全文获取类型
收费全文 | 1103篇 |
免费 | 67篇 |
国内免费 | 2篇 |
专业分类
林业 | 31篇 |
农学 | 39篇 |
基础科学 | 5篇 |
149篇 | |
综合类 | 139篇 |
农作物 | 58篇 |
水产渔业 | 34篇 |
畜牧兽医 | 643篇 |
园艺 | 15篇 |
植物保护 | 59篇 |
出版年
2023年 | 6篇 |
2021年 | 18篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 16篇 |
2017年 | 23篇 |
2016年 | 17篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 42篇 |
2012年 | 42篇 |
2011年 | 54篇 |
2010年 | 44篇 |
2009年 | 25篇 |
2008年 | 46篇 |
2007年 | 49篇 |
2006年 | 46篇 |
2005年 | 53篇 |
2004年 | 43篇 |
2003年 | 50篇 |
2002年 | 71篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 25篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 20篇 |
1991年 | 25篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 12篇 |
1974年 | 9篇 |
1972年 | 5篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 6篇 |
1943年 | 5篇 |
排序方式: 共有1172条查询结果,搜索用时 15 毫秒
11.
Preliminary investigation comparing a detomidine continuous rate infusion combined with either morphine or buprenorphine for standing sedation in horses
下载免费PDF全文
![点击此处可从《Veterinary anaesthesia and analgesia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
12.
R. L. Miller S. Van Lelyveld J. Warland J. M. Dobson R. D. Foale 《Veterinary and comparative oncology》2016,14(4):361-370
This retrospective case series evaluates survival outcome of 94 dogs with high metastatic risk mast cell tumours (MCT). Patients were treated with a cytotoxic chemotherapy protocol or the tyrosine kinase inhibitor masitinib, in the presence of gross disease or as an adjunct to surgical resection of the primary tumour. In patients presenting with metastatic disease, surgical resection of the primary tumour with adjunctive therapy with any chemotherapy incurred a significant survival advantage [median survival time (MST): 278 days] compared to patients receiving chemotherapy without surgical excision of the primary tumour (MST: 91 days, P < 0.0001). Patients with a surgically excised Patnaik grade II tumour and high Ki‐67 in the absence of metastatic disease treated with vinblastine and prednisolone showed a significantly longer survival (MST: 1946 days) than those treated with masitinib (MST: 369 days, P = 0.0037). Further prospective case‐controlled clinical trials of high‐risk MCTs are required to make precise evidence‐based treatment decisions for individual patients. 相似文献
13.
14.
15.
16.
Fasting for 24 h had no statistically significant effect on cortisol, glucose or testosterone concentrations. A dose of pentobarbitone sodium which induced light anaesthesia resulted in an immediate decrease in cortisol values from 5.0-11.1 ng/ml to 2.2-3.6 ng/ml until waking-this latter event was accompanied by an excessive release of cortisol (up to 16.6 ng/ml). In two out of three goats testosterone concentrations decreased from 4.0-9.0 ng/ml to less than 0.5 ng/ml after pentobarbitone; low values were maintained for 4.5-6 hours. Glucose concentrations were unaffected. Precise doses of pentobarbitone (20 mg/kg or 30 mg/kg) resulted in similar cortisol profiles as above but with higher concentrations achieved upon waking from the higher dose of pentobarbitone. On two out of nine occasions increased PCO2 values were recorded concurrently with increased cortisol concentrations during the period of anaesthesia, suggesting that a sufficiently strong stressful stimulus can break through the pentobarbitone blockade. 相似文献
17.
A 20-min van journey increased plasma cortisol concentrations to 15-25 ng/ml in male goats, blood glucose concentrations were not affected, but respiratory rates and heart rates were increased, the latter by 40 beats per min. A 2-h van journey increased plasma cortisol to greater than 25 ng/ml and blood glucose to greater than 5 mmol/l. Respiratory rates were increased to greater than 40 breaths per min and heart rates by greater than 100 beats per min. Xylazine alone (0.01 mg/kg) suppressed resting plasma cortisol concentrations, increased blood glucose concentrations to 4.5 +/- 0.8 mmol/l and suppressed respiratory rates by 5-10 breaths per min and heart rates by 20 beats per min. Cortisol concentrations were suppressed by xylazine treatment if given before a 20-min van journey, and for approximately 60 min if given 20 min after the start of a 2-h journey. When combined with transport, xylazine caused an additive effect on glucose concentrations, but suppressed respiratory and heart rates. However, for the latter criteria the timing of suppression was different depending on the time of onset and duration of the stressor. Injection of 50 micrograms ovine corticotrophin releasing factor (CRF) caused an immediate elevation of cortisol concentrations (but not glucose) which lasted for at least 6 h compared with the return to baseline within 60 min after either length of journey. Xylazine pretreatment did not alter the cortisol response to CRF, suggesting that xylazine must act centrally above pituitary level when blocking the cortisol response to transport. It is proposed that under resting conditions the hypothalamus is under alpha 2-adrenergic suppression. Stimulation of cortisol secretion in response to a stressor can be inhibited by an alpha 2-adrenergic agonist. 相似文献
18.
Navarre WW Porwollik S Wang Y McClelland M Rosen H Libby SJ Fang FC 《Science (New York, N.Y.)》2006,313(5784):236-238
Horizontal gene transfer plays a major role in microbial evolution. However, newly acquired sequences can decrease fitness unless integrated into preexisting regulatory networks. We found that the histone-like nucleoid structuring protein (H-NS) selectively silences horizontally acquired genes by targeting sequences with GC content lower than the resident genome. Mutations in hns are lethal in Salmonella unless accompanied by compensatory mutations in other regulatory loci. Thus, H-NS provides a previously unrecognized mechanism of bacterial defense against foreign DNA, enabling the acquisition of DNA from exogenous sources while avoiding detrimental consequences from unregulated expression of newly acquired genes. Characteristic GC/AT ratios of bacterial genomes may facilitate discrimination between a cell's own DNA and foreign DNA. 相似文献
19.
George Rigos Alexandros Samartzis Morgane Henry Eleni Fountoulaki Efthimia Cotou John Sweetman Simon Davies Ioannis Nengas 《Aquaculture International》2010,18(6):1093-1104
The comparative effects of iron-supplemented levels on growth, tissue distribution, haematology and immunology of gilthead
sea bream, Sparus aurata (2 g) were investigated, using four organic (50, 100, 200, 300 mg ORG/kg diet) and one inorganic iron source (200 INOR mg/kg diet).
Fish were treated for 12 weeks with the experimental diets and maintained at a water temperature of 19–22°C. Growth (final
weight and specific growth rate), tissue distribution (spleen, liver and muscle), haematological parameters (red blood cells,
haematocrit, haemoglobin and mean corpuscular haemoglobin concentration) and non-specific immune indexes (respiratory burst
activity and antibacterial activity of serum) were analysed. No significant differences were found in growth and iron tissue
distribution among the tested groups. Red blood cell counting was statistically higher in fish given 50 ORG, 100 ORG, 200
ORG and 200 INOR feeds. However, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration were not significantly
affected by increasing dietary iron. Fish receiving the 100 ORG diet had the best performance with respect to the respiratory
burst activity and significantly higher values for antibacterial activity of serum were obtained in fish fed with the 300
ORG diet. The present findings provided no clear evidence of the optimum iron concentration. However, there was adequate indication
that iron supplementation enhanced the performance of gilthead sea bream, mainly from a haematological and immunological point
of view. 相似文献
20.
A method for the separation of the oil, emulsifier and polymer or salt fractions of adjuvants is described. The adjuvant is dissolved in 90% aqueous ethanol and filtered to remove polymers or salt. Light petroleum (distillation range 30–40°C) is added to the solution in a separating funnel. The light petroleum fraction is subsequently extracted with successive aliquots of 80, 70, 60 and 50% aqueous ethanol. The whole of the ethanol and light petroleum fractions are evaporated to dryness to yield the emulsifier and oil fractions respectively. Emulsifier, oil and polymer or salt are determined gravimetrically. The method successfully detected the presence of polymer or salt in adjuvants, but could not distinguish between them when both were present in the same product. The adjuvants could be classified into four broad classes; those containing > 70% emulsifier (wetter-spreaders), those containing > 75% oil (anti-evaporants), those containing a high proportion of polymer (film-forming substances), and those containing comparable amounts of all three components (multi-purpose adjuvants). 相似文献