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41.
Chloroplast ribosome-binding sites were identified on the plastidrbcL andpsbA mRNAs using toeprint analysis. TherbcL translation initiation domain is highly conserved and contains a prokaryotic Shine-Dalgarno (SD) sequence (GGAGG) located 4 to 12 nucleotides upstream of the initiator AUG. Toeprint analysis ofrbcL mRNA associated with plastid polysomes revealed strong toeprint signals 15 nucleotides downstream from the AUG indicating ribosome binding at the translation initiation site.Escherichia coli 30S ribosomes generated similar toeprint signals when mixed withrbcL mRNA in the presence of initiator tRNA. These results indicate that plastid SD sequences are functional in chloroplast translation initiation. ThepsbA initiator region lacks a SD sequence within 12 nucleotides of the initiator AUG. However, toeprint analysis of soluble and membrane polysome-associatedpsbA mRNA revealed ribosomes bound to the initiator region.E. coli 30S ribosomes did not associate with thepsbA translation initiation region.E. coli and chloroplast ribosomes bind to an upstream region which contains a conserved SD-like sequence. Therefore, translation initiation onpsbA mRNA may involve the transient binding of chloroplast ribosomes to this upstream SD-like sequence followed by scanning to localize the initiator AUG. Illumination 8-day-old dark-grown barley seedlings caused an increase in polysome-associatedpsbA mRNA and the abundance of initiation complexes bound topsbA mRNA. These results demonstrate that light modulates D1 translation initiation in plastids of older dark-grown barley seedlings. 相似文献
42.
Roots of ten-days-old seedlings obtained from a maize hybrid grown in complete or in sulphate-deprived medium were used to extract Poly(A)+RNA. The response to sulphate deprivation, which is known to increase the uptake capacity up to ten times, was manifested also by the expression of three mRNA species, as shown by the in vitro translation of the mRNA population. One hour after transfer to complete nutrient medium all three mRNAs were still present.Abbreviations BSA
Bovine Serum Albumine
- DTT
1,4-Dithio-DL-Threitol
- EDTA
Ethylenediaminetetraacetic-acid
- MES
2-(N-Morpholino) ethane sulfonic acid
- SDS
Sodium Dodecyl Sulfate
- TCA
Trichloracetic acid
- TRIS
Tris(hydroxy-methyl)-aminomethane 相似文献
43.
44.
Benzyladenine-induced changes in the translatable mRNA population in excised cucumber cotyledons 总被引:2,自引:0,他引:2
Benzyladenine-induced changes in the translatable mRNA population in excised cucumber cotyledons were studied. Poly (A)+ RNA was prepared from etiolated cotyledons incubated with or without benzyladenine (BA) for various periods in the dark. Using nonequilibrium pH gradient electrophoresis-SDS polyacrylamide gel electrophoresis and isoelectric focusing-SDS polyacrylamide gel electrophoresis, both basic and neutral proteins translated in vitro were separated. About 240 spots were detected and 16 of them changed within 6 h after BA application. Some spots changed quickly (within 1–2 h). Among them, three were repressed markedly 相似文献
45.
M. P. M. Derkx W. J. Smidt L. H. W. Van der Plas C. M. Karssen 《Physiologia plantarum》1993,89(4):707-718
Effects of dark incubation at different temperatures were studied on dormancy and respiratory activity of seeds of Sisymbrium officinale (L.) Scop. Because germination of this species absolutely depends on the simultaneous action of light and nitrate, changes in dormancy could be studied in darkness without the interference of early germination events. Upon the start of incubation rates of O2 uptake and CO2 release rose. This was followed by a gradual decrease until stable levels of O2 uptake and CO2 release were achieved. Seeds kept for prolonged periods at 24°C, showed neither a change in germination capacity nor in rates of O2 uptake and CO2 release. Respiratory quotients were 0.55–0.7. The initial rise in O2 uptake correlated with the rate of water uptake and with breaking of primary dormancy. However, the subsequent decline in O2 uptake was not generally linked to induction of secondary dormancy. An increased O2 uptake was not required during breaking of secondary dormancy. It is concluded that changes in dormancy are not generally related to changes in respiratory activity. However, germination strongly depends on respiration. The increase in O2 uptake started well before radicle protrusion. A far red irradiation only reversed this increase when it was given before germination escaped from its red light antagonising action. The contribution of different respiratory pathways was followed during prolonged incubation at 24°C in darkness. KCN at 1.5 mM was needed to inhibit the cytochrome pathway (CP) and benzohydroxamic acid (BHAM) at 30 mM to inhibit the alternative pathway (AP). These concentrations did not exert any side effects. Electron flow was predominantly via the CP, maximally 10% was via the AP. Flow through the CP declined during the first 6 days and residual respiration remained constant. Therefore, the contribution of residual respiration became relatively more important with prolonged incubation. KCN at concentrations that almost completely inhibited flow through the CP, did not dramatically reduce germination. BHAM already inhibited germination at concentrations that do not inhibit oxygen uptake. 相似文献
46.
47.
Genetics of lactobacilli: Plasmids and gene expression 总被引:20,自引:0,他引:20
48.
Oleosins of Brassica napus L. (oilseed rape) synthesized by in-vitro translation were found to be very efficiently targeted to microsomal membranes but only poorly translocated to oil bodies or emulsified oil. The use of other bilayer membranes as controls showed that this interaction was specific. The rate of oleosin synthesis in the presence of microsomes was enhanced about threefold, indicative of the involvement of the signal-recognition particle in the targeting process. There is no evidence for the cleavage of the protein during targeting and the protein sequence reveals no consensus cleavage site for the signal peptide. Protection experiments using Proteinase K revealed that about 6 kDa of the protein is exposed on the cytoplasmic side of the ER but the remainder is protected. Carbonate (pH 11) washing of microsomal membranes after in-vitro translation confirmed that oleosins have a domain which remains inserted in the ER rather than the protein being transported completely into the lumen of the ER. These results indicate that oleosins are transported via the ER prior to their accumulation on oil bodies. 相似文献
49.
Toshitsugu Nakamura Masao Hotchi 《Virchows Archiv. B, Cell pathology including molecular pathology》1993,63(1):11-16
DNA strand breaks (nicks) in non-parenchymal cells (NPCs) in CCl4-induced acute or chronic liver injury in rats were detected using an in situ nick translation method; their dynamic changes
were analysed in relation to the proliferation pattern of hepatocytes and NPCs, as revealed by bromodeoxyuridine (BrdU)-up-take.
In acute injury, hepatocyte proliferation started before centrilobular necrosis had occurred, whereas BrdU-labeled sinusoidal
NPCs markedly increased only after centrilobular necrosis was apparent. DNA breakages in NPCs paralleled the proliferation
pattern of these cells, suggesting that nicks are physiological, and reflect proliferation and activated gene expression.
In chronic injury, liver cirrhosis developed after 9 weeks, but BrdU-labeling of hepatocytes was almost the same level as
that in untreated liver. The number of BrdU-labeled NPCs showed only a slight increase, while those with DNA breakages were
much more frequent in the cirrhotic stage, suggesting a significant role for NPCs in the fibrotic process. These results indicate
that DNA strand breaks in NPCs act as a marker for activation states such as proliferation, differentiation and/or activated
gene expression. 相似文献
50.
E. V. Garmash 《Plant biology (Stuttgart, Germany)》2023,25(1):43-53
Mitochondrial alternative oxidase is an important protein involved in maintaining cellular metabolic and energy balance, especially under stress conditions. AOX genes knockout is aimed at revealing the functions of AOX genes. Under unfavourable conditions, AOX-suppressed plants (mainly based on Arabidopsis AOX1a-knockout lines) usually experience strong oxidative stress. However, a compensation effect, which consists of the absence of AOX1a leading to an increase in defence response mechanisms, concomitant with a decrease in ROS content, has also been demonstrated. This review briefly describes the possible mechanisms underlying the compensation effect upon the suppression of AOX1a. Information about mitochondrial retrograde regulation of AOX is given. The importance of ROS and mitochondrial membrane potential in triggering the signal transmission from mitochondria in the absence of AOX or disturbance of mitochondrial electron transport chain functions is indicated. The few available data on the response of the cell to the absence of AOX at the level of changes in the hormonal balance and the reactions of chloroplasts are presented. The decrease in the relative amount of reduced ascorbate at stable ROS levels as a result of compensation in AOX1a-suppressed plants is proposed as a sign of stress development. Obtaining direct evidence on the mechanisms and signalling pathways involved in AOX modulation in the genome should facilitate a deeper understanding of the role of AOX in the integration of cellular signalling pathways. 相似文献