全文获取类型
收费全文 | 4333篇 |
免费 | 1009篇 |
国内免费 | 2763篇 |
出版年
2024年 | 4篇 |
2023年 | 291篇 |
2022年 | 262篇 |
2021年 | 357篇 |
2020年 | 501篇 |
2019年 | 573篇 |
2018年 | 429篇 |
2017年 | 400篇 |
2016年 | 427篇 |
2015年 | 347篇 |
2014年 | 388篇 |
2013年 | 381篇 |
2012年 | 340篇 |
2011年 | 321篇 |
2010年 | 291篇 |
2009年 | 294篇 |
2008年 | 282篇 |
2007年 | 321篇 |
2006年 | 253篇 |
2005年 | 241篇 |
2004年 | 182篇 |
2003年 | 172篇 |
2002年 | 138篇 |
2001年 | 150篇 |
2000年 | 113篇 |
1999年 | 88篇 |
1998年 | 81篇 |
1997年 | 60篇 |
1996年 | 54篇 |
1995年 | 64篇 |
1994年 | 48篇 |
1993年 | 26篇 |
1992年 | 34篇 |
1991年 | 36篇 |
1990年 | 26篇 |
1989年 | 21篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 29篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1958年 | 3篇 |
排序方式: 共有8105条查询结果,搜索用时 15 毫秒
21.
22.
《植物生态学报》2013,22(3):277
A scientific workflow system is designed specifically to organize, manage and execute a series of research steps, or a workflow, in a given runtime environment. The vision for scientific workflow systems is that the scientists around the world can collaborate on designing global-scaled experiments, sharing the data sets, experimental processes, and results on an easy-to-use platform. Each scientist can create and execute their own workflows and view results in real-time, and then subsequently share and reuse workflows among other scientists. Two case studies, using the Kepler system and BioVeL, are introduced in this paper. Ecological niche modeling process, which is a specialized form of scientific workflow system included in both Kepler system and BioVeL, was used to describe and discuss the features, developmental trends, and problems of scientific workflows. 相似文献
23.
24.
Justin C. Luong Patrick L. Turner Celina N. Phillipson Katja C. Seltmann 《Ecological Entomology》2019,44(4):471-479
1. It is hypothesised that ecological restoration in grasslands can induce an alternative stable state shift in vegetation. The change in vegetation influences insect community assemblages and allows for greater functional redundancy in pollination and refuge for native insect species. 2. Insect community assemblages at eight coastal California grassland sites were evaluated. Half of these sites had undergone restoration through active revegetation of native grassland flora and half were non‐restored. Insects were collected from Lupinus bicolor (Fabaceae) within 2 × 2‐m2 plots in spring 2017. Lupinus bicolor is a common native species that is used in California restoration projects, and home and state landscaping projects. 3. Ordination demonstrated that insect community assemblages were different between restored and non‐restored sites. These differences were seen in insect functional groups as well as taxa‐specific differences and were found to be driven by environmental characteristics such as non‐native forb cover. 4. Functional redundancy of herbivores decreased at restored sites, while pollinators became more redundant compared with non‐restored sites. The assemblages of the common species found at restoration sites contained more native insects than those found at non‐restored sites, including species such as Bombus vosnesenskii. 5. Local grassland restoration has the potential to induce an alternative stable state change and affect insect community assemblages. Additionally, it was found that grassland restoration can be a potential conservation tool to provide refugia for bumblebees (Bombus), but additional studies are required to fully understand its broader applicability. 相似文献
25.
26.
27.
28.
Neopomacentrus filamentosus, a common damselfish on the Indo–Australian archipelago, undergoes significant shifts in size and mitochondrial genetic structure upon larval settlement and metamorphosis to juvenile stages. We characterized five polymorphic microsatellite loci in order to study temporal genetic shifts within a single generation of N. filamentosus sampled first as larval settlers then again as demersal juvenile recruits. All loci were extremely polymorphic and exhibited high levels of heterozygosity. While all loci from the larval samples conformed to Hardy – Weinberg expectations, significant heterozygote deficiencies were seen in two loci in the juvenile samples, likely due to extreme size‐selective mortality imposed post‐settlement. 相似文献
29.
- Model organisms such as Drosophila melanogaster have been key tools for advancing our fundamental and applied knowledge in biological and biomedical sciences. However, model organisms have become intertwined with the idea of controlled and stable laboratory environments, and their natural history has been overlooked.
- In holometabolous insects, lack of natural history information on larval ecology has precluded major advances in the field of developmental ecology, especially in terms of manipulations of population density early in life (i.e., larval density). This is because of relativistic and to some extent, arbitrary methodologies employed to manipulate larval densities in laboratory studies. As a result, these methodologies render comparisons between species impossible, precluding our understanding of macroevolutionary responses to population densities during development that can be derived from comparative studies.
- We recently proposed a new conceptual framework to address this issue, and here, we provide the first natural history investigation of Drosophila melanogaster larval density under such framework. First, we characterized the distribution of larval densities in a wild population of D. melanogaster using rotting apples as breeding substrate in a suburban area in Sweden.
- Next, we compiled the commonly used methodologies for manipulating larval densities in laboratory studies from the literature and found that the majority of laboratory studies identified did not manipulate larval densities below or above the densities observed in nature, suggesting that we have yet to study true life history and physiological responses to low and high population densities during D. melanogaster development.
- This is, to our knowledge, the first direct natural history account of larval density in nature for this model organism. Our study paves the way for a more integrated view of organismal biology which re‐incorporates natural history of model organisms into hypothesis‐driven research in developmental ecology.
30.
F. H. Dawson 《Hydrobiologia》1981,77(1):71-76
The design and characteristics of inexpensive and simply constructed equal-energy response photosynthetic irradiance sensors is described for use particularly where several cells are required in comparative ecological studies either above or below water. The dimensions of the sensors can be changed proportionally to suit different applications or components. The response of the sensor to irradiance at varying angles corresponds very closely to that required by the cosine law. The sensor is comparatively insensitive to other environmental variables in field use and gave a stable output; the long term drift was proportional to electrical output but in continuous use, drift is regular and could reach -0.08 year-1 of the total. The spectral range and cosine response is discussed in comparison to other more expensive (x 5–10) commercially available, sensors and to local standards. 相似文献