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   407篇
  免费   45篇
林业   39篇
农学   21篇
基础科学   1篇
  59篇
综合类   10篇
农作物   33篇
水产渔业   44篇
畜牧兽医   184篇
园艺   16篇
植物保护   45篇
  2023年   4篇
  2022年   17篇
  2021年   22篇
  2020年   18篇
  2019年   26篇
  2018年   17篇
  2017年   18篇
  2016年   30篇
  2015年   19篇
  2014年   17篇
  2013年   25篇
  2012年   28篇
  2011年   43篇
  2010年   18篇
  2009年   17篇
  2008年   18篇
  2007年   17篇
  2006年   13篇
  2005年   11篇
  2004年   13篇
  2003年   8篇
  2002年   11篇
  2001年   6篇
  2000年   2篇
  1999年   2篇
  1998年   5篇
  1997年   2篇
  1996年   1篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1980年   1篇
  1969年   1篇
  1967年   1篇
排序方式: 共有452条查询结果,搜索用时 0 毫秒
131.
The objective of this study was to evaluate the inclusion of increasing levels of a commercial mix of essential oils (EOs) from cashew (Anacardium occidentale) and castor bean (Ricinus communis) as an additive in diets for Nile tilapia. Thus, 240 juveniles with an initial weight of 35.06 ± 1.02 g were distributed in a completely randomized design (four treatments and six replicates) in 24 cylindrical‐tapered tanks; the fish were fed for 60 days, four times a day, diets containing increasing levels of EO (0.10, 0.15 and 0.20%) and a control diet (without the additive). After the experimental period, the animals were desensitized, and an aliquot of blood was collected for the biochemical analysis; they were subsequently euthanized for the evaluation of productive performance and fillet chemical composition. No significant differences (p > .05) were observed in the analyses of productive performance, fillet chemical composition, and triglycerides, VLDL, total proteins, urea and glucose. However, significant differences (p < .05) were observed in the analyses of total cholesterol, HDL and LDL. Inclusion above 0.15 of the additive showed an improvement in the levels of lipoprotein carriers, increasing HDL levels and decreasing LDL values, without interfering with the fish productive performance.  相似文献   
132.
Testicular vitrification is an alternative to preserve the genetic material of pre-pubertal animals. However, there are few studies on post-vitrification warming. Hence, the aim was to compare the influence of different warming temperatures on vitrified testicular fragments from pre-pubertal cats. The testicles were fragmented and divided into a control group (non-vitrified) and vitrified, using an association between dimethylsulphoxide and glycerol. The vitrified fragments were warmed at 50, 55 and 60°C/5 s. Morphological and morphometric evaluations were carried out using classical histology. Afterwards, the mitochondrial activity was evaluated using Rhodamine 123. The data were expressed in mean and standard error. The differences were considered significant when p < .05. In the histomorphological analysis, the testicular fragment presented seminiferous tubules with poorly developed germinal epithelium, compatible with pre-pubertal animals. The group warmed at 50°C presented similar to the control regarding the maintenance of the integrity of the tubules and cells, without stromal rupture and lamina propria alteration, as well as regarding the maintenance of the junctions between the cells. The group warmed at 55°C showed reduction of the cell junctions, and the one warmed at 60°C had increased detachment of the basement membrane (p < .05). The warming caused a reduction in the tubular diameter inversely proportional and progressive to the increase in temperature, with the highest diameter in the control group and the lowest in the 60°C group. The control group showed a lower incidence of Rhodamine 123, followed in ascending order of the warmings at 55 and 60°C. The higher mitochondrial activity was obtained with 50°C, showing an increase of the metabolic cell function at this temperature. It was concluded that the testicular fragment of pre-pubertal cats presents a better preserved morphology, morphometry and viability when warmed at 50°C.  相似文献   
133.
Plant Foods for Human Nutrition - The consumption of loquat fruits is highly appreciated for their carotenoid content and valuable sensory notes, but it is limited due to the low shelf-life. An...  相似文献   
134.
Osteoarthritis (OA) of the metacarpophalangeal joint is the most common articular disease in polo ponies leading to early retirement. A biomarker that would discriminate between pathological and physiological changes secondary to exercise could be helpful in OA prevention. The aim of this study was to investigate the effects of polo training on synovial fluid biomarkers of inflammation and cartilage turnover in polo ponies of different skill levels. Synovial fluid samples were collected from metacarpophalangeal joints of polo ponies before and during the polo season (320 d). Nucleated cells, soluble protein, prostaglandin E2 (PGE2), glycosaminoglycans (GAG), and urea were measured. The main synovial fluid GAG are chondroitin sulphate (CS, ~25 μg/mL) and hyaluronic acid (HA, ~400 μg/mL). After a polo match, a transitory increase in protein and PGE2, but not CS and HA, occurred (expressed as urea ratio), returning to basal levels in 24 h. During the polo season, the number of synovial fluid nucleated cells was always in the normal range. Increases in protein and HA occurred during the initial 40 to 80 d, returning to basal levels afterwards. In contrast, in polo prospects the concentration of CS steadily increased during the season. Long-term follow-up revealed that the synovial fluid CS was significantly higher in polo ponies that developed joint diseases within 24 months following our study. In conclusion, CS seems to be an early marker of articular cartilage damage.  相似文献   
135.
The mechanisms of action by which aluminium affects phosphate absorption were evaluated in Stylosanthes guianensis (aluminium‐sensitive) and Stylosanthes macrocephala (aluminium‐tolerant), through kinetic studies with aluminium in pre‐ and co‐treatment. Multiphasic and cooperative models of ions absorption were tested. In the absence of aluminium, S. guianensis, a specie which normaly requires more phosphorus, showed lower rates of phosphate absorption, which was attributed to slower turnover of the carrier. In S. guianensis, the higher rates of absorption may be related to higher turnover and/or higher concentration of the carrier in the roots. Both species showed negative correlation in the absorption of phosphate, but it was more pronounced in S. guianensis. The effect of aluminium seems to be related to the decreased capacity of the carrier to associate with the ion. There may also be a reduction in the turnover of the carrier, which appears to be more pronounced in the tolerant species, reducing phosphate absorption. In the presence of aluminium, the association becomes positive or approaches Michaelis‐Menten kinetics in both species. However, the absorption of phosphate is not increased since there is also a reduction in the capacity of the carrier to bind to the ion.  相似文献   
136.
This experimental controlled study was performed to evaluate the composition of autologous processed plasma (APP), and the effects of APP intra-articular injection into healthy equine metacarpophalangeal joints. The effects on joints were analysed with a short-phase protocol and a prolonged-phase protocol using saline-injected joints as controls. For the short protocol, horses received one intra-articular APP injection. Synovial fluid samples were collected prior to the injection and 3, 6, 24, 48, and 16 h after treatment. For the prolonged protocol, the joints received three weekly injections of APP, and samples were collected at 0, 7, 14, 21, and 28 days before APP administration. IL1-ra level was found to be increased in APP compared to plasma. Upon intra-articular administration of APP, transient (up to 24 h) increases in white blood cell (WBC) counts along with elevated protein and prostaglandin E2 (PGE2) concentrations were observed in the treated joints. Over the 28-day observation period, APP did not elicit changes relative to baseline levels, but WBC counts, PGE2 and chondroitin sulphate concentrations were lower than those found in the control. In conclusion, APP intra-articular injection induced a mild and transitory inflammatory response but no inflammation reaction was observed over a longer period of treatment and observation.  相似文献   
137.
138.
Abstract: A 14‐year‐old female spayed Golden Retriever was presented to the University of Florida's Veterinary Medical Center with history of lymphoplasmacytic gastroenteritis, intermittent vomiting, watery diarrhea, and weight loss for over a year. CBC, biochemical profile, and urinalysis were within reference intervals. Abdominal ultrasonographic examination revealed mesenteric and jejunal lymphadenopathy and hyperechoic hepatic nodules. Cytologic examination of the enlarged lymph nodes revealed loosely cohesive cells with moderate nuclear pleomorphism and rare punctate eosinophilic cytoplasmic granules. The cytologic interpretation was metastatic neuroendocrine neoplasia. On surgical exploration, a mass was detected in the right lobe of the pancreas. Histologic evaluation determined the mass to be an islet cell tumor. Approximately 98% of cells were positive by immunolabeling for pancreatic polypeptide (PP), and only rare cells were positive for insulin or somatostatin. All cells were negative for glucagon, gastrin, vasoactive intestinal polypeptide, protein gene product 9.5, synaptophysin, and chromogranins A and B. Pancreatic tumors that primarily produce PP are rare in dogs, and this is the first report of both the cytologic and histologic features of an islet cell tumor predominantly secreting PP. Clinical signs for these tumors are typically absent or nonspecific; signs may include watery diarrhea, as noted in this dog, although the diarrhea may have resulted from lymphoplasmacytic gastroenteritis. Additional case studies are needed to further characterize the cytomorphologic features and clinical presentation of PP‐secreting islet cell tumor, or polypeptidoma, in dogs.  相似文献   
139.
140.
Apparent digestibility coefficients (ADCs) of amino acids, crude protein, gross energy, and dry matter of canola meal, corn gluten feed, fish offal meal, shrimp and fish offal meal, poultry by‐product meal, and hydrolyzed feather meal were determined for channel catfish, Ictalurus punctatus. Experimental diets contained 30% test ingredient, 69.5% casein‐based reference diet, and 0.5% chromic oxide. Groups of 20 fish (102.45 g) were fed the experimental diets twice a day at 3.5% body weight. Fecal samples were collected in triplicate daily at 0000 h and 0600 h after settlement into collection devices. Shrimp and fish offal meal and corn gluten feed presented significantly lower (P < 0.05) ADC for dry matter (59.5 and 39.3%) suggesting their low value as feedstuffs for catfish feeds. Although ADC values for crude protein were above 80% for all the test ingredients, amino acid digestibility varied significantly, except for histidine whose ADC remained constant regardless of the protein source. Lysine was the first limiting amino acid in most of the test ingredients, except in fish offal meal and poultry by‐product meal. Among the protein sources tested, only fish offal meal and poultry by‐product meal met channel catfish amino acid requirements for a 28% digestible protein grow‐out diet.  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