全文获取类型
收费全文 | 8207篇 |
免费 | 418篇 |
国内免费 | 9篇 |
专业分类
林业 | 588篇 |
农学 | 283篇 |
基础科学 | 62篇 |
1387篇 | |
综合类 | 1234篇 |
农作物 | 543篇 |
水产渔业 | 647篇 |
畜牧兽医 | 3022篇 |
园艺 | 215篇 |
植物保护 | 653篇 |
出版年
2023年 | 47篇 |
2022年 | 73篇 |
2021年 | 138篇 |
2020年 | 151篇 |
2019年 | 174篇 |
2018年 | 154篇 |
2017年 | 148篇 |
2016年 | 172篇 |
2015年 | 130篇 |
2014年 | 183篇 |
2013年 | 343篇 |
2012年 | 410篇 |
2011年 | 563篇 |
2010年 | 319篇 |
2009年 | 298篇 |
2008年 | 549篇 |
2007年 | 502篇 |
2006年 | 511篇 |
2005年 | 539篇 |
2004年 | 442篇 |
2003年 | 480篇 |
2002年 | 420篇 |
2001年 | 92篇 |
2000年 | 87篇 |
1999年 | 100篇 |
1998年 | 85篇 |
1997年 | 76篇 |
1996年 | 67篇 |
1995年 | 89篇 |
1994年 | 86篇 |
1993年 | 73篇 |
1992年 | 56篇 |
1991年 | 54篇 |
1990年 | 63篇 |
1989年 | 45篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 48篇 |
1985年 | 50篇 |
1984年 | 49篇 |
1983年 | 47篇 |
1982年 | 32篇 |
1981年 | 25篇 |
1980年 | 34篇 |
1979年 | 29篇 |
1978年 | 37篇 |
1977年 | 39篇 |
1976年 | 35篇 |
1975年 | 39篇 |
1974年 | 30篇 |
排序方式: 共有8634条查询结果,搜索用时 10 毫秒
51.
To determine whether amino acid sequence variation exists in the Moraxella bovis (M. bovis) cytotoxin (MbxA) from geographically diverse M. bovis isolated in the United States, mbxA was amplified and sequenced. The MbxA deduced amino acid sequence from M. bovis originally isolated in California, Washington, North Carolina, and Georgia, as well as reference strains of M. bovis isolated at the National Animal Disease Laboratory, Ames, IA, USA, all encoded a nearly identical 927 amino acid protein. MbxA from two of the four California isolates (SFS 9a and SFS 100a) differed from all other isolates at two sites at which the polar amino acids glutamine (position 666) and asparagine (position 823) were replaced by ionized amino acids glutamic acid and aspartic acid, respectively. Rabbit antiserum to the expressed carboxy terminus (amino acids 590-927) of MbxA from M. bovis (Tifton I) neutralized the hemolytic activity of SFS 9a and SFS 100a. The M. bovis cytotoxin appears to be conserved amongst geographically diverse isolates of M. bovis from the USA. Antiserum against the carboxy terminus of MbxA common to the majority of isolates neutralized the hemolytic activity of two strains with a divergent MbxA deduced amino acid sequence. Vaccines against IBK that incorporate MbxA as antigen may offer protection against geographically diverse strains of M. bovis. 相似文献
52.
Ritter MJ Perry RL Olivier NB Kim SY Dejardin LM 《Journal of the American Animal Hospital Association》2007,43(2):93-98
A novel technique was developed to estimate the caudal medial tibial plateau landmark in the face of osteophytosis to improve accuracy in tibial plateau angle measurements. Using this technique, tibial plateau angles were evaluated in 31 normal dogs before and 8 months after right cranial cruciate ligament transection. There was no significant difference in mean tibial plateau angle before or after induction of osteophytosis. Additionally, it was determined that 90% of dogs had a difference of =2 degrees between right and left tibial plateau angles, which was considered symmetrical. 相似文献
53.
Brito LF Barth AD Rawlings NC Wilde RE Crews DH Mir PS Kastelic JP 《Domestic animal endocrinology》2007,33(1):1-18
The objective of the present study was to characterize the effects of nutrition on circulating concentrations of metabolic hormones, gonadotropins, and testosterone during sexual development in bulls. Nutrition regulated the hypothalamus-pituitary-testes axis through effects on the GnRH pulse generator in the hypothalamus and through direct effects on the testes. Pituitary function (gonadotropin secretion after GnRH challenge) was not affected by nutrition. However, nutrition affected LH pulse frequency and basal LH concentration during the early gonadotropin rise (10-26 weeks of age). There were close temporal associations between changes in insulin-like growth factor-I (IGF-I) concentrations and changes in LH pulse frequency, suggesting a role for IGF-I in regulating the early gonadotropin rise in bulls. The peripubertal increase in testosterone concentration was delayed in bulls with lesser serum IGF-I concentrations (low nutrition), suggesting a role for IGF-I in regulating Leydig cell function. Serum IGF-I concentrations accounted for 72 and 67% of the variation in scrotal circumference and paired-testes volume, respectively (at any given age), indicating that IGF-I may regulate testicular growth. Bulls with a more sustained elevated LH pulse frequency during the early gonadotropin rise (high nutrition) had greater testicular mass at 70 weeks of age relative to the control group (medium nutrition), despite no differences in metabolic hormone concentrations after 26 weeks of age. Therefore, gonadotropin-independent mechanism regulating testicular growth might be dependent on previous gonadotropin milieu. 相似文献
54.
Schmitz JA Vogt RJ Rupp GP Brodersen BW Abel JM Wohlers AR Marx DB 《Journal of veterinary medical education》2007,34(3):340-349
Nebraska veterinary practitioners were surveyed to collect data about background characteristics and other factors related to veterinarians' decision to include or not include food animals in their practices and to practice in rural versus urban communities. Background characteristics that were significantly (p < or = 0.05) associated with choosing food-animal practice included growing up on a working farm or ranch; having parents who owned livestock; growing up in a town with a population of less than 10,000; majoring in animal science at university; being male; and having a primary interest, at the time of entering veterinary college, in food animal-exclusive or mixed-animal veterinary practice. The primary factor for choosing the community in which to practice was rural/urban lifestyle for rural veterinarians, while this factor was second for urban veterinarians. For all groups of veterinarians, the primary consideration in selecting their current practice was the species orientation of the practice. The primary reason for not choosing food-animal practice was better working conditions and lifestyle in companion-animal practice, followed by greater interest elsewhere. 相似文献
55.
Since its detection in 2001 the human Metapneumovirus (HMPV), a member of the Paramyxoviridae family, was observed to be a serious pathogen in human respiratory infections during childhood. Meanwhile, several animal models have been established to study the virus-host interactions and pathogenic effects. Mainly, small laboratory animals like mice and cotton rats have been used, although the usage of these two species for HMPV research is controversially discussed and contradictious results were obtained by different groups. Further trials with ferrets, hamsters and non human primates were performed revealing different success in their individual usage. In this review we present the different animal models, summarize their advantages and disadvantages, and discuss the controversial results from different studies. 相似文献
56.
57.
58.
59.
60.
A 5-year-old Quarter Horse mare was presented to the Michigan State University Equine Surgery Service for evaluation of a right hind metatarsophalangeal joint injury. On presentation, the horse was a grade 4/5 lame. Radiographs and ultrasonography showed peritendinous ossification/mineralisation of soft tissue structures and digital flexor tenosynovitis with profound intracapsular mineralisation. A digital flexor tendon sheath tenoscopy was performed with a plantar annular ligament desmotomy and a manica flexoria ligament tenotomy. During surgery, a significant amount of tan granular material was found within the digital tendon sheath. Approximately 80% of this material was removed, and a sample was sent for histopathology. The horse was diagnosed with eosinophilic granulomatous tenosynovitis. Long-term follow-up revealed improvement with four treatments of intralesional triamcinolone given 2–4 weeks apart. The horse became serviceably sound (grade 1/5) and was beginning light work under the saddle approximately 5 months post-tenoscopy. 相似文献