全文获取类型
收费全文 | 14296篇 |
免费 | 1099篇 |
国内免费 | 71篇 |
专业分类
林业 | 653篇 |
农学 | 831篇 |
基础科学 | 125篇 |
2048篇 | |
综合类 | 1682篇 |
农作物 | 506篇 |
水产渔业 | 1071篇 |
畜牧兽医 | 7102篇 |
园艺 | 230篇 |
植物保护 | 1218篇 |
出版年
2023年 | 89篇 |
2021年 | 90篇 |
2020年 | 124篇 |
2019年 | 205篇 |
2018年 | 378篇 |
2017年 | 351篇 |
2016年 | 344篇 |
2015年 | 312篇 |
2014年 | 332篇 |
2013年 | 597篇 |
2012年 | 494篇 |
2011年 | 579篇 |
2010年 | 470篇 |
2009年 | 429篇 |
2008年 | 565篇 |
2007年 | 587篇 |
2006年 | 482篇 |
2005年 | 540篇 |
2004年 | 425篇 |
2003年 | 467篇 |
2002年 | 369篇 |
2001年 | 772篇 |
2000年 | 727篇 |
1999年 | 598篇 |
1998年 | 174篇 |
1997年 | 166篇 |
1996年 | 127篇 |
1995年 | 152篇 |
1994年 | 158篇 |
1993年 | 120篇 |
1992年 | 322篇 |
1991年 | 347篇 |
1990年 | 292篇 |
1989年 | 267篇 |
1988年 | 275篇 |
1987年 | 320篇 |
1986年 | 246篇 |
1985年 | 195篇 |
1984年 | 171篇 |
1983年 | 147篇 |
1982年 | 94篇 |
1981年 | 83篇 |
1980年 | 79篇 |
1979年 | 142篇 |
1978年 | 94篇 |
1977年 | 74篇 |
1975年 | 77篇 |
1974年 | 80篇 |
1971年 | 72篇 |
1969年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
北京香塘伟业投资管理有限责任公司 《饲料广角》2005,(17):20-22
中国人民银行日前宣布,经国务院批准.自2005年7月21日起,我国开始施行以市场供求为基础、参考一篮子货币进行调节、有管理的浮动汇率制度。针对广大现货生产、加工、贸易企业关心的人民币汇率变动对利率以及进出口的影响,笔者略作探讨。 相似文献
142.
北京香塘伟业投资管理有限责任公司 《饲料广角》2005,(24):19-20
自10月中旬以来,国内大豆市场经过禽流感疫情的洗礼后,国内国际大豆期现价格出现急速下跌行情,国内近期大豆大约期货价下跌3150元/t,豆粕一度下跌到2150元/t的年内次低点。由于禽流感疫情在淡化.短期内饲料企业补库意愿增强,再加上双节临近,备货现象明显,预计大豆市场表现短多长空格局。具体分析如下: 相似文献
143.
This paper reports results of a study conducted to investigate the concentrations of seven mineral elements in yak blood, forage and water resources around the Qinghai Lake in Qinghai Province in different seasons. Meanwhile, the nutritional compositions of the forage were also surveyed. The results suggest that the mineral elements and the forage nutrients change in a seasonal pattern. In yak blood,the sodium(Na)concentration varies from 0.291 to 0.034 mg/mL,and this is lower than the normal value. In the forage,the ratio calcium(Ca)to phosphorus(P)is 4.06~7.47:1 and potassium(K)to Na 30~27:1. These results indicate that the nutrition of the yak in the area is deficient in Na but high in K. For the withered forage sampled in February,the protein content is only 31.14% of the total protein in the forage growing at puerile stage in June. The severe loss of protein by 68. 9% and decrease of effective nutrients in the wintered forage are considered to be the reasons resulting in the poor condition of yak in winter and spring seasons. 相似文献
144.
145.
146.
Familial Congenital Methemoglobinemia in Pomeranian Dogs Caused by a Missense Variant in the NADH‐Cytochrome B5 Reductase Gene
下载免费PDF全文
![点击此处可从《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
H. Shino Y. Otsuka‐Yamasaki T. Sato K. Ooi O. Inanami R. Sato M. Yamasaki 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2018,32(1):165-171
Background
In veterinary medicine, congenital methemoglobinemia associated with nicotinamide adenine dinucleotide (NADH)‐cytochrome b5 reductase (b5R) deficiency is rare. It has been reported in several breeds of dogs, but little information is available about its etiology.Objectives
To analyze the NADH‐cytochrome b5 reductase gene, CYB5R3, in a Pomeranian dog family with methemoglobinemia suspected to be caused by congenital b5R deficiency.Animals
Three Pomeranian dogs from a family with methemoglobinemia were analyzed. Five healthy beagles and 5 nonrelated Pomeranian dogs without methemoglobinemia were used as controls.Methods
Methemoglobin concentration, b5R activity, and reduced glutathione (GSH) concentration were measured, and a turbidity index was used to evaluate Heinz body formation. The CYB5R3 genes of the affected dog and healthy dogs were analyzed by direct sequencing.Results
Methemoglobin concentrations in erythrocytes of the affected dogs were remarkably higher than those of the control dogs. The b5R activity of the affected dogs was notably lower than that of the control dogs. DNA sequencing indicated that this Pomeranian family carried a CYB5R3 gene missense variant (ATC→CTC at codon 194) that resulted in the replacement of isoleucine (Ile) by leucine (Leu).Conclusions and Clinical Importance
This dog family had familial congenital methemoglobinemia caused by b5R deficiency, which resulted from a nonsynonymous variant in the CYB5R3 gene. This variation (c.580A>C) led to an amino acid substitution (p.Ile194Leu), and Ile194 was located in the proximal region of the NADH‐binding motif. Our data suggested that this variant in the canine CYB5R3 gene would affect function of the b5R in erythrocytes. 相似文献147.
Effects of Moringa oleifera silage on milk yield,nutrient digestibility and serum biochemical indexes of lactating dairy cows
下载免费PDF全文
![点击此处可从《Journal of animal physiology and animal nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
B. Zeng J. J. Sun T. Chen B. L. Sun Q. He X. Y. Chen Y. L. Zhang Q. Y. Xi 《Journal of animal physiology and animal nutrition》2018,102(1):75-81
This study investigated the effects of Moringa oleifera (MO) as a partial substitute of alfalfa hay on milk yield, nutrient apparent digestibility and serum biochemical indexes of dairy cows. MO was harvested at 120 days post‐seeding. Fresh MO was cut, mixed with chopped oat hay (425:575 on a DM basis), ensiled and stored for 60 days. Sixty healthy Holstein dairy cows were allocated to one of three groups: NM (no MO or control), LM (low MO; 25% alfalfa hay and 50% maize silage were replaced by MO silage) or HM (high MO; 50% alfalfa hay and 100% maize silage were replaced by MO silage). The feeding trial lasted 35 days. The LM and HM diets did not affect dry matter (DM) intake, milk yield or milk composition (lactose, milk fat, milk protein and somatic cell count). The apparent digestibility of DM and NDF was lower for HM group than NM group. Additionally, there were no significant differences in serum biochemical indexes between the LM and NM groups. The HM group had lower serum concentrations of total cholesterol, high‐density lipoprotein cholesterol, and low‐density lipoprotein cholesterol and higher serum concentrations of urea than the NM group. The partial replacement of alfalfa hay (≤50%) and maize silage with MO silage had no negative effects on milk yield, in vivo nutrient apparent digestibility or serum biochemical indexes of lactating cows. 相似文献
148.
G. F. Difford D. W. Olijhoek A. L. F. Hellwing P. Lund M. A. Bjerring Y. de Haas 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2018,68(1):25-32
This study assessed the ranking of dairy cows using individual-level correlations for methane (CH4) emission on-farm using sniffers and in respiration chambers. In total 20 lactating dairy cows, ten Holstein and ten Jerseys were recorded using sniffers installed in milking robots for three weeks of lactation and subsequently in respiration chambers (RC) where they were each recorded on three occasions within the RC. Bivariate linear mixed models were used to determine the individual-level correlations (rI) between sniffer and RC phenotypes as proxies for genetic correlations. Despite differences in feeding and management, the predicted CH4 production from sniffers correlated highly with RC CH4 production rI?=?0.77?±?0.18 and CH4 breath concentration correlated nearly as well with RC CH4 production rI?=?0.75?±?0.20. These correlations between sniffers on-farm and RC demonstrate the potential of sniffers measurements as large-scale indicator traits for CH4 emissions in dairy cattle. 相似文献
149.
Barriers to and enablers of implementing antimicrobial stewardship programs in veterinary practices
下载免费PDF全文
![点击此处可从《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
150.
Immunohistochemical differentiation of reactive from malignant mesothelium as a diagnostic aid in canine pericardial disease
下载免费PDF全文
![点击此处可从《The Journal of small animal practice》网站下载免费的PDF全文](/ch/ext_images/free.gif)
E. Milne Y. Martinez Pereira C. Muir T. Scase D. J. Shaw G. McGregor L. Oldroyd E. Scurrell M. Martin C. Devine H. Hodgkiss‐Geere 《The Journal of small animal practice》2018,59(5):261-271