全文获取类型
收费全文 | 527篇 |
免费 | 31篇 |
专业分类
林业 | 49篇 |
农学 | 16篇 |
基础科学 | 7篇 |
150篇 | |
综合类 | 36篇 |
农作物 | 23篇 |
水产渔业 | 61篇 |
畜牧兽医 | 156篇 |
园艺 | 21篇 |
植物保护 | 39篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 16篇 |
2019年 | 17篇 |
2018年 | 26篇 |
2017年 | 20篇 |
2016年 | 19篇 |
2015年 | 22篇 |
2014年 | 21篇 |
2013年 | 34篇 |
2012年 | 34篇 |
2011年 | 41篇 |
2010年 | 30篇 |
2009年 | 26篇 |
2008年 | 37篇 |
2007年 | 36篇 |
2006年 | 26篇 |
2005年 | 23篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 16篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1989年 | 3篇 |
1985年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1964年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有558条查询结果,搜索用时 0 毫秒
91.
Giuseppe Piccione Augusto Foà Cristiano Bertolucci Giovanni Caola 《Journal of circadian rhythms》2006,4(1):16-4
Background
In domestic animals many biochemical and physiological processes exhibit daily rhythmicity. The aim of the present study was to investigate the rhythmic pattern of salivary and serum urea concentrations in sheep. 相似文献92.
Giangaspero M Ibata G Savini G Osawa T Tatami S Takagi E Moriya H Okura N Kimura A Harasawa R 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2011,73(12):1629-1633
The first epidemiological survey of Border disease virus (BDV) was undertaken in small ruminants in Japan. Ovine sera, collected from the northern prefectures of Hokkaido, Aomori and Iwate, were examined for the presence of antibodies against BDV using the neutralization peroxidase-linked antibody test. Twenty-nine (17.6%) of one hundred and sixty-five samples were seropositive for BDV. Results were specific, excluding cross-reactions with bovine viral diarrhea virus (BVDV). Only one sample (0.6%) was positive for BVDV, and was negative for BDV. Despite serological evidence of virus circulation, there have been no clinical cases of border disease in sheep in Japan. Although no diagnostic measures were performed, the infection did not appear to be associated with a reduction in ewe fertility nor with lamb mortality. 相似文献
93.
When changing from spatially random to spatially connected appearances as conditions become wetter in their seasonal time dynamics, soil moisture spatial patterns show a behaviour similar to phase transition processes. In a previous work, once implemented an ad-hoc methodology, we have demonstrated that such a phase change shows critical point behaviour. Moreover, the value of the critical probability seems to be an intrinsic characteristic of a catchment, being insensitive to renormalization (rescaling), as well as to model parameterization. 相似文献
94.
95.
In this study, an experimental challenge was carried out by feeding Nero Siciliano pigs with acorn to evoke melanin-like pigmentation and support the hypothesis that it is caused by ingested material. Twelve pigs were studied, 6 fed with acorns and 6 fed commercial feed. At slaughter, all the animals fed on acorns showed black discolouration of almost all lymph nodes. The lymph nodes were normal in size and shape. Histochemical tests performed on tissues allowed us to identify and differentiate the pigment. Immunohistochemical staining for macrophage markers showed macrophages containing a variable amount of melanin-like granules. Our data, and the well-known steps of melanin formation, confirm that swine enzymes could act on phenolic substances found in acorns. 相似文献
96.
97.
Background
The serotonergic system is associated with numerous brain functions, including the resetting of the mammalian circadian clock. The synthesis and metabolism of 5-HT in the brain increases in response to exercise and is correlated with high levels of blood-borne tryptophan (TRP). The present investigation was aimed at testing the existence of a daily rhythm of TRP and 5-HT in the blood of athletic horses. 相似文献98.
Loretta Triberti Anna Nastri Gianni Giordani Franca Comellini Guido Baldoni Giovanni Toderi 《European Journal of Agronomy》2008,29(1):13-20
The soil organic matter content represents a huge reservoir of plant nutrients and an effective safeguard against pollution; beside it can sequestrate atmospheric CO2. Since 1966 up to now in the Southeast Po valley (Italy), the soil organic C (SOC) and total N (TN) dynamics in the 0–0.40 m soil layer under a maize–wheat rainfed rotation are studied as influenced by organic and mineral N fertilizations. Every year in the same plots cattle manure, cattle slurry, and crop residues (i.e. wheat straw and maize stalk) are ploughed under to 0.40 m depth at a same dry matter rate (6.0 and 7.5 t DM ha−1 year−1 after wheat and maize, respectively) and are compared to an unamended control. Each plot is splitted to receive four rates of mineral fertilizer (0–100–200–300 kg N ha−1). In the whole experiment, in 2000 SOC concentration was lower than in 1966 (6.77 and 7.72 g kg−1, respectively), likely for the deeper tillage that diluted SOC and favoured mineralization in deeper soil layer. From 1972 to 2000 SOC stock did not change in the control and N fertilized plots, while it increased at mean rates of 0.16, 0.18, and 0.26 t ha−1 year−1 with the incorporation of residues, slurry and manure, corresponding to sequestration efficiencies of 3.7, 3.8 and 8.1% of added C with the various materials. TN followed the same SOC dynamic, demonstrating how it depends on the soil organic matter. Manure thus confirmed its efficacy in increasing both SOC content and soil fertility on the long-term. In developed countries, however, this material has become scarcely available; slurry management is expensive and implies high environmental risks. Moreover, in a C balance at a farm (or regional) scale, the CO2 lost during manure and slurry stocking should be considered. For these reasons, the incorporation of cereal residues, even if only a little of their C content was found capable of soil accumulation, appears the best way to obtain a significant CO2 sequestration in developed countries. Our long-term experiment clearly shows how difficult it is to modify SOC content. Moreover, because climate and soil type can greatly influence SOC dynamic, to increase CO2 sequestration in cropland, it is important to optimize the fertilization within an agricultural management that includes all the agronomic practices (e.g. tillage, water management, cover crops, etc.) favouring the organic matter build up in the soil. 相似文献
99.
Traditional methods for studying tree roots are destructive and labor intensive, but available nondestructive techniques are applicable only to small scale studies or are strongly limited by soil conditions and root size. Soil electrical resistivity measured by geoelectrical methods has the potential to detect belowground plant structures, but quantitative relationships of these measurements with root traits have not been assessed. We tested the ability of two-dimensional (2-D) DC resistivity tomography to detect the spatial variability of roots and to quantify their biomass in a tree stand. A high-resolution resistivity tomogram was generated along a 11.75 m transect under an Alnus glutinosa (L.) Gaertn. stand based on an alpha-Wenner configuration with 48 electrodes spaced 0.25 m apart. Data were processed by a 2-D finite-element inversion algorithm, and corrected for soil temperature. Data acquisition, inversion and imaging were completed in the field within 60 min. Root dry mass per unit soil volume (root mass density, RMD) was measured destructively on soil samples collected to a depth of 1.05 m. Soil sand, silt, clay and organic matter contents, electrical conductivity, water content and pH were measured on a subset of samples. The spatial pattern of soil resistivity closely matched the spatial distribution of RMD. Multiple linear regression showed that only RMD and soil water content were related to soil resistivity along the transect. Regression analysis of RMD against soil resistivity revealed a highly significant logistic relationship (n = 97), which was confirmed on a separate dataset (n = 67), showing that soil resistivity was quantitatively related to belowground tree root biomass. This relationship provides a basis for developing quick nondestructive methods for detecting root distribution and quantifying root biomass, as well as for optimizing sampling strategies for studying root-driven phenomena. 相似文献
100.
畜禽粪便堆肥腐熟度评价指标体系研究 总被引:22,自引:7,他引:15
以牛粪和猪粪两种畜禽粪便分别与秸秆混合堆肥.全面考察了堆肥过程中与腐熟度有关的理化指标和生物指标变化.结果表明.在3个月的堆肥熟化试验考察期内,堆肥初期堆体升温迅速,50℃上高温持续时间累计超过15 d;物料pH值先升后降,60d后稳定在8.0左右;含水率和C/N持续下降,C/N 60 d后接近20;氨氮含量呈先升后降趋势,胡敏酸和富里酸比值则先降后升;Solvita腐熟等级、种子发芽势和根系建成指标不断升高,而作物生长指标则无显著变化.由腐熟度指标相关性分析表明,最能体现堆肥腐熟程度的Solvita腐熟等级与C/N、种子发芽势、根系建成指标呈高度相关,与含水率和腐殖酸呈低度相关.据此,结合常规温度指标建立了堆肥腐熟度评价指标体系.用于科学指导农牧业废弃物堆肥质量控制. 相似文献