC-12) and 6-palmitate (VC-16) were studied by stopped-flow ESR spectroscopy in cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) micelles, as a model reaction of these antioxidants with alkyl peroxy radicals in biological systems. The second order rate constants for the reaction of Fremy's salt with VE in CTAB and SDS micelles were found to be 7.9 x 10(3) and 2.2 M-1 s-1, respectively, with as high as a 3600-fold variation. Rate constants for VC, VC-8, VC-12 and VC-16 are 4.3, 35, 53 and 56 x 10(3) M-1 s-1 and 3.3, 2.7, 1.2 and 0.86 x 10(3) M-1 s-1 in CTAB and SDS micelles, respectively. The results demonstrate remarkable effects of the charge type of the micelles and the side-chain of the antioxidants on the antioxidation reactivity in the micelles. It reveals that the inter-micellar diffusion may be the rate-limiting step for antioxidation carried out in micelles. 相似文献
936.
Recognition sites of eukaryotic DNA topoisomerase I: DNA nucleotide sequencing analysis of topo I cleavage sites on SV40 DNA. 总被引:29,自引:18,他引:11 下载免费PDF全文
Eukaryotic DNA topoisomerase I introduces transient single-stranded breaks on double-stranded DNA and spontaneously breaks down single-stranded DNA. The cleavage sites on both single and double-stranded SV40 DNA have been determined by DNA sequencing. Consistent with other reports, the eukaryotic enzymes, in contrast to prokaryotic type I topoisomerases, links to the 3'-end of the cleaved DNA and generates a free 5'-hydroxyl end on the other half of the broken DNA strand. Both human and calf enzymes cleave SV40 DNA at the identical and specific sites. From 827 nucleotides sequenced, 68 cleavage sites were mapped. The majority of the cleavage sites were present on both double and single-stranded DNA at exactly the same nucleotide positions, suggesting that the DNA sequence is essential for enzyme recognition. By analyzing all the cleavage sequences, certain nucleotides are found to be less favored at the cleavage sites. There is a high probability to exclude G from positions -4, -2, -1 and +1, T from position -3, and A from position -1. These five positions (-4 to +1 oriented in the 5' to 3' direction) around the cleavage sites must interact intimately with topo I and thus are essential for enzyme recognition. One topo I cleavage site which shows atypical cleavage sequence maps in the middle of a palindromic sequence near the origin of SV40 DNA replication. It occurs only on single-stranded SV40 DNA, suggesting that the DNA hairpin can alter the cleavage specificity. The strongest cleavage site maps near the origin of SV40 DNA replication at nucleotide 31-32 and has a pentanucleotide sequence of 5'-TGACT-3'. 相似文献
937.
薄鳞鱼类化石的新发现及其地层意义 总被引:2,自引:1,他引:1
本文记述了薄鳞鱼类(leptolepids)一新属新种——罗家峡隆德鱼(Longdeichthys luojiaxiaensis gen.et sp.nov.)。它和广泛分布于我国北方的另一原始真骨鱼类狼鳍鱼(Lycoptera)共生。因而,为研究真骨鱼类的演化和确定我国北方中生代含鱼岩系的时代及地层对比上,提供了新的资料。 相似文献
938.
Intra- and intermolecular strand transfer by HeLa DNA topoisomerase I 总被引:27,自引:0,他引:27
B D Halligan J L Davis K A Edwards L F Liu 《The Journal of biological chemistry》1982,257(7):3995-4000
939.
On the Nature of the Interaction Between Serotonin and Serotonin Binding Protein: Effect of Nucleotides, Ions, and Sulfhydryl Reagents 总被引:5,自引:2,他引:3
Abstract: Rat brain serotonin binding protein (SBP) was found to have essential -S-S and -SH groups. Both reduction of the disulfide bond by dithiothreitol or mercaptoethanol and modification of -SH group(s) by Ellman reagent or alkylating agents caused loss of binding capacity. In contrast, formation of a mixed disulfide bond with sodium metabisulfite did not affect the binding capacity. Serotonin in the presence of Fe2+ and phosphate was found to bind to either an -SH group or to a site in very close proximity. Addition of serotonin protected -SH groups from modification by Ellman reagent and from denaturation of protein upon storage. Lipids that enhance binding of serotonin to SBP also protected -SH groups from modification. Nucleotides were found to be strong inhibitors of the binding of serotonin to SBP. The inhibitory effect of nucleotides was due to their chelating properties and not to their ability to phosphorylate the protein or to bind directly to it. Inhibition by nucleotides and other chelators was reversible. Binding capacity was fully restored after removal of the chelator by molecular sieve chromatography and addition of Fe2+. The ionic environment had a marked effect on the binding: intracellular ions such as K+ were found to enhance the binding, and extracellular ions such as Na+ and Ca2+ inhibited the binding. Based on these data and our previous studies, we suggest that SBP is an intracellular protein that acts as a storage protein. Consistent with our data is formation of a complex of SBP-S-Fe-S that in a hydrophobic surrounding could bind up to four molecules of serotonin in coordination bond with Fe2+ and thereby reduce the osmotic pressure within a storage vesicle. Extracellular ionic conditions that favor the dissociation of the complex would free the amine to interact with its receptor or the presynaptic reuptake carrier. 相似文献
940.
S S Chen J W Bohn F T Liu D H Katz 《Journal of immunology (Baltimore, Md. : 1950)》1981,127(1):166-173