全文获取类型
收费全文 | 15085篇 |
免费 | 1017篇 |
国内免费 | 1篇 |
专业分类
16103篇 |
出版年
2023年 | 114篇 |
2022年 | 224篇 |
2021年 | 443篇 |
2020年 | 292篇 |
2019年 | 355篇 |
2018年 | 444篇 |
2017年 | 405篇 |
2016年 | 628篇 |
2015年 | 947篇 |
2014年 | 1012篇 |
2013年 | 1254篇 |
2012年 | 1479篇 |
2011年 | 1331篇 |
2010年 | 827篇 |
2009年 | 710篇 |
2008年 | 868篇 |
2007年 | 852篇 |
2006年 | 799篇 |
2005年 | 656篇 |
2004年 | 622篇 |
2003年 | 547篇 |
2002年 | 440篇 |
2001年 | 92篇 |
2000年 | 66篇 |
1999年 | 96篇 |
1998年 | 83篇 |
1997年 | 74篇 |
1996年 | 64篇 |
1995年 | 48篇 |
1994年 | 53篇 |
1993年 | 37篇 |
1992年 | 31篇 |
1991年 | 22篇 |
1990年 | 22篇 |
1989年 | 19篇 |
1988年 | 12篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1972年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Vanessa Mendonça Diana Boaventura Henrique Cabral Ana C. F. Silva 《Marine Biology Research》2016,12(2):125-132
Chitons are very common molluscs on European rocky shores. They are common prey of fish and crabs and often display several colour morphs within a given habitat. Predation is one of the potential mechanisms accounting for chiton colour polymorphism. The colour variation is considered to provide a camouflage protection through a match with the substratum surface typology. However, the effectiveness of chiton polymorphism as a predation defence requires further investigation. Previously we found a relationship between chiton colour morphs and substrate characteristics, with chitons most commonly found on substrates that were of similar colour to their shells. Here, we examined whether each morph displayed an active choice for matching the substratum. Next, we assessed if the predation success of the intertidal common crab Carcinus maenas varied significantly with the absence/presence of an apparent camouflage effect created between the chiton colour morph and the substratum type. The present study indicates that chiton colour morphs probably actively choose substratum types where they blend in. Carcinus maenas was able to prey on all Lepidochitona cinereus colour morphs, regardless of the substrate camouflage effect. Surprisingly, the predation frequency was higher on camouflaged chitons than on contrasting chitons. It was concluded that chiton camouflage is probably not a defence mechanism against predation by the crab C. maenas, and that chiton colour polymorphism is probably promoted by other, more visual predators. 相似文献
83.
Diana Vilas Boas Carina Almeida Sanna Sillankorva Ana Nicolau Joana Azeredo 《Biofouling》2016,32(2):179-190
Bacteriophage–host interaction studies in biofilm structures are still challenging due to the technical limitations of traditional methods. The aim of this study was to provide a direct fluorescence in situ hybridization (FISH) method based on locked nucleic acid (LNA) probes, which targets the phage replication phase, allowing the study of population dynamics during infection. Bacteriophages specific for two biofilm-forming bacteria, Pseudomonas aeruginosa and Acinetobacter, were selected. Four LNA probes were designed and optimized for phage-specific detection and for bacterial counterstaining. To validate the method, LNA-FISH counts were compared with the traditional plaque forming unit (PFU) technique. To visualize the progression of phage infection within a biofilm, colony-biofilms were formed and infected with bacteriophages. A good correlation (r = 0.707) was observed between LNA-FISH and PFU techniques. In biofilm structures, LNA-FISH provided a good discrimination of the infected cells and also allowed the assessment of the spatial distribution of infected and non-infected populations. 相似文献
84.
85.
Ramos Patrícia A. B. Ferro Ana M. Oliveira M. Margarida Gonçalves Sónia Freire Carmen S. R. Silvestre Armando J. D. Duarte Maria F. 《Phytochemistry Reviews》2019,18(2):495-526
Phytochemistry Reviews - Cynara cardunculus health benefits have aroused much interest, leading to the discovery of valuable bioactive compounds with a crucial role in plant defence. Guaianolides... 相似文献
86.
Food Biophysics - Composite gels of whey protein isolate (WPI) and potato starch (PS) were formed by calcium chloride induced cold gelation to obtain microstructures where native starch granules... 相似文献
87.
Soeth Marcelo Fávaro Luis Fernando Spach Henry Louis Daros Felippe Alexandre Woltrich Ana Emília Correia Alberto Teodorico 《Ichthyological Research》2019,66(1):140-154
Ichthyological Research - This is the first study to investigate the age, growth and reproductive biology of the Atlantic spadefish Chaetodipterus faber in southern Brazil. A total of 625... 相似文献
88.
Regime shifts of Mediterranean forest carbon uptake and reduced resilience driven by multidecadal ocean surface temperatures 总被引:1,自引:0,他引:1
Jofre Carnicer Cristina Domingo‐Marimon Miquel Ninyerola Jesus Julio Camarero Ana Bastos Jorge Lpez‐Parages Laura Blanquer Beln Rodríguez‐Fonseca Timothy M. Lenton Vasilis Dakos Montserrat Ribas Emilia Gutirrez Josep Peuelas Xavier Pons 《Global Change Biology》2019,25(8):2825-2840
The mechanisms translating global circulation changes into rapid abrupt shifts in forest carbon capture in semi‐arid biomes remain poorly understood. Here, we report unprecedented multidecadal shifts in forest carbon uptake in semi‐arid Mediterranean pine forests in Spain over 1950–2012. The averaged carbon sink reduction varies between 31% and 37%, and reaches values in the range of 50% in the most affected forest stands. Regime shifts in forest carbon uptake are associated with climatic early warning signals, decreased forest regional synchrony and reduced long‐term carbon sink resilience. We identify the mechanisms linked to ocean multidecadal variability that shape regime shifts in carbon capture. First, we show that low‐frequency variations of the surface temperature of the Atlantic Ocean induce shifts in the non‐stationary effects of El Niño Southern Oscillation (ENSO) on regional forest carbon capture. Modelling evidence supports that the non‐stationary effects of ENSO can be propagated from tropical areas to semi‐arid Mediterranean biomes through atmospheric wave trains. Second, decadal changes in the Atlantic Multidecadal Oscillation (AMO) significantly alter sea–air heat exchanges, modifying in turn ocean vapour transport over land and land surface temperatures, and promoting sustained drought conditions in spring and summer that reduce forest carbon uptake. Third, we show that lagged effects of AMO on the winter North Atlantic Oscillation also contribute to the maintenance of long‐term droughts. Finally, we show that the reported strong, negative effects of ocean surface temperature (AMO) on forest carbon uptake in the last decades are unprecedented over the last 150 years. Our results provide new, unreported explanations for carbon uptake shifts in these drought‐prone forests and review the expected impacts of global warming on the profiled mechanisms. 相似文献
89.
90.
Martins Nicole Magalhães Rui Castro Carolina Couto Ana Díaz-Rosales Patrícia Oliva-Teles Aires Peres Helena 《Amino acids》2019,51(9):1307-1321
Amino Acids - This study aimed to evaluate the effect of taurine (tau) supplementation to low fishmeal (FM) diets on growth performance, oxidative status, and immune response of European seabass... 相似文献