全文获取类型
收费全文 | 51300篇 |
免费 | 17172篇 |
国内免费 | 2554篇 |
出版年
2024年 | 46篇 |
2023年 | 363篇 |
2022年 | 935篇 |
2021年 | 1747篇 |
2020年 | 3087篇 |
2019年 | 4763篇 |
2018年 | 4843篇 |
2017年 | 4864篇 |
2016年 | 5157篇 |
2015年 | 5535篇 |
2014年 | 5545篇 |
2013年 | 5972篇 |
2012年 | 4054篇 |
2011年 | 3531篇 |
2010年 | 4316篇 |
2009年 | 2972篇 |
2008年 | 1980篇 |
2007年 | 1484篇 |
2006年 | 1352篇 |
2005年 | 1310篇 |
2004年 | 1100篇 |
2003年 | 983篇 |
2002年 | 841篇 |
2001年 | 710篇 |
2000年 | 615篇 |
1999年 | 500篇 |
1998年 | 242篇 |
1997年 | 201篇 |
1996年 | 224篇 |
1995年 | 183篇 |
1994年 | 207篇 |
1993年 | 124篇 |
1992年 | 172篇 |
1991年 | 161篇 |
1990年 | 112篇 |
1989年 | 116篇 |
1988年 | 88篇 |
1987年 | 97篇 |
1986年 | 79篇 |
1985年 | 53篇 |
1984年 | 64篇 |
1983年 | 41篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1979年 | 19篇 |
1978年 | 16篇 |
1975年 | 15篇 |
1973年 | 16篇 |
1972年 | 14篇 |
1970年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
da Silva Gessiane Pereira de Melo Josi Teixeira Monteiro Frederico Ozanan Barros Ferreira Ana Karolyna Pereira Carneiro Liliane Almeida Takeshita Rafaela S. C. 《International journal of primatology》2021,42(5):722-736
International Journal of Primatology - The hormone dehydroepiandrosterone (DHEA) and its sulfate ester (DHEAS) are the most abundant circulating steroids in human and some nonhuman primates, and... 相似文献
992.
Lei Lei Yang Luomiao Cui Bowen Liu HuaLong Wang Jingguo Zheng Hongliang Xin Wei Zou Detang 《Plant Growth Regulation》2021,95(1):97-110
Plant Growth Regulation - β-ketoacyl-CoA synthase is a key enzyme in the biosynthesis of over-long-chain fattty acids; thus, it plays a crucial role in plant resistance to stress. Herein, 33... 相似文献
993.
994.
Liu Wen-Shen Zheng Hong-Xiang Liu Chang Guo Mei-Na Zhu Shi-Chen Cao Yue Qiu Rong-Liang Morel Jean Louis van der Ent Antony Tang Ye-Tao 《Plant and Soil》2021,461(1-2):565-578
Plant and Soil - Dicranopteris linearis is a rare earth element (REE), aluminium (Al) and silicon (Si) hyperaccumulator plant which occurs in southern China. To date, there have been no studies on... 相似文献
995.
Li‐Hsuan Ho Yung‐I Lee Shu‐Ying Hsieh I‐Shiuan Lin Yun‐Chien Wu Han‐Yu Ko Patrick A. Klemens H. Ekkehard Neuhaus Yi‐Min Chen Tzu‐Pi Huang Chih‐Hsin Yeh Woei‐Jiun Guo 《Plant, cell & environment》2021,44(1):20-33
Gastrodia elata, a fully mycoheterotrophic orchid without photosynthetic ability, only grows symbiotically with the fungus Armillaria. The mechanism of carbon distribution in this mycoheterotrophy is unknown. We detected high sucrose concentrations in all stages of Gastrodia tubers, suggesting sucrose may be the major sugar transported between fungus and orchid. Thick symplasm‐isolated wall interfaces in colonized and adjacent large cells implied involvement of sucrose importers. Two sucrose transporter (SUT)‐like genes, GeSUT4 and GeSUT3, were identified that were highly expressed in young Armillaria‐colonized tubers. Yeast complementation and isotope tracer experiments confirmed that GeSUT4 functioned as a high‐affinity sucrose‐specific proton‐dependent importer. Plasma‐membrane/tonoplast localization of GeSUT4‐GFP fusions and high RNA expression of GeSUT4 in symbiotic and large cells indicated that GeSUT4 likely functions in active sucrose transport for intercellular allocation and intracellular homeostasis. Transgenic Arabidopsis overexpressing GeSUT4 had larger leaves but were sensitive to excess sucrose and roots were colonized with fewer mutualistic Bacillus, supporting the role of GeSUT4 in regulating sugar allocation. This is not only the first documented carbon import system in a mycoheterotrophic interaction but also highlights the evolutionary importance of sucrose transporters for regulation of carbon flow in all types of plant‐microbe interactions. 相似文献
996.
997.
998.
999.
Juliano Silva Lima Igor David da Costa Ilana Rosental Zalmon 《Zeitschrift fur angewandte Ichthyologie》2021,37(2):337-341
The present work provides length-weight relationships (LWRs) for fish species captured around artificial offshore reef deployed 5 km from Guaxindiba Port, northern Rio de Janeiro, Brazil. The fish were captured during two sampling periods each year between 1996 and 2017 using bottom gill nets (25 mlength × 3 mdepth; 30 mm mesh). The fish were kept on ice and the biometric data, including total length (cm) and total wet weight (g) were determined in the laboratory. A total of 16 species belonging to 10 families were analyzed with Sciaenidae being the species richest family (5 spp) in the samples. The new value of LWRs for Sphyraena guachancho and new maximum sizes recorded for seven species highlight the scarcity of information on biological aspects of South America coastal fishes. These LWRs should assist fisheries scientist and managers to complement their further studies of population parameters to improve management decisions. 相似文献
1000.
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