全文获取类型
收费全文 | 323611篇 |
免费 | 17872篇 |
国内免费 | 690篇 |
专业分类
林业 | 24825篇 |
农学 | 14321篇 |
基础科学 | 3020篇 |
47624篇 | |
综合类 | 42916篇 |
农作物 | 17689篇 |
水产渔业 | 18515篇 |
畜牧兽医 | 140530篇 |
园艺 | 6550篇 |
植物保护 | 26183篇 |
出版年
2019年 | 3773篇 |
2018年 | 4513篇 |
2017年 | 4952篇 |
2016年 | 5196篇 |
2015年 | 4592篇 |
2014年 | 5952篇 |
2013年 | 16653篇 |
2012年 | 8305篇 |
2011年 | 10768篇 |
2010年 | 8236篇 |
2009年 | 8591篇 |
2008年 | 10055篇 |
2007年 | 9165篇 |
2006年 | 9560篇 |
2005年 | 8654篇 |
2004年 | 8478篇 |
2003年 | 8270篇 |
2002年 | 7654篇 |
2001年 | 8942篇 |
2000年 | 8557篇 |
1999年 | 7443篇 |
1998年 | 4444篇 |
1997年 | 4494篇 |
1996年 | 4210篇 |
1995年 | 4845篇 |
1994年 | 4306篇 |
1993年 | 3972篇 |
1992年 | 6062篇 |
1991年 | 6272篇 |
1990年 | 6113篇 |
1989年 | 6050篇 |
1988年 | 5431篇 |
1987年 | 5513篇 |
1986年 | 5509篇 |
1985年 | 5634篇 |
1984年 | 4975篇 |
1983年 | 4536篇 |
1982年 | 3544篇 |
1981年 | 3349篇 |
1980年 | 3282篇 |
1979年 | 4443篇 |
1978年 | 3857篇 |
1977年 | 3426篇 |
1976年 | 3156篇 |
1975年 | 3195篇 |
1974年 | 3775篇 |
1973年 | 3766篇 |
1972年 | 3492篇 |
1971年 | 3330篇 |
1970年 | 3193篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
861.
J Sherrill T Schock J L Dunn D J St Aubin V V Burnley S E Poet 《Journal of zoo and wildlife medicine》2001,32(1):17-24
Humoral immune responses of black-footed penguins (Spheniscus demersus) to DNA-mediated immunization with a beta-galactosidase reporter gene expression plasmid were evaluated. Six male and 6 female adult penguins received either test plasmid, pCMV-beta, containing the beta-galactosidase gene or control plasmid, pCI, lacking a gene for expression. Three birds from each group were used previously in a diluent control group and given one injection of sterile saline. All samples were screened for anti-beta-galactosidase antibodies by indirect enzyme-linked immunosorbent assay with anti-chicken immunoglobulin G as secondary antibody. Antibodies to beta-galactosidase were detected in the sera of pCMV-beta-inoculated penguins, with a peak response on day 21. Antibody titers of the test plasmid group versus both control groups on days 21, 28, and 42 differed significantly. These results demonstrate that black-footed penguins can be safely transfected with the gene encoding beta-galactosidase and will mount a humoral response against the in vivo-expressed protein. Knowledge from this initial study can be applied to the development of DNA-mediated vaccines against specific infectious diseases of penguins. 相似文献
862.
AM Mwanza A Madej H Kindahl N Lundeheim & S Einarsson 《Reproduction in domestic animals》2001,36(3-4):157-161
The effects of lipopolysaccharide ( Escherichia coli , O55:B5), administered 18 h after ovulation in the second oestrus after weaning on the hormonal profiles in 14 Swedish cross-bred (Landrace × Yorkshire) multiparous sows were studied. The endotoxin group (E-group) sows were administered with 300 ng/kg of lipopolysaccharide (LPS) whereas the control group (C-group) sows were administered 5 ml of saline intravenously via an indwelling jugular cannula. Blood samples for hormonal analyses were collected from all sows until slaughter. In the E-group, progesterone, cortisol and prostaglandin F2α metabolite levels increased significantly (p < 0.05) following LPS compared with the C-group. It can be concluded from this study that apart from elevating cortisol and prostaglandin F2α metabolite, LPS also elevates progesterone levels. 相似文献
863.
864.
D. Sharifi J. Singh P.K. Peshin A.P. Singh 《Veterinary anaesthesia and analgesia》1991,18(Z1):309-314
Cardio pulmonary embarrassment was induced with thiopentone sodium in 35 healthy adult donkeys divided in to seven groups of five animals. “To effect” anaesthetic dose was (12.72 ± 0.69 mg/kg) which caused transient hypotension, tachycardia and hypoxemia. A stable fall in MAP 1. 6.77 ± 0.287 Kpa (50.78 ± 2.15 mmHg) and a flat EEG were considered to indicate acute circulatory insufficiency due to thiopentone overdose. 相似文献
865.
866.
867.
A.E. Wanger DVM MS W.W. Muir III DVM Phd R.M. Bednaraki DVM MS 《Journal of Veterinary Emergency and Critical Care》1991,1(1):14-18
The purpose of this study was to determine whether lingual vanous blood gas samples reflect arterial acid-base gas status in anethetized dogs. Heparinized blood samples were drawn simultaneously from the lingual vein and a peripheral artery in 50 anestheized dogs that were clinical surgical patients, as well as from four experimental dogs in which hemorrahaic shock was being studied. Blood pH, oxygen tension (PO2 ), and bicarbonate (HCO3- )) from the two sources in clinical patients showed significant liner correlation, although arterial PO2 )(PaO2 )) tended to be approximately 110mm Hg higher than lingual venous PO2 ). During hemorrahgic shock, however, PaO2 ) and PaCO2 ) were significantly different from lingual venous PO2 ) and PCO2 ), Lingula venous blood gas analysis may be useful in assessing acid-base and blood gas status in routline cases, but should not be relied upon in dogs with low cardiac output or poor perfusion. 相似文献
868.
C. P. Verschueren P. J. Selman J. J. M. de Vijlder J. A. Mol 《Domestic animal endocrinology》1991,8(4):509-519
Canine thyroglobulin (cTg) has been isolated and purified. It has similar electrophoretic patterns as Tg from other mammalian species. The main fraction had a MW of 660,000, whereas also fractions of a MW of approximately 1,300,000 (dimer) and 330,000 (subunit) were present. The iodine content was 0.8 to 1.0 % (w/w). cTg did not cross-react with antibodies against human Tg to a degree that would allow the use of a radioimmunoassay for human Tg for the determination of cTg in serum or plasma. Therefore a polyclonal antiserum was raised against cTg and a homologous radioimmunoassay was developed, which was sensitive (0.4 μg/l) and specific (cross-reactivity in cTg assay of human Tg, goat Tg, T4, T3, and DIT < 0.01 %).
Plasma Tg levels in normal dogs of both sexes and aged 3–15 years amounted to 192 ± 73 μg/l (mean ± SD, n=30). There was no relation between plasma Tg and T4 levels. 相似文献
869.
Fluid accumulation in mouse ligated intestine inoculated with the vascular permeability factor produced by Bacillus cereus. 总被引:1,自引:0,他引:1
K Shinagawa K Sato H Konuma N Matsusaka S Sugii 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1991,53(2):167-171
Partially purified vascular permeability (VP) factor (VPF) of Bacillus cereus induced fluid accumulation in the ligated intestinal loops of mouse (MIL) and rabbit (RIL), suggesting that the VP activity may correlate with fluid accumulation in ligated intestinal loops of these animals. Fluid accumulation was observed at 6-8 hr in 55-67% of mouse intestinal loops inoculated with 40-50 immunodiffusion units (IDU) of partially purified VPF, whereas it was found at 2 hr in all loops with 400-600 IDU of partially purified VPF. In rabbit intestinal loops with 120-190 IDU of partially purified VPF, fluid accumulation was observed at 6 hr. From these findings, VPF produced by B. cereus can be easily detected in both MIL and RIL. The intestinal tissue of mouse intestinal loops was histopathologically damaged at different concentrations of the VPF to induce fluid accumulation. With 50 IDU of partially purified VPF, severe edema was found in the laminia proprial layer and submucosa. With 600 IDU of partially purified VPF, on the other hand, severe necrosis in the surface epithelium of villus and laminia proprial layer, and hyperemia in the submucosa were observed, suggesting that partially purified VPF may be cytotoxic and/or intestinecrotic. 相似文献
870.