全文获取类型
收费全文 | 491篇 |
免费 | 31篇 |
专业分类
522篇 |
出版年
2023年 | 8篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 14篇 |
2015年 | 27篇 |
2014年 | 21篇 |
2013年 | 43篇 |
2012年 | 36篇 |
2011年 | 37篇 |
2010年 | 31篇 |
2009年 | 17篇 |
2008年 | 26篇 |
2007年 | 30篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 26篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有522条查询结果,搜索用时 9 毫秒
71.
Alan Agresti Atalanta Ghosh Matilde Bini 《Biometrical journal. Biometrische Zeitschrift》1995,37(7):811-820
Several authors have noted the dependence of kappa measures of inter-rater agreement on the marginal distributions of contingency tables displaying the joint ratings. This paper introduces a smoothed version of kappa computed after raking the table to achieve pre-specified marginal distributions. A comparison of kappa with raked kappa for various margins can indicate the extent of the dependence on the margins, and can indicate how much of the lack of agreement is due to marginal heterogeneity. 相似文献
72.
Localization of eukaryotic initiation factor 2 in neuron primary cultures and established cell lines
Maria V. T. Lobo F. Javier M. Alonso Susana Rodriguez Alberto Alcazar Elena Martin Francisco Munoz Rafael G-Santander Matilde Salinas Juan L. Fando 《The Histochemical journal》1997,29(6):453-468
Eukaryotic initiation factor 2 (eIF-2) is a heterotrimeric protein with subunits α, β and γ that forms a ternary complex with
Met-tRNA and GTP. It promotes the binding of Met-tRNA to ribosomes and controls translational rates via phosphorylation/dephosphorylation
mechanisms. By means of immunofluorescence and post-embedding immunocytochemistry of intact cells and quantitative immunoblotting
of cell extracts, the cellular distribution of the initiation factor has been examined in primary neuronal cultures as well
as in two established cell lines: PC12 phaeochromocytoma cells and rat pituitary GH4C1 cells. Our results indicated that the
initiation factor is located not only in the cytoplasm but also in the nuclei of the cultured neurons and cell lines. In the
cytoplasm, immunocytochemical studies reveal that the factor is present mainly in those areas that are rich in ribosomes.
In the nucleus, the immunolabelling of eukaryotic initiation factor 2 verified the presence of gold particles in both nucleolar
and extranucleolar areas. The specific distribution of this factor on both sides of the nuclear envelope suggests that it
might have some nuclear-related function(s) besides its already known role in the control of translation 相似文献
73.
74.
Phytoplankton and zooplankton response to ultraviolet radiation in a high-altitude Andean lake: short- versus long-term effects 总被引:8,自引:0,他引:8
Cabrera Sergio; Lopez Matilde; Tartarotti Barbara 《Journal of plankton research》1997,19(11):1565-1582
Exclusion experiments on global UV (A and B) radiation and globalUVB were performed in 460 I mesocosms with plankton communitiesfrom the oligotrophic Andean lake Laguna Negra (33°35'S70°04'W;2700 m a.s.l.). The experiments were run for 30 days duringthe summers of 19911992 and 19921993, and for48 days in 19931994. When UVB radiation was allowed toenter into the mesocosms (full sun), the population of Ankyrajudayi (Chlorophyta) reached the highest density, suggestingthat this species can endure high levels of UV radiation. Concurrently,an increase in chlorophyll a concentration was observed in thistreatment. The cladoceran Chydorus sphaericus and the rotiferLepadella ovallts were strongly inhibited by UVB. Conversely,UVB radiation had no effect on the survival of the differentlife stages of the calanoid copepod Boeckela gractlipes, suggestinga species-specific difference in the sensitivity to solar UVBradiation. Moreover, no reduction in the number of copepod eggsper female and the number of nauplii produced was observed.Apparently, herbivory does not strongly affect phytoplanktonabundance. Moreover, the phytoplankton species composition changedin the different treatments over the time. Fragilaria construensand Fragilaria crotonensis were dominant in those mesocosmswhere UVB was excluded. Populations fluc tuated depending ontheir life cycles and the period of time they were exposed toUVB radiation. It is important to define the time scale of exclusionexperiments, because different conclusions about the influenceof UVB irradiance result from short-, medium- or long-term exposures. 相似文献
75.
Romain Bourcier Solena Le Scouarnec Stéphanie Bonnaud Matilde Karakachoff Emmanuelle Bourcereau Sandrine Heurtebise-Chrétien Céline Menguy Christian Dina Floriane Simonet Alexis Moles Cédric Lenoble Pierre Lindenbaum Stéphanie Chatel Bertrand Isidor Emmanuelle Génin Jean-François Deleuze Jean-Jacques Schott Hervé Le Marec 《American journal of human genetics》2018,102(1):133-141
76.
Corcelli A Lobasso S Palese LL Saponetti MS Papa S 《Biochemical and biophysical research communications》2007,354(3):795-801
Membranes having an a high content of cardiolipin were isolated from an extremely halophilic archaeon Halorubrum sp. Absorbance difference spectra of detergent-solubilized plasma membranes reduced by dithionite suggested the presence of b-type cytochromes. Non-denaturing gel electrophoresis revealed only one fraction having TMPD-oxidase activity in which cardiolipin was the major lipid component. The electroeluted fraction showed a cytochrome c oxidase activity characterized by the reduced minus oxidized difference spectra as a terminal heme-copper oxidase. The cytochrome c oxidase activity of the archaeal cardiolipin-rich membranes was inhibited by the cardiolipin-specific fluorescent marker 10-N-nonyl acridine orange (NAO) in a dose-dependent manner. The results indicate that an archaeal analogue of cardiolipin is tightly associated to archaeal terminal oxidases and is required for its optimal functioning. 相似文献
77.
Involvement of a maize proline-rich protein in secondary cell wall formation as deduced from its specific mRNA localization 总被引:3,自引:0,他引:3
Vignols Florence José-estanyol Matilde Caparrós-ruiz David Rigau Joan Puigdomènech Pere 《Plant molecular biology》1999,39(5):945-952
A clone encoding a proline-rich protein (ZmPRP) has been obtained from maize root by differential screening of a maturing elongation root cDNA library. The amino acid sequence deduced from the full-length cDNA contains a putative signal peptide and a highly repetitive sequence containing the PEPK motif, indicating that the ZmPRP mRNA may code for a cell wall protein. The PEPK repeat is also found in a previously reported wheat sequence but differs from the repeated sequences found in hydroxyproline-rich glycoproteins (HRGP) and in dicot proline-rich proteins (PRP). In the maize genome, the ZmPRP protein is encoded by a single gene that is expressed in maturing regions of the root, in the hypocotyl and in the pericarp. In these organs, the ZmPRP mRNA accumulates in the xylem and surrounding cells, and in the epidermis. No ZmPRP mRNA was found in the phloem. The pattern of mRNA accumulation is very similar to the one observed for genes coding for proteins involved in lignin biosynthesis and, like most cell wall proteins, ZmPRP synthesis is also induced by wounding. These data support the hypothesis that ZmPRP is a member of a new class of fibrous proteins involved in the secondary cell wall formation in monocot species. 相似文献
78.
Reference values for TSH may be inadequate to define hypothyroidism in persons with morbid obesity: Di@bet.es study 下载免费PDF全文
Sergio Valdés Cristina Maldonado‐Araque Ana Lago‐Sampedro Juan Antonio Lillo‐Muñoz Eduardo Garcia‐Fuentes Vidal Perez‐Valero Carolina Gutiérrez‐Repiso Eva Garcia‐Escobar Albert Goday Inés Urrutia Laura Peláez Alfonso Calle‐Pascual Elena Bordiú Luis Castaño Conxa Castell Elias Delgado Edelmiro Menéndez Josep Franch‐Nadal Sonia Gaztambide Joan Girbés Emilio Ortega Joan Vendrell Matilde R. Chacón F. Javier Chaves Federico Soriguer Gemma Rojo‐Martínez 《Obesity (Silver Spring, Md.)》2017,25(4):788-793
79.
Lobasso S Saponetti MS Polidoro F Lopalco P Urbanija J Kralj-Iglic V Corcelli A 《Chemistry and physics of lipids》2009,157(1):12-20
The dye 10-N-nonyl acridine orange (NAO) is used to label cardiolipin domains in mitochondria and bacteria. The present work represents the first study on the binding of NAO with archaebacterial lipid membranes. By combining absorption and fluorescence spectroscopy with fluorescence microscopy studies, we investigated the interaction of the dye with (a) authentic standards of archaebacterial cardiolipins, phospholipids and sulfoglycolipids; (b) isolated membranes; (c) living cells of a square-shaped extremely halophilic archaeon. Absorption and fluorescence spectroscopy data indicate that the interaction of NAO with archaebacterial cardiolipin analogues is similar to that occurring with diacidic phospholipids and sulfoglycolipids, suggesting as molecular determinants for NAO binding to archaebacterial lipids the presence of two acidic residues or a combination of acidic and carbohydrate residues. In agreement with absorption spectroscopy data, fluorescence data indicate that NAO fluorescence in archaeal membranes cannot be exclusively attributed to bisphosphatidylglycerol and, therefore, different from mitochondria and bacteria, the dye cannot be used as a cardiolipin specific probe in archaeal microorganisms. 相似文献
80.
Accounting for morphological plasticity in phytoplankton populations is relevant for taxonomy, systematic/evolutionary, and
ecological studies. In this work, the green alga Pediastrum tetras (Ehrenberg) Ralfs was used to describe the variation in population size structure over its growth cycle and to analyze responses
to changes in biotic and abiotic factors. Pediastrum cultures reached a final stable concentration in approximately 10 days. This density (8 × 105 cells ml−1) remained stable for at least another 13 days and the intrinsic growth rate was 0.24 ± 0.01 day−1. In the exponential phase, the relative number of single cells and the proportion of large cells (with vesicles inside) within
colonies increased. When density peaked, a relative increase of single cells as well as small cells in new colonies took place.
Finally, during the stationary phase, the trend reversed: fewer single cells and a larger cell size (without vesicles) were
observed. Results indicated that nutrient supply could affect population structure, diminishing the proportion of eight-cell
colonies. Daphnia
magna Straus significantly reduced the Pediastrum population density due to predation, and this led to a significant decrease in the density of the largest colonies. In addition,
info-chemicals induced a slight increase in the density of the largest colonies compared to the control treatment. Our study
suggests a possible trade-off in P. tetras colonial size in natural environments: during the stationary growth period in a lake, Pediastrum populations tend to increase in size for efficient use of nutrients, while they decrease in size in the presence of herbivores.
Handling editor: J. Padisak 相似文献