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   24713篇
  免费   4347篇
  国内免费   1363篇
林业   1578篇
农学   2068篇
基础科学   688篇
  3896篇
综合类   6246篇
农作物   1532篇
水产渔业   3317篇
畜牧兽医   8065篇
园艺   879篇
植物保护   2154篇
  2024年   40篇
  2023年   223篇
  2022年   458篇
  2021年   749篇
  2020年   1026篇
  2019年   1566篇
  2018年   1350篇
  2017年   1556篇
  2016年   1480篇
  2015年   1455篇
  2014年   1564篇
  2013年   2013篇
  2012年   1782篇
  2011年   1935篇
  2010年   1885篇
  2009年   1337篇
  2008年   1500篇
  2007年   1232篇
  2006年   1015篇
  2005年   939篇
  2004年   683篇
  2003年   661篇
  2002年   808篇
  2001年   593篇
  2000年   549篇
  1999年   293篇
  1998年   159篇
  1997年   144篇
  1996年   114篇
  1995年   111篇
  1994年   98篇
  1993年   102篇
  1992年   108篇
  1991年   92篇
  1990年   96篇
  1989年   85篇
  1988年   54篇
  1987年   60篇
  1986年   35篇
  1985年   38篇
  1984年   26篇
  1983年   30篇
  1981年   26篇
  1980年   19篇
  1978年   30篇
  1977年   25篇
  1976年   29篇
  1974年   24篇
  1973年   23篇
  1972年   23篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
This retrospective study describes the computed tomography (CT) findings in 59 horses presented with diseases of the head over 8 years that underwent CT examination of this region, including dental or sinonasal diseases (Group A) (n = 42), osseous and/or articular diseases (Group B) (n = 11) and soft tissue diseases (Group C) (n = 6). For Group A, radiographic and CT findings comparison was possible. Computed tomography had higher sensitivity (100%) and specificity (96.7%) than radiography in diagnosing dental disease. Compared to CT, radiographic identification of sinus involvement was less sensitive, particularly for ventral conchal and sphenopalatine sinuses and presented an overall sensitivity of 43.5 and 16.7%, respectively. In Group B CT allowed identification of a higher number of bone fragments and fractures in the maxillary, lacrimal, sphenoidal, temporal and zygomatic bones not identified radiographically. Accurate identification of CT changes in the temporomandibular joint and temporohyoid articulation was also possible. Group C included both intra‐ and extra‐cranial disease, retrobulbar masses being the most representative pathology (n = 3). In this group, CT was considered the gold standard for detection of periorbital diseases. We conclude that CT is an imaging technique with high diagnostic value for evaluating the equine head, yielding additional information over multiple radiographic views, which may alter the outcome of the case. Additionally, this paper reports several conditions not previously described using CT.  相似文献   
993.
994.
995.
996.
A 10-year-old Maltese dog was presented with a firm mass on the left side of his neck. Physical examination confirmed a firm mass in the left and a submandibular swelling in the right cervical region. Sialolithiasis and associated sialocele in both mandibular salivary glands were suspected and bilateral sialoadenectomy was performed. The stones were identified as non-mineral sialoliths.  相似文献   
997.
This study aimed to evaluate the effects of supplementing a basal diet (CTR) with raw garlic (GAR) or garlic oil (GAO) on blood profile in sheep. Monensin (MON, 33 mg/kg DM) was used as positive control. Four ruminally fistulated rams were used in three experiments each arranged in a 4 × 4 Latin square design with 28‐day periods. Experiments 1 and 2 differed in the dose of GAR (75 vs. 100 g/kg DM) and GAO (500 vs. 750 mg/kg DM), while experiment 3 was designed to compare the two doses of each additive (GAR and GAO). The animals were fed a basal diet as TMR consisting of 77.83% forage (alfalfa hay and corn silage) and 22.17% concentrate, providing 10.50 MJ/kg DM (metabolizable energy) and 16.5% crude protein to cover maintenance energy and protein requirements. Supplementation of monensin decreased (P < 0.05) β‐hydroxybutyrate (BHB) and non‐esterified fatty acid (NEFA) concentrations in the blood compared with other treatments. There was no significant effect of additives on serum concentration of glucose, total triglycerides, cholesterol, total protein, albumin and blood urea nitrogen (BUN). Although the serum insulin concentration was elevated in sheep receiving MON and GAO (P < 0.01), no change was observed in blood glucose concentration. No significant effect of GAO and GAR was observed in key energy and protein‐related blood metabolites. However, administration of monensin had a positive influence on energy indices. In conclusion, whereas parameters characterizing the energy balance did not show a significant effect of GAR supplementation, a higher insulin concentration in GAO‐treated animals was observed.  相似文献   
998.
999.
1000.
The aim of this study was to assess the effects of feeding Atriplex halimus (AH) silage treated with two developed enzyme cocktails to sheep on feed intake, nutrient digestibility and ruminal fermentation. The AH silage was treated without or with 2 L of ZAD1® or ZAD2®/1000 kg with 5% molasses and ensiled for 30 days. Barley grain (300 g/head/day) was fed as an energy supplement once daily at 10.00 hours and AH silage with or without enzyme treatment was offered ad libitum to animals twice daily at 09.00 and 16.00 hours. Sheep were fed on four experimental forage diets comprised of AH silage and barley (D1), AH silage treated with ZAD1® and barley (D2), AH silage treated with ZAD2® and barley (D3) and AH silage treated with a combination of ZAD1® and ZAD2® (1:1) and barley (D4). Ensiling AH with enzymes reduced its contents of neutral detergent fiber and acid detergent fiber. The dry matter intake of AH of D2, D3 and D4 decreased (P < 0.001) as compared to D1. However, enzyme‐treated diets had greater total digestible nutrients intake (P < 0.001) as compared to D1. The nutrients digestibility for D2, D3 and D4 were higher than those for D1 (P < 0.001), and were higher for D3 as compared to both D2 and D4. Sheep fed on D3 had highest (P < 0.001) ruminal total volatile fatty acids concentration, ammonia nitrogen concentration and microbial protein yield. It could be concluded that AH silage treated with ZAD1® or ZAD2® improved digestibility and rumen fermentation in sheep.  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