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21.
22.
Teresa Teruel Angela M. Valverde Manuel Benito Margarita Lorenzo 《Journal of cellular physiology》1996,166(3):577-584
The presence of transforming growth factor β1 (TGF-β1) for 24 or 48 h stimulated DNA synthesis, the percentage of cells in the S + G2/M phases of the cell cycle, and cell number, as compared to quiescent cells. The mitogenic capacity of TGF-β1 (1 pM) was similar to that shown by 10% fetal calf serum (FCS). TGF-β1 for 48 h increased by 5-fold the percentage of cells containing (3H)thymidine-labeled nuclei as compared to quiescent cells. In addition, single fetal brown adipocytes, showing their typical multilocular fat droplets phenotype, become positive for (3H)thymidine-labeled nuclei in response to TGF-β1. Moreover, TGF-β1 induced the mRNA expression of a complete set of proliferation-related genes, such as c-fos (30 min), c-myc and β-actin (2 h), and H-ras, cdc2 kinase, and glucose 6-phosphate dehydrogenase (G6PD) at 4 and 8 h, as compared to quiescent cells. Concurrently, TGF-β1 for 12 h increased the protein content of proliferating cellular nuclear antigen (PCNA) by 6-fold and p21-ras by 2-fold. Although our results demonstrate that TGF-β1 induces the expression of very early genes related to cell proliferation, TGF-β1 could be acting either as a mitogen or as a survival factor to induce proliferation in fetal brown adipocytes. © 1996 Wiley-Liss, Inc. 相似文献
23.
María Prez-Caro Csar Cobaleda Ins Gonzlez-Herrero Carolina Vicente-Dueas Camino Bermejo-Rodríguez Margarita Snchez-Beato Alberto Orfao Beln Pintado Teresa Flores Manuel Snchez-Martín Rafael Jimnez Miguel A Piris Isidro Snchez-García 《The EMBO journal》2009,28(1):8-20
In human cancers, all cancerous cells carry the oncogenic genetic lesions. However, to elucidate whether cancer is a stem cell-driven tissue, we have developed a strategy to limit oncogene expression to the stem cell compartment in a transgenic mouse setting. Here, we focus on the effects of the BCR-ABLp210 oncogene, associated with chronic myeloid leukaemia (CML) in humans. We show that CML phenotype and biology can be established in mice by restricting BCR-ABLp210 expression to stem cell antigen 1 (Sca1)+ cells. The course of the disease in Sca1-BCR-ABLp210 mice was not modified on STI571 treatment. However, BCR-ABLp210-induced CML is reversible through the unique elimination of the cancer stem cells (CSCs). Overall, our data show that oncogene expression in Sca1+ cells is all that is required to fully reprogramme it, giving rise to a full-blown, oncogene-specified tumour with all its mature cellular diversity, and that elimination of the CSCs is enough to eradicate the whole tumour. 相似文献
24.
Effects of nutrients and fish on periphyton and plant biomass across a European latitudinal gradient
Eloy Bécares Joan Gomá Margarita Fernández-Aláez Camino Fernández-Aláez Susana Romo Maria R. Miracle Anika Ståhl-Delbanco Lars-Anders Hansson Mykael Gyllström Wouter J. Van de Bund Ellen Van Donk Timo Kairesalo Jaana Hietala Debbie Stephen David Balayla Brian Moss 《Aquatic Ecology》2008,42(4):561-574
Replicated, factorial mesocosm experiments were conducted across Europe to study the effects of nutrient enrichment and fish
density on macrophytes and on periphyton chlorophyll a (chl-a) with regard to latitude. Periphyton chl-a densities and plant decline were significantly related to nutrient loading in all countries. Fish effects were significant
in a few sites only, mostly because of their contribution to the nutrient pool. A saturation-response type curve in periphyton
chl-a with nutrients was found, and northern lakes achieved higher densities than southern lakes. Nutrient concentration and phytoplankton
chl-a necessary for a 50% plant reduction followed a latitudinal gradient. Total phosphorus values for 50% plant disappearance
were similar from Sweden (0.27 mg L−1) to northern Spain (0.35 mg L−1), but with a sharp increase in southern Spain (0.9 mg L−1). Planktonic chl-a values for 50% plant reduction increased monotonically from Sweden (30 μg L−1) to València (150 μg L−1). Longer plant growing-season, higher light intensities and temperature, and strong water-level fluctuations characteristic
of southern latitudes can lead to greater persistence of macrophyte biomass at higher turbidities and nutrient concentration
than in northern lakes. Results support the evidence that latitudinal differences in the functioning of shallow lakes should
be considered in lake management and conservation policies. 相似文献
25.
M. Gabriela Mángano Noelia B. Carmona Luis A. Buatois Fernando Muñiz Guinea 《Ichnos》2013,20(3):179-190
A new ichnospecies of Arthrophycus Hall 1852, A. minimus , is described from Upper Cambrian-Lower Tremadocian, shallow-marine strata of northwest Argentina. This new ichnospecies consists of small, long, regularly annulated hypichnial elements displaying subcircular to squarish cross-section and a ventral median groove. Side branches are occasionally present, but palmate, fan-like structures and scribbling patterns are absent. We adopt a relatively narrow diagnosis of Arthrophycus , suggesting that roughly annulated, cylindrical structures should not be included in this ichnogenus, unless other diagnostic features (i.e., squarish cross-section, median groove, zipper-like annulations) are also present. Arthrophycus is a common ichnotaxon in Ordovician-Silurian shallow-marine siliciclastic environments. Post-Paleozoic occurrences are removed from Arthrophycus . Arthrophycus has been proposed as a biostratigraphic index fossil in Ordovician-Silurian rocks. The presence of A. minimus in the Santa Rosita Formation of northwest Argentina indicates that Arthrophycus ranges at least from the Upper Cambrian-Lower Tremadocian with probable representatives in the Lower Cambrian and, therefore, its biostratigraphic utility is extended. Arthrophycus minimus represents the first Cambrian occurrence exhibiting not only fine, diagnostic morphologic features, but also the classical Arthrophycus behavioral pattern in dense monoichnospecific assemblages. The exploratory behavioral pattern displayed by A. minimus is simpler than that of the younger ichnospecies, particularly A. brogniartii, A. alleghaniensis, and A. lateralis . This is consistent with the basal position of A. minimus within the arthrophycid lineage. 相似文献
26.
UV-B-induced damage and photoreactivation in three species of Boeckella (Copepoda, Calanoida) 总被引:2,自引:0,他引:2
Zagarese Horacio E.; Feldman Margarita; Williamson Craig E. 《Journal of plankton research》1997,19(3):357-367
Solar ultraviolet (UV) radiation poses a threat to most livingorganisms. Aquatic organisms have evolved three basic mechanismsto cope with harmful levels of radiation. Two mechanisms, avoidance(e.g. vertical migration) and photoprotection (e.g. productionof photoprotective compounds that act as filters, antioxidants,etc.), serve to minimize the dose of UV radiation that reachesthe organism's vital structures (DNA, membranes, etc.). Thethird mechanism, repair (e.g. dark repair mechanisms, such asnucleotide excision repair; or photoreactivation mechanisms,such as photoenzymatic repair), serves to repair the damagefollowing UV exposure. Here, we compare the vulnerability toUV-B radiation of three copepod species (Boeckella brevicaudata,Boeckella gibbosa, and Boeckella gracilipes) that occur in lakesthat differ in UV-B penetration and depth. Our aim was to gaininsight into the significance of each of the three mechanismsin different UV-B environments. Results from a 3-day insitu incubation in ultra-oligotrophic Lake Toncek showedthat B.gracilipes is highly vulnerable to UV-B and UV-A radiation.In contrast, virtually no mortality was observed in B.gibbosaand B.brevicaudata during the same period. In order to discriminatethe contribution of photoprotection and photoreactivation, thethree species were subsequently exposed in the laboratory toan artificial source of UV-B radiation, both in the presenceand absence of visible radiation (recovery radiation). The photoprotectionpotential (i.e. resistance to UV-B in the absence of recoveryradiation) of B.gracilipes and B.gibbosa was lower than thatof B.brevicaudata. On the other hand, photoreactivation (higherresistance to UV-B in the presence of recovery radiation) wasobserved in B.brevicaudata and B.gibbosa, but not in B.gracilipes.To cope with damaging UV-B levels in nature, B.gracilipes dependsexclusively on the attenuation by the external media (i.e. avoidance).Although B.gibbosa tends to avoid the surface waters of lakes,it also occurs in shallow transparent pools. Most likely itsability to survive in these shallow, high UV environments isdue to its photoreactivation potential. Finally, despite itsoccurrence in highly turbid lakes, B.brevicaudata seems extremelywell suited to cope with UV-B radiation thanks to a combinationof photoreactivation and photoprotection. 相似文献
27.
D Barettino G Morcillo J L Díez M T Carretero M J Carmona 《Biochimie et biologie cellulaire》1988,66(11):1177-1185
28.
Summary Capillaries, pericytes and microglial cells in layer I of the cerebral cortex of normal adult cats have been studied with electron microscopy. The data obtained in this study show that pericytes are cells which are able to transform themselves into microglial cells by virtue of an activation process in which the astrocytic neuroglia appears to play a decisive role. By virtue of its structure, its mesodermic origin and its function the microglia has to be distinguished clearly from the astrocytic neuroglia and the oligodendroglia.This study was partly supported by a grant from the Seguridad Social, Instituto Nacional de Previsión. 相似文献
29.
Metal‐Oxide‐Free Methylammonium Lead Iodide Perovskite‐Based Solar Cells: the Influence of Organic Charge Transport Layers 下载免费PDF全文
Olga Malinkiewicz Cristina Roldán‐Carmona Alejandra Soriano Enrico Bandiello Luis Camacho Mohammad Khaja Nazeeruddin Henk J. Bolink 《Liver Transplantation》2014,4(15)
Metal‐oxide‐free methylammonium lead iodide perovskite‐based solar cells are prepared using a dual‐source thermal evaporation method. This method leads to high quality reproducible films with large crystal domain sizes allowing for an in depth study of the effect of perovskite film thickness and the nature of the electron and hole blocking layers on the device performance. The power conversion efficiency increases from 4.7% for a device with only an organic electron blocking layer to almost 15% when an organic hole blocking layer is also employed. In addition to the in depth study on small area cells, larger area cells (approx. 1 cm?2) are prepared and exhibit efficiencies in excess of 10%. 相似文献
30.
Miguel Amzquita Geny Carolina Silva Diego Antonio Restrepo Linda Margarita Ibata Rafael Nio Maximiliano Bustacara Víctor Alexander Senz Dieric Anderson Díaz Milena Alarcn Luz Adriana Quintero 《Biomédica : revista del Instituto Nacional de Salud》2022,42(2):290