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971.
The Ca2+-binding properties of calmodulin purified from zucchini (Cucurbita pepo L.) has been determined. A value of 3.3 mol Ca2+ per mol of zucchini calmodulin was measured at pH 7.5 by equilibrium chromatography. The far-and near-UV circular-dichroic spectra of the Ca2+-and Mg2+-saturated as well as from the metal-free forms of zucchini calmodulin reveal that upon Ca2+-binding the -helix content increases. A comparison with the spectra of vertebrate calmodulin indicates that both calmodulin have a similar secondary structure, similar Ca2+-induced conformational changes and the same number of Ca2+-binding sites.Abbreviations CAPP
10-(3-aminopropyl)-2-chloro-phenothiazine
- EGTA
ethylene glycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid
- EDTA
ethylenediaminetetraacetic acid
Dedicated to Prof. Dr. Karl Decker on the occasion of his 60th birthday 相似文献
972.
Thylakoids isolated from peas (Pisum sativum cv. Kelvedon Wonder) and phosphorylated by incubation with ATP have been compared with non-phosphorylated thylakoids in their sensitivity to photoinhibition by exposure to illumination in vitro. Assays of the kinetics of fluorescence induction at 20° C and the fluorescence emission spectra at-196° C indicate a proportionally larger decrease in fluorescence as a result of photoinhibitory treatment of non-phosphorylated compared with phosphorylated thylakoids. It is concluded that protein phosphorylation can afford partial protection to thylakoids exposed to photoinhibitory conditions.Abbreviations and symbols DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
-
F
0
Level of chlorophyll fluorescence when photosystem 2 traps are open
-
F
m
Level of chlorphyll fluorescence when photosystem 2 traps are closed
- P
Maximum level of fluorescence reached in the absence of DCMU
- PSI (II)
photosystem I(II) 相似文献
973.
A radioimmunoassay, combined with high-performance liquid chromatography, has been used to analyse the zeatin-type cytokinins of potato (Solanum tuberosum L. cv. Majestic) tubers and tuber buds throughout growth and storage. During tuber growth, zeatin riboside was the predominant cytokinin detected in all tissues. Immediately after harvest, the total cytokinin concentration fell dramatically in the storage tissue, largely as a consequence of the disappearance of zeatin riboside. During storage, levels of cytokinins in the storage tissue remained relatively constant, but increased in the tuber buds. In the buds of tubers stored at 2°C there was a 20-to 50-fold increase in total cytokinin over six weeks, coinciding with the natural break of innate dormancy. At 10°C the rise in the level of bud cytokinins was slower, correlating with the longer duration of innate dormancy. Injecting unlabelled cytokinins into tubers in amounts known to induce sprouting gave rise to increases in cytokinin concentrations in the buds of the same order as the increase associated with the natural break of dormancy. Metabolism of injected cytokinins was greater in non-dormant than in dormant tubers. The roles of cytokinin concentration and the sensitivity of the buds to cytokinin in the control of dormancy are discussed.Abbreviations CK
cytokinin
- FW
fresh weight
- HPLC
high-performance liquid chromatography
- RIA
radioimmunoassay
- tio6ade
6-(4-hydroxy-3-methylbut-trans-2-enylamino)-purine=zeatin
- tio6adeglc9
6-(4-hydroxy-3-methylbut-trans-2-enylamino)-9--D-glucopyranosyl purine=zeatin-9-glucoside
- tio6ado
6-(4-hydroxy-3-methylbut-trans-2-enylamino)-9--D-ribofuranosyl purine=zeatin riboside
- tio6ado-[3H]-diol
a radioactive derivative of zeatin riboside, synthesised by periodate-oxidation followed by [3H]NaBH4-reduction
- tio6AMP
6-(4-hydroxy-3-methylbut-trans-2-enylamino)-9--D-5-phosphoribofuranosyl purine=zeatin riboside 5-monophosphate
- t(ioglc4)6ade
6-(4-O--D-glucopyranosyl-3-methylbut-trans-2-enylamino)-purine=zeatin-O-glucoside 相似文献
974.
The structure of spinach ribulose 1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) has been investigated by tilted-view electron microscopy of negatively stained monolayer crystals and image processing. The structure determined consists of a cylinder of octagonal cross-section with a large central hole. Based on this and other available evidence a model for the arrangement of the large and small subunits is suggested with the eight small subunits arranged equatorially around the core of eight large subunits.Abbreviations LS
large subunit
- Rubisco
ribulose 1,5-bisphosphate carboxylase/oxygenase
- SS
small subunit 相似文献
975.
Tryptophan decarboxylase (EC 4.2.1.27) is synthesized de-novo by Catharanthus roseus cells shortly after the cells have been transferred into culture medium in which monoterpenoid indole alkaloids are formed. The enzyme production, monitored by in-vivo labelling with [35S]methionine and immunoprecipitation, precedes the apparent maximal enzyme activity by 10–12 h. From the time course of the descending enzyme activity after induction, a half-life of 21 h for tryptophan decarboxylase in C. roseus cell suspensions is calculated. A comparison of the polyadenylated-RNA preparations from C. roseus cells indicates that mRNA activity for tryptophan decarboxylase is only detected in cells grown in the production medium. The importance of tryptophan decarboxylase induction with respect to the accumulation of th corresponding alkaloids is discussed.Abbreviation TDC
tryptophan decarboxylase 相似文献
976.
Photoacoustic and fluorescence measurements of the chilling response and their relationship to carbon dioxide uptake in tomato plants 总被引:5,自引:0,他引:5
The response of tomato plants to various chilling treatments was studied using two approaches for the measurement of photosynthetic activity. One involved the use of a portable fluorometer for the measurement of in-vivo chlorophyll fluorescence, while the other employed a newly introduced photoacoustic system which allowed changes in oxygen evolution to be followed in a leaf disc. A strong correlation was found between results obtained by each system and those obtained by a conventional open gas-exchange system for the determination of CO2 uptake. Both systems of measurements could readily distinguish between the effects of chilling in the dark (at 3° C for 18 h) and chilling at high photon flux density (2000 mol m-2 s-1 for 5h at 5° C). Chilling in the dark had practically no effect on the quantum yield of oxygen evolution, chlorophyll fluorescence or CO2 uptake, while chilling at excessively high photon flux density resulted in a sharp reduction (50–70%) in the quantum yields obtained. The results support the view that photosystem II cannot be the primary site of damage by chilling in the dark, although it is significantly affected by chilling at high light intensity.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- PA
photoacoustic
- PFD
photon flux density
- PSII
photosystem II 相似文献
977.
5-Enolpyruvylshikimate 3-phosphate (EPSP) synthase (3-phosphoshikimate 1-carboxyvinyltransferase; EC 2.5.1.19), 3-dehydroquinate dehydratase (EC 4.2.1.10) and shikimate: NADP+ oxidoreductase (EC 1.1.1.25) were present in intact chloroplasts and root plastids isolated from pea seedling extracts by sucrose and modified-silica density gradient centrifugation. In young (approx. 10-d-old) seedling shoots the enzymes were predominantly chloroplastic; high-performance anion-exchange chromatography resolved minor isoenzymic activities not observed in density-gradientpurified chloroplasts. The initial enzyme of the shikimate pathway, 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (EC 4.1.2.15) was also associated with intact density-gradient-purified chloroplasts. 3-Dehydroquinate synthase (EC 4.6.1.3) and shikimate kinase (EC 2.7.1.71) were detected together with the other pathway enzymes in stromal preparations from washed chloroplasts. Plastidic EPSP synthase was inhibited by micromolar concentrations of the herbicide glyphosate.Abbreviations DAHP
3-deoxy-d-arabino-heptulosonate 7-phosphate
- DEAE
diethylaminoethyl
- DHQase
3-dehydroquinate dehydratase
- DTT
dithiothreitol
- EPSP
5-enolpyruvylshikimate 3-phosphate
- SORase
shikimate:NADP+ oxidoreductase 相似文献
978.
The effects of light and several photosynthetic inhibitors on the rate of sulfite metabolism in cells obtained from Cucumis sativus L. cotyledons was studied. The cells were treated with 200 M Na2SO3 and the disappearance of sulfite was monitored using either dithiobisnitrobenzoic acid or fuchsin. The rate of sulfite disappearance in light was double the dark rate. Disalicylidene propanediamine at 1 mM increased this light-enhanced metabolism approx. 50%; neither 1 M 3,4-dichlorophenyl-N,N-dimethylurea nor 0.1 mM cyanazine, which completely inhibited CO2-dependent oxygen evolution, affected the rate of sulfite metabolism. Addition of 200 M Na2SO3 to the cells partially inhibited 14CO2 fixation. The rate of sulfite consumption by the cells did not affect this inhibition. We conclude that light-dependent sulfite metabolism is cucumber cells may utilize reduced ferredoxin generated as a result of photosynthetic electron transport. An injurious interaction between CO2 fixation and sulfite appears to occur independently of the sulfite-metabolism process.Abbreviations DCMU
3,4-dichlorophenyl-N,N-dimethylurea
- DSPD
disalicylidene propanediamine
- DTNB
5,5-dithiobis-(2-nitrobenzoic acid) 相似文献
979.
Methods were developed for the isolation of plastids from mature green and ripening tomatoes (Lycopersicon esculentum Mill.) and purification by sucrose or Percoll density-gradient centrifugation. Assessment of the purity of preparations involved phase-contrast and electron microscopy, assays for marker enzymes and RNA extraction and analysis. Proteins were extracted from isolated plastids at different ripening stages and separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The profiles obtained from chloroplasts and chromoplasts showed many qualitative and quantitative differences. Labelling of proteins with [35S]methionine in vivo showed that there was active protein synthesis throughout ripening, but there was a change in the plastid proteins made as ripening proceeded. The cellular location of synthesis of specific proteins has yet to be established.Abbreviations CS
citrate synthase
- EDTA
ethylenediaminetetraacetic acid,-acetate
- GAPDH
NADP+-glyceraldehyde-3-phosphate dehydrogenase
- rRNA
ribosomal RNA
- SDS
sodium dodecyl sulphate
- SDS-PAGE
SDS-polyacrylamide gel electrophoresis
- Tris
2-amino-2(hydroxymethyl)-1,3-propanediol 相似文献
980.
The effects of methyl jasmonate and jasmonic acid on uptake of abscisic acid (ABA) by suspension-cultured runner-bean cells and subapical runner-bean root segments have been investigated. Increasing concentrations of methyl jasmonate inhibit ABA uptake by the cultured cells with a K
i of 22±3 M. This is not due to cytoplasmic acidification or to effects on metabolism of ABA, and is not additive with inhibition of radioactive ABA uptake by nonradioactive ABA. Uptake of indol-3-yl acetic acid (IAA) is unaffected by methyl jasmonate. The maximum effect of nonradioactive ABA in inhibiting uptake of radioactive ABA, previously shown to reflect saturation of an ABA carrier, is generally greater than the effect of maximally inhibitory concentrations of methyl jasmonate. Similar results were obtained with root segments, but longer incubation times were necessary to observe inhibitory effects of methyl jasmonate. Demethylation of methyl jasmonate to jasmonic acid does not appear to be required since similar concentrations of jasmonic acid had no observable direct effect on ABA uptake other than that attributable to cytoplasmic acidification. Histidine reagents, a proton ionophore and acidic external pH all affect in parallel the inhibition by methyl jasmonate and nonradioactive ABA of uptake of radioactive ABA by the cultured cells. There is no effect of ABA or nonradioactive methyl jasmonate on uptake of radioactive methyl jasmonate by the cultured cells. It is proposed that methyl jasmonate interacts with the ABA carrier. Various models for this interaction are discussed.Abbreviations ABA
abscisic acid
- DMO
5,5-dimethyloxazolidine-2,4-dione
- IAA
indol-3-yl acetic acid 相似文献