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   344篇
  免费   26篇
林业   14篇
农学   17篇
基础科学   8篇
  106篇
综合类   6篇
农作物   72篇
水产渔业   56篇
畜牧兽医   55篇
园艺   8篇
植物保护   28篇
  2023年   4篇
  2022年   8篇
  2021年   12篇
  2020年   15篇
  2019年   24篇
  2018年   27篇
  2017年   48篇
  2016年   37篇
  2015年   15篇
  2014年   22篇
  2013年   38篇
  2012年   22篇
  2011年   36篇
  2010年   20篇
  2009年   2篇
  2008年   14篇
  2007年   11篇
  2006年   9篇
  2005年   1篇
  2004年   4篇
  2002年   1篇
排序方式: 共有370条查询结果,搜索用时 15 毫秒
1.
Possibility of using interspecific hybridization to increase genetic diversity of drought tolerance in safflower (Carthamus tinctorius L.) and effectiveness of different selection methods is poorly understood. The main objectives of this study were to evaluate the effectiveness of (a) interspecific hybridization to expand genetic diversity in safflower for agronomic traits and drought tolerance in advance generations and (b) different selection methods (direct vs. indirect) for improving seed yield. Interspecific hybridizations were performed between species of C. tinctorius × C. palaestinus (TP), C. palaestinus × C. oxyacantha (PO) and C. tinctorius × C. oxyacantha (TO). Based on the field screening of genotypes in F3 generation, four groups of selected genotypes (derived from combination of direct and indirect selection under both drought and normal environments along with selection based on drought tolerance index (STI)) were evaluated in F4 and F5 generations. Indirect selection for seed yield was significantly more efficient than direct selection. Selection in stress environment resulted to more efficiency than selection in normal environment. No significant difference was observed between direct selection and selection based on STI. The result showed that TP was the best population to combine high seed yield and drought tolerance in safflower.  相似文献   
2.
Madder is a natural colorant which is commonly applied with metal salts as a mordant to improve its affinity to fibers and color fastness. Madder produces an insoluble complex or lake in the presence of metal ions on mordanted fabric. In this study, wool fabric was pretreated with AgNPs (silver nanoparticles) as a mordant, then dyed with madder. The wool fabric samples were examined by scanning electron microscopy (SEM) and their colorimetric characteristics were evaluated. The formation of spherical silver nanoparticle was confirmed using UV-Visible spectroscopy, SEM images, and elemental analysis. The average size of synthesized silver nanoparticles on the surface of wool fibers is around 73 nm. The dyed wool samples were pretreated with different concentration of Ag+ ions or AgNPs, which showed higher color strength value compared to untreated dyed wool fabric. This pretreatment also presented good antibacterial activity.  相似文献   
3.
Protective effects of nanochitosan/zeolite composite besides zeolite and chitosan/zeolite composite on rainbow trout growth, digestive enzyme activities and biochemical parameters were studied. Nanochitosan/zeolite hybrid composites with three different ratio of nanochitosan:zeolite (35:100, 3.5:100 and 0.35:100) were synthesized and analysed by X‐ray powder diffraction (XRD), thermal gravim (TG) analysis and scanning electron microscope (SEM) methods. Prepared composites as well as zeolite and control diets were fed to rainbow trout (50 g) for a period of 60 days. The addition of treated diets significantly improved growth performance compared to the control diet. Supplemental zeolite could only enhance the amylase activity in fish intestine, whereas other treatment groups could increase the pepsin activity besides intestinal alkaline phosphatase, trypsin and amylase activities. No differences were observed for intestinal acid phosphatase and lipase activities among the experimental diets. Meanwhile, serum total antioxidant activity and lipid peroxidation product, indicated by malondialdehyde (MDA), significantly increased and decreased, respectively, with some doses of administration, indicating the elevated antioxidant status in treatment groups. Serum‐specific marker enzymes, namely aspartate aminotransferase (AST) and alkaline phosphatase (ALP), were not affected in all groups. Meanwhile serum total protein in most treatment groups was significantly higher than the control group. Results showed that synthesized composites especially nanochitosan/zeolite composite at 5 g/kg had potential to enhance growth performance, digestive enzyme activities and some biochemical parameters in rainbow trout.  相似文献   
4.
Tropical Animal Health and Production - This study was conducted to evaluate the male effect on the manifestation of estrus and feeding behavior of Afshari ewes during their breeding season. The...  相似文献   
5.
Polyvinylidene fluoride (PVdF) membranes in spite of having many critical properties necessary for lithium-ion batteries, do not have satisfying thermal and mechanical resistance. The goal of this study was to combine the good mechanical and thermal properties of PP nonwoven fabric with the excellent electrochemical properties of PVdF nanofibers to exploit a high-performance membrane for lithium-ion batteries. This work reports the preparation of PVdF nanofiber membranes using electrospinning on a polypropylene (PP) spunbonded nonwoven fabric and an aluminum foil followed by a hot-pressing treatment. The morphology and size of the membranes were studied by the scanning electron microscopy. The tensile strength of the membrane with the PP support was superior to the PVdF membrane. Thermal stability of the prepared membranes was determined using the TGA method and the dimensional stability was investigated by measuring the shrinkage ratio at 105 °C. The results have shown that the PVdF/PP membrane was thermally more stable than the PVdF and the commercial Celgard 2325 membranes. The batteries using PVdF/PP membrane exhibited higher electrochemical oxidation limit, better cycling performance and less discharge capacity fading during 100 cycles compared to PVdF and Celgard membranes. The results of this study showed that PVdF/PP membrane is a promising advanced membrane in lithium-ion batteries.  相似文献   
6.
The genus Ganoderma Karst. has broad‐spectrum usage in biotechnology, medicine and the food industry. The complexity of the morphology within species has led to uncertain identification in the past, but recent advancements in molecular identification methods have provided scientists with the opportunity to better understand the taxonomy of the species. The present study attempts for the first time to elucidate the distinctiveness of the Ganoderma species growing in Iran concerning those elsewhere in the world based on mitochondrial small subunit ribosomal DNA (mtSSU rDNA) and internal transcribed spacer (ITS) sequence data. The results disclosed that the G. lucidum Karst. samples collected in Iran are more similar to the European Ganoderma species than to the Asian (Chinese) one used in this study.  相似文献   
7.
8.
9.
10.
OBJECTIVE: To assess the effects of socio-economic status (SES) on BMI, waist:hip ratio (WHR) and waist circumference (WC) in a group of Iranian women. METHODS: A cross-sectional study was conducted on 888 women in Sistan and Baluchestan Province. SES was measured using level of education. In addition, parity, marital status and physical activity were assessed. Standardized measurements were taken, BMI and WHR were calculated. RESULTS: Low education level was a strong determinant of overweight and obesity among Iranian women. After controlling for age, women with higher education level had significantly lower BMI, WC and parity. Multiple linear regression analysis found a significant negative association of BMI and WC with education level and a significant positive association of BMI and WC with parity. Significant factors associated with obesity by a logistic regression model were education level (OR for university graduates v. illiterate or low literacy levels: 1.00 v. 3.70; P = 0.01), living with spouse (OR for married v. single subjects: 1.00 v. 0.15; P = 0.05), parity (OR for more than five v. less than two pregnancies: 1.00 v. 0.34; P = 0.03) and WC (OR for < 0.88 cm v. > or = 0.88 cm: 1.00 v. 11.20; P = 0.001). CONCLUSION: The present study revealed that educational level, multiple pregnancies, marital status and lack of exercise are some possible explanations for the obesity among Sistan and Baluchestan women.  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