全文获取类型
收费全文 | 2703篇 |
免费 | 234篇 |
专业分类
2937篇 |
出版年
2023年 | 10篇 |
2022年 | 27篇 |
2021年 | 40篇 |
2020年 | 22篇 |
2019年 | 31篇 |
2018年 | 43篇 |
2017年 | 36篇 |
2016年 | 66篇 |
2015年 | 96篇 |
2014年 | 142篇 |
2013年 | 130篇 |
2012年 | 159篇 |
2011年 | 196篇 |
2010年 | 137篇 |
2009年 | 112篇 |
2008年 | 138篇 |
2007年 | 141篇 |
2006年 | 149篇 |
2005年 | 103篇 |
2004年 | 141篇 |
2003年 | 127篇 |
2002年 | 125篇 |
2001年 | 56篇 |
2000年 | 55篇 |
1999年 | 50篇 |
1998年 | 40篇 |
1997年 | 32篇 |
1996年 | 33篇 |
1995年 | 15篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 37篇 |
1991年 | 26篇 |
1990年 | 32篇 |
1989年 | 30篇 |
1988年 | 25篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 21篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 24篇 |
1978年 | 20篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1974年 | 6篇 |
1972年 | 11篇 |
排序方式: 共有2937条查询结果,搜索用时 15 毫秒
51.
Bertrand P. Beauvoit Sophie Colombié Antoine Monier Marie-Hélène Andrieu Benoit Biais Camille Bénard Catherine Chéniclet Martine Dieuaide-Noubhani Christine Nazaret Jean-Pierre Mazat Yves Gibon 《The Plant cell》2014,26(8):3224-3242
A kinetic model combining enzyme activity measurements and subcellular compartmentation was parameterized to fit the sucrose, hexose, and glucose-6-P contents of pericarp throughout tomato (Solanum lycopersicum) fruit development. The model was further validated using independent data obtained from domesticated and wild tomato species and on transgenic lines. A hierarchical clustering analysis of the calculated fluxes and enzyme capacities together revealed stage-dependent features. Cell division was characterized by a high sucrolytic activity of the vacuole, whereas sucrose cleavage during expansion was sustained by both sucrose synthase and neutral invertase, associated with minimal futile cycling. Most importantly, a tight correlation between flux rate and enzyme capacity was found for fructokinase and PPi-dependent phosphofructokinase during cell division and for sucrose synthase, UDP-glucopyrophosphorylase, and phosphoglucomutase during expansion, thus suggesting an adaptation of enzyme abundance to metabolic needs. In contrast, for most enzymes, flux rates varied irrespectively of enzyme capacities, and most enzymes functioned at <5% of their maximal catalytic capacity. One of the major findings with the model was the high accumulation of soluble sugars within the vacuole together with organic acids, thus enabling the osmotic-driven vacuole expansion that was found during cell division. 相似文献
52.
Zoffmann S Bertrand S Do QT Bertrand D Rognan D Hibert M Galzi JL 《Journal of neurochemistry》2007,101(2):506-516
Neurokinin A stimulates physiological responses in the peripheral and central nervous systems upon interacting primarily with the tachykinin NK2 receptor (NK2R). In this study, the structure of NKA bound to the NK2R is characterised by use of fluorescence resonance energy transfer. Four fluorescent NKA analogues with Texas red introduced at amino acid positions 1, 4, 7 and 10 were prepared. When bound to a NK2R carrying enhanced green fluorescent protein at the N-terminus, all peptides reduce green fluorescent protein fluorescence from 10% to 50% due to energy transfer. The derived donor-acceptor distances are 46, 55, 59 and 69 A for the fluorophore linked to positions 1-10, respectively. The monotonic increase in distance clearly indicates that the peptide adopts an extended structure when bound to its receptor. The present data are used, in combination with rhodopsin structure, fluorescence studies, photoaffinity labelling and site-directed mutagenesis data to design a computer model of the NKA-NK2R complex. We propose that the N-terminus of NKA is exposed and accessible to the extracellular medium. Subsequent amino acids of the NKA peptide become progressively more buried residues up to approximately one-third of the transmembrane-spanning domain. 相似文献
53.
Pascale Varlet Fabrice Chretien Felipe Andreiuolo Mélanie Pages Ali Ibrahim Johan Pallud Edouard Dezamis Georges Abi‐Lahoud François Nataf Baris Turak Bertrand Devaux Darine Abi‐Haidar 《Journal of biophotonics》2017,10(2):253-263
Meningioma is the most frequent primary central nervous system tumor. The risk of recurrence and the prognosis are correlated with the extent of the resection that ideally encompasses the infiltrated dura mater and, if required, the infiltrated bone. No device can deliver real‐time intraoperative histopathological information on the tumor environment to help the neurosurgeon to achieve a gross total removal. This study assessed the abilities of nonlinear microscopy to provide relevant and real‐time data to help resection of meningiomas. Nine human meningioma samples (four World Health Organization Grade I, five Grade II) were analyzed using different optical modalities: spectral analysis and imaging, lifetime measurements, fluorescence lifetime imaging microscopy, fluorescence emitted under one‐ and two‐photon excitation and the second‐harmonic generation signal imaging using a multimodal setup. Nonlinear microscopy produced images close to histopathology as a gold standard. The second‐harmonic generation signal delineated the collagen background and two‐photon fluorescence underlined cell cytoplasm. The matching between fluorescence images and Hematoxylin and Eosin staining was possible in all cases. Grade I meningioma emitted less autofluorescence than Grade II meningioma and Grade II meningioma exhibited a distinct lifetime value. Autofluorescence was correlated with the proliferation rates and seemed to explain the observed differences between Grade I and II meningiomas. This preliminary multimodal study focused on human meningioma samples confirms the potential of tissue autofluorescence analysis and nonlinear microscopy in helping intraoperatively neurosurgeons to reach the actual boundaries of the tumor infiltration.
54.
55.
56.
E Perez-Reyes A Castellano H S Kim P Bertrand E Baggstrom A E Lacerda X Y Wei L Birnbaumer 《The Journal of biological chemistry》1992,267(3):1792-1797
The skeletal muscle dihydropyridine receptor/Ca2+ channel is composed of five protein components (alpha 1, alpha 2 delta, beta, and gamma). Only two such components, alpha 1 and alpha 2, have been identified in heart. The present study reports the cloning and expression of a novel beta gene that is expressed in heart, lung, and brain. Coexpression of this beta with a cardiac alpha 1 in Xenopus oocytes causes the following changes in Ca2+ channel activity: it increases peak currents, accelerates activation kinetics, and shifts the current-voltage relationship toward more hyperpolarized potentials. It also increases dihydropyridine binding to alpha 1 in COS cells. These results indicate that the cardiac L-type Ca2+ channel has a similar subunit structure as in skeletal muscle, and provides evidence for the modulatory role of the beta subunit. 相似文献
57.
Samuel Rommelaere Virginie Millet Thien-Phong Vu Manh Thomas Gensollen Pierre Andreoletti Mustapha Cherkaoui-Malki Christophe Bourges Bertrand Escalière Xin Du Yu Xia Jean Imbert Bruce Beutler Yoshiakira Kanai Bernard Malissen Marie Malissen Anne Tailleux Bart Staels Franck Galland Philippe Naquet 《PloS one》2014,9(8)
58.
Eric Giraud Alain Brauman Simon Keleke Bertrand Lelong Maurice Raimbault 《Applied microbiology and biotechnology》1991,36(3):379-383
Summary An amylolytic lactic acid bacterium identified as Lactobacillus plantarum was isolated from cassava roots (Manihot esculenta var. Ngansa) during reting. The amylolytic enzyme synthesized was an extracellular -amylase with an optimum pH of 5.0 and an optimum temperature of 55° C. Cultured on starch, the strain displayed a growth rate of 0.43 h–1, a biomass yield of 0.19 g·g–1 and a lactate yield of 0.81 g·g–1. The growth kinetics were similar on starch and glucose. Sufficient enzyme was synthesized and starch hydrolysis was not a limiting factor for growth. Biosynthesis of the enzyme was observed when the glucose concentration was less than 6.7 g·l–1 and reached up to 4 IU·ml–1 at the end of the fermentation.
Offprint requests to: M. Raimbault 相似文献
59.
Anne-Sophie Mathieu Stanley Lutts Bertrand Vandoorne Christophe Descamps Claire Périlleux Vincent Dielen Jean-Claude Van Herck Muriel Quinet 《Journal of plant physiology》2014
An increase in mean and extreme summer temperatures is expected as a consequence of climate changes and this might have an impact on plant development in numerous species. Root chicory (Cichorium intybus L.) is a major crop in northern Europe, and it is cultivated as a source of inulin. This polysaccharide is stored in the tap root during the first growing season when the plant grows as a leafy rosette, whereas bolting and flowering occur in the second year after winter vernalisation. The impact of heat stress on plant phenology, water status, photosynthesis-related parameters, and inulin content was studied in the field and under controlled phytotron conditions. In the field, plants of the Crescendo cultivar were cultivated under a closed plastic-panelled greenhouse to investigate heat-stress conditions, while the control plants were shielded with a similar, but open, structure. In the phytotrons, the Crescendo and Fredonia cultivars were exposed to high temperatures (35 °C day/28 °C night) and compared to control conditions (17 °C) over 10 weeks. In the field, heat reduced the root weight, the inulin content of the root and its degree of polymerisation in non-bolting plants. Flowering was observed in 12% of the heat stressed plants during the first growing season in the field. In the phytotron, the heat stress increased the total number of leaves per plant, but reduced the mean leaf area. Photosynthesis efficiency was increased in these plants, whereas osmotic potential was decreased. High temperature was also found to induced flowering of up to 50% of these plants, especially for the Fredonia cultivar. In conclusion, high temperatures induced a reduction in the growth of root chicory, although photosynthesis is not affected. Flowering was also induced, which indicates that high temperatures can partly substitute for the vernalisation requirement for the flowering of root chicory. 相似文献
60.
Kiessoun Konaté Jacques Fran?ois Mavoungou Alexis Nicaise Lepengué Ra?ssa RR Aworet-Samseny Adama Hilou Alain Souza Mamoudou H Dicko Bertrand M’Batchi 《Annals of clinical microbiology and antimicrobials》2012,11(1):1-12