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   48927篇
  免费   2739篇
  国内免费   5007篇
林业   3676篇
农学   3749篇
基础科学   2834篇
  5768篇
综合类   21747篇
农作物   3420篇
水产渔业   2142篇
畜牧兽医   7645篇
园艺   3221篇
植物保护   2471篇
  2024年   331篇
  2023年   825篇
  2022年   2035篇
  2021年   2096篇
  2020年   2024篇
  2019年   1923篇
  2018年   1392篇
  2017年   2159篇
  2016年   1571篇
  2015年   2415篇
  2014年   2434篇
  2013年   3002篇
  2012年   3999篇
  2011年   4209篇
  2010年   3882篇
  2009年   3390篇
  2008年   3561篇
  2007年   3267篇
  2006年   2750篇
  2005年   2150篇
  2004年   1388篇
  2003年   938篇
  2002年   954篇
  2001年   926篇
  2000年   848篇
  1999年   460篇
  1998年   260篇
  1997年   224篇
  1996年   217篇
  1995年   225篇
  1994年   161篇
  1993年   149篇
  1992年   125篇
  1991年   91篇
  1990年   64篇
  1989年   60篇
  1988年   33篇
  1987年   33篇
  1986年   22篇
  1985年   10篇
  1984年   6篇
  1983年   8篇
  1982年   7篇
  1981年   7篇
  1966年   2篇
  1963年   1篇
  1962年   9篇
  1958年   1篇
  1956年   21篇
  1955年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
十种常用农药与球孢白僵菌的生物学相容性   总被引:24,自引:2,他引:24  
球孢白僵菌孢子粉与10种常用农药相容性的测定结果显示,随着孢子浓度上升,所试农药对孢子的抑制作用均有不同程度的增强。在1/10田间常规使用浓度下,百菌清和代森锰锌均能抑制或杀死孢子(萌发率<1%)。除阿维菌素外,所有杀虫剂均与白僵菌孢子相容,在常规使用浓度的10倍稀释液中孢子萌发率达90%以上。吡虫啉、蚜虱灵、灭多威和氟虫腈与孢子的相容性最好,其中吡虫啉和蚜虱灵对孢子萌发率的影响不明显随药剂浓度的变化而变化,即使在田间常规使用浓度下孢子萌发率也在95%以上,而阿维菌素与白僵菌的相容性极差。因此,应用白僵菌制剂防治害虫,选择生物学相容性好的农药以低剂量与白僵菌制剂混用,既可使菌剂增效,又可大幅度降低化学药剂用量。  相似文献   
112.
玉米疯顶病种子传播研究   总被引:2,自引:0,他引:2  
连续3a对不同来源的玉米种子,利用显微镜镜检和试种观察植株发病显症的方法,检测其携带玉米疯顶病病菌状况。结果表明,病株病穗籽粒、病株健穗籽粒、病田健株籽粒都有较高的带菌率。因此,病菌随种子调运远距离传播是造成各地病害突发的主要原因。  相似文献   
113.
转Bt基因棉在安庆市大面积种植后害虫发生特点调查   总被引:6,自引:1,他引:6  
根据调查,转Bt基因棉大面积种植后,棉铃虫、红铃虫发生减轻;棉叶螨发生加重,为害时间延长;甜菜夜蛾、斜纹夜蛾发生面积扩大,为害程度加重。据此初步提出了当地转Bt基因棉害虫防治中应注意的问题和管理对策。  相似文献   
114.
沙棘植物资源的综合利用   总被引:10,自引:0,他引:10  
依据有关沙棘的研究文献,综述了沙棘的形态特征、生物学特征与分布及其生态效益、生化特性、医学用途、饮料、食品、化妆品生产中的应用、饲用价值等,提出了沙棘资源当前与今后开发利用的建议.  相似文献   
115.
β- 氨基丁酸诱导甜( 辣) 椒抗疫病作用的研究   总被引:12,自引:2,他引:12  
 报道了用β- 氨基丁酸( DL-β-aminon-butyric acid, BABA) 喷雾处理辣椒叶片和茎后的诱导抗疫病作用。研究证明: 高浓度BABA ( 1 000 g/mL) 对离体辣椒疫霉病菌无抗菌活性, 用其喷雾处理辣椒的茎叶所诱导的抗疫病作用可完全控制其危害; 用BABA 诱导处理后3 d 接种辣椒疫霉病菌, 辣椒植株开始表达出较高的诱导抗性, 这种抗病作用可持续20 d 以上, 并表现出与数量抗病性相似的特性。  相似文献   
116.
滑菇优良品种筛选试验初报   总被引:1,自引:0,他引:1  
本试验对 6个不同滑菇品种进行了菌丝体生长和制种观察 ;在栽培试验过程中进行了多点小试和中试 ,初选出Ph0 8号和Ph0 6号两个品种。Ph0 8的单盘产量比CK1高出 2 5 8% ,比CK2 高出 35 3% ;Ph0 6的单盘产量比CK1高出 2 1 5 % ,比CK2 高出 30 6 %。它们均属早生品种 ,适合辽宁地区的气候特点 ,在幼菇期菌盖呈半球形、桔红色、附着的粘液多 ,菌柄比对照短 ,菇体健壮 ,符合商品收购和产品加工的要求  相似文献   
117.
AIM: To examine the expression of human endostatin in E.coli, produce its fusion protein antibody and observe its biological activity. METHODS: Endostatin gene was amplified by polymerase chain reaction,recombined with plasmid vector pGEX-2T and induced expression with IPTG.The protein activity was tested by endothelial cell proliferation inhibitory assay.Inclusion body crudely purified was used to generate polyclonal antibody to detect its expression at mouse's liver and kidney etc. RESULTS: The protein expressed was 20kD after digestion by thrombin,it appeared the anti-angiogenesis activity and Western blotting indicated the expression of endostatin in liver and kidney of mouse. CONCLUSION: The successful expression of human endostatin and the preparation of polycolonal antibody indicated its potential application in anti-angiogenesis therapy and diagnosis tumors.  相似文献   
118.
AIM: To study the electrophysiological characteristics of ion channels of stem cell derived cardiomyocytes(SCDC) of mouse. METHODS: Embryonic stem cells of D3 line(ES-D3) were cultured on the MEF feeder layer with BRL conditioned medium, and fetal mouse heart cells(FMHC)were cultured in vitro. Then ES-D3 cells were induced to differentiate into many kinds of cells. SCDC were harvested on day 12 after differentiation initiating and identified by electro-microscope and immunocytochemistry. SCDC and FMHC were prepared for the patch-clamp research. Sodium and calcium currents together were elicited and compared between SCDC and FMHC. RESULTS: The current characteristics of sodium and calcium channels of SCDC were very similar to FMHC. CONCLUSION: The functional expression of ion channels occurred during ES-D3 cells differentiation and the electrophysiological characteristics of sodium and calcium channels of SCDC are very similar to FMHC.  相似文献   
119.
AIM: To investigate the changes of myocardium glycogen content and the relation ship between changes of the myocardial glycogen content and the myocardial function. METHODS: Male Wistar rats were placed in (hypoxia rats) and made to swim in (hypoxia swimming rats) a hypobaxic chamber simulating an altitude of 5 000 m above sea level. The content of myocardium glycogens was determined by colorimetry. RESULTS: The myocardium
glycogen content of rats significantly reduced along with the prolongation of hypoxic exposure and approached to control level in hypoxia swimming rats. The myocardial function of right ventricule was improved significantly compared with control group.CONCLUSION: Moderate exercise (swimming) is beneficial to hypoxic adaptation of rats under the condition of chronic hypoxia.  相似文献   
120.
AIM: To investigate the activity of interleukin-1β converting enzyme in transplanted intracerebral rat gliomas under angiotensin II-induced hypertension chemotherapy. METHODS: The brain tumor model was produced in Wistar rats by stereotaxic inoculation of C6 glioma cells (1×1012 /L). Tumor-bearing rats were treated with carmustine, teniposide and lisplatin (chemotherapy) during angiotensin II-induced hypertension. Then, the survival time of tumor-bearing rats, tumor blood flow, the concentration of drug, volume of gliomas and the activity of interleukin-1β converting enzyme in glioma were examined.RESULTS: The survival time of tumor-bearing rats was significantly longer in chemotherapy with angiotensin II-induced hypertension group than that of chemotherapy alone. In addition, regional tumor blood flow, the concentration of chemotherapeutic drug and the activity of interleukin -1β converting enzyme in transplanted rat gliomas were increased, while the volume of gliomas was decreased in hypertention chemotherapy group compared with chemotherapy alone. CONCLUSION: Chemotherapy with angiotensin II-induced hypertension has a enhancing effect on chemotherapy for improving the drug delivery to tumor tissue by a increased tumor blood flow and enhancing activity of interleukin -1β converting enzyme.  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