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   172篇
  免费   2篇
林业   10篇
农学   15篇
基础科学   1篇
  39篇
农作物   58篇
水产渔业   14篇
畜牧兽医   22篇
园艺   3篇
植物保护   12篇
  2023年   2篇
  2022年   10篇
  2021年   14篇
  2020年   12篇
  2019年   13篇
  2018年   10篇
  2017年   14篇
  2016年   12篇
  2015年   10篇
  2014年   12篇
  2013年   17篇
  2012年   9篇
  2011年   11篇
  2010年   8篇
  2009年   5篇
  2008年   8篇
  2007年   2篇
  2006年   1篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
排序方式: 共有174条查询结果,搜索用时 15 毫秒
1.
Separation of X and Y chromosome-bearing sperm is an appropriate method for the selection of desired sex of offspring to increase the profit in livestock industries. The purpose of this study was the production of a monoclonal antibody against recombinant bovine sex-determining region Y protein for separation Y sperm. The hybridoma cells from splenocytes of immunized female's balb/C mice and Sp2/0 cells were made. The binding affinity of our monoclonal antibody (mAbSRY2) was compared with mouse monoclonal SRY-15. The Western blot method indicated that mAbSRY2 successfully detected the rbSRY protein. The specificity and sensitivity of mAbSRY2 is comparable to SRY-15 commercially ones. The SRY gene in 100% of bull semen contains the Y chromosome that had the strongest binding affinity to mAbSRY2 was synthesized. In other words, the binding affinity of semen contains the X sperms near the negative control. In general, this immunological method can help to separate X from Y sperms. However, the mAbSRY2 is bind to Y-bearing sexed sperm, but in the future; the sexed sperms need to apply in farms.  相似文献   
2.
Prunus scoparia is a wild deciduous shrub, usually living on dry calcareous soils of the rocky mountains and has been used as a grafting rootstock for domesticated almonds to provide drought resistance. In the current study, micropropagation ability of P. scoparia was investigated using cytokinin and auxin. Uniform nodal shoot pieces (3–5 cm in length) of seedlings were used as explants. The explants were disinfected with 10% sodium hypochlorite solution. For adventitious shoot induction and proliferation, Murashige and Skoog (MS) media containing 7.00 g/l agar and 30.00 g/l sucrose containing five concentrations of benzyl adenine (BA) (0.00, 0.50, 1.00, 2.00, and 4.00 mg/1) and also containing six concentrations of Thidiazuron (TDZ) (0.00, 0.50, 1.00, 2.00, 5.00, and 7.00 mg/1) were compared. For rooting, in vitro shoots (2–3 cm) were transferred into ½ MS medium supplemented with 30 g/l sucrose, 7.50 g/l agar, and different concentrations of IBA (0.00, 0.25, 0.50, and 1.00 mg/l) and NAA (0.00, 0.25, 0.50, and 1.00 mg/l). Based on the results obtained for shoot proliferation, only 2.00 and 4.00 mg/l BA and 2.00 mg/l TDZ concentrations generated shoots, while other treatments did not show shoot proliferation. Among the three treatments that generated shoots, the best results for shoot number, leaf number, and leaf color quality were observed in media containing 2.00 mg/l TDZ. Based on the results obtained for rooting, the effect of IBA concentrations on the rooting percentage, root number, and root length was significant. Among IBA concentrations, only 0.50 mg/l IBA induced rooting, while there was no rooting in the media containing other IBA concentrations. None of the NAA concentrations showed rooting. In conclusion, MS culture medium supplemented with 2.00 mg/l TDZ and ½ MS culture medium supplemented with 0.50 mg/l IBA are suggested for in vitro shoot proliferation and rooting of P. scoparia, respectively. The results presented herein could be used for in vitro selection and micropropagation of P. scoparia.  相似文献   
3.

Background:

Hypertension is one the most common causes of chronic kidney disease (CKD). One of the major concerns in hypertensive patients is early detection of renal disorders. In the past, serum creatinine (Scr) concentration was used as a marker of kidney function, but it proffers a late reflection of reduced glomerular filtration rate. Cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) have been recently proven to be useful for quantification of CKD. Therefore, we compared the diagnostic value of NGAL with cystatin C and creatinine to evaluate kidney function in hypertensive patients.

Methods:

In this study, 42 hypertensive patients and 30 healthy volunteers were recruited. Serum cystatin C (Scys C) and plasma NGAL were measured using ELISA method. Creatinine, urea, hemoglobin, fibrinogen, and C-reactive protein were measured according to the routine methods. Estimated glomerular filtration rate (eGFR) was considered as the gold standard method (cut-off value of < 78 ml/min/1.73 m2.

Results:

In the patient group, plasma NGAL, cystatin C, and creatinine were all significantly correlated with eGFR, and plasma NGAL correlated best with eGFR. Receiver-operating characteristics analysis indicated that plasma NGAL was a better indicator than creatinine and cystatin C for predicting a GFR < 78 ml/min/1.73 m2. The sensitivity and specificity for NGAL were 96% and 100%, for cystatin C were 92% and 60% and for creatinine were 76% and 47%, respectively.

Conclusion:

Plasma NGAL demonstrated a higher diagnostic value to detect kidney impairment in the early stages of CKD as compared to Scys C and Scr in hypertensive patients.Key Words: Neutrophil gelatinase-associated lipocalin (NGAL), Cystatin C, Creatinine, Hypertension  相似文献   
4.
ABSTRACT

Litopenaeus vannamei postlarvae were exposed to 0, 6, 13, and 19 mg/L total ammonia nitrogen (TAN) treatments. After 45 days, shrimp weight and length were lowest under TAN concentrations of 13 and 19 mg/L (P ≤ 0.05). Maximum weight gain was observed in control and 6 mg/L treatments. Mortality was highest (80.55 ± 4.80%) under 19 mg/L reared in 35 ppt salinity. Average intermolt periods of PLs exposed to 0, 6, 13, and 19 mg/L TAN were 11.5 ± 0.7, 10.8 ± 1.3, 9.4 ± 1.0, and 8.7 ± 0.6 days under 35 ppt and 11.1 ± 0.5, 10.7 ± 0.6, 10.1 ± 0.5, and 9.5 ± 0.2 days under 45 ppt salinity. Although TAN increased postlarvae molting frequency, its negative effects on the shrimp growth and survival of PLs was directly linked to its concentration and exposure duration. Higher salinity reduces the effects of ammonia and increases the survival.  相似文献   
5.
Soybean, as a major oilseed crop, is cultivated in many parts of the world including saline-affected regions. A four-replicated factorial experiment based on a completely randomized design with five salinity levels (control, 50, 100, 150, and 200 mM NaCl) and five wild-type and new mutant cultivars of soybean (Williams, Clark, M-4, M-7, and M-9) was done at two vegetative and reproductive phases to study leaf oxidants, antioxidants and osmolytes under salinity stress. The vegetative phase demonstrated higher K+:Na+ ratio, cell membrane stability, relative water content (RWC) and stomatal conductance to H2O (gs) accompanied with lower oxidative stress, antioxidants and osmolytes contrasting to reproductive phase. At both phenological phases, saline stress stimulated antioxidative defense owing to the enhancement of oxidative stress. The results indicated that mutants possessed a better antioxidative system than their wild-types.  相似文献   
6.
Understanding the vertical and lateral distribution of soil organic carbon (SOC) and soil organic carbon density (SOCD) is indispensable for soil use and environmental management because of their vital role in soil quality assessments. Primarily, they are needed in calculating soil organic carbon storage (SOCS). The objective of this research was to provide digital maps of SOC and SOCD variation as well as their uncertainties at multiple standardized depths (H1: 0–5, H2: 5–15, H3: 15–30, H4: 30–60 and H5: 60–100 cm) using a parsimonious model with optimized terrain-related attributes and satellite-derived data. SOCS were evaluated at soil subgroup levels. An area of about 808 km2 with varying elevation, plant cover and lithology from the Miandoab region, West Azerbaijan Province, Iran was selected as a case study area. A total of 386 soil samples were collected from 104 profiles comprising various soil genetic horizons. A continuous spline function was then fitted to the target properties in advance of creating a dataset at five standard depth intervals (following the GlobalSoilMap project). These were then grouped into three classes including top (H1), middle (H2, H3 and H4) and bottom (H5) depths to ease interpretation. Static and dynamic covariates (30-m resolution) were derived from a digital elevation model (DEM) and a suite of Landsat-8 spectral imageries, respectively. Four candidate models including stepwise multiple linear regression (SMLR), random forest (RF), cubist (CU) and extreme gradient boosting (XGBoost) Tree were tested in this study. Finally, the digital maps at 30-m resolution of SOC and SOCD and their uncertainties were prepared using the best-fit model and the bootstrapping method, respectively. Four soil subgroups (Gypsic Haploxerepts, Typic Calcixerepts, Typic Haploxerepts and Xeric Haplocalcids) were identified across the study area. The covariates had variable contributions on the evaluated models. The XGBoost Tree model generally outperformed other models for prediction of SOC and SOCD (R2 = 0.60, on average). Regardless of soil subgroups, the uncertainty analysis showed that the SOCD map had a low prediction interval range value indicating high accuracy. Additionally, the highest SOCS and SOCD was observed at the top followed by middle and bottom depths in the study area. All subgroups exhibited a decreasing trend of SOCD with increasing depth. A similar trend was also observed for SOCS. The highest SOCD (on average) was observed in Gypsic Haploxerepts (4.71 kg C/m2) followed by Typic Calcixerepts (4.46 kg C/m2), Typic Haploxerepts (4.45 kg C/m2) and Xeric Haplocalcids (4.40 kg C/m2). Overall, the SOCS normalized by area within soil order boundaries was greater in Inceptisols than Aridisols across the study area. The findings of this study provide critical information for sustainable management of soil resources in the area for agricultural production and environmental health in the Miandoab region of Iran.  相似文献   
7.
This study assessed the foliar uptake of 15N-labelled nitrogen (N) originating from wet deposition along with leaf surface conditions, measured by wettability and water storage capacity. Foliar 15N uptake was measured on saplings of silver birch, European beech, pedunculate oak and Scots pine and the effect of nitrogen form (NH 4 + or NO 3 ? ), NH 4 + to NO 3 ? ratio and leaf phenology on this N uptake was assessed. Next to this, leaf wettability and water storage capacity were determined for each tree species and phenological stage, and the relationship with 15NH 4 + and 15NO 3 ? uptake was examined. Uptake rates were on average five times higher (p?<?0.05) for NH 4 + than for NO 3 ? and four times higher for deciduous species than for Scots pine. Developing leaves showed lower uptake than fully developed and senescent leaves, but this effect was tree species dependent. The applied NH 4 + to NO 3 ? ratio did only affect the amount of N uptake by senescent leaves. The negative correlation between measured leaf contact angles and foliar N uptake demonstrates that the observed effects of tree species and phenological stage are related to differences in leaf wettability and not to water storage capacity.  相似文献   
8.
Background: Pseudomonas aeruginosa is one of the opportunistic pathogens causing frequent hospital-acquired life-threatening infections in mechanically ventilated patients. The most significant virulence factor of P. aeruginosa is T3SS. PcrV is an important structural protein of the T3SS. Methods:In the current investigation, a recombinant scFv mAb against the PcrV protein was expressed in EnBase® (fed-batch) cultivation mode. The pETiteTM N-His SUMO Kan vector, including anti-PcrV scFv gene, was transformed into Escherichia coli (BL21) cells. The expression and solubility of anti-PcrV scFv protein were investigated at two different temperatures (25 °C and 30 °C) and at different induction times (4, 6, 8, 12, and 24 hours). Results:Increased efficiency was achieved by EnBase® compared to LB broth; owing to the slow release of glucose, the maximum level of solubility and total protein expression was observed in EnBase® cultivation system at 30 °C and 24 h post induction. Furthermore, IC50 for anti-PcrV scFv protein was determined to be approximately 7 μg/mL. Conclusion:Anti-PcrV scFv produced in this study showed promising in vitro results, protecting RBC from lysis by P. aeruginosa (exoU+). Key Words: Fed Batch, recombinant protein, Pseudomonas aeruginosa, scFv  相似文献   
9.
In recent years several interspecific hybrids have been reported in the plant pathogenic oomycete genus Phytophthora. Due to the large genotypic and phenotypic changes, these hybrids might have broader or more limited host ranges compared with their parental species. It is crucial to understand the host range of Phytophthora hybrids to minimize the economic losses caused by their infection. The potential host range of four hybrids belonging to Clade 8a of the Phytophthora phylogenetic tree was investigated in this study. Thirty species of herbaceous plants as well as eight species of woody plants were inoculated and monitored for any symptom of infection. In addition, the detached twigs of 32 tree species, fruits of six plant species, tubers of potato, and roots of carrot and sugar beet were investigated for susceptibility to these hybrids. Almost all hybrids caused severe rot on all tested fruits, tubers, and roots, although different isolates showed different pathogenicity on detached tree twigs. All hybrids tested had a different host range compared with their parental species: they were able to infect plants outside the host range of their parents, infect hosts of both parental species, although these parents did not have overlapping hosts, or, in some cases, they were not able to infect hosts infected by the parents.  相似文献   
10.
BACKGROUND: The amygdala is a forebrain region, which is known as a modulator of pain sensation. The amygdala, particularly the central nucleus, has high concentrations of enkephalins relative to dynorphins and has high concentrations of opioid receptors. We here studied the role of central nuclei of amygdala in morphine antinociception. METHODS: In this study, we used 130 male Wistar rats (200-250 g). Bilateral two guide cannula were inserted into central nuclei of amygdala. The drugs were administrated via intra central-amygdala and intraperitoneal. The antinociceptive effect was measured by formalin test. RESULTS: Bilateral microinjections of morphine (50 and 100 microg/rat) into the central nuclei of amygdala elicited powerful suppression of nociceptive behaviors in both phases of formalin test. The intraperitoneal administration of naloxone (1 and 2 mg/kg) decreased significantly the antinociception induced by the intra-amygdaloid injection of morphine. Our data also showed that microinjection of naloxone (50 and 100 microg/rat) into the central nuclei of amygdala could reduce the analgesic effects of systemic morphine (7 mg/kg). On the other hand, bilateral neurotoxic lesions of the central nuclei of amygdala attenuated the antinociception induced by subcutaneous or intra-amygdaloid injection of morphine. CONCLUSION: These findings suggest that morphine analgesia in the formalin test depends on ascending connections to the forebrain, probably the amygdala.  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