全文获取类型
收费全文 | 2514篇 |
免费 | 153篇 |
国内免费 | 131篇 |
专业分类
林业 | 124篇 |
农学 | 149篇 |
基础科学 | 112篇 |
165篇 | |
综合类 | 1169篇 |
农作物 | 109篇 |
水产渔业 | 8篇 |
畜牧兽医 | 57篇 |
园艺 | 59篇 |
植物保护 | 846篇 |
出版年
2024年 | 14篇 |
2023年 | 74篇 |
2022年 | 77篇 |
2021年 | 101篇 |
2020年 | 104篇 |
2019年 | 110篇 |
2018年 | 72篇 |
2017年 | 107篇 |
2016年 | 156篇 |
2015年 | 102篇 |
2014年 | 191篇 |
2013年 | 124篇 |
2012年 | 192篇 |
2011年 | 182篇 |
2010年 | 154篇 |
2009年 | 137篇 |
2008年 | 114篇 |
2007年 | 131篇 |
2006年 | 132篇 |
2005年 | 94篇 |
2004年 | 72篇 |
2003年 | 71篇 |
2002年 | 49篇 |
2001年 | 46篇 |
2000年 | 34篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 32篇 |
1996年 | 21篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有2798条查询结果,搜索用时 15 毫秒
71.
Although it is well known that judicious use of adjuvants can increase the performance of foliage-applied sprays of many agrochemicals, little information is available in the public domain about their ultimate effects on pesticide residues in treated crops. In the present work, the influence of Agral (polyoxyethylene nonylphenols), Toil (methyl esters of rapeseed fatty acids) and Bond (styrene-butadiene copolymers) on surface and crop residues of diclofop-methyl/diclofop and propiconazole in wheat and field beans was investigated using a model system simulating field practice. Pesticides were applied as commercial formulations, diclofop-methyl 378 g litre(-1) EC (Hoegrass) and propiconazole 250 g litre(-1) EC (Tilt), at their maximum approved rates, 1135 g AI ha(-1) and 125 g AI ha(-1), respectively, both in the presence or absence of the maximum rate recommended for each candidate adjuvant. No detectable residues of diclofop-methyl or propiconazole were found in wheat 35 days after any of the four applications. However, residues of diclofop were present in this crop, and those from applications containing Agral (0.07 mg kg(-1) fresh weight (FW)) or Bond (0.08 mg kg(-1) FW) were significantly lower than those with no adjuvant (0.14 mg kg(-1) FW) or Toil (0.16 mg kg(-1) FW). Unlike wheat, residues of both diclofop and propiconazole were detected in field beans after harvest. Significantly higher residues of the former were recorded from the applications with Agral or Bond (ca 0.32 mg kg(-1) FW) than with those with no adjuvant or Toil (ca 0.15mg kg(-1) FW). All the propiconazole applications containing adjuvants showed a similar significant increase in residues (0.10-0.16 mg AI kg(-1) FW) over the no-adjuvant treatment (0.05 mg kg(-1) FW) in this crop. There appeared to be little agreement between the apparent amounts of uptake, as indicated by the rates of decline of surface residues up to 5 days after application, and final residues in either target species. On wheat, surface residues of diclofop-methyl decreased from initially ca 20 to as little as 0.02 mg kg(-1) FW using adjuvants; the corresponding values for propiconazole were ca 2 to ca 0.03 mg kg(-1) FW. Recoveries of diclofop-methyl from the surfaces of field beans were much higher than those from wheat, declining from ca 30 to only ca 6 mg kg(-1) FW during the course of 5 days; the corresponding residues for propiconazole were ca 2 mg to 0.15 mg kg(-1) FW. These findings are discussed in relation to uptake results obtained with radiolabelled pesticides and adjuvants in the laboratory, and to the mandatory requirements for pesticide residue data for the authorised use of adjuvants in the UK. 相似文献
72.
Sensitivity analyses using a one-at-a-time approach were carried out for leaching models which have been widely used for pesticide registration in Europe (PELMO, PRZM, PESTLA and MACRO). Four scenarios were considered for simulation of the leaching of two theoretical pesticides in a sandy loam and a clay loam soil, each with a broad distribution across Europe. Input parameters were varied within bounds reflecting their uncertainty and the influence of these variations on model predictions was investigated for accumulated percolation at 1-m depth and pesticide loading in leachate. Predictions for the base-case scenarios differed between chromatographic models and the preferential flow model MACRO for which large but transient pesticide losses were predicted in the clay loam. Volumes of percolated water predicted by the four models were affected by a small number of input parameters and to a small extent only, suggesting that meteorological variables will be the main drivers of water balance predictions. In contrast to percolation, predictions for pesticide loss were found to be sensitive to a large number of input parameters and to a much greater extent. Parameters which had the largest influence on the prediction of pesticide loss were generally those related to chemical sorption (Freundlich exponent nf and distribution coefficient Kf) and degradation (either degradation rates or DT50, QTEN value). Nevertheless, a significant influence of soil properties (field capacity, bulk density or parameters defining the boundary between flow domains in MACRO) was also noted in at least one scenario for all models. Large sensitivities were reported for all models, especially PELMO and PRZM, and sensitivity was greater where only limited leaching was simulated. Uncertainty should be addressed in risk assessment procedures for crop-protection products. 相似文献
73.
云南主要烟区烟蚜种群解毒酶活力比较 总被引:2,自引:0,他引:2
通过测定烟蚜Myzus persicae(Sulzer)的α-NA羧酸酯酶、β-NA羧酸酯酶、谷胱甘肽转移酶和乙酰胆碱酯酶的活力,比较了云南5个主要烟区田间烟蚜种群的4种酶的活力频率分布,结果表明,云南5个烟区的烟蚜田间种群的α-NA羧酸酯酶、β-NA羧酸酯酶和乙酰胆碱酯酶的高活力个体均以楚雄和昆明种群较高,昭通种群和丽江种群较低。谷胱甘肽转移酶在5个烟区烟蚜种群间差异不大。 相似文献
74.
75.
树干注药对柳树叶片几种生理指标的影响 总被引:2,自引:0,他引:2
研究了4种注干液剂(吡虫啉、啶虫脒、吡虫啉·敌敌畏和敌敌畏·氧乐果)树干注射后对垂柳叶片内几种生理指标的影响。结果表明:4种药剂树干注药后均可导致垂柳叶片内可溶性总糖及纤维素含量下降,下降程度与药剂种类及注药后时间长短有关。吡虫啉对可溶性总糖含量影响最显著,药后 6 d下降了28.31%;敌敌畏·氧乐果对纤维素含量影响最显著,药后 6 d下降了19.16%。4种药剂注药后短期内均可导致叶绿素、可溶性蛋白和淀粉含量下降,但随处理时间延长其含量又明显上升。其中吡虫啉对叶绿素含量影响最显著,药后15 d升高了21.31%;敌敌畏·氧乐果对可溶性蛋白、淀粉含量影响最显著,药后15 d分别上升24.94%和 20.32%。 相似文献
76.
77.
78.
79.
Organophosphorus pesticides (OPs) are of environmental significance due to their high toxicity to animals. Binding to plasma proteins may effective influence the toxicological properties of xenobiotics. In an attempt to evaluate the affinity of phenthoate (PTA) to bovine serum albumin (BSA) and inhibitory ability of bound PTA to acetylcholinesterase (AChE), we investigated the interactions between phenthoate (PTA) and bovine serum albumin (BSA) using tryptophan fluorescence quenching and subsequent inhibition on AChE activity by PTA. The results showed that PTA caused the fluorescence quenching of BSA because of the formation of a PTA-BSA complex. Quenching constants (Ksv), determined using the Sterns-Volmer equation to provide a measure of the binding affinity between PTA and BSA at 303, 306, 310 and 313 K were (3.4295 ± 0.0763) × 10−4, (3.2446 ± 0.0635) × 10−4, (3.0434 ± 0.0856) × 10−4 and (2.8262 ± 0.0569) × 10−4 M−1, respectively. The thermodynamic parameters, ΔH and ΔS were −25.04 kJ mol−1 and 168.94 J mol−1 K−1, respectively, which indicated that the electrostatic interactions played a major role in PTA-BSA association. The presence of BSA consistently reduced the inhibitory ability of PTA on AChE, with the relative activity being increased from 46.98 to 61.71% for the concentration range of BSA between 0 and 4.0 g L−1. 相似文献
80.
本文介绍了高效毛细管电泳仪的原理和方法,及其在农药有效成分,异构体,残留与代谢,限制中的应用和展望,着重介绍二氯喹啉酸制剂的分析方法。 相似文献