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   326篇
  免费   3篇
  国内免费   2篇
林业   22篇
农学   14篇
基础科学   1篇
  64篇
综合类   24篇
农作物   11篇
水产渔业   17篇
畜牧兽医   147篇
园艺   2篇
植物保护   29篇
  2023年   1篇
  2022年   6篇
  2021年   12篇
  2020年   3篇
  2019年   3篇
  2018年   7篇
  2017年   6篇
  2016年   9篇
  2015年   8篇
  2014年   13篇
  2013年   21篇
  2012年   18篇
  2011年   20篇
  2010年   11篇
  2009年   11篇
  2008年   26篇
  2007年   24篇
  2006年   25篇
  2005年   14篇
  2004年   19篇
  2003年   25篇
  2002年   17篇
  2001年   11篇
  2000年   6篇
  1999年   2篇
  1998年   4篇
  1997年   1篇
  1993年   1篇
  1992年   1篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有331条查询结果,搜索用时 46 毫秒
91.
OBJECTIVE: To determine whether small intestinal ischemia and reperfusion induces bacterial translocation and proinflammatory cytokine response in either the systemic or portal circulation in dogs. ANIMALS: 17 healthy adult Beagles. PROCEDURE: The superior mesenteric artery (SMA) was occluded for 0 (group-3 dogs), 30 (group-1 dogs), or 60 (group-2 dogs) minutes, followed by reperfusion for 180 minutes; serum lactate and endotoxin concentrations and tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 activities in the systemic and portal circulation and intramucosal pH were measured at various time points. RESULTS: In group-2 dogs, TNFalpha activity was found to be significantly increased in the portal circulation, peaking at 60 minutes of reperfusion; TNF-alpha activity, in the systemic circulation, gradually increased from 60 minutes of reperfusion to the end of the experiment; however, the increase was not significant. In group-1 and -2 dogs, IL-6 activities significantly and gradually increased in the systemic and portal circulation during the reperfusion phase, and the magnitude of these increases was dependent on the duration of the ischemic phase. There were no significant changes in IL-1beta activity or endotoxin concentration in any dog group. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the our study indicate that intestinal ischemia and reperfusion leads to significant increases of the circulating TNF-alpha and IL-6 activities, depending on the duration of the ischemia phase, in the absence of detectable endotoxin in the circulation. This finding suggests that intestinal ischemia and reperfusion induces a systemic proinflammatory cytokine response in dogs.  相似文献   
92.
In horses with chronic laminitis, an abnormal horny structure called lamellar wedge, is generated between the hoof wall and the laminar epidermis. To be able to manage horses with chronic laminitis correctly, more information about the pathological state of this abnormal horn is required. The aim of this study was to collect and analyze objective morphological data about the abnormal horn in order to understand its morphology and development. In the study, the abnormal horn was grossly visible on the sagittal hoof section from approximately 20 days after the onset of disease. In the histological observations, the structural characteristics of this abnormal horn were similar to the white line tissue, suggesting it is an ectopic white line. Mean value of the cross-sectional area of the abnormal horn against the distal phalanx section area (A/D) was 0.29 cm(2) SD +/- 0.14 and it finally showed an eight-fold increase over the mean value of normal white line section area against the distal phalanx section area. In conclusion, a large amount of the ectopic white line is thought to be finally able to inhibit normal hoof wall growth, so that it should be resected at the optimum time when would be after one month from the onset of the disease.  相似文献   
93.
 Green fluorescent protein (GFP)-marked Fusarium oxysporum f. sp. melonis and nonmarked F. oxysporum f. sp. fragariae were stained with neutral red. The neutral red stained vacuoles of the fungi without disturbing GFP fluorescence in the cytoplasm. GFP-marked fungi showed fluorescent hyphae with dark-stained vacuoles, whereas nonmarked fungi were detected as nonfluorescent hyphae with dark-dotted vacuoles. Root colonization by these two fungi was monitored using this method. Microconidia attached similarly to the root surface and elongated vegetative hyphae. Only the pathogenic fungi invaded, causing necrosis at the inoculation site. Thus, the present method enabled us to track simultaneously the various formae speciales of F. oxysporum colonizing the root surface. Received: March 25, 2002 / Accepted: September 27, 2002  相似文献   
94.
Due to the recent outbreak of avian influenza, transportation of frozen canine semen with egg yolk has been sharply restricted. Thus, there is urgent need to develop a novel egg yolk-free extender for freezing canine spermatozoa. In the present study, the effect of using skim milk/glucose (SG)-based extender without egg yolk on the motility and fertilizing capacity of canine spermatozoa frozen-thawed in the presence of glycerol was examined. There was a tendency for the proportion of motile spermatozoa exposed to SG-based extender for 3 h to be higher than that exposed for 1 h, but the difference was not significant. The motility and other viability parameters of canine spermatozoa after thawing were similar to those obtained with an egg yolk-based extender. When spermatozoa frozen with SG-based extender containing glycerol after 3 h exposure were transcervically inseminated into 2 recipient bitches, a total of 6 pups were obtained. These results suggest that a simple extender composed of skim milk, glucose and glycerol is useful for cryopreservation of canine spermatozoa, which may contribute to improved exchange of genetic material and efficient production of companion and working dogs, such as guide dogs for the blind.  相似文献   
95.
Non-surgical embryo transfer is a promising method for improving efficiency in the pork industry and also for biotechnology applications, such as in vitro embryo production, transgenesis and cloning. Several groups have reported successful piglet production using an artificial insemination catheter or flexible catheter designed for this procedure; however, the efficiency of the technique is still low. The critical points that need to be addressed in order to improve this procedure are (1) the embryo deposition site and (2) volume of transfer medium associated with the embryos; however, the latter has not yet been examined systematically. In the present study, we evaluated the effect of the volume of non-surgical embryo transfer medium on the ability of porcine embryos to survive to term by using a recently produced flexible catheter. The catheter consists of a guide and an injector. Blastocysts 200-230 mum in diameter were collected from donor gilts and transferred to recipient gilts. The time required for the completion of embryo transfer using this catheter was 14.6 +/- 3.9 min. The tip of the injector was determined by laparotomy to be located in a uterine horn 20-30 cm anterior from the branching point of the uterus body. We transferred 17.0-17.3 embryos with different volumes of medium (1.6, 3.2 and 10 ml) into each of 5, 4 and 4 recipients, respectively, and pregnancy was confirmed in 4, 3 and 1 of these recipients, respectively. Three recipients in the 1.6 ml group farrowed a total of 19 piglets (4, 5 and 10 piglets, respectively). These results suggest that successful non-surgical embryo transfer is affected by the volume of transfer medium.  相似文献   
96.
A set of N-(4-difluoromethoxybenzyl)pyrimidinamines with various substituents at the 4- and 5-positions of the pyrimidine ring and at the benzyl position were prepared, and their fungicidal activities against wheat brown rust, Puccinia recondita, and barley powdery mildew, Erisiphe graminis, were measured. Variations in each of these activities were quantitatively analysed by the use of physicochemical substituent parameters and a regression analysis. Each of these activities was parabolically correlated with the steric bulkiness of the pyrimidine substituents and with the bulkiness or the hydrophobicity of the benzylic substituents. © 1999 Society of Chemical Industry  相似文献   
97.
Seven species of bacteria were isolated and identified from ponded sugi (Cryptomeria japonica D. Don) logs, and six species showed potent wood-degrading activities. To evaluate the effects of these isolated bacteria on the drying and anatomical characteristics of wood, small fresh blocks of sugi were immersed in water suspensions containing bacteria for 1–7 months. The permeability and drying properties were evidently improved. Most of the encrusting substances adhering to the cell lumens and the pit chambers were removed, and the pit membranes were destroyed. These anatomical changes due to bacterial activity were assumed to improve the permeability of sugi wood.Part of this report was presented at the 40th annual meeting of the Japan Wood Research Society, Tsukuba, April 1990; the 41st annual meeting of the Japan Wood Research Society, Matsue, April 1991; and the IUFRO XX World Congress, Tampere, August 1995  相似文献   
98.
99.
The effect of anaerobic conditions on acetate ester biosynthesis in ripened banana pulp was investigated. Incubation of the pulp in less than 1% O(2) resulted in a significant reduction in the formation of ethyl acetate. Regardless of the presence of a large amount of endogenous ethanol and the remaining exogenous isobutyl alcohol after complete anaerobic incubation with the pulp, the production of acetate ester decreased. The effect of addition of pyruvate, isobutyl alcohol, acetate, and methyl hexanoate on acetate ester formation in 100% N(2) was also investigated. The addition of pyruvate and isobutyl alcohol to the pulp gave lower acetate esters in N(2) than in air, whereas the pulp incubated with acetate and isobutyl alcohol produced more acetate ester in both conditions. Therefore, the lack of acetyl CoA, or more precisely acetate, in the tissue is the main reason for the inhibition of acetate ester formation under anaerobic conditions. The activity of beta-oxidation measured by incubation with methyl hexanoate was detected only in the samples incubated in air. The formation of acetyl CoA, derived from pyruvate through mitochondria and through beta-oxidation, was inhibited by anaerobic conditions, which suggests that mitochondrial activity and/or beta-oxidation are essential for ester biosynthesis.  相似文献   
100.
在田间条件下 ,采用 1 5 N微区法 ,研究中、后期施肥对稻株体内氮素积累与分配的影响。结果表明 :1随着氮肥施用时期的推迟 ,茎、叶等营养器官干物重明显下降 ,而穗干物重下降幅度较小 ,且其占全株干重的比例提高。 2稻株含氮率随氮肥施用时期推迟有提高的趋势 ;与施促花肥相比 ,施用粒肥绿叶及叶鞘中的氮素积累量明显下降 ,而茎、穗中氮累积量则略有增加。 3在稻株不同器官中 ,穗、绿叶 (包括叶鞘 )对穗粒肥氮的积累能力最强 ,但随穗粒肥施用时期的推迟 ,穗部积累的肥料氮及其占全株的比例增加 ,而绿叶则呈相反的趋势。 4稻株对促花肥、保花肥、粒肥氮的回收率 (利用率 )分别为 32 .7%、30 .0 %及 2 3.7%。  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