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31.
Freeze cleaving electron microscopy has shown that fusion of isolated secretory vesicles from bovine neurohypophyses was induced by Ca2+ in micromolar concentrations. Mg2+ and Sr2+ were ineffective. Mg2+ inhibited Ca2+-induced fusion.In suspensions containing secretory vesicles as well as sheets of cell membrane, release of vasopressin parallel to intervesicular fusion of secretory vesicles with sheets of cell membrane was observed after exposure to Ca2+. Mg2+ and Sr2+ were ineffective in replacing Ca2+ as trigger for fusion or vasopressin release.Intervesicular fusion and exocytotic profiles were observed when isolated neurohypophyses or neurosecretosome were exposed to cold. 相似文献
32.
Niels H. Andersen Shoji Imamoto Donald H. Picker 《Prostaglandins & other lipid mediators》1977,14(1):61-101
With the report given herein all diastereomers of PGF2, PGE2, and PGD2 which bear the naturally recognized 15-S hydroxylated center, whether in the natural or -prostanoic acid skeleton, have been prepared by a route involving initial introduction of the carboxyl (α) chain (1). A major advantage of the initial α-ylation+ route is the facile reduction of the 13,14-en-15-one system with methanolic NaBH4 which proceeds without competing 1,4-reduction. The products are thus free of 13,14-dihydro-PG2 contaminants (2). The initial pharmaco logical evaluation of these diastereomers will be submitted for publication in this journal (3). 相似文献
33.
Niels C. Krejci Lynne Smith Rebecca Rudd Robert Langdon Joseph McGuire 《In vitro cellular & developmental biology. Animal》1991,27(12):933-938
Summary To investigate the regulation of epithelial differentiation, normal human epidermal keratinocytes were cultured floating on
the surface of culture medium without attachment to a solid substrate. Keratinocytes spread out on the surface of the medium,
proliferated and differentiated either into several flat lacy sheets 1 to 3 cells thick (on medium containing 0.15 mM calcium) or formed one single aggregate of cells from 5 to 15 cells in thickness on medium containing 1.15 mM calcium. The cell aggregates demonstrated a pattern of ordered epithelial differentiation. Levels of progressive differentiation
resembling the structure of normal human epidermis were identified by light microscopy, immunohistochemistry, and electron
microscopy. Differentiation proceeded from cells at the air side toward cells at the medium side with basal appearing cells
on the air side and keratinocytes expressing filaggrin and involucrin on the side toward the medium. These results demonstrate
that organized epithelial differentiation can occur in the absence of extracellular matrix. In contrast with other air-liquid
interface cultures, epithelial differentiation in the absence of extracellular matrix progresses from air towards medium. 相似文献
34.
35.
Constance Vind Niels Grunnet 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1982,720(3):295-302
This paper describes the transfer of tritium from [2-3H]xylitol or (1R)-[1-3H]ethanol into lactate in cells from fed rats either untreated or triiodothyronine-treated. The labelling pattern of lactate during the metabolism of [2-3H]xylitol or (1R)-[1-3H]ethanol follows the equation (μmol tritium/μmol lactate). The yield in lactate together with the minimum value of the total flux of reducing equivalents are used to estimate the specific radioactivity of NADH. We have calculated the lactate dehydrogenase-catalysed oxidation rate of NADH from the experimental values of lactate labelling and the specific radioactivity of NADH. We found the calculated flux of reducing equivalents from NADH to pyruvate to be of the same order of magnitude whether labelled ethanol or labelled xylitol was metabolized. We found the flux to be only a few percent of the maximal activity of lactate dehydrogenase. The results obtained suggest that the cytoplasm can be regarded as one compartment, containing a single pool of NAD(H). 相似文献
36.
Steen Pedersen Solveig V. Reeh Jack Parker Robert J. Watson James D. Friesen Niels P. Fiil 《Molecular & general genetics : MGG》1976,144(3):339-343
Summary The presence of EF-Tu, RNA polymerase subunit , and EF-G on the dfus-3 genome and EF-Tu, ribosomal proteins L7/L12, and RNA polymerase subunit on the drif
d
18 genome has been confirmed using a two-dimensional gel electrophoresis technique sensitive to changes in isoelectric point and molecular weight. In this system two EF-Tu gene products could not be resolved. Following infection of ultraviolet light-irradiated Escherichia coli with either dfus-3 or drif
d
18, the EF-Tu gene, tufA, near 65 minutes on the genetic map is expressed as 3–4 copies per EF-G molecule. The EF-Tu gene, tufB, near 79 minutes on the genetic map, is expressed at about one-third of this rate. is expressed as 1 copy per EF-G molecule, as 0.14 per EF-G molecule and L7/L12 as 2.5 per EF-G. These figures compare well with the relative amounts found in exponentially-growing cells, in which the ratio of EF-Tu to EF-G is approximately 5. Almost 90% of the total number of proteins (calculated on a molecular weight basis) which theoretically can be encoded on the drif
d
18 have been identified on the two-dimensional gel. 相似文献
37.
CYTODYNAMICS IN THE THYMUS OF YOUNG ADULT MICE: 总被引:1,自引:0,他引:1
Cell proliferation and cell loss in the thymic blast cell population were studied in young adult mice by (1) stathmokinetic methods combined with an analysis of the PLMe-curve after a pulse 3H-TdR, and (2) nigrosin-dye exclusion combined with 3H-TdR-autoradiography. It was calculated that about 17% of the blast cells do not progress into mitosis within the period of an average cell cycle. The dye exclusion studies indicated a rate of blast cell death of about 2–5 %/hr. The two methods of assessing blast cell loss (death) support each other very well. In spite of these findings scintillation countings on thymuses removed from 1 to 17 hr after 3H-TdR injection showed fairly constant levels of thymic radioactivity. This suggests a very extensive reutilization of 3H-labelled break-down products from dying blast cells. The very sparse labelling of pyknotic thymocytes strongly suggests that thymic blast cells do not become pyknotic. The rate of small thymocyte production and disappearance was studied by pulse and repeated 3H-TdR labelling techniques combined with dye exclusion studies and pyknotic counts. The data from the repeated labelling experiment were analysed by use of a model based on the assumption of first order kinetics of small viable, dead, and pyknotic thymocytes. The rate of cell production was estimated to 1–6 %/hr whereas the rates of cell loss due to disintegration, i.e. supravital stainability and nuclear pyknosis, were calculated to 0–02 %/hr and 0–0006 %/hr respectively. Cell loss due to disintegration was less than 2 % of the total loss of small thymocytes. It was concluded that pyknotic counts are a useless method of assessing the cell death in the population of thymic blast cells and small thymocytes. On the basis of a model for thymocyte proliferation, production and loss it is suggested that about 45 % of the small viable thymocytes re-enter the generative cell pool, whereas about 55% disappear by emigration. 相似文献
38.
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40.
Melanie Krüger RoosAnne Samsom Loes A. Oosterhoff Monique E. van Wolferen Hans S. Kooistra Niels Geijsen Louis C. Penning Linda M. Kock Pilar SainzArnal Pedro M. Baptista Bart Spee 《Journal of cellular and molecular medicine》2022,26(19):4949
In Europe alone, each year 5500 people require a life‐saving liver transplantation, but 18% die before receiving one due to the shortage of donor organs. Whole organ engineering, utilizing decellularized liver scaffolds repopulated with autologous cells, is an attractive alternative to increase the pool of available organs for transplantation. The development of this technology is hampered by a lack of a suitable large‐animal model representative of the human physiology and a reliable and continuous cell source. We have generated porcine intrahepatic cholangiocyte organoids from adult stem cells and demonstrate that these cultures remained stable over multiple passages whilst retaining the ability to differentiate into hepatocyte‐ and cholangiocyte‐like cells. Recellularization onto porcine scaffolds was efficient and the organoids homogeneously differentiated, even showing polarization. Our porcine intrahepatic cholangiocyte system, combined with porcine liver scaffold paves the way for developing whole liver engineering in a relevant large‐animal model. 相似文献