全文获取类型
收费全文 | 44760篇 |
免费 | 2109篇 |
国内免费 | 4728篇 |
专业分类
林业 | 2933篇 |
农学 | 4966篇 |
基础科学 | 795篇 |
5411篇 | |
综合类 | 20635篇 |
农作物 | 3637篇 |
水产渔业 | 3044篇 |
畜牧兽医 | 5782篇 |
园艺 | 1790篇 |
植物保护 | 2604篇 |
出版年
2024年 | 156篇 |
2023年 | 527篇 |
2022年 | 1087篇 |
2021年 | 1228篇 |
2020年 | 1305篇 |
2019年 | 1574篇 |
2018年 | 1126篇 |
2017年 | 1805篇 |
2016年 | 2312篇 |
2015年 | 1960篇 |
2014年 | 1597篇 |
2013年 | 2401篇 |
2012年 | 3401篇 |
2011年 | 3346篇 |
2010年 | 2673篇 |
2009年 | 2501篇 |
2008年 | 2737篇 |
2007年 | 3243篇 |
2006年 | 2977篇 |
2005年 | 2226篇 |
2004年 | 1801篇 |
2003年 | 1276篇 |
2002年 | 1008篇 |
2001年 | 926篇 |
2000年 | 867篇 |
1999年 | 709篇 |
1998年 | 567篇 |
1997年 | 527篇 |
1996年 | 490篇 |
1995年 | 487篇 |
1994年 | 427篇 |
1993年 | 434篇 |
1992年 | 402篇 |
1991年 | 365篇 |
1990年 | 311篇 |
1989年 | 229篇 |
1988年 | 191篇 |
1987年 | 114篇 |
1986年 | 108篇 |
1985年 | 52篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 5篇 |
1963年 | 6篇 |
1962年 | 10篇 |
1955年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
21.
This paper depicted the physiographic landscape features and natural vegetation situation of study area (the eastern Jilin
Province), and expatiates the definition, basic characters and its development of Ecological Land Classification (ELC). Based
on the combination of relief map, satellite photography for study area and vegetation inventory data of 480 sample sites,
a 5-class and a 15-class ecological land type map was concluded according to 4 important factors including slope, aspect,
vegetation and elevation. Ecological Classification System (ECS) is a method to identify, characterize, and map ecosystems.
The Ecological Land Type (ELT) was examined and applied initially in eastern Jilin Province.
Foundation item: This paper was supported by Chinese Academy of Sciences “100 people” project and the Open Research Station of Changbai Mountain
Forest Ecosystem.
Biography: XIAO Bao-ying (1974-), female, postgraduate in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016,
P. R. China
Responsible editor: Zhu Hong 相似文献
22.
本文报道广东南岭国家级自然保护区大东山管理站所辖林区广翅目1科2属2种,脉翅目3科8属10种,长翅目1科1属1种,鳞翅目(蛾类)27科213属299种的昆虫名录。 相似文献
23.
本文报道了江西三种危害食用菌的绿色霉菌的生物学特性。它们是:绿色木霉(Trichoderma Viride pers exFn)。产黄青霉(Penicillium Chrysoenum Thom)和构巢曲霉(Aspergillus nidulcms(Eidzm)Winter)。 相似文献
24.
25.
本文研究了吡喹酮和硝硫氰醚与日本血吸虫拟似神经递质 5-羟色胺间的关系。以吡喹酮 ( 5× 1 0 - 7mol/ L和 5× 1 0 - 8mol/ L )、硝硫氰醚 ( 1 0 - 4mol/ L和 1 0 - 5mol/ L )分别培养日本血吸虫成虫 4h和 8h ,反相离子对高效液相法测定其体内 5-HT的含量变化。结果显示 :吡喹酮和硝硫氰醚对日本血吸虫体内 5-HT等含量的影响与对照相比均无显著性差异。表明二者抗虫作用似不通过影响虫体 5-HT的生物合成和降解。 相似文献
26.
John W.PATRICK 《浙江大学学报(农业与生命科学版)》1990,(4)
The instablity of the stimulation of photosynthate unloading from seed coats of Phaseolus vulgaris by abscisic acid (ABA ) and benzylamino purine ( BAP ) was studied in terms of experimental conditions. ABA stimulated photosynthate unloading at pH 6 and pH 8 without close dependence upon pH. ABA at a concentration range of 10-5-10-4 mol/L displayed stimulatory effect. However, BAP revealed no effect at a concentration range of 10-6-10-4 mol/L. Experiments designed with different transport time of 14C-photosynthate indicated that ABA might act at the plasma membrane of the unloading cells. Reducing endogenous ABA level by diminishing leaf area did not facilitate the manifestation of exogenous ABA function. Potassium ion stimulated photosynthate unloading from seed coats with highest promotion at 100 mmol/L K . However, no dependence of ABA stimulation of photosynthate unloading on K was found. 相似文献
27.
28.
V. Slipevi I. Vedrina-Dragojevi L. Balint J. Momirovi-uljat 《Journal of Agronomy and Crop Science》1992,168(2):73-84
Dynamics of the cumulation of phosphorus, potassium, calcium and magnesium in developing seed of four soybean genotypes under the defined climatic conditions in the course of three years was observed. Samples were being taken at weekly intervals from the point at which the grain reached a size suitable to be analyzed up to the full maturity of the seed. By analyzing the results it was found out that the intense cumulation of the minerals tested took place during the stages III and IV of the seed development, that is, in the course of intense cumulation of dry matter and the most expressive metabolic activity in the seed. Investigation of the impact of climatic conditions provides evidence that cumulation of the tested macroelements has been favourably influenced by increased precipitation along with moderate air temperatures within the seed developing period. The highest content of the minerals found with the cultivar Maksimirka independently of the year investigated reveals that mineral cumulation in soybean seed is affected by the cultivar and genetic particularity. 相似文献
29.
纵带球须刺蛾是多种农林作物的害虫。在广州1年发生1~3代,以老熟幼虫在土中茧内越冬,幼虫一般为7~8龄,幼虫感染核多角体病毒后,常成为流行病,死亡率可达90%以上。进行防治试验表明,90%敌百虫晶体40000倍液、80%敌敌畏乳剂100000倍液和50%杀螟松乳剂100000倍液等,以及2.3×10~(5-7)浓度的核多角体病毒,均对幼虫有较好的毒杀效果。 相似文献
30.
表达序列标签(ESTs)及其应用 总被引:3,自引:0,他引:3
表达序列标签(ESTs)是指从(ESTcDNA文库中随机挑取克隆并对其3’或5’端进行单轮自动测序所获得的短cDNA库列,一般长度为300~500bp。要有效获取ESTs,必须对cDNA文库进行预处理,处理方法有衰减杂交法、均一化法和差异显示法。在dbEST中收录了大量各种生物的ESTs。ESTs广泛应用于鉴定基因、发现新基因、电子克隆、构建遗传学图谱、制备DNA芯片、分子标记、研究基因的差异表达及检验病原微生物等方面。 相似文献