全文获取类型
收费全文 | 2426篇 |
免费 | 129篇 |
国内免费 | 1篇 |
专业分类
林业 | 137篇 |
农学 | 69篇 |
基础科学 | 12篇 |
427篇 | |
综合类 | 298篇 |
农作物 | 156篇 |
水产渔业 | 176篇 |
畜牧兽医 | 1002篇 |
园艺 | 67篇 |
植物保护 | 212篇 |
出版年
2023年 | 18篇 |
2022年 | 14篇 |
2021年 | 45篇 |
2020年 | 62篇 |
2019年 | 63篇 |
2018年 | 44篇 |
2017年 | 46篇 |
2016年 | 46篇 |
2015年 | 40篇 |
2014年 | 61篇 |
2013年 | 108篇 |
2012年 | 115篇 |
2011年 | 170篇 |
2010年 | 67篇 |
2009年 | 87篇 |
2008年 | 125篇 |
2007年 | 141篇 |
2006年 | 143篇 |
2005年 | 119篇 |
2004年 | 139篇 |
2003年 | 105篇 |
2002年 | 111篇 |
2001年 | 35篇 |
2000年 | 35篇 |
1999年 | 37篇 |
1998年 | 22篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 15篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 33篇 |
1991年 | 17篇 |
1990年 | 30篇 |
1989年 | 25篇 |
1988年 | 16篇 |
1987年 | 21篇 |
1986年 | 19篇 |
1985年 | 27篇 |
1984年 | 28篇 |
1982年 | 11篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1976年 | 16篇 |
1975年 | 11篇 |
1974年 | 14篇 |
1973年 | 12篇 |
1967年 | 11篇 |
排序方式: 共有2556条查询结果,搜索用时 281 毫秒
51.
M. Angeles Achon Marion Pinner Vicente Medina George P. Lomonossoff 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(7):697-705
Two isolates of maize dwarf mosaic virus (MDMV-Sp and MDMV-Spl) obtained from maize in the northeast of Spain were studied. Both isolates induced similar reactions on 6 sorghum cultivars, johnsongrass and oat (cv. Clintland), with the exception of MDMV-Sp which produced a different reaction on one sorghum cultivar. Thirty-three grass species were tested as possible hosts (16 previously untested) and 18 were found to be susceptible. Among those, eight were previously unidentified hosts for MDMV:Aegilops ovata, A. ventricosa, Avena barbata, Bromus alopecurus, B. diandrus, B. fasciculatus, Echinaria capitata andLolium rigidum. Both isolates were transmitted from maize to maize nonpersistently byRhopalosiphum maidis, R. padi, Schizaphis graminum andSitobium avenae. The virus was not seed-transmitted in Mo17 and B73 maize inbred lines. Pinwheels, scrolls and short curved laminated aggregates were observed in the cytoplasm of maize cells infected by MDMV-Sp or MDMV-Sp1. In addition, laminated aggregates were observed in cells infected by MDMV-Sp1. 相似文献
52.
D. Craig Heim George G. Kennedy Fred L. Gould John W. Van Duyn 《Pest management science》1992,34(4):303-311
Progeny from reciprocal F1 crosses and F1 backcrosses between fenvalerate-resistant and fenvalerate-susceptible Colorado beetles, Leptinotarsa decemlineata (Say), and between carbofuran-resistant and carbofuran-susceptible Colorado beetles were bioassayed to investigate the mode of inheritance of resistance to these chemicals. Bioassays of progeny from these crosses indicate that resistance to fenvalerate is inherited in a semi-recessive, sex-linked manner and carbofuran resistance is inherited in a partially dominant autosomal fashion. Log concentration/probit mortality lines and chi-square tests, however, indicate that multiple genes may be involved in resistance to both insecticides. 相似文献
53.
A residual bioassay was used to determine insecticide susceptibility in populations of Colarado potato beetle, Leptinotarsa decemlineata (Say), in eastern North Carolina. Mean bioassay mortalities were subjected to correlation analysis to assess patterns of resistance among tested insecticides. Within insecticide classes, cross-resistance patterns were observed between carbaryl and carbofuran (carbamates), fenvalerate and permethrin (pyrethroids), and among azinphosmethyl, methamidophos, and phosmet (organophosphates). Significant associations between insecticides from different insecticide classes were concluded to be due to multiple resistance. Knowledge of multiple and cross-resistance patterns are discussed in relation to the bioassay as a tool for monitoring insecticide resistance. 相似文献
54.
55.
56.
The mechanisms of resistance to pyrethroids were studied in a permethrin-selected (147-R) strain of the house fly, Musca domestica L. Approximately 12-fold synergism was obtained with a mixture of (1R)-trans-permethrin:piperonyl butoxide (1:5) so that the resistance decreased from 97-fold to 22-fold. Tests with the esterase inhibitor S,S,S-tributyl phosphorotrithioate produced very little synergism in either the resistant (R) strain (1.6-fold) or the susceptible (S) strain (1.9-fold). An investigation of the microsomal components revealed that compared to the S strain, the R strain demonstrated twice as much cytochrome P-450 and cytochrome b5 and double the rate of NADPH-cytochrome c reductase activity. In addition, the rate of p-nitroanisole O-demethylation was found to be six times greater in the R strain. An in vivo accumulation study showed that the R strain displayed a decreased rate of penetration of trans-[14C]permethrin. When treated at equitoxic doses the R strain was found to tolerate 50-fold more internal permethrin than the S strain. An in vitro metabolism study indicated that there was no difference between strains in the overall rate of metabolism of trans-[14C]permethrin. The evidence obtained supports the conclusion that several resistance factors are involved but that decreased sensitivity of the nervous system to the action of pyrethroids is the principal mechanism of resistance in the 147-R strain. 相似文献
57.
58.
Experimental Exposure of Pigs to Infectious Bovine Rhinotracheitis (IBR) Virus 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
George T. Woods R. C. Meyer Joseph Simon 《Canadian journal of veterinary research》1968,32(3):480-482
Thirteen specific-pathogen-free pigs were used in an experiment to determine the pathogenicity of IBR virus for pigs. Three pigs were used as controls, eight were exposed to IBR virus by either the intravenous, subcutaneous, intratracheal, or intranasal route, and two pigs served as contact controls. The clinical response consisted of a temperature rise, depression and variable lymphocytosis. The major tissue alterations were interstitial pneumonitis, and peribronchiolitis with round cell aggregates and giant cell formation. IBR virus was not recovered from any of the pigs. A serologic response was detected in only the pig injected intravenously. 相似文献
59.
60.
Clinical chemical determinations were carried out on blood removed by cardiac puncture from 49 mink affected with Aleutian disease and 25 normal animals and the respective differences tested for statistical significance. Blood urea nitrogen, serum total protein and globulin, thymol turbidity, glutamic oxalacetic and glutamic pyruvic transaminases and amylase were definitely elevated in the affected animals whereas serum calcium, albumin and A/G ratio were depressed. No statistically significant difference was apparent between the two groups in the comparison of inorganic phosphorus, alkaline and acid phosphatases, bilirubin, total cholesterol and esters, cephalin-cholesterol flocculation (3+ in each case), sodium, potassium, chloride, CO2-combining power, leucine aminopeptidase and lactic dehydrogenase (means: over 2,000 u./ml.). For both the control and affected mink, the distribution of serum lactic dehydrogenase isozymes resembled that of human homologous serum hepatitis. Electrophoresis of serum proteins confirmed earlier findings of hypergammaglobulinemia in the diseased animals but a fast-moving or pre-albumin component, averaging 4% of the total protein, occurred in both the diseased and normal mink. 相似文献