全文获取类型
收费全文 | 304篇 |
免费 | 19篇 |
专业分类
林业 | 30篇 |
农学 | 54篇 |
基础科学 | 2篇 |
38篇 | |
综合类 | 18篇 |
农作物 | 31篇 |
水产渔业 | 4篇 |
畜牧兽医 | 108篇 |
园艺 | 4篇 |
植物保护 | 34篇 |
出版年
2021年 | 6篇 |
2020年 | 6篇 |
2018年 | 6篇 |
2017年 | 15篇 |
2016年 | 6篇 |
2015年 | 8篇 |
2014年 | 4篇 |
2013年 | 16篇 |
2012年 | 15篇 |
2011年 | 15篇 |
2010年 | 14篇 |
2009年 | 6篇 |
2008年 | 6篇 |
2007年 | 24篇 |
2006年 | 7篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1971年 | 5篇 |
1970年 | 4篇 |
1969年 | 2篇 |
1967年 | 5篇 |
1966年 | 2篇 |
排序方式: 共有323条查询结果,搜索用时 15 毫秒
21.
Response of confection sunflower (Helianthus annuus L.) grown in a semi‐arid environment to planting date and early termination of irrigation 下载免费PDF全文
V. R. Joshi J. J. Heitholt A. Garcia y Garcia 《Journal of Agronomy and Crop Science》2017,203(4):301-308
Adjustments on planting date and on the time to terminate irrigation may reduce agricultural water use. However, such management practices in regions with extreme weather conditions have the potential to negatively affect yield. A 3‐year (2012–2014) study was conducted on a clay‐loam soil in a cool, semi‐arid environment to (i) determine the response of confection sunflower to planting date and irrigation termination timing and (ii) identify the relative importance of yield components in irrigated confection sunflower across planting dates. Early May planting had considerable negative effects on all studied variables, except on the percentage of large seeds. The highest yield of total and large seeds was obtained from the late May plantings, averaging 3,777 and 3,379 kg/ha, respectively. None of the irrigation strategies affected the measured variables. However, the interaction between planting date and termination of irrigation significantly affected the 1,000‐seed weight. Our study revealed the last week of May as suitable planting period for confection sunflower in the semi‐arid north‐western region of Wyoming, USA, and that irrigation on heavy soils may be terminated as early as at R5.5 stage without a significant yield reduction. The path‐coefficient analysis indicated head diameter and the number of seeds per head as important traits that significantly influence the yield of confection sunflower across planting dates. 相似文献
22.
Traditional seed management and genetic diversity in barley varieties in high-hill agro-ecosystems of Nepal 总被引:1,自引:0,他引:1
Jwala Bajracharya Anthony H. D. Brown Bal K. Joshi Dipak Panday Bimal K. Baniya Bhuwon R. Sthapit Devra I. Jarvis 《Genetic Resources and Crop Evolution》2012,59(3):389-398
Chawali and Lekali are two common farmer’s barley varieties or landraces in Jumla, Nepal (2,240–3,000 m) with small to bold
grains and wide adaptation from irrigated low lands to high hills. This study was undertaken to test whether features of the
traditional seed system can significantly influence the diversity of a crop and its conservation on-farm. In Jumla (high-hill),
the barley seed system is completely informal and is mainly from farmer to farmer. In the present study, the seed flows and
the pattern of genetic diversity in barley were investigated to detect differences between the two varieties and test the
divergence among populations of each variety These data suggested that Chawali, the more common variety, was less subject
to homogenising gene flow between farms than was Lekali. A total of 128 farming households were surveyed for seed supply information
and 128 populations for each landrace from two villages: Kartikswami and Talium were collected for SSR diversity analysis.
Some 92 SSRs were screened in an initial sample of 20 barley populations of both landraces and 2 improved varieties (LG-51
and Soluwa). Of the 81 SSRs that consistently amplified, only 15 SSRs (19%) were polymorphic with gene diversity values ranging
from 0.09 to 0.71. A medium to low diversity was detected among the landrace populations of barley varieties. Chawali populations
were less polymorphic within ecological groups, and more divergent between than were Lekail populations. This result accords
with Chawali having a more conservative local seed system. 相似文献
23.
Adhikari Sneha Joshi Anjali Kumar Amarjeet Singh Narendra Kumar 《Genetic Resources and Crop Evolution》2021,68(7):2983-2995
Genetic Resources and Crop Evolution - Zea mays ssp. parviglumis is the progenitor of maize and assume to have tolerance against various biotic and abiotic stresses. It... 相似文献
24.
S. R. Joshi 《Water, air, and soil pollution》1988,37(1-2):111-120
The presence of West Valley-derived radionuclides in the densely-populated Niagara River/Lake Ontario region is demonstrated through measurements on water and sediment samples. The 137Cs profile in a 210Pb-dated Lake Ontario sediment core is consistent with the pattern of West Valley discharges to the local aquatic environment in that the observed 137Cs activity maximum corresponds to the 1970 peak discharge and not the 1963 fallout peak activity. Preliminary mass balance estimate, based on a 137Cs/90Sr activity ratio of 1.5 and on the assumption that the dominant regional flow of Lake Erie transports most of the radionuclides to Lake Ontario va the Niagara River, shows that nearly all of the West Valley-delivered 137Cs is deposited in the bottom sediments of Lake Ontario. It is suggested that any accidental releases of radioactivity from the site are likely to provide additional radiation dose to the area residents using municipal water supplies. 相似文献
25.
Summary An Indian hexaploid wheat var. Pb C591 has been shown to carry gene(s) for chlorophyll synthesis on chromosome 3A (Singh & Joshi, 1979). In the present study cv. Pb.C591, its monosomic 3A and diteocentrics for 3A, 3BL and 3DL of var. Chinese Spring have been used. The F2 segregation involving crosses between Pb.C591 as male, monosomic line 3A of Pb.C591 (female) and ditelocentrics 3A, 3BL and 3DL of cv. Chinese Spring as male and female respectively has been observed. It has been found that there are two dominant genes regulating chlorophyll synthesis in cv. Chinese Spring. These genes are located on chromosomes arms 3A and 3DS respectively.These chlorophyll synthetic genes must be the same which were postulated by Sears (1956, 1957) as the normal alleles of virescent gene v
2 (which was located on 3BS) on chromosomes 3A(v
1) and 3D(V
3). 相似文献
26.
G. S. Chaturvedi P. K. Aggarwal A. K. Singh M. G. Joshi S. K. Sinha 《Irrigation Science》1981,2(4):225-235
Summary The effect of irrigation on tillering and tiller mortality in varieties of wheat (Triticum aestivum and T. durum), triticale and barley was studied under field conditions. Low temperature in the early stages of growth promoted production of tillers whereas increase in temperature during extension growth phase increased tiller mortality. More than 1000 tillers m–2 were produced with five irrigations but 40% or more died. With limited water availability tiller production was reduced but so was their mortality. Grain yield in wheat and triticale was positively correlated with productive tillers and negatively correlated with the maximum number of tillers produced in wheat and barley grown under limited irrigation conditions. Varieties with a capacity to produce fewer tillers were identified. Some of them proved more stable in yield. No correlation was found between tiller number and grain yield in the frequently irrigated treatment. 相似文献
27.
The oviposition and development of the grain bettle
Oryzaephilus mercator Faur.on dry fruit meals.
Oryzaephilus mercator showed enormous variation in egg laying on different dry fruit meals (apricot, cashew, almond, groundnut, coconut, fig, date and raisin). The lowest egg period was 4.1 days on almond and the highest on apricot 5.1 days. The egg mortality on various meals differed to a small extent (11.8 to 14.1%). The larval period ranged between 22.7 to 34.3 days. The larval mortality ranged between 7.8% (almond) to 94.4% (raisin). 相似文献
28.
Ratnaboli Bose Shailesh Pandey Pooja Joshi Sabyasachi Banerjee Amit Pandey Maneesh S. Bhandari 《Forest Pathology》2021,51(1):e12658
Eucalyptus spp. and their hybrids are frequently cloned and mass planted across farmland tracts and commercial plantations in northern India. It is a viable feeder species to the paper and pulp industries in this region. In 2018 and 2019, during field surveys conducted in northern India, a serious leaf blight disease was frequently observed in E. tereticornis plantations. Isolation from the blighted leaf samples consistently yielded fungal isolates having Calonectria‐like morphology. Morphological features coupled with sequence analysis of partial β‐tubulin (TUB2) and partial translation elongation factor‐alpha (TEF1) gene regions of two fungal isolates confirmed the species as Ca. cerciana. In detached leaf assays and glasshouse inoculation experiments, both isolates produced symptoms similar to those observed on the naturally infected leaves. Koch's postulates were fulfilled by re‐isolating Ca. cerciana from the inoculated leaves. This work is the first to confirm that Ca. cerciana is associated with a serious leaf blight disease of Eucalyptus in northern India and is an important addition to the taxonomy of Calonectria fungi in India. 相似文献
29.
Climate is a critical factor affecting forest ecosystems and their capacity to produce goods and services. Effects of climate change on forests depend on ecosystem-specific factors including dimensions of climate (temperature, precipitation, drought, wind etc.). Available information is not sufficient to support a quantitative assessment of the ecological, social and economic consequences. The present study assessed shifts in forest cover types of Western Himalayan Eco-region (700?4500 m). 100 randomly selected samples (75 for training and 25 for testing the model), genetic algorithm of rule set parameters and climatic envelopes were used to assess the distribution of five prominent forest cover types (Temperate evergreen, Tropical semi-evergreen, Temperate conifer, Subtropical conifer, and Tropical moist deciduous forests). Modelling was conducted for four different scenarios, current scenario, changed precipitation (8% increase), changed temperature (1.07°C increase), and both changed temperature and precipitation. On increasing precipitation a downward shift in the temperate evergreen and tropical semi-evergreen was observed, while sub-tropical conifer and tropical moist-deciduous forests showed a slight upward shift and temperate conifer showed no shift. On increasing temperature, an upward shift in all forest types was observed except sub-tropical conifer forests without significant changes. When both temperature and precipitation were changed, the actual distribution was maintained and slight upward shift was observed in all the forest types except sub-tropical conifer. It is important to understand the likely impacts of the projected climate change on the forest ecosystems, so that better management and conservation strategies can be adopted for the biodiversity and forest dependent community. Knowledge of impact mechanisms also enables identification and mitigation of some of the conditions that increase vulnerability to climate change in the forest sector. 相似文献
30.
Plant biomass, species diversity and net primary productivity are presented for herb layer of banj oak (Quercus leucotrichophora A. Camus)-chir pine (Pinus roxburghii Sarg.) mixed forest in Kumaun, central Himalaya, India. The species diversity declined from a maximum (3.56) in September to a minimum (2.11) in December. The monthly live shoots biomass exhibited a single peak growth pattern with highest live shoot biomass of 185 g·m-2 in August. The seasonal pattern showed that the maximum above-ground production (131 g·m-2) occurred during the rainy season and the minimum (1 g·m-2) during winter season. The below-ground production was maximum during winter season (84 g·m-2) and minimum during summer season (34 g·m-2). The annual net shoot production was 171 g·m-2 and total below-ground production was 165 g·m-2. Of the total input 61% was channeled to above-ground parts and 39% to below-ground parts. Transfer of live shoots to dead shoots compartments and that of dead shoots to litter compartments was 61% and 66%, respectively. The total dry matter disappearance was 61% of the total input within annual cycle. The herb layer showed a net accumulation of organic matter, indicating the seral nature of the community. 相似文献