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51.
Synaptic destabilization by neuronal Nogo-A 总被引:1,自引:0,他引:1
Aloy EM Weinmann O Pot C Kasper H Dodd DA Rülicke T Rossi F Schwab ME 《Brain Cell Biology》2006,35(2-3):137-157
Formation and maintenance of a neuronal network is based on a balance between plasticity and stability of synaptic connections.
Several molecules have been found to regulate the maintenance of excitatory synapses but nothing is known about the molecular
mechanisms involved in synaptic stabilization versus disassembly at inhibitory synapses. Here, we demonstrate that Nogo-A,
which is well known to be present in myelin and inhibit growth in the adult CNS, is present in inhibitory presynaptic terminals
in cerebellar Purkinje cells at the time of Purkinje cell-Deep Cerebellar Nuclei (DCN) inhibitory synapse formation and is
then downregulated during synapse maturation. We addressed the role of neuronal Nogo-A in synapse maturation by generating
several mouse lines overexpressing Nogo-A, starting at postnatal ages and throughout adult life, specifically in cerebellar
Purkinje cells and their terminals. The overexpression of Nogo-A induced a progressive disassembly, retraction and loss of
the inhibitory Purkinje cell terminals. This led to deficits in motor learning and coordination in the transgenic mice. Prior
to synapse disassembly, the overexpression of neuronal Nogo-A led to the downregulation of the synaptic scaffold proteins
spectrin, spectrin-E and β-catenin in the postsynaptic neurons. Our data suggest that neuronal Nogo-A might play a role in
the maintenance of inhibitory synapses by modulating the expression of synaptic anchoring molecules.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
52.
Petitdemange C Becquart P Wauquier N Béziat V Debré P Leroy EM Vieillard V 《PLoS pathogens》2011,7(9):e1002268
Chikungunya virus (CHIKV) is a worldwide emerging pathogen. In humans it causes a syndrome characterized by high fever, polyarthritis, and in some cases lethal encephalitis. Growing evidence indicates that the innate immune response plays a role in controlling CHIKV infection. We show here that CHIKV induces major but transient modifications in NK-cell phenotype and function soon after the onset of acute infection. We report a transient clonal expansion of NK cells that coexpress CD94/NKG2C and inhibitory receptors for HLA-C1 alleles and are correlated with the viral load. Functional tests reveal cytolytic capacity driven by NK cells in the absence of exogenous signals and severely impaired IFN-γ production. Collectively these data provide insight into the role of this unique subset of NK cells in controlling CHIKV infection by subset-specific expansion in response to acute infection, followed by a contraction phase after viral clearance. 相似文献
53.
Heroen Verbruggen † Lennert Tyberghein † Klaas Pauly † Caroline Vlaeminck Katrien Van Nieuwenhuyze Wiebe H.C.F. Kooistra Frederik Leliaert Olivier De Clerck 《Global Ecology and Biogeography》2009,18(4):393-405
Aim Because of their broad distribution in geographical and ecological dimensions, seaweeds (marine macroalgae) offer great potential as models for marine biogeographical inquiry and exploration of the interface between macroecology and macroevolution. This study aims to characterize evolutionary niche dynamics in the common green seaweed genus Halimeda, use the observed insights to gain understanding of the biogeographical history of the genus and predict habitats that can be targeted for the discovery of species of special biogeographical interest. Location Tropical and subtropical coastal waters. Methods The evolutionary history of the genus is characterized using molecular phylogenetics and relaxed molecular clock analysis. Niche modelling is carried out with maximum entropy techniques and uses macroecological data derived from global satellite imagery. Evolutionary niche dynamics are inferred through application of ancestral character state estimation. Results A nearly comprehensive molecular phylogeny of the genus was inferred from a six‐locus dataset. Macroecological niche models showed that species distribution ranges are considerably smaller than their potential ranges. We show strong phylogenetic signal in various macroecological niche features. Main conclusions The evolution of Halimeda is characterized by conservatism for tropical, nutrient‐depleted habitats, yet one section of the genus managed to invade colder habitats multiple times independently. Niche models indicate that the restricted geographical ranges of Halimeda species are not due to habitat unsuitability, strengthening the case for dispersal limitation. Niche models identified hotspots of habitat suitability of Caribbean species in the eastern Pacific Ocean. We propose that these hotspots be targeted for discovery of new species separated from their Caribbean siblings since the Pliocene rise of the Central American Isthmus. 相似文献
54.
55.
Caroline J. Rose Katrin Hammerschmidt Yuriy Pichugin Paul B. Rainey 《Ecology letters》2020,23(9):1380-1390
The evolutionary transition to multicellularity has occurred on numerous occasions, but transitions to complex life forms are rare. Here, using experimental bacterial populations as proxies for nascent multicellular organisms, we manipulate ecological factors shaping the evolution of groups. Groups were propagated under regimes requiring reproduction via a life cycle replete with developmental and dispersal (propagule) phases, but in one treatment lineages never mixed, whereas in a second treatment, cells from different lineages experienced intense competition during the dispersal phase. The latter treatment favoured traits promoting cell growth at the expense of traits underlying group fitness – a finding that is supported by results from a mathematical model. Our results show that the transition to multicellularity benefits from ecological conditions that maintain discreteness not just of the group (soma) phase, but also of the dispersal (germline) phase. 相似文献
56.
Nasi Mian Caroline E. Anderson Andrew J. Pope Anthony R. Smith Paul S. Richardson Kim Balfre Paul W. Kent 《The Biochemical journal》1982,208(2):425-433
Chicken tracheal mucosa in vitro transported and incorporated radioactive precursors into mucins, which were secreted at a steady rate into the tracheal lumen. Secretion of mucins labelled with 35S and 3H after pulse-labelling of the mucosal layer with Na235SO4 and d-[1-3H]glucosamine as precursors was an energy-dependent process, as it was strongly inhibited by the action of respiratory-chain inhibitors, an uncoupler of oxidative phosphorylation, a metabolic blocker and a temperature shift from 41°C to 5°C. On the other hand, both cholinergic and parasympathomimetic agents considerably increased the secretion of dual-radiolabelled mucins when applied on the submucosal side of the trachea. The effect of Ca2+ was directional, since only high submucosal (3.6 or 18mm) or low luminal (zero or 0.18mm) Ca2+ massively enhanced the secretion of radiolabelled mucin compared with the mucin output measured under physiological Ca2+ conditions (1.8mm). Whereas application of ionophore A23187 on either side of the trachea significantly increased mucin output, its presence in the appropriate tracheal compartment and under appropriate Ca2+ conditions further accentuated the output of radiolabelled mucins. Addition of acetylcholine under appropriate conditions also had an additive effect on the Ca2+-stimulated secretion of mucins. Ca2+ stimulation of mucin secretion appears to be dependent on the metabolic integrity of the mucosal cells. Mucins secreted in response to high submucosal and low luminal [Ca2+] appear to consist of a number of different types of glycoproteins, as judged from their ion-exchange-chromatographic behaviour. 相似文献
57.
Shannyn E. Wolfe Daniel E. Howard John A. Schetz Caroline J. Cheng Robert Webber Diane M. Beatty Bibie M. Chronwall & Stephen J. Morris 《Journal of neurochemistry》1999,72(2):479-490
Abstract : Dopamine D2 receptors both acutely and chronically inhibit high-voltage-activated Ca2+ channels (HVA-CCs). Two alternatively spliced isoforms, D2L (long) and D2S (short), are expressed at high levels in rat pituitary intermediate lobe melanotropes but are lacking in anterior lobe corticotropes. We stably transfected D2L and D2S into corticotrope-derived AtT20 cells. Both isoforms coupled to inhibition of Q-type calcium channels through pertussis toxin-sensitive G proteins. Thus, we have created a model system in which to study the kinetics of D2 -receptor regulation of Ca2+ channels. Rapid inhibition of HVA-CCs was characterized using a novel fluorescence video imaging technique for the measurement of millisecond kinetic events. We measured the time elapsed (lag time) between the arrival of depolarizing isotonic 66 m M K+ , sensed by fluorescence from included carboxy-X-rhodamine (CXR), and the beginning of increased intracellular Ca2+ levels (sensed by changes in indo 1 fluorescence ratio). The lag time averaged 350-550 ms, with no significant differences among cell types. Addition of the D2 -agonist quinpirole (250 μ M ) to the K+ /CXR solution significantly increased the lag times for D2 -expressing cells but did not alter the lag time for AtT20 controls. The increased lag times for D2L - and D2S -transfected cells suggest that at least a fraction of the Ca2+ channels was inhibited within the initial 350-550 ms. As this inhibition time is too fast for a multistep second messenger pathway, we conclude that inhibition occurs via a membrane-delimited diffusion mechanism. 相似文献
58.
Rob C. van Lummel Stefan Walgaard Markus A. Hobert Walter Maetzler Jaap H. van Die?n Francisca Galindo-Garre Caroline B. Terwee 《PloS one》2016,11(3)
Background
The “Timed Up and Go” (TUG) is a widely used measure of physical functioning in older people and in neurological populations, including Parkinson’s Disease. When using an inertial sensor measurement system (instrumented TUG [iTUG]), the individual components of the iTUG and the trunk kinematics can be measured separately, which may provide relevant additional information.Objective
The aim of this study was to determine intra-rater, inter-rater and test-retest reliability of the iTUG in patients with Parkinson’s Disease.Methods
Twenty eight PD patients, aged 50 years or older, were included. For the iTUG the DynaPort Hybrid (McRoberts, The Hague, The Netherlands) was worn at the lower back. The device measured acceleration and angular velocity in three directions at a rate of 100 samples/s. Patients performed the iTUG five times on two consecutive days. Repeated measurements by the same rater on the same day were used to calculate intra-rater reliability. Repeated measurements by different raters on the same day were used to calculate intra-rater and inter-rater reliability. Repeated measurements by the same rater on different days were used to calculate test-retest reliability.Results
Nineteen ICC values (15%) were ≥ 0.9 which is considered as excellent reliability. Sixty four ICC values (49%) were ≥ 0.70 and < 0.90 which is considered as good reliability. Thirty one ICC values (24%) were ≥ 0.50 and < 0.70, indicating moderate reliability. Sixteen ICC values (12%) were ≥ 0.30 and < 0.50 indicating poor reliability. Two ICT values (2%) were < 0.30 indicating very poor reliability.Conclusions
In conclusion, in patients with Parkinson’s disease the intra-rater, inter-rater, and test-retest reliability of the individual components of the instrumented TUG (iTUG) was excellent to good for total duration and for turning durations, and good to low for the sub durations and for the kinematics of the SiSt and StSi. The results of this fully automated analysis of instrumented TUG movements demonstrate that several reliable TUG parameters can be identified that provide a basis for a more precise, quantitative use of the TUG test, in clinical practice. 相似文献59.
Genetic and environmental influences on migraine: a twin study across six countries. 总被引:7,自引:0,他引:7
Elles J Mulder Caroline Van Baal David Gaist Mikko Kallela Jaakko Kaprio Dan A Svensson Dale R Nyholt Nicholas G Martin Alex J MacGregor Lynn F Cherkas Dorret I Boomsma Aarno Palotie 《Twin research》2003,6(5):422-431
Migraine is a common neurovascular brain disorder that is manifested in recurrent episodes of disabling headache. The aim of the present study was to compare the prevalence and heritability of migraine across six of the countries that participate in GenomEUtwin project including a total number of 29,717 twin pairs. Migraine was assessed by questionnaires that differed between most countries. It was most prevalent in Danish and Dutch females (32% and 34%, respectively), whereas the lowest prevalence was found in the younger and older Finnish cohorts (13% and 10%, respectively). The estimated genetic variance (heritability) was significant and the same between sexes in all countries. Heritability ranged from 34% to 57%, with lowest estimates in Australia, and highest estimates in the older cohort of Finland, the Netherlands, and Denmark. There was some indication that part of the genetic variance was non-additive, but this was significant in Sweden only. In addition to genetic factors, environmental effects that are non-shared between members of a twin pair contributed to the liability of migraine. After migraine definitions are homogenized among the participating countries, the GenomEUtwin project will provide a powerful resource to identify the genes involved in migraine. 相似文献
60.
Maunoury F Berveiller D Lelarge C Pontailler JY Vanbostal L Damesin C 《Oecologia》2007,151(2):268-279
The stable C isotope composition (δ13C) of CO2 respired by trunks was examined in a mature temperate deciduous oak forest (Quercus petraea). Month-to-month, day-to-day and diurnal, measurements were made to determine the range of variations at different temporal
scales. Trunk growth and respiration rates were assessed. Phloem tissue was sampled and was analysed for total organic matter
and soluble sugar 13C composition. The CO2 respired by trunk was always enriched in 13C relative to the total organic matter, sometimes by as much as 5‰. The δ13C of respired CO2 exhibited a large seasonal variation (3.3‰), with a relative maximum at the beginning of the growth period. The lowest values
occurred in summer when the respiration rates were maximal. After the cessation of radial trunk growth, the respired CO2 δ13C values showed a progressive increase, which was linked to a parallel increase in soluble sugar content in the phloem tissue
(R = 0.95; P < 0.01). At the same time, the respiration rates declined. This limited use of the substrate pool might allow the discrimination
during respiration to be more strongly expressed. The late-season increase in CO2 δ13C might also be linked to a shift from recently assimilated C to reserves. At the seasonal scale, CO2 δ13C was negatively correlated with air temperature (R = −0.80; P < 0.01). The diurnal variation sometimes reached 3‰, but the range and the pattern depended on the period within the growing
season. Contrary to expectations, diurnal variations were maximal in winter and spring when the leaves were missing or not
totally functional. By contrast to the seasonal scale, these diurnal variations were not related to air temperature or sugar
content. Our study shows that seasonal and diurnal variations of respired 13C exhibited a similar large range but were probably explained by different mechanisms. 相似文献