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991.
Francis V. DeFeudis Lucienne Ossola Gaby Schmitt Paul Mandel 《Journal of neurochemistry》1980,34(4):845-849
Abstract: The effects of some GABA analogues and some drugs on the binding of [3H]muscimol (3.08 nM) to thoroughly washed subcellular particles prepared from a neuron-enriched culture of embryonic rat brain were examined using Na+-free Tris-citrate medium and a centrifugation method. Competition for [3H]muscimol binding sites by excess(10?5 M) unlabelled GABA provided estimates of “specific” binding. In accord with in vivo neuropharmacological studies on GABA receptors and with in vitro studies on cerebral membrane preparations, [3H]muscimol binding was potently inhibited by muscimol itself (IC50, 2.5 nM), GABA (1C50, 43 nM), isoguvacine (IC50, 61 nM), and 3-aminopropanesulphonic acid (IC50, 160 nM), and less potently inhibited by the GABA antagonist bicuculline methobromide (IC50, 800 nM). δ- Aminovaleric acid (IC50, 2.6 μM), the glycinelp-alanine antagonist strychnine (IC50, 6.6 μM), and the predominantly glial GABA uptake inhibitors β-alanine (IC50, 23 μM) and p-proline (IC50, 66 μM) also inhibited [3H]muscimol binding. Other inhibitors of Na+-dependent GABA uptake, (±)-nipecotic acid, L- 2,4-diaminobutyric acid, and guvacine, as well as picrotoxinin, were relatively inactive as inhibitors of [3H]muscimol binding (IC50≥ 1 mM). In addition to revealing that GABA receptors are present on neuronal membranes before the formation of most synapses, this binding of [3H]muscimol that occurs to neuronal, but not to glial, membranes might be useful as a “neuronal marker” and for the further characterization and isolation of GABA receptors. 相似文献
992.
Use of lambda pMu bacteriophages to isolate lambda specialized transducing bacteriophages carrying genes for bacterial chemotaxis. 总被引:3,自引:0,他引:3 下载免费PDF全文
A general method for constructing lambda specialized transducing phages is described. The method, which is potentially applicable to any gene of Escherichia coli, is based on using Mu DNA homology to direct the integration of a lambda pMu phage near the genes whose transduction is desired. With this method we isolated a lambda transducing phage carrying all 10 genes in the che gene cluster (map location, 41.5 to 42.5 min). The products of the cheA and tar genes were identified by using transducing phages with amber mutations in these genes. It was established that tar codes for methyl-accepting chemotaxis protein II (molecular weight, 62,000) and that cheA codes for two polypeptides (molecular weights, 76,000 and 66,000). Possible origins of the two cheA polypeptides are discussed. 相似文献
993.
Different methods for the preparation of active lipoxygenase (LOX) extracts from apples were compared. Highest activities were obtained using a 0.25 M phosphate buffer (pH 7) containing 1% Triton X-100 and 10?2 M metabisulphite as extraction solvent. LOX activity during storage was investigated in the core, flesh, and peel. Activity was always highest in the core and peel. On storage, activity was increased in each part of the fruit but especially in the core and peel. Increase in LOX preceded the browning of the core. LOX may be responsible for the browning and may be concerned in the induction of superficial scald. 相似文献
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998.
The amino acid sequence divergence of glutamine synthetase (GS) from species ofVibrio, Photobacterium, Aeromonas, Escherichia, Salmonella, Citrobacter, Enterobacter, Serratia, Proteus, Erwinia, Xenorhabdus, andPlesiomonas was determined by quantitative microcomplement fixation, using antisera to GS fromVibrio alginolyticus andEscherichia coli. A similar study was performed with superoxide dismutase (SOD), using antiserum to the enzyme fromV. alginolyticus. A comparison of the results for GS and SOD, relative to the enzymes fromV. alginolyticus, as well as a comparison of these data with the results of previous ribosomal RNA (rRNA)/DNA homology studies indicated a
high degree of congruence (correlation coefficients≥0.9). The results with both enzymes suggested four major groupings among
these genera: (i)Vibrio, (ii)Photobacterium, (iii)Aeromonas, (iv) a large and heterogeneous group which included the peritrichously flagellated terrestrial enterobacteria. 相似文献
999.
A review of some physiological and toxicological responses of freshwater fish to acid stress 总被引:2,自引:0,他引:2
Paul O. Fromm 《Environmental Biology of Fishes》1980,5(1):79-93
Synopsis Data relating to the specific effect of low pH on growth of freshwater fishes are ambiguous. Reproductive failure resulting
from acid stress appears to be related to an upset in calcium metabolism and to faulty deposition of protein in developing
oocytes. It appears that the ’no effect‘ level of pH depression for successful reproduction is around 6.5. Data on behaviorial
responses of freshwater fish to acid stress and CO2 are described. Most fish appear to be indifferent to pH within the range of approximately 10.5 to 5.5 and between 7.4 and
4.5 CO2 appears to be the main directive factor. In cases of severe acid stress alteration of gill membranes and/or coagulation of
gill mucus occurs and death due to hypoxia may result from a lengthening of the water-blood diffusion distance. Several reports
agree that acid stress causes an upset of electrolyte homeostasis in fish but effects of low pH on osmotic permeability are
largely lacking. Most hatcheryreared salmonids can tolerate pH 5.0 indefinitely but below this level the homeostatic electrolyte
and osmotic regulatory mechanisms become inadequate. When fish are subjected to debilitating acid stress blood pH decreases
possibly as the result of flux of H+ ions across gill membranes into the blood. This could change transepithelial potential and allow a blood, to-water diffusion
of Na+ ions down an electrochemical gradient. Lowered ambient pH may interfere with gill calcium levels increasing permeability
to both H+ and Na+ ions or an acidemia may occur as the result of a decrease in the excretion of metabolically produced H+ ions and CO2. When the capacity of the buffer mechanisms is exceeded the blood pH drops and the capacity of hemoglobin to transport oxygen
is decreased. 相似文献
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