全文获取类型
收费全文 | 1078篇 |
免费 | 64篇 |
国内免费 | 9篇 |
专业分类
林业 | 67篇 |
农学 | 72篇 |
基础科学 | 27篇 |
410篇 | |
综合类 | 102篇 |
农作物 | 96篇 |
水产渔业 | 62篇 |
畜牧兽医 | 185篇 |
园艺 | 28篇 |
植物保护 | 102篇 |
出版年
2023年 | 16篇 |
2022年 | 44篇 |
2021年 | 72篇 |
2020年 | 70篇 |
2019年 | 92篇 |
2018年 | 115篇 |
2017年 | 105篇 |
2016年 | 78篇 |
2015年 | 38篇 |
2014年 | 45篇 |
2013年 | 130篇 |
2012年 | 56篇 |
2011年 | 70篇 |
2010年 | 40篇 |
2009年 | 25篇 |
2008年 | 36篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有1151条查询结果,搜索用时 140 毫秒
991.
自1989 年发现了菊花对农杆菌浸染的敏感性,农杆菌介导转化法已成功应用于菊花花色、花期、株形、抗病虫及耐非生物胁迫等性状的改良中。从影响菊花遗传转化效率的农杆菌菌株类型、外植体选用、辅助添加剂的使用以及抗生素筛选等几方面阐述了菊花遗传转化技术研究的进展和应用现状,对菊花分子育种性状改良和重要功能基因发掘等研究进展进行综述,并对菊花转化效率改善途径的探索和环境友好型转基因新技术研发前景提出展望,以期为菊花分子育种提供参考。 相似文献
992.
Muhammad Tahir Khan Nazir Ahmad Khan Melkamu Bezabih Muhammad Subhan Qureshi Altafur Rahman 《Tropical animal health and production》2013,45(3):849-853
The aim of this study was to evaluate the nutritional and feeding value of peanut hay (Arachis hypogaea L.) produced under tropical environment as an alternate forage resource for sheep. Peanut hay was appreciably high in crude protein [CP; 105 g/kg dry matter (DM)] and lower in neutral detergent fiber (NDF; 466 g/kg DM). Moreover, peanut hay was rich in Ca (12 g/kg DM) and P (1.7 g/kg DM). A feeding trial was conducted to investigate the effect of substituting wheat straw with peanut hay on nutrient intake, digestibility, and N utilization. Four adult Ramghani (Kaghani × Rambouillet) wethers (60?±?2.5 kg body weight) were randomly assigned to the four dietary treatments according to a 4?×?4 Latin square design. The four rations were formulated on isonitrogenous and isocaloric bases and differed in the proportion (in grams per kilogram DM) of wheat straw/peanut hay, i.e., 700:0, 460:240, 240:460, and 0:700. The replacement of wheat straw with peanut hay increased the intakes of DM (P?<?0.001), NDF (P?<?0.01), and N (P?<?0.001). Moreover, apparent in vivo digestibility of DM, NDF, and CP increased (P?<?0.001) with the increasing proportion of peanut hay in the ration. Nitrogen retention in the body increased (P?<?0.01; 3.2 to 8.1 g/day) with the replacement of wheat straw with peanut hay. These findings showed that substitution of wheat straw with peanut hay can improve DM and nutrients intake, digestibility, and N retention in sheep. 相似文献
993.
Bin Li Chang-Lin Shan Qing Zhou Yuan Fang Yang-Li Wang Fei Xu Li-Rong Han Muhammad Ibrahim Long-Biao Guo Guan-Lin Xie Guo-Chang Sun 《Marine drugs》2013,11(5):1534-1552
This present study deals with synthesis, characterization and antibacterial activity of cross-linked chitosan-glutaraldehyde. Results from this study indicated that cross-linked chitosan-glutaraldehyde markedly inhibited the growth of antibiotic-resistant Burkholderia cepacia complex regardless of bacterial species and incubation time while bacterial growth was unaffected by solid chitosan. Furthermore, high temperature treated cross-linked chitosan-glutaraldehyde showed strong antibacterial activity against the selected strain 0901 although the inhibitory effects varied with different temperatures. In addition, physical-chemical and structural characterization revealed that the cross-linking of chitosan with glutaraldehyde resulted in a rougher surface morphology, a characteristic Fourier transform infrared (FTIR) band at 1559 cm−1, a specific X-ray diffraction peak centered at 2θ = 15°, a lower contents of carbon, hydrogen and nitrogen, and a higher stability of glucose units compared to chitosan based on scanning electron microscopic observation, FTIR spectra, X-ray diffraction pattern, as well as elemental and thermo gravimetric analysis. Overall, this study indicated that cross-linked chitosan-glutaraldehyde is promising to be developed as a new antibacterial drug. 相似文献
994.
Muhammad Nadeem Asghar Muhammad Kaleem Ullah Muhammad Mohsin Hafeez 《Irrigation and Drainage Systems》2008,22(3-4):239-252
Stream salinity management is of prime importance for ensuring environmental sustainability of rivers, streams, lakes and other water bodies. Saline groundwater inflows are the main cause of deteriorating quality of stream flows; especially during periods of low flows. The Murray-Darling Basin is a good example for reducing groundwater recharge from irrigated agricultural areas with successful implementation of land and water management plans (LWMPs). In most cases, these plans help minimize the influence of saline groundwater flows on the stream salinity, as a preventive measure. As a remedial measure, this paper introduces a simple but an innovative approach for regulating saline groundwater inflows to natural streams in irrigated agricultural areas. The approach uses the flap gate with an automatic lowering and raising mechanism. During low stream flow, this gate is kept in a raised position. Depending upon the upstream inflows, the ponding situation will develop hydraulic gradient away from the stream; groundwater inflows to the creek will become minimal. During high stream flows, the gate is kept in a lower position to let the diluted water flows through the stream uninterrupted. To install, operate and manage such gates on multiple sites along the stream(s), the individual control panels can be joined into a central control station via telemetric link up. This approach, which holds a key for successfully regulating groundwater induced salinity to natural streams, should be considered in conjunction with other LWMPs to improve stream salinity in an irrigated agricultural area. 相似文献
995.
Dietary forage concentration and particle size affect sorting,feeding behaviour,intake and growth of Chinese holstein male calves 下载免费PDF全文
A. U. R. Muhammad C. Q. Xia B. H. Cao 《Journal of animal physiology and animal nutrition》2016,100(2):217-223
The objective of study was to evaluate the effect of forage concentration (F:C) and forage particle length (FPL) on sorting, feeding behaviour, intake, growth and body measurements of growing calves. Twenty‐eight weaned calves of body weight 156.79 ± 33.44 (mean ± SD) were used in 2 × 2 factorial arrangements with the factors FPL of hay grass (full and short) and hay grass concentrations (low, 50% and high, 65%). The treatments were as follows: full length (FL) with low F:C (50:50), FL with high F:C(65:35), short length (SL) with low F:C (50:50) and SL with high F:C (65:35). Increasing F:C and decreasing FPL enhanced sorting for short and fine particle and sorting against long particle (p < 0.05). Dry matter intake (DMI) was decreased by decreasing the FPL (p < 0.05). Increasing F:C (65:35) increased the DMI (p < 0.05). A positive interaction between FPL and F:C was found for (daily weight gain) DWG, weight gain (WG) and feed conversation ratio (FCR) (p < 0.05). In case of feeding behaviour, interaction for eating time and eating time per kilogram DM was present. Increasing the F:C increased the eating time in both FL and SL (p < 0.05). Chopping of hay had decreased the chewing time (p < 0.05). Increasing F:C increased chewing time per kilogram DMI. High F:C decreased the lying time (p < 0.05) in FL and SL treatments (p < 0.05). Increasing F:C reduced the overall abnormal behaviour (p < 0.05). These results suggested that animals performed better at higher F:C at SL diet. Intensity of sorting for short and fine particle and against long particle increased at higher F:C and SL diets. Eating time and eating time per kilogram DMI increased by increasing F:C level in both FL and SL treatments. Chewing time increased by increasing the FPL, while increasing the F:C enhanced the chewing time per kilogram DMI and reduced animal's abnormal behaviour. 相似文献
996.
997.
Muhammad A. I. Dalia A. M. Loh T. C. Akit H. Samsudin Anjas A. 《Veterinary research communications》2022,46(2):431-445
Veterinary Research Communications - This study compares the effects of sodium selenite, selenium yeast, and enriched bacterial organic selenium protein on antioxidant enzyme activity, serum... 相似文献
998.
Khurshaid Khan Nazma Habib Khan Farhat Anwar Ihtisham Ullah Noor Badshah Irfan Irfan Khalid Iqbal Ibrar Shah Shah Tariq Aziz Muhammad Shahid Naseem Khan Safeer Ullah Shah 《Zoonoses and public health》2022,69(1):33-45
Present study was carried to determine the sand fly species composition, breeding sites ecology, seasonal abundance, and spatial distribution in district Malakand, Khyber Pakhtunkhwa, Pakistan. In addition, risk factors associated with cutaneous leishmaniasis (CL) were also evaluated. Survey of indoor and outdoor habitats was carried out using sticky traps in 31 villages of Dargai and Batkhela tehsils of Malakand. Soil from habitats of adult and immature sand flies was analysed. Questionnaire-based household survey was also performed in these villages to assess risk factors associated with CL. Soil samples from selected CL positive households were analysed for its contents. Additionally, clinicoepidemiological data from local health centres was examined for the year 2019. Total of 3,140 sand flies belonging to 18 species were collected. Phlebotomus sergenti was the most abundant species (38.16%). Its abundance had a strong positive correlation with mean monthly relative humidity and negative correlation with average temperature. Phlebotomus sergenti and Phlebotomus papatasi were abundant at an elevation ranging from 320 to 1,120 m above sea level and in agricultural lands near human settlements. Flight height preference apparatus collected maximum sand flies at 30 cm (1ft) above the ground and all species associated negatively with height. Soil analysis from habitats of adult and immature flies showed that highest mean number of adults and immatures were recorded from silt loam which carried highest concentrations of K2O, Mg, Ca, and Zn. Number of immature sand flies correlated moderately (r = .7, p < .05) with K2O soil concentrations. There was significant similarity between organic matter contents in soil samples from positive breeding sites and CL households (Wilcoxon rank-sum test, p = .1976). In multivariate analysis model for CL risk factors, age (26–35 and >35 years), knowledge of leishmaniasis, living in a middle and upper class, preachers visit to villages, and assumption that Afghan refugees are more prone to CL were significant. CL patient's archived data from health centres showed that majority of patients had lesions on face and hands. Patient's influx was highest in February and March. 相似文献
999.
Farm Level Tree Planting in Pakistan: The Role of Farmers’ Perceptions and Attitudes 总被引:1,自引:0,他引:1
The low proportion of forested land and continuing degradation of existing forest cover are serious threats to the sustainability
of forestry in Pakistan. Farm forestry has been identified as a feasible solution, particularly in the plain areas. Applying
the Theory of Planned Behaviour in a survey of 124 farmers in Dera Ismail Khan district of Pakistan’s North West Frontier
Province showed that farmers’ willingness to grow trees on their farms is a function of their attitudes towards the advantages
and disadvantages of growing trees, their perception of the opinions of salient referents and factors that encourage and discourage
farm level tree planting. Farmers viewed farm forestry as economically beneficial and environmentally friendly. Tree planting
was perceived as increasing income, providing wood for fuel and furniture, controlling erosion and pollution and providing
shade for humans and animals. Farmers saw hindrance in agricultural operations and the harbouring of insects, pests and diseases
as negative impacts of tree planting; however, these were outweighed by their perceptions of positive impacts. Tree growing
decisions of farmers were influenced by the opinions of family members, owners/tenants, fellow farmers and village elders.
The factors that significantly predicted farm level tree planting were availability of barren land, lack of markets, lack
of nurseries and damage caused by animals and humans. Farm forestry programmes are more likely to be successful if they acknowledge
and address the factors which underlie farmers’ reasons for planting or not planting trees. 相似文献
1000.
Asma Hassan Shahzada Sohail Ijaz Rattan Lal Safdar Ali Qaiser Hussain Muhammad Ansar Romaan Hayat Khattak Muhammad Sharif Baloch 《Land Degradation \u0026amp; Development》2016,27(4):1175-1185
Depth distribution of soil organic carbon (SOC) fractions depends on the efficiency of agro‐technical managements. Information on depth distribution of SOC fractions mostly confined to the plow layer and scant in dry lands of Punjab, Pakistan. Therefore, a field experiment was laid out with moldboard plow (MP) (control), tine cultivator (TC), and minimum tillage (MT) as main plots, and cropping sequences fallow wheat (Triticum aestivum L.), (FW, control), mungbean (Vigna radiata L.) wheat (MW), sorghum (Sorghum bicolor L.) wheat (SW), green manure wheat (GW), and mungbean‐chickpea (MC) (Cicer arietinum L.) as sub‐plots. Treatment effects were assessed for microbial biomass carbon (MBC), potentially mineralizeable carbon (PMC), particulate organic carbon (POC), dissolved organic carbon (DOC), HCl insoluble carbon (HIC), and stratification ratio (SR) in Rawal series: Udic Haplustalf. Alfisols. The MBC concentration was the highest in MT system, at 15 to 30‐cm depth under MW and PMC concentration was highest under SW with MT at 45–60 cm. MP had higher POC in FW sequence. The highest DOC was at 0 to 15‐cm depth under MC with TC and stock of HIC was more under TC with FW sequence. The highest SR of PMC was under MT with FW at 0–15:15–30 and POC was under TC and MP with FW at depths of 0–15:45–60 cm. The highest SR for DOC was under MP with GW at 0–15:45–60 cm and HCl insoluble C was under MT with SW at 0–15:45–60. In broad‐spectrum, labile organic fractions revealed differential sensitivity, and POC stocks are also a sensitive indicator to detect the short‐management effects. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献