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   591篇
  免费   29篇
  国内免费   1篇
林业   68篇
农学   13篇
  112篇
综合类   31篇
农作物   17篇
水产渔业   130篇
畜牧兽医   222篇
园艺   8篇
植物保护   20篇
  2022年   5篇
  2021年   9篇
  2020年   8篇
  2019年   8篇
  2018年   11篇
  2017年   14篇
  2016年   13篇
  2015年   21篇
  2014年   14篇
  2013年   65篇
  2012年   28篇
  2011年   47篇
  2010年   14篇
  2009年   16篇
  2008年   24篇
  2007年   45篇
  2006年   38篇
  2005年   55篇
  2004年   27篇
  2003年   34篇
  2002年   27篇
  2001年   29篇
  2000年   18篇
  1999年   5篇
  1998年   5篇
  1997年   4篇
  1996年   5篇
  1995年   1篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1988年   3篇
  1987年   2篇
  1986年   1篇
  1984年   2篇
  1981年   3篇
  1979年   1篇
  1978年   4篇
  1977年   2篇
  1976年   1篇
  1975年   3篇
  1972年   1篇
  1970年   1篇
排序方式: 共有621条查询结果,搜索用时 15 毫秒
571.
Abnormal early ripening (AER), a major constraint on wheat production in Western Japan, manifests as sudden leaf senescence shortly after anthesis and results in poor grain filling; this leads to smaller grains and reduced grain yield. It is suggested that overwetting of the soil may be related to AER. We conducted field experiments over 2 seasons (2008-2009 and 2009-2010) in Yamaguchi, Western Japan, with waterlogging treatment using 2 Japanese wheat cultivars, Daichinominori (Western Japanese cultivar) and Haruyutaka (Hokkaido cultivar), which differ in terms of grain growth in the environment of Western Japan. We imposed pre-anthesis waterlogging for 2 weeks in 2008-2009 and post-anthesis waterlogging throughout the grain-filling period in 2009-2010. Pre-anthesis waterlogging had no significant effect on grain yield or grain filling irrespective of cultivar. Post-anthesis waterlogging severely reduced the grain yield by 44% and 36% in Haruyutaka and Daichinominori, respectively. The yield loss was attributable to the smaller grain weight that was a result of slower grain growth rate later in the shortened grain-filling period. Post-anthesis waterlogging induced sudden leaf senescence 1 and 2 weeks after anthesis in Haruyutaka and Daichinominori, respectively, and drastically reduced the photosynthesis and ultimately dry mass accumulation. It also depressed the remobilization of water-soluble carbohydrates (WSCs) from culms to grains leaving more residual WSCs in the culms at harvest (149 and 65 mg g−1 DW in waterlogging and controls, respectively). The results indicate that the reduced grain growth due to waterlogging was attributable to decreased current assimilation and poor remobilization of culm WSCs to grain similar to that in AER plants. These results suggest that injured root function after anthesis might induce early leaf senescence and poor grain filling similar to AER wheat.  相似文献   
572.
We evaluated the effect of stress and adrenaline injection on insulin release in barfin flounder Verasper moseri. Flounders were fed to satiation and then exposed to 30 min of stress (chasing using a blunt stick), beginning 15 min after feeding. Plasma insulin concentrations were measured using a time-resolved fluoroimmunoassay for barfin flounder insulin. Peak insulin concentrations in the stressed flounders (3.4 ± 1.0 ng/ml, mean ± SEM) were lower than in the control group (8.3 ± 1.7 ng/ml). Similarly, in flounders injected with l-arginine (Arg; 3.5 mmol/kg body weight), the most potent insulinotropic factor for flounders, insulin levels were lower for up to 5 h in individuals exposed to chasing stress. Furthermore, plasma insulin levels did not increase after injection with Arg followed by exposure to 10 min of stress. This was also true for flounders co-injected with Arg (20 nmol/kg body weight) and adrenalin instead of the chasing stress. We conclude that stress induces a powerful and extended inhibition of insulin release in flounders, even when the stress is acute. We hypothesize that this effect is mediated partly by adrenaline release. Our results provide insight into the deleterious effects of stress on growth.  相似文献   
573.
取30例强直性脊柱炎(AS)患者和30例健康对照组外周血清和膝关节滑液,采用放射性免疫法和双抗体夹心酶免疫吸附法分析瘦素(leptin)、IL-17、TNF-α、IL-6含量,探讨leptin、Th17细胞因子与AS病情活动的相关性。结果表明:AS患者外周血和膝关节滑液中leptin、IL-17、TNF-α、IL-6含量比健康对照组明显升高(P0.01)。AS外周血和关节滑液中leptin的表达水平与IL-17、IL-6呈显著相关(P0.01),与TNF-α表达相关不显著。AS患者外周血清和关节滑液中leptin、IL-17、IL-6平均表达水平与AS患者的血沉、C-反应蛋白、Bath强直性脊柱炎活动指数呈显著相关(P0.05),TNF-α的表达水平与AS病情活动指标相关不显著。说明leptin及Th17相关细胞因子在AS患者外周血和关节滑液中明显升高,可能直接参与了AS关节炎症过程。  相似文献   
574.
Several lines of evidence have shown that the olfactory system of the fish contains the main and accessory olfactory systems. However, morphological data indicate that the accessory olfactory bulb, the primary centre for the accessory olfactory system, will not differentiate in the fish. Therefore, the fish olfactory bulb is supposed to engage in both main and accessory olfactory systems. To examine this possibility, we investigated the olfactory bulb of the barfin flounder ( Verasper moseri ) by histochemical examination using lectins. The olfactory bulb of the barfin flounder showed a laminar structure with four layers, and diffuse glomerular architecture was observed in the glomerular layer. Based on the expression patterns of sugar residues, the glomerular layer of the barfin olfactory bulb was largely divided into three portions. Heterogeneity in the lectin-binding pattern among olfactory glomeruli was clearly demonstrated by the fluorescent double-lectin staining. The results of this study suggest that the fish olfactory bulb contains both regions equivalent to the main and accessory olfactory bulbs, and they are subdivided into small subsets with different functions.  相似文献   
575.
夏季飞来昆虫对放牧牛摆尾行为的影响   总被引:1,自引:1,他引:0  
本研究选择黑毛和牛种牛4头作为实验牛。从2000年8月至10月,在0.8ha的实验牧草地进行了实验。实验结果表明:飞来昆虫消化的季节,飞来昆虫对放牧牛摆尾行为的影响可能存在个体飞来昆虫不仅引起牛的体表护理行为,还可能导致心理上的应激。  相似文献   
576.
Ten germ-free pigs and 10 conventionally reared pigs were fed one of two nutritionally balanced diets containing either 16 ppm Cu (basal) or 283 ppm Cu (high-Cu) to evaluate the physiological relationships between Cu and microbiological environment. Germ-free pigs tended to have higher ADG and average daily feed intake (ADFI) than conventionally reared pigs. Feeding the high-Cu diet tended to reduce ADG and ADFI in germ-free pigs but it increased ADG and ADFI in conventionally reared pigs. Hemoglobin and hematocrit were higher in germ-free pigs than in conventionally reared pigs (P less than .001), and hematocrit (P less than .01) and erythrocyte count (P less than .06) were reduced by feeding the high-Cu diet. Germ-free pigs had lower total leukocyte count (P less than .01) and the relative percentages of differentiated leukocytes were altered compared with conventionally reared pigs. Feeding the high-Cu diet increased the percentage of band neutrophils and monocytes in germ-free pigs but reduced the percentage of these cells in conventionally reared pigs (P less than .04). Germ-free pigs had higher concentrations of Cu and Zn in liver and plasma (P less than .001) and greater plasma ceruloplasmin oxidase activity (P less than .001) than conventionally reared pigs did. The high-Cu diet increased liver Cu and Zn (P less than .001) and plasma Cu (P less than .001) and reduced liver and plasma Fe (P less than .05). Organ weights (g/kg BW) differed between germ-free and conventionally reared pigs, and feeding the high-Cu diet reduced thymus weights (P less than .002). Intestinal weight and thickness were reduced in germ-free pigs, and feeding the high-Cu diet generally reduced villus height and width and crypt depth in germ-free pigs, whereas it increased these measurements in conventionally reared pigs.  相似文献   
577.
There are several benefits to a high-fat diet for animals exposed to cold, including improved tolerance to severe cold conditions and increased survival rates in cold environments. It is therefore of interest to examine whether animals exposed to cold will selectively consume lipids. We examined the intake of safflower oil (SO) by rats exposed to cold (4 +/- 2 degrees C) under a feeding condition in which the rats were given free access to SO. Rats exposed to cold consumed more SO than those housed at 25 +/- 2 degrees C. This finding suggests that rats prefer SO in a cold environment. There was no significant difference in the ratio of calories of SO ingested to that of matter (standard laboratory chow plus SO) ingested between rats exposed to cold and those at 25 +/- 2 degrees C. The high SO intake also affected cold tolerance and metabolite kinetics in the rats. Factors that affected the SO intake of rats exposed to cold are also discussed.  相似文献   
578.
The effects of delipidation and the oxygen (O(2)) concentration in the atmosphere during culture on in vitro development and H(2)O(2) content were investigated in porcine in vivo fertilized embryos and embryos after in vitro maturation and in vitro fertilization (IVM/IVF embryos). There was no significant difference in the developmental rates to the blastocyst stage between the intact and delipidated IVM/IVF embryos. However, the mean number of cells in blastocysts derived from delipidated IVM/IVF embryos (19.8 +/- 0.8 cells) was significantly smaller than that from intact embryos (24.2 +/- 1.2 cells). Although there were no significant differences in the developmental rates to the blastocyst stage of intact and delipidated IVM/IVF embryos between the cultures under 5% O(2) and 20% O(2), the developmental rate of intact IVM/IVF embryos cultured under 5% O(2) (27.1%) was significantly higher than that of the delipidated embryos cultured under 20% O(2) (19.3%). On the other hand, there was no difference in the developmental rate to the blastocyst stage between in vivo fertilized embryos cultured under 5% O(2) and 20% O(2). Hydrogen peroxide (H(2)O(2)), one of the reactive oxygen species (ROS), is thought to cause damage to embryos. The H(2)O(2) content per embryo derived from oocytes cultured under 5% O(2) (in vivo fertilized, 58.0 +/- 2.5 pixels; IVM/IVF, 79.6 +/- 3.2 pixels) was significantly lower than that (in vivo fertilized, 100.2 +/- 3.8 pixels; IVM/IVF, 103.9 +/- 3.2 pixels) under 20% O(2). Furthermore, the level of H(2)O(2) in delipidated IVM/IVF embryos (94.7 +/- 3.9 pixels) was significantly lower than that in intact embryos (103.9 +/- 3.2 pixels) cultured under 20% O(2). The present results indicate that the delipidation of porcine IVM/IVF embryos and reduction of the O(2) concentration decreased the H(2)O(2) level rather than the in vitro developmental rate to the blastocyst stage.  相似文献   
579.
The effects of acepromazine-butorphanol (AB), midazolam-butorphanol (MB) and medetomidine (Med) on the induction dose of propofol and their compatibility with propofol were evaluated in client-owned dogs. All premedications induced good to excellent sedation and the induction dose of propofol was considerably reduced. Of the tested premedicants, Med induced the deepest sedation and the most potent dose-sparing effect. Induction of anesthesia was excellent to good in all dogs except for one dog premedicated with MB. Most dogs premedicated with AB or MB showed temporary apnea. Although other adverse effects such as bradycardia or hypotension may also occur, premedication with MB, AB or Med is a valuable technique for the induction of anesthesia with propofol in dogs in a clinical setting.  相似文献   
580.
The effect of fusion/activation protocol on in vitro development of porcine nuclear transfer (NT) embryos constructed with foreign gene-transfected somatic cells were investigated. NT embryos were produced by using enucleated M II oocytes and enhanced green fluorescence protein (EGFP) gene-transfected or non-transfected porcine fetal fibroblasts. One group of NT embryos received a single electrical pulse to induce fusion and activation simultaneously (FAS). The other group was fused 2 hr before activation (FBA) using two kinds of electrical pulses. Electrically activated NT embryos in both groups were treated with cycloheximide (CHX) before culture to assess the development to the blastocyst stage. After 6 days of culture, all morulae and blastocysts derived from EGFP-transfected fibroblasts emitted green fluorescence without mosaicism, and EGFP-gene product was also detected in all morulae and blastocysts examined. NT embryos undergoing FAS showed higher developmental capacity to blastocysts than those undergoing FBA, regardless of the EGFP transfection into the nuclear donor cells. The results also indicated that EGFP-gene transfection into nuclear donor cells has no obvious deleterious effect on the development of NT embryos to blastocysts.  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