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   214篇
  免费   25篇
林业   1篇
农学   4篇
  4篇
综合类   31篇
农作物   5篇
水产渔业   11篇
畜牧兽医   173篇
植物保护   10篇
  2022年   1篇
  2021年   1篇
  2020年   7篇
  2019年   4篇
  2018年   11篇
  2017年   9篇
  2016年   9篇
  2015年   4篇
  2014年   6篇
  2013年   13篇
  2012年   6篇
  2011年   5篇
  2010年   18篇
  2009年   21篇
  2008年   17篇
  2007年   11篇
  2006年   2篇
  2005年   1篇
  2004年   6篇
  2003年   3篇
  2002年   1篇
  2001年   5篇
  2000年   1篇
  1999年   7篇
  1998年   14篇
  1997年   9篇
  1996年   13篇
  1995年   5篇
  1994年   2篇
  1993年   4篇
  1992年   5篇
  1991年   5篇
  1990年   6篇
  1989年   2篇
  1988年   2篇
  1987年   1篇
  1984年   1篇
  1978年   1篇
排序方式: 共有239条查询结果,搜索用时 15 毫秒
141.
142.
Electrical conductivity in the precambrian lithosphere of western canada   总被引:1,自引:0,他引:1  
The subcrustal lithosphere underlying the southern Archean Churchill Province (ACP) in western Canada is at least one order of magnitude more electrically conductive than the lithosphere beneath adjacent Paleoproterozoic crust. The measured electrical properties of the lithosphere underlying most of the Paleoproterozoic crust can be explained by the conductivity of olivine. Mantle xenolith and geological mapping evidence indicate that the lithosphere beneath the southern ACP was substantially modified as a result of being trapped between two nearly synchronous Paleoproterozoic subduction zones. Tectonically induced metasomatism thus may have enhanced the subcrustal lithosphere conductivity of the southern ACP.  相似文献   
143.
ObjectivesTo describe perioperative management and complications, risk factors and mortality rates in cats anaesthetized for treatment of ureteral obstruction.Study designRetrospective, clinical, cohort study.AnimalsThirty-seven client-owned cats anaesthetized for ureteral surgery.MethodsRecords with sufficient data for cats treated between March 2010 and March 2013 were examined for breed, age, gender, history, concurrent diseases, pre- and post-anaesthetic biochemical and haematological parameters, American Society of Anesthesiologists classification, anaesthetic protocol, surgical technique, surgeon, perioperative complications and mortality within 48 hours after extubation. Associations between risk factors and outcome variables were evaluated using univariable analysis. Odds ratios and 95% confidence intervals were calculated for significant parameters. Sensitivity and specificity using receiving operator characteristic curve analysis were calculated for creatinine, potassium level and standard base excess (SBE) to denote survival or non-survival.ResultsPreoperatively, all cats were azotaemic: mean ± SD urea was 31.6 ± 26.9 mmol L−1 and median (range) creatinine was 562 μmol L−1 (95 μmol L−1 to off scale). Thirteen cats were hyperkalaemic (K+ > 6.5 mmol L−1). Anaesthesia-related complications included bradycardia (n = 8, 21.6%), hypotension (n = 15, 40.5%) and hypothermia (n = 32, 86.5%). Seven cats (18.9%) died postoperatively. Non-survivors were significantly (p = 0.011) older (9.8 ± 1.9 years) than survivors (6.4 ± 3.1 years) and had higher potassium concentrations (p = 0.040). Risk factors associated with mortality were ASA classes IV and V (p = 0.022), emergency procedures (p = 0.045) and bicarbonate administration (p = 0.002). Non-survivors had higher creatinine concentrations (p = 0.021) and lower SBE (p = 0.030).Conclusion and clinical relevanceIntraoperative anaesthetic complications were common; increased age, poor health status, preoperative bicarbonate administration, hyperkalaemia and increased creatinine were associated with increased risk for death and can be used to predict risk for complications.  相似文献   
144.
The fractioning of some components and their immobilization of Flavourzyme, a commercial protease/aminopeptidase preparation, has been investigated to improve its specificity and stability. Adsorption of Flavourzyme on two ionic exchangers yielded two fractions with endoprotease activity and one fraction containing aminopeptidase activity. The use of an amine agarose gel has made it possible to purify a 43 kDa protein with only endoprotease activity. Immobilization of this endoprotease and the original Flavourzyme preparation onto glyoxyl-agarose provided derivatives that were more thermostable than their soluble counterparts. Tests using immobilized Flavourzyme and immobilized purified endoprotease for the hydrolysis of chickpea proteins showed that both preparations can be used for the production of protein hydrolysates and compare very favorably with the original crude Flavourzyme in terms of reducing the production of free amino acids. This was especially so in the case of immobilized endoprotease, which produced only 0.2% free amino acids. Keeping free amino acids content low is very important in protein hydrolysates for nutritional use to avoid excessive osmotic pressure.  相似文献   
145.
A Magnetic Signature at Io: Initial Report from the Galileo Magnetometer   总被引:1,自引:0,他引:1  
During the inbound pass of the Galileo spacecraft, the magnetometer acquired 1 minute averaged measurements of the magnetic field along the trajectory as the spacecraft flew by Io. A field decrease, of nearly 40 percent of the background jovian field at closest approach to Io, was recorded. Plasma sources alone appear incapable of generating perturbations as large as those observed and an induced source for the observed moment implies an amount of free iron in the mantle much greater than expected. On the other hand, an intrinsic magnetic field of amplitude consistent with dynamo action at Io would explain the observations. It seems plausible that Io, like Earth and Mercury, is a magnetized solid planet.  相似文献   
146.
Objective To describe two cases of infection with Fasciola hepatica i n young farmed emus, subacute and chronic fasci-olosis and a response to treatment of the flock with albenda-zole.
Procedure Gross lesions were found at necropsy and hepatic lesions in microscopic examination. The parasite recovered from one emu was identified by its morphological characteristics and an egg count reduction test was carried out after treatment of the flock with albendazole.
Results Hepatic lesions resembling subacute and chronic fasciolosis of ruminants were identified. An adult fluke was recovered from the liver of one of the birds and was identified as F hepatica . The eggs of the fluke were irregular in shape and size. No fluke eggs were identifiable in faeces of live emus 10 days after treatment of the flock with albendazole at a dose of 10 mg/kg.
Conclusions This is the first reported case of infection with F hepatica i n farmed emus and the first report of the occurrence of Fasciola infection is the class Aves. The irregular shape and size of the eggs may be attributable to infection of an aberrant host. Treatment with albendazole eliminated eggs from the faeces of the flock.  相似文献   
147.
Genotype × environment interaction (GEI) affects marketable fruit yield and average fruit weight of both hybrid and open-pollinated (OP) tomato genotypes. Cultivars vary significantly for marketable fruit yield, with hybrid cultivars having, on average, higher yield than OP cultivars. However, information is scanty on environmental factors affecting the differential response of tomato genotypes across environments. Hence, the aim of this research was to use factorial regression (FR) and partial least squares (PLS) regression, which incorporate external environmental and genotypic covariables directly into the model for interpreting GEI. In this research, data from an FAO multi-environment trial comprising 15 tomato genotypes (7 hybrid and 8 OP) evaluated in 18 locations of Latin America and the Caribbean were analyzed using FR and PLS. Environmental factors such as days to harvest, soil pH, mean temperature (MET), potassium available in the soil, and phosphorus fertilizer accounted for a sizeable portion of GEI for marketable fruit yield, whereas trimming, irrigation, soil organic matter, and nitrogen and phosphorus fertilizers were important environmental covariables for explaining GEI of average fruit weight. Locations with relatively high minimum and mean temperatures favored the marketable fruit yield of OP heat-tolerant lines CL 5915-223 and CL 5915-93. An OP cultivar (Catalina) and a hybrid (Apla) showed average marketable fruit yield across environments, while two hybrids (Sunny and Luxor) exhibited outstanding marketable fruit yield in high yielding locations (due to lower temperatures and higher pH) but a sharp yield loss in poor environments. Two stable hybrid genotypes in high yielding environments, Narita and BHN-39, also showed high and stable yield in average and low yielding environments.  相似文献   
148.
Double-outlet right ventricle in a 10-month-old Friesian filly   总被引:1,自引:1,他引:0  
A 10-month-old Friesian filly had a presentation that was consistent with chronic left- and right-sided congestive heart failure. Clinical pathology findings included abnormal haematological and biochemical variables, abnormal blood gas values and increased serum concentration of cardiac troponin I. Echocardiography revealed cardiac chamber dilation and dextropositioning of the aorta. Radiography revealed a generally enlarged heart and pulmonary interstitial infiltration. These findings were supported at necropsy and the diagnosis of double-outlet right ventricle was confirmed. The pathological changes and physiological responses subsequent to double-outlet right ventricle have not previously been described in detail in horses. Clinical progression closely resembles that seen in humans, in whom antemortem diagnosis relies on echocardiography. In horses, complex cardiac disease presents a diagnostic challenge to the clinician. Appropriate therapy must be based on an accurate diagnosis.  相似文献   
149.
Nitrate–nitrite poisoning killed four adult alpacas and induced the abortion of a full-term fetus after access to oaten hay ( Avena sativa ) containing 3.2% KNO3 equivalent in dry matter. Necropsy findings were cyanosis, dark-coloured blood, and pulmonary congestion and oedema. Aqueous humour from two adults contained 25 mg NO3/L and that from the fetus contained 10 mg NO3/L. Cyanide poisoning possibly killed two adult wether alpacas that ate a garden-cultivated variety of Osteospermum ecklonis (South African daisy, bietou) with a cyanide potential of 6800 mg HCN/kg dry matter.  相似文献   
150.
The present study attempted to select the subpopulation of stallion spermatozoa that best survived a conventional freezing and thawing procedure, using centrifugation of post-thawed semen samples through a single layer of a glycidoxypropyltrimethoxysilane-coated silica colloid with a species-specific formulation (Androcoll-E™). After freezing and thawing, four sperm subpopulations were identified, listed as FT1 to FT4. While subpopulations FT1 and FT2 were characterized by low sperm velocity, high velocities characterized the ones called FT3 and FT4. The single-layer centrifugation (SLC)-handled sperm sample was enriched in subpopulation FT3, reaching a proportion of 82.6% of the present spermatozoa, in contrast with the non-filtered control post-thawed semen, where this sperm subpopulation only accounted for 16.3% of the total. It is concluded that in the equine industry, the SLC is a practical, easy-to-perform approach to improve the quality of equine frozen–thawed semen samples.  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