全文获取类型
收费全文 | 502篇 |
免费 | 28篇 |
专业分类
林业 | 34篇 |
农学 | 9篇 |
基础科学 | 1篇 |
77篇 | |
综合类 | 103篇 |
农作物 | 15篇 |
水产渔业 | 41篇 |
畜牧兽医 | 181篇 |
园艺 | 13篇 |
植物保护 | 56篇 |
出版年
2023年 | 4篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 24篇 |
2012年 | 26篇 |
2011年 | 29篇 |
2010年 | 14篇 |
2009年 | 11篇 |
2008年 | 39篇 |
2007年 | 31篇 |
2006年 | 19篇 |
2005年 | 32篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 37篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1947年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有530条查询结果,搜索用时 625 毫秒
81.
Barry SL Lafuente MP Martinez SA 《Journal of the American Veterinary Medical Association》2008,232(6):886-888
CASE DESCRIPTION: A 3-year-old spayed female Labrador Retriever was evaluated for progressive lameness of the left forelimb 21 months after being shot in the elbow with a lead bullet. CLINICAL FINDINGS: Physical examination findings were consistent with moderate osteoarthritis of the left elbow joint. Orthogonal radiographic views of the elbow revealed multiple metallic fragments in and around the joint space as well as signs of osteoarthritis. TREATMENT AND OUTCOME: The elbow joint was evaluated arthroscopically. A lead-based bullet fragment was seen in the lateral synovial compartment and removed in multiple pieces. Excess fibrin and synovium were removed, and microfractures were created in exposed subchondral bone to stimulate neovascularization and fibrocartilage formation. In a follow-up telephone conversation 4 months after surgery, the owner reported a marked improvement in the lameness. CLINICAL RELEVANCE: Removal of lead intra-articular foreign bodies may be indicated even if the material is not believed to mechanically interfere with joint motion. 相似文献
82.
83.
The aims of this study were: (1) to examine whether or not enterohemorrhagic Escherichia coli O26 and O111 (EHEC O26 and O111) are involved in neonatal calf diarrhea; (2) to determine the specific age periods at which the calves are vulnerable to these organisms, and (3) to reveal the biochemical, genetic and cytotoxic characteristics of the isolates. The study investigated the occurrence of EHEC O26 and O111 in calves associated with or without diarrhea. A total of 442 diarrheic and non-diarrheic young calves from 115 different farms were examined. Of the 257 calves with diarrhea, 37 (14.4%) and 32 (12.5%) tested positive for EHEC O26 and EHEC O111, respectively. Of the 185 non-diarrheic calves, 14 (7.6%) and 11 (5.9%) tested positive for EHEC O26 and EHEC O111, respectively. EHEC O26 and O111 were recovered from 14/69 (20%) and 11/69 (16%) diarrheic calves <2-weeks-old, respectively, and no EHEC O26 and O111 were detected in the non-diarrheic claves of this age group, suggesting that EHEC O26 and O111 are possible causes of the disease in infected neonatal calves. However, there were similar rates of occurrence in the diarrheic and non-diarrheic calves in the older animals (particularly, aged >10 weeks). PCR analysis showed that the isolates carried various virulence genes such as Ehly, eae, stx1 and stx2, which highlight the potential importance of these attributes for the infection, colonization and the possible pathogenesis of calf diarrhea. Cytotoxicity analysis revealed that many of the EHEC isolates showed high cytotoxicity to Vero cells, re-emphasizing the potential for cattle being a direct source of EHEC infections in humans. 相似文献
84.
85.
Influence of nitrogen,photoperiod, cutting type,and clone on root and shoot development of rooted stem cuttings of sweetgum 总被引:1,自引:1,他引:0
Rieckermann Heidi Goldfarb Barry Cunningham Michael W. Kellison Robert C. 《New Forests》1999,18(3):231-244
This study was designed to test the effects of nitrogen fertilization, photoperiod, cutting type, and clone on root and shoot development of stem cuttings of sweetgum (Liquidambar styraciflua). Differences in the growth of roots and shoots were observed as a result of weekly applications of varying levels of nitrogen (N) fertilization (0, 25, 50, 100, or 200 mg N/liter). As the concentration of N increased, new-shoot dry weight increased, but root dry weight decreased at rates greater than 50 mg N/liter. The percentage of rooted cuttings surviving also decreased as N concentrations increased past 50 mg N/liter. A night-interruption light treatment did not significantly affect survival percentages or the amount of root and shoot growth. Across all treatments, only 46% of all cuttings produced new-shoot growth within a 15-week period following rooting. Cutting type (terminal or sub-terminal) affected rooted cutting development. A higher percentage of terminal cuttings survived and were deemed plantable. In contrast, sub-terminal cuttings produced more shoot and root growth. Differences among clones were observed for all traits measured.Manipulating N fertilization, in conjunction with using clones that propagate well, has the potential of producing rooted cuttings of a size adequate for plantation establishment. However, higher percentages of cuttings that produce new shoot growth shortly after rooting must be achieved. 相似文献
86.
利用 Northern 杂交和核酸保护分析(RPA)检测了番茄ACC 合成酶(ACS)和 ACC氧化酶(ACO)基因家族在番茄突变体Epinastics (Epi)果实中的表达特性,同时测定了Epi果实自动催化乙烯合成系统的特性⒚EPI等位基因的突变诱导了LEACS2 和LEACO1 两个基因的过表达,这是Epi果实的乙烯过表达的主要成因⒚EPI突变同时显著抑制了LEACS4 和 LEACO3 的表达强度⒚这些结果初步鉴别了这两个基因家族在番茄果实上表达的各个成员的转录调节途径⒚同时表明,番茄单基因乙烯反应突变体是研究ACS和ACO基因家族各成员转录调节特性的一种有用工具⒚ 相似文献
87.
88.
Synthesis and evaluation of hydroxyazolopyrimidines as herbicides; the generation of amitrole in planta
下载免费PDF全文
![点击此处可从《Pest management science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
89.
Danilo T. Stipp Aline F. Barry Alice F. Alfieri Elisabete Takiuchi Alexandre M. Amude Amauri A. Alfieri 《Tropical animal health and production》2009,41(7):1563-1567
Bovine coronavirus (BCoV) is one of the main causes of neonatal calf diarrhoea. Several diagnostic assays have been employed
to detect the presence of the virus in stool samples from calves. Despite this, the frequency of BCoV infection among Brazilian
and even South American cattle herds has yet to be well characterised. This study describes the occurrence of BCoV infection
among calves from dairy and beef herds in four Brazilian states. A total of 282 stool samples from 1 to 60-day-old calves
were evaluated for the presence of BCoV by a semi-nested (SN) PCR assay. The animals were from herds (n = 23) located in three geographical regions in Brazil (south, southeast, and center-west). The specific BCoV amplicon was
detected in 15.6% (44/282) of the faecal specimens examined, of which 95.4% (42/44) were from diarrhoeic and 4.6% (2/44) from
asymptomatic calves. The specificity of the SN-PCR amplicons was evaluated by restriction fragment length polymorphism (RFLP)
analysis. The results show that the BCoV is widespread, mainly among calves from 16 to 30-days-old (p = 0.0023), and verify the association between BCoV infection and clinical signs of diarrhoea (p = 0.005). These findings emphasise the importance of this virus in enteric infections of Brazilian cattle herds. 相似文献
90.
John Moore Alexis Achim Andrew Lyon Shaun Mochan Barry Gardiner 《Forest Ecology and Management》2009,258(7):1174-1180
The effects of early re-spacing on the physical and mechanical properties of Sitka spruce (Picea sitchensis [Bong.] Carr.) structural-dimensioned timber were studied using material from a fully replicated 57-year-old trial located in Northern Ireland, which had been thinned at age 11 years. Basic density, distortion (spring, twist and bow), modulus of elasticity (MOE) and modulus of rupture (MOR) in bending of structural timber from four different re-spacing treatments (1.83 m × 3.66 m, 3.66 m × 3.66 m, 3.66 m × 5.49 m and 5.49 m × 5.49 m) were compared with those of timber from a control (1.83 m × 1.83 m). Re-spacing intensity had a significant effect on both modulus of elasticity (p = 0.006) and modulus of rupture (p = 0.009), but not on basic density (p = 0.379) or distortion (p > 0.200). Timber from the two widest re-spacing treatments failed to meet the requirements for the C14 strength class, while timber from the control met the requirements for the C16 strength class. Both MOE and MOR were significantly and negatively associated with knot size and frequency, which in turn increased with re-spacing intensity. Overall, re-spacing intensity only explained approximately 10% of the total amount of variation in both MOE and MOR, with most of the variation due to inter- and intra-tree differences within a treatment. Based on these results, re-spacing of Sitka spruce to a residual stand density of less than 900 trees/ha (3.33 m × 3.33 m) is not recommended if the goal of management is to produce C16 structural timber. 相似文献