全文获取类型
收费全文 | 587篇 |
免费 | 47篇 |
专业分类
林业 | 21篇 |
农学 | 19篇 |
基础科学 | 1篇 |
84篇 | |
综合类 | 45篇 |
农作物 | 81篇 |
水产渔业 | 103篇 |
畜牧兽医 | 239篇 |
园艺 | 7篇 |
植物保护 | 34篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 21篇 |
2020年 | 18篇 |
2019年 | 21篇 |
2018年 | 33篇 |
2017年 | 15篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 34篇 |
2012年 | 36篇 |
2011年 | 52篇 |
2010年 | 34篇 |
2009年 | 30篇 |
2008年 | 27篇 |
2007年 | 32篇 |
2006年 | 23篇 |
2005年 | 28篇 |
2004年 | 13篇 |
2003年 | 34篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有634条查询结果,搜索用时 375 毫秒
501.
Survey of the prevalence and methodology of quality assurance for B‐mode ultrasound image quality among veterinary sonographers
下载免费PDF全文
![点击此处可从《Veterinary radiology & ultrasound》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Larry P. Hoscheit Hock Gan Heng Chee Kin Lim Hsin‐Yi Weng 《Veterinary radiology & ultrasound》2018,59(3):326-332
Image quality in B‐mode ultrasound is important as it reflects the diagnostic accuracy and diagnostic information provided during clinical scanning. Quality assurance programs for B‐mode ultrasound systems/components are comprised of initial quality acceptance testing and subsequent regularly scheduled quality control testing. The importance of quality assurance programs for B‐mode ultrasound image quality using ultrasound phantoms is well documented in the human medical and medical physics literature. The purpose of this prospective, cross‐sectional, survey study was to determine the prevalence and methodology of quality acceptance testing and quality control testing of image quality for ultrasound system/components among veterinary sonographers. An online electronic survey was sent to 1497 members of veterinary imaging organizations: the American College of Veterinary Radiology, the Veterinary Ultrasound Society, and the European Association of Veterinary Diagnostic Imaging, and a total of 167 responses were received. The results showed that the percentages of veterinary sonographers performing quality acceptance testing and quality control testing are 42% (64/151; 95% confidence interval 34–52%) and 26% (40/156: 95% confidence interval 19–33%) respectively. Of the respondents who claimed to have quality acceptance testing or quality control testing of image quality in place for their ultrasound system/components, 0% have performed quality acceptance testing or quality control testing correctly (quality acceptance testing 95% confidence interval: 0–6%, quality control testing 95% confidence interval: 0–11%). Further education and guidelines are recommended for veterinary sonographers in the area of quality acceptance testing and quality control testing for B‐mode ultrasound equipment/components. 相似文献
502.
In this research, we have investigated the removal efficiency of natural organic matter (NOM) from river and stream water using potassium ferrate(VI). For the study, ferrate was added in 100-ml water sample mixed either with humic acid or with fulvic acid. The removal efficiency at the ferrate dose of 2–46 mg/l (as Fe) was 21–74% for 10 mg/l humic acid and 48–78% for 10 mg/l fulvic acid. NOM was more effectively removed either at lower pH or at higher temperature. The removal performance by ferrate was comparable to that by traditional coagulants (i.e., alum, FeSO4·7H2O, and FeO(OH)). In addition, the removal rate of humic acid using traditional coagulants was improved by pretreatment with a very small dose of ferrate. The reaction between ferrate and humic acid was completed within 60 s, while showing first-order kinetic, and then reached a steady state. 相似文献
503.
504.
505.
Thomas L. Welker Chhorn Lim Phillip Klesius Keshun Liu 《Journal of the World Aquaculture Society》2014,45(6):625-637
The effects of distiller's dried grains with solubles (DDGS) from different sources on growth performance, hematology, and immunity of hybrid tilapia, Oreochromis niloticus × Oreochromis aureus, were evaluated. Sex‐reversed, all‐male hybrid tilapia (3.72 ± 0.08 g initial weight) were fed diets in which 30% of protein in the control diet, supplied by a combination of soybean meal (SBM) and corn meal (CM) (SBM : CM ratio = 1.8), was replaced by wheat DDGS (WtDDGS), sorghum DDGS (SDDGS), whiskey DDGS (WkDDGS), or one of three corn DDGS (CDDGS 1–3) sources (control and six experimental diets) for 10 wk. Tilapia were stocked at 30 fish per aquaria (three aquaria per diet). Growth of tilapia fed diets containing DDGS sources was similar to or better than the control diet, and no nutritional deficiencies were observed. Tilapia fed the CDDGS 2 and 3 sources showed superior weight gain. Improved growth appeared to be caused by an increase in feed intake and not due to improvements in dietary nutritional value. Hematology and immunity were not affected by DDGS source. It is concluded that DDGS from all the sources examined can be included in the diet of juvenile hybrid tilapia at about 30% as a replacement of one‐third protein from SBM‐CM mixture without adverse effects. 相似文献
506.
Erchao Li Chhorn Lim Phillip H Klesius Thomas L Welker 《Journal of the World Aquaculture Society》2013,44(1):42-55
The effects of dietary linoleic (LA) and linolenic acids (LN) on growth and immunity of all‐male hybrid tilapia, Oreochromis niloticus × Oreochromis aureus, were evaluated for 10 wk. Fish fed 0.12% LA + 0% LN had the lowest weight gain (WG) but was not significantly different from diets containing 0.5% LA or 0.40% LA + 1.0% LN. Fish fed 1% LA had the highest WG but did not differ from diets with 0.5% LA, 2.0% LA, 0.26% LA + 0.5% LN, 0.69% LA + 2.0% LN, or diets containing both LA and LN at 0.25, 0.5, and 1.0%. Feed intake, feed efficiency, and survival did not differ among treatments. Total body n‐6 fatty acids (FAs) increased with increasing dietary levels of n‐6. Total body n‐3 FAs also appeared to increase with increasing dietary n‐3 levels but peaked at 1% of diet. Dietary treatment had no effect on hematology, immune function, or survival to Streptococcus iniae. This study indicates that both LA and LN are dietary essential for growth of hybrid tilapia. Dietary LA alone can meet the essential FA requirement, and a level of 1.14% of diet is required for optimum growth. 相似文献
507.
Fifty-three bulk deposition samples were collected at the campus of the University of Brunei Darussalam between April and November 1994 using a funnel-in bottle sampler. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5 °C for subsequent chemical analysis. Analyses for Cl?, NO3 ? and SO4 2? were carried out by means of ion chromatography, while Na+, K+, Ca2+ and Mg2+ were determined by atomic spectroscopy. The recorded pH values were in the range of 4.35 to 6.59. Seventy-seven percent of the samples had pH values below 5.6, demonstrating the occurrence of acidic deposition. The range, mean and standard deviation of measured concentrations are reported. There was very little difference between measurements in filtered and unfiltered samples. Correlation coefficients between pairs of parameters are reported and discussed. 相似文献
508.
Philpott M Gould KS Lim C Ferguson LR 《Journal of agricultural and food chemistry》2004,52(6):1511-1513
Anthocyanins from a variety of fruits and vegetables have been shown to possess potent antioxidant activity in vitro, but scavenging of free radicals by anthocyanins has only been demonstrated in situ in the leaves of certain plants. We report on a new sweetpotato that exhibits mottled purple flesh attributable to high concentrations of anthocyanins. By perfusing transverse sweetpotato sections with the reactive oxygen species H(2)O(2), followed by the H(2)O(2) sensitive fluorochrome scopletin, we show that anthocyanins act as antioxidants in situ within the sweetpotato storage roots. We also demonstrate in vitro antioxidant activity by sweetpotato anthocyanins, where an additive effect with hydroxycinnamic acids is observed. Anthocyanic foods have been shown to offer protection against a variety of degenerative disease processes. Given that sweetpotato can be eaten several hundred grams at a time and as a staple, these data are consistent with the possibility of superior health protection by anthocyanic varieties of sweetpotato in comparison to most common fruits and vegetables. 相似文献
509.
An Integrated Modeling Approach to Total Watershed Management: Water Quality and Watershed Assessment of Cheney Reservoir, Kansas, USA 总被引:1,自引:0,他引:1
Steven H. Wang Donald G. Huggins Lyle Frees Chad G. Volkman Niang C. Lim Debra S. Baker Val Smith Frank deNoyelles Jr. 《Water, air, and soil pollution》2005,164(1-4):1-19
Degradation of water quality is the major health concern for lakes and reservoirs in the central regions of the United States as a result of heavily devoted agricultural production. A vital key to the development of a reservoir management strategy is to identify nutrient loading that describes associated water quality conditions in reservoirs. This study integrated AnnAGNPS watershed and BATHTUB lake models to simulate actual lake water quality conditions of Cheney Reservoir, KS, and demonstrated the use of the coupled model for simulating lake response to changes in different watershed land use and management scenarios. The calibrated current-conditions model simulated in-lake reductions as much as 52% for TN, 48% for TP, and 70% for chlorophyll a due to conversion to native grass, and increases as much as 4% for TN, 9% for TP and 6% for chlorophyll a due to conversion of land from the Conservation Reserve Program (CRP) to cropland (15.5% of watershed). This model also demonstrated an increase in chlorophyll a (19%) as the lake sediment capacity was reached over the next century. 相似文献
510.
Chee Kin Lim Hock Gan Heng Lynn F. Guptill 《The Canadian veterinary journal. La revue veterinaire canadienne》2021,62(7):751
An 11-year-old, spayed female American domestic shorthair cat was presented with open-mouth breathing and dyspnea due to respiratory tract disease. Radiographically, there was thickening of the retropharyngeal soft tissue and soft palate, focal pulmonary change, and severe pectus excavatum (PE), best seen on the left lateral view. Repeat thoracic radiographs 4 months later showed persistent PE, but only on the right lateral view; PE was absent on the left lateral view. The dynamic component of the observed PE was presumably acquired secondary to chronic upper respiratory disease and/or concurrent increased pliability of the thoracic wall from prolonged prednisolone treatment. 相似文献