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211.
Ultrastructure of the female gonad of two temnocephalids (Platyhelminthes,Rhabdocoela) 总被引:2,自引:2,他引:0
The female gonad of Temnocephala dendyi and T. minor consists of a single germarium and two rows of vitellaria. It is enveloped
by an extracellular lamina and accessory cells. Accessory cells are only peripherally located in the germarium while their
cytoplasmic projections also fill the spaces between vitellocytes in the vitellarium. The main feature of oocyte maturation
is the appearance of chromatoid bodies and the development of rough endoplasmic reticulum (R.E.R.) and Golgi complexes which
appear to be correlated with the production of double-structured egg granules. The egg granules, which are localized in the
cortical cytoplasm of mature oocytes, contain glycoproteins, are devoid of polyphenols and are similar in structure and composition
to the cortical granules observed in some Digenea and Monogenea. Vitellocytes are typical secretory cells with well-developed
R.E.R. and Golgi complexes which are involved in the production of shell globules and yolk. The multigranular pattern and
the polyphenolic composition of the shell globules of the temnocephalids investigated are similar to those observed in other
rhabdocoels, and in some Prolecithophora and Neodermata. This feature may represent a synapomorphy shared by these taxa.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
212.
Alessandra de Cupis Paolo Pirani Laura Fazzuoli Roberto E. Favoni 《In vitro cellular & developmental biology. Animal》1998,34(10):836-843
Summary Growth rate, morphology, and responsiveness to mitogenic stimuli and pharmacological treatments were evaluated in early and
late cell passages derived from the same clone of the widely used MCF-7 human breast adenocarcinoma cell line. Our results
indicate dissimilarities between early (E) and late (L) passages for some of the parameters analyzed. The cells that underwent
many subcultivations grew faster than the others; both appeared homogeneous in size and shape. The E cells, subcultured for
almost 1 yr, displayed higher sensitivity to the mitogenic action of both estradiol, according to the level of estrogen receptor,
and insulin-like growth factor-I than did the L cells, kept in culture for more than 10 yr. Cell responsiveness to two drugs,
a novel steroid antiestrogen and a polysulfonated distamycin A derivative, was more pronounced in the early cultures only
at the longer time of exposure to the higher concentration of the estrogen antagonist. In addition, a drug-induced inhibition
of insulin-like growth factor-I binding to its receptor was shown in both E and L cells, the latter being less sensitive than
the former when exposed to the antiestrogen. Finally, MCF-7 E and L cells showed similar behavior when drug-induced apoptosis
was tested. 相似文献
213.
Isabella Di Lernia Alessandra Morana Antonio Ottombrino Stefania Fusco Mosè Rossi M. De Rosa 《Extremophiles : life under extreme conditions》1998,2(4):409-416
Enzymes that convert starch and dextrins to α,α-trehalose and glucose were found in cell homogenates of the hyperthermophilic
acidophilic archaeon Sulfolobus shibatae DMS 5389. Three enzymes were purified and characterized. The first, the S. shibatae trehalosyl dextrin-forming enzyme (SsTDFE), transformed starch and dextrins to the corresponding trehalosyl derivatives with
an intramolecular transglycosylation process that converted the glucosidic linkage at the reducing end from α-1,4 to α-1,1.
The second, the S. shibatae trehalose-forming enzyme (SsTFE), hydrolyzed the α-1,4 linkage adjacent to the α-1,1 bond of trehalosyl dextrins, forming
trehalose and lower molecular weight dextrins. These two enzymes had molecular masses of 80 kDa and 65 kDa, respectively,
and showed the highest activities at pH 4.5. The apparent optimal temperature for activity was 70°C for SsTDFE and 85°C for
SsTFE. The third enzyme identified was an α-glycosidase (SsαGly), which catalyzed the hydrolysis of the α-1,4 glucosidic linkages
in starch and dextrins, releasing glucose in a stepwise manner from the nonreducing end of the polysaccharide chain. The enzyme
had a molecular mass of 313 kDa and showed the highest activity at pH 5.5 and at 85°C.
Received: October 29, 1997 / Accepted: April 29, 1998 相似文献
214.
Alessandra Gradi Hiroaki Imataka Yuri V. Svitkin Eran Rom Brian Raught Shigenobu Morino Nahum Sonenberg 《Molecular and cellular biology》1998,18(1):334-342
Mammalian eukaryotic translation initiation factor 4F (eIF4F) is a cap-binding protein complex consisting of three subunits: eIF4E, eIF4A, and eIF4G. In yeast and plants, two related eIF4G species are encoded by two different genes. To date, however, only one functional eIF4G polypeptide, referred to here as eIF4GI, has been identified in mammals. Here we describe the discovery and functional characterization of a closely related homolog, referred to as eIF4GII. eIF4GI and eIF4GII share 46% identity at the amino acid level and possess an overall similarity of 56%. The homology is particularly high in certain regions of the central and carboxy portions, while the amino-terminal regions are more divergent. Far-Western analysis and coimmunoprecipitation experiments were used to demonstrate that eIF4GII directly interacts with eIF4E, eIF4A, and eIF3. eIF4GII, like eIF4GI, is also cleaved upon picornavirus infection. eIF4GII restores cap-dependent translation in a reticulocyte lysate which had been pretreated with rhinovirus 2A to cleave endogenous eIF4G. Finally, eIF4GII exists as a complex with eIF4E in HeLa cells, because eIF4GII and eIF4E can be purified together by cap affinity chromatography. Taken together, our findings indicate that eIF4GII is a functional homolog of eIF4GI. These results may have important implications for the understanding of the mechanism of shutoff of host protein synthesis following picornavirus infection. 相似文献
215.
Giovanni Savettieri Giacoma Alessandra Mazzola Maria Belén Rodriguez Sanchez Giovanna Caruso Italia Di Liegro Alessandro Cestelli 《Cellular and molecular neurobiology》1998,18(4):369-378
1. Neuronal differentiation depends on crosstalk between genetic program and environmental cues. In this study we tried to dissect this complex interplay by culturing neurons from fetal rat brain cortices in a chemically defined, neuron-specific, medium and on different substrata, either artificial (poly-D-lysine) or natural.2. Among the extracellular matrix compounds used in this study, two (collagen I and fibronectin) allowed only a weak attachment of cortical neurons to the substratum, while the others (collagen IV, laminin, and basal lamina from Engelbreth-Holm-Swarm sarcoma) allowed both firm attachment and moderate to extensive neurite outgrowth from neuronal cell bodies.3. By using synapsin I gene expression as a parameter of neuronal differentiation, we found that neurite outgrowth and neuronal differentiation are not linearly linked. Synapsin I gene expression, in fact, was maximal in neurons cultured on laminin, while the fastest neuritic outgrowth was recorded in cultures on poly-D-lysine.4. The data presented in this paper are consistent with the hypothesis that the extracellular matrix plays an active role in modulating the differentiative program of neurons. 相似文献
216.
217.
Rosangela Guollo Damazio Ana Paula Zanatta Luisa Helena Cazarolli Alessandra Mascarello Louise Domeneghini Chiaradia Ricardo José Nunes Rosendo Augusto Yunes Fátima Regina Mena Barreto Silva 《Biochimie》2009,91(11-12):1493-1498
In this study, the in vivo and in vitro anti-hyperglycemic activity of chalcone derivatives of 3,4-methylenedioxy, with a substituent electron-acceptor nitro group in the A or B ring, was investigated. As expected, the second generation sulfonylurea glipizide stimulated insulin secretion and reduced glycemia over the study period. Also, it was demonstrated for the first time that chalcones are able to increase insulin secretion and this event was coincident with serum glucose-lowering in the oral glucose tolerance test. Additionally, the chalcones studied had a similar effect on insulin secretion and serum glucose-lowering as glipizide. The effect of chalcones in terms of inducing insulin secretion was greater than that of glipizide after 30 min. Moreover, chalcones were not able to stimulate glucose uptake in soleus muscle, either in the presence of insulin or in the absence of this hormone. In addition, the oral treatment with chalcones did not alter glycemia in diabetic rats. These reports indicate that the effect of chalcones on serum glucose-lowering in hyperglycemic-normal rats is mainly a consequence of insulin secretion, highlighting these chalcones as novel compounds with strong anti-hyperglycemic properties. 相似文献
218.
Flexible Perovskite Photovoltaic Modules and Solar Cells Based on Atomic Layer Deposited Compact Layers and UV‐Irradiated TiO2 Scaffolds on Plastic Substrates
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219.
Effect of Purified Murine NGF on Isolated Photoreceptors of a Rodent Developing Retinitis Pigmentosa
Maria Luisa Rocco Bijorn Omar Balzamino Pamela Petrocchi Passeri Alessandra Micera Luigi Aloe 《PloS one》2015,10(4)
A number of different studies have shown that neurotrophins, including nerve growth factor (NGF) support the survival of retinal ganglion neurons during a variety if insults. Recently, we have reported that that eye NGF administration can protect also photoreceptor degeneration in a mice and rat with inherited retinitis pigmentosa. However, the evidence that NGF acts directly on photoreceptors and that other retinal cells mediate the NGF effect could not be excluded. In the present study we have isolated retinal cells from rats with inherited retinitis pigmentosa (RP) during the post-natal stage of photoreceptor degenerative. In presence of NGF, these cells are characterized by enhanced expression of NGF-receptors and rhodopsin, the specific marker of photoreceptor and better cell survival, as well as neuritis outgrowth. Together these observations support the hypothesis that NGF that NGF acts directly on photoreceptors survival and prevents photoreceptor degeneration as previously suggested by in vivo studies. 相似文献
220.
Emiliano Mancini Maria Ida Spinaci Vasco Gordicho Beniamino Caputo Marco Pombi José Luis Vicente Jo?o Dinis Amabélia Rodrigues Vincenzo Petrarca David Weetman Jo?o Pinto Alessandra della Torre 《PloS one》2015,10(6)
“Far-West” Africa is known to be a secondary contact zone between the two major malaria vectors Anopheles coluzzii and A. gambiae. We investigated gene-flow and potentially adaptive introgression between these species along a west-to-east transect in Guinea Bissau, the putative core of this hybrid zone. To evaluate the extent and direction of gene flow, we genotyped site 702 in Intron-1 of the para Voltage-Gated Sodium Channel gene, a species-diagnostic nucleotide position throughout most of A. coluzzii and A. gambiae sympatric range. We also analyzed polymorphism in the thioester-binding domain (TED) of the innate immunity-linked thioester-containing protein 1 (TEP1) to investigate whether elevated hybridization might facilitate the exchange of variants linked to adaptive immunity and Plasmodium refractoriness. Our results confirm asymmetric introgression of genetic material from A. coluzzii to A. gambiae and disruption of linkage between the centromeric "genomic islands" of inter-specific divergence. We report that A. gambiae from the Guinean hybrid zone possesses an introgressed TEP1 resistant allelic class, found exclusively in A. coluzzii elsewhere and apparently swept to fixation in West Africa (i.e. Mali and Burkina Faso). However, no detectable fixation of this allele was found in Guinea Bissau, which may suggest that ecological pressures driving segregation between the two species in larval habitats in this region may be different from those experienced in northern and more arid parts of the species’ range. Finally, our results also suggest a genetic subdivision between coastal and inland A. gambiae Guinean populations and provide clues on the importance of ecological factors in intra-specific differentiation processes. 相似文献