全文获取类型
收费全文 | 92447篇 |
免费 | 4731篇 |
国内免费 | 317篇 |
专业分类
林业 | 5272篇 |
农学 | 3471篇 |
基础科学 | 620篇 |
12684篇 | |
综合类 | 15767篇 |
农作物 | 3949篇 |
水产渔业 | 4366篇 |
畜牧兽医 | 43430篇 |
园艺 | 1621篇 |
植物保护 | 6315篇 |
出版年
2019年 | 912篇 |
2018年 | 2454篇 |
2017年 | 2571篇 |
2016年 | 1835篇 |
2015年 | 1233篇 |
2014年 | 1493篇 |
2013年 | 3429篇 |
2012年 | 2955篇 |
2011年 | 3941篇 |
2010年 | 3044篇 |
2009年 | 2963篇 |
2008年 | 3593篇 |
2007年 | 3743篇 |
2006年 | 2625篇 |
2005年 | 2445篇 |
2004年 | 2310篇 |
2003年 | 2322篇 |
2002年 | 2104篇 |
2001年 | 2593篇 |
2000年 | 2557篇 |
1999年 | 2018篇 |
1998年 | 806篇 |
1997年 | 847篇 |
1996年 | 779篇 |
1995年 | 863篇 |
1994年 | 778篇 |
1993年 | 753篇 |
1992年 | 1523篇 |
1991年 | 1621篇 |
1990年 | 1504篇 |
1989年 | 1561篇 |
1988年 | 1458篇 |
1987年 | 1436篇 |
1986年 | 1462篇 |
1985年 | 1412篇 |
1984年 | 1125篇 |
1983年 | 1013篇 |
1979年 | 1145篇 |
1978年 | 921篇 |
1977年 | 804篇 |
1976年 | 785篇 |
1975年 | 857篇 |
1974年 | 1100篇 |
1973年 | 1033篇 |
1972年 | 1067篇 |
1971年 | 963篇 |
1970年 | 933篇 |
1969年 | 946篇 |
1968年 | 790篇 |
1967年 | 837篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
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
112.
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
113.
114.
Effects of monensin on Mg, Ca, P and Zn metabolism and tissue concentrations in lambs 总被引:1,自引:0,他引:1
A study consisting of two trials was conducted to determine the effects of monensin on the apparent absorption and retention of magnesium (Mg), phosphorus (P), calcium (Ca) and zinc (Zn) and to determine mineral changes in tissue and ruminal fluid. Eight lambs (39 kg) were used in trial 1, and 10 lambs (37 kg) were used in trial 2. Animals were blocked by weight and fed a high concentrate diet with or without 20 mg/kg monensin. Trials began with a dietary adjustment period lasting 18 d in trial 1 and 21 d in trial 2. Animals were then placed in metabolism stalls for a 10-d stall adjustment period followed by a 12-d collection period. Collections to determine mineral balance were made during the first 10 d of the collection period. Blood and ruminal fluid samples were taken on d 11 of the collection period. Lambs were slaughtered on d 12 of the collection period and tissue samples were collected. Monensin supplementation increased (P less than .05) Mg retention 42.0%. Urinary Ca excretion decreased (P less than .05) 60.0% when monensin was fed. Monensin supplementation decreased (P less than .05) liver Ca and bone Ca, 45.5 and 2.9%, respectively. Apparent P digestibility increased (P less than .05) 40.0% and P retention increased (P less than .10) 26.8% due to monensin supplementation. Both apparent absorption and retention of Zn increased (P less than .01) 50.0 and 45.0%, respectively, with monensin supplementation. Ruminal fluid Zn concentrations decreased (P less than .05) 33.0% with the addition of monensin.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
115.
116.
2 groups of 20 cocks each were selected at random from non-dwarf White Leghorn (28 weeks post-hatch) and dwarf Krishna-J (38 weeks post-hatch) genotypes. The treated groups comprised 10 White Leghorn and 10 Krishna-J cocks. The remaining birds served as controls. 8 weeks prior to furazolidone treatment, semen was collected from both control groups at regular 4-day intervals, for 4 weeks. Cocks of the treated groups of both genotypes were administered furazolidone (0.14 g/bird/day) for 7 consecutive days. Semen was collected from all cocks at regular 4-day intervals for 4 weeks. Semen from the cocks of the same group was pooled. The pooled ejaculate volume and sperm density did not differ significantly in the 2 genotypes. The semen output as well as sperm density increased along with progressive attainment of sexual maturity. Furazolidone treatment caused significant reduction in semen volume as well as sperm concentration in either genotype. 相似文献
117.
The records of 71 horses with small intestinal disorders requiring surgical correction were disorders requiring surgical correction were reviewed to compare the prevalence of laminitis in those horses treated prophylactically with heparin and the prevalence of horses not treated with heparin. The prevalence of laminitis was 13% (9/71), and there was no significant difference (P less than 0.05) in the prevalence of laminitis between the 2 groups. The lack of significant benefit after treatment with heparin indicates that further work needs to be done on the equine coagulation system before heparin can be advocated for prevention of laminitis. 相似文献
118.
119.
120.
M A Albassam B J Houston P Greaves N Barsoum 《Journal of the American Veterinary Medical Association》1989,194(11):1595-1597
A 13-month-old Beagle became anorectic and had fever, stiff gait, and tenderness in the inguinal region. Clinical signs of disease were associated with neutrophilia and a decrease in the albumin-to-globulin ratio. The dog became clinically normal for 5 days after 3 days of treatment with penicillin G and dihydrostreptomycin. Clinical signs of disease recurred, and the dog was euthanatized after failing to respond to administration of a trimethoprim-sulfamethoxazole combination for 9 days. Disseminated arteritis was seen in the testes, epididymides, mesentery, coronary arteries, aorta, and thyroid gland. Lesions were seen in large and medium-sized arteries and varied from acute necrotizing arteries to a chronic lesion with organization and recanalization of thrombi. The clinical signs of disease resembled those of Beagle pain syndrome, described in laboratory Beagles. 相似文献