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   78篇
  免费   1篇
林业   3篇
农学   3篇
基础科学   4篇
  11篇
综合类   5篇
农作物   4篇
水产渔业   1篇
畜牧兽医   34篇
园艺   7篇
植物保护   7篇
  2021年   1篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   1篇
  2015年   4篇
  2014年   2篇
  2013年   6篇
  2012年   7篇
  2011年   4篇
  2010年   4篇
  2009年   2篇
  2008年   10篇
  2007年   1篇
  2006年   6篇
  2005年   3篇
  2004年   1篇
  2003年   3篇
  2002年   2篇
  2001年   1篇
  2000年   1篇
  1999年   4篇
  1993年   1篇
  1989年   1篇
  1986年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1972年   2篇
  1970年   1篇
  1967年   1篇
排序方式: 共有79条查询结果,搜索用时 18 毫秒
31.
Thirty-six new nitro-alcohol derivatives were synthesised. Tested in vitro against Helminthosporium sativum, the compounds had high antifungal activities; the EC50 values varied between 10?2 and 10?6 M , and for the majority of the compounds between 10?4 and 10?6 M . The EC50 values were calculated by probit analysis, except for the compounds with low activity, for which the values were estimated. Interesting relationships between the structure and antifungal action of the compounds were established.  相似文献   
32.
We performed a 2-year microcosm study to assess the effectiveness of red mud, a by-product of bauxite processing, in stabilizing contaminated mine waste and agricultural soil. Our study used red mud from a long-term disposal area in Almásfüzit?, Hungary with a pH of 9.0. A 5% (by weight) red mud addition decreased the highly mobile, water-extractable amount of Cd and Zn by 57% and 87%, respectively, in the agricultural soil and by 73% and 79%, respectively, in the mine waste. In a laboratory lysimeter study, the addition of red mud reduced the concentration of Cd and Zn in the leachate by about two third of the original. The metal content of the leachate was below the Maximum Effect Based Quality Criteria for surface water as determined by a risk assessment in the metal-contaminated area of the Toka valley near Gyöngyösoroszi, Hungary. The addition of red mud did not increase the toxicity of the treated mine waste and soil and decreased the Cd and Zn uptake of Sinapis alba test plants by 18–29%. These results indicate that red mud applied to agricultural soil has no negative effects on plants and soil microbes and decreases the amounts of mobile metals, thus indicating its value for soil remediation.  相似文献   
33.
Previous investigations have shown that selenium supplementation inhibits growth of mastitis pathogens in cow's milk. The present study was performed to clarify the role of selenium in defence mechanisms of mammary gland. We have examined the effects of selenium supplementation on Staphylococcus aureus growth inhibiting activity in whey. Six selenium-supplemented and six non-supplemented Estonian dairy cows were used for this study. Selenium-supplemented cows received 4 mg organic selenium in the form of selenium yeast in their daily diet for 8-week period. Cows from non-supplemented group received the same amount of yeast free of selenium in their diet. All cows had initially low blood glutathione peroxidase (GPx) activity (相似文献   
34.
Simultaneous analysis of two myogenin (MYOG) loci has been carried out using polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) tests in DNA isolated from blood samples collected from four different pig breeds (Hungarian Large White, Duroc, Mangalica and Hungarian Landrace). The following MYOGA frequency values have been obtained: Hungarian Large White 0.2416; Duroc 0.0900; Mangalica 0.6617; Hungarian Landrace 0.2361. The MYOG2 allele was found in Duroc and Mangalica breeds only. This test allows the analysis of two loci of the MYOG gene in parallel, which might be used in marker assisted selection programmes in the near future. Ongoing studies on the possible effects of the MYOG types on carcass and growth traits are outlined.  相似文献   
35.
Facilitating human-carnivore coexistence is a major conservation concern in human-dominated landscapes worldwide. Useful insights could be gained by studying and understanding the dynamics of human-carnivore coexistence in landscapes in which carnivores and humans have coexisted for a long time. We used a two-pronged approach combining ecological and social data to study coexistence of the brown bear (Ursus arctos) and humans in Transylvania, Romania. First, we surveyed 554 km of walking transects to estimate activity via a bear sign index, namely the proportion of anthills disturbed by bears, and used spatially explicit predictive models to test which biophysical and anthropogenic variables influenced bear activity. Second, we interviewed 86 shepherds and 359 villagers and community representatives to assess conflicts with bears and attitudes of shepherds towards bears. Our interdisciplinary study showed that bears and humans coexisted relatively peacefully despite occasional conflicts. Coexistence appeared to be facilitated by: (1) the availability of large forest blocks that are connected to the source population of bears in the Carpathian Mountains; (2) the use of traditional livestock management to minimize damage from bears; and (3) some tolerance among shepherds to occasional conflict with bears. In contrast, bear activity was unrelated to human settlements, and compensation for livestock losses did not influence people’s attitudes toward bears. Our study shows that coexistence of humans and carnivores is possible, even without direct economic incentives. A key challenge for settings with a discontinuous history of human-carnivore coexistence is to reinstate both practices and attitudes that facilitate coexistence.  相似文献   
36.
Autologous vascular patch grafts developed from the internal rectus sheath were implanted onto the bilateral common iliac vein and jugular vein of 4 experimental beagle dogs. During the development and implanting of the grafts no technical difficulties or perioperative complications were encountered. The follow-up lasted 6 months and 3 months in the case of the common iliac vein grafts and the jugular grafts, respectively. In the postoperative period, the morphological and functional characteristics of the implanted venous sections were examined by Doppler ultrasonography and CT angiography. Normal patency was detected, and none of these check-ups showed obturation or stenosis. The histological survey showed no mesothelial cell layer, but the insides of the grafts showed total restructuring and were covered by a normal endothelial layer. No difference could be detected between samples harvested 3 and 6 months after implanting. The immunohistochemical examinations using anti-claudin-5 and anti-CD31 antibodies confirmed the preliminary results of the histological examinations that the luminal surfaces of the implanted grafts developed a differentiated monolayer endothelium which was free of degenerative and inflammatory signs. The control examinations show the suitability of the internal rectus sheath as a venous wall donor.  相似文献   
37.
Effects of various aluminum (AlCl3) concentration and exposure times (6, 12, and 24 h and 3 d) on growth and potassium (K) transport were studied in two wheat species (Triticum aestivum L. cv. Jubilejnaja 50 and Triticum durum Desf. cv. GK Betadur) grown in low salt conditions hydroponically. In longer (3 d) Al exposure times at pH 4.1, the inhibition of root growth appeared at 10 μM Al3+ treatment in GK Betadur, and at 50 μM Al3+ treatment in Jubilejnaja 50. Shoot growth was not influenced by Al3+ treatment, except at 100 μM in 7 d experiments. In 6, 12, and 24 h Al3+ exposure times, at low pH, the K+(86Rb) influx in roots increased as the Al3+ concentration increased in the outer medium in both species. It also appeared in K+(86Rb) transport toward the shoots, except by higher Al3+ treatments of GK Betadur seedlings. At the same time, in longer‐term (3 d) Al3+ treatments, a striking inhibition were observed in K+(86Rb) influx and K+ concentration of roots and shoots. The K+concentration of roots and shoots measured at the end of 24 h Al3+ exposure times was significantly not affected by Al3+ treatment. Durum wheat proved to be more sensitive to the Al toxicity than common winter wheat.  相似文献   
38.
Green pepper (Capsicum annuum L.) field experiments were conducted in Northeastern‐Japan in order to evaluate the effects of band and broadcast applications of a polyolefin‐coated fertilizer (POCF) on yield of green pepper grown on Andisol in comparison with conventional, rapidly available fertilizers (RAF). POCF broadcast treatment produced the best yield while POCF band treatment and RAF treatment gave similar results. At the POCF treatments similar or better nutrient uptake was observed than in the RAF treatment resulting similar or better fresh and dry matter productions and consequently similar or higher fruit yield. Thus, by using POCF, labor and energy costs and environmental loading can be reduced without any yield decrease. Among the relatively cold field conditions roots could not reach the POCF band quickly, that caused slower early plant development and eventually lower yield than in comparison with the broadcast application. The very low pH of the soil solutions, having taken from the POCF band throughout the growing period, provided a further possible explanation for the inferiority of band application method. According to these results for green peppers grown on Andisol in Northeastern Japan the broadcast application of POCF is a more effective fertilization method than the band application.  相似文献   
39.
The genetic relationship between 195 Mangalica and 79 non‐Mangalica pigs was studied using mitochondrial D‐loop SNP genotyping. Altogether, 35 polymorphic sites and 27 haplotypes were identified. Of the haplotypes, eight and 16 are Mangalica and non‐Mangalica specific, respectively, while three contain both Mangalica and non‐Mangalica individuals. Genetic distance values and phylogenetic analysis indicate that Mangalica individuals are very closely related, and five haplotypes represent approximately 92% of the Mangalica pigs involved in the study, thus determining the major maternal lineages. In contrast to previous microsatellite studies, individuals of Mangalica could not be distinguished as three separate breeds using mtDNA genotyping. Comparing modern and archaeological mtDNA sequences revealed that present day Mangalica is related to pigs that lived in the Carpathian basin where postulated ancestors of Mangalica also lived. This is the first DNA‐based genetic evidence to support the described breeding history of Mangalica.  相似文献   
40.

Context

Genetic diversity of sessile oak (Quercus petraea) populations in Hungary was assessed close to the retracting, low-elevation, low-latitude (xeric) distribution limits.

Objective

We aimed at tracing an assumed effect of climatic factors on genetic diversity, particularly at the southern, low elevation limits of distribution.

Methods

Genetic diversity at isozyme-coding loci was analysed in populations, and related to the climate of the sites where the populations grow. A locus-wise analysis proved to be essential to follow responses.

Results

A climate-related cline was found at seven isoenzyme-coding gene loci. Declining allelic numbers and heterozygosity indicated lower diversity at warmer and drier sites. The majority of loci were responsive to precipitation factors, others to temperature. Genetic clustering was neither related to geographic distance nor to random or historic effects.

Conclusions

The results suggest that climatic stress may elicit a genetic diversity loss in populations, which may reduce their plasticity and adaptive potential. The selective pressure may override historic effects and gene flow. With respect to expected climate change, the correlation of diversity with some climatic factors gains specific importance. If supported by further investigations, the results might be utilised for reconsidering conservation strategies and rules for use of forest reproductive material.  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