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   306篇
  免费   8篇
林业   7篇
农学   28篇
  12篇
综合类   17篇
农作物   23篇
水产渔业   24篇
畜牧兽医   174篇
植物保护   29篇
  2017年   5篇
  2016年   2篇
  2015年   5篇
  2013年   2篇
  2012年   2篇
  2011年   8篇
  2010年   7篇
  2009年   11篇
  2008年   7篇
  2007年   7篇
  2006年   4篇
  2005年   3篇
  2003年   2篇
  2002年   2篇
  1999年   3篇
  1998年   10篇
  1997年   14篇
  1996年   13篇
  1995年   11篇
  1994年   4篇
  1993年   8篇
  1992年   9篇
  1991年   7篇
  1990年   19篇
  1989年   15篇
  1988年   13篇
  1987年   11篇
  1986年   9篇
  1985年   6篇
  1984年   10篇
  1983年   5篇
  1982年   9篇
  1981年   8篇
  1980年   5篇
  1979年   4篇
  1978年   6篇
  1977年   4篇
  1976年   5篇
  1975年   3篇
  1971年   3篇
  1969年   2篇
  1967年   2篇
  1960年   3篇
  1958年   4篇
  1957年   2篇
  1956年   2篇
  1955年   3篇
  1954年   2篇
  1946年   1篇
  1933年   1篇
排序方式: 共有314条查询结果,搜索用时 15 毫秒
61.
为了探寻不同发育期朝鲜球坚蚧的有效防治新措施,根据朝鲜球坚蚧不同发育阶段的形态特征和生物学习性,对不同龄期的若虫采取刮皮涂干、树干注射和常规喷雾等措施进行防治.试验结果表明;在施药方法上,刮皮涂干和常规喷雾是最为适用的;在药效方面,在1龄若虫期喷雾施用的几种药剂中醋盐合剂对1龄若虫的喷洒防效达到了90%以上.通过施用脱叶剂处理叶片的方法来防治2龄若虫,试验所设3种浓度的脱叶剂均能间接起到防治作用,其效果均达到了95%以上.在3龄若虫期喷雾施用的几种药剂中95%酒精合剂的喷洒防效达到了90%以上.涂干防治3龄若虫期供试的几种药剂中,20%吡虫啉可溶性液剂1∶10的稀释液防效达到了90%以上.  相似文献   
62.
This study aims at quantifying the effects of defoliation on seed production and germination in Buddleja davidii , and determining the potential for reducing the invasive success of the species. The effects of defoliation on seed production and germination at the flower spike and plant levels were investigated for control plants and plants that were defoliated by 66% at monthly intervals from mid-summer (January) to mid-autumn (April). Seed samples for germination were collected in late autumn (May). Defoliation reduced flower spike number per shoot, seed number per flower spike and average seed mass by 9%, 22% and 13% and 30%, 33% and 17% on main and side shoots, respectively. In contrast, emergent leaf area per shoot in the defoliated plants exceeded that for the control plants by 89%. The ratio of total seed mass per plant/emergent leaf area per shoot was significantly lower in the defoliated compared with the control plants by 50%. Defoliation did not affect the timing or rate of seed germination. Defoliation of B. davidii resulted in a marked decrease in reproductive capacity, consistent with the priority allocation of resources to compensational leaf area growth.  相似文献   
63.
Perennial ryegrass cv. S23 was preserved by fermentation (C), or with the addition of 8.7 1 formalin (35% w/w formaldehyde) per t fresh herbage (F) or of 9.0 1 equal mixture (by vol.) of formalin and formic acid (85% w/w solution) per t fresh herbage (FF). These three silages comprised the treatments in a three-period, crossover design in which urea (u) was given at the rate of 20 g per kg dietary DM to half the animals. Twelve calves were allocated to the treatment sequences when they were approximately 12 weeks of age from within groups which had previously received diets with or without urea. Calves ate significantly (P< 0.001) less of silages F or FF than of silage C when each was offered alone, but when urea was given, intakes of silages F and FF were significantly (P < 0.001) increased such that the intakes of all three silages with urea were similar (23.6, 19.6, 19.3, 24.2, 24.2, 24.7 ± 0.51 g DM per kg LW for C, F, FF, Cu, Fu and FFu, respectively). Significantly (P<0.01) more of the DM in silage C was digested than in F or FF and the addition of urea significantly (P<0.05) increased the digestibility of DM from silage FF only (73.8, 71.3, 69.8, 74.6, 70.7, 72.5 ± 0.72% for C, F, FF, Cu, Fu and FFu, respectively). When the silages were given alone, calves spent longer eating and ruminating per kg DM ingested with F or FF than with C. The time spent on F and FF was significantly (P<0.01) reduced by the addition of urea (303, 388, 411, 297, 299, 290 ± 18.9 min per kg DM ingested for C, F, FF, Cu and Fu and FFu, respectively). The results presented suggest that urea partially alleviated the reduction in voluntary intake by calves given herbage preserved using formalin, but the mode of action was not clear.  相似文献   
64.
65.
66.
A large tumour present on the proximal tibia of a Bull Mastiff dog was diagnosed on histological appearance as a Malignant Fibrous Histiocytoma. These tumours, rarely identified in domestic animals, but well recognised in humans, are typically pleomorphic sarcomas with histiocytic and fibroblastic differentiation. Less commonly, one cell type predominates. In this case there was prominent histiocytic differentiation.  相似文献   
67.
A case of generalised protothecosis in a Collie dog is discussed. A long-standing history of severe colitis was the major clinical sign. Dissemination to many organs was confirmed histologically. Possible pathogenesis is discussed along with a review of the literature. The possibility of a breed disposition in Collie dogs is discussed. The organisms are ubiquitous in the environment and generalised disease suggests the possibility of immune competence.  相似文献   
68.
A prospective study was undertaken to compare the analgesic effect of intra-articular bupivacaine, morphine, or saline in the 24-hour period following cranial cruciate ligament repair in dogs. Thirty-six clinical patients with ruptured cranial cruciate ligaments were randomly assigned to one of three groups. After surgical stabilization, and before skin closure, an intra-articular injection was given; group one (n = 12) received 0.5% bupivacaine HCl at 0.5 mL/kg, group two (n = 12) received morphine at 0.1 mg/kg diluted with saline to a volume of 0.5 mL/kg, and group three (n = 12) received saline at 0.5 mL/kg. Heart rate, respiratory rate, mean arterial blood pressure, cumulative pain score, visual analog pain score, and pain threshold test on both stifles were recorded preoperatively and at 0 to 6 and 24 hours postoperatively. Surgeons and pain scoring investigators were unaware of the intra-articular medication given. Supplemental analgesia, if needed, was provided in the postoperative period according to subjective assessment of patient discomfort. Postoperative pain scores were lowest in the bupivacaine group and highest in the saline group. Pain threshold, measured by applying calibrated loads to the knee, was higher postoperatively in the bupivacaine group than in the saline group. Dogs in the morphine and bupivacaine groups required less supplemental analgesia than dogs in the saline group. The local provision of analgesia reduces the need for systemic drugs with potential side effects. Both intra-articular morphine and intra-articular bupivacaine provided better postoperative analgesia than intra-articular saline, with intra-articular bupivacaine showing the greatest effect.  相似文献   
69.
Primary ocular sarcomas in the cat   总被引:1,自引:0,他引:1  
Primary ocular sarcomas were diagnosed following enucleation (12) or necropsy (one) in 13 cats over an eight year period. Twelve of the 13 cats were males; ages of affected animals were seven to 15 years, with a mean of 12. Five of the cats had a history of previous trauma and six others had a history of chronic uveitis. Morphologically the neoplasm was comprised of undifferentiated spindle cells and appeared to arise in the anterior uvea. The cancer was quite aggressive, with extension into adjacent tissues and/or distant metastases commonly encountered. Seven of 12 cats experienced confirmed tumour related deaths within months following enucleation and one was humanely destroyed at the time of original presentation.  相似文献   
70.
The effects of the imposition and timing of a rest period from continuous sheep stocking, for a conservation cut, on white clover presence in forty perennial ryegrass/white clover associations were studied over two full grazing seasons. Each association consisted of one grass variety along with one white clover variety, the grasses being diploid and tetraploid ryegrasses from each of five maturity groups and the white clovers from each of four leaf size categories. The presence of white clover within each association was assessed at the beginning and end of both seasons by means of a 0–64-m2 quadrat subdivided into 100 squares, each 80 mm × 80 mm, the number of squares in which any part of a white clover plant was visible being recorded. Complementary point quadrat data were also collected. Although continuous sheep stocking did not necessarily have an adverse effect on white clover presence, a July to mid-August rest period increased white clover proportions in the swards (means: unrested, 48–1; April to late May rest, 32.7; July to mid-August rest, 67.3 - s.e.d. 7.59; P < 0.05) the benefit increasing with increasing white clover leaf size. The early rest period (April to late May) reduced white clover presence and the late rest period (July to mid-August) increased white clover presence, these effects being intensified with increasing white clover leaf size (very large-leaved clover: unrested, 20.6; April to late May rest, 8.3; July to mid-August rest, 41.1 and small-leaved clover: unrested, 96.3; April to late May rest, 84.8; July to mid-August rest, 97 - s.e.d. 9.2; P <0001). Tetraploid ryegrass/white clover associations had consistently and significantly more white clover than diploid ryegrass/white clover associations of similar ryegrass maturity group (tetraploid, 53.4; diploid 44.8 - s.e.d. 2.12; P <0.001) and associations with early maturing ryegrass contained more white clover than those with late maturing ryegrasses, the effect of maturity group being greater than that of ploidy. Overall, white clover presence increased with increasing openness of grass growth habit.  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