收费全文 | 2374篇 |
免费 | 135篇 |
国内免费 | 1篇 |
2023年 | 18篇 |
2022年 | 36篇 |
2021年 | 77篇 |
2020年 | 39篇 |
2019年 | 52篇 |
2018年 | 84篇 |
2017年 | 55篇 |
2016年 | 80篇 |
2015年 | 104篇 |
2014年 | 146篇 |
2013年 | 186篇 |
2012年 | 178篇 |
2011年 | 178篇 |
2010年 | 126篇 |
2009年 | 94篇 |
2008年 | 115篇 |
2007年 | 135篇 |
2006年 | 96篇 |
2005年 | 93篇 |
2004年 | 66篇 |
2003年 | 64篇 |
2002年 | 54篇 |
2001年 | 28篇 |
2000年 | 27篇 |
1999年 | 20篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1992年 | 12篇 |
1991年 | 26篇 |
1990年 | 17篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 23篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1975年 | 13篇 |
1974年 | 6篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1971年 | 7篇 |
Iron deficiency anaemia is a major challenge among consumers in developing countries. Given the deficiency of iron in the diet, there is an urgent need to devise a strategy for providing the required iron in the daily diet to counter the iron deficiency anaemia. We propose that iron biofortification of wheat (Triticum aestivum L.) through seed priming would be an innovative strategy to address this issue. This investigation attempts to find the interaction of iron oxide nanoparticles on germination, growth parameters and accumulation of grain iron in two contrasting wheat genotypes WL711 (low-iron genotype) and IITR26 (high-iron genotype). Wheat seeds were primed with different concentrations of iron oxide nanoparticles in the range of 25–600 ppm, resulting in differential accumulation of grain iron contents. We observed a pronounced increase in germination percentage and shoot length at 400 and 200 ppm treatment concentrations in IITR26 and WL711 genotypes, respectively. Intriguingly, the treatment concentration of 25 ppm demonstrated higher accumulation with a significant increase in grain iron contents to 45.7% in IITR26 and 26.8% in WL711 genotypes, respectively. Seed priming represents an innovative and user-friendly approach for wheat biofortification which triggers iron acquisition and accumulation in grains.
相似文献We evaluated the effect of different watering regimes on the growth, chlorophyll fluorescence, phytohormones, and phenolic acids in Ceratotheca triloba (Bernh.) Hook.f., a commonly consumed African indigenous leafy vegetable. The study was conducted in the greenhouse under different watering regimes [seven (daily); three (thrice); two (twice); one (once) day(s) per week] for a period of 2 and 4-months. In each pot (7.5 cm diameter; 150 ml volume), 50 ml of water was applied per treatment. At the end of the experiment, plant growth, chlorophyll fluorescence, phytohormones, and phenolic acids were determined. A decrease in water availability resulted in a consistent decline in plant growth after a 4-month growth period. The severity of reduced water availability was more noticeable in plants watered once a week with a 1.4-fold reduction in growth and quantum efficiency of PSII (Fv/Fm) value of 0.80. The significant decline in growth and chlorophyll fluorescence was probably due to the increased production of abscisic acid (ABA) and cytokinin (CK) content together with the detected phytohormones in plants with restricted water supply. Furthermore, plants watered once a week had a trade-off between growth and phenolic acid production, with significantly higher (threefolds) concentrations of vanillic, ferulic, caffeic, and 4-coumaric acids in 4-month-old plants. Even though C. triloba grew best in well-watered soil, the plant had the potential to adapt and survive in soils with limited water supply for longer periods of growth. These findings suggest that regulation of phytohormones and phenolic acids played an important role in improving the growth of C. triloba under limited water conditions.
相似文献Soil salinity is a major limiting factor for crop productivity worldwide and is continuously increasing owing to climate change. A wide range of studies and practices have been performed to induce salt tolerance mechanisms in plants, but their result in crop improvement has been limited due to lack of time and money. In the current scenario, there is increasing attention towards habitat-imposed plant stress tolerance driven by plant-associated microbes, either rhizospheric and/or endophytic. These microbes play a key role in protecting plants against various environmental stresses. Therefore, the use of plant growth-promoting microbes in agriculture is a low-cost and eco-friendly technology to enhance crop productivity in saline areas. In the present review, the authors describe the functionality of endophytic bacteria and their modes of action to enhance salinity tolerance in plants, with special reference to osmotic and ionic stress management. There is concrete evidence that endophytic bacteria serve host functions, such as improving osmolytes, anti-oxidant and phytohormonal signaling and enhancing plant nutrient uptake efficiency. More research on endophytes has enabled us to gain insights into the mechanism of colonization and their interactions with plants. With this information in mind, the authors tried to solve the following questions: (1) how do benign endophytes ameliorate salt stress in plants? (2) What type of physiological changes incur in plants under salt stress conditions? And (3), what type of determinants produced by endophytes will be helpful in plant growth promotion under salt stress?
相似文献