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   203篇
  免费   3篇
林业   10篇
农学   15篇
基础科学   1篇
  42篇
农作物   70篇
水产渔业   24篇
畜牧兽医   27篇
园艺   4篇
植物保护   13篇
  2023年   2篇
  2022年   11篇
  2021年   16篇
  2020年   14篇
  2019年   13篇
  2018年   13篇
  2017年   15篇
  2016年   14篇
  2015年   11篇
  2014年   14篇
  2013年   20篇
  2012年   9篇
  2011年   15篇
  2010年   10篇
  2009年   5篇
  2008年   12篇
  2007年   2篇
  2006年   1篇
  2005年   1篇
  2004年   2篇
  2003年   3篇
  1993年   1篇
  1989年   1篇
  1986年   1篇
排序方式: 共有206条查询结果,搜索用时 15 毫秒
61.
Amylose content is a parameter that correlates with the cooking behavior of rice. It is measured at the earliest possible stages of rice improvement programs to enable breeders to build the foundations of appropriate grain quality during cultivar development. Amylose is usually quantified by absorbance of the amylose‐iodine complex. The International Network for Quality Rice (INQR) conducted a survey to determine ways that amylose is measured, reproducibility between laboratories, and sources of variation. Each laboratory measured the amylose content of a set of 17 cultivars of rice. The study shows that five different versions of the iodine binding method are in use. The data show that repeatability was high within laboratories but reproducibility between laboratories was low. The major sources of variability were the way the standard curve was constructed and the iodine binding capacity of the potato amylose used to produce the standard. Reproducibility is much lower between laboratories using a standard curve of potato amylose alone compared with those using calibrated rice cultivars. This study highlights the need to standardize the way amylose is measured, and presents research avenues for doing so.  相似文献   
62.
The supercritical fluid extraction (SFE) of the aerial parts of Perovskia atriplicifolia Benth. was studied. The effect of different parameters such as pressure, temperature, modifier identity, and modifier volume on the SFE of the plant was investigated. The extracts were analyzed by GC and GC-MS and compared with the essential oil obtained from P. atriplicifolia Benth by steam distillation. The supercritical extracts and the steam-distilled products had very different compositions. The main constituents of the oil obtained by steam distillation were 1,8-cineole, limonene, camphor, beta-caryophyllene, alpha-pinene, camphene, and alpha-humulene. On the other hand, the major components of SFE extracts were 1,8-cineole, limonene, camphor, beta-caryophyllene, gamma-cadinene, alpha-pinene, and alpha-terpinyl acetate. The results showed that increasing the temperature from 35 to 65 degrees C (at a constant pressure of 100 atm) drastically reduced the number of extracted components. Also, the number of extracted constituents and the percent of main analytes increased when lower pressures were used. Using different modifiers (e.g., methanol, ethanol, dichloromethane, and hexane) for the extraction of the plant at low pressure (100 atm) and temperature (35 degrees C) showed that hexane was more selective than the other modifiers.  相似文献   
63.
A 90‐day feeding trial was carried out to examine the influence of fish oil (FO) substitution with blends of vegetable oils (VOs) on reproductive efficiency of female brooders and fluctuation in fatty acid (FA) profile of embryos in Oncorhynchus mykiss. A basal diet was formulated in which 20% (80FO/20VO), 50% (50FO/50VO), 75% (25FO/75VO) and 100% (100VO) of FO were replaced by mixture of VO. Reproductive performance of brooders was not affected by drastic alternations in FA profile of diets. The level of saturated and monounsaturated FAs (MUFAs) significantly increased, whereas the levels of long‐chain polyunsaturated FAs (LC‐PUFAs), mainly docosahexaenoic acid, profoundly decreased during embryogenesis. The concentrations of MUFA and n?6 PUFA increased in the eggs with increasing the incorporation of VO mixture in diets; however, the concentration of LC‐PUFA and n?3/n?6 PUFA ratio decreased. Haematological parameters and humoral immune responses including total immunoglobulin content, lysozyme and alternative complement pathway activities in brooders fed with the experimental diets did not statically different. In summary, incorporating mixture of various VO sources especially linseed and sunflower oils as good sources of α‐linolenic and linoleic acids, respectively, along with low levels of residual fat from fish meal in diet suggested a good strategy for providing the appropriate essential FA requirements of O. mykiss brooders for their successful reproduction.  相似文献   
64.
European Journal of Plant Pathology - In this study, inhibitory effects of the aqueous and ethanolic leaf extracts obtained from marshmallow (A. officinalis) were evaluated against Alternaria spp.,...  相似文献   
65.
This research was conducted to quantify total phosphorus (TP) losses in poorly drained-consolidated paddy fields equipped with different surface and shallow subsurface drainage systems including drain depth of 0.9 m and drain spacing of 30 m (D0.9L30), drain depth of 0.65 m and drain spacing of 30 m (D0.65L30), drain depth of 0.65 m and drain spacing of 15 m (D0.65L15), drain spacing of 15 m and drain depths of 0.65 and 0.9 m as alternate depths (Bilevel). Typical surface drainage system of consolidated paddy fields was also considered as conventional practice of the study area (control). The subsurface drained fields were under year-round crop production of rice-canola, while the surface drained fields experienced only rice cropping once a year. During three rice-canola-rice growing seasons, TP losses through drainage and leaching in the D0.9L30, Bilevel, D0.65L30, D0.65L15 and control treatments were respectively, 1.12, 0.98, 1.44, 1.53 and 24.48 kg ha?1, equivalent to about 3.9%, 3.4%, 5.1%, 5.3% and 85.7% of applied triple superphosphate fertilizer. In the rice growing seasons, TP losses through surface runoff were higher than those through subsurface drainage effluents. Shallow subsurface drainage systems were promising for the study area compared surface drainage as phosphorus risks were reduced by 79%, 77%, 64% and 57% through D0.9L30, Bilevel, D0.65L30 and D0.65L15, respectively. These results demonstrated that, by providing suitable condition for winter cropping, subsurface drainage systems can diminish concerns related to phosphorus losses from poorly drained paddy fields in the north of Iran.  相似文献   
66.
Background: Although effects of trace elements on secretion of sex steroids and insulin have been studied, the effects of these hormones on serum level of trace elements have been rarely investigated. The aim of the present study was to evaluate the effect of testosterone and finasteride administration and castration on serum levels of testosterone, insulin, zinc and chromium. Methods: Male adult rats (n = 32) were divided into 4 groups (n = 8). Group 1, control; Group 2, castration, castration was done at the first day of the study; Group 3, finasteride (20 mg/kg/day, dissolved in drinking water) and Group 4, testosterone (5 mg/kg/day, i.p.). At the end of the period of the study (35 days), serum testosterone, insulin, zinc and chromium levels were determined in the blood samples collected directly from the right atrium of the heart of the animals. Results: The data indicated that the serum levels of testosterone, insulin and zinc were significantly increased (P<0.01) in testosterone-administrated and finasteride groups, but the level of chromium was decreased in both groups (P<0.01). Castrated group had the lowest serum levels of testosterone, insulin and zinc (P<0.05). Also, the levels of serum chromium in this group were increased. Conclusion: The study demonstrates that testosterone and finasteride increases insulin and zinc levels and decreases chromium levels in the serum of male adult rats. According to these data, it seems that testosterone may affect glucose cycle through effect on serum insulin levels and trace elements such as zinc and chromium. Key Words: Finasteride, Castration, Insulin, Zinc, Chromium  相似文献   
67.
Background: The secretion of thyroxin (T4) as the main hormone of thyroid gland is regulated by androgens. The present study aimed to evaluate the effect of testosterone and finasteride administration and castration on serum levels of T4 and to show the effect of this regulation on total body weight, weight of testis, and the weight of prostate. Methods: Male adult rats (n = 32) were divided into 4 groups (n = 8): Group 1 (control), Group 2 (castration), Group 3 (finasteride: 20 mg/kg/day) and Group 4 (testosterone: 5 mg/kg/day). At the end of the study (35 days), serum level of thyroxin, body weight, weight of testis, and prostate were determined. Results: The data showed that the body weight increased in castrated (P = 0.04) and decreased in testosterone (P = 0.00) groups but did not differ in finasteride (P>0.05) group. There were not any differences in the weight of testis among control, finasteride, and testosterone groups but the weight of prostate increased in testosterone group (P = 0.00) and decreased in castrated (P = 0.03) and finasteride groups (P = 0.04). In addition, the serum level of T4 (nmo/ml) decreased in the three groups: finasteride (P = 0.03), testosterone (P = 0.04), and castrated (P = 0.00). Conclusion: Testosterone in both high and low levels decreased the amount of T4 with a time-dependent manner. Key Words: Finasteride, Rats, Testosterone, Thyroxin  相似文献   
68.
Cyanobacteria are photosynthetic prokaryotic organisms which represent a significant source of novel, bioactive, secondary metabolites, and they are also considered an abundant source of bioactive compounds/drugs, such as dolastatin, cryptophycin 1, curacin toyocamycin, phytoalexin, cyanovirin-N and phycocyanin. Some of these compounds have displayed promising results in successful Phase I, II, III and IV clinical trials. Additionally, the cyanobacterial compounds applied to medical research have demonstrated an exciting future with great potential to be developed into new medicines. Most of these compounds have exhibited strong pharmacological activities, including neurotoxicity, cytotoxicity and antiviral activity against HCMV, HSV-1, HHV-6 and HIV-1, so these metabolites could be promising candidates for COVID-19 treatment. Therefore, the effective large-scale production of natural marine products through synthesis is important for resolving the existing issues associated with chemical isolation, including small yields, and may be necessary to better investigate their biological activities. Herein, we highlight the total synthesized and stereochemical determinations of the cyanobacterial bioactive compounds. Furthermore, this review primarily focuses on the biotechnological applications of cyanobacteria, including applications as cosmetics, food supplements, and the nanobiotechnological applications of cyanobacterial bioactive compounds in potential medicinal applications for various human diseases are discussed.  相似文献   
69.
The main aim of this study was to evaluate the effects of dextromethorphan and midazolam and their combination on morphine tolerance and dependence in mice. In the present study, different groups of mice were rendered randomly and received morphine (50 mg kg(-1), s.c.), morphine (50 mg kg(-1), s.c.) + Dextromethorphan (25, 50 and 75 mg kg(-1), i.p.), morphine (50 mg kg(-1), s.c.) + midazolam (0.5, 1 and 2 mg kg(-1), i.p.), morphine (50 mg kg(-1), s.c.) + [Dextromethorphan (25 mg kg(-1), i.p. ) + midazolam (0.5 mg kg(-1), i.p.)] once a day for four days. Tolerance was assessed by administration of morphine (9 mg kg(-1), i.p.) on fifth day. Withdrawal symptoms (markers for dependence) was assessed by administration of naloxone (4 mg kg(-1), i.p.) 2 h after co-administration of morphine with either Dextromethorphan or midazolam or their combination. Results showed that pretreatment with Dextromethorphan or midazolam decreased the degree of tolerance and withdrawal symptoms significantly. Additionally co-administration ofDextromethorphan and midazolam couldn't decreased the tolerance and dependence significantly. From these results it may concluded that Dextromethorphan and midazolam alone or in combination could prevent the development of morphine induced tolerance and dependence. These effects can be related to the N-Methyl-D-Aspartate (NMDA) receptor antagonist behavior of Dextromethorphan and GABA-receptor agonist property of midazolam.  相似文献   
70.
The presence and vasoactive effects of native calcitonin gene-related peptide (CGRP), substance P (SP), and neurokinin A (NKA) were studied on isolated small branches of the coeliac artery from Atlantic cod, Gadus morhua, using immunohistochemistry and myograph recordings, respectively. Immunohistochemistry revealed nerve fibers containing CGRP- and SP/NKA-like material running along the wall of the arteries. CGRP induced vasorelaxation of precontracted arteries with a pD2 value of 8.54 ± 0.17. Relaxation to CGRP (10−8 M) was unaffected by l-NAME (3 × 10−4 M) and indomethacin (10−6 M) suggesting no involvement of nitric oxide or prostaglandins in the CGRP-induced relaxation. SP and NKA (from 10−10 to 3 × 10−7 M) contracted the unstimulated arteries at concentrations from 10−8 M and above in 42% and 33%, respectively, of the vessels. It is concluded that the innervation of the cod celiac artery includes nerves expressing CGRP-like and tachykinin-like material, and that a vasodilatory response to CGRP is highly conserved amongst vertebrates while the response to tachykinins is more variable.  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