全文获取类型
收费全文 | 506篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
林业 | 32篇 |
农学 | 30篇 |
基础科学 | 2篇 |
112篇 | |
综合类 | 19篇 |
农作物 | 42篇 |
水产渔业 | 42篇 |
畜牧兽医 | 186篇 |
园艺 | 16篇 |
植物保护 | 45篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 19篇 |
2020年 | 29篇 |
2019年 | 15篇 |
2018年 | 18篇 |
2017年 | 12篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 10篇 |
2013年 | 40篇 |
2012年 | 40篇 |
2011年 | 33篇 |
2010年 | 22篇 |
2009年 | 18篇 |
2008年 | 26篇 |
2007年 | 27篇 |
2006年 | 23篇 |
2005年 | 22篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 13篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1980年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有526条查询结果,搜索用时 46 毫秒
521.
Increasing zinc (Zn) concentration of cereal grains is a global challenge to alleviate Zn deficiency‐related health problems in humans caused by low dietary Zn intake. This study investigated the effects of soil‐ and foliar‐applied nitrogen (N) and Zn fertilizers on grain Zn accumulation of durum wheat (Triticum durum) grown on a Zn‐deficient soil. In addition, localization of Zn and protein within durum wheat grain was studied by using Bradford reagent for protein and dithizone (diphenyl thiocarbazone) for Zn. Grain Zn concentration was greatly enhanced by soil or foliar applications of Zn. When Zn supply was adequately high, both soil and foliar N applications improved grain Zn concentration. Consequently, there was a significant positive correlation between grain concentrations of Zn and N, when Zn supply was not limiting. Protein and Zn staining studies showed co‐localization of Zn and protein within grain, particularly in the embryo and aleurone. Results indicate that N and Zn fertilization have a synergistic effect on grain Zn concentration. Possibly, increasing N supply contributes to grain Zn concentration by affecting the levels of Zn‐chelating nitrogenous compounds or the abundance of Zn transporters. Our results suggest that nitrogen management can be an effective agronomic tool to improve grain Zn concentration. 相似文献
522.
Technical efficiency of cage fish farming in Peninsular Malaysia: a stochastic frontier production approach
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Abdullahi Iliyasu Zainal Abidin Mohamed Mohamed Mansor Ismail Abdullah Mahir Amin Hashim Mazuki 《Aquaculture Research》2016,47(1):101-113
The study estimates technical efficiency and investigates the factors affecting the technical inefficiency of cage fish farming in Peninsular Malaysia. The study employs the stochastic frontier function to estimate a production frontier and technical inefficiency model. The data were collected using standard structured questionnaires completed by sample cage fish farmers in the study area. The result reveals an estimated mean technical efficiency score of 0.79, implying that the sample fish farmers are operating 21% below the production frontier and thus, there is room for improvement. The production function involves the use of one output and four inputs, which are stocking density, feed, labour and other relevant production costs. The coefficients of all the inputs have positive signs and statistically significant impacts on the output. The output elasticity associated with stocking density is the highest (0.634), followed by feed (0.317). The null hypotheses that the technical inefficiency effects are absent from the model and that the combined exogenous variables do not influence inefficiency are strongly rejected. The individual's null hypotheses of no age effect, no experience effect, no education effect, no species effect, no extension services effect, no workshop attended effect and no diseases effect on technical inefficiency are all rejected at different levels of statistical significance. 相似文献
523.
The objective of this study was to investigate the effects of five isonitrogenous (35% crude protein) diets having different
energy contents; 10.85, 11.82, 12.73, 13.69, and 15.06 MJ DE/kg, respectively, on the gonad development and weight gain of
Sharptooth catfish fingerlings. Energy contents of the experimental diets were increased with the increasing amount of soy-acid
oil (0, 4, 8.5, 13, 18%) and each group of fish was fed on their respective diets (group I was fed diet I) during 180 days.
The gonad maturation was significantly affected by dietary energy. In both sexes, the histological inspections of the gonads
did reveal differences among the fish fed different energetic diets. Fish fed diets I, II, and III had significantly heavier
and more developed gonads compared to those on diets IV and V. Fish fed the higher energetic diets (IV and V) had partially
low numbers of yolky oocytes compared to other groups. The mean GSI values of female and male fish fed with diet III was significantly
greater than those fed diets with higher dietary energy; however, higher HSI values were recorded for fish fed with the higher
energetic diets (IV and V). Also, the best weight gain for both males and females were recorded from the fish fed diet III
(12.73 MJ DE/kg). Therefore, on the basis of the present results, among energy levels tested, 12.73 MJ DE/kg was found to
be optimal for healthy gonad development and weight gain. 相似文献
524.
Effects of dietary antioxidants on oxidative stress,antioxidant defence and growth of freshwater crayfish Astacus leptodactylus (Eschscholtz, 1823) during the reproductive period in females
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this study, we examined the effects of dietary antioxidant vitamins [vitamin E (Vit E), vitamin C (Vit C) and vitamin A (Vit A)], astaxanthin (AX) and β‐carotene (βC) supplementation on oxidative stress [malondialdehyde (MDA)], antioxidant enzyme activities [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH‐Px)] and glutathione (GSH) levels in hepatopancreas, ovarian, muscle, gill tissues and survival rates (SR), live weight gain (LWG), specific growth rate (SGR) of Astacus leptodactylus during ovarian development. The EE, EC, EA, EAX and EβC groups were formed by addingClick here to enter text. Vit E, Vit C, Vit A, AX and βC to the diet respectively. The antioxidants did not have a significant impact on the values of SR, LWG and SGR. After 137 days, the MDA levels in the Control (C) group were statistically higher in the hepatopancreas, ovarian and muscle tissues according negative control (NC), EE, EC, EA, EAX and EβC groups. The SOD activities in ovarian, muscle and gill tissues and GSH levels in ovarian and muscle tissues were lower in the C group compared with the NC group, but GSH‐Px activities in hepatopancreas and ovarian tissues and GSH levels in gill tissues were higher. The MDA levels were statistically lower in all tissues of crayfish in experimental groups according to C group. The antioxidant enzyme activities and GSH levels changed according to tissue. The results showed that Vit E and AX should be supplemented in diets to increase the reproductive performance of crayfish, because Vit E and AX were of higher potential as antioxidants than other vitamins and carotenoids in ovarian tissues. 相似文献
525.
Kursat Ozer Aysun Yilmaz Mariano Carossino Gulay Yuzbasioglu Ozturk Ozge Erdogan Bamac Hasan E. Tali Egemen Mahzunlar Utku Y. Cizmecigil Ozge Aydin Hamid B. Tali Semaha G. Yilmaz Zihni Mutlu Ayse Ilgn Kekec Nuri Turan Aydin Gurel Udeni Balasuriya Munir Iqbal Juergen A. Richt Huseyin Yilmaz 《Journal of veterinary science (Suw?n-si, Korea)》2022,23(4)
This paper reports a presumptive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a cat. A cat with respiratory disease living with three individuals with coronavirus disease 2019 showed bilateral ground-glass opacities in the lung on X-ray and computed tomography. The clinical swabs were negative for SARS-CoV-2 RNA, but the serum was positive for SARS-CoV-2 antibodies. Interstitial pneumonia and prominent type 2 pneumocyte hyperplasia were noted on histopathology. Respiratory tissues were negative for SARS-CoV-2 RNA or antigen, but the cat was positive for feline parvovirus DNA. In conclusion, the respiratory disease and associated pathology in this cat could have been due to exposure to SARS-CoV-2. 相似文献
526.
Migena Gjoni Gündemir Tomasz Szara Constantin Spataru Ismail Demircioglu Bernard Turek Georgios Petrovas Mihaela Claudia Spataru 《Anatomia, histologia, embryologia》2023,52(2):190-196
The anatomy of the sternum in birds varies according to their habitats and type of locomotion. In particular, the carina sterni manifest different shape variations. In this study, the shape of the carina sterni was investigated by means of geometric morphometrics. Birds of different types of locomotion were used in the study: flying, swimming, and terrestrial. Ducks and chickens show a wider variety of shapes. Pigeons are the species with the least differences. The margo cranialis carinae in a turkey is the flattest compared to other species. In chickens, the apex carinae is more caudally than the base of the carina sterni. The margo cranialis of the carina sterni in ducks is concave. The differences in centroid size and shape differences between species collectively are statistically significant (p < 0.0001). The most distinct shape contrast is between the duck and turkey (p: 0.0003). Form differences between the ducks and geese as well as between the chicken and turkey are statistically insignificant. There is less variation in the shape of the carina sterni among avian species representing the same type of locomotion. Although there are many comparative morphological and morphometric studies of birds, shape analysis studies revealing the interspecific differences and similarities of the sternum are very limited. Morphology of the carina sterni can be useful in taxonomic investigations. 相似文献