全文获取类型
收费全文 | 486篇 |
免费 | 54篇 |
专业分类
林业 | 36篇 |
农学 | 6篇 |
基础科学 | 2篇 |
106篇 | |
综合类 | 22篇 |
农作物 | 22篇 |
水产渔业 | 32篇 |
畜牧兽医 | 260篇 |
园艺 | 4篇 |
植物保护 | 50篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 18篇 |
2018年 | 25篇 |
2017年 | 31篇 |
2016年 | 26篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 25篇 |
2012年 | 35篇 |
2011年 | 33篇 |
2010年 | 16篇 |
2009年 | 9篇 |
2008年 | 32篇 |
2007年 | 26篇 |
2006年 | 32篇 |
2005年 | 21篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1973年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有540条查询结果,搜索用时 0 毫秒
441.
442.
Silva SR Afonso JJ Santos VA Monteiro A Guedes CM Azevedo JM Dias-da-Silva A 《Journal of animal science》2006,84(12):3433-3439
Ultrasonic measurements were taken on 46 sheep using a real-time ultrasound machine equipped with 2 probes (5 and 7.5 MHz). Measurements of subcutaneous fat thickness (SC) and muscle LM depth (MD) and area (MA) were taken at 2 locations: over the 13th thoracic vertebra (SC13, MD13, and MA13, respectively) and at the interval between the third and fourth lumbar vertebrae (SC34, MD34, and MA34, respectively). Fat thickness was also measured over the third sternebra of the sternum. The relationship between carcass and in vivo ultrasound measurements was high for all the measurements (r(2) between 0.54 and 0.96, P < 0.01). Concerning MD and SC, the 7.5 MHz probe estimates were consistently more precise than the 5-MHz estimates (r(2) increased between 0.09 and 0.13), but the reverse occurred with the MA estimates, although to a lesser extent. Estimates of carcass composition for muscle, subcutaneous fat, intermuscular fat, internal fat, and total fat based on BW explained a large amount of variation in muscle (87%), subcutaneous fat (85%), intermuscular fat (79%), internal fat (74%), and total fat (87%). In most cases (55 of 70) the introduction of one ultrasound measurement in addition to BW in the multiple regression equations further improved the explanation of variation for weight of carcass tissues, internal fat, and total fat. For carcass muscle estimation, the ultrasound measurements of muscle provided an increase of r(2) between 0.05 and 0.10 (P < 0.01). The SC13 and SC34 gave the best improvements in estimating subcutaneous fat, intermuscular fat, internal fat, and total fat (r(2) increased between 0.05 and 0.17; P < 0.01). Prediction of the proportions of the carcass components (internal and total fat from BW) was clearly lower than the prediction of the absolute amounts of these traits. Inclusion of one or more ultrasound measurements in addition to BW increased the predictive ability of the equations. Both probes were useful to estimate carcass muscle depth and area and fat depth, but the 7.5-MHz probe showed a greater ability to estimate depth. For all traits, the stepwise procedure demonstrated that the best fit was obtained with BW and one or more ultrasound measurement with the 7.5-MHz probe. 相似文献
443.
Parra A García A Inglis NF Tato A Alonso JM Hermoso de Mendoza M Hermoso de Mendoza J Larrasa J 《Research in veterinary science》2006,80(2):140-146
Recreational hunting of indigenous wild artiodactyls has been one of the most lucrative and rapidly growing industries in Western Spain over the last five years. In the absence of careful ecological management, one consequence of the commercial exploitation of this natural resource has been the appearance of outbreaks of infectious disease; most notably bovine tuberculosis. From the outset of the study in 1997, we have observed a steady increase in prevalence of Mycobacterium bovis (M. bovis) in both species reaching 1.74 (+/-0.17) in deer in 2002 and 2.32 (+/-0.24) in wild boar. The latter species seems to be most severely affected with pulmonary lesions appearing more chronic than those observed in deer. In this study, we describe the epidemiology of M. bovis in European wild boar (Sus scrofa) and Iberian red deer (Cervus elaphus hispanicus) in Extremadura (W. Spain); a region where there are large areas of natural habitat for these species. 相似文献
444.
Chlamydophila psittaci (C. psittaci) infection was evaluated in 77 free-living nestlings of Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil. Tracheal and cloacal swab samples from 32 wild parrot and 45 macaw nestlings were submitted to semi-nested PCR, while serum samples were submitted to complement fixation test (CFT). Although all 32 Amazon parrot serum samples were negative by CFT, cloacal swabs from two birds were positive for Chlamydophila DNA by semi-nested PCR (6.3%); these positive birds were 32 and 45 days old. In macaws, tracheal and cloacal swabs were positive in 8.9% and 26.7% of the samples, respectively. Complement-fixing antibodies were detected in 4.8% of the macaw nestlings; macaw nestlings with positive findings were between 33 and 88 days old. These results indicate widespread dissemination of this pathogen in the two evaluated psittacine populations. No birds had clinical signs suggestive of chlamydiosis. To the best of our knowledge, this is the first report on C. psittaci in free-living Blue-fronted Amazon parrots and Hyacinth macaws in Brazil. 相似文献
445.
Alonso JM 《Science (New York, N.Y.)》2006,312(5780):1604-1605
446.
Carmona M Zalacain A Sánchez AM Novella JL Alonso GL 《Journal of agricultural and food chemistry》2006,54(3):973-979
Crocetin esters present in saffron (Crocus sativus L.) stigmas and in Gardenia jasminoides Ellis fruit are the compounds responsible for their color. Of the fifteen crocetin esters identified in this study, five new compounds were tentatively identified: trans and cis isomers of crocetin (beta-D-triglucoside)-(beta-D-gentibiosyl) ester, trans and cis isomers of crocetin (beta-D-neapolitanose)-(beta-D-glucosyl) ester, and cis crocetin (beta-D-neapolitanose)-(beta-D-gentibiosyl) ester. The most relevant differences between both species were a low content of the trans crocetin (beta-D-glucosyl)-(beta-D-gentibiosyl) ester, the absence of trans crocetin di-(beta-D-glucosyl) ester in gardenia, and its higher content of trans crocetin (beta-D-gentibiosyl) ester and cis crocetin di-(beta-D-gentibiosyl) ester. With the same chromatographic method it was possible to identify, in a single run, ten glycosidic compounds in saffron extracts with a UV/vis pattern similar to that of picrocrocin; among them, 5-hydroxy-7,7-dimethyl-4,5,6,7-tetrahydro-3H-isobenzofuranone 5-O-beta-D-gentibioside and 4-hydroxymethyl-3,5,5-trimethyl-cyclohexen-2-one 4-O-beta-D-gentibioside were tentatively identified for the first time in saffron. Of these ten glycosides, only the O-beta-D-gentibiosyl ester of 2-methyl-6-oxo-2,4-hepta-2,4-dienoic acid was found in gardenia samples, but it was possible to identify the iridoid glycoside, geniposide. 相似文献
447.
Vegas R Luque S Alvarez JR Alonso JL Domínguez H Parajó JC 《Journal of agricultural and food chemistry》2006,54(15):5430-5436
Liquors from rice husk autohydrolyis, containing xylooligosaccharides, other saccharides, and nonsaccharide compounds, were subjected to two selected processing schemes to increase the proportion of substituted xylooligosaccharides in refined liquors. Nanofiltration through a ceramic membrane with a molecular mass cutoff of 1000 Da allowed simultaneous concentration and purification; this latter derived from the preferential removal of monosaccharides and nonsaccharide compounds. When liquors were nanofiltered to achieve a volume reduction factor of 5 operating at a transmembrane pressure of 14 bar, 58.6% of the nonsaccharide components and 20.9-46.9% of monosaccharides were kept in retentate, in comparison with 92% of xylooligosaccharides and glucooligosaccharides. When nanofiltered liquors were subjected to double ion-exchange processing, a final product with a nonsaccharide content near 9 kg/100 kg of nonvolatile components was obtained at a yield of 10.90 kg/100 kg oven dry rice husks. Alternatively, when nanofiltered liquors were subjected to ethyl acetate extraction and further double ion-exchange processing, a purified product with a nonsaccharide content of 5.66 kg/100 kg of nonvolatile components was obtained at a yield of 9.94 kg/100 kg oven dry rice husks. The nonsaccharide components remaining in the final concentrate were mainly made up of phenolic and nitrogen-containing compounds. 相似文献
448.
Diet has an important role in the prevention and treatment of hypertension. In early epidemiological studies, conducted mainly in the USA, monounsaturated fatty acids showed a deleterious association with blood pressure or no relationship at all. However, more recent studies, conducted in Mediterranean countries, have shed new light on this issue. In the present review we summarise the main results of epidemiological studies and feeding trials, and explain the possible mechanisms through which monounsaturated fatty acids, and specifically olive oil as the major dietary source of this type of fat in Mediterranean countries, could exert a favourable effect on blood pressure. 相似文献
449.
Identification and characterization of proteases from skin mucus of tambacu,a Neotropical hybrid fish 总被引:1,自引:0,他引:1
C. M. C. Salles P. Gagliano S. A. T. Leitão J. B. Salles H. L. M. Guedes V. P. F. Cassano S. Giovanni De-Simone 《Fish physiology and biochemistry》2007,33(2):173-179
Skin secretions of fishes constitute a rich source of proteins with a broad spectrum of antimicrobial properties. We report
here the characterization of proteases from skin mucus of tambacu, an economically important Neotropical hybrid fish. The
effects of pH on the proteolytic activities of the mucus acting on various substracts – hemoglobin, casein, bovine serum albumin
(BSA) and ovalbumin (OVA) – were tested. Optimal pH values for protease activity on hemoglobin were 4.5 and 8.5, on casein,
8.5, on BSA, 5.0 and 7.5, and on ovalbumin, 4.5 and 6.5. The proteolytic activity was inhibited on all of these substrates
in the presence of specific inhibitors: caseinolytic activity was inhibited by inhibitors of serine and metalloproteases;
hemoglobinolytic activity was inhibited by serine, aspartic and metalloproteases inhibitors; albuminolytic activity on BSA
was inhibited by serine and aspartic proteases inhibitors, and on ovalbumin, by cysteine and aspartic proteases inhibitors.
Gelatin zymography revealed that the skin mucus of tambacu consisted primarily of serine and metalloproteases. Hemoglobin
zymography showed one proteolytic band inhibited by EDTA, whereas casein zymography showed two proteases inhibited by serine
proteases inhibitors. We were able to identify all classes of proteases in the mucus from the skin of tambacu. These, and
these results suggest that the proteolytic activities of the skin mucus of fish may play an important role in the defense
against microorganisms and ectoparasites. 相似文献
450.