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   881篇
  免费   43篇
  国内免费   2篇
林业   76篇
农学   66篇
基础科学   15篇
  253篇
综合类   51篇
农作物   101篇
水产渔业   70篇
畜牧兽医   213篇
园艺   16篇
植物保护   65篇
  2023年   16篇
  2022年   21篇
  2021年   28篇
  2020年   47篇
  2019年   50篇
  2018年   52篇
  2017年   60篇
  2016年   53篇
  2015年   23篇
  2014年   37篇
  2013年   99篇
  2012年   56篇
  2011年   60篇
  2010年   40篇
  2009年   36篇
  2008年   34篇
  2007年   22篇
  2006年   16篇
  2005年   12篇
  2004年   11篇
  2003年   13篇
  2002年   15篇
  2001年   15篇
  2000年   15篇
  1999年   8篇
  1998年   6篇
  1997年   4篇
  1996年   3篇
  1995年   3篇
  1994年   5篇
  1993年   5篇
  1992年   5篇
  1991年   7篇
  1990年   7篇
  1989年   5篇
  1988年   4篇
  1987年   3篇
  1986年   3篇
  1985年   4篇
  1980年   5篇
  1978年   2篇
  1977年   2篇
  1975年   1篇
  1973年   1篇
  1971年   2篇
  1970年   1篇
  1968年   1篇
  1960年   1篇
  1959年   3篇
  1957年   2篇
排序方式: 共有926条查询结果,搜索用时 817 毫秒
101.
102.
Paddy and Water Environment - The application of isoprothiolane in rice cultivation may give a risk to the aquatic ecosystem. The present study was undertaken to determine the level of...  相似文献   
103.
A review of publications on “Strawberry” was done by using the Scopus database for the period 1960–2016. A total of 10,400 articles were found in the database and analyzed using a variety of measures. Results show that publication increased exponentially from 1960 to 2016. Multiple authors are collaborating in strawberry research. Acta Horticulturae was the most productive journal. The United States of America was the most productive country. The greatest portion of the research was concerned with medicinal benefits of strawberries to humans. This work will be useful to researchers in identifying trends in strawberry research.  相似文献   
104.
Crop water parameters, including actual evapotranspiration, transpiration, soil evaporation, crop coefficients, evaporative fractions, aerodynamic resistances, surface resistances and percolation fluxes were estimated in a commercial mango orchard during two growing seasons in Northeast Brazil. The actual evapotranspiration (Ea) was obtained by the eddy covariance (EC) technique, while for the reference evapotranspiration (E0); the FAO Penman–Monteith equation was applied. The energy balance closure showed a gap of 12%. For water productivity analysis the Ea was then computed with the Bowen ratio determined from the eddy covariance fluxes. The mean accumulated Ea for the two seasons was 1419 mm year−1, which corresponded to a daily average rate of 3.7 mm day−1. The mean values of the crop coefficients based on evapotranspiration (Kc) and based on transpiration (Kcb) were 0.91 and 0.73, respectively. The single layer Kc was fitted with a degree days function. Twenty percent of evapotranspiration originated from direct soil evaporation. The evaporative fraction was 0.83 on average. The average relative water supply was 1.1, revealing that, in general, irrigation water supply was in good harmony with the crop water requirements. The resulting evapotranspiration deficit was 73–95 mm per season only. The mean aerodynamic resistance (ra) was 37 s m−1 and the bulk surface resistance (rs) was 135 s m−1. The mean unit yield was 45 tonne ha−1 being equivalent to a crop water productivity of 3.2 kg m−3 when based on Ea with an economic counterpart of US$ 3.27 m−3. The drawback of this highly productive use of water resources is an unavoidable percolation flux of approximately 300 mm per growing season that is detrimental to the downstream environment and water users.  相似文献   
105.
Field experiments were conducted to study soil properties, soil enzymes activities, water use efficiency (WUE) and crop productivity after six years of soya bean straw mulching in the semi‐arid conditions of China. The experiment included four treatments: CK (Control), N (240 kg N ha‐1), H (soya bean straw mulching at half rate 700 kg ha‐1 with 240 kg N ha‐1) and F (soya bean straw mulching at full rate 1,400 kg ha‐1 with 240 kg N ha‐1). Soil organic carbon (SOC), soil labile organic carbon (LOC), soil available N (AN), available P (AP) and enzyme activities were analysed after wheat harvesting in 2016 and 2017. Results show that straw amounts had positive effects on the soil fertility indices being higher for treatment F. The SOC, LOC, AN, AP and enzyme activities (i.e. saccharase, urease and alkaline phosphatase) were in the order of F > H > N > CK. High wheat grain yield and WUE were observed for F treatment. A total of six years mulching along with 240 kg ha‐1 nitrogen fertilizer application is sufficient for wheat yield stability and improving soil properties except urease activities in the semi‐arid condition of China. However, the straw mulching amount should be further studied with minimum nitrogen fertilizer for an environment‐friendly and effective approach for improving the soil biological properties with adequate crop production on a sustainable basis in the semi‐arid region of China.  相似文献   
106.
In the present study, naringin, a flavonoid isolated from the grape and citrus fruit species, was incorporated with poly(ε-caprolactone)/gelatin composite mats in order to develop a potential wound dressing. The composite mats were prepared by electrospinning of poly(ε-caprolactone)/gelatin (1:1 (w/w)) solution incorporated with 1.50 %, 3 % and 6 % (w/w) of naringin. The electrospun mats were evaluated regarding their morphology, contact angle, water-uptake capacity, water vapor transmission rate, tensile properties, drug release, cellular response and in vivo wound healing activity. The study showed that after 2 weeks, the full-thickness excisional wounds of Wistar rats treated with the naringin-loaded dressings achieved a wound closure of higher than 94 % and the dressing containing 6 % (w/w) naringin had almost 100 % wound closure. The sterile gauze, as the control group, showed nearly 86 % of wound closure after this period of time. Our results provided evidence that supports the possible applicability of naringin-loaded wound dressing for successful wound treatment.  相似文献   
107.
Tropical Animal Health and Production - In comparison with other livestock, tuberculosis (TB) in camels has not been extensively studied in Nigeria. Camels in the hands of Nigerian pastoralists...  相似文献   
108.
This study aimed to evaluate the effects of dietary supplemental methionine (Met) source and betaine (Bet) replacement for Met on performance and activity of mitochondrial respiratory chain enzymes (MRCEs) in normal and heat‐stressed broiler chickens. Total of 1,200‐day‐old Ross 308 chicks were allocated to two houses, each consisted of 12 treatments, five replicates of 10 birds each with 2 × 2×3 × 2 (temperature × Met source × Met level × Bet, respectively) split‐plot factorial arrangement. Met level in the basal diets was 70% requirements (Req) that was increased to the requirement or 130% by supplemental dl ‐ or l ‐Met. Bet was or was not substituted at the rate of 30% supplemental dl ‐ or l ‐Met. Feed conversion ratio (FCR) in chicks fed 70% l ‐Met was lower than those fed 70% dl ‐Met diet during 1–10 days (p = 0.04). Broilers fed diets containing requirement or 130% Met, regardless of its source, showed higher weight gain (WG) than those received 70% Met diet during 11–42 days (p < 0.001). Feed intake (FI) of broilers fed 130% Met diet was decreased compared to other two groups during 11–42 days (p < 0.05). One hundred thirty percent Met requirement diet resulted in lower FCR comparing to other two groups during 11–42 days (p < 0.001). Heat‐stressed birds grew less than those under normal condition (p < 0.05). Broilers fed Req Met diet under normal temperature exhibited higher activities of complexes (Cox) I and III (p < 0.05). Cox I activity in heat‐stressed birds fed Bet + diet was similar to those fed Bet‐diet under normal temperature (p = 0.046). It is concluded that performance and the activities of Cox I and III were increased as the level of Met increased. Bet replacement for 30% supplemental Met resulted in similar consequences comparing to non‐Bet replacement diets on performance, but increased the activity of Cox III. l ‐Met was effective than dl ‐Met at the cellular level. High ambient temperature depressed performance and MRCE activity.  相似文献   
109.
Tropical Animal Health and Production - Sperm storage function of the sperm storage tubules (SSTs) is directly correlated with the fertility of laying hens. SSTs are located at the utero-vaginal...  相似文献   
110.
This study compares the factors associated with variable interval to oestrus and ovulation between early versus late ovulating goats following PGF administration. The time of ovulation in Beetal goats (n = 38) was monitored through transrectal ultrasound at every 6 hr following a single dose of PGF (experiment 1). Variations in oestrus and ovulation times were further explored through the changes in follicular dynamics, endocrine profiles and behaviour in another set of goats (n = 13) following single PGF given randomly during the luteal phase (experiment 2). The ovulation time varied between 60 and 96 hr, and 57% of ovulations occurred by 72 hr following PGF (experiment 1). Accordingly, the goats (n = 13) in the second experiment were retrospectively divided either into early and/or late ovulating, that is, ≤72 and/or ≥84 hr following PGF. The onset of oestrus, peak estradiol‐17β concentration and LH surge after PGFwas first observed in early than late ovulating goats (p < 0.05). The goats ovulating early had larger follicle and smaller CL in diameter at the time of PGF administration than those ovulating late (5.4 ± 0.2 vs. 4.3 ± 0.2 mm and 10 ± 0.6 vs. 11.8 ± 0.3 mm, respectively; p < 0.05). Likewise, plasma progesterone concentration tended to be lower (p = 0.087) in early than late ovulating goats. In conclusion, the size of dominant follicle and CL at the time of PGF2a determines the interval to ovulation following a single dose of PGF2a during the luteal phase.  相似文献   
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