全文获取类型
收费全文 | 2143篇 |
免费 | 159篇 |
国内免费 | 102篇 |
专业分类
林业 | 101篇 |
农学 | 133篇 |
基础科学 | 57篇 |
166篇 | |
综合类 | 519篇 |
农作物 | 167篇 |
水产渔业 | 16篇 |
畜牧兽医 | 109篇 |
园艺 | 25篇 |
植物保护 | 1111篇 |
出版年
2024年 | 16篇 |
2023年 | 52篇 |
2022年 | 46篇 |
2021年 | 52篇 |
2020年 | 93篇 |
2019年 | 85篇 |
2018年 | 89篇 |
2017年 | 80篇 |
2016年 | 104篇 |
2015年 | 81篇 |
2014年 | 116篇 |
2013年 | 179篇 |
2012年 | 133篇 |
2011年 | 124篇 |
2010年 | 100篇 |
2009年 | 125篇 |
2008年 | 104篇 |
2007年 | 86篇 |
2006年 | 112篇 |
2005年 | 78篇 |
2004年 | 88篇 |
2003年 | 79篇 |
2002年 | 64篇 |
2001年 | 56篇 |
2000年 | 48篇 |
1999年 | 42篇 |
1998年 | 24篇 |
1997年 | 25篇 |
1996年 | 16篇 |
1995年 | 8篇 |
1994年 | 17篇 |
1993年 | 23篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
排序方式: 共有2404条查询结果,搜索用时 0 毫秒
61.
Mariyono J 《Pest management science》2008,64(10):1069-1073
BACKGROUND: Integrated pest management (IPM) technology has been disseminated since 1989 in Indonesia to cut down pesticide use, but the adoption and diffusion of the technology are still debated. This study aims to estimate the models of demand for pesticides and to analyse the impact of IPM technology on pesticide use. Aggregate cross-section time series data from 1990-1998 are used.RESULTS: The results show that IPM technology reduces the use of pesticides by improving the process of rice production, such that pesticides are more efficiently used. In this case, the IPM technology is not a pest control technique.CONCLUSION There is an indication that IPM technology has been adopted by farmers. This is evidence that the IPM programme in Indonesia was successful in this area. Copyright (c) 2008 Society of Chemical Industry. 相似文献
62.
Anoda cristata is a troublesome annual broad-leaved weed in summer crops in the rolling Pampa in Argentina; seeds are the only source of regeneration of this species. Seed persistence or depletion is the result of survival and loss processes, including predation. The objective of this study was to determine survival at two burial depths in undisturbed soil and predation rates of A. cristata seeds in soyabean crops in different rotations and tillage systems. Survival was discontinuous and decreased to 25% after 35 months, after which no further reduction in survival was observed to the end of the experiment at 96 months. No differences in seed survival between seeds placed on the soil surface and buried 5 cm below the soil surface were found at 80 months, but at later times survival was lower for seeds placed on the soil surface. Predation rates ranged between 0.3% day−1 and 6.7% day−1. Of the models tested, a polynomial regression of the rate of predation with time gave the best representation of seed predation. From January to July, predation was higher in non-tillage plots in the wheat/soyabean rotation. There was no significant difference in predation rates between tillage systems in the soyabean monoculture and no difference between planting densities. Higher crop residue levels in non-tillage plots in the wheat/soyabean rotation was the dominant factor influencing seed predation, probably because such habitat favours the presence of seed predators. 相似文献
63.
对6种青饲牧草用7种除草剂进行除草试验。证明播后苗前墨西哥类玉米用40%阿特拉津胶悬剂0.90kg(ai)/hm^2;M-81E饲用高粱与串叶松香草适宜用60%丁草胺乳油0.90kg(ai)/hm^2;苏丹草适宜用60%丁草胺乳油0.90kg9ai)/hm^2与25%绿麦隆可湿性粉剂0.94kg(ai)/hm^2,紫苏用12%恶草灵乳油0.27kg(ai)/hm^2与84%chinch乳油1.89 相似文献
64.
NIHAT TURSUN IRFAN ERSIN AKINCI AHMET ULUDAG ZULEYHA PAMUKOGLU DOGAN GOZCU 《Weed Biology and Management》2012,12(2):109-115
Direct seeded red pepper is a cash crop in Kahramanmara? province of Turkey as well as some other nearby provinces. Weeds are a major constraint in red pepper production. Field studies were conducted to determine critical period for weed control (CPWC) in direct seeded spice pepper in Kahramanmara?, in 2008 and 2009. The CPWC in red pepper based on a 2.5%, 5% and 10% acceptable yield loss (AYL) was calculated by fitting logistic and Gompertz equations to relative yield data. The CPWC in red pepper was determined from 0 to 1087 growing degree days (GDD) in 2008 and from 109 to 796 GDD in 2009 for 10% AYL after crop emergence in red pepper. For 2.5–5% AYL, the CPWC starts with germination and lasts until harvest. Direct seeded red pepper is very vulnerable to weed competition and weed control programs for direct seeded spice pepper in Turkey should include pre‐emergence and residual herbicides. 相似文献
65.
采用倒置"W"九点取样法和5级目测法,调查了云南冬季作物田杂草虉草的发生和危害状况。结果表明,截至2017年在云南有7个地州33个区县发现有虉草危害,其中保山地区危害最为严重,占全省受害面积的92%,其次是大理白族自治州。虉草在冬季作物田大麦、小麦、油菜和蚕豆田均有发生。危害的虉草有两个种,分别是小籽虉草Phalaris minor和奇异虉草P.paradoxa。其中小籽虉草的发生较为普遍,奇异虉草为零星发生。虉草造成的危害指数在6%~50%之间,对农作物造成的产量损失在40~110kg/667m2之间。虉草的防除以化学防除为主,人工防除为辅,但目前尚缺乏经济有效的防除农田虉草的除草剂。 相似文献
66.
Contrasting patterns of variation in weedy traits and unique crop features in divergent populations of US weedy rice (Oryza sativa sp.) in Arkansas and California 下载免费PDF全文
67.
为探索如何提高稻田除草剂使用效率, 实现除草剂减量使用, 本试验以30%苄嘧·丙草胺乳油为供试药剂, 以‘甬优1540’为供试水稻, 保持除草剂总量一致的前提下, 利用大田试验和温室盆栽试验, 通过设置插秧前?插秧时?插秧后单次施用100%推荐剂量, 插秧前和插秧后各施用50%推荐剂量, 插秧前及苗期各施用50%推荐剂量, 以及不施用除草剂的6种处理, 研究不同施药次数及施药时间对稻田禾本科?阔叶类?莎草科三类杂草及其总草防除效果的影响?温室盆栽试验表明, 与其他处理相比, 采用30%苄嘧·丙草胺乳油于移秧后3 d施药50%推荐剂量及苗期再施50%推荐剂量的处理, 可使水稻移栽后24 d时的稗草?千金子和耳叶水苋发生量明显少于其他施药方式, 说明该施药方式对稻田杂草具有明显的抑制作用; 此外, 大田试验表明, 采用上述同样的施药方式, 可使水稻在移栽后36 d时的分蘖在各处理中达到最大量, 为16.90万/667m2, 且杂草总发生量最少, 为17.00株/m2, 杂草株防效最高, 为84.17%?本研究表明, 30%苄嘧·丙草胺乳油在移秧后3 d施用50%推荐剂量, 及苗期再施50%推荐剂量, 对稻田杂草防除效果较好? 相似文献
68.
Controlled growth chamber experiments were conducted to determine factors affecting seed germination and emergence of the troublesome weed Gomphrena perennis. The objective of this research was to examine the effects of temperature, light, moist chilling, osmotic potential, dry storage and depth of seed burial on G. perennis germination and emergence. The optimum temperature for germination was around 15–20°C. Seeds showed germination rates above 90% under 20/10 and 25/15°C temperature regimes. The minimum exposure to light needed to stimulate germination was 1 min. However, the light requirement was reduced after a long storage period. Furthermore, germination was high (>90%) in all moist‐chilling treatments tested. Germination was highly sensitive to increasing osmotic stress. The highest germination percentage (94%) was achieved at 0 MPa, and decreasing osmotic potential from 0 to ?0.3 MPa reduced germination to 11%. The highest seedling emergence occurred for seeds placed from 0 to 1 cm deep, and no seedlings emerged from a 5‐cm burial depth. Gomphrena perennis has a suitable environment in a no‐till soybean field, where seeds remaining on the surface have the required temperature, light and depth needed for germination. 相似文献
69.
N Colbach L Biju‐Duval A Gardarin S Granger S H M Guyot D Mézière N M Munier‐Jolain S Petit 《Weed Research》2014,54(6):541-555
Weeds are both harmful for crop production and important for biodiversity, while herbicides can pollute the environment. We thus need new cropping systems optimising all cultural techniques, reconciling agricultural production, herbicide reduction and biodiversity conservation. Here, we show how to (i) develop models quantifying the effects of cropping systems on weed dynamics, (ii) integrate interactions between weeds and other organisms, (iii) predict the impact on production and biodiversity and (iv) use the model for multicriteria evaluation and multiobjective design of cropping systems. Among the existing weed dynamics models, we chose the one closest to our requirements to illustrate these different steps, that is, FlorSys which predicts multispecific weed dynamics as a function of cultural techniques and pedoclimate. We have illustrated the development of interaction submodels with the example of a crop pathogen whose propagation is increased when infecting grass weeds. To evaluate the weed flora impact, predicted weed densities were translated into indicators of harmfulness (crop yield loss, technical harvest problems, harvest pollution, field infestation, crop disease increase) and biodiversity (weed species richness and equitability, trophic resources for birds, insects and pollinators). Simulations were run over several years and with different weather scenarios (i) to optimise cultural techniques to control harmful weeds, (ii) to analyse the impact of changing agricultural practices (e.g. simplified tillage and rotations, no‐till, temporary crops) on weed density, species and trait composition and (iii) to evaluate cropping systems for their ability to reconcile agricultural production and biodiversity, thus identifying levers for designing sustainable cropping systems. 相似文献
70.