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51.
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The gene (alyVI) encoding an alginate lyase of marine bacterium Vibrio sp. QY101, which was isolated from a decaying thallus of Laminaria, was cloned using a strategy of combined degenerate PCR and long range-inverse PCR (LR-IPCR), then sequenced and expressed in Escherichia coli. Gene alyVI was composed of a 1014 bp open reading frame (ORF) encoding 338 amino acid residues. The calculated molecular mass of alyVI product is 38.4 kDa, but a signal peptide is cleaved off, leaving a mature protein of 34 kDa. AlyVI was purified from culture supernatants to electrophoretic homogeneity using affinity chromatography. AlyVI was most active at pH 7.5 and 40 degrees C in the presence of 1 mM ZnCl2. A nine-amino-acid consensus region (YXRESLREM), which was only found in polyguluronate lyases, was also observed in the amino-terminal region of AlyVI. However, AlyVI could degrade both M block and G block. These results indicate that a novel alginate lyase-encoding gene has been cloned. 相似文献
53.
Torsten Müller Stefan Fiedler Thomas Schnelle Kai Ludwig Hartmut Jung Günter Fuhr 《Biotechnology Techniques》1996,10(4):221-226
Summary Combining dielectrophoretic and hydrodynamic forces in micro electrode structures allows enrichment and stable trapping of viruses in aqueous solutions. Fluorescently labelled Influenza and Sendai viruses were collected from solutions of 2*105 – 2*108 viruses/l within a few seconds. In the central part of the trap a virus aggregate of about 2–9 m in diameter was formed. This corresponds to a local enrichment of viruses up to a factor of about 1400. 相似文献
54.
We studied the effect of egg presence on female mate choicein a fish with paternal care. Females who were allowed a freechoice between two males mated within a shorter time than femaleswho were randomly assigned to a particular male. When a secondfemale was allowed to choose among the males, she preferredthe same male as the previous female. This result shows thatfemales are concordant in their mate choice. When the initialfemale was randomly assigned to mate with one of two males (forcedchoice), the second female mated randomly with respect to thefirst one. Thus females do not prefer males with eggs. If theinitial female was given a free choice, but the eggs were removedfrom the chosen male, the test female mated randomly. When boththe males initially had mated but one randomly determined male'seggs were removed, the test female preferred the male who wasstill guarding eggs. These experiments show that females avoidspawning in unsuccessful nests. When the females in the freechoice/egg removal experiment mated with the unsuccessful malethere was a considerably bigger size difference in favor ofthis male than when the females mated with the other male. Weconclude that female sand gobies show clear mate preferences,but that they do not prefer males with eggs over males withouteggs. They do, however, avoid mating with males guarding unsuccessfulnests. We therefore suggest that egg loss could be an importantfactor selecting for egg preference. 相似文献
55.
Tibor Harrach Klaus Eckert Kai Schulze-Forster Rolf Nuck Detlef Grunow H. Rainer Maurer 《Journal of Protein Chemistry》1995,14(1):41-52
Crude bromelain extracts from pineapple stems (Ananas comosus) were fractionated by two-step FPLC-cation-exchange chromatography. At least eight basic proteolytically active components were detected. The two main components F4 and F5 together with the most active proteinase fraction F9 were characterized by SDS-PAGE, mass spectroscopy, multizonal cathodal electrophoresis, partial amino acid sequence, and monosaccharide composition analysis. F9 amounts to about 2% of the total protein and has a 15 times higher specific activity against the substratel-pyroglutamyl-l-phenylanalyl-l-leucine-p-nitroanilide (PFLNA) than the main component F4. The molecular masses of F4, F5, and F9 were determined to 24,397, 24,472, and 23,427, respectively, by mass spectroscopy. Partial N-terminal amino acid sequence analysis (20 amino acids) revealed that F9 differs from the determined sequence of F4 and F5 by an exchange at position 10 (tyrosineserine) and position 20 (asparagine glycine). F4 and F5 contained fucose, N-acetylglucosamine, xylose, and mannose in ratio of 1.02.01.02.0, but only 50% of the proteins seem to be glycosylated, whereas F9 was found to be unglycosylated. Polyclonal antibodies (IgG) against F9 detected F4 and F5 with tenfold reduced reactivity. ThepH optimum of F4 and F5 was betweenpH4.0 and 4.5 and for F9 close to neutralpH. The kinetic parameters for PFLNA hydrolysis were similar for F4 (K
m 2.30 mM,k
cat 0.87 sec–1 and F5 (K
m 2.42 mM,k
cat 0.68 sec–1), and differed greatly from F9 (K
m 0.40 mM,k
cat 3.94 sec–1).Dedicated to H. Tschesche, Bielefeld, Germany, on behalf of his 60th anniversary. 相似文献
56.
Novel DNA binding proteins highly specific to UV-damaged DNA sequences from embryos of Drosophila melanogaster. 总被引:1,自引:0,他引:1
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Three new proteins which selectively bind to UV-damaged DNA were identified and purified to near homogeneity from UV-irradiated Drosophila melanogaster embryos through several column chromatographies. These proteins, tentatively designated as D-DDB P1, P2 and P3, can be identified as different complex bands in a gel shift assay by using UV-irradiated TC-31 probe DNA. Analysis of the purified D-DDB P1 fraction by native or SDS-polyacrylamide gel electrophoresis and FPLC-Superose 6 gel filtration demonstrated that it is a monomer protein which is a 30 kDa polypeptide. The D-DDB P2 protein is a monopolypeptide with a molecular mass of 14 kDa. Both D-DDB P1 and P2 highly prefer binding to UV-irradiated DNA, and have almost no affinity for non-irradiated DNA. Gel shift assays with either UV-irradiated DNA probes demonstrated that D-DDB P1 may show a preference for binding to (6-4) photoproducts, while D-DDB P2 may prefer binding to pyrimidine dimers. Both these proteins require magnesium ions for binding. D-DDB P1 is an ATP-preferent protein. These findings are discussed in relation to two recently described [Todo and Ryo (1991) Mutat. Res., 273, 85-93; Todo et al. (1993) Nature, 361, 371-374] DNA-binding factors from Drosophila cell extracts. A possible role for these DNA-binding proteins in lesion recognition and DNA-binding proteins in lesion recognition and DNA repair of UV-induced photo-products is discussed. 相似文献
57.
58.
Crystallization and main-chain structure of neutral protease from Streptomyces caespitosus 总被引:1,自引:0,他引:1
A neutral protease, i.e., a zinc-containing metalloendoprotease from Streptomyces caespitosus, has been crystallized using acetone as a precipitating agent. The crystals diffract to better than 1.5 A resolution when a rotating anode X-ray generator is used as an X-ray source. Protein phase angles were calculated by the multiple isomorphous replacement method using two heavy-atom derivatives (HgCl2 and CH3HgCl). A 6 A resolution electron density map clearly showed molecular boundaries. Although its amino acid sequence is not known, the folding pattern of the polypeptide chain could be traced on a 2.5 A resolution electron density map. A large cleft, which is located on the molecular surface, was proved to be the active site of the enzyme by structure analyses of inhibitor-complex crystals. The highest electron density peak, which corresponds to the cleft, was assigned to a catalytically essential zinc atom on difference Fourier synthesis between native and EDTA-soaked crystals. 相似文献
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60.