全文获取类型
收费全文 | 1096篇 |
免费 | 89篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 43篇 |
2020年 | 27篇 |
2019年 | 27篇 |
2018年 | 33篇 |
2017年 | 39篇 |
2016年 | 49篇 |
2015年 | 54篇 |
2014年 | 63篇 |
2013年 | 103篇 |
2012年 | 79篇 |
2011年 | 83篇 |
2010年 | 49篇 |
2009年 | 33篇 |
2008年 | 54篇 |
2007年 | 34篇 |
2006年 | 47篇 |
2005年 | 49篇 |
2004年 | 36篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1995年 | 5篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1969年 | 6篇 |
1966年 | 4篇 |
排序方式: 共有1187条查询结果,搜索用时 484 毫秒
151.
Summary Relative efficiency of five chemical extractants for the extraction of available Zn in four different soils and its uptake by rice seedlings was studied in a pot culture experiment. The Zn extracted by dithizone-ammonium acetate showed a significant relationship with plant uptake whereas the values for other extractants except NH4OAc (pH4.8) did not approach the level of significance. Among the soil properties studied, pH and CaCO3 correlated negatively and organic matter and CEC positively with Zn uptake by rice plants.Contribution from the Soil Science and Agricultural Chemistry Dept., Banaras Hindu University, Varanasi-221005, India.Lecturer and Research Scholar of the Soil Science and Agricultural Chemistry Department, respectively.Lecturer and Research Scholar of the Soil Science and Agricultural Chemistry Department, respectively. 相似文献
152.
153.
154.
155.
156.
Activation of brain‐derived neurotrophic factor‐tropomyosin receptor kinase B signaling in the pedunculopontine tegmental nucleus: a novel mechanism for the homeostatic regulation of rapid eye movement sleep
下载免费PDF全文
![点击此处可从《Journal of neurochemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
157.
Sterol glycosyltransferases required for adaptation of Withania somnifera at high temperature
下载免费PDF全文
![点击此处可从《Physiologia plantarum》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gaurav Singh Manish Tiwari Surendra P. Singh Ruchi Singh Surendra Singh Pramod A. Shirke Prabodh K. Trivedi Pratibha Misra 《Physiologia plantarum》2017,160(3):297-311
Heat is a major environmental stress factor that confines growth, productivity, and metabolism of plants. Plants respond to such unfavorable conditions through changes in their physiological, biochemical and developmental processes. Withania somnifera, an important medicinal plant, grows in hot and dry conditions, however, molecular mechanisms related to such adaptive properties are not known. Here, we elucidated that members of the sterol glycosyltransferases (SGT) gene family play important roles in the survival of W. somnifera under adverse conditions through maintaining the integrity of the membrane. SGTs are enzymes involved in sterol modifications and participate in metabolic flexibility during stress. Silencing of WsSGT members, for instance WsSGTL1, WsSGTL2 and WsSGTL4, was inimical for important physiological parameters, such as electron transport rate, photochemical quantum yield, acceptor side limitation, non‐photochemical quenching (NPQ), Fv/Fm and net photosynthetic rate, whereas stomatal conductance, transpiration rate and dark respiration rates (Rds) were increased. Decreased NPQ and increased Rds helped to generate significant amount of ROS in the Wsamisgt lines. After heat stress, H2O2, lipid peroxidation and nitric oxide production increased in the Wsamisgt lines due to high ROS generation. The expression of HSPs in Wsamisgt lines might be involved in regulation of physiological processes during stress. We have also observed increased proline accumulation which might be involved in restricting water loss in the Wsamisgt lines. Taken together, our observations revealed that SGTL enzyme activity is required to maintain the internal damages of the cell against high temperature by maintaining the sterol vs sterol glycosides ratio in the membranes of W. somnifera. 相似文献
158.
Abhishek Kumar Tiwari Jitendra Prasad 《Biomechanics and modeling in mechanobiology》2017,16(2):395-410
Bone loss is a serious health problem. In vivo studies have found that mechanical stimulation may inhibit bone loss as elevated strain in bone induces osteogenesis, i.e. new bone formation. However, the exact relationship between mechanical environment and osteogenesis is less clear. Normal strain is considered as a prime stimulus of osteogenic activity; however, there are some instances in the literature where osteogenesis is observed in the vicinity of minimal normal strain, specifically near the neutral axis of bending in long bones. It suggests that osteogenesis may also be induced by other or secondary components of mechanical environment such as shear strain or canalicular fluid flow. As it is evident from the literature, shear strain and fluid flow can be potent stimuli of osteogenesis. This study presents a computational model to investigate the roles of these stimuli in bone adaptation. The model assumes that bone formation rate is roughly proportional to the normal, shear and fluid shear strain energy density above their osteogenic thresholds. In vivo osteogenesis due to cyclic cantilever bending of a murine tibia has been simulated. The model predicts results close to experimental findings when normal strain, and shear strain or fluid shear were combined. This study also gives a new perspective on the relation between osteogenic potential of micro-level fluid shear and that of macro-level bending shear. Attempts to establish such relations among the components of mechanical environment and corresponding osteogenesis may ultimately aid in the development of effective approaches to mitigating bone loss. 相似文献
159.
A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management. 相似文献
160.
Ghosh S Tiwari P Pandey S Misra AK Chaturvedi V Gaikwad A Bhatnagar S Sinha S 《Bioorganic & medicinal chemistry letters》2008,18(14):4002-4005
A series of glycosyl thioacetamide and glycosyl sulfonyl acetamide derivatives have been prepared following a convenient reaction protocol and evaluated for their antitubercular activity against Mycobacterium tuberculosis H37Rv. Amongst 32 compounds evaluated 3 compounds were effective in inhibiting mycobacterial growth at MIC of 6.25 μg/mL, 6 compounds at MIC of 3.125 μg/mL and 1 compound at MIC of 1.56 μg/mL. All active compounds were found nontoxic in Vero cell lines and mice bone marrow macrophages. 相似文献