收费全文 | 2838篇 |
免费 | 247篇 |
国内免费 | 2篇 |
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 40篇 |
2021年 | 87篇 |
2020年 | 46篇 |
2019年 | 67篇 |
2018年 | 79篇 |
2017年 | 89篇 |
2016年 | 94篇 |
2015年 | 159篇 |
2014年 | 159篇 |
2013年 | 220篇 |
2012年 | 202篇 |
2011年 | 219篇 |
2010年 | 136篇 |
2009年 | 130篇 |
2008年 | 181篇 |
2007年 | 214篇 |
2006年 | 187篇 |
2005年 | 161篇 |
2004年 | 163篇 |
2003年 | 119篇 |
2002年 | 136篇 |
2001年 | 19篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 25篇 |
1997年 | 19篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1964年 | 1篇 |
In 2016, an outbreak of anthrax killing thousands of reindeer and affecting dozens of humans occurred on the Yamal peninsula, Northwest Siberia, after 70 years of epidemiological situation without outbreaks. The trigger of the outbreak has been ascribed to the activation of spores due to permafrost thaw that was accelerated during the summer heat wave. The focus of our study is on the dynamics of local environmental factors in connection with the observed anthrax revival. We show that permafrost was thawing rapidly for already 6 years before the outbreak. During 2011–2016, relatively warm years were followed by cold years with a thick snow cover, preventing freezing of the soil. Furthermore, the spread of anthrax was likely intensified by an extremely dry summer of 2016. Concurrent with the long-term decreasing trend in the regional annual precipitation, the rainfall in July 2016 was less than 10% of its 30-year mean value. We conclude that epidemiological situation of anthrax in the previously contaminated Arctic regions requires monitoring of climatic factors such as warming and precipitation extremes.
相似文献The remarkable properties of pristine B3O3 nanosheet as a nanocarrier for adsorption and desorption of TEPA anticancer drug for designing potential drug delivery platform were investigated using periodic DFT calculations. We studied the adsorption energy of all stable complexes formed between the drug molecule and B3O3 in gas and aqueous phases along with electronic structure analysis of complexes. Different adsorption configurations were studied for drug/B3O3 complexes, including the interaction of the C atom of the triangular ring, O atom in the TEPA drug with the B atom in B3O3, and indirect drug interaction the middle of the R1 ring cavity of the B3O3 nanosheet. The take-up of TEPA prompts a substantial change of 68.13% in the band gap (Eg) of the B3O3 nanosheet in the most stable complex. The present study results affirmed the application of B3O3 nanosheet as a potential vehicle for TEPA drugs in the treatment of cancerous tissues.
相似文献