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   3242篇
  免费   198篇
  国内免费   5篇
林业   204篇
农学   83篇
基础科学   22篇
  561篇
综合类   720篇
农作物   80篇
水产渔业   264篇
畜牧兽医   1172篇
园艺   99篇
植物保护   240篇
  2024年   10篇
  2023年   20篇
  2022年   32篇
  2021年   76篇
  2020年   83篇
  2019年   92篇
  2018年   84篇
  2017年   87篇
  2016年   92篇
  2015年   73篇
  2014年   80篇
  2013年   132篇
  2012年   197篇
  2011年   230篇
  2010年   155篇
  2009年   106篇
  2008年   232篇
  2007年   228篇
  2006年   205篇
  2005年   197篇
  2004年   204篇
  2003年   200篇
  2002年   180篇
  2001年   42篇
  2000年   34篇
  1999年   34篇
  1998年   20篇
  1997年   13篇
  1996年   18篇
  1995年   15篇
  1994年   13篇
  1993年   11篇
  1992年   10篇
  1991年   18篇
  1990年   10篇
  1989年   13篇
  1988年   8篇
  1987年   14篇
  1986年   12篇
  1985年   15篇
  1984年   12篇
  1983年   8篇
  1982年   8篇
  1980年   7篇
  1977年   8篇
  1976年   7篇
  1974年   16篇
  1973年   7篇
  1971年   7篇
  1968年   6篇
排序方式: 共有3445条查询结果,搜索用时 15 毫秒
41.
OBJECTIVE: To determine the concentration of house dust mite (HDM) allergens, Der f 1 and group 2, on the skin and hair of dogs and whether associations exist between the presence of Der f 1 and group 2 allergens on the skin and hair of dogs and household and dog characteristics. ANIMALS: 63 pet dogs from 50 homes. PROCEDURE: Dogs were weighed and body surface area in square meters was determined. Skin and hair samples were obtained by vacuuming dogs. Collected dust was analyzed by use of standard ELISA techniques. RESULTS: HDM allergen was detected in 21 of 59 skin and hair samples. Presence of group 2 allergen on skin and hair of dogs was significantly associated with long hair, compared with short or medium length hair. Median house dust sample concentrations of Der f 1 and group 2 allergens were high in homes with dogs that had skin and hair samples that were positive for Der f 1 and group 2 allergens. Dogs with skin and hair samples that were positive for Der f 1 and group 2 allergens resided in homes with a high number of house dust samples that were positive for Der f 1, group 2, or both allergens and in homes with a mean house dust sample allergen concentration of > or =2 microg/g of dust. CONCLUSIONS AND CLINICAL RELEVANCE: Associations exist between environmental HDM allergen concentrations and HDM allergens on the skin and hair samples of dogs. Environmental allergen load is a major factor in accumulation of allergens on the skin and hair of dogs.  相似文献   
42.
Euthanasia of mature swine is challenging. Temporal and behind-the-ear locations are two sites that have been identified as alternatives to the more commonly used frontal placement. In stage one, the effectiveness of two penetrating captive bolt gun styles (cylinder or pistol) was evaluated using frontal, temporal, and behind-the-ear placement in anesthetized mature swine (n = 36; weight: 267 ± 41 kg). For stage one, when evaluating treatment efficacy by sex, the cylinder-style equipment was 100% effective in achieving death when applied to all cranial locations (frontal, temporal, and behind-the-ear) for sows; however, the pistol-style equipment was only 100% effective when applied at the behind-the-ear location for sows. For boars, the cylinder-style equipment was 100% effective when applied to the frontal and behind-the-ear location, but the pistol-style equipment was not effective for any cranial location in boars. Therefore, the pistol–frontal, pistol–temporal, pistol–behind-the-ear, and cylinder–temporal were not included for boars, and pistol–frontal and pistol–temporal were not included for sows in stage two. In stage two, commercial, mixed-breed, mature swine (n = 42; weight: 292 +/− 56 kg) were randomly assigned to one of four treatments based on the inclusion criteria described in stage one. A three-point traumatic brain injury (TBI) score (0 = normal; 1 = some abnormalities; 2 = grossly abnormal, unrecognizable) was used to evaluate six neuroanatomical structures (cerebral cortex, cerebellum, hypothalamus, thalamus, pons, and brain stem), and the presence of hemorrhage was also noted. All treatments were 100% effective in stage two. A significant interaction between gun style and placement was determined on predicting total TBI as the cylinder style produced a higher total TBI score compared with the pistol type of the magnitude of +2.8 (P < 0.01). The cylinder style tended to produce a greater TBI score than the pistol in the temporal location (+1.2; P = 0.08). No difference was noted for TBI score behind-the-ear between the cylinder- and pistol-style gun (P > 0.05). TBI tended to be less in boars compared with sows (−0.6; P = 0.08). Hemorrhage was observed in frontal, parietal, occipital, and temporal lobes. This study demonstrated that the cylinder-style captive bolt gun more effectively resulted in brain trauma and death compared with a pistol-style gun and the behind-the-ear and temporal placement showed promise as an alternative placement site for euthanizing mature pigs on-farm.  相似文献   
43.
A 2-year-old, castrated male Manx cat was presented for anorexia, obstipation, and straining to defecate. Imaging tests revealed a cystic mass associated with the descending colon. Three surgical explorations over several years were performed before complete resection of the cystic mass was achieved. Histopathology of the mass revealed normal colonic structures consistent with colonic duplication. Complete resection of a noncommunicating duplicate colon may allow successful treatment of this condition and resolution of associated clinical signs.  相似文献   
44.
45.
46.
47.
48.
From 1991 to 2003, 24 cases of larval cyathostominosis were diagnosed at postmortem in equids, 15 (63%) from 2001 to 2003. Cases occurred from September to May, the majority from October to December. Median age was 12 mo. Diarrhea, colic, and weight loss were common clinical signs. Hypoalbuminemia and microcytosis were consistent findings.  相似文献   
49.
50.
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