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71.
72.
In vitro and in vivo action of antisense RNA 总被引:3,自引:0,他引:3
The transient or permanent expression of antisense RNA represents one option to apply antisense techniques in biotechnology
and medical research. Despite the increasing importance and use of antisense nucleic acids as well as their significant antisense-specific
phenotypic effects in vivo, there is an obvious lack of explanation for the mechanism of their action. By studying naturally
occurring antisense RNA and analyzing their mechanism of action we attempt to learn more about the design, the use, and the
critical parameters of artificial antisense RNA. Attempts to derive models from biochemical and structural studies for the
interactions between antisense RNAs and their targets will be discussed. 相似文献
73.
Abstract: Stimulation of chick sympathetic neurons in culture by the cholinergic agonists acetylcholine, nicotine, and 1,1-dimethyl-4-phenylpiperazinium (all at 10–1,000 µmol/L) induced concentration-dependent increases of free calcium levels measured by fura 2 fluorescence in neuronal processes. The response evoked by acetylcholine had both nicotinic and muscarinic components, whereas that induced by 1,1-dimethyl-4-phenylpiperazinium was purely nicotinic. Tetrodotoxin (0.3 µmol/L) blocked completely the increase of intraterminal free calcium level evoked by electrical stimulation. On the other hand, stimulation with 1,1-dimethyl-4-phenylpiperazinium still evoked 20–25% of the control response in the presence of tetrodotoxin. The concentration-response relationship of 1,1-dimethyl-4-phenylpiperazinium stimulation did not differ in the absence and in the presence of tetrodotoxin. The nicotinic antagonists d -tubocurarine (10 µmol/L) and mecamylamine (10 µmol/L), but not α-bungarotoxin (125 nmol/L), prevented the increase of intraterminal free calcium level evoked by 1,1-dimethyl-4-phenylpiperazinium (100 µmol/L) in the presence of tetrodotoxin. These observations indicate the presence of nicotinic receptors on neuronal processes that increase the intraterminal concentration of free calcium and probably modulate transmitter release. Their pharmacological properties are similar to those of nicotinic receptors located on neuronal cell bodies. 相似文献
74.
Prof. Dr. Wolf-Christian Dullo Dr. Marcos Gektidis Prof. Dr. Stjepko Golubic Dr. Georg A. Heiss Dipl. Biol. Heike Kampmann Dr. William Kiene Dipl. Ökol. Dieter K. Kroll Dipl. Biol. Martin L. Kuhrau Dr. Gudrun Radtke Dr. John G. Reijmer Dr. Götz B. Reinicke Prof. Dr. Dietrich Schlichter Prof. Dr. Helmut Schuhmacher Klaus Vogel 《Facies》1995,32(1):145-188
75.
Androgen Ablation Leads to an Upregulation and Intranuclear Accumulation of Deoxyribonuclease I in Rat Prostate Epithelial Cells Paralleling Their Apoptotic Elimination 总被引:1,自引:0,他引:1 下载免费PDF全文
76.
The Lipid Peroxidation Product, 4-Hydroxy-2-trans-Nonenal, Alters the Conformation of Cortical Synaptosomal Membrane Proteins 总被引:6,自引:1,他引:5
‡Ram Subramaniam ‡Fred Roediger Brad Jordan †‡§Mark P. Mattson §Jeffrey N. Keller Georg Waeg ‡§ D. Allan Butterfield 《Journal of neurochemistry》1997,69(3):1161-1169
Abstract: Alzheimer's disease (AD) is widely held to be a disorder associated with oxidative stress due, in part, to the membrane action of amyloid β-peptide (Aβ). Aβ-associated free radicals cause lipid peroxidation, a major product of which is 4-hydroxy-2- trans -nonenal (HNE). We determined whether HNE would alter the conformation of synaptosomal membrane proteins, which might be related to the known neurotoxicity of Aβ and HNE. Electron paramagnetic resonance spectroscopy, using a protein-specific spin label, MAL-6(2,2,6,6-tetramethyl-4-maleimidopiperidin-1-oxyl), was used to probe conformational changes in gerbil cortical synaptosomal membrane proteins, and a lipid-specific stearic acid label, 5-nitroxide stearate, was used to probe for HNE-induced alterations in the fluidity of the bilayer domain of these membranes. Synaptosomal membranes, incubated with low concentrations of HNE, exhibited changes in protein conformation and bilayer order and motion (fluidity). The changes in protein conformation were found to be concentration- and time-dependent. Significant protein conformational changes were observed at physiologically relevant concentrations of 1–10 µ M HNE, reminiscent of similar changes in synaptosomal membrane proteins from senile plaque- and Aβ-rich AD hippocampal and inferior parietal brain regions. HNE-induced modifications in the physical state of gerbil synaptosomal membrane proteins were prevented completely by using excess glutathione ethyl ester, known to protect neurons from HNE-caused neurotoxicity. Membrane fluidity was found to increase at higher concentrations of HNE (50 µ M ). The results obtained are discussed with relevance to the hypothesis of Aβ-induced free radical-mediated lipid peroxidation, leading to subsequent HNE-induced alterations in the structure and function of key membrane proteins with consequent neurotoxicity in AD brain. 相似文献
77.
The ant’s path integration system: a neural architecture 总被引:3,自引:0,他引:3
A model is developed by which path integration as observed in many animal species could be implemented neurobiologically.
The proposed architecture is able to describe the navigation behaviour of Cataglyphis ants, and that of other social insects, at the level of interacting neurons. The basic idea of this architecture is the concept
of activity patterns travelling along neural chains. Although experimental evidence has yet to be provided, this concept seems
biologically plausible and not limited to the navigation problem. Neural chains are able to represent variables by activity
patterns with high accuracy and temporal stability. Moreover, they are able to integrate incremental signals with high precision.
Cyclical chains of neurons show superior performance as soon as cyclical variables are to be represented and integrated. Finally,
representation of cyclical variables by travelling activity peaks allows simple approximations of goniometric functions as
they are used in path integration systems.
Received: 15 November 1994/Accepted in revised form: 30 May 1995 相似文献
78.
In nerve tissue the histochemical nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reaction is considered a suitable marker for nitric oxide synthase (NOS) activity. We have previously shown that the NOS-specific inhibitorl-nitroarginine (l-NNA) can block NADPH-d staining in intermediolateral (IML) neurons of the rat spinal cord; such a reaction might serve as a control for the presence of a NOS-related catalytic activity, i.e.,l-NNA-dependent NO synthesis in these neurons. However,l-NNA inhibition of neuronal NADPH-d is inconsistent and is therefore disputed by others. This prompted us to reinvestigate the reaction conditions to provide a standardized protocol for inhibition experiments. In IML neurons of formaldehyde-fixed spinal cord tissue, inhibition of NADPH-d reaction was tested by preincubation of frozen sections with the flavin-binder diphenylene iodonium chloride (DPI, 10 M-1 mM) which blocked the NADPH-d reaction in a concentration-dependent way, suggesting an inverse relationship of inhibitor concentration and final reaction product generated. Preincubation with the NOS-specific inhibitorl-NNA in glycine-NaOH buffer (pH 8.5–9.5) but notl-nitroarginine methyl ester (l-NAME) revealed a concentration-dependent blocking effect on neuronal NADPH-d comparable to the effects seen with DPI, suggesting the existence of al-NNA sensitive NADPH-d activity. Blocking withl-NNA (100 M-10 mM) was prevented by excessl-arginine (10–100 mM), suggesting competitive binding sites. NADPH-d staining was not inhibited by 7-nitro indazole, another NOS inhibitor. Thus, in formaldehyde-fixed nervous tissue both DPI andl-NNA inhibit the NOS-associated catalytic NADPH-d activity, thereby preventing NADPH-dependent conversion of nitroblue tetrazolium to formazan.Presented in the Workshop Detection of NO-synthases at the XXXVI Symposium of the Society for Histochemistry on Oxy Radicals, 20–23 September 1994, Heidelberg, Germany 相似文献
79.
Georg R. Beilharz Carl R. Middlehurst Philip W. Kuchel Glenn E. Hunt Gordon F.S. Johnson 《Analytical biochemistry》1984,137(2):324-329
Detailed operating conditions are reported for the determination of choline in human erythrocytes using proton nuclear magnetic resonance spectroscopy in conjunction with the inversion-recovery spin-echo pulse sequence. The results of the NMR method were in excellent agreement with those obtained using an enzymatic (choline oxidase) assay; however, they were approximately three times higher than those reported using gas chromatography/mass spectrometry techniques. The differences may be partly due to the method of preparing or sampling cells since there is a distribution of choline in cells of different ages. However, choline levels were not affected by the methods used in the present study for storing or preparing cells. 相似文献
80.
Sucrose transport has been investigated in vacuoles isolated from barley mesophyll protoplasts. Rates of sucrose transfer across the tonoplast were even higher in vitro than in vivo indicating that the sucrose transport system had not suffered damage during isolation of the vacuoles. Sucrose transport is carrier-mediated as shown by substrate saturation of transport and sensitivity to a metabolic inhibitor and to competitive substrates. A number of sugars, in particular maltose and raffinose, decreased uptake of sucrose. Sorbitol was slowly taken up but had no effect on sucrose transport. The SH-reagent p-chloromercuribenzene sulfonate inhibited sucrose uptake completely. The apparent Km of the carrier for sucrose uptake was 21 mM. Transport was neither influenced by ATP and pyrophosphate, with or without Mg2+ present, nor by protonophores and valinomycin (with K+ present). Apparently uptake was not energy dependent. Efflux experiments with preloaded vacuoles indicated that sucrose unloading from the isolated vavuoles is mediated by the same carrier which catalyses uptake. The vacuole of mesophyll cells appears to represent an intermediary storage compartment. Uptake of photosynthetic products into the vacuole during the light apparently minimizes osmotic swelling of the small cytosolic compartment of vacuolated leaf cells when photosynthetic productivity exceeds the capacity of the phloem for translocation of sugars.Abbreviations Hepes
4-(2-hydroxyethyl)-1-piperazincethane-sulfonic acid
- pCMBS
p-chloromercuribenzene sulfonate
Dedicated to Professor Dr. W. Simonis on the occasion of his 75th birthday 相似文献