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Gracjana Klein Robert Walczak Ewa Krasnowska Adam Blaszczak Barbara Lipiska 《Molecular microbiology》1995,16(4):801-811
We have investigated heat-shock response in a marine bacterium Vibrio harveyi. We have found that 39 C was the highest tempature at which V. harveyi was able to grow steadily. A shift from 30° C to 39° C caused increased synthesis of at least 10 proteins, as judged by SDS-PAGE, with molecular masses of 90, 70, 58, 41, 31, 27, 22, 15, 14.5 and 14kDa. The 70, 58, 41 and 14.5 kDa proteins were immunologically homologous to DnaK, GroEL, DnaJ and GroES heat-shock proteins of Escherichia coli, respectively. V. harveyi GroES protein had a lower molecular mass (14.5 kDa) than E. coli GroES, migrating in SDS-PAGE as 15 kDa protein. We showed that a protein of ~43 kDa, immunologically reactive with antiserum against E. coli sigma 32 subunit (σ32) of RNA polymerase, was induced by heat-shock and co-purified with V. harveyi RNA polymerase. These results suggest that the 43 kDa protein is a heat-shock sigma protein of V. harveyi. Preparation containing the V. harveyi sigma 32 homologue, supplemented with core RNA polymerase of E. coli, was able to transcribe heat-shock promoters of E. coli in vitro. 相似文献
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Cross-correlation histograms (CCH) were computed for discharge sequences of pairs of motoneurones which were excited by sinusoidal muscle stretches. These CCH's were compared before and after opening of the recurrent inhibitory loop by Renshaw cell blocking agents. Periodic patterns in the CCH's indicative of specifically timed phase relations between discharges of different motoneurones were enhanced after Renshaw cell blockage. This was confirmed by power spectra computed for the CCH's. They contained power peaks about 50Hz which tended to increase after depression of recurrent inhibition. The correlation was thus due predominantly to line current interference which seemed to act as a common entrainment input at the spinal level. It is concluded that Renshaw cells de-correlate discharge patterns of different motoneurones of the same pool by injecting uncorrelated signals into them. This de-correlation is an important prerequisite for distortion suppression of signal transmission in a multi-channel system, like that of stretch reflex, and for its linearization. 相似文献
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In order to determine the significance of the C-6 carboxyl group for the biological activity gibberellin A3, 6-epigibberellin A3, 7-norgibberellin A3, 6-methyl-7-norgibberellin A3, and 7-homogibberellin A3 were studied using dwarf pea, dwarf maize, dwarf rice, dwarf barley and -amylase bioassays. All gibberellin A3(GA3)derivatives tested were considerably less active than GA3. In all biossays, 6-epi-GA3 showed a low activity of the same order, whereas 6-methyl-7-nor-GA3 was inactive. Surprisingly, 7-nor-GA3 had some activity in the dwarf rice (root application), dwarf barley, and -amylase bioassay, in contrary to its low potency in the dwarf pea, dwarf maize, and dwarf rice (micro drop) bioassay. 7-Homo-GA3 was primarily active in the dwarf maize, dwarf barley and dwarf rice bioassay. It also caused antigibberellin effects in dwarf rice. The results demonstrate that the C-6 carboxyl group is not absolutely essential for biological activity of gibberellins. The different activities of 7-nor-GA3 observed in the various test systems may indicate that the C-6 carboxyl group is a structural requirement more for uptake and/or transport processes than for receptor affinity.Abbreviation GA3
gibberellic acid 相似文献
127.
A technique for the preparation of microgram quantities of bovine parathyroid hormone (bPTH) labeled with carrier-free 125I to a specific activity of 1300 Ci/mmol is described. A restructured and simplified apparatus was used for electrolytic iodination, making it feasible to use reaction volumes of 100 to 200 ml. The miniaturized setup requires only a small platinum crucible connected via an agar-KCl salt bridge to a saturated KCl solution, a battery to drive the reaction, and a voltmeter to monitor the potential difference between the reference-saturated KCl solution (via a calomel electrode) and the platinum crucible. The [125I]-labeled bPTH elutes as a single species when chromatographed on a Biogel P-10 column equilibrated in 3 m guanidine HCl-2.3 m formic acid, and it retains full biologic activity when bioassayed in vivo. It is evident that bPTH labeled to a high specific activity with 125I does not suffer in regard to its biological potency. 相似文献
128.
Gretchen Kurpiewski Lawrence J. Forrester James T. Barrett Benedict J. Campbell 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,678(3):467-476
A facile and quantitative assay for measuring the activity of sphingomyelinase D in recluse spider venom has been developed using L-α-[palmitoyl-1-14C]lysophosphatidylcholine as substrate. This assay avoids the problem of substrate insolubility that occurs when sphingomyelin and other lipids are used as subtrates. This assay has been employed in gel filtration and isoelectric focusing isolation techniques to purify sphingomyelinase D from spider venom. The purified sphingomyelinase exhibits four active enzyme forms in isoelectric focusing with pI values of 8.7, 8.4., 8.2, and 7.8. Each active form when examined in SDS-polyacrylamide gel electrophoresis gave an estimated molecular weight of 32 000. The four active enzyme forms were immunologically cross-reactive with each other as demonstrated with radioimmune assays using an antiserum developed to one of the active forms. Each active form hydrolysed sphingomyelin to release choline and produce N-acylsphingosine phosphate. One of the active enzyme forms was characterized further in dermonecrosis and platelet aggregation measurements. This purified sphingomyelinase D was identified as a poisonous toxin that can develop the typical dermonecrotic spider lesion when injected into experimental animals at levels expected to be delivered in a normal bite. Furthermore, the purified toxin acts to aggregate human blood platelets. The toxin-induced platelet aggregation has been related to serotonin release as aggregation occurs, and it has been shown to be inhibited by EDTA over the range of 0.6 to 3.0 mM EDTA. It is suggested that spider-induced dermonecrosis could result in part from platelet aggregation at and near the site of envenomation. 相似文献
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