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   807篇
  免费   93篇
林业   44篇
农学   57篇
基础科学   5篇
  153篇
综合类   24篇
农作物   78篇
水产渔业   112篇
畜牧兽医   307篇
园艺   20篇
植物保护   100篇
  2023年   4篇
  2022年   8篇
  2021年   17篇
  2020年   26篇
  2019年   60篇
  2018年   37篇
  2017年   52篇
  2016年   49篇
  2015年   33篇
  2014年   37篇
  2013年   65篇
  2012年   45篇
  2011年   59篇
  2010年   30篇
  2009年   24篇
  2008年   34篇
  2007年   26篇
  2006年   25篇
  2005年   27篇
  2004年   15篇
  2003年   23篇
  2002年   16篇
  2001年   18篇
  2000年   9篇
  1999年   11篇
  1998年   9篇
  1997年   8篇
  1996年   7篇
  1995年   5篇
  1994年   6篇
  1993年   12篇
  1992年   6篇
  1991年   8篇
  1990年   5篇
  1988年   8篇
  1987年   4篇
  1984年   5篇
  1983年   6篇
  1982年   4篇
  1980年   2篇
  1979年   11篇
  1978年   5篇
  1977年   4篇
  1976年   6篇
  1975年   4篇
  1973年   2篇
  1971年   4篇
  1967年   5篇
  1966年   3篇
  1965年   2篇
排序方式: 共有900条查询结果,搜索用时 187 毫秒
51.
The current work is aimed to realizing land and water use efficiency and determining the profitability of precision farming economically and environmentally. The studied area is represented by an experimental pivot irrigation field cultivated with maize in Ismailia province, Egypt. Two field practices were carried out during the successive summer growing seasons (2008 and 2009) to study the response of maize plants single hybrid 10 (S.H.10) to traditional and precision farming practices. Traditional farming (TF) as handled by the farm workers were observed and noted carefully. On the other hand precision farming (PF) practices included field scouting, grid soil sampling, variable rate technology and its applications. After applying PF a dramatic change in management zones was noticed and three management zones (of total four) were merged to be more homogenous representing 84.3% of the pivot irrigation field.Under PF Remote Sensing and Geographic Information System techniques have played a vital role in the variable rate applications that were defined due to management zones requirements. Fertilizers were added in variable rates, so that rationalization of fertilizers saved 23.566 tonnes/experimental pivot area. Natural drainage system was improved by designing vertical holes to break down massive soil layers and to leach excessive salts. Crop water requirements were determined in variable rate according to the actual plant requirements using SEBAL model with the aid of FAO Cropwat model. Irrigation schedule of maize was adopted considering soil water retention, depletion, gross and net irrigation saving an amount of water equal to 93,718 m3 in the pivot irrigation field (153.79 acre). However costs of applying PF were much higher than TF, the economic profitability (returns-costs) achieved remarkable increase of 29.89% as a result of crop yield increment by 1000, 2100, 800 and 200 kg/acre in the management zones 1, 2, 3 and 4, respectively. Finally applying adequate amounts of fertilizers beside water control the environmental hazards was reduced to the acceptable limits.  相似文献   
52.
A proton microprobe capable of focusing proton beams with energies up to 6 million electron volts to a spot size of 2 x 2 square micrometers has been used for chemical analysis of small grains of minerals in lunar samples by proton-induced x-ray emission. The proton microprobe is preferable to the electron microprobe for analyzing trace elements whose concentrations are below the detection limit of the latter and for analyzing objects with numerous major and trace elements with a wide range of atomic numbers. Application of the proton microprobe to biological samples is feasible.  相似文献   
53.
Feline parotid salivary duct sialocele is an uncommon disorder that has been previously reported in association with traumatic rupture of the duct in only two cats. Both cases were successfully treated by proximal duct ligation. We describe the successful surgical treatment of a parotid duct sialocele, secondary to spontaneous salivary duct stenosis, in an adult domestic shorthair cat. The cat was referred for assessment of a recurrent fluid-filled swelling on the left side of the face. Cytology of the aspirated fluid was consistent with serous saliva. The anatomical localisation of the lesion and the nature of the fluid were indicative of parotid gland/duct involvement. Retrograde sialography by parotid duct cannulation was unsuccessful because the left parotid duct opening was stenosed and obstructed by scar tissue. Surgical exploration revealed a parotid salivary duct sialocele, which was completely removed along with the parotid gland without complications.  相似文献   
54.
In order to identify antigens that can help prevent camel tick infestations, three major glycoproteins (GLPs) about 97, 66 and 40 kDa in size were purified from adult and larval Egyptian ticks, Hyalomma (H.) dromedarii, using a single-step purification method with Con-A sepharose. The purified GLPs were evaluated as vaccines against camel tick infestation in rabbits. The rabbits received three intramuscular inoculations of GLPs (20 µg/animal) on days 0, 14, and 28. In the immunoblot analysis, Sera from the immunized rabbits recognized the native GLPs and other proteins from larval and adult H. dromedarii ticks along with those from other tick species such as Rhipicephalus sanguineus but not Ornithodoros moubata. The effects of immunity induced by these GLPs were determined by exposing rabbits to adult H. dromedarii ticks. These results demonstrated that GLP immunization led to a slightly decreased reproductive index and significantly reduced rates of egg hatchability. These results demonstrated that immunization with the purified GLPs can provide protection against infestation by H. dromedarii and some other tick species. Further studies are needed to confirm the effectiveness of immunization with GLPs against other tick species.  相似文献   
55.
56.
An enzyme-linked lectin assay (ELLA) was used to differentiatebetween chromium-stressed and unstressed cells of Escherichia coli EI19. The assay is a modification of the enzyme-linked immunosorbent assay (ELISA) that uses Concanavalin A (Con A) conjugated with peroxidase to detect the carbohydrate moiety of the cell envelope glycoconjugates. The ELLA test shows that Con A binds to stressed bacteria much moreefficiently than it does to unstressed bacteria. Effects of heat,phenol and papain treatments on Con A-binding to chromium-stressed bacteria were also studied. Con A-binding to bacteria was sensitive to heat and phenol treatment, but not to treatment with papain. A potential analytical method for estimating the concentration of certain environmental pollutants is outlined.  相似文献   
57.
Furundu, a meat substitute, is traditionally prepared by cooking the karkade (Hibiscus sabdariffa L.) seed and then fermenting it for 9 days. Physicochemical and functional properties of raw and cooked seed and of furundu ferments were analyzed. Furundu preparation resulted in significant changes in karkade seed major nutrients. Total polyphenols and phytic acid were also reduced. The increase in total acidity and fat acidity coupled with a decrease in pH indicates microbial hydrolysis of the major nutrients; proteins, carbohydrates, and fats. In vitro digestibility of the seed proteins reached the maximum value (82.7%) at the sixth day of fermentation, but thereafter it significantly decreased. The effect of furundu preparation on N solubility profiles and functional properties, such as emulsification and foaming properties and other related parameters, is investigated in water and in 1 M NaCl extracts from defatted flour samples. The results show that cooking followed by fermentation affects proteins solubility in water and 1 M NaCl. The foaming capacity (FC) from the flour of raw seed decreased as a result of cooking. Fermentation for 9 days significantly increased the FC of the cooked seed, restoring the inherent value. Foam from fermented samples collapsed more rapidly during a period of 120 min as compared to the foam from raw and cooked karkade seeds; stability in 1 M NaCl was lower as compared to those in water. In water, the emulsion stability (ES) from the fermented samples was significantly higher than that of the raw seed flour. Addition of 1 M NaCl significantly decreased the ES of the fermented samples.  相似文献   
58.
Intercropping or rotating of P‐efficient crop species which mobilize sparingly soluble P by their root exudates can have beneficial effects on growth and P uptake of P‐inefficient species. We aimed at studying the effect of intercropping or incorporating of crop residues of P‐efficient crops on the components of maize P‐uptake, i.e. the root‐system size and P influx (P‐uptake rate per unit root length). This was studied in 3 pot experiments in a low‐P sandy soil. In the first experiment, maize was intercropped with white lupine, sugar beet or oilseed rape, and with groundnut in the second experiment. In the third experiment, maize was grown after incorporating the crop residues of white lupine, sugar beet or oilseed rape. Maize growth and yield was strongly inhibited when intercropped with white lupine, sugar beet or oilseed rape, probably because of competition for nutrients. But with groundnut as the accompanying species, maize yield was increased by a factor of 3, mainly because of an enhanced P influx. Crop residues of oilseed rape and sugar beet increased the yield of maize by factors 2 and 1.6, respectively, because of a 3 and 2 times higher P uptake as compared to maize grown after maize without incorporation of crop residue. The reason for the higher maize P‐uptake after oilseed rape was an 11 times higher P influx as compared to maize without crop residues, and after sugar beet residues because of an enhanced root growth and a 4 times higher P influx. Lupine residues did not improve maize growth, mainly because of a low P influx, which was even less than that of maize grown without crop residues. The soil solution P concentration and calcium acetate lactate‐extractable P (CAL P) measured in this study did not reflect the P availability as indicated by the plants (P uptake, P influx). This indicates that other mechanisms such as P mobilization in the rhizosphere by root exudates or cell‐wall components were responsible for the increased P availability. These mechanisms need further investigation.  相似文献   
59.
If a great number of rays are fished in the Tropical East Atlantic Ocean for their caudal fins, only a small amount of ray flesh is processed. Among them, three species of rays, Dasyatis marmorata, Rhinobatos cemiculus, and Rhinoptera marginata, from the Mauritanian coast have been investigated for the fatty acid composition of their lipids. Gas chromatography and gas chromatography-mass spectrometry allowed identification of 50 molecules from muscles, livers, and gonads of these fishes. Principal component analysis, starting from >50 samples, reveals significant differences in various fatty acid distributions, related to the species and sex of the sampled fish. Some of them are preferentially present in one sex or in both species, whereas the occurrence of others characterizes the male and female of one or two species. The results show that rays are potential resources of polyunsaturated fatty acids (PUFA) and should be used in the diet of local populations. The lipidic fractions contained a high amount of PUFA (up to 30% of the total), mainly composed of docosa-4,7,10,13,16,19-hexaenoic acid, eicosa-5,8,11,14-tetraenoic acid, and eicosa-5,8,11,14,17-pentaenoic acid.  相似文献   
60.
Summary Chronic, undulatingTheileria annulata infection was diagnosed as the cause of severely depressed milk yields in a herd of 44 Friesian cows in Egypt. The herd was divided at random into two groups of 22; one group was injected intramuscularly with a single dose of the experimental antitheilerial drug, buparvaquone, while the other remained untreated. Over the subsequent seven weeks milk yield in the treated group increased to double that of the untreated group (P<0.05). Pyrexia was controlled within two days of injection of buparvaquone and piroplasm parasitaemia was eliminated in one week. It is suggested that treatment of dairy cattle chronically infected withT. annulata using buparvaquone may have the dual beneficial effect of reducing the pathogenic effects of theileriosis, thereby permitting restoration of an impaired immune system, thus increasing resistance to other infections. If a similar effect could be produced inBos indicus cattle inT. annulata endemic areas, treatment of indigenous cattle with buparvaquone could be a useful alternative to the introduction ofBos taurus blood as a way of boosting milk production.
Efecto Sobre La Produccion De Leche Del Tratamiento De La Theileriosis Cronica Con Buparvaquone
Resumen Se diagnosticó infección crónica ondulate deTheileria annulata, en un hato de 44 vacas Friesian en Egipto; la causa fue, la caida severa de la producción láctea. Se dividió el hato al azár, en dos grupos de 22 vacas cada uno; un grupo se inyectó via intramuscular, con una dosis única de la droga experimental buparvaquone y el otro no se trató. Durante las siete semanas subsiguientes, la producción láctea aumentó el doble en el grupo tratado, en relación con el grupo sin tratar (P<0.05). La pirexia fue controlada, dentro de los dos primeros dias después de la inyección de buparvaquone, y la parasitemia por piroplasmas se eliminó en una semana. Se sugiere, que el tratamiento con buparvaquone del genado de leche infectado crónicamente conT. annulata, podría tener doble efecto benéfico, al reducir el efecto patógeno de la theileriosis, permitiendo la restauración del sistema inmunológico, incrementando así la resistencia a otras infecciones. Si un efecto similar se produjera en ganadoBos indicus, en áreas endémicas deT. annulata, el tratamiento del ganado nativo con buparvaquone, podría convertirse en una alternativa a la introducción de sangreBos taurus, para incrementar la producción láctea.

Effet Du Traitement De La Theileriose Chronique Par La Buparvaquone Sur Les Rendements Laitiers
Résumé L'infection chronique et à rechutes àTheileria annulata a été diagnostiquée comme étant la cause de rendements laitiers fortement déprimés dans un troupeau de 44 vaches frisonnes en Egypte. Le troupeau fut partagé, au hasard, en deux groupes de 22; un groupe a reçu par voie intramusculaire, une dose unique d'un médicament antitheileriose expériemental, la buparvaquone, tandis que l'autre n'était pas traité. Pendant les sept semaines suivantes, le rendement laitier du groupe traité a doublé par rapport à celui du groupe non triaté (P<0.05). L'hyperthermie a été contrôlée dans les deux jours suivant l'injection de buparvaquone, et la parantémie à piroplasme éliminée en une semaine. Il est suggéré que le traitement du bétail laitier chroniquement infecté parT. annulata à l'aide de la buparvaquone peut avoir le double effet bénéfique de réduire les effects pathologiques de la theilériose, permettant ainsi la restauration d'un système immunitaire affaibli, ce qui augmente la résistance aux autres infections. Si un effet similaire pouvait être produit chez le bétailBos indicus des régions à endémicitéT annulata, le traitement du bétail indigène avec la buparvaquone pourrait être une alternative utile à l'introduction du sangBos taurus dans le but de stimuler la production laitière.
  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