首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   44篇
  免费   4篇
林业   3篇
农学   1篇
  8篇
农作物   7篇
水产渔业   19篇
畜牧兽医   6篇
园艺   1篇
植物保护   3篇
  2022年   1篇
  2021年   3篇
  2020年   3篇
  2019年   4篇
  2018年   4篇
  2017年   6篇
  2016年   3篇
  2015年   6篇
  2014年   4篇
  2013年   2篇
  2012年   1篇
  2011年   2篇
  2010年   3篇
  2008年   3篇
  2005年   1篇
  2004年   2篇
排序方式: 共有48条查询结果,搜索用时 31 毫秒
11.
Property rights, the agricultural price index, forest area, population, income and timber price are important factors in the deforestation process. The aim of this study was to test the impact of these factors on deforestation in Iran using an environmental Kuznets curve (EKC). The autoregressive distributed lag approach was also used to estimate the deforestation function. The existence of an inverted U-shaped EKC for deforestation in Iran was confirmed. In addition, there is evidence of a relationship between deforestation and property rights, forest area, agricultural price index and terms of trade. It is concluded that improvement of secure property rights and environmental policies can improve compliance regarding forest land use and reduce the deforestation rate in Iran.  相似文献   
12.
The effect of time‐dependent protein restriction (PR) and refeeding were investigated on growth, body composition, fatty acids (FA), amino acids (AA) and nonspecific immune functions in the juvenile Siberian sturgeon (Acipenser baeri; 75 ± 5 g). Test diets included: T1 (control) and T2 fish fed diets containing 400 and 300 g/kg protein respectively during the whole experimental period, T3 (every other day) and T4 (every other week) fish were fed diets containing 300 g/kg protein (PR) and refeeding with diet containing 400 g/kg protein respectively, and T5 fish fed a diet containing 300 g/kg protein for 3 weeks and a diet containing 400 g/kg protein for 5 weeks, were fed to the fish for 56 days by visual satiation. Unlike ration T2 and T5, feeding treatments of T3 and T4 showed an increase in fish growth and body composition (p < 0.05) and they were very close to the control group (> 0.05). Regarding the fatty acid profile, although the percentage of highly unsaturated fatty acids (HUFA) and polyunsaturated fatty acids (PUFA) declined significantly in the T2 and T5 groups, the saturated fatty acid (SFA) and monounsaturated fatty acids (MUFA) indicated no change among the treatments. In addition, the T2 and T5 groups demonstrated a reduction in essential amino acids (EAA) with a simultaneous increase in nonessential amino acids (NEAAs), which was significant from that of controls and other groups (< 0.05). In terms of nonspecific immune parameters (serum lysozyme activity and alternate complement activity [ACH50]), treatment 3 has an appropriate result that did not have a significant difference with the control group (p > 0.05), but there was significant difference with other groups (p < 0.05). As a result, the T3 treatment can be used in sturgeon aquaculture practically without any negative impacts on biological or physiological indices.  相似文献   
13.
Thermography is proposed to be an alternative non-destructive and rapid technique for the study and diagnosing of salt tolerance in plants. In a pot experiment, 30 cultivars of wheat (Triticum aestivum L.) were evaluated in terms of their leaf temperature and shoot growth and their ion distribution responses to NaCl salinity at two concentration levels: the control with electrical conductivity (EC) of 1 dS m?1 and salinity treatment with EC of 16 dS m?1 (150 mM). A completely randomized block design with factorial treatments was employed with three replications. The results indicated that thermography may accurately reflect the physiological status of salt-stressed wheat plants. The salt stress-based increase in leaf temperature of wheat cultivars grown at 150 mM NaCl reached 1.34°C compared to the control. According to the results obtained, it appears that thermography has the capability of discerning differences of salinity tolerance between the cultivars. Three salt-tolerant wheat cultivars, namely Roshan, Kharchia and Sholeh, had higher mean shoot dry matter (0.039 g plant?1) and higher mean ratio of leaf K+/Na+ (14.06) and showed lower increase in the mean leaf temperature (0.37°C) by thermography compared to the control. This was while nine salt-sensitive cultivars, namely Kavir, Ghods, Atrak, Parsi, Bahar, Pishtaz, Falat, Gaspard and Tajan, had lower mean plant dry matter production (0.027 g plant?1), lower mean ratio of K+/Na+ (9.49) and higher mean increases in leaf temperature (1.24°C).  相似文献   
14.
Ektaphelenchoides maafiae n. sp. was isolated during a survey of nematodes associated with bark samples of an oak tree (Quercus castaneifolia) in Gorgan, Golestan Province, northern Iran. The new species has a body length of 480–546 μm (in females) and 431–480 μm (in males). The cuticle is weakly annulated, with three lateral lines. Lip region offset. The stylet is 13–15 μm long without basal swellings. The excretory pore is located at the level of the metacorpus base to slightly posterior, and hemizonid is at 15–17 μm posterior to the excretory pore. The post‐uterine sac is short, 6–8 μm long. Spicules having rounded condylus, rostrum short, conical with bluntly pointed tip, a cucullus (apophysis) presented on the dorsal distal end. Male tail bearing four (2 + 2) caudal papillae, conical, with sharply pointed terminus. The new species is close to four known species of the genus, including E. hunti, E. ruehmi, E. caspiensis and E. poinari, but differs from them by body size, shape of tail terminus, stylet length, shape and size of spicules, length of post‐vulval uterine sac and number of caudal papillae. Phylogenetic analysis based on small subunit (SSU) and partial large subunit (LSU) sequences of rDNA confirmed its status as a new species.  相似文献   
15.
Sudden marked increases in the serum potassium concentration, up to 8 to 9 meq L(-1), are the result of transcellular movement of potassium and are associated with profound electrocardiographic abnormalities and fluid shifts. Electrocardiographic changes associated with hyperkalemia have been described in the cat, the dog, the horse and are well documented in man. Since there is no research about the effects of hyperkalemia on electrocardiogram of donkey, the purpose of this study was to induce the experimentally hyperkalemia in donkey and studying the relationship between KCl infusion and changes of ECG, electrolytes of plasma and K content of donkey's red blood cells. This research was carried out in seven clinically healthy female donkeys, injected with 0.35 molar potassium chloride solutions to jugular vein. Results indicated that potassium content of RBC at 30, 45, 60, 75 and 90 min, blood potassium level at 30, 45, 60, 75 and 90 min, blood calcium at 60, 75, 90 and 105, increased significantly and blood magnesium decreased significantly at 135 min. Electrocardiographic changes were first degree A-V block, wandering pacemaker, inversion of negative to positive T-wave, flattening of the P-wave, ventricular premature beat, sinus arrest, bradycardia and sinus tachycardia.  相似文献   
16.
Recently, it is hypothesized that there might be an association between immunological disorders and cervical premalignant and malignant abnormalities. Related studies have been generally focused on some particular autoimmune disease, specially the Systemic Lupus Erythematosus (SLE). This study aimed at comparing the rate of Pap smear abnormalities in female patients with autoimmune diseases and normal counterparts. In a case-control setting, 118 female patients with various autoimmune diseases (the case group) and 118 healthy female counterparts (the control group) were recruited in Tabriz Imam Reza Teaching Centre in a 24 months period of time. The two groups were matched for demographics and known risk factors of cervical malignancy. Frequencies of abnormal Pap smear testing were compared between the two groups. The autoimmune disorders were SLE (74 patients), rheumatoid arthritis or RA (32 patients), systcmic sclerosis or SS (7 patients) and ankylosing spondylitis or AS (5 patients) in the case group. Frequency of abnormal Pap smear testing was significantly higher in the case group comparing with that in the controls (7.6% vs. 1.7%; p = 0.03). Frequency of abnormal Pap smear testing was higher in the patients with SLE (8.1%) and RA (9.3%) comparing with that in the controls; However, these differences were marginally nonsignificant (p = 0.06 and p = 0.07, respectively). Frequency of cases with abnormal Pap smear testing was not statistically different between the autoimmune disorders (p = 0.99). Based on these findings and in conclusion, there might be an association between the autoimmune disorders and occurrence of premalignant or malignant lesions in cervix. Further studies with larger samples sizes are recommended.  相似文献   
17.
To determine the genetic relationship of Iranian viruses, the haemagglutinin (HA) genes from ten isolates of H9N2 viruses isolated from commercial chickens in Iran during 1998–2002 were amplified and sequenced. Sequence analysis and phylogenetic studies were conducted by comparing each isolate with those of the available H9N2 strains at GenBank. All these ten isolates had the same sequence –R-S-S-R/G-L– of proteolytic cleavage site of the HA. Nucleotide sequence comparisons of HA gene from Iranian isolates showed 95.2–99.1% identity within the group. Five isolates had leucine (L) at position 226 instead of glutamine (Q). Phylogenetic analysis showed that all our isolates belonged to the G1-like sublineage. Also these isolates showed some degree of homology with other H9N2 isolates e.g., 94.3–96.9% with qu/HK/G1/97, 96.1–98.6% with pa/Chiba/1/97, 95.6–98.2% with pa/Narita/92A/98, and 94.0–96.3% with HK/1073/99. On the basis of phylogenetic and molecular characterization evidence, we concluded that the H9N2 subtype influenza viruses circulating in chicken flocks in Iran since 1998–2002 had a common origin. The results of this study indicated that all Iranian viruses have the potential to emerge as highly pathogenic influenza virus, and considering the homology of these isolates with human H9N2 strains, it seems that the potential of these avian influenza isolates to infect human should not be overlooked.  相似文献   
18.

Background:

Serologic screening of gastric cancer (GC) by serum pepsinogens (sPG) levels and Helicobacter pylori (Hp) sero-status, though highly informative, has provided heterogeneous results. Here, we have evaluated the modifying effects of demographic factors on the risk impact of Hp sero-status/sPG levels in gastric cancer, with particular emphasis on age.

Methods:

A cross-sectional study was carried out on 1341 individuals (GC = 578, healthy = 763), who were stratified into two age groups: 35-59 years (middle-aged, n = 830) and ≥ 60 years (60 years-plus, n = 511). Demographic factors and serological states (Hp sero-staus and sPG levels) were recorded by subject interview and serum ELISAs, respectively. Covariate-specific odds ratios were calculated by multivariable logistic regression.

Results:

Hp infection was consistently associated with increased sPGI and sPGII levels in the 60 year-plus, but not the middle-aged group. The joint examination of the variable states of the three serum biomarkers (Hp serology, sPGI, and sPGI/II ratio), in the 60 year-plus age group, demonstrated a stepwise escalation of risk from the single (sPGIlow; OR = 2.6), to double (sPGIlow/sPGI/IIlow; OR = 3.55, and Hppositive/sPGIlow; OR = 5.0) and ultimately triple (Hppositive/PGIlow/PGI/IIlow; OR = 10.48) positive states, in reference to the triple negatives. However, this pattern was not exhibited in the middle-aged subjects.

Conclusion:

Age was clearly identified as a modifying factor on the risk projection of the combined states of Hp serology and sPG levels in gastric cancer screening, reflected by the augmented (~10.5 fold) risk of GC in the triple positive (Hppositive/sPGIlow/sPGI/IIlow) 60 year-plus subjects, which was not evident in the middle-aged group. Key Words: Biomarkers, Demography, Age Distribution  相似文献   
19.
The experiments were conducted to examine the effects of five photoperiod regimes (24:00; 16:08; 12:12; 08:16 and 00:24 hours) (Light: Dark) on reproductive traits, development and generation time, survival rate, adult sex ratio and total life span of freshwater cyclopoid copepod, Mesocyclops sp.. Daily offspring production of individual female was monitored from the last moulting until death of all females. Mean daily offspring production affected by photoperiod, with the highest output recorded at 08:16, which was significantly higher than 24:00 and 00:24, but not differ from 12:12 and 16:08. No significant differences were obtained in total egg sacs per female among treatments. Photoperiods other than 12:12 significantly prolonged the inter‐clutch times. A trend of accelerated development and generation time was shown with increasing illumination periods. With the exception of female's life span, the survival rates of offspring and females as well as adult sex ratio were not significantly affected by photoperiod. Based on results of this study, it is recommended that Mesocyclops sp. can tolerate and reproduce in a wide range of photoperiod regimes, however, photoperiod of 08:16 being adopted in controlled culture due to its high reproductive performance, fast development and long longevity.  相似文献   
20.
Fungal and oomycete communities in symptomatic roots, crowns and lower stem tissues of field pea plants from sites across the Canadian prairies were characterized using plate culture and sequence-based identification. Symptomatic plants were sampled at the mid-flowering stage from a total of 21 fields in 2014 and 2015. Fungi and oomycete species were isolated on agar medium and grouped into operational taxonomic groups (OTU) based on their morphology. From the OTUs, 40 fungal and oomycete species were identified according to translation elongation factor-1 alpha or ITS sequences. Fusarium spp. accounted for more than 60 % of total isolations. The fungal communities were similar in roots and crowns, but differed from communities in lower stems. In 2014, the most prevalent fungi isolated from roots were F. avenaceum, F. solani and F. redolens, but F. solani was dominant in 2015. In crown tissues, F. avenaceum was most prevalent in 2014 but F. solani was more prevalent in 2015. Stem tissues were primarily colonized by Peyronellaea spp. (= Ascochyta / Phoma spp.) and Alternaria spp. in 2014, but there was a drastic decrease in Peyronellaea spp. in 2015. This study indicated that climate, primarily precipitation levels, and local edaphic characteristics may play a profound role in the structure of phytopathogen communities associated with the root and foot rot diseases complex of field pea on the Canadian prairies.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号