全文获取类型
收费全文 | 2008篇 |
免费 | 97篇 |
专业分类
林业 | 60篇 |
农学 | 60篇 |
基础科学 | 3篇 |
341篇 | |
综合类 | 282篇 |
农作物 | 255篇 |
水产渔业 | 149篇 |
畜牧兽医 | 821篇 |
园艺 | 26篇 |
植物保护 | 108篇 |
出版年
2022年 | 19篇 |
2021年 | 38篇 |
2020年 | 24篇 |
2019年 | 28篇 |
2018年 | 50篇 |
2017年 | 44篇 |
2016年 | 45篇 |
2015年 | 44篇 |
2014年 | 59篇 |
2013年 | 93篇 |
2012年 | 105篇 |
2011年 | 139篇 |
2010年 | 62篇 |
2009年 | 55篇 |
2008年 | 100篇 |
2007年 | 108篇 |
2006年 | 70篇 |
2005年 | 78篇 |
2004年 | 73篇 |
2003年 | 73篇 |
2002年 | 51篇 |
2001年 | 36篇 |
2000年 | 44篇 |
1999年 | 37篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1994年 | 14篇 |
1992年 | 23篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 27篇 |
1988年 | 20篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 17篇 |
1973年 | 23篇 |
1972年 | 18篇 |
1971年 | 14篇 |
1970年 | 18篇 |
1969年 | 19篇 |
1968年 | 12篇 |
1966年 | 11篇 |
排序方式: 共有2105条查询结果,搜索用时 31 毫秒
991.
R F Berendt M A Schneider H W Young F R Frola 《American journal of veterinary research》1979,40(9):1231-1235
The methods of aerosol administration of kanamycin and IM injection of the antibiotic were compared for their protection of mice and squirrel monkeys against Klebsiella pneumoniae respiratory tract infection. Mice exposed to LD90 of K pneumoniae at 0.5, 4, 24, 48 and 72 hours after they were treated with aerosol of kanamycin (27 mg/kg of body weight) were significantly better protected at all exposure times than were mice given the antibiotic (450 mg/kg) by IM injection. Squirrel monkeys given the aerosol at dose level of 11.25 mg/kg were completely protected against K pneumoniae exposure at 6 and 24 hours, whereas only one of eight monkeys treated with the same dose given IM survived the exposure at 6 hours and none survived at 24 hours. Antibiotic clearance curves indicated that kanamycin remained in the lungs at higher concentrations and for longer periods after aerosol treatment than after IM treatment. 相似文献
992.
R D Keenan D J Young C M Tier A D Jones J Underdown 《Journal of agricultural and food chemistry》2001,49(7):3394-3402
The pressure-induced gelation of concentrated skimmed milk and milk-sugar mixtures was studied to discover the main components responsible for gelation. The major protein component responsible for gelation is micellar casein. Gelation occurs at similar pressures to casein micelle disintegration in dilute milk, and both can be prevented by inclusion of excess calcium chloride. Transmission electron micrographs show that the protein network is formed from particles with diameters approximately an order of magnitude smaller than those of intact casein micelles. Gelation occurs on decompression and is found to be baroreversible. Concentrations of sugar up to 30% reduce the critical concentration of casein required for gelation, but higher sugar concentrations inhibit gelation. A mechanism of gelation based on the aggregation of casein submicelles formed by pressure-induced disintegration of casein micelles is proposed. Observations on the effect of sucrose on gelation are discussed in terms of the influence of sugars on the solvent quality in aqueous casein systems. 相似文献
993.
Anthony Sowers Shawn P. Young J. Jeffery Isely Craig L. Browdy Joseph R. Tomasso Jr 《Journal of the World Aquaculture Society》2004,35(4):445-451
The uptake, depuration and toxicity of environmental nitrite was characterized in Litopenaeus vannamei exposed in water containing low concentrations of artificial sea salt or mixed salts. In 2 g/L artificial sea salts, nitrite was concentrated in the hemolymph in a dose-dependent and rapid manner (steady-state in about 2 d). When exposed to nitrite in 2 g/L artificial sea salts for 4 d and then moved to a similar environment without added nitrite, complete depuration occurred within a day. Increasing salinity up to 10 g/L decreased uptake of environmental nitrite. Nitrite uptake in environments containing 2 g/L mixed salts (combination of sodium, potassium, calcium and magnesium chlorides) was similar to or lower than rates in 2 g/L artificial sea salt. Toxicity was inversely related to total dissolved salt and chloride concentrations and was highest in 2 g/L artificial sea salt (96-h medial lethal concentration = 8.4 mg/L nitrite-N). Animals that molted during the experiments did not appear to be more susceptible to nitrite than animals that did not molt. The shallow slope of the curve describing the relationship between toxicity and salinity suggests that management of nitrite toxicity in low-salinity shrimp ponds by addition of more salts may not be practical. 相似文献
994.
Urine Cortisol:Creatinine Ratio in Healthy and Sick Cats 总被引:1,自引:0,他引:1
Carolyn J. Henry Terrence P. Clark Diane W. Young Joseph S. Spano 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1996,10(3):123-126
Urine cortisokcreatinine ratios (UCCR) were determined from single urine samples obtained by cystocentesis in 47 cats allotted into 2 groups: 31 healthy cats and 16 sick, hospitalized cats with assorted clinical illnesses. The mean (± standard deviation) UCCR for healthy cats was 5.9 ± 7.0 (median, 3.2; range, 0.6 to 27.8). Age or gonadal status had no significant effect on the magnitude of UCCR within this group. However, sick cats had significantly higher UCCR (P = .002) when compared with healthy cats. The mean UCCR for sick cats was 19.6 ± 19.2 (median, 14.8; range, 1.7 to 75.1). This report establishes a reference range for UCCR in 31 normal cats and provides evidence that health status affects UCCR in cats. J Vet Intern Med 1996;10:123–126. Copyright © 1996 by the American College of Veterinary Internal Medicine . 相似文献
995.
996.
Efficacy and toxicity of tamoxifen citrate for prevention and termination of pregnancy in bitches 总被引:2,自引:0,他引:2
Five groups of bitches were given tamoxifen citrate (1 mg/kg of body weight) orally twice daily for 10 days. Drug administration commenced during late proestrus, day 4 of estrus, day 2 of diestrus, day 15 of diestrus, or day 30 of diestrus (n = 4/group). Nineteen of the bitches accepted natural mating by 1 or more of 3 stud dogs of known fertility (1 bitch did not). Twenty days after cessation of drug administration, ovarian, uterine, and hepatic specimens were obtained from each bitch in 4 of the groups. Pregnancy proceeded to natural termination in bitches of the remaining group (diestrous day 30). Pregnancy was not detected in any bitch of the proestrus, estrous, or early diestrous groups. Of 4 bitches of each of the remaining groups (diestrous day 15 and diestrous day 30), 2 aborted fetuses and/or resorbed placental remnants; the other 2 bitches in each of these groups had normal-appearing fetuses (diestrous day-15 group) or clinically normal pups (diestrous day-30 group). Of the 20 bitches given tamoxifen citrate, 5 developed endometritis with or without pyometra, and 4 of these had ovarian cysts. Although tamoxifen citrate is effective for preventing or terminating pregnancy in the bitch, the regimen used in the study reported here was associated with high frequency of pathologic changes in the reproductive tract. 相似文献
997.
Park HB Jung CH Lee YM Hill AJ Pas SJ Mudie ST Van Wagner E Freeman BD Cookson DJ 《Science (New York, N.Y.)》2007,318(5848):254-258
Within a polymer film, free-volume elements such as pores and channels typically have a wide range of sizes and topologies. This broad range of free-volume element sizes compromises a polymer's ability to perform molecular separations. We demonstrated free-volume structures in dense vitreous polymers that enable outstanding molecular and ionic transport and separation performance that surpasses the limits of conventional polymers. The unusual microstructure in these materials can be systematically tailored by thermally driven segment rearrangement. Free-volume topologies can be tailored by controlling the degree of rearrangement, flexibility of the original chain, and judicious inclusion of small templating molecules. This rational tailoring of free-volume element architecture provides a route for preparing high-performance polymers for molecular-scale separations. 相似文献
998.
999.
1000.
Young DT Berthelier JJ Blanc M Burch JL Bolton S Coates AJ Crary FJ Goldstein R Grande M Hill TW Johnson RE Baragiola RA Kelha V McComas DJ Mursula K Sittler EC Svenes KR Szegö K Tanskanen P Thomsen MF Bakshi S Barraclough BL Bebesi Z Delapp D Dunlop MW Gosling JT Furman JD Gilbert LK Glenn D Holmlund C Illiano JM Lewis GR Linder DR Maurice S McAndrews HJ Narheim BT Pallier E Reisenfeld D Rymer AM Smith HT Tokar RL Vilppola J Zinsmeyer C 《Science (New York, N.Y.)》2005,307(5713):1262-1266
During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where RS is the radial distance from the center of Saturn), whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with approximately 3% N+. Over the A and B rings, we found an ionosphere in which O2+ and O+ are dominant, which suggests the possible existence of a layer of O2 gas similar to the atmospheres of Europa and Ganymede. 相似文献