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   329篇
  免费   21篇
林业   19篇
农学   7篇
  94篇
综合类   17篇
农作物   27篇
水产渔业   31篇
畜牧兽医   121篇
园艺   7篇
植物保护   27篇
  2024年   1篇
  2023年   2篇
  2022年   4篇
  2021年   10篇
  2020年   9篇
  2019年   8篇
  2018年   11篇
  2017年   10篇
  2016年   13篇
  2015年   5篇
  2014年   9篇
  2013年   9篇
  2012年   21篇
  2011年   30篇
  2010年   22篇
  2009年   20篇
  2008年   29篇
  2007年   23篇
  2006年   25篇
  2005年   18篇
  2004年   18篇
  2003年   18篇
  2002年   13篇
  2000年   5篇
  1999年   1篇
  1997年   3篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   4篇
  1987年   1篇
  1983年   1篇
  1982年   1篇
  1975年   1篇
排序方式: 共有350条查询结果,搜索用时 62 毫秒
41.
Mixtures of wet vegetable wastes (Brassica, carrot or onion) and dry onion waste were composted at 50 °C for 7 days. The incorporation of the raw or composted vegetable waste mixtures into sandy loam, silt and peat soils reduced the viability of sclerotia of S. cepivorum in glasshouse pot bioassays. The reduction in viability was dependent on waste type, rate of incorporation, duration of exposure and soil type. Onion waste was the most effective waste type in reducing sclerotia viability in all three soils. The Brassica and carrot wastes were as effective as the onion waste in silt soil but less effective in sandy loam and peat soil. A 50% w/w incorporation rate of the wastes gave the largest reduction in viability, with an increase in reduction over time. Composted onion waste reduced sclerotia viability under glasshouse and field conditions although the effect was smaller in the field. Composted onion waste incorporated into soil at 50% w/w reduced the incidence of Allium white rot on onion seedlings in glasshouse pot tests. Incidence and control of the disease differed with soil type. The most consistent control was achieved in peat soil whereas no control was observed in silt soil. Incorporation of the waste 2 months prior to sowing or transplanting reduced seedling emergence in sandy loam soil and growth in all three soil types. The potential for field application of composted vegetable wastes as a sustainable method for control of Allium white rot and waste disposal is discussed.  相似文献   
42.
43.
OBJECTIVE: To assess the applicability of high-frequency diagnostic ultrasonography for evaluation and accurate measurement of the skin thickness of clinically normal dogs. ANIMALS: 26 healthy dogs (12 sexually intact males, 13 sexually intact females, and 1 spayed female) of various breeds and ages. PROCEDURE: Ultrasonographic examination of the skin and histomorphometric analysis of skin biopsy specimens obtained from the same site were performed. A 13-MHz linear-array transducer was used to obtain a series of ultrasonographic images of the skin in the flank region; images were analyzed and measured by use of imaging software. Cutaneous biopsy specimens were placed in fixative and then stained with H&E and Masson trichrome stains. Histomorphometric analysis was performed by use of an image analyzer. Thickness of the epidermis and dermis of each specimen was evaluated by use of a semiautomatic procedure of quantification. Data obtained from ultrasonographic and histologic measurements were compared by use of the Pearson correlation test. RESULTS: The ultrasonographic pattern of canine skin was consistently characterized by 3 distinct, defined echogenic layers corresponding to the epidermal entry echo, epidermis and dermis, and subcutaneous tissues. A positive correlation was found between ultrasonographic and histologic measurements of skin thickness. CONCLUSIONS AND CLINICAL RELEVANCE: Comparison between ultrasonographic and histologic appearance of the skin revealed that layering of canine skin (ie, epidermis and dermis) and the subcutaneous tissues may be recognized and measured by use of high-frequency ultrasonography. Thus, diagnostic ultrasonography may be a useful tool for the noninvasive evaluation of cutaneous disorders in dogs.  相似文献   
44.
Two healthy buffaloes (Bubalus bubalis) in a herd which had not been vaccinated against infectious bovine rhinotracheitis (IBR), were selected for their seropositivity for anti-bovine herpesvirus type 1 (BoHV-1) glycoprotein E antibodies, and injected intramuscularly daily with dexamethasone for five consecutive days (day 1 to day 5) to reactivate any latent herpesvirus. Blood samples and nasal and vaginal swabs were collected daily from day 5 to day 15 from each buffalo for virological examination. All the vaginal swabs and blood samples were negative, but 13 of the 22 nasal swabs were positive; a cytopathic effect was observed in primary cultures of bovine fetal lung cells, and the viral isolates were identified as a herpesvirus by PCR. The viral strains were characterised by the sequence analysis of the genes coding for glycoproteins D and B, and the gene sequences were then used for phylogenetic analysis. The isolates from both buffaloes appeared identical at the level of the two genes, and were more closely related to bovine herpesvirus type 5 than to BoHV-1.  相似文献   
45.
Four different polyphenolic compounds were isolated by chromatographic methods from methanolic and hydromethanolic extracts of Ipomoea batatas tuber flour. On the basis of UV, mass, and NMR analysis procedures, the structure of the isolated compounds were determined as 4,5-di-O-caffeoyldaucic acid (1), 4-O-caffeoylquinic acid (2), 3,5-di-O-caffeoylquinic acid (3), and 1,3-di-O-caffeoylquinic acid (4). To the best of our knowledge, this is the first report of isolation and characterization of compound 1. Then, we evaluated the antioxidant activity of daucic acid derivative by using DPPH and FRAP methods together with authentic antioxidant standards, l-ascorbic acid, tert-butyl-4-hydroxy toluene (BHT), and gallic acid. The activity of compound 1 in both methods was higher than that of all standards used at the same molar concentration.  相似文献   
46.
47.
Growth, weight at birth and daily weight gain (DWG) on 12 water buffalo calves, starting from 6 days of age until completion of weaning, was investigated in this study. Different feeding regimens were given to two groups of animals with regard to daily milk replacer: (1) group 1 (G1) received a double concentration in single administration; whereas (2) group 2 (G2) received the same amount of milk replacer split twice daily. Blood samples were collected from each calf on days 6, 30, 60 and 90 to evaluate acute phase proteins (haptoglobin), bactericide activity, lysozime, total protein content and biochemical parameters. No differences were observed between the two groups in terms of dry matter intake, feed efficiency and live body weight at the end of the study. Interestingly, a significantly (P?<?0.05) reduced DWG was observed earlier in G1 (day 45) than in G2 (day 60). Gastrointestinal disorders were not recorded throughout the experimental period, and no significant differences were recorded between the two groups for all considered parameters. This study confirms the possibility of utilising one daily administration of milk replacer in water buffalo calf during weaning. This new approach facilitates calves management, without interfering with calves growing performances.  相似文献   
48.
In soil, iron (Fe) solubility depends on complex interactions between Fe minerals and organic matter, but very little is known about plant availability of Fe present in Fe oxides associated with humic substances. For this purpose, this study investigates the effect of Fe mineral crystallinity in the presence of humic acids (HA) on Fe availability to plants. Four Fe–HA mineral coprecipitates were prepared, either in the presence or absence of oxygen, i.e., two goethite (G)‐HA samples containing large amounts of Fe as nanocrystalline goethite and ferrihydrite mixed phases, and two magnetite (M)‐HA samples containing crystalline magnetite. Bioavailability studies were conducted in hydroponic systems on cucumber plants (Cucumis sativus L.) grown under Fe deficient conditions and supplied with the Fe–HA coprecipitates containing goethite or magnetite. Results showed that plants grown in the presence of Fe–HA coprecipitates exhibited a complete recovery from Fe deficiency, albeit less efficiently than plants resupplied with Fe‐chelate fertilizer used as control (Fe‐diethylene triamine penta acetic acid, Fe‐DTPA). However, the supply with either G‐ or M–HA coprecipitates produced different effects on plants: G–HA‐treated plants showed a higher Fe content in leaves, while M–HA‐treated plants displayed a higher leaf biomass and SPAD (Soil–Plant Analysis Development) index recovery, as compared to Fe‐DTPA. The distribution of macronutrients in the leaves, as imaged by micro X‐ray fluorescence (µXRF) spectroscopy, was different in G–HA and M–HA‐treated plants. In particular, plants supplied with the poorly crystalline G–HA coprecipitate with a lower Fe/HA ratio showed features more similar to those of fully recovered plants (supplied with Fe‐DTPA). These results highlight the importance of mineral crystallinity of Fe–HA coprecipitates on Fe bioavailability and Fe uptake in hydroponic experiments. In addition, the present data demonstrate that cucumber plants can efficiently mobilize Fe, even from goethite and ferrihydrite mixed phases and magnetite, which are usually considered unavailable for plant nutrition.  相似文献   
49.
The effects of an innovative process for the manufacture of peach and nectarine purees on the main quality indices, namely, color, consistency, carotenoid and phenolic content, and antioxidant activity, were studied using a peach cultivar that is optimal for nectar processing (cv. Redhaven) and peach and nectarine varieties that undergo a faster browning degradation. The innovative process, operating the pulping/finishing step at room temperature, was compared to the traditional process of hot pulping/finishing. The study comprised initial trials on a pilot plant scale and scaling up to industrial production of the puree and nectar. The quality of products was analyzed at the time of production and as a function of storage of both the puree and the nectar. With respect to the traditional process, the new process, scaled up to industrial levels, improved the color of peach and nectarine products (by increasing the L* value and decreasing the a* value), whatever the variety studied; maintained almost the same levels of carotenoids, hydroxycinnamates, flavan-3-ols, and flavonols; and reduced the level of cyanidin 3-O-glucoside. The presence of cyanidin 3-O-glucoside was correlated to an unstable and undesirable red hue of the products (even if its concentration was very low in all products), and the decreased level obtained by the innovative process was considered to be positive. On the basis of these results, new technology can be proposed for the processing of fruit varieties that are not suitable for puree production using traditional technology. This opens up two possibilities: (a) utilization of fresh market fruit surplus and (b) processing of selected fruit varieties that are rich in antioxidants but have a high browning potential, such as the Stark Red Gold nectarine. Furthermore, as the positive impact of the new technology is optimal at the beginning of storage, it is particularly suitable for fruit-based products with a short shelf life.  相似文献   
50.
The phenolic fraction of virgin olive oil influences both its quality and oxidative stability. One of the principal threats of the quality of olive fruit is the olive fly ( Bactrocera oleae) as it alters the chemical composition. The attack of this olive pest has been studied in order to evaluate its influence on the quality of virgin olive oil (free acidity, peroxide value, fatty acid composition, water content, oxidative stability, phenols, and antioxidant power of phenolic fraction). The study was performed using several virgin olive oils obtained from olives with different degrees of fly infestation. They were acquired in different Italian industrial mills from the Abruzzo region. Qualitative and quantitative analyses of phenolic profiles were performed by capillary electrophoresis-diode array detection, and electrochemical evaluation of the antioxidant power of the phenolic fraction was also carried out. These analyses demonstrated that the degree of fly attack was positively correlated with free acidity ( r = 0.77, p < 0.05) and oxidized products ( r = 0.58, p < 0.05), and negatively related to the oxidative stability index ( r = -0.54, p < 0.05) and phenolic content ( r = -0.50, p < 0.05), mainly with secoiridoid compounds. However, it has been confirmed that the phenolic fraction of olive oil depends on several parameters and that a clear correlation does not exist between the percentages of fly attack and phenolic content.  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