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91.
The role of polyamines (PA) synthesis in NMDA receptor-mediated45Ca2+ fluxes and norepinephrine release was studied in rat hippocampal synaptosomes. NMDA (50M) caused a sharp (>2-fold) transient increase in PA synthesis regulating enzyme, ornithine decarboxylase (ODC) activity with concomitant elevation in PA levels in the order putrescine>spermidine>spermine. ODC inhibitor, -difluoromethylornithine (DFMO), and NMDA antagonist, 2-amino-5-phosphonovaleric acid (D-AP5), both blocked increases in ODC activity and PA levels. Activation of NMDA receptors induced a sharp (3 to 4-fold) and quick (15 seconds) increase in45Ca2+ uptake by synaptosomes within 15 seconds of exposure at 37°C. The efflux of45Ca2+ and3H-norepinephrine (NE) release at 22°C from pre-loaded synaptosomes was also significantly (2 to 4-fold) enhanced by NMDA within 15 seconds. These NMDA receptor-mediated effects on calcium fluxes and NE release were blocked by NMDA receptor-antagonists (DAP-5 and MK-801) and PA synthesis inhibitor, DFMO and the DFMO inhibition nullified by exogenous putrescine. These observations establish that ODC/PA cascade play an important role in transduction of excitatory amino acid mediated signals at NMDA receptors.Special issue dedicated to Dr. Sidney Ochs. 相似文献
92.
Daniel Keppler Patrice Waridel Magnus Abrahamson Daniel Bachmann José Berdoz Bernard Sordat 《生物化学与生物物理学报:疾病的分子基础》1994,1226(2):117-125
The lysosomal cystein proteinase cathepsin B is shown to be secreted by ten human colon carcinoma cell lines and to accumulate in culture media as a latent enzyme. The cell lines also secrete a physiological inhibitor of cathepsin B, cystatin C. A significant correlation was found between secretion of the latent enzyme and the inhibitor (r = 0.755, P < 0.01). The aim of the present study was to modulate the respective secretion of the two antagonists to test whether or not latency of cathepsin B was due to the concomitant secretion of the inhibitor. SW480 colon carcinoma cells were treated with the acidotropic agent ammonium chloride, phorbol 12-myristate 13-acetate, and the inflammatory cytokines TGF-β, TNF-α, and IL-1β. Ammonium chloride significantly increased latent cathepsin B levels without affecting the constitutive secretion of cystatin C. Phorbol 12-myristate 13-acetate induced a 4- to 5-fold increase in secreted latent cathepsin B, but did not alter significantly the accumulation of cystatin C in media. The cytokines, TGF-β, TNF-α, and IL-1β, had no major effect on the expression of these two antagonists. Latent cathepsin B released from human carcinoma cells could be efficiently activated by neutrophil elastate at neutral pH. It is concluded that latent cathepsin B is a true proenzyme rather than an enzyme-inhibitor comples. In addition, our data from neutrophil elastate activation experiments indicate that a proteolytic system for activation of the tumor cell-secreted latent enzyme may exist in vivo. 相似文献
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95.
R. J. Leer H. Christiaens W. Verstraete L. Peters M. Posno P. H. Pouwels 《Molecular & general genetics : MGG》1993,239(1-2):269-272
A chloramphenicol-resistance gene (cml) was introduced into the Lactobacillus plantarum gene encoding conjugated bile acid hydrolasc (cbh) on a ColEl replicon. This plasmid which is nonreplicative in Lactobacillus was used to transform L. plantarum strain 80. A homologous double cross-over recombination event resulted in replacement of the chromosomal cbh gene by the cml-containing cbh gene. The transformants obtained were unable to synthesize active conjugated bile acid hydrolase (Cbh). The Cbh-CmlR phenotype was stably maintained for more than 100 generations under nonselective conditions.This paper is dedicated with great appreciation to Dr. Frits Berends on the occasion of his retirement as Head of the Biochemistry Department of the TNO Medical Biological Laboratory 相似文献
96.
Normal pods (containing seed) of groundnut (Arachis hypogaea L.) (cv. TMV-2) were successfully raised in darkened, aerated, nutrient solution, but not in the light. The onset of podding was evident 7 to 8 d after gynophores were submerged in the darkened nutrient solution. An examination of pods and submerged portions of gynophore surfaces by scanning electron microscopy showed the presence of two distinctly different protuberances: unicellular root-hair-like structures that first developed from epidermal cells of the gynophores and developing pods; and branched septate hairs that developed later from cells below the epidermal layer. The septate hairs became visible only after the epidermal and associated unicellular structures had been shed by the expanding gynophore and pods. Omission of Mn and Mg from the podding environment increased pod and seed weight, whilst omission of Zn reduced pod and seed weight. 相似文献
97.
A relatively drought tolerant cultivar of maize ( Zea mays L. cv. Pioneer 3950) and a drought tolerant line of sorghum ( Sorghum bicolor [L.] Moench cv. ICSV 112) were grown hydroponically for 11 days. Treatments for non-ionic osmotic and salt stresses were started at the 8th day by addition of polyethylene glycol 6000 and NaCl, respectively, at 200 mOsm equivalent concentrations in the presence or absence of 0. 1 μ M abscisic acid. Relative growth rate was depressed by both stress factors, more severely for maize than sorghum. Abscisic acid increased the growth rate and reverted the negative effect of NaCl in maize, while sorghum was only slightly affected. In general, sorghum had higher levels of K+ and lower levels of Na+ and the K+ /Na+ ratio was further increased by abscisic acid treatment. From the pressure-volume curves, osmotic potential, the water potential at turgor loss point, bulk elastic modulus and the water saturation deficit at initial turgor loss were estimated. Most significantly, sorghum had a higher elastic modulus than maize and it decreased under osmotic treatment, while in maize it increased under NaCl stress. The results suggest that bulk tissue turgor was not limiting growth under these conditions and underscores the possible implications of changes in the elastic condition of the cell walls in stress responses. 相似文献
98.
The uptake of lead by two contrasting plant species, radish and red fescue, grown in soils contaminated by mine spoil was investigated. Uptake was found to be poorly correlated either with pH or total Pb concentration in the soils. By contrast, a good correlation was obtained, particularly for red fescue, between Pb uptake and Pb concentration in the solution of equilibrated soil suspensions over a wide range of soil pH, total soil Pb and soil solution Pb concentration.Calculations suggested a similar order of magnitude in the total amounts of Pb taken up by the plants and Pb in the soil solution of the root zone, justifying the latter as a good index of Pb-availability. ei]Section editor: A C Borstlap 相似文献
99.
Evaluation of polysulfone hollow fibres and ceramic suction samplers as devices for the in situ extraction of soil solution 总被引:1,自引:0,他引:1
An investigation was carried out to assess the potential of using polysulfone hollow fibres for the extraction of soil solution. In comparison to ceramic suction samplers the fibres were shown to contain very low levels of potential contaminants and a low exchange capacity. Carry over between individual samples was negligible permitting the accurate monitoring of temporal changes in solution chemistry. Their flexible and root sized nature makes them ideal for sampling small soil volumes. Some concern however remains about retention of colloidal Fe at the fibre interface. When comparing the soil solution of samples extracted with polysulfone fibres with those extracted by ceramic suction samplers, no significant differences in solute concentrations were observed. No sample contamination resulting from dissolution of Al or Si from the ceramic cup was detected. Analysis of soil solutions collected over a number of extractions, and during and after a rainfall event showed concentrations of elements in solution to remain relatively constant with time. 相似文献
100.
Explants from new growth of forced dormant stems and secondary cultures of Vanhoutte's spirea were cultured on Linsmaier and Skoog (L.S.) medium containing benzyladenine (BA), indoleacetic acid (IAA), thidiazuron (TDZ), and zeatin. The dormant stems were forced by immersing their basal portions in forcing solutions containing 626 µM 8-hydroxyquinoline citrate (8-HQC) and 2% sucrose. BA and gibberellic acid (GA3) were also added into the forcing solutions to determine if explants obtained from the new growth will benefit from this treatment when culturedin vitro.L.S. medium supplemented with 5 µM BA alone, 5 µM BA plus 1 or 5 µM IAA, and 0.5 or 0.75 µM TDZ alone produced the best shoot proliferation for both sources of explants. BA and GA3 appeared to be taken up from the forcing solution by the new softwood growth. BA in the forcing solution stimulatedin vitro shoot proliferation in different degrees depending on the period of treatment, while GA3 caused lessin vitro shoot proliferation. It is proposed that forcing solutions containing plant growth regulators (P.G.R.) are a useful approach for manipulating responses of plant tissues culturedin vitro. 相似文献