全文获取类型
收费全文 | 43365篇 |
免费 | 1462篇 |
国内免费 | 2986篇 |
专业分类
林业 | 6373篇 |
农学 | 4874篇 |
基础科学 | 2478篇 |
6927篇 | |
综合类 | 9852篇 |
农作物 | 3647篇 |
水产渔业 | 3054篇 |
畜牧兽医 | 5016篇 |
园艺 | 2171篇 |
植物保护 | 3421篇 |
出版年
2024年 | 116篇 |
2023年 | 375篇 |
2022年 | 933篇 |
2021年 | 1223篇 |
2020年 | 1103篇 |
2019年 | 1097篇 |
2018年 | 3509篇 |
2017年 | 3817篇 |
2016年 | 2108篇 |
2015年 | 1362篇 |
2014年 | 1340篇 |
2013年 | 1588篇 |
2012年 | 2848篇 |
2011年 | 4005篇 |
2010年 | 4012篇 |
2009年 | 2977篇 |
2008年 | 2994篇 |
2007年 | 3138篇 |
2006年 | 1496篇 |
2005年 | 1284篇 |
2004年 | 725篇 |
2003年 | 666篇 |
2002年 | 501篇 |
2001年 | 398篇 |
2000年 | 502篇 |
1999年 | 527篇 |
1998年 | 448篇 |
1997年 | 346篇 |
1996年 | 338篇 |
1995年 | 325篇 |
1994年 | 234篇 |
1993年 | 244篇 |
1992年 | 203篇 |
1991年 | 143篇 |
1990年 | 140篇 |
1989年 | 152篇 |
1988年 | 124篇 |
1987年 | 70篇 |
1986年 | 80篇 |
1985年 | 76篇 |
1984年 | 53篇 |
1983年 | 54篇 |
1982年 | 42篇 |
1981年 | 34篇 |
1980年 | 23篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1968年 | 6篇 |
1966年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Bo?ena Bukowska Katarzyna GoszczyńskaWirgiliusz Duda 《Pesticide biochemistry and physiology》2003,77(3):92-98
The effects of exposure of human erythrocytes to different concentrations of 4-chloro-2-methylphenoxyacetic acid (MCPA) and its metabolite—2,4-dimethylphenol (2,4-DMP) were studied. The investigations concerned mainly the content of glutathione (GSH and GSSG), glutathione peroxidase (GSH-Px), glutathione transferase (GST), and the level of adenine energy charge (AEC). Reactive oxygen species (ROS) such as hydroxyl radical, superoxide anion, hydrogen peroxide, and nitric oxide are produced during normal processes in the cell. Under normal conditions, antioxidant systems of the cell minimize damage caused by ROS. When ROS generation increases to an extent that it overcomes the cellular antioxidant systems, the result is oxidative stress. We observed that MCPA and 2,4-DMP decreased the level of GSH in erythrocytes in comparison with control. MCPA did not affect glutathione peroxidase and glutathione transferase activity, while 2,4-DMP increased their activity. 2,4-DMP decreased the level of ATP and increased the content of ADP and AMP, leading to the fall of the level of AEC. MCPA and 2,4-DMP transform hemoglobin into methemoglobin, thus preventing oxygen transport. Comparison of the toxicity of MCPA and 2,4-DMP revealed that the most prominent changes occurred in human erythrocytes incubated with 2,4-DMP. 相似文献
133.
Eiji Tanaka Chihiro Tanaka Atsushi Ishihara Yasumasa Kuwahara Mitsuya Tsuda 《Journal of General Plant Pathology》2003,69(1):1-6
Aciculosporium take (Ascomycota; Clavicipitaceae) is a causal agent of witches' broom of
bamboo plants. The symptoms of this disease are believed to be induced by plant
hormones, particularly auxins. Indole-3-acetic acid (IAA) was identified in
cultures of this fungus in an l-tryptophan-supplemented liquid medium.
IAA production was confirmed on 30 isolates of A. take from various
hosts and locations at levels up to 1 mg/l. The biosynthetic pathway of
IAA in A. take culture was examined by analyzing intermediate products
and by feeding experiments. The results showed that the indole-3-pyruvic acid
pathway (l-tryptophan → indole-3-pyruvic acid → indole
acetaldehyde → IAA) was the dominant pathway in A. take.
Received: June 3, 2002 / Accepted: July 25, 2002 相似文献
134.
135.
Hiromitsu Furuya Tsutomu Matsumoto Shin-ichi Fuji Hideki Naito 《Journal of General Plant Pathology》2003,69(2):115-119
Rice seedling growth, estimated by plant height and root development and discoloration, was better in pasteurized soil than
in unpasteurized soil obtained from a flooded rice field. Rice seedlings also grew better in sterilized soil modified by adding
roots harvested from the pasteurized soil than in soil modified by adding roots harvested from the unpasteurized soil. The
results demonstrate that seedling growth in the rice field soil was inhibited by soil microorganisms, even though no typical
symptoms such as seedling blight or damping-off appeared. Pythium aristosporum is suggested to be involved in the inhibition. Thus, it appears that inconspicuous restraint of rice seedling growth could
occur in soils of rice paddy fields.
Received: May 20, 2002 / Accepted: October 16, 2002
Acknowledgments The authors thank Dr. T. Ichitani, former professor at Osaka Prefectural University, for providing an isolate of Pythium aristosporum for comparison, and Mr. Mitsuaki Sato of Akita Prefectural College of Agriculture for technical assistance. 相似文献
136.
137.
果梅幼树对春施~(15)N-硫铵的吸收与分配 总被引:5,自引:0,他引:5
以盆栽3年生细叶青梅/毛桃为试材,研究了早春施用~(15)N-(NH_4)_2SO_4条件下,果梅对~(15)N的吸收分配规律。结果表明:由于春季土温较低,限制了植株对肥料氮的利用率。在新梢旺长期,植株从肥料氮中吸收的氮素营养主要用于新生器官的建造,且新梢成为~(15)N的主要分配中心,其次即为果实,再其次为细根。至花芽分化期,植株的生长中心已发生转移和分散,但春施氮对促进当年生枝的花芽分化和维持叶片正常光合功能仍有重要作用,此期亦是根系生长的关键时期之一,且与贮氮相比,春施氮更有利于当年新根的萌发和根系的扩大。 相似文献
138.
139.
140.
苹果果实日灼人工诱导技术及阈值温度研究 总被引:10,自引:3,他引:10
使用自制的日灼诱导设备,在无风或微风的晴天对活体果实进行田间日灼诱导,通过改变诱导室内的气温来控制和调节果面温度,从而确定了不同苹果品种果实发生日灼的阈值温度。试验证明: 自制的诱导设备运行平稳,诱导期间可保持果温基本稳定,大多数情况下,处理期间果面平均温度与实际设定温度的差异小于0.12℃ ,温度变化幅度一般小于±0.5℃ 。本试验所测定的9个苹果品种日灼阈值温度为(45.9±0.5)℃ (48.5±0.5)℃。光照对日灼发生有重要影响,即使在同样的阈值温度下,有光的处理果实发生日灼,而无光的处理则不发生日灼。 相似文献