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   788篇
  免费   97篇
  国内免费   57篇
林业   15篇
农学   26篇
基础科学   6篇
  19篇
综合类   193篇
农作物   20篇
水产渔业   120篇
畜牧兽医   459篇
园艺   61篇
植物保护   23篇
  2024年   3篇
  2023年   17篇
  2022年   25篇
  2021年   46篇
  2020年   50篇
  2019年   52篇
  2018年   31篇
  2017年   56篇
  2016年   60篇
  2015年   47篇
  2014年   52篇
  2013年   47篇
  2012年   49篇
  2011年   53篇
  2010年   28篇
  2009年   34篇
  2008年   31篇
  2007年   24篇
  2006年   16篇
  2005年   19篇
  2004年   17篇
  2003年   19篇
  2002年   26篇
  2001年   14篇
  2000年   14篇
  1999年   10篇
  1998年   10篇
  1997年   15篇
  1996年   6篇
  1995年   13篇
  1994年   10篇
  1993年   8篇
  1992年   7篇
  1991年   5篇
  1990年   3篇
  1989年   7篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   3篇
  1984年   3篇
  1981年   1篇
  1980年   3篇
  1975年   3篇
  1973年   1篇
排序方式: 共有942条查询结果,搜索用时 250 毫秒
91.
水牛肾属于表面有沟的多乳头肾,无肾盂,肾小盏汇合成肾大盏,肾大盏与输尿管相连.肾小体直径平均为210μm,横径平均为146μm,与马的接近,比牛和猪的要大.近曲小管细胞立方形或低柱状.游离端刷状缘短而稀少.胞质染色浅,管腔大,难与远曲小管区分.细段不如其它动物长.细胞器也少.远曲小管短,细胞为立方形,界线清楚,核多而密集.集合小管细胞染色浅,胞质清亮,细胞分界明显.肾间质十分发达.血管丰富.并分布有肥大细胞.  相似文献   
92.
AIM: To investigate the role of excitatory amino acid transporter 3(EAAT3) in prefrontal cortex and hippocampus in morphine relapse by detecting the changes of EAAT3 expression in prefrontal cortex and hippocampus in conditioned place preference (CPP) reinstatement rat model induced by morphine.METHODS: Forty adult male SD rats, weighing 200-250 g, were randomly divided into 5 groups with 8 rats each: control group, CPP establishment group (Es), CPP extinction group (Ex), reinstatement 2 h group (Re2) and reinstatement 4 h group (Re4).Intraperitoneal (ip) injection of morphine was applied at a constant dose (10 mg/kg) for 10 days to the established CPP model.Normal saline instead of morphine was used to induce CPP extinction for 10 days.CPP was reinstated following a single priming injection of morphine (2.5 mg/kg).After the CPP behavior test, the rats were sacrificed, and the prefrontal cortex and hippocampus were collected for detecting the levels of EAAT3 by Western blotting.RESULTS: The accumulated time the rats spent in the drug-paired chamber was significantly longer in Es group, Re2 group and Re4 group than that in control group (P<0.05).Compared with control group, the expression of EAAT3 in prefrontal cortex significantly decreased both in Es group and Re4 group (P<0.05).No significant change of EAAT3 in hippocampus among groups was observed (P>0.05), while EAAT3 in hippocampal CA1 area significantly increased in Es group and Ex group as compared with control group (P<0.05).CONCLUSION: The expression of EAAT3 in prefrontal cortex decreases both in CPP establishment and reinstatement models, indicating that down-regulation of EAAT3 in prefrontal cortex may partly participate in the formation of opium relapse.  相似文献   
93.
94.
采集岷县黑裘皮羊肾组织,用胰蛋白酶热消化法制备原代细胞,通过差速消化和差速贴壁法进行继代培养和细胞纯化,并对复苏细胞的形态、活力、生长曲线、荧光蛋白质粒转染表达、核型以及乳酸脱氢酶同工酶等生物学特性进行了分析。结果显示:原代和传代细胞生长形态均好,群体倍增时间为28.3 h;染色体2 n=54,二倍体占主体(84%)乳酸脱氢酶同工酶电泳图谱有明显特征,未见LDH4、LDH5谱带,与其它羊有明显区别;外源性荧光蛋白转染质粒在该细胞中能进行复制和表达;细菌、真菌、病毒、支原体检测呈阴性。表明该研究已成功建立岷县黑裘皮羊肾组织成纤维细胞系,为在细胞水平上保存岷县黑裘皮羊种质资源以及进行相关研究提供了理想的生物材料。  相似文献   
95.
探讨了3种常用的有机磷农药胚胎期暴露对新生鼠脑组织结构的影响。在母鼠妊娠期7.5~11.5 d时,连续5 d每天分别经皮下注射2 mg/kg bw的二嗪磷(diazinon)、2 mg/kg bw的毒死蜱(chlorpyrifos)及50 mg/kg bw乙酰甲胺磷(acephate),显微镜下观察并计数大脑皮层S1区胶质细胞和神经元数量及比率,以及海马CA1、CA3区锥体细胞的数量及体积密度。结果表明,二嗪磷与毒死蜱处理分别使得大脑皮层S1区胶质细胞数减少了14.29%和21.43%;毒死蜱处理导致胶质细胞与神经元比率下降了24.19%;二嗪磷与毒死蜱处理后海马CA1区锥体细胞数量分别下降了9.30%与20.93%,毒死蜱处理后锥体细胞体积密度下降了27.05%;二嗪磷与毒死蜱处理后海马CA3区锥体细胞数量分别下降了22.22%和19.44%,锥体细胞体积密度分别下降了23.54%和18.98%;而乙酰甲胺磷对新生鼠大脑皮层与海马细胞均无明显影响。  相似文献   
96.
540只1日龄红布罗商品代雏鸡随机分为9组,第1组饲喂以小麦为基础的诱发日粮,第2和第3组在1组基础上分别添加300(μg/kg日粮)生物素和动物脂肪(前期2%,后期3%)。第4至9组饲以玉米-豆饼型日粮,前后期分别添加0,50,90,120,150,200和0,50,70,95,120,160(μg/kg日粮)的生物素。结果表明:生物素缺乏造成足底皮肤炎,肝脏脂肪酸成分发生变化:不饱和脂肪酸(棕榈油酸)显著增加(P<0.01),饱和脂肪酸(硬脂酸)减少(P<0.05)。29日龄绝食24h,饲喂诱发日粮的鸡,血糖、肝糖原和肝脏总脂肪含量下降,血浆甘油三酯增加,但无显著差异(P>0.05)。玉米-豆饼型日粮中添加不同水平生物素,绝食后血糖、肝糖原和甘油三酯含量未发生显著变化,随生物素添加水平提高,对足部皮肤状况有一定的改善作用,前期添加150或200(μg/kg日粮)生物素对增重和饲料报酬较好,而后期添加生物素影响不大。种鸡试验选用336只20周龄育成种鸡随机分为3组,分别饲以添加有0,100,150μg/kg生物素的日粮。初步结果表明:生物素对蛋重无影响,日粮添加100和150μg/kg生物素可提高受精率0  相似文献   
97.
A manual, ultrasound-guided biopsy technique was compared to a new automatic method using a new biopsy device. The liver and the left kidney of 10 dogs were biopsied using the two methods. The specimens from the biopsies were compared for size and quality. Results demonstrate that larger and higher quality samples were obtained with the new automatic method.  相似文献   
98.
QFM合剂麻醉剂量对犬肝、肾功能的影响   总被引:2,自引:0,他引:2  
QFM合剂是一种新型的犬用复合麻醉制剂。本试验旨在研究其对犬肝、肾功能的影响。试验用7条犬肌肉注射QFM合剂0.15~0.2mL(每千克体质量),观察比较了注药前、后犬血清GOT、GPT、AKP活性和尿素氮、肌酐含量的变化。结果证明:注药前、后犬血清GOT、GPT、AKP活性和尿素氮、肌酐含量的变化差异不显著,在正常生理范围内。说明QFM合剂应用于犬的麻醉,时犬的肝、肾功能无明显不良影响,进一步证明了QFM合剂应用于犬的临床安全性。  相似文献   
99.
African swine fever is a viral haemorrhagic disease of pigs which has been used as a model for the study of viral haemorrhagic diseases in man. The acute course of the disease is characterized by acute proliferative glomerulonephritis, with viral replication in mesangial cells and occasional focal necrosis of the renal tubular system; hyperplasia of the collecting ducts is associated with evident virus replication. Haemorrhages have been attributed to endothelial dysfunction, aggravated by virus replication in endothelial cells in the final stages of the disease. The renal interstitium displays intense oedema and an infiltrate largely composed of macrophages. Virus replication has also been observed in fibroblasts and in the smooth0muscle cells of arterioles and venules.In subacute-chronic forms of the disease, various types of glomerulonephritis are observed, ranging from mesangial proliferative glomerulonephritis to focal and segmental hyalinosis associated with immune-mediated phenomena. No striking changes are reported in the renal tubular system. Interstitial haemorrhages are associated with diapedesis due to immunologically mediated events. The interstitium has also been found to contain a lymphohistiocytic infiltrate with abundant plasma cells. No evidence has been reported of viral replication in any cell population.Abbreviations ASF African swine fever - ASFV African swine fever virus - C complement component - DNA deoxyribonucleic acid - HAD50 50% haemoadsorbing doses - Ig immunoglobulin - MPS mononuclear phagocytic system - PAS periodic acid-Schiff reagent  相似文献   
100.
Canine kidney measurements were obtained in vivo using ultrasound before and after anesthesia and were compared with direct caliper measurements at laparotomy. Following excision, the kidney dimensions were also measured ultrasonically in a water bath and the results were used to calculate kidney -volume by a modified parallel planimetric method and three variations of a prolate ellipsoid method. The calculated volume was compared with actual kidney volume determined by volume displacement. All methods were found to underestimate actual volume so that a linear correction of ultrasonically calculated volume was required to predict actual volume. The modified parallel planimetric method and a prolate ellipsoid method using height and width determinations cranial and caudal to the renal pelvis were the best models. The prolate ellipsoid model was chosen for subsequent kidney volume calculations because of its simplicity. The noninvasive calculation of kidney volume using ultrasound was sufficiently accurate to be clinically useful, particularly when serially evaluating kidney size changes in the same dog.  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