全文获取类型
收费全文 | 17036篇 |
免费 | 898篇 |
国内免费 | 17篇 |
专业分类
林业 | 828篇 |
农学 | 558篇 |
基础科学 | 122篇 |
2505篇 | |
综合类 | 2664篇 |
农作物 | 911篇 |
水产渔业 | 950篇 |
畜牧兽医 | 8308篇 |
园艺 | 197篇 |
植物保护 | 908篇 |
出版年
2020年 | 161篇 |
2019年 | 182篇 |
2018年 | 310篇 |
2017年 | 365篇 |
2016年 | 261篇 |
2015年 | 198篇 |
2014年 | 316篇 |
2013年 | 665篇 |
2012年 | 496篇 |
2011年 | 620篇 |
2010年 | 428篇 |
2009年 | 410篇 |
2008年 | 628篇 |
2007年 | 552篇 |
2006年 | 513篇 |
2005年 | 453篇 |
2004年 | 420篇 |
2003年 | 429篇 |
2002年 | 369篇 |
2001年 | 486篇 |
2000年 | 475篇 |
1999年 | 373篇 |
1998年 | 180篇 |
1997年 | 201篇 |
1996年 | 156篇 |
1995年 | 192篇 |
1993年 | 164篇 |
1992年 | 280篇 |
1991年 | 313篇 |
1990年 | 307篇 |
1989年 | 312篇 |
1988年 | 289篇 |
1987年 | 246篇 |
1986年 | 295篇 |
1985年 | 253篇 |
1984年 | 209篇 |
1983年 | 207篇 |
1979年 | 250篇 |
1978年 | 165篇 |
1977年 | 155篇 |
1975年 | 171篇 |
1974年 | 234篇 |
1973年 | 215篇 |
1972年 | 251篇 |
1971年 | 230篇 |
1970年 | 203篇 |
1969年 | 192篇 |
1968年 | 158篇 |
1967年 | 160篇 |
1966年 | 161篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Kasková A Ondrasovicová O Vargová M Ondrasovic M Venglovský J 《Zoonoses and public health》2007,54(3-4):125-130
Hygiene and sanitation play a major role in any effective disease control programme for poultry production and processing premises. Various deficiencies in disinfection may induce that chains of infections are not broken from one stock to another. The present study investigated the efficacy of disinfection on a broiler farm and in a plant processing poultry from the investigated farm. Besides inspection of disinfection, the influence of contamination on broiler carcasses and consequences of this contamination on sanitation of the processing lines were studied. Swabs from surfaces coming into contact with the handled raw material were taken and evaluated. The results obtained by a standard microbiological swab method were evaluated and compared with an ATP-bioluminescence method. The investigations included determination of total counts of microorganisms, coliform bacteria and moulds. When employing the standard plate-count method, the total counts of microorganisms (TCM) reached <1, 1-100 and >100 CFU in 0, 12 and 88% swabs on poultry farm and in 22%, 36% and 42% swabs in the processing plant, respectively. The bioluminescence method was used only in the processing plant and contamination corresponding to <100, 100-300 and >300 relative light units (RLU) was detected in 80%, 10% and 10% swabs respectively. 相似文献
132.
Deschamps JY Roux FA Fantinato M Albaric O 《The Journal of small animal practice》2007,48(12):699-701
A ureteral sarcoma was diagnosed in a nine-year-old Weimaraner dog with gross haematuria, severe unilateral hydronephrosis, and hydroureter. Treatment consisted of unilateral nephrectomy and ureterectomy. This case was compared with 14 other ureteral tumours reported in the veterinary literature. Only three previous reports concerned a malignant ureteral tumour. Urinary tract neoplasms mainly involve the bladder and the kidney, and more rarely the urethra. The purpose of this paper is to report a rare case of malignant ureteral tumour in a dog. 相似文献
133.
Scacchia M Sacchini F Filipponi G Luciani M Lelli R Tjipura-Zaire G Di Provvido A Shiningwane A Ndiipanda F Pini A Caporale V Hübschle OJ 《The Onderstepoort journal of veterinary research》2007,74(3):251-263
Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides var. mycoides small colony (MmmSC), is one of the most important diseases of cattle in Africa. The role of innate or acquired cell mediated and humoral immunity in conferring protection against MmmSC infection has not yet been elucidated. On the other hand, the pathological lesions caused by the aetiological agent have been considered indicative of an immunopathological process. In this study ten na?ve cattle were exposed to in-contact infection with animals infected by intubation with a strain of MmmSC. Clinical signs, antibody response, IFNgamma release and pathological changes at necropsy were analysed and compared with the events following in-contact infection of an equal number of animals kept under daily treatment with cyclosporine for the entire observation period of 84 days. Cyclosporine is a suppressor of the immune response related to the T-cell system. Under the conditions of the experiment, cyclosporine appeared to condition the pathogenesis of CBPP by delaying the events that follow infection, bringing further support to the possibility that the immune response may have an impact on the disease outcome. 相似文献
134.
The aim of this trial was to assess the effect that calcium gluconate priming of 468 broilers has on the antibacterial activity of a standard dose of enrofloxacin. Hence, a series of oral pharmacokinetic studies were carried out in four groups of broilers medicated individually through an oral cannula as follows: group A, medicated only with enrofloxacin 10mg/kg; group B, receiving immediately one after the other, calcium gluconate (200mg/kg) and enrofloxacin 10mg/kg; group C, dosed first with calcium gluconate (200mg/kg) and 1h later enrofloxacin (10mg/kg); and group D, dosed first with calcium gluconate (200mg/kg) and 2h later enrofloxacin (10mg/kg). Broilers were bled at different times after the dose of enrofloxacin and antibacterial activity, measured as concentration of enrofloxacin, was measured by an agar diffusion assay. Results revealed that group D the greatest values of maximum serum concentration (Cs(max)), area under the concentration vs. time curve (AUC) and area under the moment curve (AUMC). These values were statistically higher than the corresponding ones derived from groups A, B and C (P<0.05). Taking Cs(max) and AUC values of group A as reference baseline, an increase of 24% and 50%, respectively, was obtained in group D. Group B had the lowest Cs(max), AUC, AUMC and elimination half life (T(1/2)beta) and these values were statistically different from groups A, C and D (P<0.05). The T(1/2)beta was statistically longer in groups C and D as compared with A and B, and the former groups were also different between each other (P<0.05). These results show that if calcium gluconate is first dosed to broilers and 2h later enrofloxacin is administered (as in group D), a more pronounced antibacterial activity of enrofloxacin can be obtained. A challenge of this sequential dosing scheme in a field trial may reveal its clinical value. 相似文献
135.
136.
Summary A field experiment was carried out for two years on a grumusol (Typic chromoxerert) soil at Merhavya, Israel, to study the influence of different concentrations of N in soil solution on the growth and yield of drip-irrigated cotton (Gossypium hirsutum L.) var. Acala SJ-2. The N-concentrations in the soil solution used were: 0, 12.5, 25, 50, 75 and 100 ppm N. The soil was analyzed for moisture and NO3-N every two weeks and the concentration of NO3-N in the soil solution was calculated. When the NO3-N concentration was less than the above-mentioned levels, N-fertilizer was added in the irrigation water to match these concentrations. If the tested soils showed higher concentrations, no N fertilizer was applied.The maximum yields of seed cotton obtained were 6.3 ton h–1 in the first year, and 5.7 ton ha–1 in the second year. Concentrations below 25 ppm N in the soil solution reduced the cotton seed and lint yields, but concentrations of 50 ppm N and above did not increase the yields and sometimes even decreased them. Application of more nitrogen caused excessive vegetative growth and less seed-cotton and lint.The results show that soil nitrate analysis during the cotton season can be used to monitor the N supplied by drip irrigation.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1418-E, 1985 series 相似文献
137.
Summary An investigation was made of the irrigation requirements of cotton grown in a sub-humid environment with significant but highly variable rainfall. In the first year of the study, no additional yield benefits accrued to subsequent irrigations following a pre-emergent irrigation due to above average rainfall (550 mm) throughout the growing season. In the second year a similar rainfall amount (502 mm) fell but significant yield increases to irrigation resulted due to the uneven distribution of the rainfall. The main effect was associated with later rains which influenced the number of bolls set. The maximum amount of water extracted by cotton from a deep grey cracking clay was 178 mm. It was found that 70% of this amount could be depleted before irrigation without loss of yield. Crop evapotranspiration varied from 607 mm with no irrigation after emergence to 775 mm following three irrigations. Irrigation was associated with significant losses from rainfall runoff. Too frequent irrigation creates a risk that soil will be too wet to permit utilisation of natural rainfall. Therefore, the use of soil water information to maximise the interval between irrigation is proposed as a necessary basis for efficient irrigation management. 相似文献
138.
Natalia V. Krylova Anna O. Kravchenko Olga V. Iunikhina Anastasia B. Pott Galina N. Likhatskaya Aleksandra V. Volodko Tatyana S. Zaporozhets Mikhail Y. Shchelkanov Irina M. Yermak 《Marine drugs》2022,20(1)
The structural diversity and unique physicochemical properties of sulphated polysaccharides of red algae carrageenans (CRGs), to a great extent, determine the wide range of their antiviral properties. This work aimed to compare the antiviral activities of different structural types of CRGs: against herpes simplex virus type 1 (HSV-1) and enterovirus (ECHO-1). We found that CRGs significantly increased the resistance of Vero cells to virus infection (preventive effect), directly affected virus particles (virucidal effect), inhibited the attachment and penetration of virus to cells, and were more effective against HSV-1. CRG1 showed the highest virucidal effect on HSV-1 particles with a selective index (SI) of 100. CRG2 exhibited the highest antiviral activity by inhibiting HSV-1 and ECHO-1 plaque formation, with a SI of 110 and 59, respectively, when it was added before virus infection. CRG2 also significantly reduced the attachment of HSV-1 and ECHO-1 to cells compared to other CRGs. It was shown by molecular docking that tetrasaccharides—CRGs are able to bind with the HSV-1 surface glycoprotein, gD, to prevent virus–cell interactions. The revealed differences in the effect of CRGs on different stages of the lifecycle of the viruses are apparently related to the structural features of the investigated compounds. 相似文献
139.
140.
Valentina Gonzlez María Jos Vargas-Straube Walter O. Beys-da-Silva Luclia Santi Pedro Valencia Fabrizio Beltrametti Beatriz Cmara 《Marine drugs》2020,18(11)
Marine actinobacteria are viewed as a promising source of enzymes with potential technological applications. They contribute to the turnover of complex biopolymers, such as pectin, lignocellulose, chitin, and keratin, being able to secrete a wide variety of extracellular enzymes. Among these, keratinases are a valuable alternative for recycling keratin-rich waste, which is generated in large quantities by the poultry industry. In this work, we explored the biocatalytic potential of 75 marine-derived actinobacterial strains, focusing mainly on the search for keratinases. A major part of the strains secreted industrially important enzymes, such as proteases, lipases, cellulases, amylases, and keratinases. Among these, we identified two streptomycete strains that presented great potential for recycling keratin wastes—Streptomyces sp. CHA1 and Streptomyces sp. G11C. Substrate concentration, incubation temperature, and, to a lesser extent, inoculum size were found to be important parameters that influenced the production of keratinolytic enzymes in both strains. In addition, proteomic analysis of culture broths from Streptomyces sp. G11C on turkey feathers showed a high abundance and diversity of peptidases, belonging mainly to the serine and metallo-superfamilies. Two proteases from families S08 and M06 were highly expressed. These results contributed to elucidate the mechanism of keratin degradation mediated by streptomycetes. 相似文献