全文获取类型
收费全文 | 3108篇 |
免费 | 208篇 |
国内免费 | 199篇 |
专业分类
林业 | 215篇 |
农学 | 304篇 |
基础科学 | 4篇 |
220篇 | |
综合类 | 1207篇 |
农作物 | 311篇 |
水产渔业 | 341篇 |
畜牧兽医 | 150篇 |
园艺 | 102篇 |
植物保护 | 661篇 |
出版年
2024年 | 9篇 |
2023年 | 38篇 |
2022年 | 58篇 |
2021年 | 91篇 |
2020年 | 72篇 |
2019年 | 64篇 |
2018年 | 77篇 |
2017年 | 96篇 |
2016年 | 137篇 |
2015年 | 125篇 |
2014年 | 142篇 |
2013年 | 170篇 |
2012年 | 219篇 |
2011年 | 204篇 |
2010年 | 178篇 |
2009年 | 197篇 |
2008年 | 159篇 |
2007年 | 156篇 |
2006年 | 148篇 |
2005年 | 135篇 |
2004年 | 109篇 |
2003年 | 84篇 |
2002年 | 66篇 |
2001年 | 87篇 |
2000年 | 67篇 |
1999年 | 44篇 |
1998年 | 49篇 |
1997年 | 46篇 |
1996年 | 43篇 |
1995年 | 59篇 |
1994年 | 54篇 |
1993年 | 42篇 |
1992年 | 53篇 |
1991年 | 39篇 |
1990年 | 41篇 |
1989年 | 50篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1962年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有3515条查询结果,搜索用时 156 毫秒
1.
小球藻( Chlorella )是一种单细胞真核藻类,属绿藻门、绿藻纲、绿球藻目、小球藻科、小球藻属 [1] 。作为最早开发的真核微藻之一,具有高营养价值、生长快速、结构简单、易工业化集成等显著优点。其细胞形态为球形或椭圆形,直径3~12 μm,呈单生或聚集成群状生长 [2] ,分布广泛,多见于淡水、咸水和土壤中。作为地球上最早的生命之一,小球藻基因比较稳定,至今未见有关其基因自发突变的报道。因其富含蛋白质、脂质、维生素、活性代谢产物等多种营养物质而被公认为具有高附加值和医疗保健作用,已经被广泛应用于保健食品 [3] 、水产养殖 [4] 、生物能源 [5] 等方面,关于小球藻生物技术的研究主要集中在基因组学 [6] 、分子遗传学 [7] 、代谢机理 [8] 、大规模培养 [9] 等方向。 相似文献
2.
3.
Elena V. Girich Anton N. Yurchenko Olga F. Smetanina Phan Thi Hoai Trinh Ngo Thi Duy Ngoc Mikhail V. Pivkin Roman S. Popov Evgeny A. Pislyagin Ekaterina S. Menchinskaya Ekaterina A. Chingizova Shamil S. Afiyatullov Ekaterina A. Yurchenko 《Marine drugs》2020,18(12)
Low molecular weight secondary metabolites of marine fungi Aspergillus flocculosus, Aspergillus terreus and Penicillium sp. from Van Phong and Nha Trang Bays (Vietnam) were studied and a number of polyketides, bis-indole quinones and terpenoids were isolated. The structures of the isolated compounds were determined by 1D and 2D NMR and HR-ESI-MS techniques. Stereochemistry of some compounds was established based on ECD data. A chemical structure of asterriquinone F (6) was thoroughly described for the first time. Anthraquinone (13) was firstly obtained from a natural source. Neuroprotective influences of the isolated compounds against 6-OHDA, paraquat and rotenone toxicity were investigated. 4-Hydroxyscytalone (1), 4-hydroxy-6-dehydroxyscytalone (2) and demethylcitreoviranol (3) have shown significant increasing of paraquat- and rotenone-treated Neuro-2a cell viability and anti-ROS activity. 相似文献
4.
Ting Shi Yan-Yan Yu Jia-Jia Dai Yi-Ting Zhang Wen-Peng Hu Li Zheng Da-Yong Shi 《Marine drugs》2021,19(3)
The species Pseudogymnoascus is known as a psychrophilic pathogenic fungus with a ubiquitous distribution in Antarctica. Meanwhile, the study of its secondary metabolites is infrequent. Systematic research of the metabolites of the fungus Pseudogymnoascus sp. HSX2#-11, guided by the method of molecular networking, led to the isolation of one novel polyketide, pseudophenone A (1), along with six known analogs (2–7). The structure of the new compound was elucidated by extensive spectroscopic investigation and single-crystal X-ray diffraction. Pseudophenone A (1) is a dimer of diphenyl ketone and diphenyl ether, and there is only one analog of 1 to the best of our knowledge. Compounds 1 and 2 exhibited antibacterial activities against a panel of strains. This is the first time to use molecular networking to study the metabolic profiles of Antarctica fungi. 相似文献
5.
大枫子与马钱上的叶斑类真菌病害 总被引:1,自引:1,他引:0
报道1986~1989年在泰国大枫子、海南大枫子和印度马钱上发现的9种叶斑类真菌病害的症状、病原菌及病情、分布。9种病原菌中,大枫子褐斑病菌(Ascochyta hydnocarpi S.M.Lin et P.K.Chi)、马钱叶枯病菌(Didymosphaeria strychnoris S.M.Lin et P.K.Chi)、马钱叶斑病菌(Microsphaeropsis strychoris S.M.Lin et P.K.Chi)和马钱轮纹褐斑病菌(Mycosphaerella strychnoris S.M.Lin et P.K.Cki)是新种。 相似文献
6.
地膜覆盖对棉枯萎病发生的影响 总被引:1,自引:0,他引:1
地膜覆盖显著降低了棉花枯萎病的发病率与病情指数,极显著地提高了棉花的产量。 相似文献
7.
中国家蚕微粒子虫及其近缘种的考察 总被引:2,自引:0,他引:2
本文描述了我国寄生于家蚕及二点螟的微粒子虫光学显微镜和电子显微镜形态及其对多种昆虫的致病性。后者极似家蚕微粒子虫,但在超微构造和致病性上有明显区别,定为新种。 相似文献
8.
M. Özgen 《Journal of Agronomy and Crop Science》1991,166(5):318-325
The purpose of this study was to compare responsiveness to environment as well as the stability of newly developed promising lines with traditional commercial cultivars. Subject research was conducted in Ankara between 1983-1989 on common and durum wheat cultivars and lines. Regression coefficient (b) was used as the criterion of genotypes' responsiveness to environment whereas deviation from regression (S2 d) and coefficient of determination (r2 ) were used as stability parameters. Each experiment year was regarded as an environment and yield average of each year was used as the environmental index.
In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological regions. 相似文献
In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological regions. 相似文献
9.
[目的]研究杜梨瘿螨在杜梨树上的自然发生规律,并观察评估杜梨瘿螨对其他果树、蔬菜为害的可能性。[方法]野外调查结合室内观察了解杜梨瘿螨在杜梨树上的自然发生规律 室内人工接虫饲育观察杜梨瘿螨对其他多种果树、蔬菜为害的可能性。[结果]基本摸清了杜梨瘿螨在杜梨树上的自然发生规律,杜梨瘿螨在承德一年发生2代,以成螨于杜梨芽鳞内越冬,春季4月中旬在杜梨树初展叶时,越冬螨虫开始出蛰活动 7月下旬叶面上的虫瘿数达到最高峰,8月上旬后螨虫开始蛰伏越冬。接虫饲育试验表明,杜梨瘿螨仅在桃、山楂叶片上能存活较长时间,但不能形成虫瘿,在所有的供试果树和蔬菜上均不能最终成活。[结论]杜梨瘿螨活动为害期集中在4~7月,具有生态脆弱性,属单食性害虫,只能在杜梨树上形成虫瘿,对供试的多种植物不构成危害。 相似文献
10.