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   13785篇
  免费   1055篇
  国内免费   3篇
林业   1177篇
农学   535篇
基础科学   113篇
  3598篇
综合类   441篇
农作物   683篇
水产渔业   1401篇
畜牧兽医   5463篇
园艺   232篇
植物保护   1200篇
  2023年   105篇
  2022年   175篇
  2021年   349篇
  2020年   321篇
  2019年   262篇
  2018年   649篇
  2017年   659篇
  2016年   657篇
  2015年   514篇
  2014年   608篇
  2013年   933篇
  2012年   1057篇
  2011年   990篇
  2010年   562篇
  2009年   489篇
  2008年   786篇
  2007年   785篇
  2006年   638篇
  2005年   612篇
  2004年   543篇
  2003年   512篇
  2002年   418篇
  2001年   298篇
  2000年   307篇
  1999年   263篇
  1998年   67篇
  1997年   53篇
  1996年   41篇
  1995年   31篇
  1994年   31篇
  1993年   31篇
  1992年   75篇
  1991年   63篇
  1990年   63篇
  1989年   85篇
  1988年   49篇
  1987年   70篇
  1986年   58篇
  1985年   63篇
  1984年   48篇
  1983年   48篇
  1982年   26篇
  1981年   27篇
  1979年   39篇
  1978年   33篇
  1977年   34篇
  1974年   30篇
  1973年   52篇
  1972年   38篇
  1971年   29篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
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   
122.
Landscape Ecology - An understanding of species-habitat relationships is required to assess the impacts of habitat fragmentation and degradation. To date, habitat modeling in fragmented landscapes...  相似文献   
123.
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   
124.
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   
125.
Plant Foods for Human Nutrition - ADP-glucose pyrophosphorylase (AGPase) is a key enzyme of starch synthesis in seeds, tubers and fruits. UDP-glucose pyrophosphorylase (UGPase) is an important...  相似文献   
126.
Plant Foods for Human Nutrition - Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized, among others by abnormal levels of acetyl- and butyrylcholinesterase in...  相似文献   
127.
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   
128.
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   
129.
Plant Foods for Human Nutrition - Grapes contain high contents of phenolics, which are known to possess health promoting properties. Exogenous application of phytoregulators, mainly methyl...  相似文献   
130.
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