全文获取类型
收费全文 | 82176篇 |
免费 | 4040篇 |
国内免费 | 57篇 |
专业分类
林业 | 4007篇 |
农学 | 2507篇 |
基础科学 | 424篇 |
8975篇 | |
综合类 | 16427篇 |
农作物 | 3314篇 |
水产渔业 | 3729篇 |
畜牧兽医 | 40846篇 |
园艺 | 1067篇 |
植物保护 | 4977篇 |
出版年
2018年 | 992篇 |
2017年 | 1047篇 |
2016年 | 981篇 |
2015年 | 897篇 |
2014年 | 1086篇 |
2013年 | 2846篇 |
2012年 | 1977篇 |
2011年 | 2449篇 |
2010年 | 1577篇 |
2009年 | 1458篇 |
2008年 | 2343篇 |
2007年 | 2405篇 |
2006年 | 2182篇 |
2005年 | 2106篇 |
2004年 | 2005篇 |
2003年 | 2035篇 |
2002年 | 1945篇 |
2001年 | 2298篇 |
2000年 | 2315篇 |
1999年 | 1950篇 |
1998年 | 762篇 |
1997年 | 747篇 |
1995年 | 852篇 |
1993年 | 746篇 |
1992年 | 1535篇 |
1991年 | 1614篇 |
1990年 | 1732篇 |
1989年 | 1697篇 |
1988年 | 1569篇 |
1987年 | 1525篇 |
1986年 | 1589篇 |
1985年 | 1562篇 |
1984年 | 1300篇 |
1983年 | 1193篇 |
1982年 | 807篇 |
1981年 | 747篇 |
1979年 | 1277篇 |
1978年 | 1008篇 |
1977年 | 878篇 |
1976年 | 821篇 |
1975年 | 939篇 |
1974年 | 1229篇 |
1973年 | 1271篇 |
1972年 | 1288篇 |
1971年 | 1204篇 |
1970年 | 1124篇 |
1969年 | 1018篇 |
1968年 | 875篇 |
1967年 | 919篇 |
1966年 | 854篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
Lavigne C Smith HJ 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(12):389-390,391
In 1982, approximately 13,000 Canadian cattle were treated once for sarcoptic mange with ivermectin at a dose of 10 mg per 45.4 kg of body weight. The results showed 100% efficacy against Sarcoptes scabiei and other ectoparasites present. All cattle showed marked improvement in general condition with new hair growth and apparent weight gains by 31 days posttreatment. Surveillance of treated herds for a year following treatment showed that one parenteral treatment with ivermectin eradicated the disease from closed herds. 相似文献
143.
144.
Kinematics of the equine thoracolumbar spine 总被引:2,自引:0,他引:2
At least three types of movement take place in the joint complexes of the equine thoracolumbar spine: dorsoventral flexion and extension, axial rotation and lateral bending. Using the standard right-handed Cartesian coordinate system, these movements may be defined as rotation about the x, y and z axes respectively. Except in cases of intervertebral fusion, all three types of movement occur in each joint complex of the equine back. The greatest amount of dorsoventral movement takes place at the lumbosacral and the first thoracic intervertebral joints. The greatest amount of axial rotation and lateral bending was measured in the mid-thoracolumbar spine at the level of the 11th or 12th thoracic intervertebral joints. The caudal thoracic and the lumbar spine is the least mobile region of the equine back. In the mid-thoracic spine, lateral bending was always accompanied by a "coupled" axial rotation. The presence of the rib cage stabilised the cranial thoracic vertebrae against axial rotation. 相似文献
145.
L. Bos N. Huijberts H. Huttinga D. Z. Maat 《European journal of plant pathology / European Foundation for Plant Pathology》1983,89(5):207-222
A damaging virus isolated in the Netherlands from lettuce was studied and compared with a virus isolated from dandelion orginating from Czechoslovakia. It was found to biologically resemble dandelion yellow mosaic virus incompletely described from dandelion and lettuce in Great Britain (Kassanis, 1944, 1947) and from dandelion in Germany (Hein, 1963). Mechanical transmission was greatly improved by buffer solution and transmission byMyzus persicae seemed to be in the non-persistent manner. Longevity in vitro of the virus hardly exceeded one day. Thermal inactivation was between 60 and 65 °C and the dilution end-point was between 10 000 and 100 000. It was still infectious in leaf material dried and stored over CaCl2 at 4 °C for 6 1/2 years. The virus was isolated and purified with difficulty and was found to consist of one type of spherical particle of ca 30 nm diameter, with a sedimentation coefficient of 159 S, a buoyant density of 1.42 g.cm?3 and an A260/A280 ratio of 1.67. An antiserum was prepared with a titre of 256 in the agar double-diffusion test. The virus could be identified in crude extracts from lettuce andChenopodium amaranticolor by enzyme-linked immunosorbent assay (ELISA), but not by agar double diffusion. It could only be visualized in crude sap in the electron microscope after trapping of virus particles on antiserum-coated grids. The virus cannot yet be assigned to any known virus group. It is of potential economic importance to lettuce because of its occurrence in widely differing regions in Europe, its aggressiveness and virulence on 22 out of 23 lettuce cultivars tested (and on endive) and its pathogenicity toLactuca genotypes which are resistant to lettuce mosaic virus and other important pathogens of lettuce. ‘Laibacher Eis’ was the only cultivar showing some tolerance. 相似文献
146.
147.
148.
149.
150.
McMurphy RM Cribb PH 《The Canadian veterinary journal. La revue veterinaire canadienne》1989,30(1):37-41
This study was designed to investigate the effect of the nasotracheal insufflation of oxygen at a flow rate of 15 L/min on the arterial partial pressure of oxygen during the recovery period following inhalation anesthesia in the horse. It has been stated that this is a suitable flow rate to prevent postoperative hypoxemia but without any experimental evidence to support those statements. Horses being used for the study of healing of cartilage were anesthetized on two separate occasions. Following one period of anesthesia they were allowed to recover breathing room air, and following the other period of anesthesia oxygen was insufflated into the trachea at 15 L/min throughout the recovery period. This permitted each horse to act as its own control and allowed statistical analysis using Student's t-test for paired samples.
The insufflated horses had a higher arterial partial pressure of oxygen during the recovery period than did the noninsufflated horses (p < 0.05).
相似文献