全文获取类型
收费全文 | 1183篇 |
免费 | 63篇 |
国内免费 | 2篇 |
专业分类
林业 | 135篇 |
农学 | 88篇 |
基础科学 | 15篇 |
291篇 | |
综合类 | 85篇 |
农作物 | 103篇 |
水产渔业 | 91篇 |
畜牧兽医 | 306篇 |
园艺 | 18篇 |
植物保护 | 116篇 |
出版年
2023年 | 8篇 |
2022年 | 28篇 |
2021年 | 34篇 |
2020年 | 36篇 |
2019年 | 34篇 |
2018年 | 46篇 |
2017年 | 53篇 |
2016年 | 42篇 |
2015年 | 29篇 |
2014年 | 47篇 |
2013年 | 111篇 |
2012年 | 69篇 |
2011年 | 77篇 |
2010年 | 62篇 |
2009年 | 52篇 |
2008年 | 56篇 |
2007年 | 24篇 |
2006年 | 40篇 |
2005年 | 24篇 |
2004年 | 24篇 |
2003年 | 33篇 |
2002年 | 32篇 |
2001年 | 35篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 4篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1973年 | 9篇 |
1972年 | 4篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 7篇 |
排序方式: 共有1248条查询结果,搜索用时 46 毫秒
81.
Shahbaz Khan Hafeez ur Rehman Muhammad Ashfaq Wahid Muhammad Farrukh Saleem Mumtaz Akhtar Cheema Shahzad Maqsood Ahmed Basra 《Journal of plant nutrition》2016,39(12):1681-1687
The impact of soil (1, 2 kg ha?1) and foliar (100, 200 mg L?1) boron (B) with control (no B) was evaluated on phenology and yield formation of Camelina each applied at stem elongation and flowering stages. Foliar (200 mg L?1) or soil B (2 kg ha?1) resulted in earlier flowering and maturity, increased fruit bearing branches (19.68%), number of siliqua, seeds per siliqua (4.6%), biological yield (15%), seed yield (24%), harvest index (11.4%) and oil contents (23%) than no B. Increased fruit bearing branches, seed filled siliqua or seed numbers, harvest index and oil quality can be attributed to changes in dry matter accumulated of stem with simultaneous increase in siliqua dry weight with foliar or soil applied B. In crux, foliar (200 mg L?1) or soil applied (2 kg ha?1) B seems promising to improve seed and oil yield, harvest index of Camelina sativa under B deficient condition. 相似文献
82.
M. Shahadat Hossain Khan Tadao Wagatsuma Afrin Akhter Idupulapati M. Rao 《Journal of plant nutrition》2015,38(13):1973-1983
Nutrient deficiencies are often an additional growth-limiting factor in tropical acid soils. Considering the potential interactions between Al stress and low-nutrient stress, differences among rice cultivars for Al tolerance, low-nutrient tolerance, and combined stress tolerance were investigated. The main objective of this study was to identify the predominant growth-limiting factor in tropical acid soils. Tolerance to low nutrient stress and combined stress did not show any relationship with aluminum (Al) tolerance indicating that these stress factors act independently. Al-tolerant cv. Rikuu-132 was tolerant to combined stress. Conversely, highly Al-sensitive cv. BR34 was most tolerant to combined and low nutrient stress. Combined stress tolerance of shoot was positively correlated with calcium (Ca) content of shoot. The results indicate that Al tolerance alone is not adequate for superior performance on most acid soils. Tolerance to combined stress factors would be needed to improve productivity of rice on low fertility acid soils. 相似文献
83.
84.
85.
86.
Cytokinins: permissive role in seed germination 总被引:14,自引:0,他引:14
A A Khan 《Science (New York, N.Y.)》1971,171(974):853-859
87.
Coleman JN Lotya M O'Neill A Bergin SD King PJ Khan U Young K Gaucher A De S Smith RJ Shvets IV Arora SK Stanton G Kim HY Lee K Kim GT Duesberg GS Hallam T Boland JJ Wang JJ Donegan JF Grunlan JC Moriarty G Shmeliov A Nicholls RJ Perkins JM Grieveson EM Theuwissen K McComb DW Nellist PD Nicolosi V 《Science (New York, N.Y.)》2011,331(6017):568-571
If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS(2) and MoS(2) effectively reinforce polymers, whereas WS(2)/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties. 相似文献
88.
Antiarthritic gold compounds effectively quench electronically excited singlet oxygen 总被引:5,自引:0,他引:5
Although certain gold [Au(I)] compounds have been used effectively in the treatment of rheumatoid arthritis for some years, the molecular basis for such therapeutic action has been unclear. One possible mechanism of the action of Au(I) compounds is that they protect unsaturated membrane lipids and proteins against oxidative degradation caused by activated phagocytes that are not properly regulated. In this study it has been shown that superoxide ion (O-2.), a product of activated phagocytes, can be oxidized to electronically excited singlet oxygen (O1(2)delta g), an agent that is capable of peroxidation of unsaturated fatty acid derivatives. It has also been shown that antiarthritic Au(I) compounds are effective deactivators of O1(2)delta g with quenching constants on the order of 10(7) M-1 sec-1. 相似文献
89.
Human muscle phosphoglycerate mutase deficiency: newly discovered metabolic myopathy 总被引:7,自引:0,他引:7
Muscle phosphoglycerate mutase activity was decreased (5.7 percent of the lowest control value) in a 52-year-old man with intolerance for strenuous exercise and recurrent pigmenturia since adolescence. All of the other enzymes of glycolysis had normal activities, and glycogen concentration was normal. Electrophoretic, heat lability, and mercury inhibition studies showed that the small residual activity in the patient's muscle was represented by the brain (BB) isoenzyme of phosphoglycerate mutase, suggesting a genetic defect of the M subunit which predominates in normal muscle. The prevalence of the BB isoenzyme in other tissues, including muscle culture, may explain why symptoms were confined to muscle. 相似文献
90.
Du J Zhou Y Su X Yu JJ Khan S Jiang H Kim J Woo J Kim JH Choi BH He B Chen W Zhang S Cerione RA Auwerx J Hao Q Lin H 《Science (New York, N.Y.)》2011,334(6057):806-809
Silent information regulator 2 (Sir2) proteins (sirtuins) are nicotinamide adenine dinucleotide-dependent deacetylases that regulate important biological processes. Mammals have seven sirtuins, Sirt1 to Sirt7. Four of them (Sirt4 to Sirt7) have no detectable or very weak deacetylase activity. We found that Sirt5 is an efficient protein lysine desuccinylase and demalonylase in vitro. The preference for succinyl and malonyl groups was explained by the presence of an arginine residue (Arg(105)) and tyrosine residue (Tyr(102)) in the acyl pocket of Sirt5. Several mammalian proteins were identified with mass spectrometry to have succinyl or malonyl lysine modifications. Deletion of Sirt5 in mice appeared to increase the level of succinylation on carbamoyl phosphate synthase 1, which is a known target of Sirt5. Thus, protein lysine succinylation may represent a posttranslational modification that can be reversed by Sirt5 in vivo. 相似文献