全文获取类型
收费全文 | 144279篇 |
免费 | 8372篇 |
国内免费 | 858篇 |
专业分类
林业 | 5897篇 |
农学 | 4167篇 |
基础科学 | 1060篇 |
16756篇 | |
综合类 | 29113篇 |
农作物 | 5523篇 |
水产渔业 | 6546篇 |
畜牧兽医 | 74144篇 |
园艺 | 1836篇 |
植物保护 | 8467篇 |
出版年
2019年 | 1515篇 |
2018年 | 2153篇 |
2017年 | 2426篇 |
2016年 | 2150篇 |
2015年 | 1990篇 |
2014年 | 2363篇 |
2013年 | 5006篇 |
2012年 | 4411篇 |
2011年 | 5397篇 |
2010年 | 3519篇 |
2009年 | 3481篇 |
2008年 | 5029篇 |
2007年 | 4783篇 |
2006年 | 4405篇 |
2005年 | 4172篇 |
2004年 | 3858篇 |
2003年 | 4013篇 |
2002年 | 3661篇 |
2001年 | 4266篇 |
2000年 | 4354篇 |
1999年 | 3376篇 |
1998年 | 1352篇 |
1997年 | 1286篇 |
1996年 | 1252篇 |
1995年 | 1402篇 |
1993年 | 1275篇 |
1992年 | 2713篇 |
1991年 | 3059篇 |
1990年 | 2941篇 |
1989年 | 2871篇 |
1988年 | 2615篇 |
1987年 | 2730篇 |
1986年 | 2805篇 |
1985年 | 2656篇 |
1984年 | 2167篇 |
1983年 | 1877篇 |
1979年 | 2006篇 |
1978年 | 1575篇 |
1977年 | 1312篇 |
1976年 | 1256篇 |
1975年 | 1384篇 |
1974年 | 1840篇 |
1973年 | 1809篇 |
1972年 | 1809篇 |
1971年 | 1711篇 |
1970年 | 1659篇 |
1969年 | 1553篇 |
1968年 | 1312篇 |
1967年 | 1394篇 |
1966年 | 1286篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
C Richardson W P Taylor S Terlecki E P Gibbs 《American journal of veterinary research》1985,46(9):1912-1922
Twenty-four ewes were inoculated with 1 of 2 strains of bluetongue virus type 4 at 40, 60, or 80 days of gestation. Two ewes aborted, 2 ewes died, and 1 was killed during the experiment, but their fetuses were recovered. At term, 2 mummified fetuses, 4 dead lambs, and 17 clinically healthy lambs were produced by 12 sheep, and the remaining 7 sheep were barren. Porencephaly and cerebellar dysgenesis were found in term lambs born to sheep inoculated at 40 and 60 days of gestation. Radiographic examination of 12 fetuses showed developmental ages far less than their chronologic age; 8 fetuses had skeletal growth-retardation lines, which were also observed in the dead lambs. A systemic lymphoreticular hyperplasia was observed in the dead lambs and in all lambs at 12 weeks of age; in 4 of the latter, granulomatous reactions were present in the liver and kidney. Lungs of the full-term lambs were reduced in weight and showed poor alveolar development and mononuclear cell infiltration, which persisted in the 12-week-old lambs. It was concluded that bluetongue virus is capable of causing not only gross abnormalities of the CNS, but also generalized growth retardation and fetal lymphoreticular hyperplasia. 相似文献
85.
Antigens in the extracellular protein (ECP) complexes of Bacteroides nodosus, isolated from sheep with either benign or virulent footrot, were studied by immunoelectrophoresis (IEP). Rabbit antisera against ECP from virulent and benign strains, were used in homologous and heterologous crossed IEP. Four precipitin peaks unique to the virulent strain, and five peaks unique to the benign strain were identified. In an attempt to characterize the different antigens in ECP, rabbit antisera were raised against an outer membrane protein (OMP, mol. wt. 35 000 daltons), pili and various proteases of virulent and benign strains of B. nodosus. No precipitin band was observed when ECP from both B. nodosus strains were reacted against anti-OMP and anti-pilus antisera. However, single precipitin bands unique to one protease from the benign strain and one protease from the virulent strain were identified. The results suggest that specific antigens other than proteases or pili are important in determining whether a B. nodosus isolate is virulent or benign. 相似文献
86.
Isolated dog neutrophils exposed to known chemotactic factors assumed a bipolar configuration in suspension. This response was initiated within 2 minutes with a gradual return to spherical shape. The rate of return to sphere was positively correlated with the dose of stimulant. Dog neutrophils exposed to N-formylmethionyl-leucyl-phenylalanine (fMLP) did not adapt to bipolar conformation and did not bind radiolabeled fMLP. These findings are consistent with other species (pig and cow) that also did not respond to fMLP. 相似文献
87.
L Klein 《Veterinary Clinics of North America: Equine Practice》1985,1(1):77-89
A brief discussion of those aspects of neonatal physiology that pertain to anesthetic risk and selection of anesthetic techniques is followed by discussion of suggested techniques for anesthetic management in healthy foals. Preoperative preparation and management of foals with selected serious surgical conditions are also considered. 相似文献
88.
C A Osborne T D O'Brien H K Ghobrial L Meihak J B Stevens 《Veterinary Clinics of North America: Small Animal Practice》1986,16(1):45-65
Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis. 相似文献
89.
Twenty stifles (10 dogs) were studied for a period of 1 year after various lesions of the cranial cruciate ligament and medial meniscus were produced surgicaoy. Through serial arthroscopic evaluations, degenerative processes In stifles with a "torn" cranial cruciate ligament were documented. Intra-articular changes were minimal after partial meniscectomy and were severe after total meniscectomy. Multiple arthroscopies caused no demonstrable changes. 相似文献
90.
A steam-dryer, designed and manufactured in Sweden, was evaluated for destroying Bursaphelenchus xylophilus in pine chips from southern USA. In a trial, pine chips were treated at different temperature and pressure regimes for 5 or 10min. The lowest time/temperature/pressure combination was to increase the vessel temperature from 85 to 104°C in 5 min at low pressure. Samples of pine chips were assayed for nematodes in laboratories in USA, Sweden, and Finland. No nematodes of any species were recovered from any of the treated pine-chip samples. Large and heterogeneous pieces of wood in the treated samples were also nematode-free. The apparatus was a prototype capable of handling about 400 kg h-1 . The final version would have to be able to process 100-200 th-1 . 相似文献