全文获取类型
收费全文 | 341篇 |
免费 | 17篇 |
专业分类
林业 | 32篇 |
农学 | 27篇 |
基础科学 | 5篇 |
99篇 | |
综合类 | 19篇 |
农作物 | 51篇 |
水产渔业 | 40篇 |
畜牧兽医 | 51篇 |
园艺 | 6篇 |
植物保护 | 28篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 14篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 22篇 |
2016年 | 25篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 39篇 |
2012年 | 23篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 25篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有358条查询结果,搜索用时 250 毫秒
171.
Ali Ghadami Firouzabadi Mahmoud Raeini-Sarjaz Ali Shahnazari Hamid Zareabyaneh 《Archives of Agronomy and Soil Science》2013,59(10):1357-1367
Leaf area (LA) is a valuable parameter in many agronomic and plant physiological studies. Its measurement is time consuming and involves leaf destruction. Therefore, there is a tendency in using simple, fast, non-destructive, and electronic devices methods to estimate LA. The aim of this study was to estimate LA across different water regime treatments using a combination of leaf mass and leaf dimensions of sunflower (Helianthus annuus L.). For this purpose, different leaf sizes were collected from plants during the growing season on different time intervals. Experiment was conducted during 2012 summer time in Sari Agriculture Sciences and Natural Resources University, Iran. On field leaf dimension measurements were carried out, and leaves sketches were put on paper, scanned and then areas were measured using AutoCAD software. Multivariate linear and non-linear regression models were constructed between LA and other leaf components measured. All constructed models provided highly significant correlations (r = 0.90–0.99) between LA and different leaf components. The exponential model [LA = 0.619 [(L × W)0.5]2.019] provided the best estimation of sunflower LA (R2 = 0.993). In conclusion, the simple and quick models developed in this study could predict the sunflower LA and leaf area index (LAI) with high precision. 相似文献
172.
Hamid I. Tak Olubukola O. Babalola Maria H. Huyser Arif Inam 《Soil Science and Plant Nutrition》2013,59(2):156-167
The deficiency of potassium (K) has resulted in decreasing the yield and quality of food grains. Moreover, with decreasing water resources the use of wastewater in agriculture as an alternative source of water and nutrients is being debated. This study was therefore undertaken to test wastewater for its suitability as irrigation water together with uniform basal doses of nitrogen (N) and phosphorus (P) and varying doses of potassium (K0, K20, K40 and K60). It was observed that the plants receiving wastewater as a source of irrigation water performed better with a lower K dose. Potassium at 20?kg?ha?1 along with wastewater resulted in better growth, photosynthetic rate (P N), stomatal conductance (g s) and yield of the chickpea (Cicer arietinum L.). Thus fertilizer rates could be lowered with the use of wastewater which can serve not only as the source of water but of nutrients also. However, regular monitoring of wastewater and soil for any buildup of heavy metal is necessary. The physical and chemical parameters of wastewater were also tested and most of them were found to be well within the permissible limits as set by the Food and Agriculture Organization (FAO). 相似文献
173.
Azadeh Hatef Hamid Niksirat Bagher Mojazi Amiri Sayed Mohammad Hadi Alavi & Mahmoud Karami 《Aquaculture Research》2007,38(11):1175-1181
Sperm density, mineral and organic composition of the seminal plasma and their physiological relationship were investigated in the Caspian brown trout (Salmo trutta caspius). To establish a rapid and accurate method for assessment of sperm density, three different techniques were used: sperm counting, spectrophotometry (at 480 nm) and determination of the spermatocrit. The seminal plasma contained 159.26±8.84 mM sodium (Na), 33.72±2.01 mM potassium (K), 133.04±5.96 mM chlorine (Cl), 1.68±0.2 mM calcium (Ca) and 0.988±0.13 mM magnesium (Mg). The following organic components were found: total protein 0.75±0.14 mg 100 mL−1, cholesterol 2.86±0.58 mg L−1 and glucose 3.81±1.04 mM L−1. The mean sperm density was estimated to be 3.3 × 109 spermatozoa mL−1. The spermatocrit (%) ranged from 25 to 52 in sperm samples. Highly significant linear relationships were found between sperm density and spermatocrit (R2=0.703, P<0.001) and sperm density and optical density (R2=0.909, P<0.001), indicating that optical density can be used as a quick and accurate method of estimating sperm density. Significant relationships were also found between sperm density and Ca, Mg and total protein of seminal plasma. A significant correlation was also observed between the Ca and Mg concentrations (R2=0.774, P<0.01). The following correlations were observed between mineral and organic components: total protein and Ca (R2=0.462, P<0.05), total protein and Mg (R2=0.518, P<0.05) and glucose and Cl (R2=0.374, P<0.05). These parameters should be considered when developing procedures for either artificial fertilization or for cryopreservation of sperm. 相似文献
174.
Nargis Begum Tajammal Hussain Bilquis Afridi A. Hamid 《Plant foods for human nutrition (Dordrecht, Netherlands)》1991,41(4):329-336
A supplementary food mix was prepared from roasted peanut, chickpea and sugar. The effect of this food mix on birth weight was tested on a group of rural women of low socioeconomic group in few villages in Peshawar District of NWFP. A 100 g supplementary food mix providing 16.7 g protein and 520 K. Cal of energy was given daily to a group of mothers in their third trimester, until the time of delivery. Another group of pregnant women acted as control. The results indicated a high maternal weight gain in the supplemented group. Moreover the birth weight, length, head and chest circumference of the new born in the supplemented group was also significantly higher as compared to control group. 相似文献
175.
Mohammad Reza Kandehkar Ghahraman Hossein Hosseini-Nave Omid Azizi Mohammad Reza Shakibaie Hamid Reza Mollaie Samane Shakibaie 《Iranian Biomedical Journal》2021,25(3):193
Background:There is limited information on the 3D prediction and modeling of the colistin resistance-associated proteins PmrA/B TCS in Acinetobacter baumannii. We aimed to evaluate the stereochemical structure and domain characterization of PmrA/B in an A. baumannii isolate resistant to high-level colistin, using bioinformatics tools. Methods:The species of the isolate and its susceptibility to colistin were confirmed by PCR-sequencing and MIC assay, respectively. For 3D prediction of the PmrA/B, we used 16 template models with the highest quality (e-value <1 × 10−50). Results:Prediction of the PmrA structure revealed a monomeric non-redundant protein consisting of 28 α-helices and 22 β-sheets. The PmrA DNA-binding motif displayed three antiparallel α-helices, followed by three β-sheets, and was bond to the major groove of DNA by intermolecular van der Waals bonds through amino acids Lys, Asp, His, and Arg, respectively. Superimposition of the deduced PmrA 3D structure with the closely related PmrA protein model (GenBank no. ) revealed no distortion in conformation, due to Glu→Lys substitution at position 218. Similarly, the PmrB protein structure displayed 24 α-helices and 13 β-sheets. In our case, His251 acted as a phosphate receptor in the HisKA domain. The amino acid substitutions were mainly observed at the putative N-terminus region of the protein. Furthermore, two substitutions (Lys21→Ser and Ser28→Arg) in the transmembrane domain were detected. Conclusion: TheDNA-binding motif of PmrA is highly conserved, though the N-terminal fragment of PmrB showed a high rate of base substitutions. This research provides valuable insights into the mechanism of colistin resistance in A. baumannii. Key Words: WP_071210493.1Acinetobacter baumannii, Amino acid substitution, Colistin, Mutation 相似文献
176.
Hamid Najafipour Ali Siahposht Khachaki Mohammad Khaksari Beydolah Shahouzehi Siyavash Joukar Hamid Reza Poursalehi 《Iranian Biomedical Journal》2014,18(4):225-231
Background: Accidents are the second reason for mortality and morbidity in Iran. Among them, brain injuries are the most important damage. Clarification of the effects of brain injuries on different body systems will help physicians to prioritize their treatment strategies. In this study, the effect of pure brain trauma on the cardiovascular system and lungs 24 hours post trauma was assessed. Methods: Male Wistar rats (n = 32) were divided into sham control and traumatic brain injury (TBI) groups. In TBI animals, under deep anesthesia, a blow to the head was induced by the fall of a 450 g weight from 2 m height. Twenty four hours later, heart electrocardiogram and functional indices, cardiac troponin I, IL-6, TNF-, IL-Iβ in tissue and serum, and the histopathology of heart and lung were assessed. Results: The results showed that none of the functional, biochemical, inflammatory, and histopathology indices was statistically different between the two groups at 24 hours post TBI. Indices of impulse conduction velocity in atrium (P wave duration and P-R interval) were significantly longer in the TBI group. Conclusion: Overall, no important functional and histopathologic disturbances were found in heart and lung of TBI group after 24 hours. If the data is reproduced in human studies, the medical team could allocate their priority to treatment of brain disorders of the victim in the first 24 hours of pure TBI and postpone extensive assessment of heart and lung health indices to later time, thus reducing patient and health system expenditures. Key Words: Brain injury (TBI), Cardiopulmonary, Myocardial contraction, Cytokines 相似文献
177.
Hamid Reza Naji Mohd. Hamami Sahri Tadashi Nobuchi Edi Suhaimi Bakar 《Journal of Wood Science》2013,59(6):460-468
Wood characteristics vary from pith to bark and this can influence the final use. These variations can be related to the effects of plantation management. The radial variation in fiber cells, vessel elements, and ray cells was investigated for a commercial and fast-grown species, the rubberwood (Hevea brasiliensis), at varying stocking densities. Nine-year-old trees of two new clones (RRIM 2020 and RRIM 2025) were categorized into four stocking densities of 500, 1000, 1500, and 2000 trees ha?1. The sample blocks were anatomically analyzed to determine the changes in wood cells from pith to bark. The results generally showed a centrifugal increase in fiber features, vessel diameter, ray height, and ray area. Vessel density and ray density showed a decreasing trend. Vessel areas revealed a radial irregular variation. The ray area showed a striking relationship with ray density and ray height. Ray cell pattern indicated enough variation for visual approval to ensure within and between stocking density changes. Most radial variation was explained by the effect of cambial age. Owing to different stem width and growth rates, the mean cell features were not at the same radial distances from the pith. 相似文献
178.
Modeling and Analysis of Mechanization Projects of Wheat Production by GERT Networks 总被引:1,自引:0,他引:1
Reza Abdi Hamid Reza Ghasemzadeh Shamsollah Abdollahpour Majid Sabzeparvar Adel Dabbag Mohamadi Nasab 《中国农业科学(英文版)》2010,9(7):1078-1083
In crop production systems,all operations such as seed bed preparation,etc.,must be accomplished on time,if yield reduction and low quality product are to be avoided.Therefore all operations in mechanized cropping projects require precise scheduling,planning and management.The basic approach in all scheduling techniques is to form a network of activities and events relationships that graphically portrays the sequential relations between the tasks in a project.Such a network would as a powerful tool available a farm manager to plan,schedule,monitor and control a project.Since GERT(Graphical Evaluation and Review Technique) networks have most of advantages associated with networks and available system analyst in exact evaluation of certain types of networks,in this research it was used and mechanized wheat production system was simulated,modeled and analyzed.Critical activities,events and path were determined.Results showed that the network model was able to answer any statistic questions concerning with the project.Network models,particularly GERT networks are increasingly powerful tool for modeling,scheduling,planning,controlling,and analyzing of agricultural mechanization projects. 相似文献
179.
180.
Gill histopathological characteristics of Caspian roach (Rutilus rutilus caspicus) fingerlings treated with potassium permanganate and formalin
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Melika Ghelichpour Hamid Rajabiesterabadi Seyyed Morteza Hoseini 《Aquaculture Research》2016,47(1):276-282
The aim of this study was to determine the gill histopathological characteristics of Caspian roach (Rutilus rutilus caspicus) fingerlings exposed to different concentrations of potassium permanganate (PM) and formalin (FO). The fish were exposed to different PM and FO concentrations over different periods: 1 ppm PM for 24 h (1‐P24), 2 ppm PM for 24 h (2‐P24), 5 ppm PM for 0.5 h (5‐P0.5), 10 ppm PM for 0.5 h (10‐P0.5), 10 ppm FO for 24 h (10‐F24), 20 ppm FO for 24 h (20‐F24), 40 ppm FO for 0.5 h (40‐F0.5) and 80 ppm FO for 0.5 h (80‐F0.5). After exposure, gill samples were collected for histological examination. The most frequent gill histopathological symptoms were hyperplasia and epithelial lifting. The order of the gill injury index (Ig.i) among the treatments was as follow: 1‐P24, 2‐P24 < 5‐P0.5, 40‐F0.5 < 10‐F24 < 10‐P0.5, 20‐F24, 80‐F0.5. Comparing the two agents, it is concluded that there is no significant difference in the gill damages between the agents during the short‐bath treatments. However, PM causes less pathological symptoms than FO during the long‐bath treatments. Comparing the bath durations, the agents showed different behaviours. PM‐treated fish showed significantly lower gill damage during the long‐bath compared to the short‐bath treatment; whereas, pathological symptoms of FO‐treated fish was dose‐dependent for each exposure period, separately. Overall, exposure of Caspian roach to PM, at the concentrations recommended for long bath, resulted in milder gill damages compared to FO. 相似文献