全文获取类型
收费全文 | 39000篇 |
免费 | 3154篇 |
国内免费 | 4篇 |
出版年
2023年 | 224篇 |
2022年 | 206篇 |
2021年 | 441篇 |
2020年 | 442篇 |
2019年 | 464篇 |
2018年 | 724篇 |
2017年 | 640篇 |
2016年 | 1248篇 |
2015年 | 2040篇 |
2014年 | 2016篇 |
2013年 | 2770篇 |
2012年 | 3399篇 |
2011年 | 2888篇 |
2010年 | 1703篇 |
2009年 | 1414篇 |
2008年 | 2377篇 |
2007年 | 2291篇 |
2006年 | 2346篇 |
2005年 | 2073篇 |
2004年 | 2050篇 |
2003年 | 1942篇 |
2002年 | 1936篇 |
2001年 | 762篇 |
2000年 | 853篇 |
1999年 | 529篇 |
1998年 | 359篇 |
1997年 | 256篇 |
1996年 | 262篇 |
1995年 | 258篇 |
1994年 | 217篇 |
1993年 | 213篇 |
1992年 | 229篇 |
1991年 | 192篇 |
1990年 | 171篇 |
1989年 | 154篇 |
1988年 | 112篇 |
1987年 | 98篇 |
1986年 | 93篇 |
1985年 | 127篇 |
1984年 | 158篇 |
1983年 | 111篇 |
1982年 | 164篇 |
1981年 | 127篇 |
1980年 | 118篇 |
1979年 | 102篇 |
1978年 | 92篇 |
1977年 | 88篇 |
1976年 | 108篇 |
1975年 | 78篇 |
1973年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Magalhães André L. B. Daga Vanessa S. Bezerra Luis A. V. Vitule Jean R. S. Jacobi Claudia M. Silva Luiz G. M. 《Hydrobiologia》2020,847(18):3897-3915
Hydrobiologia - Non-native freshwater fish introduced via the aquarium trade can cause major changes at the community level over time and space, resulting in dynamics context dependencies within... 相似文献
972.
973.
Rubén Ortega-Álvarez Esteban Berrones Benítez Israel Medina Mena José Jaime Zúñiga-Vega 《Ibis》2020,162(4):1262-1278
The simultaneous effects of habitat traits and interspecific interactions determine the occurrence and habitat use of wildlife populations. However, little research has been devoted to examining spatial co-occurrence among closely related species while considering the effect of habitat variation and imperfect detectability of species in the field. In this study, we focused on migratory and resident 'wood-warblers' that coexist during the winter in a Neotropical working landscape in southern Mexico to understand if habitat occupancy of resident wood-warblers is influenced by habitat characteristics and by the presence of other species of resident and migratory wood-warblers. For this purpose, we implemented two-species occupancy models, which account for the imperfect detectability of these birds in the field. Our results revealed that habitat occupancy of resident wood-warblers was positively influenced by the presence of other closely related species (both migratory and resident). These positive relationships may be explained by the fact that different species of wood-warblers frequently participate in mixed-species flocks. However, these patterns of species co-occurrence were more evident among resident species than between migratory and resident species, which may be explained by micro-habitat segregation and differences in behaviours between resident and migratory wood-warblers. We also found that some habitat characteristics may mediate the observed patterns of species co-occurrence. Specifically, sites with larger trees were associated with the co-occurrence of some species of resident wood-warblers. In addition, we discuss the possibility that species co-occurrence might be the result of shared preferences for environmental factors that we did not consider. Our study highlights the importance of the interplay between species co-occurrence and habitat traits in determining the presence and habitat use of resident birds in Neotropical working landscapes. 相似文献
974.
Francielle C. Mosele Rafael Bissi Ricci Phablo Abreu José C. Rosa Neto 《Journal of cellular physiology》2020,235(9):6183-6193
Activation, proliferation, and differentiation of satellite cells can be influenced by extracellular factors, such as adiponectin. This adipokine has been proposed as a regulator of in vitro myogenesis, but its action on in vivo regeneration is not still elucidated. We used C57BL/6 (wild-type [WT]) and adiponectin knockout (AdKO) mice injured with barium chloride at periods of 3, 7, and 14 days after injury. The AdKO presented a higher number of centralized nuclei after 7 days, and a reduction in myogenic genes was observed after 3 days. Moreover, these mice presented an increase in anti-inflammatory cytokines after 3 and 7 days, and an increase in the M2 gene marker and proinflammatory cytokines after 7 days. The WT demonstrated an increase in adiponectin messenger RNA after 7 days. These results demonstrate that adiponectin is important in tissue remodeling during regeneration and that its deficiency does not compromise the maturation of muscle fibers, due to an increase in anti-inflammatory response; however, there is a possible impairment in proinflammatory response and an increase in centralized myonuclei. 相似文献
975.
This study provides sound evidence of the spawning activity of common dolphinfish (Coryphaena hippurus) in the Gulf of Cadiz (southwest Spain) during summer months. Along with waters off Côte d'Ivoire, this area adjacent to the Mediterranean Sea is the easternmost Atlantic spawning ground documented for the species. All the fish analysed (5 males and 15 females) were at spawning stage, except the smallest female (61.5 cm in fork length), which might not have yet reached sexual maturation. The oceanographic conditions during the samplings were similar to those occurring during the peak spawning season in the Gulf of Mexico. The study results are consistent with recent genetic studies indicating differentiation between Mediterranean and Atlantic dolphinfish populations, with the Strait of Gibraltar representing a boundary between two distinct reproductive units. The present results may contribute to improve the understanding of the dynamics of dolphinfish population and the management of eastern Atlantic and Mediterranean stocks. 相似文献
976.
Alexandro Bonifaz Andrés Tirado-Sánchez María José Graniel Carlos Mena Adriana Valencia Rosa María Ponce-Olivera 《Mycopathologia》2013,175(3-4):249-254
Aim
Diaper dermatitis (DD) is an inflammatory irritating condition that is common in infants. Most cases are associated with the yeast colonization of Candida or diaper dermatitis candidiasis (DDC), and therefore, the signs and symptoms improve with antimycotic treatment. Sertaconazole is a broad-spectrum third-generation imidazole derivative that is effective and safe for the treatment for superficial mycoses, such as tineas, candidiasis, and pityriasis versicolor. Our goal was to assess the efficacy and safety of sertaconazole cream (2 %) in DDC.Materials and methods
Twenty-seven patients with clinical and mycological diagnosis of DDC were enrolled and treated with 2 daily applications for 14 days and were followed-up for 2 further weeks.Results
Three etiologic agents were isolated: Candida albicans in 88.8 %, Candida parapsilosis in 7.3 %, and Candida glabrata in 3.2 %. There was an average symptom reduction from 7.1 to 3.2 in the middle of treatment and to 1.2 and 0.4 units at the end of treatment and follow-up, respectively. The treatment evaluation at the end of the follow-up period showed a total clinical and mycological cure in 88.8 %, improvement in 3.7 %, and failure in 7.4 %. There was side effect (3.7 %) of skin irritation, but the drug was not discontinued.Conclusions
Based on its safety and effectiveness, sertaconazole cream may be considered a new alternative for DDC treatment. 相似文献977.
The RNA helicase Upf1 is a multifaceted eukaryotic enzyme involved in DNA replication, telomere metabolism and several mRNA degradation pathways. Upf1 plays a central role in nonsense-mediated mRNA decay (NMD), a surveillance process in which it links premature translation termination to mRNA degradation with its conserved partners Upf2 and Upf3. In human, both the ATP-dependent RNA helicase activity and the phosphorylation of Upf1 are essential for NMD. Upf1 activation occurs when Upf2 binds its N-terminal domain, switching the enzyme to the active form. Here, we uncovered that the C-terminal domain of Upf1, conserved in higher eukaryotes and containing several essential phosphorylation sites, also inhibits the flanking helicase domain. With different biochemical approaches we show that this domain, named SQ, directly interacts with the helicase domain to impede ATP hydrolysis and RNA unwinding. The phosphorylation sites in the distal half of the SQ domain are not directly involved in this inhibition. Therefore, in the absence of multiple binding partners, Upf1 is securely maintained in an inactive state by two intramolecular inhibition mechanisms. This study underlines the tight and intricate regulation pathways required to activate multifunctional RNA helicases like Upf1. 相似文献
978.
979.
980.