全文获取类型
收费全文 | 8867篇 |
免费 | 370篇 |
国内免费 | 591篇 |
专业分类
林业 | 226篇 |
农学 | 1136篇 |
基础科学 | 442篇 |
988篇 | |
综合类 | 3860篇 |
农作物 | 1153篇 |
水产渔业 | 70篇 |
畜牧兽医 | 687篇 |
园艺 | 432篇 |
植物保护 | 834篇 |
出版年
2024年 | 51篇 |
2023年 | 189篇 |
2022年 | 293篇 |
2021年 | 359篇 |
2020年 | 368篇 |
2019年 | 377篇 |
2018年 | 270篇 |
2017年 | 386篇 |
2016年 | 452篇 |
2015年 | 364篇 |
2014年 | 556篇 |
2013年 | 552篇 |
2012年 | 769篇 |
2011年 | 712篇 |
2010年 | 558篇 |
2009年 | 487篇 |
2008年 | 382篇 |
2007年 | 357篇 |
2006年 | 335篇 |
2005年 | 282篇 |
2004年 | 206篇 |
2003年 | 172篇 |
2002年 | 142篇 |
2001年 | 168篇 |
2000年 | 134篇 |
1999年 | 108篇 |
1998年 | 98篇 |
1997年 | 87篇 |
1996年 | 69篇 |
1995年 | 84篇 |
1994年 | 56篇 |
1993年 | 42篇 |
1992年 | 68篇 |
1991年 | 53篇 |
1990年 | 42篇 |
1989年 | 34篇 |
1988年 | 32篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1978年 | 9篇 |
1977年 | 17篇 |
1976年 | 3篇 |
1962年 | 11篇 |
1955年 | 3篇 |
排序方式: 共有9828条查询结果,搜索用时 31 毫秒
11.
12.
13.
Physiological Indices and Selection of Methods on Rapid Identification for Sweet Potato Drought Resistance 总被引:1,自引:0,他引:1
ZHANG Ming-sheng TAN Feng ZHANG Qi-tang YANG Yong-hua 《中国农业科学(英文版)》2005,4(11):826-832
The relationships between the changes of relative water content (RWC), malondialdehyde (MDA) contents, superoxide dismutase (SOD) activity and free proline contents in sweet potato leaves, and drought resistant ability under different concentration of polyethylene glycol (PEG) treatment applied at rhizosphere of sweet potato seedlings were studied. A highly positive correlation between RWC and drought resistance (r =0.783, P〈0.01), a highly negative correlation between MDA contents and drought resistance (r = -0.848, P〈0.01), a highly positive correlation between SOD activity and drought resistance (r = 0.777, P〈0.01) was observed. Free proline contents in leaves was not related obviously to the sweet potato drought resistance under 25% PEG treatment. The stronger the drought resistance of variety, the less decrease of RWC and increase of MDA contents, the more increase of SOD activity. By determining these physiological indices in sweet potato leaves under 25% PEG treatment, rapid identification of drought resistant ability of different varieties can be obtained in the lab. 相似文献
14.
Late blight, caused by Phytophthora infestans , is an ongoing threat to potato and tomato crop production worldwide and considerable fundamental and applied research is conducted with the long-term aim of improved disease control. Understanding the mechanisms, processes and rates of P. infestans evolution is an important factor in predicting the effectiveness and durability of new management practices. A range of phenotypic and genotypic tests has been applied to achieve this goal, but each has limitations and new methods are sought. Recent progress in P. infestans genomics is providing the raw data for such methods and new high-throughput codominant biomolecular markers are currently being developed that have tremendous potential in the study of P. infestans population biology, epidemiology, ecology, genetics and evolution. This paper reviews some key applications, recommends some changes in approach and reports on the status and potential of new and existing methods for probing P. infestans genetic diversity. 相似文献
15.
16.
17.
丁勇义 《林业机械与木工设备》2001,29(7):20-22
车间粉尘与湖湿空气是人造板热压机液压系统油液外界污染的主要原因,通过构筑封闭式泵房,增设辅助油箱,改变没箱底部结构,设置排污,排水装置,可有效降低人造板热压机液压系统油液污染,改善液压系统性能,提高压机工作效率。 相似文献
18.
薯类加工产业可持续发展的现实思考 总被引:1,自引:0,他引:1
就湖南省娄底市农饥部门致力于红薯加工机械与加工技术的研究开发和推广应用的实践,对如何推进特色产业的可持续发展做理性和现实思考。 相似文献
19.
L. J. Turkensteen 《European journal of plant pathology / European Foundation for Plant Pathology》1987,93(2):87-90
Samenvatting In het Instituut voor Plantenziektenkundig Onderzoek (IPO) te Wageningen wordt gangreen bij aardappel, veroorzaakt door de schimmelPhoma exigua var.foveata, onderscheiden van ander droogrot door aangetast weefsel uit te leggen op een semiselectief medium. Op dit medium wordt de vorming van kristallen van voor de schimmel kenmerkende anthrachinonen bevorderd. De gemakkelijk waar te nemen geelgroene kristallen in het medium wijzen op de aanwezigheid van de betrokken schimmel. Bij een van deze toetsen vormden zich tussen de zich ontwikkelende kolonies van de schimmel donkere lijnen. Deze lijnen verschilden van reeds eerder beschreven violette lijnen, die zich vormen tussen kolonies van de twee variëteitenexigua enfoveata vanP. exigua. Onderzoek aan 27 isolaten vanP. exigua var.foveata toonde aan dat er met betrekking tot de vorming van donkere lijnen 11 verschillende typenP. exigua var.foveata onderscheiden konden worden. Isolaten van deze typen vormden bij gepaarde groei op het selectieve medium donkere lijnen met andere typen, maar niet met isolaten van het zelfde type. Er bleek geen verband met het groeitype van de cultures noch met de vorming van het antibioticum E te bestaan. 相似文献
20.
N. J. M. Roozen J. W. L. Van Vuurde 《European journal of plant pathology / European Foundation for Plant Pathology》1991,97(5):321-334
Various compounds and basal media were tested for their suitability to create a semi-selective medium for isolation ofClavibacter michiganensis subsp.sepedonicus (Cms) from cattle manure slurry containing c. 108 colony forming units (cfu) per ml.Plating efficiency of Cms in yeast glucose mineral medium (YGM) was 104% compared with yeast peptone glucose medium. Nalidixic acid, polymyxin B sulphate and the experimental disinfectant S-0208 inhibited colony growth of cattle slurry bacteria as compared with Cms in YGM. The optimal concentration of these inhibitors in combination was determined by modified agar diffusion tests and by pour plating in 24-well tissue culture plates. The semi-selective medium YGMI consisted of YGM supplemented with nalidixic acid (2 mg/l), polymyxin B sulphate (30 mg/l) and S-0208 (125 mg/l). Plating efficiency varied for Cms between 50.9 and 69.6%, for cattle slurry bacteria between 1.8 and 2.5% and for saprophytes from potato heel end extracts between 11.5 and 27.4%.Differentiation of Cms colonies from other colonies was based on their small and bluish colony morphology in pour plates and on immunofluorescence colony-staining (IFC). IFC of a pure culture of micro colonies of Cms in YGM was possible after one day incubation (colonies c. 5 cells). Green background fluorescence in the agar gels was prevented by addition of Tween 20 (0.1%) to the washing buffer and the use of 1% agar gels. IFC of macro colonies of Cms in YGMI, visible with 4x objective magnification, was possible after 4 days. The detection level of the target organism in artificially inoculated cattle slurry in YGMI based on colony morphology varied between 1.4×103 and 2.3×104 cfu per ml of cattle slurry. Miniaturized plating combined with IFC, using wells in tissue culture plates (=16 mm), proved suitable for detection, but was c. 30 times les sensitive. The recovery of Cms was negatively correlated with the number of saprophytic colonies in the agar plates (R
2=0.74). 相似文献