全文获取类型
收费全文 | 26687篇 |
免费 | 2208篇 |
国内免费 | 20篇 |
出版年
2023年 | 87篇 |
2022年 | 188篇 |
2021年 | 443篇 |
2020年 | 263篇 |
2019年 | 328篇 |
2018年 | 409篇 |
2017年 | 342篇 |
2016年 | 593篇 |
2015年 | 1023篇 |
2014年 | 1205篇 |
2013年 | 1437篇 |
2012年 | 1919篇 |
2011年 | 1942篇 |
2010年 | 1255篇 |
2009年 | 1081篇 |
2008年 | 1695篇 |
2007年 | 1747篇 |
2006年 | 1600篇 |
2005年 | 1558篇 |
2004年 | 1578篇 |
2003年 | 1513篇 |
2002年 | 1397篇 |
2001年 | 272篇 |
2000年 | 174篇 |
1999年 | 301篇 |
1998年 | 357篇 |
1997年 | 264篇 |
1996年 | 219篇 |
1995年 | 222篇 |
1994年 | 234篇 |
1993年 | 227篇 |
1992年 | 181篇 |
1991年 | 175篇 |
1990年 | 149篇 |
1989年 | 131篇 |
1988年 | 153篇 |
1987年 | 121篇 |
1986年 | 127篇 |
1985年 | 163篇 |
1984年 | 165篇 |
1983年 | 171篇 |
1982年 | 192篇 |
1981年 | 183篇 |
1980年 | 158篇 |
1979年 | 105篇 |
1978年 | 113篇 |
1977年 | 90篇 |
1976年 | 87篇 |
1975年 | 71篇 |
1974年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Subramanya Rao Yuki Chan Donnabella C. Bugler-Lacap Ashish Bhatnagar Monica Bhatnagar Stephen B. Pointing 《Indian journal of microbiology》2016,56(1):35-45
A culture-independent diversity assessment of archaea, bacteria and fungi in the Thar Desert in India was made. Six locations in Ajmer, Jaisalmer, Jaipur and Jodhupur included semi-arid soils, arid soils, arid sand dunes, plus arid cryptoendolithic substrates. A real-time quantitative PCR approach revealed that bacteria dominated soils and cryptoendoliths, whilst fungi dominated sand dunes. The archaea formed a minor component of all communities. Comparison of rRNA-defined community structure revealed that substrate and climate rather than location were the most parsimonious predictors. Sequence-based identification of 1240 phylotypes revealed that most taxa were common desert microorganisms. Semi-arid soils were dominated by actinobacteria and alpha proteobacteria, arid soils by chloroflexi and alpha proteobacteria, sand dunes by ascomycete fungi and cryptoendoliths by cyanobacteria. Climatic variables that best explained this distribution were mean annual rainfall and maximum annual temperature. Substrate variables that contributed most to observed diversity patterns were conductivity, soluble salts, Ca2+ and pH. This represents an important addition to the inventory of desert microbiota, novel insight into the abiotic drivers of community assembly, and the first report of biodiversity in a monsoon desert system. 相似文献
995.
996.
Stephen Summers Bruce C. Thomson Andrew S. Whiteley Charles S. Cockell 《Geomicrobiology journal》2016,33(1):52-62
The weathering of silicate in the world's critical-zone (rock-soil interface) is a natural mechanism providing a feedback on atmospheric CO2 concentrations through the carbonate-silicate cycle. We examined culturable bacterial communities from a critical-zone in western Iceland to determine the optimum growth temperature and their ability to solubilize phosphate-containing minerals, which are abundant within the critical-zone area examined here. The majority of isolated bacteria were able to solubilize mineral-state phosphate. Almost all bacterial isolates were mesophilic (growth optima of 20–45°C), despite critical-zone temperatures that were continuously below 15°C, although all isolates could grow at temperatures associated with the critical-zone (?2.8–13.1°C). Only three isolates were shown to have thermal optima for growth that were within temperatures experienced at the critical-zone. These findings show that the bacteria that inhabit the western Icelandic critical-zone have temperature growth optima suboptimally adapted to their environment, implying that other adaptations may be more important for their long-term persistance in this environment. Moreover, our study showed that the cold basaltic critical-zone is a region of active phosphate mineral-weathering. 相似文献
997.
Magnus Simonsson Mélanie Court Johan Bergholm Damien Lemarchand Stephen Hillier 《Biogeochemistry》2016,129(1-2):77-91
Clay minerals and K feldspars were evaluated as sources of K in a Norway spruce stand (Picea abies (L.) Karst.) from the Skogaby experimental forest in southwest Sweden. The soil, developed in a Quaternary glacial till, has only 3–5% clay, and more than 95% of its K resides in feldspars. Ratios of K/Rb were assessed in interlayers of 2:1 clay minerals (extracted with hot (100 °C) 2 M HCl), biomass and the forest floor. These compartments had similarly low K/Rb ratios, whereas K feldspars were significantly poorer in Rb. A fractionation model indicated preferential retention of Rb in the biomass and forest floor, due to stronger adsorption of Rb than K in the humus, as well as preferential uptake of K from the exchange complex in the mineral soil. Preferential uptake of K may result from weaker adsorption of K by the cation exchanger, or preference for dissolved K over Rb by the roots. A quantitative mineralogical analysis revealed that loss from micas may account for half of the Holocene loss of K from the soil, which was approximately 22 Mg ha?1. Exceptionally low K/Rb ratios in HCl extracts of the upper 60 cm of the profile indicated extensive loss of K from mica in the parent material and re-fixation of K and Rb at lower ratios. The results indicate that fixation in and release from clay minerals may be prominent in the cycling of K, even in a soil that is poor in clay minerals. 相似文献
998.
Mehbub Mohammad F. Tanner Jason E. Barnett Stephen J. Franco Christopher M. M. Zhang Wei 《Applied microbiology and biotechnology》2016,100(24):10609-10626
Applied Microbiology and Biotechnology - Sponge-associated bacteria play a critical role in sponge biology, metabolism and ecology, but how they interact with their host sponges and the role of... 相似文献
999.
1000.
Qu Wei-Min Huang Zhi-Li Mochizuki Takatoshi Eguchi Naomi Chen Jiang-Fan Schwarzschild Michael A. Fink Stephen J. Urade Yoshihiro Hayaishi Osamu 《Sleep and biological rhythms》2016,2(1):S55-S55
Sleep and Biological Rhythms - 相似文献