全文获取类型
收费全文 | 565篇 |
免费 | 36篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 35篇 |
2020年 | 21篇 |
2019年 | 13篇 |
2018年 | 28篇 |
2017年 | 21篇 |
2016年 | 23篇 |
2015年 | 27篇 |
2014年 | 36篇 |
2013年 | 52篇 |
2012年 | 49篇 |
2011年 | 41篇 |
2010年 | 29篇 |
2009年 | 26篇 |
2008年 | 27篇 |
2007年 | 22篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有602条查询结果,搜索用时 17 毫秒
531.
Napoli I Mercaldo V Boyl PP Eleuteri B Zalfa F De Rubeis S Di Marino D Mohr E Massimi M Falconi M Witke W Costa-Mattioli M Sonenberg N Achsel T Bagni C 《Cell》2008,134(6):1042-1054
Strong evidence indicates that regulated mRNA translation in neuronal dendrites underlies synaptic plasticity and brain development. The fragile X mental retardation protein (FMRP) is involved in this process; here, we show that it acts by inhibiting translation initiation. A binding partner of FMRP, CYFIP1/Sra1, directly binds the translation initiation factor eIF4E through a domain that is structurally related to those present in 4E-BP translational inhibitors. Brain cytoplasmic RNA 1 (BC1), another FMRP binding partner, increases the affinity of FMRP for the CYFIP1-eIF4E complex in the brain. Levels of proteins encoded by known FMRP target mRNAs are increased upon reduction of CYFIP1 in neurons. Translational repression is regulated in an activity-dependent manner because BDNF or DHPG stimulation of neurons causes CYFIP1 to dissociate from eIF4E at synapses, thereby resulting in protein synthesis. Thus, the translational repression activity of FMRP in the brain is mediated, at least in part, by CYFIP1. 相似文献
532.
Zaira Ianniello Melissa Sorci Lavinia Ceci Ginistrelli Alessia Iaiza Marcella Marchioni Claudia Tito Ernestina Capuano Silvia Masciarelli Tiziana Ottone Cristina Attrotto Manuela Rizzo Luca Franceschini Stefano de Pretis Maria Teresa Voso Mattia Pelizzola Francesco Fazi Alessandro Fatica 《Cell death & disease》2021,12(10)
533.
In contrast to most chelonians, the fully aquatic soft-shelled turtles have a smooth, unscaled, and pliable shell. The skin of the shell, tail, limbs, and neck of juveniles of Trionyx spiniferus has been studied by ultrastructural, immunocytochemical, and immunoblotting methods. The epidermis of the carapace and plastron has a thick corneous layer composed of alpha-corneocytes surrounded by a cornified cell envelope. The softer epidermis is similar to that of the shell but the epidermis and corneous layer are much thinner. Pre-corneous cells in both soft and shell epidermis are rich in vesicles produced in the Golgi apparatus and smooth endoplasmic vesicles, and contain numerous dense-core mucus-like and vesicular (lamellar) bodies. Secreted material is present among corneocytes where it probably forms an extensive intercellular lipid-mucus waterproof barrier. The dermis is very thick and composed of several layers of collagen bundles that form a plywood-patterned dermis. This dermis constitutes a strong mechanical barrier that compensates for the low content in beta-keratin, and lack of cornified scutes and dermal bones. The growth of the shell mainly occurs along the lateral margins. Immunocytochemistry reveals the presence of some beta-keratin in soft and shell epidermis, and this is confirmed by immunoblotting where bands at 18 and 32-35 kDa are present. Other proteins of the cornified cell envelope (loricrin and sciellin) or associated to lipid trafficking (caveolin-1) are also detected by immunoblotting. Loricrin positive bands at 24 and 57 kDa are present while bands cross-reactive for sciellin are seen at 45 and 53 kDa. Caveolin-1 positive bands are seen at 21-22 kDa. The presence of these proteins indicates that the epidermis is both coriaceous and waterproof. These results suggest that the shell of Trionyx is tough enough to be as mechanically efficient as the hard shell of the other turtles. At the same time, a soft shell is lighter, its shape is more easily controlled by muscles, and it allows a more controlled closure and retraction of limbs and neck inside the shell. Thus, the shell makes the animal more streamlined for swimming. 相似文献
534.
The contribution of nociceptin/orphanin FQ (N/OFQ) to reserpine-induced Parkinsonism was evaluated in mice. A battery of motor tests revealed that reserpine caused dose-dependent and long-lasting motor impairment. Endogenous N/OFQ sustained this response because N/OFQ peptide (NOP) receptor knockout (NOP(-/-) ) mice were less susceptible to the hypokinetic action of reserpine than wild-type (NOP(+/+) ) animals. Microdialysis revealed that reserpine elevated glutamate and reduced GABA levels in substantia nigra reticulata, and that resistance to reserpine in NOP(-/-) mice was accompanied by a milder increase in glutamate and lack of inhibition of GABA levels. To substantiate this genetic evidence, the NOP receptor antagonist 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H benzimidazol-2-one (J-113397) simultaneously reduced akinesia and nigral glutamate levels in reserpinized NOP(+/+) mice, being ineffective in NOP(-/-) mice. Moreover, repeated J-113397 administration in reserpinized mice resulted in faster recovery of baseline motor performance which was, however, accompanied by a loss of acute antiakinetic response. The short-term beneficial effect of J-113397 was paralleled by normalization of nigral glutamate levels, whereas loss of acute response was paralleled by loss of the ability of J-113397 to inhibit glutamate levels. We conclude that endogenous N/OFQ contributes to reserpine-induced Parkinsonism, and that sustained NOP receptor blockade produces short-term motor improvement accompanied by normalization of nigral glutamate release. 相似文献
535.
Brambilla M Vitulano S Spina F Baccetti N Gargallo G Fabbri E Guidali F Randi E 《Molecular phylogenetics and evolution》2008,48(2):461-472
The subalpine warbler Sylvia cantillans is formally considered a polytypic species, with four subspecies, European S. c. cantillans, albistriata, moltonii (recently resumed name: subalpina) and North African S. c. inornata. They are very similar in external morphology but clearly differ in their vocalizations. We evaluated their uncertain taxonomic status reconstructing the phylogenetic and phylogeographic relationships among populations sampled across major biogeographical areas in the European species’ range, using nucleotide sequences of the mitochondrial cytochrome b gene (mtDNA cyt b). A variety of phylogenetic analyses concordantly led to identify four major groups, only partially corresponding to the three European nominal subspecies. Phylogenetic trees showed a monophyletic group including all moltonii individuals, well diverged from all other taxa. Populations taxonomically assigned to cantillans were polyphyletic being split into two distinct clades (western and southern cantillans), with monophyletic albistriata closely related to southern cantillans. Individuals of moltonii and southern cantillans sampled in sites of sympatry in central Italy were assigned to their respective groups, with perfect concordance between phenotypic and genetic identifications. All findings indicate that moltonii should be ranked as a distinct species. Former subspecies cantillans is polyphyletic, but additional data are needed to define the taxonomic status of its two clades. Albistriata is phylogenetically related to southern cantillans and should be provisionally kept as a subspecies of S. cantillans. The cantillans complex thus provides an interesting case-study illustrating geographical structuring across small geographical ranges, and it exemplifies speciation through differentiation in allopatry leading to reproductive isolation after a secondary contact. 相似文献
536.
Conte C Gambardella S Bulli C Rinaldi F Di Marino D Falconi M Bramanti P Desideri A Novelli G 《Genetic testing》2008,12(3):437-442
Mutations within EDA1 gene, which encodes for the ectodysplasin, cause X-linked anhidrotic ectodermal dysplasia. In this study, 23 Italian patients with anhidrotic ectodermal dysplasia were analyzed for mutations in EDA1 gene. We set up a rapid protocol through denaturing high-performance liquid chromatography, followed by sequencing, that allowed the characterization of 18 mutations, 14 novel and 4 recurrent: 8 missense mutations (p.L51Q, p.H54R, p.R156H twice, p.C332F, p.D316H, p.T378M, and p.A349T), 3 in-frame deletions (p.G82_P84del, p.A179_P191del, and p.L354del), 1 gross deletion (p.G168_G265del, identified through direct sequencing and PCR), 4 altered splicing (c.949-13T > C, c.741 + 1G/T, c.793 + 4A > T, and c.924 + 1G/T), 1 nonsense (p.Y3X), and 1 synonymous mutation (c.741G > A). Moreover, structural analysis of three missense mutations shows that alteration of the electrostatic surface of the protein (p.D316N), the break of intermonomer interactions (p.A349T) and destabilization of the single monomer structure (p.T378M), may irreversibly invalidate the EDA-A1 binding properties. Our data confirm and extend the large spectrum of EDA1 mutations and provide a rapid and efficient molecular protocol for testing EDA1 mutations in EDA patients. 相似文献
537.
Fabrizio De Mattia Serena Imazio Fabrizio Grassi Hamed Doulati Baneh Attilio Scienza Massimo Labra 《Rendiconti Lincei》2008,19(3):223-240
Archaeobotanical-archaeological, cultural and historical data indicate that grapevine domestication can be dated back from
6000 to 7000 years ago and that it took place in the Caucasian and Middle East Regions. However, events leading to the domestication
of this crop species are still an open issue. In this paper, 6 chloroplast microsatellites have been used to assess genetic
similarities among, and within, domesticated and wild grapevine accessions representative of 7 distinct geographical regions
from the Middle-East to Western Europe. Results show that 2 out of the 6 analyzed chloroplast loci are polymorphic within
the 193 domesticated individuals and the 387 samples of 69 wild populations. Allele variants of the Cp-SSR loci combine in
a total of 6 different haplotypes. The data show that the haplotype distribution is not homogeneous: the 6 haplotypes are
present in the domesticated varieties, but only 5 (haplotype VI is absent) are observed in wild populations. The analysis
of haplotype distribution allows discussion of the relationships between the two grape subspecies. The contribution of the
wild grape germplasm to the domesticated gene pool still growing in different geographical regions can be, in cases, made
evident, suggesting that beside domestication, gene introgression has also played a role in shaping the current varietal landscape
of the European viticulture.
相似文献
相似文献
538.
M. Lepore M. Portaccio E. De Tommasi P. De Luca U. Bencivenga P. Maiuri D.G. Mita 《Journal of Molecular Catalysis .B, Enzymatic》2004,31(4-6):151-158
By using soluble and insoluble glucose oxidase, the changes in intrinsic emission fluorescence in the visible spectral region were studied as a function of glucose concentration. Insoluble glucose oxidase (GOD) was obtained by entrapment in a gelatine membrane or by covalent attachment on an agarose membrane grafted with hexamethylendiamine. The intensity of the fluorescence emission peak at 520 nm or the value of the integral fluorescence area from 480 to 580 nm were taken as physical parameters representative of the glucose concentration during the enzyme reaction. By using these parameters, linear calibration curves for glucose concentration were obtained. The extension of the calibration curve and the sensitivity of the adopted systems were found to be dependent on the enzyme state (free or immobilized) and on the immobilization method. In particular, it was found that the extent of the linear range of the calibration curves is increased of one order of magnitude when the glucose oxidase is immobilized, while the sensitivity of the measure is decreased of one order of magnitude by the immobilization process. Measures carried out by using the integral fluorescence area resulted more sensitive than those obtained with the peak size. Useful indications for the construction of optical fibre-based sensors were drawn from the reported results. 相似文献
539.
Fulciniti F Di Mattia D Bove P Mastro AA De Chiara A Botti G Petrillo A Apice G 《Acta cytologica》2008,52(5):612-618
BACKGROUND: Epithelioid angiosarcomas (EAs) are uncommon mesenchymal tumors occurring in the thyroid, deep-seated soft tissues, parenchymal organs and, more rarely, superficial soft tissues of the head and neck. Due to their cytologic and immunocytochemical presentation on fine needle aspiration cytology (FNAC) samples, these neoplasms may closely mimic a number of different tumors, potentially causing an erroneous cytopathologic diagnosis unless immunophenotypical markers of vascular differentiation are sought in the cellular material. CASES: A 68-year-old man with a 1-year history of total thyroidectomy for EA presented with a suspicious right neck node and underwent FNA. A 63-year-old woman with a history of recurring multiple scalp nodules diagnosed as EA ultimately developed small multiple, bilateral lymph nodes in the neck and underwent FNA. In both cases a cytopathologic diagnosis of metastatic EA was made. CONCLUSION: The cytopathologic diagnosis of EA is a challenge. Knowledge of the clinical history is of great help in diagnosing metastatic lesions. The cytopathologicpicture of metastases is a useful way for cytopathologists to gain confidence with presentaton of this rare entity in primary sites on FNAC samples. Cytopathologic hints of vascular differentiation should be sought in the cytopathologic material when a diagnosis of EA is entertained. 相似文献
540.