全文获取类型
收费全文 | 330篇 |
免费 | 52篇 |
国内免费 | 17篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 16篇 |
2019年 | 21篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 16篇 |
2015年 | 18篇 |
2014年 | 29篇 |
2013年 | 42篇 |
2012年 | 18篇 |
2011年 | 21篇 |
2010年 | 18篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 15篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 5篇 |
2003年 | 17篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1982年 | 3篇 |
排序方式: 共有399条查询结果,搜索用时 31 毫秒
391.
Laura Super Analise Hofmann Connie Leung Mabel Ho Emma Harrower Najah Adreak Zohreh Rezaie Manesh 《Ecology and evolution》2021,11(8):3464
Instructors can deliberately design for equity, diversity, and inclusion, including for large first‐year classes, and now instructors have added challenges given COVID‐19. Our paper explores the question: How do we integrate equity, diversity, and inclusion and universal design for learning (UDL) into first‐year, undergraduate ecology and evolution introductory lessons given the COVID‐19 pandemic? Given the large field exploring equity, diversity, and inclusion, we chose to focus on developing reflective practice question rubrics for before, during, and after lessons to encourage UDL for instructors, teaching assistants, and learners. We conducted a focus group within our team and discussed ideas related to online learning, including related pitfalls and solutions. Lastly, we created a figure to illustrate ideas and end with a general discussion. Our reflective practice questions for UDL rubrics, figure, focus group, and discussion aim to increase positive action for equity, diversity, and inclusion in the classroom and beyond. 相似文献
392.
《Cell reports》2023,42(7):112766
- Download : Download high-res image (243KB)
- Download : Download full-size image
393.
Excavations conducted by H.J. Deacon in the 1970s at Boomplaas Cave (BPA) uncovered a stratified sequence of Middle Stone Age (MSA) and Later Stone Age (LSA) deposits spanning the last >65,000 years. This study provides the first comprehensive and integrated taphonomic and paleoecological analysis of the BPA large mammals, with a focus on its implications for understanding human adaptations and environmental changes in southern Africa's Cape Floristic Region (CFR), an area that features prominently in understanding modern human origins. Taphonomic data indicate a complex history of human, carnivore, and raptor accumulation of the large mammal assemblage. The anthropogenic signal is largely absent from the bottom of the sequence (>65,000 years ago), intermediate in MSA and LSA assemblages from ∼50,000 to 20,000 years ago, and strong in LSA deposits post-dating the Last Glacial Maximum (LGM). When viewed in the broader CFR context, the inferred occupation history of BPA is consistent with the hypothesis that both MSA and LSA human populations were concentrated on the submerged coastline from ∼60,000 to ∼20,000 years ago. Intensive occupation following the LGM parallels an apparent increase in regional population densities, which may have been driven in part by rising sea levels. The BPA ungulate assemblage is characterized by the rise and decline of a taxonomically diverse grazing community, which peaks during the LGM. These changes are not correlated with taphonomic shifts, meaning that they are likely driven by environmental factors, namely the expansion and contraction of grassland habitats. Changes in ungulate diversity indicate that effective precipitation was highest during the LGM, corresponding with an intensified winter rainfall system. This is consistent with recent arguments that the LGM in this region may not have been extremely harsh and arid. 相似文献
394.
Yves Coppens 《Comptes Rendus Palevol》2017,16(2):196-199
The international expedition to the Omo region of Ethiopia clearly demonstrates for the first time in the 1970s that a discernable change from a probable moist climate regime occurred some 3 millions years ago. This climate change brought about an adaptation process and caused environmental adaptations for all vertebrates. This included ecosystems throughout the central, eastern, and southern regions of tropical Africa that surrounded the equatorial nucleus of dense forest. The Hominids who lived in these ecosystems did not escape these changes, but experienced five, maybe six adjustments to the climatic alteration, e.g., physical sturdiness, feeding habits, locomotion, central nervous system. As always in such circumstances, nature reacts by enabling variations on the same theme by providing answers, which are often comparable, but never the same! Similar to the instance of the vertebrates and Hominids cited above, the Human race, together with all its specific peculiarities, is an example of adaptations made necessary due to climatic and environmental variations. 相似文献
395.
Xueyu Du Goran Gellerstedt Jiebing Li 《The Plant journal : for cell and molecular biology》2013,74(2):328-338
It is of both theoretical and practical importance to develop a universally applicable approach for the fractionation and sensitive lignin characterization of lignin–carbohydrate complexes (LCCs) from all types of lignocellulosic biomass, both natively and after various types of processing. In the present study, a previously reported fractionation approach that is applicable for eucalyptus (hardwood) and flax (non‐wood) was further improved by introducing an additional step of barium hydroxide precipitation to isolate the mannan‐enriched LCC (glucomannan‐lignin, GML), in order to suit softwood species as well. Spruce wood was used as the softwood sample. As indicated by the recovery yield and composition analysis, all of the lignin was recovered in three LCC fractions: a glucan‐enriched fraction (glucan‐lignin, GL), a mannan‐enriched fraction (GML) and a xylan‐enriched fraction (xylan‐lignin, XL). All of the LCCs had high molecular masses and were insoluble or barely soluble in a dioxane/water solution. Carbohydrate and lignin signals were observed in 1H NMR, 13C CP‐MAS NMR and normal‐ or high‐sensitivity 2D HSQC NMR analyses. The carbohydrate and lignin constituents in each LCC fraction are therefore believed to be chemically bonded rather than physically mixed with one another. The three LCC fractions were found to be distinctly different from each other in terms of their lignin structures, as revealed by highly sensitive analyses by thioacidolysis‐GC, thioacidolysis‐SEC and pyrolysis‐GC. 相似文献
396.
Kristy Deiner Roland A. Knapp Daniel M. Boiano Bernie May 《Molecular ecology resources》2013,13(5):820-831
The first step in many community ecology studies is to produce a species list from a sample of individuals. Community ecologists now have two viable ways of producing a species list: morphological and barcode identification. In this study, we compared the taxonomic resolution gained by a combined use of both methods and tested whether a change in taxonomic resolution significantly impacted richness estimates for benthic macroinvertebrates sampled from ten lakes in Sequoia National Park, USA. Across all lakes, 77 unique taxa were identified and 42% (32) were reliably identified to species using both barcode and morphological identification. Of the 32 identified to species, 63% (20) were identified solely by comparing the barcode sequence from cytochrome oxidase I to the Barcode of Life reference library. The increased resolution using a combined identification approach compared to identifications based solely on morphology resulted in a significant increase in estimated richness within a lake at the order, family, genus and species levels of taxonomy (P < 0.05). Additionally, young or damaged individuals that could not be identified using morphology were identified using their COI sequences to the genus or species level on average 75% of the time. Our results demonstrate that a combined identification approach improves accuracy of benthic macroinvertebrate species lists in alpine lakes and subsequent estimates of richness. We encourage the use of barcodes for identification purposes and specifically when morphology is insufficient, as in the case of damaged and early life stage specimens of benthic macroinvertebrates. 相似文献
397.
Magdalena Niedziakowska Karolina Doan Marcin Grny Maciej Sykut Krzysztof Stefaniak Natalia Piotrowska Bogumia Jdrzejewska Bogdan Ridush Sawomira Paweczyk Pawe Mackiewicz Ulrich Schmlcke Pavel Kosintsev Daniel Makowiecki Maxim Charniauski Dariusz Krasnodbski Eve Ranname Urmas Saarma Marine Arakelyan Ninna Manaseryan Vadim V. Titov Pavel Hulva Adrian Blescu Ralph Fyfe Jessie Woodbridge Katerina Trantalidou Vesna Dimitrijevi Oleksandr Kovalchuk Jarosaw Wilczyski Theodor Obad Grzegorz Lipecki Alesia Arabey Ana Stankovi 《Journal of Biogeography》2021,48(1):147-159
398.
399.