全文获取类型
收费全文 | 340篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
林业 | 30篇 |
农学 | 17篇 |
基础科学 | 3篇 |
193篇 | |
综合类 | 35篇 |
农作物 | 16篇 |
水产渔业 | 13篇 |
畜牧兽医 | 21篇 |
园艺 | 6篇 |
植物保护 | 18篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 34篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 26篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 17篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 15篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有352条查询结果,搜索用时 359 毫秒
81.
B. Lal D. S. Rajput M. B. Tamhankar I. Agarwal M. S. Sharma 《Journal of Agronomy and Crop Science》2003,189(2):57-62
An assessment of the energy requirements of different intensive forage production systems was carried out at the Indian Grassland Fodder, and Agroforestry Research Institute, Jhansi. This included assessment of energy use and output for five intensive crop production systems: (1) sorghum (single‐cut)–berseem, (2) cowpea–sorghum (single‐cut)–berseem + mustard–maize + cowpea, (3) sorghum (multi‐cut)–berseem + oats, (4) guar–oats–maize and (5) sorghum (single‐cut)–wheat–fallow. In all the systems, the Napier bajra hybrid (IGFRI‐3) was transplanted in regular plots of 50 m × 13 m. Results revealed that the total annual energy use was highest for sorghum (multi‐cut)–berseem + oats (36 606 MJ ha?1), followed by sorghum (single‐cut)–berseem + mustard, sorghum (single‐cut)–berseem–cowpea, guar–oats–maize and sorghum (single‐cut)–wheat–fallow (for which values were 31 086, 30 449, 29 867 and 25 956 MJ energy ha?1, respectively). The high value found for sorghum (multi‐cut)–berseem + oats might be attributable to the multi‐cuts in this system. Energy use by fertilizers represented the major part of the total energy use, amounting to 28–38 % in all treatments, followed by energy used in electricity, machinery, seeds, human labour and farmyard manure (FYM), in case of all with slight increase in input. In sorghum–wheat, energy use by seeds occupied the second position, followed by energy used in electricity, human labour, FYM and machinery/diesel. Pesticides contributed the least energy utilization in all the treatments. Herbicides were used for the control of weeds. Among the five forage production systems, sorghum (single‐cut)–berseem + mustard–maize + cowpea was found to be the most energy efficient, followed by sorghum (multi‐cut)–berseem + oats–sorghum (multi‐cut), sorghum (single‐cut)–berseem–cowpea, guar–oats–maize and sorghum (single‐cut)–wheat–fallow. Sorghum (single‐cut)–berseem + mustard–maize + cowpea increased the fertility of the soil, resulting in a higher percentage of organic carbon, higher availability of nitrogen and optimal balancing of the C:N ratio in the upper layers of the soil. These intensive crop production systems also maintain the optimum microbial population in the crop root zone. The benefit–cost ratio (B:C ratio) for the most energy‐efficient forage production system was 1.37 : 1. However, the highest B:C ratio was found in the sorghum–wheat rotation (1: 1.57). 相似文献
82.
Parmeshwar Lal Saran Ravish Choudhary Ishwar Singh Solanki Sezai Ercisli 《Erwerbs-Obstbau》2016,58(3):199-202
The effect of temperature on germination and days taken for germination was evaluated in Carica papaya cvs., ‘Pune selection-3’ and ‘Pusa Dwarf’. The highest average seed germination per cent was observed in the month of July (96.8 and 93.0?%), followed by August (94 and 88.5?%), whereas the lowest average seed germination was observed in the month of January (44.2 and 36.8?%) in ‘Pune selection-3’ and ‘Pusa Dwarf’, respectively. Minimum number of days (5.17 and 6.33) was observed for germination in the month of July, whereas the maximum number of days (29.5 and 31) was taken in the month of January in both the cultivars, respectively. The average highest germination and seedling height was observed at temperature 29.8 °C and 29.5 °C during July and August, respectively, whereas the lowest was observed at temperature 14 °C and 15.9 °C during January and December, respectively. The optimum time for nursery sowing was July to August for autumn season crop under subtropical conditions of India. 相似文献
83.
Soil erosion is widespread in agricultural lands of the US Corn Belt. The objective of this study was to examine the impact of antecedent erosion on loss of soil under laboratory simulated rainfall. The soil was obtained from the surface layer of eroded (ER) and uneroded (UN) sites within a conservation agro‐ecosystem in central Ohio, USA. Air‐dried soil was subjected to a rainfall simulation for 60 min (dry run), and to another simulation (wet run) 24 h after the dry run. In the dry run, the cumulative water runoff, sediment yield, and soil organic carbon loss were higher in ER (12.3 L/m2, 169.3 g/m2, and 5.6 g/m2, respectively) than in the UN (7.3 L/m2, 22.6 g/m2, and 0.9 g/m2 respectively). An opposite trend was observed for the cumulative water infiltration (0.9 and 3.9 L/m2, respectively). In the wet run, despite a similar cumulative water runoff from the two erosional phases (20.1 and 19.6 L/m2 in ER and UN respectively), sediment yield and soil organic carbon loss were higher in ER (484.4 g/m2, and 16.3 g/m2 respectively) than in the UN (146.6 g/m2, and 5.3 g/m2 respectively). Also for the wet run, an opposite trend was observed for the cumulative infiltration (0.8 and 5.8 L/m2 respectively). This study suggests that past erosional processes increase the susceptibility of remaining soil to accelerated erosion. 相似文献
84.
Natural 13C abundance and soil carbon dynamics under long‐term residue retention in a no‐till maize system 下载免费PDF全文
Residue retention and reduced tillage are both conservation agricultural practices that may enhance soil organic carbon (SOC) stabilization in soil. We evaluated the long‐term effects of no‐till (NT) and stover retention from maize on SOC dynamics in a Rayne silt loam Typic Hapludults in Ohio. The six treatments consisted of retaining 0, 25, 50, 75, 100 and 200% of maize residues on each 3 × 3 m plot from the crop of previous year. Soil samples were obtained after 9 yrs of establishing the experiment. The whole soil (0–10 and 10–20 cm of soil depths) samples under different treatments were analysed for total C, total N, recalcitrant C (NaOCl treated sample) and 13C isotopic abundance (0–10 cm soil depth). Complete removal of stover for a period of 9 yrs significantly (P < 0.01) decreased soil C content (15.5 g/kg), whereas 200% of stover retention had the maximum soil C concentration (23.1 g/kg). Relative distribution of C for all the treatments in different fractions comprised of 55–58% as labile and 42–45% as recalcitrant. Retention of residue did not significantly affect total C and N concentration in 10–20 cm depth. 13C isotopic signature data indicated that C4‐C (maize‐derived C) was the dominant fraction of C in the top 0–10 cm of soil layer under NT with maize‐derived C accounting for as high as 80% of the total SOC concentration. Contribution of C4‐C or maize‐derived C was 71–84% in recalcitrant fraction in different residue retained plots. Residue management is imperative to increase SOC concentrations and long‐term agro‐ecosystem necessitates residue retention for stabilizing C in light‐textured soils. 相似文献
85.
In India, a single soil loss tolerance ( T ) value of 11.2 Mg/ha is by default used for formulating land restoration strategies for all soil types, climates and vegetation covers. However, this single 'T' value does not represent a true picture of soil loss tolerance under all land uses. The objective of our study was to develop adjusted ' T ' values for Central India using soil infiltration rate, bulk density, total organic carbon, erodibility and soil pH. Soil state was defined using a quantitative model involving different soil functions which were used to convert soil parameters to a 0 to 1 scale. The normalized values were then multiplied by appropriate weighing factors based on relative importance and sensitivity analysis of each indicator. Based on overall assessment, each soil mapping unit was categorized into soil groups I, II or III. A general guideline of USDA – Natural Resource Conservation Service (USDA-NRCS) was followed to calculate soil loss tolerance for each soil group using effective soil depth. Adjusted ' T ' values for Central India ranged from 2.5 to 12.5 Mg/ha compared with a default value of 11.2 Mg/ha. Use of these values for soil mapping units will improve conservation planning and assist with planning the development of sustainable agriculture. 相似文献
86.
The possible anti-inflammatory activity of the 90% ethanolic extract of Dalbergia sissoo leaves (DSELE) was studied in different models of inflammation in rats after oral administration at doses of 100, 300 and 1000 mg/kg. DSELE significantly inhibited carrageenin, kaolin and nystatin-induced paw oedema, as well as the weight of granuloma induced by a cotton pellet. It also inhibited dye leakage in acetic acid-induced vascular permeability test in mice. DSELE was devoid of ulcerogenic effect on the gastric mucosa of rats in acute and chronic tests. In acute toxicity studies, it was found to be safe up to 10.125 g/kg, p.o. in the rat. It was concluded that the D. sissoo leaf extract possessed significant anti-inflammatory activity (in acute, sub-acute and chronic models of inflammation) without any side effect on gastric mucosa. 相似文献
87.
O. P. Lal 《Journal of pest science》1977,50(2):28-29
Hibernation of the beetles, Altica caerulescens Baly and Macrima armata Baly in the Kula Valley, Himachal Pradesh
The flea beetle,Altica caerulescens Baly, is a pest of bringjal, tomato, spinach, strawberry and the weedsRumex sp. andImpatiens sp. in India. The beetle,Macrima armata Baly attacks the trees ofAlnus nitida and is also found as a minor pest of radish in Kulu Valley. Both of the beetles are found only in summer. Concerning the overwintering formerly it was supposed thatA. caerulescens hibernates in pupal stage. The autor describes for the first time about the overwintering of the two species in Kulu Valley based on a survey conducted in 1972 to 1975.
Altica caerulescens hibernates in adult stage under the bark of willow (Salix alba).Macrima armata adults were found in the winter in cracks of Kosh trees (Alnus nitida). 相似文献
88.
89.
R. Lal 《Agroforestry Systems》1989,8(1):7-29
Field experiments were conducted on a tropical Alfisol at Ibadan, Nigeria, to evaluate the effects on soil moisture and crop yields of three agroforestry systems. Effects of agroforestry treatments involving two perennial shrubs (Leucaena leucocephala and Gliricidia sepium), each at 2-m and 4-m row spacings, were compared with no-till and plow-till systems of seedbed preparation. Measurements were made for soil properties, runoff and erosion, nutrient losses in runoff, and crop growth and yield for a uniform maize (Zea mays) and cowpea (Vigna unguiculata) rotation. All of the six plots, each measuring 70 × 10m, were established on a natural slope of about 7%. Alterations in soil properties and effects on crop growth were evaluated for six consecutive years from 1982 through 1987.Seed germination and seedling establishment of Leucaena hedgerows were satisfactory while establishment of Gliricidia from stem cuttings was unsatisfactory. Maize germination and crop stand were normal while that of cowpea were suppressed by both Leucaena and Gliricidia. Maize growth and yield were suppressed only in the vicinity of hedgerows. Maize grain yield in agroforestry systems averaged about 10 percent lower than that of the control. In contrast with maize, agroforestry systems drastically suppressed cowpea grain yield. The average cowpea yield in agroforestry systems was 30 to 50% of the control. Regardless of the mangement system, grain yields declined over time at the rate of 340 and 96 kg ha–1yr–1 for maize and cowpea, respectively.Hedgerows of Leucaena and Gliricidia acted as windbreaks. Consequently, soil moisture content in the top 0–5 cm layer in agroforestry systems was generally higher than that in the control during both wet and dry seasons. 相似文献
90.
Summary Intra-increment circumferential variation in tracheid length at breast-height in deodar (Cedrus deodara (Roxb.) Loud. vern. diar) has been studied with the main objective of evolving an efficient sampling procedure for the purpose of comparing tracheid length amongst individual trees of forest stands. It has been studied in five sampling strata namely: whole-annual ring, whole-earlywood, whole-latewood, first-firmed earlywood and last-formed latewood. Tracheid length shows significant circumferential variation in whole-annual ring, whole-earlywood, whole-latewood and last-formed latewood. However, when the mean tracheid length of two opposite directions is compared with the mean tracheid length of eight cardinal directions in these sampling strata, then no significant difference is observed. First-formed stratum of an annual ring exhibits statistically consistent values around the circumference and thus sampling from any random radial direction can serve the purpose for the comparison of inherent values of tracheid length amongst the deodar trees.The financial assistance given by Himachal Pradesh University as H.P.U. Junior Research Fellowship to second author is highly acknowledged 相似文献