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   116885篇
  免费   6295篇
  国内免费   10716篇
林业   7872篇
农学   5789篇
基础科学   5779篇
  11267篇
综合类   57143篇
农作物   7986篇
水产渔业   5416篇
畜牧兽医   18699篇
园艺   8726篇
植物保护   5219篇
  2024年   957篇
  2023年   2497篇
  2022年   5451篇
  2021年   5207篇
  2020年   4996篇
  2019年   4937篇
  2018年   3419篇
  2017年   5692篇
  2016年   3724篇
  2015年   5660篇
  2014年   5995篇
  2013年   7233篇
  2012年   9942篇
  2011年   10235篇
  2010年   9918篇
  2009年   8781篇
  2008年   8771篇
  2007年   7753篇
  2006年   6325篇
  2005年   5020篇
  2004年   3121篇
  2003年   1848篇
  2002年   1997篇
  2001年   1768篇
  2000年   1616篇
  1999年   568篇
  1998年   57篇
  1997年   36篇
  1996年   15篇
  1995年   25篇
  1994年   29篇
  1993年   27篇
  1992年   33篇
  1991年   26篇
  1990年   10篇
  1989年   8篇
  1988年   10篇
  1987年   25篇
  1986年   23篇
  1985年   6篇
  1984年   4篇
  1981年   18篇
  1966年   3篇
  1965年   4篇
  1964年   6篇
  1963年   4篇
  1962年   31篇
  1957年   3篇
  1956年   35篇
  1955年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
南亚热带李新品种‘华蜜大蜜李’   总被引:1,自引:0,他引:1  
 ‘华蜜大蜜李’是从‘三华李’中选育出来的优良新品种, 果实近圆形, 平均单果质量51.5 g, 可溶性固形物含量9%~11% , 酸甜味浓, 肉质软溶, 丰产稳产, 是‘三华李’中的大果品种, 适合于南亚热带山区栽培。在广东6月中下旬果实红熟。  相似文献   
962.
AIM: To investigate the associated proteins and sensitive biomarkers for early diagnosis of colorectal adenocarcinoma by comparing the results of differential proteomic analysis between colorectal adenoma and early malignantly transformed adenoma. METHODS: Two-dimensional gel electrophoresis was used to define patterns of protein expressions of colorectal adenoma and early malignantly transformed adenoma. Proteins expressed differentially among groups were detected, cut out and analyzed by MALDI-TOF/TOF mass spectrometry. RESULTS: Two-dimensional protein maps of colorectal adenoma and early malignantly transformed adenoma were analyzed with gel-analysis software, an average of 1 672 spots in adenoma, 1 732 in early malignantly transformed adenoma were observed. 28 spots of a 1.5-fold change were found, including 15 proteins down-regulated and 13 up-regulated in early malignantly transformed adenoma, in which 23 proteins were identified by mass spectrometry, the rate of identification was 82.14%. 13 differential proteins were attained, 8 were up-regulated and 5 were down-regulated, which was classified to 6 categories, including protease inhibitor, complement, immunoglobulin, keratoproteins, signal transduction protein and function-unknown proteins. CONCLUSION: The changes of serum proteins in early malignantly transformed adenoma from adenoma can be identified by proteomic technology. Proteins detected in the study may provide new biomarkers correlated with biological behavior of colorectal adenocarcinoma.  相似文献   
963.
964.
AIM: To explore the mechanism of mesenteric lymph reperfusion (MLR) aggravates multiple organ injury in superior mesenteric artery occlusion (SMAO) shock rats. METHODS: Male Wistar rats were randomly divided into 4 groups: in sham group, only anesthetization and operation were performed; in MLR group, occlusion of mesenteric lymphatics (ML) for 1 h followed by 2 h of reperfusion; in SMAO group, occlusion of superior mesenteric artery (SMA) for 1 h followed by 2 h reperfusion; in MLR+SMAO group, occlusion of SMA and ML for 1 h followed by 2 h of reperfusion. The homogenates of liver, kidney, myocardium and lung were prepared for determining the activities of free radical, nitric oxide, myeloperoxidase (MPO) and cell membrane ATPase. RESULTS: The MDA, NO contents and NOS, MPO activities of multiple organic homogenate in SMAO and MLR+SMAO group were higher than those in sham and MLR group, and these indexes in MLR+SMAO were increased significantly than those in SMAO group. The SOD and ATPase activities of muliple organic homogenate in SMAO and MLR+SMAO group were lower than those in sham and MLR group, and those in MLR+SMAO group was decreased obviously than those in SMAO group. CONCLUSION: The MLR enhances the multiple organ free radical injury, NO synthesis and release, PMN detention and decreases the activity of cell membrane ATPase, aggravating the major organs injury in SMAO shock rats. Intestinal lymphatic pathway plays an important role in the pathogenesis of SMAO shock.  相似文献   
965.
Myocardium hypertrophy is a compensated response to cardiac disease in which intracellular Ca2+ concentration is elevated, the essential signal that results in hypertrophy. The cardiac sodium-calcium exchanger (NCX) is a bidirectional ion transporter in sarcolemma. The decrease in NCX activity as well as its inverse mode is one of the main mechanisms that contribute to cytosolic Ca2+ loading in hypertrophy. The extracellular signal molecules, the change of Na+ /Ca2+ concentrations and intracellular modulating proteins during cardiac hypertrophy can affect the activity or NCX function, and increase intracellular Ca2+. We summarized the regulatory mechanism of NCX in myocardium hypertrophy.  相似文献   
966.
AIM: To express osteopontin 13 peptide (OPN 13) in E.coli, and to test the biological activity of the purified products. METHODS: cDNA fragments containing RGD sequences were cloned into prokaryotic expression vector pET-32c(+) including His coding sequence to construct pET-32c-OPN 13 plasmid. E.coli DH5α transformed by pET-32c-OPN 13 plasmid was induced by IPTG at different concentrations for different times to identify the optimal induction condition. Expressed His-OPN 13 fusion protein was purified via Ni-NTA His Bind Resin metal chelation chromatography, and detected by VSMCs adhesion and migration analysis. RESULTS: His-OPN 13 fusion protein was expressed in soluble manner. The fusion proteins were purified via Ni-NTA His Bind Resin affinity chromatography. His-OPN 13 fusion protein specifically inhibited adhesion and migration of VSMCs stimulated by osteopontin in dose-dependent manner. CONCLUSION: The OPN 13 peptide is successfully expressed in E.coli DH5α. The purified His-OPN 13 fusion protein could inhibit the adhesion and migration of VSMCs stimulated by osteopontin.  相似文献   
967.
富士苹果AFLP体系的优化及其在鉴定早熟芽变中的应用   总被引:4,自引:0,他引:4  
 以‘长富2号’苹果为材料,采用优化的AFLP技术对其早熟芽变与母株进行初步研究,筛选了64对引物,其中43对引物扩增结果理想,共产生了2,700条带。有4对引物在芽变与母株之间产生了7条差异片段,主要集中在350~800 bp之间。研究表明早熟芽变是由于遗传物质改变造成的,同时也说明利用该体系对苹果芽变进行分析和鉴定获得成功。  相似文献   
968.
969.
褐蘑菇子实体活性多肽提取工艺   总被引:1,自引:0,他引:1  
刘莹 《食用菌》2009,31(4):10-11
采用单因素和正交试验,以水提醇沉的方法来获取褐蘑菇子实体中的活性肽类物质。且根据不同条件下活性多肽的提取量为指标来确定活性多肽的最佳提取条件(料水比1:12、时间6h、温度4℃、pH值7、水醇比1:1.5),旨在为褐蘑菇子实体中蛋白质的开发应用打下基础。  相似文献   
970.
对景洪热带地区独有的少数民族,结合当地自然风貌,尝试将景洪热带地区总结出人与大自然植物景观和谐相处,重视"意"与"匠"的结合,傣族民间园林植物造景与园林其它要素的结合,公园的植物造景特色,重视热带景观的营造5个植物造景的特点,对其进行了分析,并对热带地区园林植物造景研究的意义提出看法.  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