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   11573篇
  免费   828篇
  国内免费   111篇
林业   1094篇
农学   484篇
基础科学   96篇
  2984篇
综合类   490篇
农作物   630篇
水产渔业   1254篇
畜牧兽医   4241篇
园艺   205篇
植物保护   1034篇
  2023年   89篇
  2022年   161篇
  2021年   298篇
  2020年   317篇
  2019年   298篇
  2018年   531篇
  2017年   545篇
  2016年   546篇
  2015年   423篇
  2014年   481篇
  2013年   744篇
  2012年   926篇
  2011年   860篇
  2010年   545篇
  2009年   451篇
  2008年   634篇
  2007年   645篇
  2006年   531篇
  2005年   520篇
  2004年   439篇
  2003年   401篇
  2002年   320篇
  2001年   233篇
  2000年   238篇
  1999年   202篇
  1998年   52篇
  1997年   56篇
  1996年   38篇
  1995年   37篇
  1994年   23篇
  1993年   22篇
  1992年   60篇
  1991年   45篇
  1990年   51篇
  1989年   53篇
  1988年   42篇
  1987年   42篇
  1986年   48篇
  1985年   53篇
  1984年   40篇
  1983年   37篇
  1982年   20篇
  1981年   15篇
  1979年   34篇
  1978年   32篇
  1977年   30篇
  1974年   30篇
  1973年   45篇
  1972年   33篇
  1971年   29篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Dothistroma needle blight (DNB) is a serious needle disease of conifers that primarily affects pine species (Pinus spp.). Dothistroma septosporum is one of the DNB pathogens that has a diverse range of host species excluding Pinus armandii. In 15 inoculated P. armandii seedlings, D. septosporum acervuli were observed in 43 infected needles of ten seedlings with a mean disease severity of 1.11% at 25 weeks after inoculations, demonstrating the potential of D. septosporum to cause symptoms on the needles of P. armandii via artificial inoculation. The disease severity of P. armandii was similar to the positive control, Pinus nigra (median 0.75 for P. armandii to 0.70 for P. nigra), thus, P. armandii acts under artificial conditions as a susceptible host species.  相似文献   
102.
Landscape Ecology - Landscape connectivity plays a key role in determining the persistence of species inhabiting fragmented habitat patches. In dynamic landscapes, most studies measure connectivity...  相似文献   
103.
Landscape Ecology - Landscape ecology early on developed the awareness that central objects of investigation are not stable over time and therefore the historical dimension must be included, or at...  相似文献   
104.
Adsorption, incubation and soil-column experiments with bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were carried out in ten different soils from the marches surrounding the Doñana National Park (Huelva, SW Spain). Adsorption isotherms for the different soils showed a good fit with the Freundlich equation. Bentazone was poorly adsorbed in all the soils studied, with no significant relationship between theKf values and soil characteristics. A significant correlation was obtained between the soil organic matter content and the distribution constant values (Kd) calculated at an equilibrium concentration of 200 μg cm−3. The low adsorption and non-degradation of bentazone on these soils suggest that the herbicide readily percolates through soils to reach the surface and ground waters. The mobility of bentazone through three soil columns was also studied. The mass balances carried out showed that bentazone was totally eluted from the soil columns. The theoretical model applied to explain bentazone leaching under our experimental conditions seems to be suitable for soil columns with a uniform water-flow rate.  相似文献   
105.
The butyl ester of buthionine sulfoximine (BBSO) applied topically to the nymph V stage of Triatoma infestans (Klug) caused glutathione depletion which was maintained for four days after treatment. Topical pre-treatment of nymph V with BBSO significantly synergised the toxicity of DDT and fenitrothion to T. infestans.  相似文献   
106.
The addition of protein supplementation in a silvopastoral system can contribute to improved forage intake and digestibility. Our objective was to evaluate in vitro ruminal parameters, digestibility and gas production of Marandu palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster] in a silvopastoral system and compare this to parameters obtained from diets with protein supplementation. Forage was sampled during the growing season (November to April) in 2016/17 and 2017/18. In vitro incubation treatments consisted of four levels of protein supplement (20% of crude protein; CP) in the diet (0.1, 0.2, 0.3 and 0.4 g/kg of body weight). The neutral detergent fibre, acid detergent fibre and indigestible neutral detergent fibre concentrations were highest in the first year. In the second year, CP concentration was 21% greater than in the first year. There was a linear increase for digestion rate, a quadratic effect for lag time and a linear decrease for average digestion time as supplementation levels were increased. The least lag time and digestion time occurred in the second year. There was no supplementation effect on ruminal pH, acetate and butyrate concentrations. Second-year in vitro dry matter digestibility (IVDMD) was greater than in the first year. Increases in supplementation levels linearly enhanced IVDMD and reduced methane (CH4) production. The inclusion of a protein supplement contributed to reduced CH4 and increased volatile fatty acids production; therefore, we recommended the supplement inclusion of >0.28 g/kg of BW for animals grazing in well-managed palisadegrass pastures.  相似文献   
107.
In silvopastoral (SP) systems, forage responses depend on the microenvironment in which the plants develop. Our objective was to evaluate canopy and tillering characteristics of shaded 'Marandu' palisadegrass [Brachiaria brizantha (Hochst A Rich) Stapf, syn. Urochloa brizantha] under continuous stocking in a SP system. Treatments were one full sun (FS) and three shaded systems (silvopasture, SP) corresponding to distances from tree groves: 7.5 m north (SP1), and 15 m (SP2) and 7.5 m south (SP3) studied during two rainy seasons (Year 1 and Year 2). The tree in the SP system was Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden × Eucalyptus urophylla S. T. Blake). The photosynthetic active radiation was greater in FS (923 μmol m-2 s-1), followed by SP2 (811 μmol m-2 s-1), SP1 (727 μmol m-2 s-1) and SP3 (673 μmol m-2 s-1). Forage accumulation in FS was 15% greater than the mean of SP1, SP2 and SP3 (10,663 kg DM/ha). There was no difference in net accumulation of leaf, stem and dead material, averaging 3,302, 3,420 and 4,063 kg DM/ha respectively. Leaf accumulation and accumulation rate were greater in Year 2, and leaf accumulation rate was similar among treatments (19 kg DM ha−1 day−1). Leaf proportion increased 14% from Year 1 to Year 2. Specific leaf area was greater for treatments SP1 and SP3 (193 cm2/g). Tiller population density was similar across treatments in Year 1. Shaded palisadegrass maintains leaf productivity similar to FS under continuous stocking in an SP system.  相似文献   
108.
Plant Foods for Human Nutrition - The purpose of this study was to compare the yield, chemical composition, antimicrobial and antioxidant properties of essential oils isolated from leaves of Laurus...  相似文献   
109.
Plant Foods for Human Nutrition - In this study the breadmaking potential of lupin flour from L. mutabilis after being debittered (DLF) and solid state fermented (FLF) was evaluated in lupin-wheat...  相似文献   
110.
Plant Foods for Human Nutrition - Chickpea is one of the most consumed legumes worldwide. Among their benefits are the high protein concentration that reflects not only at the nutritional level but...  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