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   221篇
  免费   11篇
林业   21篇
农学   11篇
  11篇
综合类   8篇
农作物   4篇
水产渔业   19篇
畜牧兽医   146篇
园艺   7篇
植物保护   5篇
  2024年   1篇
  2022年   7篇
  2021年   1篇
  2020年   2篇
  2019年   4篇
  2018年   2篇
  2017年   6篇
  2016年   8篇
  2015年   2篇
  2014年   8篇
  2013年   8篇
  2012年   5篇
  2011年   11篇
  2010年   4篇
  2009年   7篇
  2008年   9篇
  2007年   18篇
  2006年   4篇
  2005年   16篇
  2004年   14篇
  2003年   14篇
  2002年   10篇
  2001年   11篇
  2000年   10篇
  1999年   7篇
  1998年   4篇
  1997年   2篇
  1996年   2篇
  1992年   8篇
  1991年   4篇
  1990年   6篇
  1989年   5篇
  1988年   1篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1969年   1篇
  1968年   1篇
  1964年   1篇
排序方式: 共有232条查询结果,搜索用时 156 毫秒
1.
MX belongs to a family of type I interferon (IFN)-stimulated genes, and the MX protein has antiviral activity. MX has at least two isoforms, known as MX1 and MX2, in mammals. Moreover, bovine MX1 has been found to have alternative splice variants—namely, MX1-a and MX1B. In ruminants, IFN-τ—a type I IFN—is temporarily produced from the conceptus before implantation and induces MX expression in the endometrium. However, the expression dynamics of MX after implantation are not clear. In the present study, we investigated the expression of MX1-a, MX1B and MX2 in the endometrium and placenta before and after implantation along with the expression of IFN-α, type I receptors (IFNAR1 and IFNAR2) and interferon regulatory factors (IRF3 and IRF9). Pregnant uterine samples were divided into five groups according to pregnancy days 14–18, 25–40, 50–70, 80–100, and 130–150. Tissue samples were collected from the intercaruncular endometrium (IC), caruncular endometrium (C) and fetal placenta (P). Although all the MX expressions were significantly higher in the IC and C at days 14–18, presumably caused by embryo-secreted IFN-τ stimulation, their expressions were also detectable in the IC, C and P after implantation. Furthermore, IFN-α expression was significantly higher in the IC. RT-PCR indicated IFNAR1, IFNAR2, IRF3 and IRF9 mRNA in all the tissues during pregnancy. These results suggest that all the MX genes are affected by the type I IFN pathway during pregnancy and are involved in an immune response to protect the mother and fetus.  相似文献   
2.
Dolphins in a captive environment are exposed to various kinds of stresses. Handling and transportation are stressful events for terrestrial mammals, and such stress may affect immune system function and increase susceptibility to infectious diseases. The same phenomenon could occur in dolphins, however, few studies have reported this in dolphins. The objective of this study was to evaluate the relationship between stress and polymorphonuclear (PMN) cell function of dolphins during transportation. Four bottlenose dolphins (Tursiops truncatus) were transported for 6 hr by truck. Serum cortisol levels, leukograms, phagocytosis, and superoxide production of PMN cells were evaluated during handling and transportation compared to resting values. The mean serum cortisol level was significantly increased during handling and transportation (p<0.05) when compared with the resting values. White blood cell (WBC) counts, eosinophil counts, phagocytosis, and superoxide production of PMN cells during handling and transportation stages decreased significantly in comparison with the resting stage (p<0.05). The concentration of serum cortisol was significantly correlated with the results of the WBC counts, eosinophil counts, superoxide production, and phagocytosis (p<0.01, p<0.05, p<0.05, and p<0.001, respectively). The present results indicate that handling and transportation are stressful events for dolphins and could affect their PMN cell functions, thereby leading to the impairment of the immune system.  相似文献   
3.
Juvenile green abalone Haliotis rufescens were grown under laboratory conditions at 21±1 °C and fed formulated diets consisting of different protein:energy ratios (mg protein/kcal), 62, 74, 85, 100, 108, for 60 days. The level of crude protein ranged from approximately 26% to 44% while the energy content remained constant at about 4.1 kcal g−1. Growth ranged from 3.63 to 12.33 mg day−1. The growth of abalone fed the 100 and 108 diets was significantly greater than that of each of the other diets. Protein efficiency ratio increased as the dietary protein content increased except for the T108 diet (44% crude protein). Abalone apparently consume food to satisfy an energy requirement. Caloric expenditure due to metabolism was estimated for abalone fed diets with protein ratios of 62, 85, 100. Energy loss due to respiration did not vary appreciably among abalone fed the different diets. The proportional distribution of dietary energy into fecal, digestible, growth, and metabolic energy was estimated for abalone fed these diets. Apparent dry matter digestibility was among the lowest for abalone fed the 100 P:E diet, but growth of abalone fed this diet was significantly higher than that of each of the other treatments except the 108 diet. Unexplained energy loss to achieve balance ranged from 7% to 28.5%, some of which is probably due to differential mucus and ammonia production. Results suggest a potential for the reduction of both dietary protein and lipid without causing any adverse effects on the growth response.  相似文献   
4.
We estimated the aboveground net primary production (ANPP) in five self-thinning jack pine (Pinus banksiana) stands in Wood Buffalo National Park, NWT, Canada. The stands (11 to ca.175 years old) were selected to examine the relationship between stand density and tree size and its effect on carbon dynamics. Aboveground litterfall was collected from each stand from 1997 to 2012. Stand biomass was estimated by measuring tree size every 5 years and estimating the individual mass using allometric relationships. ANPP was then estimated by summing the litterfall mass, dead stem mass increment and stand biomass increment. We determined the proportional contribution of each organ to the total litter and the seasonal pattern of needle litterfall. There was a lower turnover rate of aboveground biomass in older stands than younger stands. The ANPP increased in the youngest stand (<30 years old) showed a decreasing trend in stands >50 years old. The maximum ANPP was estimated to be ca. 500?g m?2 year?1 in dry matter, which was found in 30–50 year-old stands.  相似文献   
5.
The endometrial epidermal growth factor (EGF) profile is an indicator of uterine function and fertility in cattle. The present study aimed to investigate the effects of heat stress on the endometrial EGF profile and fertility in lactating Holstein cows. The endometrial EGF profiles of 365 cows in the Hokkaido and Kyushu regions were examined between June and September (heat stress period, n = 211) and between October and January (control period, n = 154). EGF profiles were investigated using uterine endometrial tissues obtained by biopsy 3 days after estrus (Day 3). The proportion of cows with an altered EGF profile was higher between June and September than between October and January (41.2 vs. 16.2%, P < 0.05). The effects of rectal temperature on Days 0 and 3 on the endometrial EGF profile were also assessed in cows (n = 79) between June and September in the Kyushu region. A single embryo was transferred to cow on Day 7 to evaluate fertility (n = 67). Regardless of the rectal temperature on Day 3, the proportion of cows with an altered EGF profile was higher (64.1 vs. 30.0%, P < 0.05) and the pregnancy rate after embryo transfer (ET) was lower (26.7 vs. 51.4%, P < 0.05) in cows with a rectal temperature ≥ 39.5°C on Day 0 than in cows with a rectal temperature < 39.5°C on Day 0. The present results indicate that alterations in the endometrial EGF profile induced by an elevated body temperature on Day 0 contributed to reductions in fertility in lactating dairy cows during the heat stress period.  相似文献   
6.
7.
A 10-year-old, female shih tzu was diagnosed as having myelodysplastic syndrome (MDS) based on the presence of a nonregenerative anemia, dysplastic changes in the three hematopoietic cell lines, a normal to hypercellular bone marrow, and less than 30% blast cells of all nucleated cells in the bone marrow. Low-dose aclarubicin, a differentiation-induction therapy for MDS and atypical leukemias in humans, was administered. Hematological improvement was observed, and the dog lived for 809 days after the first presentation.  相似文献   
8.
We performed a pathologic examination of the brains of three dogs in an epileptic beagle colony. Histologically, all the cases had diffuse astrocytosis in the cerebral cortex and basal ganglia as well as the hippocampus, whereas they showed acute nerve cell change in the hippocampus and some other areas of the cerebrum. One of these animals showed laminar myelin pallor associated with the presence of many vacuoles in the IV to VI layers of the bilateral motor cortices. Most of the vacuoles contained fine granules stained with luxol-fast-blue stain. Ultrastructural examination revealed that some oligodendrocytes and perineuronal satellite oligodendrocytes in the bilateral cerebral motor cortices of the two affected dogs had many vacuoles surrounded by myelin-like lamellar structures. These findings suggest a possibility that astrocytosis in the cerebrum and vacuolar degeneration of oligodendrocytes in the cerebral motor cortex may be, at least in part, related to the occurrence or development of seizures.  相似文献   
9.
In vitro cell culture is a convenient tool for studying cellular mechanisms. In the present study, production of matrix-metalloproteinases (MMPs) in bovine endometrial (containing both epithelial and stromal cells) monolayer cells was examined. Blastocysts attached to the endometrial cells in a monolayer culture were examined for their effects on MMP-2 production. Initial attachment of blastocysts to the monolayer inhibited MMP-2 production by endometrial cells. But once trophoblast cells began to migrate into the endometrial cell layer, MMP-2 production increased, and at the same time MMP-9 production also became evident in the medium. In order to understand how blastocysts affected MMP-2 production, we examined the effect of progesterone, estradiol, insulin-like growth factors (IGFs), tumor necrosis factors (TNFs), and interferon-tau (IFN-tau) supplementation. It was IFN-tau that inhibited the production of MMP-2. In addition, progesterone at a lower dose appeared to inhibit MMP-2 production. Both TNF-alpha and TNF-beta strongly stimulated the production of MMP-2 and MMP-9, whereas IGFs had no effect. Based on these findings, it appears that conceptus has the capacity to inhibit MMP activity.  相似文献   
10.
Neospora caninum was isolated from the brain of a 2-year-old dairy cow that had aborted confirmed N. caninum-infected fetuses on two occasions. The cow had an indirect fluorescent antibody titer of 1:1600 to N. caninum. The cow was killed 24 days after its second abortion and the brain was bioassayed for N. caninum in nude mice. Multifocal areas of perivascular cuffing and glial nodules were observed in the cerebrum and mesencephalon of the cow, but N. caninum was not identified in histological sections of the brain. All three nude mice inoculated with brain homogenate of the cow, developed emaciation and paralysis. Microscopical examination of the nude mice revealed systemic N. caninum infection with demonstrable tachyzoites in various organs. The parasites isolated from fresh mouse brain were transferred successfully into Vero cell cultures. PCR procedure on the purified tachyzoites obtained from the Vero cell cultures amplified the specific DNA sequence for N. caninum.  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