全文获取类型
收费全文 | 312篇 |
免费 | 18篇 |
专业分类
林业 | 18篇 |
农学 | 15篇 |
基础科学 | 3篇 |
73篇 | |
综合类 | 7篇 |
农作物 | 59篇 |
水产渔业 | 50篇 |
畜牧兽医 | 78篇 |
园艺 | 12篇 |
植物保护 | 15篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 19篇 |
2017年 | 27篇 |
2016年 | 20篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 36篇 |
2012年 | 21篇 |
2011年 | 30篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有330条查询结果,搜索用时 11 毫秒
301.
Morteza Yousefi Mehdi Paktinat Nemat Mahmoudi Amalia Pérez-Jiménez Seyyed Morteza Hoseini 《Fish physiology and biochemistry》2016,42(5):1417-1425
The aim of the present study was to investigate whether supplementary nucleotide “Optimun” mitigates the adverse effects of chronic overcrowding in Oncorhynchus mykiss. Two experimental diets [control and nucleotide-supplemented (0.2 %)] and two rearing densities (10 and 30 kg m?3) were combined to have four experimental treatments. The fish were reared for 45 days under different densities using different diets. At the end of the trial, FCR of the fish in higher density was significantly higher than those of the lower density. Nucleotide had no significant effects on growth performance and survival rate. Supplemented nucleotide significantly increased blood hematocrit, whereas it decreased serum total protein, total immunoglobulin (Ig) and creatinine. Overcrowding significantly increased serum glucose and total protein level and decreased serum lysozyme activity, but supplemented nucleotide produced no improvement in these items. No significant effect of overcrowding and dietary nucleotide was observed on serum cortisol. Supplemented nucleotide significantly increased serum urea under low stocking density. Overall, the results showed that 0.2 % “Optimun” had no positive effects on rainbow trout and also caused some immunological and metabolic problems. These findings are not in accordance with those obtained in the same species, with same nucleotide source and level, but acute stress; thus, further studies are encouraged on this topic. 相似文献
302.
Seyed Ali Johari Mohammad Reza Kalbassi Mehdi Soltani Il Je Yu 《Aquaculture International》2016,24(1):23-38
This study investigated the indirect use of silver nanoparticles (AgNPs) for reduction of fungal infections during incubation period of fertilized rainbow trout eggs. Different concentrations of nanosilver-coated zeolite (0.5, 1, and 1.5 % AgNPs) were compared with unmodified zeolite as water filter media in semi-recirculation systems. For testing the effect of AgNPs on reduction of fungal infection, fertilized eggs were transferred in incubators receiving water from filters coated with nanosilver. The eggs in each incubator were inoculated with Saprolegnia-infected trout eggs. Any dead or infected eggs and embryos were periodically removed, while the performance of the filters was assessed by calculating the survival rates from fertilization up to completion of the yolk–sac absorption stage. The results showed that the filters containing 0.5 % AgNPs increased the survival rate by 4.56 % from fertilization to the swim up stage compared to the control (p < 0.05). Also, the additional application of activated carbon (as absorbent media) along with AgNP-coated media in filters caused an increase of about 11.24 % in the survival rate for the larval stage (p < 0.05). In contrast to the control group with about 6 % fungal infection, no infections were observed during the incubation period in the incubators containing nanosilver-coated filters. Therefore, the final results confirmed that the indirect use of AgNPs in the aforementioned filters were significantly effective for preventing fungal infections in semi-recirculation systems for rainbow trout, making them a candidate for replacing the chemical fungicides currently used during egg incubation in hatchery systems. 相似文献
303.
Mehdi Vafakhah Amin Fakher Nikche Seyed Hamidreza Sadeghi 《Paddy and Water Environment》2018,16(3):411-424
The present study aims to evaluate performance of different infiltration models, namely initial and constant rate, soil conservation service (SCS) curve number and Green–Ampt in simulation of flood hydrographs for the small-sized Amameh Watershed, Iran. To achieve the study purpose, the infiltration rates were measured using rainfall simulator in work units acquired through overlaying topography, land use, drainage network and soil hydrologic group maps. All parameters of the study infiltration models were determined with the help of the Infilt. software package. The performances of the models in simulation of the observed output hydrographs from the entire watershed were ultimately evaluated for 28 rainfall–runoff events in the HEC-HMS environment. The different components of the observed and estimated hydrographs including time to peak, runoff volume, peak discharge, discharge values and peak time deviation were compared using relative error (RE), coefficient of determination (R2), peak-weighted root mean square error (PWRMSE) and Nash–Sutcliffe (NS) criteria. The general performance of estimations was also qualitatively assessed using scatter plot and distribution of study variables around standard lines of 1:1 slope. The results revealed that the SCS infiltration model with PWRMSE = 0.61 m3 s?1 and NS = 0.53 performed better than initial and constant rate model with PWRMSE = 1.1 m3 s?1 and NS = 0.54, and Green Ampt model with PWRMSE = 1.35 m3 s?1 and NS = 0.29 in estimation of flood hydrograph for the Amameh Watershed. 相似文献
304.
Hossein Mozafari Zahra Asrar Mohammad Mehdi Yaghoobi Hassan Salari Mohammad Mozafari 《Journal of plant nutrition》2016,39(5):628-642
This study was carried out to evaluation of some nutrients accumulation including Ni (nickel), Fe (iron), Mg (magnesium), Cu (copper), Ca (calcium) as well as Ni translocation factor (TF) in three tomato cultivars grown hydroponically under treatments including L-histidine (His) and calcium chloride (CaCl2) (300 µM) exposed to nickel (II) sulfate (NiSO4) (150 and 300 µM) by ICP-OES (inductively coupled plasma atomic emission spectroscopy) analysis. Tomato cultivars included Cal-J N3, Early Urbana Y and. Results indicated that shoot Ni accumulation increased under Ni stress. Ca and His reduced root, shoot Ni content and Ni TF (translocation factor) under Ni stress in Petoearly CH cultivar. Ni stress also decreased root and shoot Ca, Fe, Mg and Cu while Ca and His improved the nutrients uptake, and inhibited Ni accumulation. Therefore, Ca and His alleviated adverse effects of Ni stress on nutrients in Petoearly CH cultivar. Beside, Ca and His interaction alleviate Ni stress by inhibition of Ni uptake and translocation as well as plant nutrition improvement in the tomato plants. 相似文献
305.
Arshad Naji Alhasnawi Che Radziah Che Mohd Zain Ahsan A. Kadhimi Anizan Isahakb Azhar Mohamad Mehdi Farshad Ashraf Wan Mohtar Wan Yusoff 《Journal of Crop Science and Biotechnology》2016,19(5):353-362
Salt stress is considered to be the most important abiotic stress and is the main problem in the interruption of the metabolic processes of plants, thereby limiting crop production. The present study was carried out to examine the effects of exogenously applied mushroom polysaccharides (β-glucan) on the growth of two rice varieties of Oryza sativa L. (MRQ74 and MR269) seedlings grown in vitro in 200 Mm sodium chloride (NaCl). Growth characteristics, including shoot and root height, and fresh and dry weight of salt-stressed rice seedlings were inhibited by sodium chloride treatment, the degree of which depends on the rice variety. The negative effects of salinity stress resulted in an imbalance of N, K+ Na+ and Na/K ratios and biochemical analysis activities a degradation of chlorophyll content in the plants. However, treatment with exogenously applied polysaccharides (β-glucan) ameliorated the stress generated by NaCl and improved the parameters mentioned above. The significance of the changes in growth and metabolism to salt stress tolerance in rice seedlings are discussed in the paper. 相似文献
306.
APETx2 is a peptide isolated from the sea anemone Anthopleura elegantissima. It is the most potent and selective inhibitor of acid-sensing ion channel 3 (ASIC3) and it is currently in preclinical studies as a novel analgesic for the treatment of chronic inflammatory pain. As a peptide it faces many challenges in the drug development process, including the potential lack of stability often associated with therapeutic peptides. In this study we determined the susceptibility of wild-type APETx2 to trypsin and pepsin and tested the applicability of backbone cyclisation as a strategy to improve its resistance to enzymatic degradation. Cyclisation with either a six-, seven- or eight-residue linker vastly improved the protease resistance of APETx2 but substantially decreased its potency against ASIC3. This suggests that either the N- or C-terminus of APETx2 is involved in its interaction with the channel, which we confirmed by making N- and C-terminal truncations. Truncation of either terminus, but especially the N-terminus, has detrimental effects on the ability of APETx2 to inhibit ASIC3. The current work indicates that cyclisation is unlikely to be a suitable strategy for stabilising APETx2, unless linkers can be engineered that do not interfere with binding to ASIC3. 相似文献
307.
Seyyed Mehdi Hosseinifard Asieh Ahmadpour Bagher Mojazi Amiri Majid Razeghi Mansour Arezo Ebrahimpour 《Fish physiology and biochemistry》2013,39(6):1505-1511
The main indication of cimetidine is being H2-receptor antagonist, but studies suggest that cimetidine may also act as a non-specific stimulant of cell-mediated immunity and immunomodulator. In order to determine the immunomodulatory effect of dietary intake of cimetidine in the common carp (100 ± 10 g), subjects were fed diets containing 0 (control), 50, 100 and 200 mg cimetidine kg?1 of dry diet for a period of 6 weeks. TLC and NBT assays were significantly (P < 0.05) stimulated in cimetidine-supplemented groups displaying the highest value in 200 mg kg?1 group. A decrease (P < 0.05) in cortisol and ACH50 value was recorded in fish treated with cimetidine. Serum protein, albumin and serum globulin levels were not significantly changed. The findings of the present investigation suggest that the incorporation of cimetidine in the diet of common carp enhances the non-specific immunity. 相似文献
308.
Maryam Akbari Hessam Jafari Mojtaba Rostami Gholam Reza Mahdavinia Ali Sobhani nasab Dmitry Tsurkan Iaroslav Petrenko Mohammad Reza Ganjali Mehdi Rahimi-Nasrabadi Hermann Ehrlich 《Marine drugs》2021,19(9)
The renewable, proteinaceous, marine biopolymer spongin is yet the focus of modern research. The preparation of a magnetic three-dimensional (3D) spongin scaffold with nano-sized Fe3O4 cores is reported here for the first time. The formation of this magnetic spongin–Fe3O4 composite was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA) (TGA-DTA), vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FTIR), and zeta potential analyses. Field emission scanning electron microscopy (FE-SEM) confirmed the formation of well-dispersed spherical nanoparticles tightly bound to the spongin scaffold. The magnetic spongin–Fe3O4 composite showed significant removal efficiency for two cationic dyes (i.e., crystal violet (CV) and methylene blue (MB)). Adsorption experiments revealed that the prepared material is a fast, high-capacity (77 mg/g), yet selective adsorbent for MB. This behavior was attributed to the creation of strong electrostatic interactions between the spongin–Fe3O4 and MB or CV, which was reflected by adsorption mechanism evaluations. The adsorption of MB and CV was found to be a function of pH, with maximum removal performance being observed over a wide pH range (pH = 5.5–11). In this work, we combined Fe3O4 nanoparticles and spongin scaffold properties into one unique composite, named magnetic spongin scaffold, in our attempt to create a sustainable absorbent for organic wastewater treatment. The appropriative mechanism of adsorption of the cationic dyes on a magnetic 3D spongin scaffold is proposed. Removal of organic dyes and other contaminants is essential to ensure healthy water and prevent various diseases. On the other hand, in many cases, dyes are used as models to demonstrate the adsorption properties of nanostructures. Due to the good absorption properties of magnetic spongin, it can be proposed as a green and uncomplicated adsorbent for the removal of different organic contaminants and, furthermore, as a carrier in drug delivery applications. 相似文献
309.
Hygroscopic thickness swelling rate of composites from sawdust and recycled plastics 总被引:1,自引:1,他引:0
Saeed Kazemi Najafi Azadeh Kiaeifar Mehdi Tajvidi Elham Hamidinia 《Wood Science and Technology》2008,42(2):161-168
The thickness swelling rates of compression molded wood plastic composites (WPCs) prepared from 50% by weight sawdust and
50% by weight virgin and/or recycled plastics (HDPE and PP) were studied. Thickness swelling rates of the manufactured WPCs
were evaluated by immersing them in water at room temperature and monitoring thickness changes for several weeks. A swelling
model developed by Shi and Gardner (Composites Part A, 37:1276–1285, 2006) was used to study the thickness swelling process
of WPCs. The parameter K
SR of the model can be used to quantify the swelling rate. The results indicated that composites containing PP had lower equilibrium
thickness swelling and also shorter equilibrium time (time to reach equilibrium thickness swelling). The swelling model developed
was a good predictor of the hygroscopic swelling process of wood plastic composites. Composites containing PP (virgin and
recycled) had higher K
SR than those containing HDPE. The minimum and maximum K
SR values were observed in composites made of virgin HDPE and a mixture of recycled plastics, respectively. With increasing
recycled plastic content K
SR linearly decreased. 相似文献
310.
Emadi M Baghernejad M Emadi M Maftoun M 《Pakistan journal of biological sciences: PJBS》2008,11(2):238-243
Spatial patterns for several soil parameters such soil texture, Exchangeable Sodium Percentage (ESP), Electrical Conductivity (ECe), soil pH, Cation Exchange Capacity (CEC) were examined in saline and sodic soils in Arsanjan plain, Southern Iran, in order to identify their spatial distribution for implementation of a site-specific management. Soil samples were collected from 0-30, 30-60 and 60-90 cm soil depths at 85 sampling sites. Data were analyzed both statistically and geostatistically on the basis of the semivariogram. The spatial distribution model and spatial dependence level varied between soil parameters. Soil pH and ESP had the minimum and maximum variability at all depths, respectively. Soil properties indicated moderate to strong spatial dependence. ECe exhibited moderate spatial dependence at three depths; pH and ESP had a moderate spatial dependence at 0-30 cm and strong spatial dependence at 30-60 and 60-90 cm depths. Clay and CEC exhibited strong spatial dependence for the 0-30 cm and weak spatial dependence at 30-60 and 60-90 cm depths. Sand and silt had a non-spatial dependence at 0-30 cm and weak spatial dependency at 30-60 and 60-90 cm depths. The spatial variability in small distances of ECe, CEC, pH and ESP generally increased with depth. All geostatistical range values were greater than 1168 m. The results reported herein indicated that the strong spatial dependency of soil properties would lead to the extrinsic factors such as ground water level and drainage. It is important to know the spatial dependence of soil parameters, as management parameters with strong spatial dependence will be more readily managed and an accurate site-specific scheme for precision farming more easily developed. 相似文献