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   331篇
  免费   23篇
林业   3篇
农学   2篇
基础科学   2篇
  16篇
综合类   160篇
农作物   1篇
水产渔业   6篇
畜牧兽医   142篇
园艺   6篇
植物保护   16篇
  2023年   1篇
  2022年   4篇
  2021年   4篇
  2020年   7篇
  2019年   12篇
  2018年   11篇
  2017年   7篇
  2016年   6篇
  2015年   6篇
  2014年   9篇
  2013年   9篇
  2012年   7篇
  2011年   11篇
  2010年   15篇
  2009年   9篇
  2008年   35篇
  2007年   39篇
  2006年   42篇
  2005年   37篇
  2004年   6篇
  2003年   5篇
  2002年   7篇
  2001年   7篇
  2000年   8篇
  1999年   1篇
  1997年   1篇
  1996年   3篇
  1995年   3篇
  1993年   2篇
  1992年   2篇
  1991年   2篇
  1990年   5篇
  1988年   4篇
  1987年   3篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1979年   3篇
  1978年   1篇
  1976年   3篇
  1975年   1篇
  1972年   1篇
  1969年   1篇
  1967年   1篇
  1963年   1篇
  1937年   1篇
排序方式: 共有354条查询结果,搜索用时 31 毫秒
91.
OBJECTIVE: To compare efficacy and safety of paste formulations of firocoxib and phenylbutazone in horses with naturally occurring osteoarthritis. DESIGN: Randomized controlled clinical trial. ANIMALS: 253 client-owned horses with naturally occurring osteoarthritis. PROCEDURES: Horses were treated with firocoxib (0.1 mg/kg [0.045 mg/lb], PO, q 24 h) or phenylbutazone (4.4 mg/kg [2 mg/lb], PO, q 24 h) for 14 days. Physical examinations and lameness evaluations were performed prior to treatment and after 7 and 14 days. Clinical improvement was defined as a reduction of at least 1 lameness grade or a combined reduction of at least 3 points in scores for pain during manipulation or palpation, joint swelling, joint circumference, and range of motion. RESULTS: Proportion of horses clinically improved on day 14 for the firocoxib group (104/123 [84.6%]) was not significantly different from the proportion for the phenylbutazone group (103/119 [86.6%]). Proportion of horses that were improved on day 14 was significantly greater for horses treated with firocoxib than for horses treated with phenylbutazone with regard to score for pain on manipulation or palpation (P = 0.028), joint circumference score (P = 0.026), and range of motion score (P = 0.012), but not for overall lameness score or joint swelling score. No direct treatment-related adverse effects were detected during the study. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that overall clinical efficacy of a paste formulation of firocoxib in horses with naturally occurring osteoarthritis was comparable to efficacy of a paste formulation of phenylbutazone.  相似文献   
92.
93.
The aim of the study was to assess the effects of the anthelminthic, praziquantel, on the haematological and biochemical indices of the blood of common carp (Cyprinus carpio L.). Fish were divided into six groups: two groups received 30 mg kg−1 body weight (bw) of praziquantel, and two groups were given 50 mg kg−1 bw of praziquantel mixed into the heat-treated amyloid vehicle. Fish in the remaining two groups were given only the amyloid vehicle and were used as controls. Fish were examined either 24 or 96 h after administration. Praziquantel treatment was characterised by a significantly lower erythrocyte count, haemoglobin level, packed cell volume and total protein at both dose levels after 24 h compared with the controls, but these parameters were similar to the control values at 96 h. The activity of alanine aminotransferase (ALT) was significantly higher after 96 h in the treated groups, which could be attributed to slight hepatocyte damage caused by praziquantel. However, the differences between the treated and the control groups were not great, and we presumed that they were reversible.  相似文献   
94.
The 1996 Food and Agriculture Organization’s (FAO) ‘Guidelines on the Precautionary Approach to Fisheries and Species Introduction’ raise important issues for fisheries managers, but fail to prescribe an approach for risk management. The distinguishing characteristics of the ‘precautionary approach’ are the inclusion of uncertainty and ‘an elaboration on the burden of proof’. The FAO precautionary approach emphasizes that managers should be risk‐averse, but does not provide tools for determining the appropriate degree of risk aversion. Consequently, application of the precautionary approach often leads to decision‐making based on ad hoc safety margins. These safety margins are seldom chosen with explicit consideration of trade‐offs. If the emphasis was shifted to choosing between competing uncertainties, then managers could manage risk. By attempting to avoid risk, managers may gain exposure to other risks and perhaps miss valuable opportunities. We place fishery management problems within the rubric of ‘real investment’ problems, and compare and contrast the consideration of risk by alternative investment frameworks. We show that traditional investment frameworks are inappropriate for fishery management, and furthermore, that traditional precautionary approaches are arbitrary and without basis in decision theory. Quantitative decision‐making techniques, such as formal decision analysis (FDA), enable integration of competing hypotheses that help alleviate burden‐of‐proof issues. These techniques help analysts consider sources of uncertainty. FDA, however, can still be subject to arbitrary safety margins because such analyses often focus on determining which strategies best achieve, or avoid, targets that have been established without complete consideration of trade‐offs. A managerial finance approach, real options analysis (ROA), is an alternative and complementary decision‐making technique that enables managers to compute precautionary adjustments that couple the size of the ‘safety margin’ with the amount of uncertainty, thereby optimizing risk exposure and avoiding the need for arbitrary safety margins. We illustrate the advantages of an approach that combines FDA and ROA, using a heuristic example about a decision to re‐introduce Atlantic salmon (Salmo salar L.) into Lake Ontario. Finally, we provide guidance on applying ROA to other fishery problems. The precautionary approach requires that managers consider risk, but considering risk is not the same as managing it. Here ROA is useful.  相似文献   
95.
96.
OBJECTIVE: To compare the peak force required for failure of hand-tied laparoscopic slipknot ligatures. STUDY DESIGN: In vitro mechanical evaluation of suture material/knot combinations. Sample POPULATION: Four hand-tied laparoscopic slipknots were studied. Three suture materials and 2 suture sizes were evaluated. Twenty samples of each group were tested, for a total of 400 samples. METHODS: The 4S modified Roeder, modified Roeder, and Weston and Brooks laparoscopic slipknots using 0 polyglyconate, 0 polyglycolic acid, 1 polyglyconate, and 1 polydioxanone (PDS) were tested. A vertical distracting force (5 mm/s) was applied until failure. Mean peak force to failure was obtained for each suture material, size, and knot combination. RESULTS: Mean (+/-SEM) peak force to failure of hand-tied ligatures ranged from 156.8+/-9.1 N to 4.8+/-.4 N. The 4S-modified Roeder had the highest mean peak force to failure. Ligatures tied with polyglyconate and size 1 suture had the highest mean peak force to failure. CONCLUSIONS: The 4S-modified Roeder was significantly and consistently stronger than the other slipknots. Polyglyconate was superior to other suture materials. The 1 polyglyconate had the highest mean peak force to failure followed by 0 polyglyconate that exceeded the 1PDS. CLINICAL RELEVANCE: The 4S-modified Roeder slipknot using 1 polyglyconate has the greatest breaking strength of sutures tested and should be considered when performing laparoscopic ligatures.  相似文献   
97.
ABSTRACT Structural solarization of greenhouses for sanitation by closing them involves dry heating to 60 degrees C and higher with a consequent low relative humidity (RH) ( approximately 15%), thus requiring an extended period for thermal inactivation of pathogens. In an attempt to enhance pathogen control by increasing moisture during the hot hours of the day, various regimes of inoculum moistening were studied. However, wetting inoculum of Fusarium oxysporum f. sp. melonis and F. oxysporum f. sp. radicis-lycopersici resulted in less effective pathogen control compared with that of dry heating. Fifty percent effective dose (ED(50)) values of thermal inactivation of wetted and dry inoculum for the former pathogen were 18 and 7 days, respectively, and for the latter, a respective 9 and 4 days. This was because wetting resulted in inoculum cooling due to evaporation, which eventually led to its drying. A model describing the drying of wet inoculum in a wetted greenhouse, based on the fact that there was an approximately 10 degrees C difference between greenhouse and ambient temperatures, was proposed. A double-tent system reduced this difference to 1 to 2 degrees C, reduced moisture loss, and led to improved inoculum inactivation of F. oxysporum f. sp. radicis-lycopersici. Thus, the ED(50) value of thermal inactivation was reduced from 15 days to 1 day, because this system provided both high temperature ( approximately 60 degrees C) and high RH ( approximately 100%), resulting in effective wet heating.  相似文献   
98.
OBJECTIVE: To evaluate the outcome of horses with large fragments of the extensor process of the distal phalanx that were removed by use of arthrotomy. DESIGN: Retrospective study. ANIMALS: 14 horses with large fragments of the extensor process of the distal phalanx. PROCEDURE: Medical records for horses with large fragments of the extensor process that were removed by use of arthrotomy were reviewed. Data retrieved from medical records included signalment, use of horse, affected limb, lameness history, lameness examination findings, radiographic findings, surgical technique, and outcome. Follow-up evaluation was obtained by telephone interview. RESULTS: Most affected horses were < 5 years old and had a history of chronic lameness. Lameness grade ranged from 1/5 to 4/5. Fragments involved 20 to 45% of the dorsopalmar articular surface of the distal phalanx. Eight of 14 horses had a successful outcome. Outcome was not associated with age, duration or severity of lameness, or fragment size. CONCLUSIONS AND CLINICAL RELEVANCE: Despite involvement of a large portion of the articular surface and use of arthrotomy, joint instability and permanent soft tissue injury was not a problem in most horses. Outcome may be improved by selection of horses with lameness of < 2 years' duration and careful management after surgery. A fair prognosis may be anticipated for removal of large fragments of the extensor process via arthrotomy.  相似文献   
99.
Mexico is considered by different international organizations as a country where the bovine tuberculosis is an endemic problem. However, there are important and consistent improvements in eradicating the disease by the implementation of government policies and with the livestock organization support. The current situation of the program shows good results regarding decreasing the prevalence, and as a consequence, the risk of this disease for public health and animal health, as well as the improvement in animal production and international and national trade. Today, the bovine tuberculosis distribution is almost known in Mexico. In addition, a series of controls and indicators have been established, which allow maintain consistency and reliability in the data that are managed and analyzed.  相似文献   
100.
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