全文获取类型
收费全文 | 1356篇 |
免费 | 89篇 |
国内免费 | 2篇 |
专业分类
林业 | 135篇 |
农学 | 89篇 |
基础科学 | 15篇 |
291篇 | |
综合类 | 92篇 |
农作物 | 102篇 |
水产渔业 | 93篇 |
畜牧兽医 | 493篇 |
园艺 | 19篇 |
植物保护 | 118篇 |
出版年
2023年 | 9篇 |
2022年 | 24篇 |
2021年 | 34篇 |
2020年 | 41篇 |
2019年 | 38篇 |
2018年 | 53篇 |
2017年 | 60篇 |
2016年 | 57篇 |
2015年 | 33篇 |
2014年 | 54篇 |
2013年 | 126篇 |
2012年 | 70篇 |
2011年 | 79篇 |
2010年 | 72篇 |
2009年 | 57篇 |
2008年 | 62篇 |
2007年 | 25篇 |
2006年 | 47篇 |
2005年 | 25篇 |
2004年 | 29篇 |
2003年 | 33篇 |
2002年 | 34篇 |
2001年 | 38篇 |
2000年 | 26篇 |
1999年 | 31篇 |
1998年 | 23篇 |
1997年 | 28篇 |
1996年 | 27篇 |
1995年 | 9篇 |
1993年 | 11篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1973年 | 9篇 |
1972年 | 4篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 7篇 |
排序方式: 共有1447条查询结果,搜索用时 15 毫秒
31.
S Martín Rillo C de Alba Romero A Romero Rodriguez R Cidoncha & AJ Ziecik 《Reproduction in domestic animals》2001,36(6):297-300
As in other species, the reproductive tract in pigs increases in size with age and body weight, and the development of the reproductive tract depends on a balance between development of the pituitary–ovarian axis and the influence of metabolic hormones. Two experiments were conducted in prepubertal Duroc gilts, 150–180 days of age, to determine whether litter size is related to vaginal–cervix catheter penetration length during insemination. In experiment 1, oestrus was induced in 452 gilts with a combined dose of 400 IU Pregnant Mare Serum Gonadotrophine (PMSG) + 200 IU human chorionic gonadotropin (hCG). The gilts were classified into three catheter penetration length groups: Ih, ≤ 21 cm; IIh, > 21 and < 28 cm; IIIh, > 28 cm. The litter size was lowest in group Ih (7.35 ± 0.15) compared with groups IIh (7.81 ± 0.12; p < 0.05) and IIIh (10.0 ± 0.36; p < 0.001). In experiment 2, first oestrus was induced in 162 gilts by boar exposure. The gilts were classified into three catheter penetration length groups at insemination during their second oestrus: In, ≤ 24 cm; IIn, > 24 and < 26 cm; IIIn, > 26 cm. As in experiment 1, the litter size was lowest in the group with the shortest catheter penetration length (8.32 ± 0.19). The litter size was not different among gilts of groups IIn and IIIn (8.84 ± 0.35 and 9.56 ± 0.46, respectively), but litter size was lower (p < 0.05) in group In than in group IIn. Based on the combined data from both experiments, the correlation between the catheter penetration length and total number of piglets born was expressed as: y=5.346 ± 0.104x; r=0.361 (p < 0.05). Fertility rate was not different among the groups of gilts induced into oestrus by hormone treatment or inseminated in the second oestrus; however, the total fertility rate of boar‐exposed gilts was higher (p < 0.0001) than PMSG/hCG treated animals. Thus, it is possible to conclude that litter size at first farrowing is associated with vaginal–cervix catheter penetration length during insemination of the gilt. 相似文献
32.
Five potato cultivars of autumn crop, dipped in corn oil, were observed for 90 days at room temperature under natural light. Chlorophyll formation took place in minute quantities in treated tubers of ‘Désirée’ and ‘Prima’, and a little more in ‘Primura’, ‘Montana’ and ‘Multa’, whereas all control tubers became completely green after 90 days. Sugars were significantly lower and starch higher in treated tubers than in controls. No sprout-development was observed in treated tubers of all cultivars, but 50–70% control tubers had sprouted during this period. Peeling-losses were minimum in treated tubers and were 67.5–85.4% in controls. The oil-dipped potato tubers of all cultivars could safely be stored for 60 days without quality deterioration under ordinary conditions of temperature and light. 相似文献
33.
34.
35.
A Q Khan 《The British veterinary journal》1968,124(4):171-173
36.
M.A. Khan 《Veterinary parasitology》1981,8(4):327-336
In two experiments, a pour-on application of phosmet at 25 mg kg?1 reduced the harassment of cattle by black flies for up to 5–6 weeks posttreatment. During this period, the treated groups either gained more weight or loss less weight than their controls. The untreated groups made compensatory gains when teh black fly activity decreased or ceased. No significant differences existed between the average daily gains of a treated group and its control either for the posttreatment-periods of 9 and 15 weeks or for the experimental periods of 15 and 20 weeks in the two experiments.Black fly toxemia was not seen in indigenous cattle or in naive steers brought into a black fly infested area 1–2 weeks before the onset of black fly activity. 相似文献
37.
38.
Draghia-Akli R Cummings KK Khan AS Brown PA Carpenter RH 《Journal of animal science》2003,81(9):2301-2310
Our study focused on the evaluation of the pharmacological and toxicological effects of plasmid-mediated GHRH supplementation with electroporation in normal adult dogs over a 180-d period. Twenty-eight dogs (< 2 yr of age) were randomized to four groups. Three groups (four dogs/sex for each group) were treated with ascending doses of GHRH-expressing plasmid: 0.2, 0.6, and 1 mg. One group (two dogs of each sex) served as the control. Clinical observations and body weights were recorded. Hematological, serum biochemical, and urine analyses were performed. Serum IGF-I, ACTH, and insulin were determined. Necropsies were performed on d 93 and 180; organs were weighed and tissues were fixed and processed for light microscopy. Selected tissues were used to assess plasmid biodistribution on d 93. At all doses, plasmid GHRH caused increased weight gain (P < 0.001), without organomegaly. Serum glucose and insulin in fasted dogs remained within normal ranges at all time points. Adrenocorticotropic hormone was normal in all groups. Significant increases in number of red blood cells, hematocrit, and hemoglobin (P < 0.01) were observed. In conclusion, our study shows that plasmid-mediated GHRH supplementation is safe in electroporated doses up to 1.0 mg in young healthy dogs. 相似文献
39.
The spike 1 (S1) surface glycoprotein of infectious bronchitis virus (IBV) is the major inducer of the generation of virus neutralizing antibodies, and the administration of purified S1 has been shown to elicit a protective immune response against virulent virus challenge. On the basis of these observations, recombinant fowl poxvirus (rFPV) containing a cDNA copy of the S1 gene of IBV Mass 41 (rFPV-S1) was constructed and its immunogenicity and vaccine potential were evaluated. Initially, rFPV-S1 was shown to express the S1 in vito by indirect immunofluorescence staining and western blot analyses. Later, in vivo expression was demonstrated by the detection of IBV-specific serum immunoglobulin G and neutralization antibodies in the sera of chickens immunized with rFPV-S1. That the recombinant virus elicited anti-IBV protective immunity was indicated by the manifested, relatively mild clinical signs of disease, decreased titers of recovered challenge virus, and less severe histologic changes of the tracheas in virulent IBV Mass 41-challenged chickens previously receiving rFPV-S1 as compared with parental fowl poxvirus (FPV)-vaccinated control birds. In contrast, chickens immunized with either recombinant or parental FPV were resistant to a subsequent virulent FPV challenge. As to a preferred method of immunization, wing web administration appeared to be superior to the subcutaneous route because a greater percentage of birds vaccinated by the former protocol exhibited an anti-IBV humoral immune response. Thus, rFPV-S1 has potential as a poultry vaccine against both fowl pox and infectious bronchitis. 相似文献
40.
A flock of 810 pheasants experienced 6.2% mortality over 6 days. Affected birds were weak and lethargic for up to 24 hr before death. Examined birds were thin, and gross lesions consisted of thick opaque crops and cecal cores. Histologically, there was capillariasis of the crop and multifocal ulcerative typhlitis with Heterakis spp. infection, and numerous systemic intravascular monocytes were filled with clusters of blue rod-shaped organisms. The organisms were gram-positive bacilli by Brown and Brenn staining and ultrastructural analysis. Liver bacterial cultures were negative for pathogenic bacteria. Erysipelas septicemia was diagnosed by an Erysipelothrix species-specific polymerase chain reaction method with the substrate DNA isolated from formalin-fixed, paraffin-embedded liver. 相似文献