全文获取类型
收费全文 | 475篇 |
免费 | 18篇 |
专业分类
林业 | 51篇 |
农学 | 64篇 |
基础科学 | 8篇 |
101篇 | |
综合类 | 33篇 |
农作物 | 22篇 |
水产渔业 | 39篇 |
畜牧兽医 | 120篇 |
园艺 | 26篇 |
植物保护 | 29篇 |
出版年
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 15篇 |
2019年 | 6篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 19篇 |
2013年 | 43篇 |
2012年 | 26篇 |
2011年 | 30篇 |
2010年 | 21篇 |
2009年 | 22篇 |
2008年 | 24篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 8篇 |
1966年 | 6篇 |
排序方式: 共有493条查询结果,搜索用时 15 毫秒
61.
Early results from three test plantings of Casuarina equisetifolia spp. equisetifolia are reported: a clonal test of 40 locally selected clones, a progeny test of 16 wind-pollinated families of local origin, and a family-in-provenance test of 100 wind-pollinated families which is part of an international provenance trial. All tests were planted in 1996 at the Regional Forest Research Centre, Rajahmundry, Andhra Pradesh, India. Height, stem straightness and axis persistence were measured in the family tests at 6 and 12 months of age. The height of the clonal test was measured at 12 months of age. Heritability estimates obtained were ca. 0.3, 0.2 and 0.1 for height, stem straightness and axis persistence, respectively. Heritability estimates for height were reasonably consistent across the three tests; however, estimates for stem straightness and axis persistence were generally higher in the small test of locally selected families. Height and the other two traits are most probably either weakly correlated or uncorrelated, while stem straightness and axis persistence are positively correlated. Provenances spread across the range of natural- and land-race populations tested demonstrated good growth potential at Rajahmundry. However, natural provenances from Malaysia and Thailand generally showed superior growth, while the land-race populations often demonstrated superior stem straightness. Based on these results some aspects of a breeding strategy are outlined: (a) the establishment of three unrelated sublines; (b) an initial clonal test of all parents; and (c) wind-pollinated mating within clonal breeding orchards. 相似文献
62.
Summary In pearl millet hairy lamina, hairy sheath and hairy stem were inherited as monofactorial recessives while hairy leaf margin and hairy node were inherited as monogenic dominant traits. The gene for hairy lamina hl showed independent assortment from the gene for hairy node, Hn, and showed linkage with the genes hst (hairy stem), hs (hairy sheath) and Hm (hairy leaf margin). Furthermore, Hl was observed to have an epistatic effect on the expression of hs. The percentages of recombination between the gene pairs hl-hst, hl-hs and hl-Hm were 0.0, 8.30±0.44 and 19.81±0.98 respectively. Thus the genes hl-hst-hs Hm form one linkage group. 相似文献
63.
The Removal of Dye Colours from Aqueous Solutions by Adsorption on Low-cost Materials 总被引:2,自引:0,他引:2
The ability of five low cost adsorbents – rice husk, cotton, bark, hair and coal – to adsorb two basic dyes, namely, Safranine and Methylene Blue, has been studied. Equilibrium isotherms have been determined and analysed using the Langmuir equations. The monolayer saturation capacities for Safranine are 1119, 838, 875, 190 and 120 mg g-1adsorbent and for Methylene Blue are 914, 312, 277, 158 and 250 mg g-1adsorbent for bark, rice husk, cotton waste, hair and coal respectively. A limited number of fixed bed column studies have been performed and the bed depth service time for each dye-adsorbent system has been determined. 相似文献
64.
Avinash Talukdar Ashutosh Dharmendra Deo Narrotam Prasad Sahu Parimal Sardar Muhammad Aklakur Satya Prakash Nazeema Shamna Sarvendra Kumar 《Aquaculture Nutrition》2020,26(3):921-935
A 60 days feeding trial was conducted to illustrate the effect of graded levels of protein on the growth and metabolic enzymes of grey mullet (Mugil cephalus L.) fingerlings reared in inland saline water (ISW). Six isoenergetic (16 MJ/kg) and isolipidic (60 g/kg) diets containing 240, 260, 280, 300, 320 and 340 g crude protein (CP)/kg diet were formulated and fed to triplicate. Weight gain %, specific growth rate, protein utilizing efficiency, feed efficiency and RNA:DNA ratio were significantly higher (p < .05) in 320 and 300 g CP/kg diets. Fish fed with 240 g CP/kg diet showed significantly higher (p < .05) feed intake, whole‐body lipid content, hepatosomatic index value and liver glycogen content. Transaminase enzymes and malate dehydrogenase activities were elevated in fish fed 340 g CP/kg diet. Protease activity increased with increasing dietary CP level, but amylase activities showed an inverse relationship. No significant (p > .05) variations were observed for lactate dehydrogenase, oxidative stress enzymes, blood parameters and serum osmolality among all the treatment groups, but red blood cell count increases with increasing dietary CP levels. Based on the results, feeding dietary protein level of 300 g CP/kg is economically viable for rearing of grey mullet in ISW. 相似文献
65.
Chaitanya Prasad Nath Tapas Kumar Das Kuldeep Singh Rana Ranjan Bhattacharyya Sangeeta Paul Shashi Bala Singh 《国际虫害防治杂志》2018,64(4):303-314
In this experiment, weed management was studied in zero tillage (ZT) and conventional tillage (CT) wheat with and without crop residue and nitrogen (N). The treatment ZT with crop residue retention (R) and 75% of required N plus GreenSeeker? (GS)-aided N management (ZTRNGS) resulted in a reduction of density and dry weight of weeds compared to CT and ZT without residue. Sequential application of pendimethalin and sulfosulfuron (PMT-SSF) reduced the weed density and dry weight compared to the weedy check (WC). Importantly, the richness and diversity indices were high in ZTRNGS and in WC treatments. Greater wheat grain (5.11 t/ha) and biomass yield (13.31 t/ha) were observed in ZTRNGS than CT without residue and blanket split application of N (CTN). The treatment ZTRNGS recorded 14.1% and 16.9% higher gross and net returns, respectively, over CTN. This study demonstrates that surface retention of crop residue in ZT is more useful than residue incorporation under CT for effective weed control, improving crop yield and profitability. 相似文献
66.
Molecular breeding technologies and strategies for rust resistance in wheat (Triticum aestivum) for sustained food security
下载免费PDF全文
![点击此处可从《Plant pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Wheat is an important cereal food crop providing key nutrients to humankind. Rusts are the most destructive pathogens of cereal crops, with the exception of rice, across the world and resistant cultivars have been widely employed to reduce the yield losses caused by them. The modern intensive monoculture of cultivars and changing climatic conditions has created congenial conditions for the emergence of new virulent races such as Ug99, which is a great concern for world food security. Conventional breeding efforts have not been effective in quickly developing new varieties with durable and broad‐spectrum resistance against the rapidly evolving rust pathogen races. However, in the last two decades, biotechnological methods such as marker‐assisted selection (MAS) and transgenic technology have provided novel strategies for enhancing resistance levels and durability in crop plants in a short span of time. Nevertheless, broad application of transgenics in agriculture is hindered by biosafety apprehensions. In recent years, improved versions of biotechnological breeding methods such as genomic selection, genome editing technologies, cisgenesis and intragenesis, RNA‐dependent DNA methylation (RdDM), agroinfiltration and reverse breeding are gaining popularity. These technologies provide a tremendous capability to manipulate crop plants more precisely than before and accelerate crop improvement efforts for sustained food production as well as overcoming safety concerns associated with food crops. 相似文献
67.
68.
Rishi Kumar V. S. Nagrare Mukesh Nitharwal Dinesh Swami Y. G. Prasad 《Phytoparasitica》2014,42(3):311-316
The cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), an invasive pest species, has appeared on a large scale on cotton in India since 2006. Its distribution within the plant, and associated yield losses in cotton, were studied over 2 years. Distribution of P. solenopsis was observed within the cotton plant from vegetative to boll formation stage. In the vegetative and square formation stages, the highest mealybug population was recorded on the upper portion of the stem, followed by the middle leaves of the plant. In the boll formation stage, there was no significant difference in distribution of the insect among plant parts. Losses in cotton due to the mealybug varied between 14.9% at Grade 1 and 53.6% at Grade 4, on a 0 to 4 severity index, with a mean reduction of 35% and 32%, during 2008 and 2009, respectively. There was a significant relationship between severity of infestation and decrease in seed cotton yield. The information generated from this study will help in the early detection of mealybug infestation and estimation of yield losses corresponding to the severity grade of the damage. 相似文献
69.
Megha Kadam Salunkhe Shardul J. L. Bhagath Vinita Tiwari N. Prasad P. P. GOSWAMI 《Veterinary research communications》2009,33(7):597-610
Paratuberculosis or Johne’s disease is a chronic gastric disease of ruminants. For this disease there is no effective treatment
or preventive measure available. 16.8 kDa protein is an immunogenic protein of Mycobacterium avium paratuberculosis and can be an ideal candidate for developing a DNA vaccine construct. In present study a bicistronic DNA vaccine construct
pIR16.8/IFN was developed using eukaryotic vector pIRES 6.1. Two genes MPT (expressing 16.8 kDa protein) and murine IFNγ were
cloned, expressed and immunoreactivity was studied in murine model. Immunoreactivity was also compared with monocistronic
construct pIR16.8 expressing 16.8 kDa protein. Both pIR16.8 and pIR16.8/IFN showed eukaryotic expression of respective proteins
in BHK21 cells. The expressed proteins also showed immunoreactivity when reacted with hyperimmune sera raised against recombinant
16.8 kDa protein in western blot assay and immunofluorence assay. Both constructs were used as DNA vaccine in murine model
and immunogenecity was studied by DTH, lymphocyte proliferation assay and NO determination. DTH reaction was significantly
high in pIR16.8/IFN than pIR16.8 group, similarly lymphocyte proliferation and NO release was higher in pIR16.8/IFN group
than pIR16.8 group. This indicated T cell epitopic nature of 16.8 kDa protein. The study also showed that co-expression of
IFNγ with mycobacterial gene can enhance immunogenecity of DNA vaccine and can be used as immunoadjuvant. 相似文献
70.
Labile soil organic carbon,soil fertility,and crop productivity as influenced by manure and mineral fertilizers in the tropics 总被引:1,自引:0,他引:1
In recent years, organic agriculture has been receiving greater attention because of the various problems like deterioration in soil health and environmental quality under conventional chemical‐intensive agriculture. However, little information is available on the comparative study related to the impact of use of mineral fertilizers and organic manures on the soil quality and productivity. A long‐term field experiment was initiated in 2001 to monitor some of the important soil‐quality parameters and productivity under soybean–wheat crop rotation. The treatments consisted of 0, 30, and 45 kg N ha–1 for soybean and of 0, 120, and 180 kg N ha–1 for wheat. The entire amount of N was supplied to both the crops through urea and farmyard manure (FYM) alone or in combination at 1:1 ratio. Results indicated that Walkley‐and‐Black C (WBC; chromic acid–oxidizable) exhibited a marginal increase under only organic treatments as compared to control treatment (without fertilizers and manure) after completion of five cropping cycles. In case of labile‐C (KMnO4‐oxidizable) content in soil, relatively larger positive changes were recorded under organic, mixed inputs (integrated) and mineral fertilizers as compared to WBC. Maximum improvement in the values of C‐management index (CMI), a measure of soil quality was recorded under organic (348–362), followed by mixed inputs (268–322) and mineral fertilizers (198–199) as compared to the control treatment after completion of five cropping cycles. Similarly there was a substantial increase in KCl‐extractable N; in Olsen‐P; as well as in DTPA‐extractable Zn, Fe, and Mn under organic treatments. Although labile soil C positively contributed to the available N, P, K, Zn, Fe, and Mn contents in soil, it did not show any relationship with the grain yield of wheat. After completion of the sixth cropping cycle, organic treatments produced 23% and 39% lower grain yield of wheat as compared to that under urea‐treated plots. Relatively higher amount of mineral N in soil at critical growth stages and elevated N content in plant under mineral‐fertilizer treatments compared to FYM treatments were responsible for higher yield of wheat under mineral fertilizers. 相似文献