全文获取类型
收费全文 | 1612篇 |
免费 | 133篇 |
国内免费 | 1篇 |
出版年
2023年 | 37篇 |
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 31篇 |
2019年 | 37篇 |
2018年 | 59篇 |
2017年 | 56篇 |
2016年 | 94篇 |
2015年 | 79篇 |
2014年 | 99篇 |
2013年 | 231篇 |
2012年 | 103篇 |
2011年 | 143篇 |
2010年 | 155篇 |
2009年 | 84篇 |
2008年 | 55篇 |
2007年 | 20篇 |
2006年 | 36篇 |
2005年 | 15篇 |
2004年 | 28篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 18篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 22篇 |
1992年 | 20篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1986年 | 4篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1972年 | 11篇 |
1971年 | 8篇 |
排序方式: 共有1746条查询结果,搜索用时 703 毫秒
101.
102.
Anu Vehmaa Hedvig Hogfors Elena Gorokhova Andreas Brutemark Towe Holmborn Jonna Engström‐Öst 《Ecology and evolution》2013,3(13):4548-4557
Zooplankton are an important link between primary producers and fish. Therefore, it is crucial to address their responses when predicting effects of climate change on pelagic ecosystems. For realistic community‐level predictions, several biotic and abiotic climate‐related variables should be examined in combination. We studied the combined effects of ocean acidification and global warming predicted for year 2100 with toxic cyanobacteria on the calanoid copepod, Acartia bifilosa. Acidification together with higher temperature reduced copepod antioxidant capacity. Higher temperature also decreased egg viability, nauplii development, and oxidative status. Exposure to cyanobacteria and its toxin had a negative effect on egg production but, a positive effect on oxidative status and egg viability, giving no net effects on viable egg production. Additionally, nauplii development was enhanced by the presence of cyanobacteria, which partially alleviated the otherwise negative effects of increased temperature and decreased pH on the copepod recruitment. The interactive effects of temperature, acidification, and cyanobacteria on copepods highlight the importance of testing combined effects of climate‐related factors when predicting biological responses. 相似文献
103.
Özlem Biçen Ünlüer Arzu Ersöz Ridvan Say Özlem Tomsuk Hülya Sivas 《Biotechnology progress》2013,29(2):472-479
This study describes preparation and use of novel labeled and antibodious polymeric nanolabels (anti‐alpha fetoprotein cross‐linked nanolabels) as an immunogenic and semisynthetic nanolabel with potential prognostic and therapeutic roles for hepatoma cancer. Specificity, uptake, and binding efficiencies of the nanolabel have been examined in a human hepatosarcoma cell line HepG2, a human colorectal cell line DLD‐1, and a mouse myoblast cell line C2. Labeling of the cells has been performed by treating live and fixed cells with varying concentrations of the nanolabels and then, the cells have been examined under a fluorescence microscope. In addition, all cell lines have also been labeled using FITC‐conjugated nanotrastuzumab to compare the results obtained with those of the binding of the FITC‐nanoanti‐alpha fetoprotein nanolabels. Results show that FITC‐conjugated anti‐alpha fetoprotein cross‐linked nanolabels have been taken up by both live and fixed cells and have efficiently and specifically labeled HepG2 cells at a quite low concentration. Taken all together, the results indicate that the novel targeted nanoimaging tools and technique demonstrated their ability to detect the distribution of the nanolabels as probes in hepatoma cells. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 472–479, 2013 相似文献
104.
Serkan Öncü 《中国病毒学》2013,28(4):193-201
Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic viral infection that is a serious threat to humans. The disease is widely distributed in Africa, Asia, and Europe and has developed into a serious public health concern. Humans become infected through the bites of ticks, by contact with a patient with CCHF, or by contact with blood or tissues from viremic livestock. Microvascular instability and impaired hemostasis are the hallmarks of the infection. Infection in human begins with nonspecific febrile symptoms, but may progress to a serious hemorrhagic syndrome with high mortality rates. Enzyme-linked immunoassay (ELISA) and polymerase chain reaction (PCR) are the most used and specific tests for the diagnosis. The mainstay of treatment is supportive. Although definitive studies are not available, ribavirin is suggested to be effective especially at the earlier phase of the infection. Uses of universal protective measures are the best way to avoid the infection. In this review, all aspects of CCHF are overviewed in light of the current literature. 相似文献
105.
Origin of the S‐Shaped JV Curve and the Light‐Soaking Issue in Inverted Organic Solar Cells 下载免费PDF全文
Anton Sundqvist Oskar J. Sandberg Mathias Nyman Jan‐Henrik Smått Ronald Österbacka 《Liver Transplantation》2016,6(6)
Inverted organic solar cells generally exhibit a strong s‐shaped kink in the current–voltage characteristics (JV curve) that may be removed by exposure to UV light (light‐soaking) leading to a drastically improved performance. Using in‐device characterization methods the origin of the light‐soaking issue in inverted solar cells employing titanium dioxide (TiO2) as an electron selective layer is clarified. An injected hole reservoir accumulated at the TiO2/organic interface of the pristine device is observed from extraction current transients; the hole reservoir increases the recombination and results in an s‐shape in the JV curve of pristine devices. The hole reservoir and the s‐shape is a result of the energetics at the selective contact in the pristine device; the effect of UV exposure is to decrease the work function of the indium tin oxide/TiO2‐contact, increasing the built‐in potential. This hinders the build‐up of the hole reservoir and the s‐shape is removed. The proposed model is in excellent agreement with drift‐diffusion simulations. 相似文献
106.
107.
108.
The effects of different cycles of starvation and re‐feeding on growth and body composition in rainbow trout (Oncorhynchus mykiss,Walbaum, 1792) 下载免费PDF全文
O. Taşbozan Y. Emre M. A. Gökçe C. Erbaş F. Özcan E. Kıvrak 《Zeitschrift fur angewandte Ichthyologie》2016,32(3):583-588
This study was designed to investigate the effects of starvation and re‐feeding cycles on the growth performance and body chemical composition of Oncorhynchus mykiss juveniles. A total of 360 juveniles with initial mean weights (IW) of 8.46 ± 0.07 g (n = 360) were stocked into 400‐L tanks in triplicate for each group, with 30 juveniles per tanks. The control group received regular feed, as is the common practice. The three other groups were periodically starved: 1 day starvation followed by 6 days re‐feeding (S1), 2 days starvation followed by 5 days re‐feeding (S2) and 3 days starvation followed by 4 days re‐feeding (S3). The experiment lasted for 10 weeks, over the course of which the water flow rate was 4 L min?1 and the water quality parameters determined as: temperature 14.4 ± 1.1°C, oxygen 8.2 ± 0.4 mg L?1 and pH 7.5 ± 0.2. At the end of the study, S1 had the best growth performance (final weight, specific growth rate, average daily growth) of all test groups (P < 0.05). The lowest daily feed intake (DFI) and growth performance parameters were observed in S3 (P < 0.05), while protein efficiency ratio (PER), net protein utilization (NPU) and lipid efficiency ratio (LER) were higher in the S3 fish group than in the other groups (P < 0.05). Whole body protein and lipid contents were highest in S1 fish. The hepatosomatic index (HSI) and viscerosomatic index (VSI) were significantly different among groups (P < 0.05). Feed conversion ratio (FCR) was significantly lower in starvation groups S1, S2 and S3 than in the control (P < 0.05). Compensation coefficient (CC) values were higher than 1 in all starvation groups. The concluding indicate that rainbow trout exposed to 1 and 2 days of starvation in week cycles could achieve over compensation compared to the control. Additionally, partial growth compensation and improved feed utilization could be achieved in a starvation group within 3 days in a week, by beginning with the juvenile size over a 10‐week experimental period. 相似文献
109.
Do individual Activity Patterns of Brown Trout (Salmo trutta) alter the Exposure to Parasitic Freshwater Pearl Mussel (Margaritifera margaritifera) Larvae? 下载免费PDF全文
Niklas Wengström Fredrik Wahlqvist Joacim Näslund David Aldvén Libor Závorka Martin E Österling Johan Höjesjö 《Ethology : formerly Zeitschrift fur Tierpsychologie》2016,122(9):769-778
The hypothesis that interindividual differences in the activity of brown trout alter the exposure to parasitic freshwater pearl mussel glochidia was tested in a Swedish stream. Wild yearling brown trout (N = 103) were caught, individually tagged for identification and scored for open‐field activity during standardized laboratory tests in June. Fifty gravid freshwater pearl mussels were relocated to the stream, where after the trout were released back into the stream. The fish were recaptured in October (N = 35), checked for glochidia encystment (infested individuals: n = 6) and re‐scored for open‐field activity traits. Swimming velocity during the test was higher in fish infected with glochidia, suggesting that high activity could increase their exposure to glochidia. Potentially, as metabolism rate and ventilation rate typically increase with activity, elevated activity may lead to an increased likelihood of glochidia passing over the gills. This novel finding suggests that glochidia infestation is non‐random and that the behaviour of the host fish can influence the likelihood of glochidia infestation. 相似文献
110.
Mehlika Dilek Altintop Belgin Sever Ahmet Özdemir Gökhan Kuş Pinar Oztopcu-Vatan Selda Kabadere 《Journal of enzyme inhibition and medicinal chemistry》2016,31(3):410-416
Fourteen new naphthalene-based thiosemicarbazone derivatives were designed as anticancer agents against LNCaP human prostate cancer cells and synthesized. MTT assay indicated that compounds 6, 8 and 11 exhibited inhibitory effect on LNCaP cells. Among these compounds, 4-(naphthalen-1-yl)-1-[1-(4-hydroxyphenyl)ethylidene)thiosemicarbazide (6), which caused more than 50% death on LNCaP cells, was chosen for flow cytometric analysis of apoptosis. Flow cytometric analysis pointed out that compound 6 also showed apoptotic effect on LNCaP cells. Compound 6 can be considered as a promising anticancer agent against LNCaP cells owing to its potent cytotoxic activity and apoptotic effect. 相似文献