全文获取类型
收费全文 | 181篇 |
免费 | 6篇 |
专业分类
林业 | 15篇 |
农学 | 5篇 |
基础科学 | 1篇 |
37篇 | |
综合类 | 27篇 |
农作物 | 33篇 |
水产渔业 | 1篇 |
畜牧兽医 | 64篇 |
植物保护 | 4篇 |
出版年
2023年 | 3篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 27篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1967年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
1958年 | 2篇 |
1957年 | 2篇 |
1956年 | 1篇 |
1955年 | 5篇 |
1954年 | 1篇 |
1953年 | 1篇 |
1950年 | 1篇 |
1948年 | 1篇 |
1946年 | 2篇 |
1945年 | 1篇 |
1944年 | 1篇 |
1943年 | 2篇 |
1942年 | 3篇 |
1940年 | 1篇 |
1939年 | 1篇 |
1936年 | 2篇 |
1934年 | 1篇 |
1932年 | 1篇 |
1930年 | 1篇 |
1929年 | 1篇 |
1927年 | 2篇 |
排序方式: 共有187条查询结果,搜索用时 15 毫秒
11.
Comparisons of energy balance and evapotranspiration between flooded and aerobic rice fields in the Philippines 总被引:3,自引:0,他引:3
Ma. Carmelita R. Alberto Reiner Wassmann Takashi HiranoAkira Miyata Ryusuke HatanoArvind Kumar Agnes PadreModesto Amante 《Agricultural Water Management》2011,98(9):1417-1430
The seasonal and annual variability of sensible heat flux (H), latent heat flux (LE), evapotranspiration (ET), crop coefficient (Kc) and crop water productivity (WPET) were investigated under two different rice environments, flooded and aerobic soil conditions, using the eddy covariance (EC) technique during 2008-2009 cropping periods. Since we had only one EC system for monitoring two rice environments, we had to move the system from one location to the other every week. In total, we had to gap-fill an average of 50-60% of the missing weekly data as well as those values rejected by the quality control tests in each rice field in all four cropping seasons. Although the EC method provides a direct measurement of LE, which is the energy used for ET, we needed to correct the values of H and LE to close the energy balance using the Bowen ratio closure method before we used LE to estimate ET. On average, the energy balance closure before correction was 0.72 ± 0.06 and it increased to 0.99 ± 0.01 after correction. The G in both flooded and aerobic fields was very low. Likewise, the energy involved in miscellaneous processes such as photosynthesis, respiration and heat storage in the rice canopy was not taken into consideration.Average for four cropping seasons, flooded rice fields had 19% more LE than aerobic fields whereas aerobic rice fields had 45% more H than flooded fields. This resulted in a lower Bowen ratio in flooded fields (0.14 ± 0.03) than in aerobic fields (0.24 ± 0.01). For our study sites, evapotranspiration was primarily controlled by net radiation. The aerobic rice fields had lower growing season ET rates (3.81 ± 0.21 mm d−1) than the flooded rice fields (4.29 ± 0.23 mm d−1), most probably due to the absence of ponded water and lower leaf area index of aerobic rice. Likewise, the crop coefficient, Kc, of aerobic rice was significantly lower than that of flooded rice. For aerobic rice, Kc values were 0.95 ± 0.01 for the vegetative stage, 1.00 ± 0.01 for the reproductive stage, 0.97 ± 0.04 for the ripening stage and 0.88 ± 0.03 for the fallow period, whereas, for flooded rice, Kc values were 1.04 ± 0.04 for the vegetative stage, 1.11 ± 0.05 for the reproductive stage, 1.04 ± 0.05 for the ripening stage and 0.93 ± 0.06 for the fallow period. The average annual ET was 1301 mm for aerobic rice and 1440 mm for flooded rice. This corresponds to about 11% lower total evapotranspiration in aerobic fields than in flooded fields. However, the crop water productivity (WPET) of aerobic rice (0.42 ± 0.03 g grain kg−1 water) was significantly lower than that of flooded rice (1.26 ± 0.26 g grain kg−1 water) because the grain yields of aerobic rice were very low since they were subjected to water stress.The results of this investigation showed significant differences in energy balance and evapotranspiration between flooded and aerobic rice ecosystems. Aerobic rice is one of the promising water-saving technologies being developed to lower the water requirements of the rice crop to address the issues of water scarcity. This information should be taken into consideration in evaluating alternative water-saving technologies for environmentally sustainable rice production systems. 相似文献
12.
Dorn C Schroeter A Helmuth R 《Berliner und Münchener tier?rztliche Wochenschrift》2002,115(7-8):252-258
The National Salmonella Reference Laboratory (NRL-Salm) of the Federal Institute for Health Protection of Consumers and Veterinary Medicine receives putative Salmonella isolates originating from animals, food, feed and the environment for typing. This report summarises the results of the sero- and phagetyping studies. In livestock S. Typhimurium DT 104 with 24% and S. Enteritidis PT 4 with 9% of all isolations predominate like in the human isolates. These sero- and phagetypes are frequently isolated from food as well and consequently can reach the consumer via the food chain. 相似文献
13.
Variation in clinical and parasitological traits in Pietrain and Meishan pigs infected with Sarcocystis miescheriana 总被引:1,自引:0,他引:1
Reiner G Eckert J Peischl T Bochert S Jäkel T Mackenstedt U Joachim A Daugschies A Geldermann H 《Veterinary parasitology》2002,106(2):99-113
Future prophylaxis needs new concepts, including natural disease resistance of hosts against infectious agents. Genomic approaches to detect and improve disease resistance in farm animals and the molecular mechanisms involved in host-parasite interactions depend to a high degree on the trait differences between founder breeds, i.e. on the animal model. The present study evaluates differences in susceptibility/resistance against Sarcocystis miescheriana in the European Pietrain (PI) and the Chinese Meishan (ME) pig breeds, based on 25 individuals, infected orally with 5x10(4) sporocysts of S. miescheriana. Significant differences appeared in clinical, serological, haematological and parasitological findings. The major discriminating period post infection (p.i.) was between days 42 and 45. Severity of signs was negatively correlated with specific immunoglobulin titres during the first 3 weeks p.i. and positively with the load of bradyzoites in muscle tissues of the pigs. Loads of bradyzoites in muscle tissues were 20 times higher in PI than in ME. Sarcocystis-specific differences between the two breeds were in the range of 1-2 standard deviations. The study lays the foundation for further experiments to analyse chromosomal regions, candidate genes, and thus the molecular basis of Sarcocystis susceptibility/resistance as a model for host-parasite interaction in protozoan infectious disease. 相似文献
14.
Aristotelis C. Papageorgiou Reiner Finkeldey Hans H. Hattemer Sotirios Xenopoulos 《European Journal of Forest Research》2005,124(2):119-124
Individuals were selected for resistance against the imperfect fungus Seiridium cardinale Wag in six common cypress populations (Cupressus sempervirens L.) in Greece. A total of 109 resistant clones and 140 trees from their base populations were surveyed at several allozyme loci. The comparison yielded information on changes in genetic variation due to artificial selection. The genetic structure of the breeding populations was similar to their base populations. Nevertheless, the number of rare alleles among the resistant clones had decreased, showing a similar trend at most loci and for most comparisons. Possible implications for breeding strategies are discussed. 相似文献
15.
Marcel Suchowski Michael Eschbaumer Jens P. Teifke Reiner Ulrich 《Journal of veterinary diagnostic investigation》2021,33(5):997
Foot-and-mouth disease (FMD) is a highly contagious aphthoviral infection of cloven-hoofed animals, inducing vesiculopustular stomatitis, pododermatitis, and thelitis. Vesicular fluid represents a major pathway of virus excretion, but bovine milk is another important source of virus shedding. We describe here the time course of FMD virus (FMDV) excretion in the milk and characterize associated lesions in the mammary gland. Three dairy cows were infected by nasopharyngeal instillation of FMDV and monitored over 12 d. Autopsy was performed at the end of the study, and specimens were collected for histopathology, IHC, and RT-qPCR. All 3 cows developed fever, drooling, vesiculopustular stomatitis, interdigital dermatitis, and thelitis. FMDV RNA was detectable in whole milk until the end of the trial, but only transiently in saliva, nasal secretions, and blood serum. Although histology confirmed vesiculopustular lesions in the oral and epidermal specimens, the mammary glands did not have unequivocal evidence of FMDV-induced inflammation. FMDV antigen was detectable in skin and oral mucosa, but not in the mammary gland, and FMDV RNA was detectable in 9 of 29 samples of squamous epithelia but only in 1 of 12 samples of mammary gland. 相似文献
16.
Effect of increasing nitrogen fertilization on copper demand in cereals Pot experiments were conducted with wheat (2 experiments) and spring barley (1 experiment) in a peat soil. Four N and four Cu fertilizer levels were chosen in such a way that, based on grain yield, within each N level there was a Cu deficient and a Cu sufficient treatment. For sufficient Cu supply, Cu level in soil and plant increased with increasing N level. Critical Cu concentrations in aboveground biomass at shooting [μg (g dw)?1] were 3.5 (lowest N level = N1) to 7.5 (highest N level = N4) for grain production of wheat and barley, but for aboveground biomass of wheat at shooting they were only 2.6 (N1) to 5.8 (N4). Based on critical Cu concentration at different N levels, critical Cu/N ratios were determined. These were independent from N level, indicating that Cu remobilization in the older leaves is unlikely even at N deficiency. The high critical Cu concentrations at high N levels may be explained by an increased immobilization of Cu. Under Cu deficient conditions, Cu concentration did not increase with increasing N level. However, under Cu sufficient conditions, N concentration and Cu concentration of the plant increased with increasing N level. The increasing Cu uptake with increasing N level may be explained by the release of amines into the root apoplast and the rhizosphere. Particularly under Cu sufficient conditions, these may mobilize Cu by formation of soluble Cu-amine complexes. 相似文献
17.
Reiner L 《Science (New York, N.Y.)》1930,72(1871):483-484
18.
Mullen AC High FA Hutchins AS Lee HW Villarino AV Livingston DM Kung AL Cereb N Yao TP Yang SY Reiner SL 《Science (New York, N.Y.)》2001,292(5523):1907-1910
How cytokines control differentiation of helper T (TH) cells is controversial. We show that T-bet, without apparent assistance from interleukin 12 (IL-12)/STAT4, specifies TH1 effector fate by targeting chromatin remodeling to individual interferon-gamma (IFN-gamma) alleles and by inducing IL-12 receptor beta2 expression. Subsequently, it appears that IL-12/STAT4 serves two essential functions in the development of TH1 cells: as growth signal, inducing survival and cell division; and as trans-activator, prolonging IFN-gamma synthesis through a genetic interaction with the coactivator, CREB-binding protein. These results suggest that a cytokine does not simply induce TH fate choice but instead may act as an essential secondary stimulus that mediates selective survival of a lineage. 相似文献
19.
Frauke Kleemann Maximilian von Fragstein Barbara Vornam Annika Müller Christoph Leuschner Andrea Holzschuh Teja Tscharntke Reiner Finkeldey Andrea Polle 《European Journal of Forest Research》2011,130(5):707-716
Knowledge on phenological, morphometric, and phytochemical variation of local progenies of European aspen (Populus tremula, L.) is limited. The goal of this study was to characterize variation in growth and ecologically important leaf properties
in aspen full-sib families in relation to interacting organisms (mycorrhiza, endophytes, and insects) and to determine whether
these interactions were affected by soil application of a systemic fungicide. In local progenies, within-family variation
of neutral molecular genetic markers (nuclear microsatellites) was higher than between families. Significant variation in
growth, production of phenolic defensive compounds and other phytochemical leaf traits was found between families. Phenolic
compounds showed clear negative correlation with generalist herbivores, but did not result in negative trade-off with biomass
production. Differences in mycorrhizal colonization were not found among full-sib families and application of a systemic fungicide
suppressed neither mycorrhizal colonization nor infestation with insects. However, a strong suppression of endophytes occurred,
whose long-term consequences may require attention when fungicides are used in agroforestry plantations. 相似文献
20.
A greenhouse experiment was conducted by growing oats (Avenasativa L.) in a continuously 13CO2 labeled atmosphere. The allocation of 13C-labeled photosynthates in plants, microbial biomass in rhizosphere and root-free soil, pools of soil organic C, and CO2 emissions were examined over the plant's life cycle. To isolate rhizosphere from root-free soil, plant seedlings were placed into bags made of nylon monofilament screen tissue (16 μm mesh) filled with soil. Two peaks of 13C in rhizosphere pools of microbial biomass and dissolved organic carbon (DOC), as well as in CO2 emissions at the earing and ripeness stages were revealed. These 13C maxima corresponded to: (i) the end of rapid root growth and (ii) beginning of root decomposition, respectively. The δ13C values of microbial biomass were higher than those of DOC and of soil organic matter (SOM). The microbial biomass C accounted for up to 56 and 39% of 13C recovered in the rhizosphere and root-free soil, respectively. Between 4 and 28% of 13C assimilated was recovered in the root-free soil. Depending on the phenological stage, the contribution of root-derived C to total CO2 emission from soil varied from 61 to 92% of total CO2 evolved, including 4-23% attributed to rhizomicrobial respiration. While 81-91% of C substrates used for microbial growth in the root-free soil and rhizosphere came from SOM, the remaining 9-19% of C substrates utilized by the microbial biomass was attributable to rhizodeposition. The use of continuous isotopic labelling and physical separation of root-free and rhizosphere soil, combined with natural 13C abundance were effective in gaining new insight on soil and rhizosphere C-cycling. 相似文献