首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   159篇
  免费   12篇
林业   3篇
农学   13篇
  30篇
综合类   13篇
农作物   2篇
水产渔业   11篇
畜牧兽医   88篇
园艺   2篇
植物保护   9篇
  2023年   1篇
  2021年   1篇
  2020年   4篇
  2019年   5篇
  2018年   11篇
  2017年   12篇
  2016年   4篇
  2015年   6篇
  2014年   4篇
  2013年   21篇
  2012年   4篇
  2011年   4篇
  2010年   4篇
  2009年   8篇
  2008年   1篇
  2007年   4篇
  2006年   1篇
  2005年   7篇
  2004年   2篇
  2003年   2篇
  2002年   1篇
  2001年   4篇
  2000年   1篇
  1999年   6篇
  1998年   7篇
  1997年   1篇
  1996年   8篇
  1994年   1篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1989年   4篇
  1988年   2篇
  1986年   3篇
  1985年   2篇
  1983年   4篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1971年   2篇
  1969年   1篇
  1964年   1篇
  1957年   1篇
排序方式: 共有171条查询结果,搜索用时 15 毫秒
1.
This study describes the age-related variation in boar taint compounds, skatole and androstenone, and testosterone, oestradiol-17 beta (E17 beta), oestrone sulphate (ES), dehydroepiandrosterone sulphate (DHEAS), triiodothyronine (T(3)) and insulin-like growth factor-1 (IGF-1) in six boars. Three pairs of littermates of crossbred entire male pigs (from three Yorkshire x Duroc dams and one Hampshire sire) were included. Blood samples were taken at the age of 9-15 weeks and thereafter at weekly intervals from the age of 20-32 weeks. Plasma concentrations of skatole, androstenone, testosterone, E17 beta, ES, DHEAS, T(3) and IGF-1 were measured. We found that skatole levels in boars increased at the age around puberty after an increase in the levels of testicular steroids. Levels of skatole were not associated with the levels of sex steroids, T(3) and IGF-1. However, the increased level of testicular steroids is probably the underlying factor needed for high skatole levels to occur although the specific mechanism leading to increased skatole levels remains unknown.  相似文献   
2.
3.
A partial nucleotide sequence of transforming growth factor-beta3 (TGF-beta3) has been isolated from the Siberian sturgeon (Acipenser baeri), rainbow trout (Oncorhynchus mykiss) and European eel (Anguilla anguilla), confirming a ubiquitous presence in the ray-finned (Actinopterygian) bony fish. The bony fish TGF-beta3 is highly conserved, with some 83-84% nucleotide identity (coding region) and 90-95% predicted amino acid identity to known homeotherm TGF-beta3's. Far lower homologies are apparent with other known TGF-beta isoforms in fish (e.g. 64-66% and 81-82% amino acid identity to trout TGF-beta 1/5 and carp TGF-beta2 respectively). Phylogenetic tree analysis showed that the fish TGF-beta3's clustered with the known homeotherm TGF-beta3's. The relatively tight clustering of TGF-beta1, TGF-beta2 and TGF-beta3 was in contrast to the TGF-beta5's, which are clearly a more heterogenous group.  相似文献   
4.
Alum precipitatedBacteroides nodosus vaccines prepared from two antigens with and without the saponin derivative, Quil A, did not induce adverse tissue reactions in sheep injected subcutaneously. Vaccinated, non-infected Merino sheep had higher agglutinin antibody titres when the vaccines included Quil A. Moreover, the recovery rates in vaccinated sheep affected with foot-rot were higher when the vaccines included Quil A.  相似文献   
5.
Following reports of findings of ovine foot-rot flora in the feet of cattle, a study was undertaken to determine the prevalence of Bacteroides nodosus infection in the apparently normal cattle population. We found that 34.5 to 74.2 per cent of the animals examined on different farms had B nodosus present in one or more feet. B nodosus was not the most prevalent bacterium observed in smears from cattle. Other Gram negative species including Fusiformis necrophorus and many Gram positive cocci and coccobacilli were also present. Macroscopic lesions in the interdigital skin characterised by erosion and hyperkeratosis were usually associated with the occurrence of B nodosus. B nodosus isolated from cattle induced mild interdigital dermatitis in experimental cattle and sheep and the infection was transmitted to recipient cattle and sheep under field conditions. Virulent foot-rot of sheep was not transmitted to recipient cattle in conditions where the disease spread to susceptible sheep.  相似文献   
6.
The expression of growth factors was evaluated immunohistochemically in normal and cystic ovaries of sows. The immunohistochemically stained area (IHCSA) was quantified by image analysis to analyse the expression of these proteins in the follicular wall of secondary, tertiary and cystic follicles. IGF‐I immunoreactivity was strong in the granulosa cell layer (GC), moderate in the theca interna (TI) and mild in the theca externa (TE) of the normal follicles. There was severe reduction of the labelling to IGF‐I in the GC of the follicular and luteinized cysts. In the normal follicles, the reactivity for IGF‐II was very similar to pattern noted in IGF‐I. There was reduction of the IHCSAs in the GC of the follicular and luteinized cysts, but the decrease was not significant. The staining of the IGF‐II in the TI and TE of the cysts was increased, in comparison with normal follicles. The IHCSAs for VEGF were higher in the GC and TE of the normal follicles in contrast to TI, but this difference was noted only in the tertiary follicle. The VEGF reactivity increased in the GC of the cysts, in relation to normal follicles. The results of the current study show that the formation of ovarian cysts in sows is associated with alterations in the immunohistochemical expression of some growth factors.  相似文献   
7.
A simple and inexpensive device is described which maintains cultures of marine microalgae at predetermined cell densities by the automatic control of harvesting and replenishment of the culture volume with fresh medium. Cultures were maintained at a range of cell densities in 80-litre internally illuminated vessels and the daily cell production yield was evaluated.Maximum yields of 0·8–1·0×1012 cells day?1 of Isochrysis aff. galbana Green and 0·8–1·2×1011 cells day?1 of Tetraselmis suecica (Kylin) Butch. were obtained at culture densities of 15–17×103 cells μlitre?1 and 19–21×102 cells μlitre?1, respectively. Turbidostat cultures of Skeletonema costatum (Grev.) Cleve could not consistently be maintained above 5–7×103 cells μlitre?1.  相似文献   
8.
9.
In September 2003 Hurricane Isabel swept through eastern North Carolina and Virginia, destroying most of what formerly ranked among the most extensive remaining stands of Atlantic White-cedar (Chamaecyparis thyoides L., cedar). As Atlantic White-cedar communities are dependent on irregular, large-scale disturbances, the hurricane event can be viewed as an opportunity for perpetuating cedar populations in the Great Dismal Swamp. The success of cedar regeneration in the Dismal Swamp has been influenced by the management strategies employed by Great Dismal Swamp National Wildlife Refuge (active management) and by the adjacent Dismal Swamp State Park (passive management). We investigated the regeneration success of Atlantic White-cedar 5 years following Hurricane Isabel by sampling five stands at the Dismal Swamp State Park withstanding varying impact from the storm and previous windthrow events. We compared our findings to regeneration surveys completed at the adjacent Great Dismal Swamp National Wildlife Refuge. Atlantic White-cedar seedling densities were up to 100 times higher in the actively managed Wildlife Refuge compared to the passively managed State Park. We also determined the seedbank of viable cedar seeds and we described the vegetation at the State Park. The stands at the State Park are now dominated by red maple (Acer rubrum) with a dense shrubby understory. Since viable cedar seeds were still present in the seedbank (>800,000 ha−1), future seedling establishment is possible at the State Park. However, active management is essential for achieving sufficient seedling densities and survival for regenerating a mature cedar stand.  相似文献   
10.
Sterile hemorrhagic cystitis developed in 5 dogs after treatment with cyclophosphamide. Four dogs were being treated with various antineoplastic protocols, and the fifth dog had recurrent immune-mediated thrombocytopenia. In all instances, clinical signs of hematuria and stranguria persisted after cyclophosphamide administration was discontinued. Three dogs required cystotomy to remove necrotic mucosa and calculi. The other 2 dogs were treated with intravesicularly administered dimethyl sulfoxide to decrease inflammation and to inhibit fibroplasia of the bladder wall. In 4 dogs, clinical signs resolved after treatment. The fifth dog, treated surgically, continued to have intermittent urinary incontinence attributable to residual bladder wall fibrosis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号