全文获取类型
收费全文 | 456篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
林业 | 28篇 |
农学 | 16篇 |
115篇 | |
综合类 | 25篇 |
农作物 | 12篇 |
水产渔业 | 12篇 |
畜牧兽医 | 219篇 |
园艺 | 3篇 |
植物保护 | 36篇 |
出版年
2023年 | 1篇 |
2022年 | 18篇 |
2021年 | 22篇 |
2020年 | 14篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 16篇 |
2015年 | 21篇 |
2014年 | 30篇 |
2013年 | 33篇 |
2012年 | 19篇 |
2011年 | 30篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 27篇 |
2007年 | 28篇 |
2006年 | 32篇 |
2005年 | 33篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有466条查询结果,搜索用时 15 毫秒
31.
32.
Lingli Yang Naoko H. Miki Naoko Matsuo Guosheng Zhang Linhe Wang Ken Yoshikawa 《农业科学与技术》2014,(3):251-259
duniperus sabina Linnaeus, an evergreen shrub with prostrate life form, can effectively prevent sand moving and is an important tree species for reforestation in semiarid areas of China. It has laterally distributed adventitious roots and a deeply distributed main root system. To detect water movement between the main root system and adventitious roots, we adopted heat pulse sensors using the Heat Ratio Method, a high precision method for measuring low sap flow rates. Two sensors were implanted in each individual in the stem between the main root system and adventitious roots, and another two in lateral stems distal to all the roots. Positive sap flows during nighttime, even under saturated air moisture conditions, were detected only between the main root system and adventitious roots under drought conditions, and the rate of flow increased as drought progressed and decreased or disappeared after rain events. The results demonstrated the existence of water movement from the main root system to adventitious roots, and combined with the high contribution of nighttime sap flow to transpiration (11%-16%) the results indicate that it also involves the process of hydraulic lift, a water movement from moist subsoil to dry surface soils. Integrated water use strategy between the main root system and adventitious roots via the process of hydraulic lift of soil water maximizes water acquisition efficiency from both subsoil water and water from rain pulses on the soil surface; this increases survivability in the water-limited environment of semiarid areas. 相似文献
33.
Biogas production generates digested slurry as a byproduct. It can be used as a fertilizer especially after its conversion into digested liquid. A pot based study was conducted in order to evaluate the effect of the application of digested liquid on CH4 and N2O flux, and plant biomass in paddy. Analysis revealed that digested liquid treated soils released more CH4 compared to ammonium sulphate and the control. Ammonium sulphate treated soil emitted the highest N20 whereas digested liquid application decreased its emission significantly. Further, the cumulative emission over 101 d of the experiment was found to be higher for CHa (16.9 to 29.9 g m^-2) compared to N20 (-49.3 to 18.9 mg m^-2) for all treatments. Digested liquid application had positive impact on plant variables such as panicle number and weight of panicles. This study suggests that digested liquid application significantly decrease N20 emission and increase CH4 emission possibly due to affecting the availability of organic C in the soil to microbial activity for methanogenesis. Another possibility for enhancing CH4 emission by following biogas digested liquid could be attributed to the increase in plant biomass. 相似文献
34.
Genetically modified, herbicide-tolerant (GMHT) Brassica napus plants originating from seed spill have recently been found along roadsides leading from Japanese ports that unload oilseed rape. Such introductions have potential biodiversity effects (as defined by the Cartagena Protocol): these include replacement of native elements in the biota through competitive suppression or hybridization. We conducted surveys in the period 2006–2011 to assess such threats. We examined shifts in the population distribution and occurrence of GMHT plants in 1,029 volunteer introduced assemblages of B. napus, 1,169 of B. juncea, and 184 of B. rapa around 12 ports. GMHT B. napus was found around 10 of 12 ports, but its proportion in the populations varied greatly by year and location. Over the survey period, the distributions of a pure non-GMHT population around Tobata and a pure GMHT population around Hakata increased significantly. However, there was no common trend of population expansion or contraction around the 12 ports. Furthermore, we found no herbicide tolerant B. juncea and B. rapa plants derived from crosses with GMHT B. napus. Therefore, GMHT B. napus is not invading native vegetation surrounding its populations and not likely to cross with congeners in Japanese environment. 相似文献
35.
Yunsheng Lou Lixuan Ren Zhongpei Li Taolin Zhang Kazuyuki Inubushi 《Water, air, and soil pollution》2007,178(1-4):157-168
A pot incubation experiment with rice residues (straw and root) was conducted under aerobic condition (60% of WHC, water holding capacity) for a period of 55 days in a greenhouse. The emissions of carbon dioxide (CO2) and nitrous oxide (N2O) were determined by the closed chamber method in a paddy soil. The soil was derived from quaternary red clay, and collected from the Ecological Station of Red Soil, the Chinese Academy of Sciences, located in Jiangxi Province, a subtropical region of China. The emissions of CO2 and N2O were increased by the amendment of rice residues. Significantly positive correlation was found between N2O and CO2 fluxes (R = 0.650*?0.870*, P ≤ 0.05). The cumulative emissions during the early stage of the incubation (<25 days after residue addition) accounted for about 67%–86% and 67%–80% of the total amount of CO2 and N2O emissions, respectively. Cumulative emissions and emission factors of the two gases were higher in the soils amended with rice straw than those with rice root. The two gas fluxes were positively correlated with microbial biomass C and N, as well as soluble organic C. N2O flux was positively correlated with NH4 +–N content at the early stage (<25 days), and negatively with NO3 ?–N content at the later stage of this incubation (25–55 days), implying that both nitrification and denitrification may have contributed to N2O production. 相似文献
36.
Effects of N sources and methane concentrations on methane uptake potential of a typical coniferous forest and its adjacent orchard soil 总被引:6,自引:0,他引:6
After removal of the above-ground plant debris three different soil layers were taken from a typical coniferous forest and its adjacent orchard in Numata City, Japan. The potentials of soil CH4 uptake at two initial CH4 concentrations were studied under aerobic conditions in the laboratory, along with inhibition of soil CH4 oxidation by urea-N or KNO3-N addition. Due to long-term N inputs, the CH4 uptake of the upper mineral layer of the orchard soil was 25.4% and 87.7% lower than that of the surface forest soil at 2.4 and 12.6 l l–1 CH4, respectively. Methane uptake of the forest soil decreased with increasing soil depths at two CH4 levels. However, maximal CH4-consuming activity occurred in the 9- to 23-cm depth of the orchard soil at 12.6 l l–1 methane. Nitrogen additions in the form of KNO3 or urea at the rate of 200 g N g–1 soil substantially reduced soil CH4 uptake in the upper and sub-surface mineral layers at both sites, except that the addition of KNO3-N had no apparent inhibitory effect on the CH4 uptake in the 9- to 23-cm depth of the orchard soil. A strong inhibitory effect of NO3– addition on the CH4 uptake, in contrast to NH4+, occurred in the surface forest soil. The use of KNO3-N, as compared to urea or urea plus a nitrification inhibitor (dicyandiamide), resulted in a lower potential to cause inhibition of CH4 oxidation in the 0- to 23-cm depth of the orchard soil. 相似文献
37.
Mozammel M. Hoque Kazuyuki Inubushi Shu Miura Kazuhiko Kobayashi Han-Yong Kim Masumi Okada Shingo Yabashi 《Biology and Fertility of Soils》2001,34(6):453-459
An experiment was conducted in an Andosol paddy field in Shizukuishi (Iwate Prefecture, Japan) to determine the effects of free-air CO2 enrichment (FACE) on biological N2-fixation activity and soil microbial biomass C at three levels of N application. Rice (Oryza sativa L. cv. Akitakomachi) plants were grown under ambient CO2 or FACE (ambient +200 µmol mol-1 CO2) conditions throughout the growing season with each treatment having four replicated plots. Three levels of N fertilizer (high, standard and low; 15, 9 and 4 g N m-2, respectively) were applied to examine the effect of different N availability under both CO2 conditions. Soil samples were collected at four different times from upper and lower soil layers (0-1-cm and 1-10-cm soil depths, respectively) and analysed for biological N2-fixation (BNF) activity and microbial biomass C (MBC) by the acetylene reduction and chloroform fumigation-extraction methods, respectively. The amounts of chlorophyll-type compounds (Chls), an index of algal growth, and soil available C were also determined. Compared to the ambient CO2 treatment, the FACE treatment had significantly higher BNF activity in both the upper and lower soil layers at ripening only in low-N soil and at harvest at all three levels of N fertilization rates. MBC was significantly increased by FACE in both the upper and lower soil layers from the middle to later period of the growing season compared to the ambient CO2 treatment. The FACE treatment increased the Chls in the upper soil layers at ripening only in low-N soil and at harvest at all three levels of N fertilization rates. The amount of soil available C was not significantly different between FACE and ambient CO2 treatments in both the upper and lower soil layers throughout the cropping season. From these results it can be concluded that the FACE treatment had a significantly positive influence on BNF activity, MBC and Chls at different levels of N fertilization rates in paddy field during the cropping season. 相似文献
38.
Kazuyuki?Mori Yu?Sakamoto Nobuhiro?Mukojima Seiji?Tamiya Takashi?Nakao Takashige?Ishii Kazuyoshi?HosakaEmail author 《Euphytica》2011,180(3):347-355
Multiplex PCR is practically a reasonable choice for molecular marker-assisted selection in potato breeding. We had developed
and were using a multiplex PCR method for selection of resistance genes to cyst nematode (H1), Potato virus X (Rx1) and late blight (R1 and R2). Since then, more reliable and tightly linked markers for H1 and R2, and a new marker for resistance to Potato virus Y (Ry
chc
) were developed. In this article, all these superior markers, including a positive marker to eliminate PCR-failed samples,
were incorporated into one multiplex PCR assay. Using the newly developed multiplex PCR technique, five plants potentially
harboring all five resistance genes were selected from 96 hybrid plants approximately 5 h after DNA extraction, which is a
third of the operation time compared with separate PCR reactions for each marker. 相似文献
39.
Gonadotropin-releasing hormone: one polypeptide regulates secretion of luteinizing and follicle-stimulating hormones 总被引:9,自引:0,他引:9
A V Schally A Arimura A J Kastin H Matsuo Y Baba T W Redding R M Nair L Debeljuk W F White 《Science (New York, N.Y.)》1971,173(4001):1036-1038
A polypeptide isolated from porcine hypothalami stimulates the release of both luteinizing hormone and follicle-stimulating hormone from the pituitaries of several species. This polypeptide has been structurally identified as (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH(2) and synthesized. The natural and synthetic materials share biological properties. It appears that this peptide represents the hypothalamic hormone regulating the secretion of both luteinizing hormone and follicle-stimulating hormone. 相似文献
40.
Matsuo T Yamaguchi S Mitsui S Emi A Shimoda F Okamura H 《Science (New York, N.Y.)》2003,302(5643):255-259
Cell division in many mammalian tissues is associated with specific times of day, but just how the circadian clock controls this timing has not been clear. Here, we show in the regenerating liver (of mice) that the circadian clock controls the expression of cell cycle-related genes that in turn modulate the expression of active Cyclin B1-Cdc2 kinase, a key regulator of mitosis. Among these genes, expression of wee1 was directly regulated by the molecular components of the circadian clockwork. In contrast, the circadian clockwork oscillated independently of the cell cycle in single cells. Thus, the intracellular circadian clockwork can control the cell-division cycle directly and unidirectionally in proliferating cells. 相似文献