全文获取类型
收费全文 | 496篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
林业 | 5篇 |
农学 | 6篇 |
基础科学 | 2篇 |
47篇 | |
综合类 | 140篇 |
农作物 | 5篇 |
水产渔业 | 29篇 |
畜牧兽医 | 161篇 |
园艺 | 1篇 |
植物保护 | 105篇 |
出版年
2021年 | 5篇 |
2020年 | 6篇 |
2015年 | 7篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 5篇 |
2010年 | 17篇 |
2009年 | 11篇 |
2008年 | 12篇 |
2007年 | 9篇 |
2006年 | 17篇 |
2004年 | 6篇 |
2003年 | 5篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1961年 | 4篇 |
1959年 | 6篇 |
1958年 | 9篇 |
1957年 | 8篇 |
1956年 | 7篇 |
1955年 | 3篇 |
1954年 | 4篇 |
1948年 | 6篇 |
1947年 | 4篇 |
1946年 | 3篇 |
1945年 | 4篇 |
1943年 | 4篇 |
1941年 | 4篇 |
1940年 | 6篇 |
排序方式: 共有501条查询结果,搜索用时 500 毫秒
61.
62.
D.C. GOODDY P. SHAND D.G. KINNIBURGH W.H. VAN RIEMSDIJK 《European Journal of Soil Science》1995,46(2):265-285
A total of 48 elements was detected in the soil solutions centrifuged from two acid sandy (humus-iron podzol) profiles from southern England. Concentrations ranged from mm for the major ions to mm for trace metals such as U and the rare earth elements. Field-based solid/solution partition coefficients, Kd, were determined by calculating the ratio of the amount of an element extracted by 0.43 m HNO3 or a neutral salt (0.01 m CaCl2 or 0.1 m Ba(NO3)2) to the concentration in the soil solution. These partition coefficients did not show the expected trend in selectivity. For example, Cd consistently had one of the highest Kd values, higher even than Cu. This was thought to be due in part to the nature of the Kd which reflects a balance between binding to the soil solids and to the dissolved organic carbon (DOC), which is present at relatively high concentrations (1–20 mm ) in the soil solutions. Because of the underlying functional similarity between metal binding by the solid and dissolved organic matter, the partition coefficient (and hence element mobility) will be relatively insensitive to changes in pH and metal-ion activity in the soil solution. 相似文献
63.
GARY W. ELLISON DVM MS Diplomate ACVS JAMIE R. BELLAH DVM Diplomate ACVS W. PRESTON STUBBS DVM JAMES VAN GILDER BS 《Veterinary surgery : VS》1995,24(2):140-147
Excision of perianal fistulas using a 1.064 micron wavelength neodymium:yttrium aluminum garnet (ND:YAG) contact tipped laser with primary wound closure was used to treat 20 dogs with perianal fistulas. Overall, 19 of 20 (95%) dogs had resolution of fistulas after one or more ND:YAG treatments. The period of resolution ranged from 10 to 42 months with a mean of 22.9 months. Sixteen of 20 (80%) dogs had resolved fistulas after one laser excision. Three of the four recurrences underwent additional laser treatments with successful results. The total number of laser procedures ranged from one to three with a mean of 1.2 procedures. Postoperatively, anal tone as judged by digital rectal examination was reduced in about 60% of the cases, but clinical evidence of fecal incontinence only occurred in four of 20 cases. This was managed effectively with diet modification. The tendency toward loss of anal tone or fecal incontinence depended on the severity of preexisting anal stenosis. On a client survey, 19 of 20 owners believed that their animals experienced less pain during defecation after surgery and rated the results as excellent or good. The overall success rate using ND:YAG laser excision compared very favorably with previously reported studies of other methods of treatment for perianal fistulas in dogs. 相似文献
64.
The life history of Tenualosa macrura in Sarawak, further notes on protandry in the genus and management strategies 总被引:1,自引:0,他引:1
S. J. M. BLABER G. FRY D.A. MILTON T. VAN DER VELDE O. BOON-TECK J. PANG & P. WONG 《Fisheries Management and Ecology》2005,12(3):201-210
Abstract The contraction of Tenualosa macrura (Bleeker) to the Sarawak coast and a small part of Sumatra, and the decline in its fishery mirror what has happened to three other species in the genus. Little was known of this species in its last stronghold in Sarawak where it is important for management and conservation reasons to understand its biology and life history. It forms part of a multispecies fishery where effort is uniform, but catches follow a lunar cycle. Tenualosa macrura is protandrous, but low numbers of small females suggest diandry. In Sumatra Tenualosa macrura spawn throughout the year, but in Sarawak have a seasonal peak in the NE monsoon (December). This has management implications because the Sarawak fishery ceases at this time because of adverse weather, hence reducing fishing pressure on spawning T. macrura . Management measures introduced in Sarawak for Tenualosa toli (Valenciennes) may therefore not be required for T. macrura . 相似文献
65.
D. FREESE W.H. VAN RIEMSDIJK S.E.A.T.M. VAN DER ZEE 《European Journal of Soil Science》1995,46(2):239-245
A model of P-sorption kinetics was developed, that accounts for the dependency of reaction rate on concentration, sorbed P content, sorption maximum and time. The sorption phenomena predicted by the model agree with available observations in the literature. The model was tested with batch experiments for 17 acid top– and subsoils. The experiments revealed a significant correlation between the sorption maximum, Fm, and the sum of amorphous iron and aluminium in soils. Plotting the dimensionless P–sorption ratio, F(c, t)/Fm, which may be interpreted as the fractional saturation of the sorption capacity of a soil, against the natural logarithm of the exposure variable, I, gave S–shaped curves. Different parts of the S–shaped curve can be experimentally assessed, depending on the initial fractional saturation of the P–sorption capacity of soils. Apart from this dependency, one set of parameter values sufficed to describe the sorption kinetics of 10 different sandy top– and subsoils. For non–sandy soils, the parameter values differed and depended on the initial P content. The model enables extrapolation to long times, which is necessary for applications to field conditions. 相似文献
66.
67.
68.
69.
70.
In vitro activity of five tetracyclines and some other antimicrobial agents against four porcine respiratory tract pathogens 总被引:4,自引:0,他引:4
A. PIJPERS B. VAN KLINGEREN E.J. SCHOEVERS J. H. M. VERHEIJDEN A. S.J. P. A. M. VAN MIERT 《Journal of veterinary pharmacology and therapeutics》1989,12(3):267-276
The minimal inhibitory concentrations (MIC) of five tetracyclines and ten other antimicrobial agents were determined for four porcine bacterial respiratory tract pathogens by the agar dilution method. For the following oxytetracycline-susceptible strains, the MIC50 ranges of the tetracyclines were: P. multocida (n = 17) 0.25-0.5 micrograms/ml; B. bronchiseptica (n = 20) 0.25-1.0 micrograms/ml; H. pleuropneumoniae (n = 20) 0.25-0.5 micrograms/ml; S. suis Type 2 (n = 20) 0.06-0.25 micrograms/ml. For 19 oxytetracycline-resistant P. multocida strains the MIC50 of the tetracyclines varied from 64 micrograms/ml for oxytetracycline to 0.5 micrograms/ml for minocycline. Strikingly, minocycline showed no cross-resistance with oxytetracycline, tetracycline, chlortetracycline and doxycycline in P. multocida and in H. pleuropneumoniae. Moreover, in susceptible strains minocycline showed the highest in vitro activity followed by doxycycline. Low MIC50 values were observed for chloramphenicol, ampicillin, flumequine, ofloxacin and ciprofloxacin against P. multocida and H. pleuropneumoniae. B. bronchiseptica was moderately susceptible or resistant to these compounds. As expected tiamulin, lincomycin, tylosin and spiramycin were not active against H. pleuropneumoniae. Except for flumequine, the MIC50 values of nine antimicrobial agents were low for S. suis Type 2. Six strains of this species showed resistance to the macrolides and lincomycin. 相似文献