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951.
Rita Pfister-Wilhelm 《Journal of insect physiology》2009,55(8):707-715
In the solitary egg-larval parasitoid Chelonus inanitus (Braconidae) both polydnavirus and the parasitoid larva manipulate host development. Parasitization leads to a premature drop in juvenile hormone titre and a precocious onset of metamorphosis in the 5th larval instar. The C. inanitus bracovirus (CiBV) alone causes a reduction in host ecdysteroid titres at the pupal cell formation stage and prevents pupation. Here we report three new findings. (1) We show that parasitization causes a reduction in haemolymph ecdysteroid titre immediately after the moult to the 5th instar; similarly low values were seen in nonparasitized larvae after the moult to the 6th instar. These data along with parasitoid removal experiments indicate that the low ecdysteroid titre after the moult is a very early sign of the upcoming metamorphosis. (2) In vitro experiments with prothoracic glands and brain extracts showed that CiBV affects both prothoracic glands and prothoracicotropic hormone after the stage of pupal cell formation. (3) In the haemolymph of parasitized larvae the ecdysteroid titre increased in the late cell formation stage, i.e. immediately before egression of the parasitoid. In vitro experiments showed that late 2nd instar parasitoids release ecdysteroids and are thus very likely responsible for the rise in host ecdysteroids. 相似文献
952.
Ruggiero A Tizzano B Pedone E Pedone C Wilmanns M Berisio R 《Journal of molecular biology》2009,385(1):153-162
Mycobacterium tuberculosis is able to establish a non-replicating state and survive in an intracellular habitat for years. Resuscitation of dormant M. tuberculosis bacteria is promoted by resuscitation-promoting factors (Rpfs), which are secreted from slowly replicating bacteria close to dormant bacteria. Here we report the crystal structure of a truncated form of RpfB (residues 194-362), the sole indispensable Rpf of the five Rpfs encoded in this bacterium genome. The structure, denoted as (DeltaDUF)RpfB, exhibits a comma-like shape formed by a lysozyme-like globular catalytic domain and an elongated G5 domain, which is widespread among cell surface binding proteins. The G5 domain, whose structure was previously uncharacterised, presents some peculiar features. The basic structural motif of this domain, which represents the tail of the comma-like structure, is a novel super-secondary-structure element, made of two beta-sheets interconnected by a pseudo-triple helix. This intricate organisation leads to the exposure of several backbone hydrogen-bond donors/acceptors. Mutagenesis analyses and solution studies indicate that this protein construct as well as the full-length form are elongated monomeric proteins. Although (DeltaDUF)RpfB does not self-associate, the exposure of structural elements (backbone H-bond donors/acceptors and hydrophobic side chains) that are usually buried in globular proteins is typically associated with adhesive properties. This suggests that the RpfB G5 domain has a cell-wall adhesive function, which allows the catalytic domain to be properly oriented for the cleavage reaction. Interestingly, sequence comparisons indicate that these structural features are also shared by G5 domains involved in biofilm formation. 相似文献
953.
Gaëtan Bellot Sébastien Granier William Bourguet René Seyer Rita Rahmeh Bernard Mouillac Robert Pascal Hélène Déméné 《Journal of molecular biology》2009,388(3):491-507
The V2 vasopressin receptor is a G-protein-coupled receptor that regulates the renal antidiuretic response. Its third intracellular loop is involved in the coupling not only with the GαS protein but also with gC1qR, a potential chaperone of G-protein-coupled receptors. In this report, we describe the NMR solution structure of the V2 i3 loop under a cyclized form (i3_cyc) and characterize its interaction with gC1qR. i3_cyc formed a left-twisted α-helical hairpin structure. The building of a model of the entire V2 receptor including the i3_cyc NMR structure clarified the side-chain orientation of charged residues, in agreement with literature mutagenesis reports. In the model, the i3 loop formed a rigid helical column, protruding deep inside the cytoplasm, as does the i3 loop in the recently elucidated structure of squid rhodopsin. However, its higher packing angle resulted in a different structural motif at the intracellular interface, which may be important for the specific recognition of GαS. Moreover, we could estimate the apparent Kd of the i3_cyc/gC1qR complex by anisotropy fluorescence. Using a shorter and more soluble version of i3_cyc, which encompassed the putative site of gC1qR binding, we showed by NMR saturation transfer difference spectroscopy that the binding surface corresponded to the central arginine cluster. Binding to gC1qR induced the folding of the otherwise disordered short peptide into a spiral-like path formed by a succession of I and IV turns. Our simulations suggested that this folding would rigidify the arginine cluster in the entire i3 loop and would alter the conformation of the cytosolic extensions of TM V and TM VI helices. In agreement with this conformational rearrangement, we observed that binding of gC1qR to the full-length receptor modifies the intrinsic tryptophan fluorescence binding curves of V2 to an antagonist. 相似文献
954.
Bess Frost Rachel L. Jacks Marc I. Diamond 《The Journal of biological chemistry》2009,284(19):12845-12852
Tauopathies are neurodegenerative diseases characterized by aggregation of
the microtubule-associated protein Tau in neurons and glia. Although Tau is
normally considered an intracellular protein, Tau aggregates are observed in
the extracellular space, and Tau peptide is readily detected in the
cerebrospinal fluid of patients. Tau aggregation occurs in many diseases,
including Alzheimer disease and frontotemporal dementia. Tau pathology begins
in discrete, disease-specific regions but eventually involves much larger
areas of the brain. It is unknown how this propagation of Tau misfolding
occurs. We hypothesize that extracellular Tau aggregates can transmit a
misfolded state from the outside to the inside of a cell, similar to prions.
Here we show that extracellular Tau aggregates, but not monomer, are taken up
by cultured cells. Internalized Tau aggregates displace tubulin, co-localize
with dextran, a marker of fluid-phase endocytosis, and induce fibrillization
of intracellular full-length Tau. These intracellular fibrils are competent to
seed fibril formation of recombinant Tau monomer in vitro. Finally,
we observed that newly aggregated intracellular Tau transfers between
co-cultured cells. Our data indicate that Tau aggregates can propagate a
fibrillar, misfolded state from the outside to the inside of a cell. This may
have important implications for understanding how protein misfolding spreads
through the brains of tauopathy patients, and it is potentially relevant to
myriad neurodegenerative diseases associated with protein misfolding.Tau filament deposition in Alzheimer disease
(AD),2 frontotemporal
dementia (FTD), and other tauopathies correlates closely with cognitive
dysfunction and cell death (1).
Mutations in the tau gene cause autosomal dominant tauopathy,
implicating Tau as the proximal cause
(2–4).
Specific disease phenotypes are defined by the early sites of pathology. For
example, AD is characterized by memory loss that derives from involvement of
hippocampal neurons, whereas FTD is characterized by personality changes that
result from frontal lobe involvement
(5). Pathology ultimately
spreads to involve much larger regions of brain. Studies on patients with AD
show a progressive, stereotyped spread of Tau deposits from the
transentorhinal cortex to the hippocampus, and eventually to most cortical
areas
(6–8).
Others have correlated the distribution of neurofibrillary tangles of Tau in
AD brains with trans-synaptic distance from the affected areas
(9). A similar spread affecting
different subsets of neurons has been observed in other sporadic tauopathies,
such as progressive supranuclear palsy
(10). It is unknown why Tau
misfolding progresses through the brain, whether it is a sequence of cell
autonomous processes or whether a toxic factor is involved. Loss of synaptic
connections and cell death may expose healthy cells to toxic factors and
decrease available neurotrophins
(11,
12). Another possibility is
that the Tau protein itself serves as the agent of trans-cellular propagation.
For example, it has been shown that extracellular Tau is toxic to cultured
neuronal cells (13,
14). This is consistent with
the observation that immunotherapy against Tau reduces pathology in a mouse
model (15).Tau is well known as an intracellular protein that stabilizes microtubule
filaments (16); however, it is
readily detected in cerebrospinal fluid
(17) and as extracellular
aggregates, termed “ghost tangles,” in diseased brain. These are
comprised predominantly of the microtubule-binding region (MTBR), the
functional and pathogenic core of the Tau protein
(18). We hypothesize that Tau
aggregates present in the extracellular space enter naive cells and induce
misfolding of intracellular Tau. We have tested this idea using cellular
studies, biochemistry, and atomic force microscopy (AFM). 相似文献
955.
Gianna Moscato Olivier Vandenplas Roy Gerth Van Wijk Jean-Luc Malo Luca Perfetti Santiago Quirce Jolanta Walusiak Roberto Castano Gianni Pala Denyse Gautrin Hans De Groot Ilenia Folletti Mona Rita Yacoub Andrea Siracusa 《Respiratory research》2009,10(1):1-20
The present document is the result of a consensus reached by a panel of experts from European and non-European countries on Occupational Rhinitis (OR), a disease of emerging relevance which has received little attention in comparison to occupational asthma. The document covers the main items of OR including epidemiology, diagnosis, management, socio-economic impact, preventive strategies and medicolegal issues. An operational definition and classification of OR tailored on that of occupational asthma, as well as a diagnostic algorithm based on steps allowing for different levels of diagnostic evidence are proposed. The needs for future research are pointed out. Key messages are issued for each item. 相似文献
956.
Rasmus Skern-Mauritzen Petter Frost Sussie Dalvin Bj?rn Olav Kvamme Ingunn Sommerset Frank Nilsen 《BMC molecular biology》2009,10(1):44
Background
Trypsin-like serine proteases are involved in a large number of processes including digestive degradation, regulation of developmental processes, yolk degradation and yolk degradome activation. Trypsin like peptidases considered to be involved in digestion have been characterized in Lepeophtheirus salmonis. During these studies a trypsin-like peptidase which differed in a number of traits were identified. 相似文献957.
The aggregation of a soluble protein into insoluble, β-sheet rich amyloid fibrils is a defining characteristic of many neurodegenerative diseases, including prion disorders. The prion protein has so far been considered unique because of its infectious nature. Recent investigations, however, suggest that other amyloidforming proteins associated with much more common diseases, such as tau, α-synuclein, amyloid β and polyglutamine proteins, while not infectious in the classical sense, share certain essential properties with prions that may explain phenotypic diversity, and patterns of spread within the nervous system. We suggest a common mechanism of pathogenesis of myriad sporadic and inherited neurodegenerative diseases based on templated conformational change.Key words: tau, prion, amyloid beta, α-synuclein, polyglutamine, neurodegeneration, fibril, propagation 相似文献
958.
959.
The release of fatty acids from membrane glycerolipids has been implicated in a variety of cellular processes, but the enzymes involved and their regulation are poorly understood in plants. One large group of acyl-hydrolyzing enzymes is structurally related to patatins. Patatins are potato tuber proteins with acyl-hydrolyzing activity, and the patatin catalytic domain is widely spread in bacterial, yeast, plant and animal enzymes. Recent results have indicated that patatin-related enzymes are involved in different cellular functions, including plant responses to auxin, elicitors or pathogens, and abiotic stresses and lipid mobilization during seed germination. In this review, we highlight recent developments regarding these enzymes and propose the nomenclature pPLA for the patatin-related phospholipase A enzyme. 相似文献
960.
Fungal antagonists of the plant pathogen Rhizoctonia solani: selection, control efficacy and influence on the indigenous microbial community 总被引:1,自引:0,他引:1
Rita Grosch Katja Scherwinski Jana Lottmann Gabriele Berg 《Mycological Research》2006,110(12):1464-1474
A broad spectrum of fungal antagonists was evaluated as potential biocontrol agents (BCAs) against the soil-borne pathogen Rhizoctonia solani using a new combination of in vitro and in vivo assays. The in vitro characterisation of diverse parameters including the ability to parasitise mycelium and to inhibit the germination of Rhizoctonia sclerotia at different temperatures resulted in the selection of six potential fungal antagonists. These were genotypically characterised by their BOX-PCR fingerprints, and identified as Trichoderma reesei and T. viride by partial 18S rDNA sequencing. When potato sprouts were treated with Trichoderma, all isolates significantly reduced the incidence of Rhizoctonia symptoms. Evaluated under growth chamber conditions, the selected Trichoderma isolates either partly or completely controlled the dry mass loss of lettuce caused by R. solani. Furthermore, the antagonistic Trichoderma strains were active under field conditions. To analyse the effect of Trichoderma treatment on indigenous root-associated microbial communities, we performed a DNA-dependent SSCP (Single-Strand Conformation Polymorphism) analysis of 16S rDNA/ITS sequences. In this first assessment study for Trichoderma it was shown that the pathogen and the vegetation time had much more influence on the composition of the microbiota than the BCA treatment. After evaluation of all results, three Trichoderma strains originally isolated from Rhizoctonia sclerotia were selected as promising BCAs. 相似文献