全文获取类型
收费全文 | 797篇 |
免费 | 40篇 |
国内免费 | 1篇 |
专业分类
838篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 29篇 |
2021年 | 41篇 |
2020年 | 36篇 |
2019年 | 69篇 |
2018年 | 49篇 |
2017年 | 29篇 |
2016年 | 53篇 |
2015年 | 45篇 |
2014年 | 53篇 |
2013年 | 65篇 |
2012年 | 67篇 |
2011年 | 52篇 |
2010年 | 37篇 |
2009年 | 24篇 |
2008年 | 31篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 16篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有838条查询结果,搜索用时 0 毫秒
21.
Simone?RiehlEmail author Marion?Benz Nicholas?J.?Conard Hojjat?Darabi Katleen?Deckers Hassan?Fazeli?Nashli Mohsen?Zeidi-Kulehparcheh 《Vegetation History and Archaeobotany》2012,21(2):95-106
The beginnings of agriculture throughout the Fertile Crescent are still not completely understood, particularly at the eastern end of the Fertile Crescent in the area of modern Iran. Archaeobotanical samples from Epipalaeolithic/PPNA Körtik Tepe in southeastern Turkey and from the Pre-Pottery Neolithic sites of Chogha Golan and East Chia Sabz in south western Iran were studied in order to define the status of cultivation at these sites. Preliminary results show the presence of abundant wild progenitor species of crops at the Iranian sites before 10600 cal. b.p., and very few wild progenitor species at Körtik Tepe dated to 11700–11250 cal. b.p. The Iranian sites also indicate size increase of wild barley grain across a sequence of 400 years through either cultivation or changing moisture conditions. 相似文献
22.
The plasmonic effects due to the coupling of silver spherical nanoparticles with silver nanograting electrodes on active medium of the photo detector are investigated. Calculations show that the coupling of nanoparticles and nanograting electrodes at the surface of active medium lead to reflection wave into the active medium, and electrodes can participate in the absorption and quantum efficiency. Calculations show that the addition of nanograting electrodes to the structure can lead to increase the absorption coefficient up to 120% respect to the plasmonic structure containing only nanoparticles and about 4.5 times that of conventional (metal-semiconductor -metal ) MSM photo detectors.
相似文献23.
24.
Hasan Farajipour Susan Rahimian Mohsen Taghizadeh 《Journal of cellular biochemistry》2019,120(5):6886-6893
The retina is the neural portion and light-sensitive layer of the eye, which has been observed in most of the vertebrates. The retina is composed of light-sensitive cells that absorb light and convert it into neural signals. These signals are sent to the brain for visual recognition. It has been shown that many pathogenesis conditions, including inflammation, angiogenesis, oxidative stress, and imbalanced histone modifications in the retina are associated with initiation and progression of retinal diseases (ie, glaucoma, diabetic retinopathy, and age-related macular degeneration). Currently available treatments include laser surgery, freezing, stem-cell therapy, shrinking abnormal blood vessels. It has some limitations, such as invasive methods, high costs, and many side effects. Hence, finding a new therapeutic platform for stopping or slowing of the disease progression is required. Curcumin is a natural product, which is associated with a wide range of properties, such as antioxidant, anti-inflammatory, antiangiogenic, and antitumor activates. It exerts therapeutic effects via activation/inhibition cellular and molecular targets involved in various diseases, such as retinal diseases. Increasing evidence revealed that curcumin can be used as a therapeutic option in the treatment of different retinal diseases. Here, we summarized various clinical and preclinical studies that used curcumin as a therapeutic agent in the treatment of retinal disorders. 相似文献
25.
Response surface methodology (RSM) was used to evaluate the effects of fermentation parameters for cellulase production by Trichoderma reesei QM9414 and T. reesei MCG77 in solid-state fermentation using rice bran as substrate. Initial pH, moisture content and temperature were optimized using filter paper activity (FPA) as response. Statistical analysis of the results for T. reesei QM9414 showed that only moisture content had significant effect on cellulase activity and had a linear effect on enzyme activity (maximum enzyme activities were obtained at 70% moisture content). The results for T. reesei MCG77 showed that temperature and moisture content were the most significant parameters for cellulase activity. The optimum cellulase production was in the temperature range of 25-30 degrees C and moisture content between 55% and 70%. After the optimization, the FPA in T. reesei MCG77 was increased by 2.5 folds compared to that of T. reesei QM9414. 相似文献
26.
27.
Farah Idali Jan Wahlstr?m Benita Dahlberg Mohsen Khademi Tomas Olsson Anders Eklund Johan Grunewald 《Respiratory research》2009,10(1):42
Background
Activated T helper (Th)-1 pulmonary CD4+ cells and their mediators are essential for the inflammation and granulomatous process in sarcoidosis. Recently, T-cell immunoglobulin and mucin domain (TIM) molecules were suggested to be important regulators of immune function. In this study, we wanted to investigate whether TIM molecules could play a role in sarcoidosis.Methods
We used real-time polymerase chain reaction to investigate the differential gene expression of TIM-1 and TIM-3 as well as a few Th1 and Th2 cytokines (IL-2, IFN-γ, IL-4, IL-5 and IL-13) in CD4+ T cells isolated from bronchoalveolar lavage fluid (BALF) of patients (n = 28) and healthy controls (n = 8). Using flow cytometry, we were also able to analyse TIM-3 protein expression in 10 patients and 6 healthy controls.Results
A decreased TIM-3 mRNA (p < 0.05) and protein (p < 0.05) expression was observed in patients, and the level of TIM-3 mRNA correlated negatively with the CD4/CD8 T cell ratio in BALF cells of patients. Compared to a distinct subgroup of patients i.e. those with Löfgren''s syndrome, BALF CD4+ T cells from non- Löfgren''s patients expressed decreased mRNA levels of TIM-1 (p < 0.05). mRNA expression of IL-2 was increased in patients (p < 0.01) and non-Löfgren''s patients expressed significantly higher levels of IFN-γ mRNA (p < 0.05) versus patients with Löfgren''s syndrome.Conclusion
These findings are the first data on the expression of TIM-1 and TIM-3 molecules in sarcoidosis. The reduced TIM-3 expression in the lungs of patients may result in a defective T cell ability to control the Th1 immune response and could thus contribute to the pathogenesis of sarcoidosis. The down-regulated TIM-1 expression in non-Löfgren''spatients is in agreement with an exaggerated Th1 response in these patients. 相似文献28.
29.
Miroslav Bobek Pittaya Tuntiwachwuttikul M. Mohsen Ismail Thomas J. Bardos 《Nucleosides, nucleotides & nucleic acids》2013,32(8):1657-1665
Abstract N-Aminopyrazine analogues of cytidine and 2′-deoxycytidine were prepared from 1-(β-D-ribofuranosyl)-1,2-dihydro-2-oxopyrazine and 1-(2-deoxy-β-D-ribofuranosyl)-1,2-dihydro-2-oxopyrazine, respectively, by amination with O-mesitylenesulfonylhydroxylamine. 相似文献
30.
Safaei Mohsen Mobini Gholam-Reza Abiri Ardavan Shojaeian Ali 《Molecular biology reports》2020,47(8):6207-6216
Molecular Biology Reports - Synthetic biology breakthroughs have facilitated genetic circuit engineering to program cells through novel biological functions, dynamic gene expressions, as well as... 相似文献