全文获取类型
收费全文 | 5614篇 |
免费 | 241篇 |
国内免费 | 8篇 |
专业分类
林业 | 480篇 |
农学 | 207篇 |
基础科学 | 51篇 |
1323篇 | |
综合类 | 726篇 |
农作物 | 248篇 |
水产渔业 | 357篇 |
畜牧兽医 | 1880篇 |
园艺 | 170篇 |
植物保护 | 421篇 |
出版年
2023年 | 28篇 |
2022年 | 52篇 |
2021年 | 97篇 |
2020年 | 111篇 |
2019年 | 137篇 |
2018年 | 104篇 |
2017年 | 124篇 |
2016年 | 130篇 |
2015年 | 92篇 |
2014年 | 145篇 |
2013年 | 264篇 |
2012年 | 319篇 |
2011年 | 392篇 |
2010年 | 246篇 |
2009年 | 201篇 |
2008年 | 342篇 |
2007年 | 341篇 |
2006年 | 358篇 |
2005年 | 357篇 |
2004年 | 317篇 |
2003年 | 292篇 |
2002年 | 306篇 |
2001年 | 76篇 |
2000年 | 70篇 |
1999年 | 86篇 |
1998年 | 66篇 |
1997年 | 54篇 |
1996年 | 52篇 |
1995年 | 44篇 |
1994年 | 27篇 |
1993年 | 44篇 |
1992年 | 36篇 |
1991年 | 35篇 |
1990年 | 38篇 |
1989年 | 43篇 |
1988年 | 37篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 34篇 |
1984年 | 22篇 |
1983年 | 34篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1974年 | 15篇 |
1973年 | 18篇 |
1972年 | 14篇 |
排序方式: 共有5863条查询结果,搜索用时 15 毫秒
61.
62.
Katja N. Koeppel Peter Geertsma Brian F. Kuhn Ockert L. van Schalkwyk Peter N. Thompson 《The Onderstepoort journal of veterinary research》2022,89(1)
Rabies is a zoonotic disease that remains endemic in large parts of southern Africa because of its persistence in wildlife and domestic dog vectors. The black-backed jackals (Canis mesomelas) is primarily the wildlife vector responsible for rabies outbreaks in northern parts of South Africa. Two trials were carried out to investigate antibody responses to the oral rabies vaccine Raboral V-RG® in black-backed jackals under captive and free-ranging conditions. In captive jackals 10/12 (83%; 95% confidence interval [CI]: 52% – 98%), seroconverted after single oral vaccination. Nine captive jackals had protective antibody titres (> 0.5 IU/mL) at 4 weeks (median: 2.1 IU/mL; inter quartile range [IQR]: 0.6–5.7) and 10 jackals had at 12 weeks (median: 3.5 IU/mL; IQR: 1.5–8.3) and three maintained antibody titres for up to 48 weeks (median: 3.4 IU/mL; IQR: 2.0–6.3). Four sites were baited with Raboral V-RG® vaccine for wild jackals, using fishmeal polymer and chicken heads. Baits were distributed by hand or from vehicle at three sites in north-eastern South Africa, with an average baiting density of 4.4 baits/km2 and at one site in central South Africa, at 0.12 baits/km2. This resulted in protective antibody titres in 3/11 jackals (27%; 95% Cl: 6–61) trapped between 3 and 12 months after baiting in north-eastern South Africa, compared with 4/7 jackals (57%; 95% Cl: 18–90) trapped after 3–18 months in central South Africa. This study shows the potential utility of oral rabies vaccination for the control of wildlife-associated rabies in north-eastern and central South Africa, but extensive studies with wider distribution of bait are needed to assess its potential impact on rabies control in wild jackals. 相似文献
63.
64.
过去人们常认为,由于刚出壳雏鸡的免疫系统尚未发育成熟,同时肠道内缺乏有益的微生物,因而处于高度的敏感期,此时接种沙门氏菌苗产生的保护作用很有限。然而,最新的研究表明,在这些敏感期接种疫苗,可诱发产生保护作用。 相似文献
65.
Ning ZHANG Dong GUO Ye ZHU Xiaomi WANG Lingjia ZHU Fang LIU Ying TENG Peter CHRISTIE Zhengao LI Yongming LUO 《土壤圈》2020,30(4):563-569
Pentachloronitrobenzene (PCNB) is an organochlorine fungicide that is mainly used in the prevention and control of diseases in crop seedlings. Microbial removal is used as a promising method for in-situ removal of many organic pesticides and pesticide residues. A short-term field experiment (1 year) was conducted to explore the potential role of a PCNB-degrading bacterial isolate, Cupriavidus sp. YNS-85, in the remediation of a PCNB-contaminated soil on which Panax notoginseng was grown. The following three treatments were used:i) control soil amended with wheat bran but without YNS-85, ii) soil with 0.15 kg m-2 of solid bacterial inoculum (A), and iii) soil with 0.30 kg m-2 of solid bacterial inoculum (B). The removal of soil PCNB during the microbial remediation was monitored using gas chromatography. Soil catalase and fluorescein diacetate (FDA) esterase activities were determined using spectrophotometry. In addition, cultivable bacteria, fungi, and actinomycetes were counted by plating serial dilutions, and the microbial biodiversity of the soil was analyzed using BIOLOG. After 1 year of in-situ remediation, the soil PCNB concentrations decreased significantly by 50.3% and 74.2% in treatments A and B, respectively, when compared with the uninoculated control. The soil catalase activity decreased in the presence of the bacterial isolate, the FDA esterase activity decreased in treatment A, but increased in treatment B. No significant changes in plant biomass, diversity of the soil microbial community, or physicochemical properties of the soil were observed between the control and inoculated groups (P<0.05). The results indicate that Cupriavidus sp. YNS-85 is a potential candidate for the remediation of PCNB-contaminated soils under P. notoginseng. 相似文献
66.
Soil depth plays a decisive role in determining soil properties in mountainous regions for ecological site assessment. To evaluate the use of ground‐penetrating radar (GPR) for fast and high‐resolution mapping within mountainous regions, we examined the possibilities and limitations of GPR to determine soil depth over bedrock and to delineate individual substrate layers formed during the Pleistocene in a periglacial environment (Pleistocene periglacial slope deposits, PPSD). Selected catenae in representative subregions of the study area (Dill catchment, SE Rhenish Massif, Germany) have been successfully mapped using GPR. A practicable method was developed using a 400 MHz antenna to reach a mean penetration depth of 1.5 m and to map different substrates and layers of PPSD based on calibrations of the GPR at soil pits along 12 catenae. Colluvium, the three types of PPSD layers, as well as the in situ bedrock could be distinguished in most sections of the GPR surveys. Characteristic GPR facies caused by intrinsic material properties of the different substrates, such as stone content and soil moisture content, could be distinguished in different geomorphologic and lithological settings. A layer‐based velocity distribution was determined for characteristic substrate layers at soil pits enabling us to considerably enhance the accuracy of soil‐depth prediction. Compared to traditionally surveyed soil profiles, our results demonstrate an accuracy of layer thickness surveying within a standard deviation of approx. 0.1 m. It is demonstrated that the combination of GPR with conventional soil‐pit mapping is an efficient and valid method to produce high‐resolution data of substrate distribution. 相似文献
67.
Cell wall proteins (CWPs) play a vital role in the development of the different morphological stages including mycelium, fruiting body, and sclerotium in mushrooms which are important human food sources. Using fractionation by detergents and reducing agents, mushroom cell wall fractions from the different developmental stages of Pleurotus tuber-regium (PTR) were prepared. Using one-dimensional gel electrophoresis coupled with LC-MS, there were 103, 91, and 48 noncovalently linked CWPs identified in the cell wall fractions of the PTR mycelium, fruiting body, and sclerotium, respectively. Comparing the CWPs in these cell wall fractions, 19 of them were in common, among which 17 belonged to the functional categories of translation, ribosomal structure, and biogenesis. This is the first study to provide important biochemical insights into the different developmental stages of PTR mediated by CWPs, and the identified CWPs helped to explain the morphological changes of PTR mushrooms during cultivation. 相似文献
68.
Ingeborg F. Pedersen Peter Srensen Jim Rasmussen Paul J. A. Withers Gitte Holton Rubk 《植物养料与土壤学杂志》2019,182(4):541-551
We investigated the interacting effects of inorganic nitrogen and the main inorganic phosphorus form in dairy manure (dicalcium phosphate, CaHPO4) on growth, nutrient uptake, and rhizosphere pH of young maize plants. In a pot experiment, three levels of CaHPO4 (0, 167, and 500 mg P pot?1) were combined with nitrogen (637 mg N pot?1) applied at five NH4‐N : NO3‐N ratios (0 : 100, 25 : 75, 50 : 50, 75 : 25, and 100 : 0) and a nitrification inhibitor in a concentrated layer of a typical acid sandy soil from Denmark. 15N‐labeled NH4‐N was applied to differentiate the role of nitrification and to partition nitrogen uptake derived from NH4‐N. Among treatments including nitrogen, shoot biomass, rooting and phosphorus uptake were significantly higher at the five‐leaf stage when CaHPO4 was applied with NH4‐N : NO3‐N ratios of 50 : 50 and 75 : 25. In these treatments, rhizosphere pH dropped significantly in direct proportion with NH4‐N uptake. The fertilizers in the concentrated layer had a root‐inhibiting effect in treatments without phosphorus supply and in treatments with pure NO3‐N or NH4‐N supply. Increased nitrogen uptake as NH4‐N instead of NO3‐N reduced rhizosphere pH and enhanced acquisition of applied CaHPO4 by young maize plants, which may have positive implications for the enhanced utilization of manure phosphorus. 相似文献
69.
Combining agent-based and stock-flow modelling approaches in a participative analysis of the integrated land system in Reichraming, Austria 总被引:1,自引:0,他引:1
Veronika Gaube Christina Kaiser Martin Wildenberg Heidi Adensam Peter Fleissner Johannes Kobler Juliana Lutz Andreas Schaumberger Jakob Schaumberger Barbara Smetschka Angelika Wolf Andreas Richter Helmut Haberl 《Landscape Ecology》2009,24(9):1149-1165
The integrated modelling of coupled socio-ecological systems in land-change science requires innovative model concepts capable of grasping the interrelations between socioeconomic and natural components. Here, we discuss the integrated socio-ecological model SERD (Simulation of Ecological Compatibility of Regional Development) that was developed for the municipality of Reichraming in Upper Austria in a participative 2-year process involving local stakeholders. SERD includes three main components: (1) an agent-based actors module that simulates decisions of farmsteads, the municipal administration and other important actors; (2) a spatially explicit (GIS based) land-use module that simulates land-use change at the level of individual parcels of land and (3) an integrated socio-ecological stock-flow module that simulates carbon and nitrogen flows through both socioeconomic and ecological system compartments. We report on outcomes of a scenario analysis that outlines possible future trajectories depending on both external (e.g. agricultural subsidies and prices) and internal (e.g. innovation, willingness to co-operate) factors. We find that both external and internal factors can affect the behaviour of the integrated system considerably. Local and regional policies are found to be able to counteract adverse global socioeconomic conditions to some extent, but not to reverse the trend altogether. We also find strong interdependencies between socioeconomic and ecological components of the system. Fully evaluating these interdependencies is, however, not possible at the local scale alone and will require explicit consideration of higher-level effects in future research. 相似文献
70.
Combining top-down and bottom-up dynamics in land use modeling: exploring the future of abandoned farmlands in Europe with the Dyna-CLUE model 总被引:9,自引:0,他引:9
Land use change is the result of interactions between processes operating at different scales. Simulation models at regional
to global scales are often incapable of including locally determined processes of land use change. This paper introduces a
modeling approach that integrates demand-driven changes in land area with locally determined conversion processes. The model
is illustrated with an application for European land use. Interactions between changing demands for agricultural land and
vegetation processes leading to the re-growth of (semi-) natural vegetation on abandoned farmland are explicitly addressed.
Succession of natural vegetation is simulated based on the spatial variation in biophysical and management related conditions,
while the dynamics of the agricultural area are determined by a global multi-sector model. The results allow an exploration
of the future dynamics of European land use and landscapes. The model approach is similarly suitable for other regions and
processes where large scale processes interact with local dynamics. 相似文献