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   611篇
  免费   22篇
  国内免费   3篇
林业   43篇
农学   28篇
基础科学   4篇
  133篇
综合类   31篇
农作物   71篇
水产渔业   36篇
畜牧兽医   213篇
园艺   18篇
植物保护   59篇
  2023年   7篇
  2022年   8篇
  2021年   20篇
  2020年   20篇
  2019年   27篇
  2018年   34篇
  2017年   42篇
  2016年   27篇
  2015年   12篇
  2014年   31篇
  2013年   57篇
  2012年   43篇
  2011年   34篇
  2010年   26篇
  2009年   21篇
  2008年   24篇
  2007年   27篇
  2006年   13篇
  2005年   15篇
  2004年   15篇
  2003年   9篇
  2001年   7篇
  2000年   9篇
  1999年   4篇
  1998年   4篇
  1997年   4篇
  1996年   5篇
  1993年   2篇
  1992年   5篇
  1991年   9篇
  1990年   10篇
  1989年   6篇
  1988年   6篇
  1987年   6篇
  1986年   6篇
  1985年   3篇
  1984年   4篇
  1983年   2篇
  1981年   2篇
  1980年   4篇
  1979年   4篇
  1977年   1篇
  1976年   1篇
  1975年   5篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
  1970年   3篇
  1969年   3篇
  1964年   1篇
排序方式: 共有636条查询结果,搜索用时 0 毫秒
41.
    
Ohne Zusammenfassung
Observations On The Effect Of Insecticides On Coleopterous Predators OfErioischia Brassicae (Diptera: Anthonmyiidae). Beobachtungen über die Wirkung von Insektiziden auf Prädatoren(Coleoptera) vonErioschia brassicae (Diptera: Anthomyiidae)
  相似文献   
42.
Wood specimens of Casuarina glauca were inoculated withChaetomium spp. andTrichoderma spp., alone or in combination in the presence or abscence of larvae ofStromatium fulvum. All fungal inoculates caused deterioration to the lignin of the wood specimens. The infestation with larvae alone caused the same. The extractive content decreased to a little extent.
Zusammenfassung Bäume von Casuarina glauca wurden mitChaetomium spp. undTrichoderma spp. inokuliert, allein oder in Kombination sowie in Abwesenheit oder Gegenwart der Larven vonStromatium fulvum. Alle Pilz-Inokulate verusachten einen Abbau von Lignin in den Bäumen. Denselben Effekt hatte die Tätigkeit vonStromatium-Larven ohne Pilz-Inokulation. Der extraktive Anteil verminderte sich nur wenig.


With 2 tables  相似文献   
43.
Morinda citrifolia (noni) is known to contain genotoxic anthraquinones in the roots. Because of the widespread use of noni juice, the possible genotoxic risk was examined through a battery of short-term tests. Noni juice was also chemically analyzed for the possible presence of anthraquinones. Noni juice extract in the Salmonella microsome assay showed a slight mutagenic effect in strain TA1537, due to the presence of flavonoids. No mutagenicity was observed in the mammalian mutagenicity test with V79 Chinese hamster fibroblasts. Rats treated with a noni juice concentrate did not show DNA repair synthesis (UDS) in primary rat hepatocytes, nor could DNA adducts or DNA strand breaks be observed. HPLC analysis of noni juice for anthraquinones was negative, with a sensitivity of <1 ppm. In summary, chemical analysis and genotoxicity tests reveal that noni juice does not have a genotoxic potential and that genotoxic anthraquinones do not exist in noni juice.  相似文献   
44.

In the North Nile Delta of Egypt, the impacts of overplanting paddy rice on water delivery performance have not been discussed quantitatively. Further, the amount of water that could have been saved if farmers would follow the planned area is unknown. In this study, water delivery performance was assessed by comparison of actual paddy rice planting and the government’s planned conditions. For both conditions, performance indicators relating to adequacy, equity, and dependability were analyzed across six locations in conjunction with the branch canal water level in 2013 and 2014. Based on the difference between the actual water supply and planned water demand, the amount of water that could have been saved for downstream uses was calculated. The average adequacy for the investigation period was good at one location, fair at 2 locations, and poor at 3 locations in both years. Further, adequacy under both actual and planned conditions was poor in late July at all locations. The planned adequacy and dependability downstream and equity among locations improved compared to the actual condition in both years. Under the condition that paddy rice area is the upper limit planned by the government, about 12.3% and 9.6% of water could be potentially saved in each year. The difference between actual and planned water delivery performance is caused by the branch canal’s low water level. Control of overplanting paddy rice and coordination of water distribution among water user associations would improve stable water level in the canal and, eventually, water delivery performance.

  相似文献   
45.
ABSTRACT

The present investigation was based on the hypothesis that the endophytes residing in the roots of halophytes have better adaptation to saline conditions. Six halophytic herbs were collected from Khewra salt range (EC = 4.7 dS m?1 and SAR = 25.7). From these herbs, root pieces of Cenchrus ciliaris were shade dried; finely ground to powder and three plant growth promoting rhizobacteria (PGPR), Bacillus cereus, Pseudomonad moraviensis, and Stenotrophomonas maltophilia, were isolated. Root powder in sterilized and unsterilized forms was added in the saline-sodic field on wheat and mixed with soil in pot experiment with induced NaCl (150 mM). Sterilized root powder increased organic matter NO3-N and P contents of soil and leaves, fresh weight, sugar content, and yield attributes. The root powder application in unsterilized form significantly decreased EC, SAR, and Na content of field soil with concomitant increase in soil and leaves K, P, and NO3-N. The farmer’s benefit was increased by 33% at yield. Root powder-induced salt tolerance was mediated by the PGPR (residing inside the root) through increased growth and better physiological adaptations. It is inferred that root powder harboring the PGPR may be an alternative to biofertilizer with longer shelf life and may also serve as carrier for the preparation of effective biofertilizer for saline land using other PGPR bio-inoculants.  相似文献   
46.
47.
This study sought to isolate and characterize lactic acid bacteria (LAB) from stomach of adult snakehead fish, Channa striatus, to be used as probiotics for freshwater fish. A total of 13 strains were isolated from the stomach of 10 fish, and 4 of these belonged to LAB. Strain LAB‐3 showing highest in vitro growth inhibition of Aeromonas hydrophila in a disk diffusion test was identified as Lactobacillus fermentum by conventional and molecular techniques and evaluated in vitro through various tests. The bacterium could grow at pH 3–8; but the optimum growth was observed at pH 6. Moreover, LAB‐3 grew at 0.15 and 0.3% bile salt concentrations, from 15 to 45 C, and at 4% NaCl. L. fermentum showed in vitro inhibitory activity against three fish pathogens, A. hydrophila, Pseudomonas aeruginosa, and Shewanella putrefaciens, tested by disk diffusion and well diffusion methods. Antibiotic sensitivity tests indicated that L. fermentum was resistant to streptomycin, gentamycin, and kanamycin, intermediate to tetracycline, but sensitive to chloramphenicol, amoxicillin, and ampicillin. Challenge test by using A. hydrophila showed that survival of snakehead was significantly (P < 0.05) improved when 2 × 106 LAB‐3/g was supplemented to the diet. Therefore, this study suggests that L. fermentum might be a promising probiotic in snakehead aquaculture .  相似文献   
48.
Squamous cell carcinoma was recorded in 22 Nadji and 3 Maeimi sheep aged 3-6 years, of which 22 were females. Sixteen tumours involved the eyes, 7 occurred in the skin at different body sites, one developed in the ear and another in the rectum. In five cases secondary deposits were seen in the lymph nodes, nasal passages and upper lip. Surgical treatment was successful in the early stages of tumour development, but in advanced cases recurrences were noted. Histologically the tumours were typical for squamous cell carcinoma and most of them were well differentiated. Solar radiation was pointed out as a possible factor in the aetioloy of the tumour.  相似文献   
49.
The present research was conducted to study the responses of ‘Malas–e–Saveh’ (M) and ‘Shishe–Kab’ (Sh) Iranian pomegranates to sodium chloride (NaCl) stress under greenhouse and field conditions. Treatments included waters electrical conductivity (EC = 1.5, 3, 6, 9 and 12 dS m?1 for greenhouse) and (EC = 1.05 as control, 4.61 and 7.46 dS m?1 for field studies). Interactive effects of salinity × variety indicated the highest chlorophyll and leaf potassium concentration, and the lowest leaf chloride and sodium in control under greenhouse study. Non-photochemical quenching, effective quantum yield of photochemical energy conversion in PSII reduced under the highest salinity level in field, however, basal quantum yield of non-photochemical processes in PSII increased in the highest salinity. Sodium and chloride increased with increased in salinity. Calcium, magnesium and iron significantly decreased with increased in salinity. It seems that there are differences between pomegranate cultivars and Malas-e-Saveh is more tolerant compared with Shishe Kab.  相似文献   
50.
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