全文获取类型
收费全文 | 5951篇 |
免费 | 395篇 |
国内免费 | 2篇 |
出版年
2023年 | 36篇 |
2022年 | 68篇 |
2021年 | 183篇 |
2020年 | 129篇 |
2019年 | 142篇 |
2018年 | 178篇 |
2017年 | 170篇 |
2016年 | 251篇 |
2015年 | 319篇 |
2014年 | 341篇 |
2013年 | 454篇 |
2012年 | 506篇 |
2011年 | 475篇 |
2010年 | 289篇 |
2009年 | 264篇 |
2008年 | 344篇 |
2007年 | 340篇 |
2006年 | 276篇 |
2005年 | 259篇 |
2004年 | 209篇 |
2003年 | 224篇 |
2002年 | 200篇 |
2001年 | 76篇 |
2000年 | 55篇 |
1999年 | 60篇 |
1998年 | 49篇 |
1997年 | 31篇 |
1996年 | 35篇 |
1995年 | 31篇 |
1994年 | 30篇 |
1993年 | 33篇 |
1992年 | 30篇 |
1991年 | 25篇 |
1990年 | 27篇 |
1989年 | 21篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 23篇 |
1984年 | 10篇 |
1983年 | 19篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 7篇 |
排序方式: 共有6348条查询结果,搜索用时 437 毫秒
91.
Geovanna Carla Zacheo Coelho Raphael da Silva Costa Fábio Porto-Foresti Rosicleire Verissimo-Silveira Alexandre Ninhaus-Silveira 《Zeitschrift fur angewandte Ichthyologie》2021,37(3):449-461
Ontogenetic studies of the eggs and larvae of fish can provide information on the initial life history and biology of a species, are important for taxonomic and evolutionary studies, and for cultivation in captivity. The aim of this study was to analyze and describe the main morphological differences in the larval ontogeny of Pseudoplatystoma reticulatum, Leiarius marmoratus, and its hybrid (♀ P. reticulatum × ♂ L. marmoratus), as well as to identify characteristics that can identify the species and their hybrid at the larvae and juvenile stages. 205 L. marmoratus, 210 P. reticulatum, and 205 hybrid specimens were analyzed, all of which were obtained through induced reproduction. Analyses were performed from hatching to 30 days post-hatching. 19 morphometric and 5 meristic characteristics were evaluated, in addition to chromatophore shape and distribution. The specimens were classified into two life periods: Larval (stages: yolk sac, pre-flexion, flexion, and post-flexion) and Juvenile. Newly hatched larvae were transparent, poorly developed, and had a scarcity of chromatophores. During the early stages of larval development, the three groups showed similarities in appearance and proportional dimensions. However, at both the end of the post-flexion stage and at the juvenile period when individuals were approximately 2 cm long, it was possible to differentiate between hybrids and their parental species by their morphometric, meristic, and pigment characteristics. The hybrid, despite occupying an intermediate position in relationship to its parents, exhibited a shape and size more similar to P. reticulatum, its maternal parent. 相似文献
92.
dos Santos Fernanda Marcelia Pflüger Pricila Fernandes Lazzarotto Leticia Uczay Mariana de Aguida Wesley Roberto da Silva Lisiane Santos Boaretto Fernanda Brião Menezes de Sousa Jayne Torres Picada Jaqueline Nascimento da Silva Torres Iraci Lucena Pereira Patrícia 《Neurochemical research》2021,46(8):2066-2078
Neurochemical Research - Gamma-decanolactone (GD) has been shown to reduce epileptic behavior in different models, inflammatory decreasing, oxidative stress, and genotoxic parameters. This study... 相似文献
93.
da Silva Fernando Henrique Alves de Morais Patrícia Lígia Dantas da Silva Dias Nildo de Sousa Nunes Glauber Henrique de Morais Marciana Bizerra Melo Marlenildo Ferreira de Albuquerque Nascimento Maria Tereza 《Journal of Plant Growth Regulation》2021,40(3):1298-1314
Journal of Plant Growth Regulation - This study evaluated the effect of saline water irrigation (4.5 dS m−1) on growth, gas exchange and mineral nutrient content in eight melon accessions and... 相似文献
94.
de Sousa Sylvia Morais de Oliveira Christiane Abreu Andrade Daniele Luiz de Carvalho Chainheny Gomes Ribeiro Vitória Palhares Pastina Maria Marta Marriel Ivanildo Evódio de Paula Lana Ubiraci Gomes Gomes Eliane Aparecida 《Journal of Plant Growth Regulation》2021,40(2):867-877
Journal of Plant Growth Regulation - The rising demand for agricultural commodities in developing countries has put increasing pressure on land resources for higher yields, with associated growth... 相似文献
95.
96.
de Sousa Karolini Tenffen Deniz Matheus Moro Matheus Fernando Gomes Isabelle Cordova do Vale Marcos Martinez Dittrich João Ricardo 《International journal of biometeorology》2021,65(10):1781-1786
International Journal of Biometeorology - Lying behavior is an important indicator of the cows’ welfare and health. In this study, we evaluate the effect of the physical environment on dairy... 相似文献
97.
Olívia Moraes Ruberti Andressa Silva Sousa Laís Rosa Viana Moiss Felipe Pereira Gomes Alessandra Medeiros Maria Cristina Cintra Gomes Marcondes Luciano de Figueiredo Borges Carlos Cesar Crestani Cristiano Mostarda Telma Ftima da Cunha Moraes Rafael Renatino Canevarolo Maria Andreia Delbin Bruno Rodrigues 《Journal of cellular physiology》2021,236(2):1105-1115
This study aimed to evaluate the impact of aerobic training (AT) on autonomic, cardiometabolic, ubiquitin‐proteasome activity, and inflammatory changes evoked by myocardial infarction (MI) in ovariectomized rats. Female Wistar rats were ovariectomized and divided into four groups: sedentary + sham (SS), sedentary + MI (SI), AT + sham surgery (TS), AT + MI (TI). AT was performed on a treadmill for 8 weeks before MI. Infarcted rats previously subjected to AT presented improved physical capacity, increased interleukin‐10, and decreased pro‐inflammatory cytokines. Metabolomic analysis identified and quantified 62 metabolites, 9 were considered significant by the Vip Score. SS, SI, and TS groups presented distinct metabolic profiles; however, TI could not be distinguished from the SS group. MI dramatically increased levels of dimethylamine, and AT prevented this response. Our findings suggest that AT may be useful in preventing the negative changes in functional, inflammatory, and metabolic parameters related to MI in ovariectomized rats. 相似文献
98.
Carla Kruk Claudia Piccini Melina Devercelli Lucía Nogueira Victoria Accattatis Lía Sampognaro Angel M. Segura 《Oikos》2021,130(4):571-586
Understanding the mechanisms underlying community assembly helps to define success and susceptibility to biological invasions. Here, we explored phytoplankton community assembly following niche and neutral paradigms and using a trait-based approach. Under the hypothesis that the morphology-based functional groups (MBFG) clusters species with similar niche, we analysed how trait-related differences in fitness influence dominance of an invasive species. This was based on literature review, field data and model simulations. We predict that invading species can be dominant if: 1) do not belong to the local MBFG but use unexploited areas of the niche, or 2) belong to the resident MBFG but exhibit a higher fitness due to a particular combination of traits. The invasive dinoflagellate Ceratium furcoides was used as the model species to evaluate these hypotheses, its morphological (e.g. volume) and physiological (e.g. growth rates) traits were compared with species from the same (V: photosynthetic flagellates) and different (VII: colonial cyanobacteria) MBFG. Fitness was estimated using models parametrized with MBFG rates (R*, ability to draw down phosphate) under different environmental conditions (i.e. flushing). Results contributed to support both hypotheses. First, the alternation of C. furcoides and cyanobacteria dominance was explained by the use of different niches. Secondly, species from MBFG V were dominant under similar environments. Within this group V C. furcoides showed higher fitness under low flushing and high predation, advantage provided by a distinctive combination of traits. The application of trait-based approaches to represent the niche and estimate fitness along environmental gradients was useful to evaluate community assembly and can be used to predict the dominance of microbial species invasions. 相似文献
99.
Anne‐Laure Decombeix Thibault Durieux Carla J. Harper Rudolph Serbet Edith L. Taylor 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2021,54(1):96-105
The biology of trees that grew in high‐latitude forests during warmer geological periods is of major interest in understanding past and future ecosystem dynamics. As we study the different plants that composed these forests, it becomes possible to make comparisons with ecosystem processes that occur today. Here we describe a silicified late Permian (Lopingian) glossopterid (seed fern) trunk from Skaar Ridge, central Transantarctic Mountains, Antarctica, with evidence of glossopterid rootlets growing into its wood. The specimen is interpreted as a nurse log similar to those seen in some extant forests. Together with evidence of glossopterid roots growing within the lacunae of older roots, this new specimen suggests the existence of facilitative interactions among the glossopterid trees that dominated the high‐latitude forests of Gondwana during the late Permian. More generally, the existence of self‐facilitation might have favoured the expansion of glossopterids within various environments, especially those at high palaeolatitudes, during the Permian icehouse to greenhouse transition. 相似文献
100.
Liliane Bezerra de Lima Wliana Alves Viturino da Silva Ewelyn Cintya Felipe dos Santos Janaína Carla Barbosa Machado Thamara Figueiredo Procópio Maiara Celine de Moura Thiago Henrique Napoleão Magda Rhayanny Assunção Ferreira Luiz Alberto Lira Soares 《化学与生物多样性》2021,18(12):e2100538
The aim of this study was to evaluate the phytochemical composition, antioxidant, and antimicrobial potential of crude extract and fractions of Punica granatum leaves. The extract was produced by turbo extraction, after which hexanic, ethyl acetate, and aqueous fractions were obtained by partitioning. The chemical analyses were performed by thin layer chromatography and high-performance liquid chromatography, and the antioxidant activities were assayed by DPPH. and ABTS.+. Minimal inhibitory and bactericidal concentrations (MIC/MBC) were applied to twenty-two bacteria. Most strains susceptible to extract/fractions and resistant to antibiotics were selected, and ampicillin, azithromycin, ciprofloxacin, and gentamicin were associated with the ethyl acetate fraction (EAF) against multidrug-resistant strains in modulatory and checkboard models. The data from chromatographic analyses showed flavonoids and tannins in the extract, as well as the enrichment of EAF in phenols, mainly flavonoids. The flavonoids were connected to the electron transfer activity demonstrated in the DPPH. and ABTS.+ assays. Gram-positive strains are more susceptible to EAF. The subinhibitory concentrations of P. granatum enhanced the antimicrobial activity of the agents and reduced the EAF individual MIC, and the combination of EAF and antibiotics demonstrated a synergistic effect. These results present a promising approach for developing a therapy in which antioxidant extracts and fractions can be used in combination with antibiotics. 相似文献