首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   534篇
  免费   44篇
  国内免费   1篇
林业   27篇
农学   13篇
基础科学   2篇
  154篇
综合类   32篇
农作物   38篇
水产渔业   47篇
畜牧兽医   205篇
园艺   15篇
植物保护   46篇
  2023年   8篇
  2022年   8篇
  2021年   43篇
  2020年   30篇
  2019年   23篇
  2018年   23篇
  2017年   26篇
  2016年   33篇
  2015年   19篇
  2014年   23篇
  2013年   29篇
  2012年   39篇
  2011年   50篇
  2010年   36篇
  2009年   22篇
  2008年   32篇
  2007年   24篇
  2006年   15篇
  2005年   22篇
  2004年   22篇
  2003年   14篇
  2002年   21篇
  2001年   1篇
  2000年   1篇
  1999年   2篇
  1998年   4篇
  1997年   2篇
  1996年   2篇
  1994年   1篇
  1988年   1篇
  1986年   1篇
  1983年   1篇
  1977年   1篇
排序方式: 共有579条查询结果,搜索用时 15 毫秒
111.
112.
113.
The inclusion of phytogenics in fish feed is a promising strategy to compensate for the negative performance effects of replacing fishmeal (FM) with vegetable sources. The present work assessed the interactive effects of different dietary FM levels (22.5 and 10% of formulation) and the supplementation of a commercial blend of anise, citrus, and oregano essential oils (Digestarom PEP M.G.E 150) on European sea bass, Dicentrarchus labrax growth performance, nutrient utilization, gut morphology, antioxidant status, and immunological response over a 60‐day growth trial. Results showed decreased growth and protein efficiency ratio and increased feed conversion ratio with a low dietary FM level. In contrast, supplementation of the phytogenic product demonstrated improved performance and nutrient utilization together with increased protein and energy retention. Supplementation with the plant essential oils fully compensated for the negative intestinal changes observed in sea bass fed a low‐FM diet but showed little improvement in fish immunological response, except for the 30% increase in lysozyme activity observed in fish fed the low FM‐supplemented diet compared to those fed the standard high‐FM diet. Overall, this study supports the use of this phytogenic product in low‐FM diets as a possible tool to decrease feed costs associated with FM without compromising fish performance, nutrient utilization, and health.  相似文献   
114.
115.
Soybean rust in Brazil is currently controlled with several commercial fungicide premixes composed of demethylation inhibitors (EPOXiconazole, CYPRoconazole, PROThioconazole, TEBUconazole), quinone-outside inhibitors (AZOXystrobin, TriFLoXystrobin, PYRAclostrobin, PICOxystrobin), and succinate demethylation inhibitors (BENZovindiflupyr, BIXaFen, FLUXapyroxad). Here, we summarize the performance of eight premixes evaluated in 177 cooperative trials conducted in 46 locations across 10 states from 2015 to 2020. All fungicide treatments were sprayed three times starting at R1/R2. Percentage control (, %), from back-transforming meta-analytic estimates of the log of the ratio, ranged from 56.2% (PICO + CYPR) to 76.8% (BIXF + TFLX + PROT). Estimates of mean yield difference (, kg/ha) between fungicide-treated and untreated plots were greatest for BIXF + TFLX + PROT (1,080) followed by PICO + BENZ (1,010), PYRA + EPOX + FLUX (981.5), AZOX + BENZ (910), TFLX + PROT (891), PICO +TEBU (682), TFLX + CYPR (646), and PICO + CYPR (600). Significant declines in both and in as little as 4 years were detected for AZOX + BENZ (35.3%; 550 kg/ha) and PICO + BENZ (15.5%; 359.8 kg/ha). Variance in was reduced by the inclusion of baseline severity as covariate. In trials where baseline disease was ≥70%, yield was 250 kg/ha greater compared to areas with low baseline disease. Disease control and yield response were generally greater in the south-east, where the frequency of profitable scenarios was 30% higher on average than in the north-west. Results of this meta-analysis are critical for supporting decisions during planning of fungicide programmes.  相似文献   
116.
Powdery scab (PS), caused by Spongospora subterranea, reduces the quality and marketability of potatoes worldwide. Disease symptoms include lesions on the tuber surface and root galling, which may lead to yield losses. In the current study we report a sustainable approach to reduce PS by manipulating soil temperature during tuber initiation. Plant cover with nonwoven fabric significantly reduced PS on tubers by 54%–69% in 2017 and 84%–93% in 2019, compared to the control, and root galling by 96% in 2019, due to an increased average minimum and maximum soil temperature of 1.8 and 4.2 °C in respective years. Additional preplanting soil treatments were also evaluated in naturally infested soil. In 2017, disease incidence and severity were significantly reduced using 2.5 or 5 L a.i./ha fluazinam in broadcast application or in-furrow, and by 0.375 or 0.75 L a.i./ha flusulphamide applied in-furrow. In 2019, disease incidence and severity were significantly reduced by the broadcast application of fluazinam, and 75 kg/ha calcium cyanamide, but the latter had a negative impact on yield. Soil fumigation with metam sodium resulted in a 98% reduction in PS. Root galling was significantly reduced by calcium cyanamide, metam sodium, and fluazinam in the 2019 trial only. Foliar application of resistance-inducing phosphonates combined with fluazinam application had no additive effect on PS incidence and severity. Integrated approaches such as tolerant cultivars, soil testing, preplanting fungicide application, and sustainable means of control such as foliage cover for a short period may be implemented in order to control the disease and minimize damage.  相似文献   
117.
Timely delivery of adjuvant chemotherapy has been shown to be advantageous in many human cancers and canine osteosarcoma. Adjuvant chemotherapy has been shown to improve outcome for canine splenic hemangiosarcoma. The aim of this retrospective study was to investigate whether timely adjuvant chemotherapy administration resulted in better outcome in dogs with non-metastatic splenic hemangiosarcoma undergoing splenectomy. Medical records were searched for dogs with non-metastatic, splenic hemangiosarcoma that received splenectomy and adjuvant chemotherapy. The number of days from surgery to the first chemotherapy dose (StoC) was evaluated to identify the cut-off value associated with the best survival advantage. StoC and other possible prognostic factors were tested for influence on time to metastasis (TTM) and overall survival (OS). Seventy dogs were included. Median StoC was 20 days (range: 4–70). The time interval associated with the greatest survival benefit was 21 days. Median TTM and OS of dogs with StoC ≤ 21 days were significantly longer than those with StoC >21 days (TTM: 163 vs. 118 days, p = .001; OS: 238 vs. 146 days, p < .001). On multivariable analysis, StoC >21 days was the only variable significantly associated with increased risk of tumour progression (HR 2.1, p = .010) and death (HR 2.3; p = .008). Starting adjuvant chemotherapy within 21 days of surgery may be associated with a survival benefit in dogs with non-metastatic splenic hemangiosarcoma, possibly due to the early targeting of newly recruited metastatic cells after surgery.  相似文献   
118.
119.
Chemical profiles of non-invasive biological material, such as feces, have great potential to study elusive animals or those with low population densities. Here, we use a metabolomic approach to evaluate Neotropical mustelids as a biological model to describe the diversity of the metabolites present in fecal samples, as well as to evaluate the potential of chemical profiles for taxonomic discrimination. We collected fecal samples from captive individuals of 5 species of mustelids occurring in Brazil and analyzed them by liquid chromatography coupled to high-resolution mass spectrometry. Over 200 compounds have been annotated; “bile acids, alcohols and derivatives” was the most expressive class in the metabolome of all the species. We successfully discriminated 3 taxonomic groups: 1—tayra (Eira barbara); 2—otters (Lontra longicaudis and Pteronura brasiliensis; 1); and 3—grisons (Galictis vittata and Galictis cuja). Several compounds seemed to be associated with food intake and the digestive process, while others were found for the first time in Neotropical mustelids. We concluded that mustelids show high metabolome diversity and that species-specific identification through metabolomic profiles is possible, thus contributing to the development and implementation of additional non-invasive approaches in the study of mustelids.  相似文献   
120.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号