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   319篇
  免费   18篇
林业   11篇
农学   5篇
基础科学   5篇
  108篇
综合类   21篇
农作物   14篇
水产渔业   40篇
畜牧兽医   114篇
园艺   4篇
植物保护   15篇
  2024年   1篇
  2023年   2篇
  2022年   3篇
  2021年   7篇
  2020年   8篇
  2019年   7篇
  2018年   11篇
  2017年   7篇
  2016年   9篇
  2015年   10篇
  2014年   12篇
  2013年   18篇
  2012年   21篇
  2011年   22篇
  2010年   9篇
  2009年   9篇
  2008年   20篇
  2007年   28篇
  2006年   18篇
  2005年   24篇
  2004年   18篇
  2003年   10篇
  2002年   14篇
  2001年   5篇
  2000年   4篇
  1999年   5篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1994年   2篇
  1993年   2篇
  1992年   4篇
  1991年   5篇
  1990年   5篇
  1985年   2篇
  1982年   2篇
  1977年   3篇
  1971年   1篇
  1969年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有337条查询结果,搜索用时 15 毫秒
81.
沙棘,亚欧种,1753年植物学家Karl von Linné发现了沙棘并分类为"植物志"的第1023种.沙棘(Hippophae rhamnoides)被认为是希腊语"闪闪发亮的马"的语源.罗马尼亚的专家论证了沙棘对动物健康的影响,特别是皮肤方面,沙棘还有着消除肠内病菌的作用.  相似文献   
82.
Highly sensitive enzyme-linked immunoassays for chlorpyrifos, one of the most applied insecticides, are presented. Several haptens were synthesized for immunoreagent production and ELISA development. The best immunoassays obtained are based on an indirect coated-plate immunoassay format. Two assays were optimized; one shows a limit of detection of 0.3 ng L(-1), an I50 of 271 ng L(-1), and a dynamic range between 4 and 16 474 ng L(-1). The other one has a limit of detection of 0.07 ng L(-1), an I50 of 7 ng L(-1), and a dynamic range between 0.4 and 302 ng L(-1). The assays were used to quantify chlorpyrifos in olive oil using a simple and rapid sample extraction procedure. The good recoveries achieved in both assays (109% mean value) and the agreement with values given by the GC reference method (110% mean value) indicate their potential for either screening or laboratory quantification.  相似文献   
83.
The grafting of the rootstock with the lemon tree is an agronomical technique used to improve production and/or quality of the fruit. The interstock has been used with different fruit trees to modulate the tree size, fruit production and quality, and the aging of the tree. The lemon trees grafted with interstocks increase their longevity, lemon production and quality; interstocks are also used to decrease the thickness of the trunk at the grafting point. This enlarging of the trunk provokes a decrease of the sap flow. In our study, "Verna" lemon trees were grafted with interstock between the rootstock and the lemon tree to follow the flavonoid content of the lemon juice. The lemon juice was obtained from the lemons collected of the grafted lemon trees. Two types of rootstocks were used: Citrus aurantium L. and Citrus macrophylla L. Seven interstocks from five cultivars of orange tree, one cultivar of lime tree, and one cultivar of tangerine tree were used. "Verna" lemon trees were also grafted directly to the rootstock. The rootstock was more important agronomic factor than the interstock on the total flavonoid content of lemon juice. The interstock grafting had only a small influence on the flavonoid content of the lemon juice, and it modulated the individual flavonoid content. Citrus aurantium L. rootstock and "Berna" and "Washington Navel" interstocks were the most appropriate to graft in the lemon tree. This interstock grafting technique does not increase the flavonoid content of the lemon juice. Regarding the individual flavonoids, the 6,8-di-C-glucosyl diosmetin was the most affected flavonoid by the type of rootstock used. The interstock used is able to alter the individual quantitative flavonoid order of eriocitrin, diosmin, and hesperidin. In addition, the HPLC-ESI/MS(n) analyses provided the identification of two new flavonoids in the lemon juice: Quercetin 3-O-rutinoside-7-O-glucoside and chrysoeriol 6,8-di-C-glucoside (stellarin-2). The occurrence of apigenin 6,8-di-C-glucoside (vicenin-2), eriodictyol 7-O-rutinoside, 6,8-di-C-glucosyl diosmetin, hesperetin 7-O-rutinoside, homoeriodictyol 7-O-rutinoside and diosmetin 7-O-rutinoside was also confirmed in lemon juice by this technique.  相似文献   
84.
This paper describes a series of experiments designed to recover phosphorus and nitrogen from sewage in the form of struvite (MgNH(4)PO(4).6H(2)O), a potential fertilizer. Nitrogen and phosphate were recovered from a filtrate of digested sludge dewatered at the Arroyo del Soto Waste Water Treatment Plant (WWTP) (Madrid, Spain). A byproduct of the Spanish magnesite mining and MgO production industry was used as the magnesium source. The precipitating performance of this byproduct was compared to that of conventional chemical reagents such as pure MgO. The precipitates obtained were subjected to chemical, light microscopy, and X-ray diffraction analysis. The findings indicate the precipitate recovered using this byproduct contains several minerals with a predominance of struvite. Optimal purity ( approximately 80% struvite) was achieved using the sieved <0.04 mm grain size fraction of the byproduct at doses corresponding to a molar Mg:P ratio of 1.6.  相似文献   
85.
Pomegranate is an important source of bioactive compounds, such as anthocyanins, other phenolic compounds, and ascorbic acid. In the present work an in vitro availability method has been used to assay the influence of the physiological conditions in the stomach and small intestine. This method enables the study of the release of anthocyanins, vitamin C, and total phenols from the pomegranate juice and their transformations during gastrointestinal digestion. Results have shown that pomegranate phenolic compounds are available during the digestion in a quite high amount (29%). Nevertheless, due to pH, anthocyanins are largely transformed into non-red forms and/or degraded (97%), and similar results are obtained for vitamin C (>95% degradation).  相似文献   
86.
The capacity of inhibition of the mammalian mitochondrial respiratory chain of brevioxime 5a, a natural insecticide compound isolated from Penicillium brevicompactum culture broth, and another 15 analogue compounds, other oximes 5b and 5c; two diastereomeric pyrrolidines 1c' and 1c' '; five pyrrolines 3c', 3c' ' (diastereomers between them), 3a, 3b, and 6; two oxazines 4c' and 4c' ' (also diastereomers between them); and four pyrrol derivatives 7-10, are analyzed in this paper. Compounds 3b, 3c', 3c' ', 4c', 4c' ', 5b, 5c, 6, and 10 were found to be inhibitors of the integrated electron transfer chain (NADH oxidase activity) in beef heart submitochondrial particles (SMP), establishing that all of them except compound 3b and 6 only affected to complex I of the mitochondrial respiratory chain. The most potent product was 5b, with an IC50 of 0.27 microM, similar to the IC50 values of other known complex I inhibitors. The diastereomeric pairs 1c'/1c' ', 3c'/3c' ', 4c'/4c' ', and 5c have not been previously described. Chemical characterization, on the basis of spectral data, is also shown.  相似文献   
87.

• Introduction, Material and Methods  

The genetic structure and diversity of ten natural populations of Juniperus phoenicea L. from the western part of the species range have been studied using random amplified polymorphic DNA (RAPD) markers.  相似文献   
88.
This study reports on three scarlet macaw (Ara macao) reintroduction projects using hand-raised birds in Peru and Costa Rica. The habitats at the release sites ranged from pristine tropical forest to forest fragments in an agricultural matrix. The combined first-year survival was 74% and the annual post first-year survival was 96%. Survival rates were very high despite a wide range in predator communities. Number of birds released explained 70% of the variation in survival with birds from larger releases having higher survival rates. Behavioral evidence suggests that birds established at the site facilitated survival of later releases. Breeding attempts were recorded at all three sites and hand-raised birds with wild mates successfully fledged young in Peru. Supplemental feeding post-release played an important role in keeping the birds near the release site and facilitating social interactions. This work shows that properly socialized hand-raised macaws can survive and breed in the wild but that ex-pets are not good release candidates.  相似文献   
89.
Resveratrol is known as a grapevine secondary metabolite with fungicide activity. Its exogenous application on harvested grapes resulted in the reduction of microbial flora growth, and consequently, prolonged shelf life, without affecting the nutritional quality of the fruit. Resveratrol treatment also resulted in being effective on fruit that normally does not accumulate such metabolites as, for example, tomatoes, apples, avocado pears, and peppers. As a result, all treated fruits maintained their post-harvest quality and health longer than the untreated ones. This study demonstrates the potential use of resveratrol as a natural pesticide to reduce post-harvest fungi development on a broad spectrum of fruit types.  相似文献   
90.
An automated immunosensor for the rapid and sensitive analysis of penicillin type beta-lactam antibiotics has been developed and optimized. An immunogen was prepared by coupling the common structure of the penicillanic beta-lactam antibiotics, i.e., 6-aminopenicillanic acid to keyhole limpet hemocyanin. Polyclonal antibodies raised in rabbits after immunization with this conjugate have been applied for the development of a competitive fluoroimmunoassay (FIA), using a novel fluorescent penicillin {[2S,5R,6R]-3,3-dimethyl-7-oxo-6-[(pyren-1ylacetyl)amino]-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxilic acid, PAAP} as the tracer and penicillin G as the reference antibiotic. Protein A/G covalently bound to an azlactone-activated polymeric support was used for the orientated capture of the antibody-antigen immunocomplexes. Upon desorption from the immunosupport, the emission signal generated by the PAAP-Ab complexes is related to the antibiotic concentration in the sample. The 50% binding inhibition concentration of penicillin G standard curves was at 30 ng mL(-)(1) with a detection limit (10% binding inhibition) of 2.4 ng mL(-)(1) and a dynamic range from 6.0 to 191 ng mL(-)(1) (20-80% binding inhibition) penicillin G. The generic nature of the antiserum was shown by good relative cross-reactivities with penicillin type beta-lactam antibiotics such as amoxicillin (50%), ampicillin (47%), and penicillin V (145%) and a lower response to the isoxazolyl penicillins such as oxacillin, cloxacillin, and dicloxacillin. No cross-reactivity was obtained for cephalosporin type beta-lactam antibiotics (cephapirin), cloramphenicol, or fluoroquinolones (enrofloxacin and ciprofloxacin). The total analysis time was 23 min per determination, and the immunoreactor could be reused for more than 200 cycles without significant loss of activity. The immunosensor has been successfully applied to the direct analysis of penicillin G and amoxicillin in spiked influent and effluent sewage treatment plant water samples with excellent recoveries (mean values for penicillin G and amoxicillin, 99 and 105%, respectively). Results displayed by comparative analysis of the immunosensor with a chromatographic procedure for penicillins showed excellent agreement between both methods.  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