全文获取类型
收费全文 | 1083篇 |
免费 | 40篇 |
国内免费 | 97篇 |
专业分类
林业 | 52篇 |
农学 | 70篇 |
基础科学 | 41篇 |
102篇 | |
综合类 | 427篇 |
农作物 | 80篇 |
水产渔业 | 25篇 |
畜牧兽医 | 275篇 |
园艺 | 78篇 |
植物保护 | 70篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 43篇 |
2021年 | 42篇 |
2020年 | 26篇 |
2019年 | 38篇 |
2018年 | 32篇 |
2017年 | 46篇 |
2016年 | 27篇 |
2015年 | 50篇 |
2014年 | 54篇 |
2013年 | 52篇 |
2012年 | 70篇 |
2011年 | 86篇 |
2010年 | 65篇 |
2009年 | 88篇 |
2008年 | 76篇 |
2007年 | 61篇 |
2006年 | 57篇 |
2005年 | 36篇 |
2004年 | 21篇 |
2003年 | 20篇 |
2002年 | 25篇 |
2001年 | 20篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1978年 | 3篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有1220条查询结果,搜索用时 15 毫秒
111.
甘肃省坡耕地利用状况与退耕还林还草技术对策研究 总被引:6,自引:2,他引:4
对甘肃省坡耕地的利用状况及其退耕的可行性进行了较为全面的分析,按照因地制宜的原则,将退耕区域划分为陇中黄土丘陵沟壑区、陇东黄土台塬区、山高坡陡的陇南山区与河西防风固沙区四大区,并就各区退耕后的还林还草方式进行了具体的论证,提出了15°~25°和25°以上坡耕地退耕还林还草的具体技术对策。 相似文献
112.
The prevalence, aetiology and epidemiological features of subclinical mastitis were investigated in 358 lowland ewes in seven flocks in southern England. Milk samples (2092) were collected at 3-weekly intervals; those which were both bacteriologically and Whiteside test positive were deemed to have originated from glands with subclinical mastitis. The period prevalence of subclinical mastitis was 11.7% and the prevalence remained relatively constant over the course of lactation (5.5-7.0%). The predominant bacterial isolates from 48 glands with subclinical mastitis were streptococci (42%), coagulase-negative staphylococci (33%), Pasteurella haemolytica (17%) and Staphylococcus aureus (8%). Coagulase-negative staphylococci were the predominant isolates (53%) from samples which did not show a positive Whiteside test result. The prevalence of subclinical mastitis increased with age of ewe but was not influenced by the presence of teat lesions. There was a significant association between the development of clinical mastitis (26 glands) and antecedent subclinical mastitis caused by the same organism (10 glands). 相似文献
113.
狄世深 《湖南农业大学学报(自然科学版)》2006,(2)
刑法中的身份是指刑法中对定罪、量刑具有影响的个人人身方面的客观要素。它具体包括行为人的身份、刑事被害人的身份和行为对象人的身份三种,其中后二者是交叉关系。在这些身份中,既包括刑法明文规定的身份,也包括虽然刑法没有明文规定,但却对定罪、量刑有影响的身份;既包括自然人的身份,也包括单位的身份。刑法中的身份有五个方面的特征,即客观人身性、有效性、针对性、相对性和先在性。 相似文献
114.
R M Dabareiner J P Watkins G K Carter C M Honnas T Eastman 《Journal of the American Veterinary Medical Association》2001,219(1):82-86
OBJECTIVE: To determine clinical, radiographic, and scintigraphic abnormalities in and outcome of horses with septic or nonseptic osteitis of the axial border of the proximal sesamoid bones. DESIGN: Retrospective study. ANIMALS: 8 horses. PROCEDURE: Data collected from medical records included signalment; history; horse use; severity and duration of lameness; results of perineural anesthesia, radiography, ultrasonography, and scintigraphy; and outcome following surgery. RESULTS: Five horses did not have any evidence of sepsis; the other 3 had sepsis of the metacarpophalangeal or metatarsophalangeal joint or the digital synovial sheath. All horses had a history of chronic unilateral lameness. Three of 5 horses improved after diagnostic anesthesia of the metacarpophalangeal or metatarsophalangeal joint; the other 2 improved only after diagnostic anesthesia of the digital synovial sheath. Nuclear scintigraphy was beneficial in localizing the source of the lameness to the proximal sesamoid bones in 4 horses. Arthroscopy of the palmar or plantar pouch of the joint or of the digital synovial sheath revealed intersesamoidean ligament damage and osteomalacia of the axial border of the proximal sesamoid bones in all horses. All 5 horses without sepsis and 1 horse with sepsis returned to their previous uses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that osteitis of the axial border of the proximal sesamoid bones is a distinct entity in horses that typically is associated with inflammation of the associated metacarpointersesamoidean or metatarsointersesamoidean ligament and may be a result of sepsis or nonseptic inflammation. Arthroscopic debridement may allow horses without evidence of sepsis to return to their previous level of performance. 相似文献
115.
116.
T S Taylor J P Watkins J Schumacher 《Journal of the American Veterinary Medical Association》1987,191(6):677-680
A temporary indwelling liner was surgically installed in 17 horses with grade III or grade IV rectal tears. The rectal tears of 9 of the horses healed. The remaining 8 horses developed peritonitis as a result of peritoneal contamination before surgery, a change in grade of the tear, or material failure. 相似文献
117.
After premedication with intravenous xylazine 30 ponies were anaesthetised for castration under field conditions with intravenous ketamine, thiopentone or methohexitone. The duration of anaesthesia was adequate for surgery and the times taken to stand were similar in each group. The recovery of the ponies after ketamine was quieter than after either of the barbiturates and this may be an advantage when skilled assistance is lacking. However, all the anaesthetics appeared to be suitable for performing minor surgery in the field. 相似文献
118.
Propofol as an intravenous anaesthetic agent in dogs 总被引:1,自引:0,他引:1
Studies in dogs with an emulsion formulation of the intravenous anaesthetic, propofol, showed that induction of anaesthesia was smooth and it was possible to maintain anaesthesia by intermittent injection. The mean dose for induction of anaesthesia in unpremedicated dogs was 5.95 mg/kg body-weight. When no premedication was administered anaesthesia was maintained by a total dose of approximately 0.806 mg/kg/minute. Premedication with between 0.02 and 0.04 mg/kg of acepromazine reduced the mean induction dose by about 30 per cent and the maintenance dose by more than 50 per cent. In 68 unpremedicated dogs given one dose, recovery was complete in a mean time of 18 minutes and after maintenance of anaesthesia by intermittent injection in 65 dogs the mean recovery time was 22 minutes from administration of the last dose. Premedication with acepromazine did not produce statistically significant increases in these recovery times. The quiet, rapid and complete recovery proved to be most valuable in cases where the animal had to be returned to the owners' care with the minimum of delay. 相似文献
119.
Y Gu A P Schinckel T G Martin J C Forrest C H Kuei L E Watkins 《Journal of animal science》1992,70(6):1708-1718
Carcasses of 181 barrows, representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), and two levels of ractopamine (RAC) treatment (0 and 20 ppm) were completely dissected and the data were used to examine genotype and treatment (RAC) biases in estimation of fat-standardized lean weight and to evaluate accuracies and precisions realized by use of equations based on variables derived from different technologies. Independent variables used to establish regression equations represented technologies of direct carcass measurements, optical probe data, TOBEC (total body electrical conductivity) readings, and dissected (DHMLN) and fat-standardized (FSHMLN) ham lean. Genotype bias existed when any equation from a single technology was used and was minimized by combining FSHMLN with one TOBEC reading, carcass length, and the probe measurement of 10th rib fat depth. Large RAC biases appeared when equations from direct carcass measurements or optical probe data were used and were minimized by an equation using either DHMLN or FSHMLN. A practical equation with relatively high R2 value and small genotype and RAC biases were developed by combining TOBEC readings with direct carcass measurements of 10th rib fat depth and warm carcass weight. 相似文献
120.
Insecticide-resistant mosquito fish (Gambusia affinis) were found to be slightly more tolerant to two thiol esters of 2,4-dichlorophenoxyacetic acid (2,4-D) than were fish of a susceptible population. DEF (S,S,S,-tributyl phosphorotrithioate), at 0.1 ppm for 24 hr, slightly decreased the toxicity of both esters to both populations. Comparison of esterase activities in gill and liver preparations showed that the resistant fish had lower levels of liver esterases than the susceptible fish, but results with gill preparation were not consistent. With the ethyl thiol ester, susceptible fish had the higher activity, but with butyl thiol ester, resistant fish had the higher activity. DEF inhibited activities in both tissues of both populations, but inhibition was appreciably greater in the liver. Results suggest that (i) hydrolysis in the liver activaties 2,4-D esters, (ii) hydrolysis in the gill is a detoxication reaction, (iii) the slight increase in tolerance in the insecticide-resistant fish is primarily the result of decreased activation, and (iv) antagonism by DEF is the result of a greater inhibition of activation than of detoxication. 相似文献