全文获取类型
收费全文 | 355283篇 |
免费 | 18541篇 |
国内免费 | 1037篇 |
专业分类
林业 | 25630篇 |
农学 | 14852篇 |
基础科学 | 3180篇 |
50450篇 | |
综合类 | 53242篇 |
农作物 | 18219篇 |
水产渔业 | 19389篇 |
畜牧兽医 | 156058篇 |
园艺 | 6738篇 |
植物保护 | 27103篇 |
出版年
2019年 | 3947篇 |
2018年 | 4872篇 |
2017年 | 5375篇 |
2016年 | 5414篇 |
2015年 | 4763篇 |
2014年 | 6166篇 |
2013年 | 16825篇 |
2012年 | 9331篇 |
2011年 | 12051篇 |
2010年 | 8956篇 |
2009年 | 9224篇 |
2008年 | 11270篇 |
2007年 | 10628篇 |
2006年 | 10608篇 |
2005年 | 9847篇 |
2004年 | 9570篇 |
2003年 | 9436篇 |
2002年 | 8690篇 |
2001年 | 9651篇 |
2000年 | 9417篇 |
1999年 | 8102篇 |
1998年 | 4561篇 |
1997年 | 4597篇 |
1996年 | 4337篇 |
1995年 | 4977篇 |
1994年 | 4391篇 |
1993年 | 4085篇 |
1992年 | 6500篇 |
1991年 | 6790篇 |
1990年 | 6699篇 |
1989年 | 6701篇 |
1988年 | 6043篇 |
1987年 | 6067篇 |
1986年 | 6056篇 |
1985年 | 6066篇 |
1984年 | 5280篇 |
1983年 | 4810篇 |
1982年 | 3650篇 |
1981年 | 3445篇 |
1980年 | 3361篇 |
1979年 | 4798篇 |
1978年 | 4032篇 |
1977年 | 3616篇 |
1976年 | 3476篇 |
1975年 | 3536篇 |
1974年 | 4038篇 |
1973年 | 4076篇 |
1972年 | 3854篇 |
1971年 | 3648篇 |
1970年 | 3612篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
A W vd Giessen R Peters P A Berkers W H Jansen S H Notermans 《The Veterinary quarterly》1991,13(1):41-46
The contamination of poultry in the Netherlands with Salmonella enteritidis was tested. For this, different methods (detection of S. enteritidis in faecal samples of 25 g; detection of S. enteritidis in cloacal swabs; detection of S. enteritidis by serological testing of antibodies in serum) were compared for their efficiency to detect S. enteritidis in flocks of poultry. Testing of faecal samples clearly yielded the best results. This method was used in a transmission study, in which 14 flocks descending from a contaminated primary mother flock were screened for the presence of S. enteritidis. The method was also used for screening 49 flocks of laying hens and 52 flocks of broiler chickens throughout the Netherlands. From the transmission study it became clear that S. enteritidis, phage type 2 (Dutch phage set) was isolated both from the mother flock and from five of the descendent flocks. Screening of poultry flocks for the presence of salmonella revealed that salmonella was present in 47% of the layer flocks and in 94% of the broiler flocks. S. enteritidis was isolated from 15% of the flocks screened. 相似文献
942.
A P Davidson 《Veterinary Clinics of North America: Small Animal Practice》2001,31(2):411-420
The practice of small animal theriogenology is rewarding, but frustrations exist concerning technologic advances as compared with other species. Reproductive clinicians striving to practice good quality medicine readily identify topics of common concern: causes that are not identified or therapeutics that are not available or applicable. Improved collaboration among theriogenologists specializing in small animal practice is evidenced by growing attendance at national and international scientific meetings, increased scientific publications, and internet communications. 相似文献
943.
C A Leonard M Tillson 《Veterinary Clinics of North America: Small Animal Practice》2001,31(1):143-63, vii
Feline lameness is an increasingly recognized clinical problem. Today's veterinary practitioner must be comfortable with his/her ability to diagnose the various conditions responsible for lameness in the cat and be able to discuss the significance of their findings with the client. Disease of the feline musculoskeletal system can be grouped into broad categories, including: trauma, arthritis, infectious causes, developmental disorders, neoplasia, and muscular problems. Specific diseases from each of these categories will be discussed, particularly those that differ in their presentation or clinical behavior from that same disease in the canine patient. 相似文献
944.
Y Sugawara K Hirasawa M Takeda J S Han K Doi 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1991,53(3):463-468
One-month-old Syrian hamsters of the APA and Std: golden strains were inoculated intraperitoneally with 10(5) PFU/head of the D variant of encephalomyocarditis (EMC) virus and examined virologically and pathologically up to 7 days after inoculation. APA hamsters developed apparent hyperglycemia due to pancreatic islet cell damage while Std:golden hamsters did not. Hamsters of both strains showed clear histopathologic changes in the testis with prominent viral replication as well as in the brain, heart and exocrine pancreas. The susceptibility to EMC virus-infection was higher in males than in females and in APA than in Std: golden hamsters. 相似文献
945.
L.E. Young D.H. Bartram M. Diamond A. Gregg R.S. Jones 《Veterinary anaesthesia and analgesia》1991,18(Z1):171-174
946.
947.
948.
The association between ocular squamous cell tumors and various measures of solar radiation was evaluated for 2,775 contemporaneous Hereford cattle. The animals were from 34 herds located in 21 states in the United States and in one Canadian province. Examinations and photographs were made of the eyes of all cows and heifers in a herd; 33 herds were examined between June and August 1957 and 1 herd was examined in 1958. Solar radiation was measured by altitude and mean annual hours of sunshine applying to an individual herd, and global radiation, a cloudiness index, and elevation of nearby National Weather Service stations. All measures of solar radiation provided evidence of a significant association between increasing risks of developing cancer eye and increasing levels of radiation; adjustments were made for possible confounding effects of age and corneoscleral pigmentation. Associations were evident whether affliction was defined as the occurrence of any type of tumor (ie, plaque, papilloma, or carcinoma), or as the occurrence of only papilloma or carcinoma. Average ages of affected cattle also tended to be lower at high radiation levels than at low levels, further supporting the hypothesis that solar radiation has an important role in the development of this disease. In view of the heritability of eye pigmentation and its inhibitory effect on lesions, cancer eye may be controlled by selective breeding for increased pigmentation in and around the eye to afford protection against the harmful effects of incident UV radiation. 相似文献
949.
950.
Intracavitary Cisplatin Chemotherapy Experience with Six Dogs 总被引:1,自引:0,他引:1
Antony S. Moore MVSc Claudia Kirk DVM Aglaia Cardona DVM 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1991,5(4):227-231
Six dogs with a median age of 7 years (range = 5-14 years) were presented for signs referable to thoracic or abdominal effusion associated with neoplasia of the body cavities. Intracavitary cisplatin was administered at 50 mg/m2 every 4 weeks for a median of 2.5 treatments (mean = 3, range = 1-6). Three dogs with pleural mesothelioma had complete resolution of effusion for 289, 129, and greater than 306 days without evidence of tumor growth. Resolution of effusion occurred after one treatment in two dogs and after two treatments in one dog. In three dogs with carcinomatosis of unknown origin, complete responses was seen in two dogs after one treatment for 255 and greater than 807 days, respectively. Intracavitary chemotherapy with cisplatin was associated with palliation and control of malignant pleural and/or abdominal effusion in five of six dogs. Toxicity was minimal, and this method of therapy should be further explored in dogs with similar malignancies. 相似文献