全文获取类型
收费全文 | 12633篇 |
免费 | 934篇 |
专业分类
林业 | 1254篇 |
农学 | 476篇 |
基础科学 | 64篇 |
2909篇 | |
综合类 | 814篇 |
农作物 | 525篇 |
水产渔业 | 971篇 |
畜牧兽医 | 5043篇 |
园艺 | 344篇 |
植物保护 | 1167篇 |
出版年
2024年 | 22篇 |
2023年 | 107篇 |
2022年 | 146篇 |
2021年 | 264篇 |
2020年 | 257篇 |
2019年 | 195篇 |
2018年 | 590篇 |
2017年 | 555篇 |
2016年 | 526篇 |
2015年 | 413篇 |
2014年 | 479篇 |
2013年 | 736篇 |
2012年 | 969篇 |
2011年 | 915篇 |
2010年 | 517篇 |
2009年 | 417篇 |
2008年 | 802篇 |
2007年 | 739篇 |
2006年 | 603篇 |
2005年 | 616篇 |
2004年 | 573篇 |
2003年 | 529篇 |
2002年 | 428篇 |
2001年 | 297篇 |
2000年 | 278篇 |
1999年 | 246篇 |
1998年 | 84篇 |
1997年 | 68篇 |
1996年 | 49篇 |
1995年 | 70篇 |
1994年 | 45篇 |
1993年 | 44篇 |
1992年 | 85篇 |
1991年 | 74篇 |
1990年 | 65篇 |
1989年 | 66篇 |
1988年 | 60篇 |
1987年 | 49篇 |
1986年 | 48篇 |
1985年 | 48篇 |
1984年 | 43篇 |
1983年 | 36篇 |
1979年 | 37篇 |
1974年 | 26篇 |
1973年 | 21篇 |
1972年 | 22篇 |
1971年 | 23篇 |
1970年 | 27篇 |
1969年 | 25篇 |
1968年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Muscle biopsies were taken from the middle gluteal muscle of 28 Standardbred trotters, 3-4 years of age. The 13 horses in Group T were trained consistently from 18 months of age, whereas the 15 horses in Group UT were not exposed to any systematic training before 3 years of age. Group T horses had a lower percentage of Type IIB fibres (31%) than did Group UT horses (39%). Citrate synthase (CS) activity, representing oxidative capacity, was higher in Group T (72 mmol kg-1 min-1) than in Group UT (47 mmol kg-1 min-1). Biopsies were taken from 4 horses in each group when they were foals and then annually until 3-4 years of age. Results from this study indicate that regular training of Standardbreds from 18 months of age resulted in increased CS activity and a decrease in the percentage of Type IIB fibres. This study shows that training, not growth, is the main factor that induces a high oxidative capacity and a high Type IIA/IIB fibre ratio in muscle of Standardbred trotters. 相似文献
2.
3.
Protective activities of heat-inactivated (60 degrees C for 30 min) merthiolate preserved Bordetella bronchiseptica and B. pertussis bacterins were compared in intraperitoneally immunized mice challenged intracerebrally (i.p./i.c.) or intraperitoneally (i.p./i.p.). In the i.p./i.c. assay (Kendrick test), a B. pertussis bacterin protected mice against challenge with B. pertussis 18-323, as well as against phase I cytotoxic and non-cytotoxic strains of B. bronchiseptica. A B. bronchiseptica bacterin, prepared from a phase I cytotoxic strain, gave protection against two phase I B. bronchiseptica strains, irrespective of their cytotoxin-production. A non-cytotoxic phase I strain of B. bronchiseptica elicited protection against the homologous strain only. Neither cytotoxic nor non-cytotoxic B. bronchiseptica strains protected mice challenged with B. pertussis 18-323. Vaccines prepared from phase III strains of B. bronchiseptica were not protective at all against any of the challenge strains. No such differences in the protective activities of the bacterins could be detected by the i.p./i.p. method. They seem to cross-protect equally well. The results indicate that the Kendrick test may be useful in testing potency of different B. bronchiseptica bacterins. 相似文献
4.
5.
Jim GK Ribble CS Guichon PT Thorlakson BE 《The Canadian veterinary journal. La revue veterinaire canadienne》1991,32(10):613-617
A 90-day finishing trial involving 144 feedlot heifers was conducted to compare the performance parameters and carcass characteristics of open heifers, therapeutically aborted heifers, and pregnant heifers. In the first 28 days of the trial, the aborted heifers had reduced (p < 0.05) feed intake (FI), average daily gain (ADG), and feed efficiency (FE) compared to pregnant and open heifers. Over the entire trial, on a live weight basis, the aborted group had reduced (p < 0.05) final weight, ADG, and FE compared to pregnant and open heifers. However, when the data were adjusted for total uterine weight, the aborted and open heifers had improved (p < 0.05) final weight, ADG, and FE compared to pregnant heifers. The aborted and open group had a higher (p < 0.05) carcass weight, rib eye area, dressing percentage, and cutability estimate compared to the pregnant heifers. The aborted group had lower (p < 0.05) carcass weight than the open heifers. Over the entire 90-day feeding period, there were no statistically significant differences among the groups with respect to feed intake (FI), average fat, grade fat, and carcass grades. Also, there were no significant health problems or mortality in any of the groups.
In the economic analysis, aborted heifers returned $26.41 per head more than pregnant heifers. Open heifers returned $39.94 per head more than aborted heifers, and $66.35 more than pregnant heifers. Thus, aborting feedlot heifers during the second trimester was determined to be a safe and cost effective management decision.
相似文献6.
7.
8.
Evaluation of an in-office allergy screening test in nonatopic dogs having various intestinal parasites 下载免费PDF全文
Paradis M Lécuyer M 《The Canadian veterinary journal. La revue veterinaire canadienne》1993,34(5):293-295
An in-office allergy screening kit was evaluated in 10 dogs that had no clinical signs of atopy but had various intestinal parasites. All 10 dogs had a positive reaction to the dust mite Dermatophagoïdes farinae, and four dogs had positive reactions to at least one other group of allergens. The kit as presently marketed gives numerous false positive results in parasitized nonatopic dogs. 相似文献
9.
10.
Two strains of bovine Theileria from northern Nigeria were shown to be identical to Theileria mutans in the indirect immunofluorescent antibody test. One of the strains was transmitted by the tick Amblyomma variegatum; large macroschizonts, typical for T mutans, could be demonstrated in infected cattle. It is concluded from these experiments and from the literature that there is reliable evidence so far for the occurrence in Nigeria of only two bovine Tehileria species, T mutans and T velifera. 相似文献