全文获取类型
收费全文 | 3930篇 |
免费 | 363篇 |
国内免费 | 2篇 |
出版年
2023年 | 32篇 |
2022年 | 22篇 |
2021年 | 109篇 |
2020年 | 76篇 |
2019年 | 115篇 |
2018年 | 123篇 |
2017年 | 116篇 |
2016年 | 140篇 |
2015年 | 213篇 |
2014年 | 221篇 |
2013年 | 302篇 |
2012年 | 314篇 |
2011年 | 317篇 |
2010年 | 178篇 |
2009年 | 171篇 |
2008年 | 255篇 |
2007年 | 206篇 |
2006年 | 200篇 |
2005年 | 191篇 |
2004年 | 168篇 |
2003年 | 151篇 |
2002年 | 124篇 |
2001年 | 57篇 |
2000年 | 52篇 |
1999年 | 60篇 |
1998年 | 45篇 |
1997年 | 29篇 |
1996年 | 20篇 |
1995年 | 12篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 14篇 |
1988年 | 22篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1979年 | 4篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 12篇 |
1973年 | 4篇 |
1972年 | 7篇 |
1968年 | 5篇 |
排序方式: 共有4295条查询结果,搜索用时 178 毫秒
901.
Lara Maistrello Paride Dioli Massimo Bariselli Gian Lorenzo Mazzoli Isabella Giacalone-Forini 《Biological invasions》2016,18(11):3109-3116
Early detection of invasive alien species and the ability to track their spread are critical for undertaking appropriate management decisions. Citizen science surveys are potentially valuable tools for quickly obtaining information on biodiversity and species distributions. The Asian brown marmorated stink bug, Halyomorpha halys, is an invasive pest of agricultural crops and a dwelling nuisance. Halyomorpha halys was first recorded in Italy in 2012 in Emilia Romagna, one of the most important fruit producing regions of Europe. To rapidly obtain data on its distribution in the newly invaded area, a survey that combined citizen science and active search was set up using multimedia channels. Data concerning when, where and how the bugs were spotted were collected, together with photographs and specimens. The survey detected established breeding populations in different areas of Northern Italy and Southern Switzerland, indicating a potentially high risk for crop damage that extends beyond the territories of first detection. Furthermore, new data on H. halys phenology, host plants, voltinism and behaviour were obtained. The importance of citizen science in early detection of introduced pest species is highlighted. This paper also provides a picture-based key to recognize H. halys from similar pentatomids in the world. 相似文献
902.
903.
904.
Effect of grazing on the population of Matteuccia struthiopteris at the southern limit of its distribution in Europe 下载免费PDF全文
Marco Landi Antonio Zoccola Vincenzo Gonnelli Lorenzo Lastrucci Carlo Saveri Giovanni Quilghini Alessandro Bottacci Claudia Angiolini 《Plant Species Biology》2016,31(1):3-10
We investigated the impact of deer on an isolated marginal population of Matteuccia struthiopteris and on its plant community in the northern Apennines, where in recent decades the species has decreased dramatically. Our experiment was based on a 6‐year before and after control impact (BACI) design, comparing plots with deer grazing and plots where deer were excluded. Exclusion of grazing interacted with years, increasing the size of existing plants and favoring production of sporophylls. The yearly sequence of increase and decline of ramets and sterile leaves followed the same pattern in the two treatments. This indicated that their annual variation in growth depended on the sequence of more and less favorable years. Few and short plants were associated with grazing, whereas tall plants, shrubs, and tree regeneration were associated with fenced plots. The few plants to persist and dominate on heavily grazed areas were Oxalis acetosella and Cardamine species, while the genus Rubus and tree saplings were grazing‐sensitive species in this forest. Tall herbaceous species increased in size in the fenced areas, however, M. struthiopteris drew more advantage in terms of growth of leaves, showing greater cover than other species. Thus, deer grazing is becoming a threat for the survival of M. struthiopteris in southern Europe where it is already threatened in the long term by climate change. 相似文献
905.
Lorenzo Tonetti Marco Fabbri Michele Boreggiani Pietro Guastella Monica Martoni Noelia Ruiz Herrera 《Biological Rhythm Research》2016,47(4):573-581
The present study aimed to explore for the first time the relationship between circadian preference and different decision-making styles. In total, 501 young adults (330 females), with a mean age of 21.07 ± 1.99 years, took part in the study. The participants completed the reduced version of the morningness–eveningness questionnaire (rMEQ) and the general decision-making style inventory (GDMS). The rMEQ enabled to assess the circadian preference, with lower rMEQ scores pointing toward eveningness preference. The GDMS measured five decision-making styles: rational, intuitive, dependent, avoidant and spontaneous. Higher scores on each GDMS decision-making style reflect a higher prevalence of the corresponding style. A set of multiple regression analyses was performed with rMEQ score, gender and age as predictors together with each GDMS decision-making style as dependent variable. rMEQ score proved to be the only significant (negative) predictor of avoidant and spontaneous decision-making styles, i.e. lower rMEQ score (tendency toward eveningness) significantly predicted higher score at these decision-making styles. The present results suggest that eveningness preference is significantly related to avoidant and spontaneous decision-making styles in young adults. Such results will be discussed with reference to the effects of decision-making styles on decision-making in different types of workers and mental health. 相似文献
906.
TDP‐43 loss of function inhibits endosomal trafficking and alters trophic signaling in neurons 下载免费PDF全文
Benjamin M Schwenk Hannelore Hartmann Alperen Serdaroglu Martin H Schludi Daniel Hornburg Felix Meissner Denise Orozco Alessio Colombo Sabina Tahirovic Meike Michaelsen Franziska Schreiber Simone Haupt Michael Peitz Oliver Brüstle Clemens Küpper Thomas Klopstock Markus Otto Albert C Ludolph Thomas Arzberger Peer‐Hendrik Kuhn Dieter Edbauer 《The EMBO journal》2016,35(21):2350-2370
907.
Valentina Castellani Lorenzo Benini Serenella Sala Rana Pant 《The International Journal of Life Cycle Assessment》2016,21(8):1159-1169
Purpose
Distance-to-target (DTT) methods are weighting methods aimed at assessing the distance of an existing situation from a desired state (the target). Weighting factors in DTT methods could be based on calculation which is performed on normalization factors (NFs) developed for life cycle assessment (LCA). At present, some DTT weighting sets have been developed. However, there is no DTT weighting set assessing the distance of EU domestic impacts from the desired state set by EU binding or non-binding policy targets (e.g., those related to the “Climate and Energy Package” and the “Roadmap to a Resource Efficient Europe”).Methods
In the present work, a methodology to derive target references from policy-based targets in 2020 (TRs2020), both binding (A) and non-binding (B), is presented. Resulting target factors and DTT weighting factors are then compared to the current normalisation factors (based on 2010 normalization references). The resulting weighting factor (WF) sets are presented and discussed in light of their use for decision support in policy and business contexts. We applied the WF sets to characterization results to an example (the EU energy mix process) aiming at illustrating key differences and effects on the results.Results and discussion
The three reference sets (NRs2010, TRs2020A, and TRs2020B) show, in some impact categories, a relatively small difference. WFs referred to set A and set B result to be quite similar, with the only exception of water depletion impact category, for which a very relevant change is foreseen when considering the effect of the non-binding target of limiting the abstraction of water resource to 20 % of the available renewable water resources. This is mainly due to the higher difficulty in deriving quantitative targets from non-binding strategies and policies rather than from binding ones.Conclusions
The resulting weighting sets present strengths and limitations. The translation of policy targets into quantitative modifications to the baseline inventories appeared to be not a straightforward task, due to several reasons discussed in the paper (e.g., not all the policy targets are expressed in quantitative terms or can be translated into quantitative reductions and modifications of the elementary flows in the existing baseline inventories). Aiming at improving the effectiveness in supporting policies, further development of the methodology may be the integration with other DTT approaches such those based on carrying capacity, developed to integrate Earth’s carrying capacity concept and planetary boundaries.908.
Spinal lipoma as a dysembryogenetic anomaly: Four unusual cases of ectopic iliac rib within the spinal lipoma 下载免费PDF全文
909.
Lorenzo Drago Roberta De Grandi Gianfranco Altomare Paolo Pigatto Oliviero Rossi Marco Toscano 《Clinical and molecular allergy : CMA》2016,14(1):2
Background
Psoriasis and atopic dermatitis (AD) are chronic inflammatory skin diseases, which negatively influence the quality of life. In the last years, several evidences highlighted the pivotal role of skin bacteria in worsening the symptomatology of AD and psoriasis. In the present study we evaluated the skin microbiota composition in accurately selected subjects affected by (AD) and psoriasis.Methods
Three first cousins were chosen for the study according to strict selection of criteria. One subject was affected by moderate AD, one had psoriasis and the last one was included as healthy control. Two lesional skin samples and two non-lesional skin samples (for AD and psoriatic subjects) from an area of 2 cm2 behind the left ear were withdrawn by mean of a curette. For the healthy control, two skin samples from an area of 2 cm2 behind the left ear were withdrawn by mean of a curette. DNA was extracted and sequencing was completed on the Ion Torrent PGM platform. Culturing of Staphylococcus aureus from skin samples was also performed.Results
The psoriatic subject showed a decrease in Firmicutes abundance and an increase in Proteobacteria abundance. Moreover, an increase in Streptococcaceae, Rhodobacteraceae, Campylobacteraceae and Moraxellaceae has been observed in psoriatic subject, if compared with AD individual and control. Finally, AD individual showed a larger abundance of S. aureus than psoriatic and healthy subjects. Moreover, the microbiota composition of non-lesional skin samples belonging to AD and psoriatic individuals was very similar to the bacterial composition of skin sample belonging to the healthy control.Conclusion
Significant differences between the skin microbiota of psoriatic individual and healthy and AD subjects were observed.910.