全文获取类型
收费全文 | 5751篇 |
免费 | 315篇 |
国内免费 | 4篇 |
专业分类
林业 | 288篇 |
农学 | 288篇 |
基础科学 | 11篇 |
1058篇 | |
综合类 | 639篇 |
农作物 | 672篇 |
水产渔业 | 444篇 |
畜牧兽医 | 2227篇 |
园艺 | 83篇 |
植物保护 | 360篇 |
出版年
2023年 | 29篇 |
2022年 | 92篇 |
2021年 | 128篇 |
2020年 | 101篇 |
2019年 | 112篇 |
2018年 | 144篇 |
2017年 | 169篇 |
2016年 | 193篇 |
2015年 | 176篇 |
2014年 | 212篇 |
2013年 | 309篇 |
2012年 | 366篇 |
2011年 | 441篇 |
2010年 | 242篇 |
2009年 | 231篇 |
2008年 | 341篇 |
2007年 | 315篇 |
2006年 | 288篇 |
2005年 | 269篇 |
2004年 | 256篇 |
2003年 | 203篇 |
2002年 | 208篇 |
2001年 | 161篇 |
2000年 | 136篇 |
1999年 | 85篇 |
1998年 | 35篇 |
1997年 | 20篇 |
1996年 | 25篇 |
1995年 | 32篇 |
1994年 | 16篇 |
1993年 | 23篇 |
1992年 | 35篇 |
1991年 | 34篇 |
1990年 | 38篇 |
1989年 | 42篇 |
1988年 | 38篇 |
1987年 | 47篇 |
1986年 | 22篇 |
1985年 | 36篇 |
1984年 | 30篇 |
1983年 | 29篇 |
1981年 | 25篇 |
1980年 | 16篇 |
1978年 | 24篇 |
1977年 | 21篇 |
1976年 | 29篇 |
1974年 | 21篇 |
1973年 | 23篇 |
1972年 | 23篇 |
1971年 | 16篇 |
排序方式: 共有6070条查询结果,搜索用时 15 毫秒
1.
2.
3.
P. D. de Jong 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(3):293-295
Based on a simple model, the possible effects of certification of planting material on the occurrence of leek rust in a region can be derived from information on the proportion of infected fields (v) and the proportion of newly planted fields with infected planting material (i) in that region. Ifv i, certification of planting material will be highly effective. 相似文献
4.
5.
The in vitro metabolism of the chiral isomers of fonofos and fonofos oxon in the presence of mouse liver mixed-function oxidase and serum esterase was investigated. The metabolism of 35S-labeled phenyl-(S)P-fonofos mediated by mixed-function oxidase took place stereoselectively, resulting predominantly in (R)P-fonofos oxon. Similarly, (R)P-fonofos was converted to (S)P-oxon. In each case, however, a significant amount of racemization occurred. Other products were diphenyl disulfide and diphenyl disulfide oxide. In addition to stereospecificity, the oxidative metabolism of (R)P-fonofos proceeded at a rate faster than that of (S)P-fonofos. Stereoselective rate differences also were observed in mouse or rat serum-catalzyed degradation of the fonofos oxon enantiomers, the (S)P isomer being degraded about twofold faster than its enantiomer. The differences in toxicities of the isomers of fonofos and fonofos oxon were consistent with the in vitro metabolism data. 相似文献
6.
The knowledge of the biochemical mode of action of 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea (diflubenzuron) is presented, explaining the insecticidal effect. Like its structural analog, 1-(2,6-dichlorobenzyl)-3-(3,4-dichlorophenyl)urea (Du 19111), it inhibits chitin synthesis in the cuticle of larvae. Virtually complete inhibition was demonstrable 15 min after the application of diflubenzuron. Neither diflubenzuron nor Du 19111 has any effect upon chitinase activity either in vivo or in vitro. The insecticidal effect upon the cuticle, therefore, must be explained as an inhibition of chitin synthesis and not as an activation of chitin degradation. In contrast to the action of Du 19111, no accumulation of N-acetylglucosamine occurs upon treatment of larvae with diflubenzuron. Similarities and differences in the mode of action of both compounds are discussed, together with other effects reported in the literature. 相似文献
7.
8.
Hyun-Soo Kim Jun-Geon Je Hyesuck An Kyunghwa Baek Jeong Min Lee Mi-Jin Yim Seok-Chun Ko Ji-Yul Kim Gun-Woo Oh Min-Cheol Kang Young Min Ham You-Jin Jeon Dae-Sung Lee 《Marine drugs》2022,20(8)
Ecklonia maxima is a brown seaweed, which is abundantly distributed in South Africa. This study investigated an efficient approach using high-performance centrifugal partition chromatography (HPCPC), which has been successfully developed for the isolation and purification of phlorotannins, eckmaxol, and dieckol from the ethyl acetate fraction of E. maxima (EEM). We evaluated EEM for its inhibitory effect against lipopolysaccharide (LPS)-induced inflammatory responses in zebrafish embryos. The separation of eckmaxol and dieckol from samples of EEM using HPCPC was found to be of high purity and yield under an optimal solvent system composed of n-hexane:ethyl acetate:methanol:water (2:7:3:7, v/v/v/v). To evaluate the anti-inflammatory efficacy of EEM containing active compounds, zebrafish embryos exposed to LPS were compared with and without EEM treatment for nitric oxide (NO) production, reactive oxygen species (ROS) generation, and cell death two days after fertilization. These evaluations indicate that EEM alleviated inflammation by inhibiting cell death, ROS, and NO generation induced by LPS treatment. According to these results, eckmaxol and dieckol isolated from brown seaweed E. maxima could be considered effective anti-inflammatory agents as pharmaceutical and functional food ingredients. 相似文献
9.
A chemical investigation of a methanol extract of Spongia sp., a marine sponge collected from the Philippines, identified 12 unreported scalarane-type alkaloids—scalimides A–L (1–12)—together with two previously described scalarin derivatives. The elucidation of the structure of the scalaranes based on the interpretation of their NMR and HRMS data revealed that 1–12 featured a β-alanine-substituted E-ring but differed from each other through variations in their oxidation states and substitutions occurring at C16, C24, and C25. Evaluation of the antimicrobial activity of 1–12 against several Gram-positive and Gram-negative bacteria showed that 10 and 11 were active against Micrococcus luteus and Bacillus subtilis, respectively, with MIC values ranging from 4 to 16 μg/mL. 相似文献
10.