全文获取类型
收费全文 | 1615篇 |
免费 | 120篇 |
国内免费 | 2篇 |
专业分类
1737篇 |
出版年
2023年 | 7篇 |
2022年 | 26篇 |
2021年 | 29篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 42篇 |
2017年 | 36篇 |
2016年 | 51篇 |
2015年 | 82篇 |
2014年 | 88篇 |
2013年 | 113篇 |
2012年 | 124篇 |
2011年 | 111篇 |
2010年 | 84篇 |
2009年 | 78篇 |
2008年 | 98篇 |
2007年 | 103篇 |
2006年 | 102篇 |
2005年 | 82篇 |
2004年 | 76篇 |
2003年 | 63篇 |
2002年 | 59篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1998年 | 20篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 13篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1968年 | 2篇 |
排序方式: 共有1737条查询结果,搜索用时 15 毫秒
31.
Margarita Fernández García de Castro Carlos J. Martinez-Honduvilla 《Physiologia plantarum》1984,62(4):581-588
The decline of germination observed after storage of Pinus pinea L. seeds up to 35 years at room temperature was accompanied by an increase in their ability to leak reducing sugars, probably as a consequence of membrane alterations due to senescence. Results of studies of the cell ultrastructure of viable and non-viable seeds before and after imbibition indicate that such is the case. Noticeable changes occurred in the ultrastructure of endosperm and embryo cells with germinability loss, even in the unimbibed condition. The main alterations were spherosome coalescence, plasmalemma separation from the cell wall and chromatin aggregation. 相似文献
32.
Jaime Carrasco Carlos García-Delgado Rebeca Lavega María L. Tello María De Toro Víctor Barba-Vicente María S. Rodríguez-Cruz María J. Sánchez-Martín Margarita Pérez Gail M. Preston 《Microbial biotechnology》2020,13(6):1933-1947
Microorganisms strongly influence and are required to generate the selective substrate that provides nutrients and support for fungal growth, and ultimately to induce mushroom fructification under controlled environmental conditions. In this work, the fungal and bacterial microbiota living in the different substrates employed in a commercial crop (compost phase I, II and III, flush 1 and 2, and casing material on day 1, 6 and 8 after compost casing and during flush 1 and 2) have been characterized along the different stages of cultivation by metataxonomic analysis (16S rRNA and ITS2), analysis of phospholipid fatty acid content (PLFAs) and RT-qPCR. Additionally, laccase activity and the content of lignin and complex carbohydrates in compost and casing have been quantified. The bacterial diversity in compost and casing increased throughout the crop cycle boosted by the connection of both substrates. As reflected by the PLFAs, the total living bacterial biomass appears to be negatively correlated with the mycelium of the crop. Agaricus bisporus was the dominant fungal species in colonized substrates, displacing the pre-eminent Ascomycota, accompanied by a sustained increase in laccase activity, which is considered to be a major product of protein synthesis during the mycelial growth of champignon. From phase II onwards, the metabolic machinery of the fungal crop degrades lignin and carbohydrates in compost, while these components are hardly degraded in casing, which reflects the minor role of the casing for nourishing the crop. The techniques employed in this study provide a holistic and detailed characterization of the changing microbial composition in commercial champignon substrates. The knowledge generated will contribute to improve compost formulations (selection of base materials) and accelerate compost production, for instance, through biotechnological interventions in the form of tailored biostimulants and to design environmentally sustainable bio-based casing materials. 相似文献
33.
Imbalance between the main intracellular degradative, trafficking and intercellular shuttling pathways has been implicated in disease pathogenesis. Autophagy controls degradation of cellular components, while vesicular trafficking permits transport of material in and out of the cell. Emerging evidence has uncovered the extensive interconnectivity between these pathways, which is crucial to maintain organismal homeostasis. Thus, therapeutic intervention and drug development strategies targeting these processes, particularly in neurodegeneration, should account for this broad crosstalk, to maximize effectiveness. Here, recent findings underlining the highly dynamic nature of the crosstalk between autophagy, endosomal transport, and secretion is reviewed. Synergy of autophagy and endosomes for degradation, as well as, competition of autophagy and secretion are discussed. Perturbation of this crosstalk triggers pathology especially neurodegeneration. 相似文献
34.
35.
Margarita Pérez-Jiménez M. Belén López-Soto José Cos-Terrer 《In vitro cellular & developmental biology. Plant》2013,49(1):79-84
We describe an efficient protocol for callus induction from adult tissues of Prunus persica (L.) Batsch. Three different commercial peach genotypes, Early May®, Zise May®, and UFO-3®, plus three other genotypes from hybrid crosses performed in February 2006, PS108, PS208, and PS708, were used in the study. Thirteen explant treatments were tested using nine different plant parts. Murashige and Skoog and woody plant medium salts were assayed with several concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), kinetin (KN), and thidiazuron, and two different photoperiods were tested, a 16-h photoperiod or continuous darkness. In terms of the quantitative response, two parameters were assessed: the number of d to callus induction and relative callus growth recorded after 30 d. Woody plant medium supplemented with 2,4-D and KN significantly increased the rates of callus induction in the majority of treatments. And no significant differences among the P. persica genotypes were found. The explants derived from stem and calyx produced up to 85 and 96% callus induction, respectively. The protocol described here could be used for efficient callus induction in a range of Prunus spp. 相似文献
36.
Jean M. J. Tronchet Imre Kovács Françoise Barbalat-Rey Margarita VegaHolm 《Nucleosides, nucleotides & nucleic acids》2013,32(6):1115-1123
Abstract Reaction of 2′,5′-di-O-TBDMS-3′-ketouridine 1 with L-cysteine yielded in good yield a resolvable mixture of the two expected epimeric spironucleosides 2 and 3. Amidification of their carboxylic group took place readily and the ribo carboxamide 4 was oxidized to the corresponding sulfoxide 6. Despite their similarity to TSAO derivatives these compounds did not exhibit usable anti-HIV activity. 相似文献
37.
38.
M. Teresa Telleria Ireneia Melo Margarita Dueñas Isabel Salcedo Esperanza Beltrán-Tejera J. Laura Rodríguez-Armas María P. Martín 《Mycological Progress》2013,12(4):687-692
Using morphological and molecular data, the new species Sistotremastrum guttuliferum is described from specimens collected in the Azores archipelago, Madeira and Canary Islands. Morphologically, this new species differs from S. niveocremeum and S. suecicum by the small oil drops in the cytoplasm of subicular hyphae and the spore size. An updated key of Sistotremastrum species is provided. 相似文献
39.
The problem of plasmon resonance in spherical metal nanoparticles incorporated into an anisotropic dielectric medium is studied theoretically. Analytic solution is obtained in long-wavelength approximation for the case of weak uniaxial anisotropy. It is shown that medium anisotropy causes shifts of plasmon frequency from its position in an isotropic medium, which are different for plasmons with dipole momenta parallel and perpendicular to the axis of the medium. For the parallel and perpendicular orientations, which are determined by polarization of incident light, plasmon shifts differ by a factor of 4/3. Analytic expressions for field enhancement in the vicinity of a metal nanoparticle is obtained and analyzed for the cases of noble metals. The perspectives of experimental check of the obtained results and possible applications of plasmon anisotropy in plasmonics and sensorics are discussed. 相似文献
40.