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   213篇
  免费   9篇
  国内免费   54篇
  2023年   1篇
  2022年   5篇
  2021年   11篇
  2020年   10篇
  2019年   5篇
  2018年   3篇
  2017年   5篇
  2016年   10篇
  2015年   13篇
  2014年   20篇
  2013年   18篇
  2012年   15篇
  2011年   23篇
  2010年   11篇
  2009年   3篇
  2008年   12篇
  2007年   8篇
  2006年   10篇
  2005年   13篇
  2004年   12篇
  2003年   11篇
  2002年   4篇
  2001年   6篇
  2000年   2篇
  1999年   7篇
  1998年   5篇
  1997年   4篇
  1996年   2篇
  1994年   2篇
  1993年   8篇
  1992年   9篇
  1991年   3篇
  1990年   1篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
排序方式: 共有276条查询结果,搜索用时 250 毫秒
71.
北五味子的果实解剖研究   总被引:2,自引:0,他引:2  
王立军  谷安根 《植物研究》1992,12(4):383-388
采用不同花期的子房与花谢后的果实解剖制片为材料,综合研究结果,明确北五味子的雌花,其离生心皮雌蕊群呈螺旋状着生在圆顶状的花托上。每一个单雌蕊均由鸡冠状柱头与下面膨大的子房构成。花柱缺如。子房有自背缝线上发生的假隔膜隔开,致将子房形成假二室;胚珠倒生乃至弯生,亚边缘胎座(submarginal placenta),受精后发育成旋生聚合浆果(spiral-baccacetum),内含种子1-3(2)枚。种子属双子叶有胚乳种子,胚甚小,约为种子的1/50。  相似文献   
72.
对河北邯郸地区的抗性棉铃虫(Helicovrpa armigera H(?)bner)种群不同发育阶段乙酰胆碱酯酶(AChE)对灭多威和对氧磷的敏感磷的敏感度结果表明:4-5龄幼虫的AChE在棉铃虫整个发育期中敏感度是最低的,成虫期的AChE最敏感,蛹期AChE平均敏感度低于幼虫期。用甲基对硫磷和灭多威以LD_5的诱导剂量和LD_(50)的选择剂量处理棉铃虫幼虫后,AChE对底物的亲和力和对抑制剂的敏感度发生了明显的变化,水解β-乙酸萘酯的羧酸酯酶对底物的亲和力明显提高,而水解α-乙酸萘酯的羧酸酯酶对底物的亲和力在处理后24小时无明显改变。谷胱甘肽-S-转移酶活性,低剂量诱导组最高降低至78%和43%,而高剂量选择组提高15%,诱导组和选择组对底物的亲和力均明显降低,处理的剂量和处理后时间明显地影响棉铃虫磷酸酯酶的活性及其对底物的亲和力。  相似文献   
73.
Options for patients with relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL) after brentuximab vedotin (Bv) and autologous stem cell transplantation (ASCT) are limited. Immune checkpoint inhibitors (ICI) are active in this population but rarely induce complete response (CR). Ten patients with R/R cHL after ASCT and Bv received pembrolizumab (n?=?8) or nivolumab (n?=?2). Five had been previously exposed to 5-azacitidine on a phase 1 study. Among nine evaluable patients, seven (78%) achieved CR, one partial response, and one reduction of tumor burden. All five patients who had received 5-azacitidine prior to ICI achieved CR, while only two of four who did not receive prior 5-azacitidine achieved CR. At a median follow-up of 9.9 months [0.5–14.3], eight patients are alive and five are still receiving treatment. We documented an unprecedented CR rate after ICI in patients with R/R cHL. We hypothesize that hypomethylating agents might have an immune priming effect and enhance the efficacy of ICI.  相似文献   
74.
通过对异珊瑚形态构造特征分析,进一步阐明了隔壁的发生方式、隔壁发育阶段、隔壁生长的变演性、隔壁基端与外壁的关系、隔壁的微细构造及其所含的化学成份,枝体表壁和壁面上的构造物特征,横板的形态及枝体繁殖的方式.通过异珊瑚生长特征的分析,探讨了它们的生活环境.结合地层资料归纳了异珊瑚的时空分布并将异珊瑚重新归纳为6科2亚科16属.  相似文献   
75.
Charged MVB protein 5 (CHMP5) is a coiled coil protein homologous to the yeast Vps60/Mos10 gene and other ESCRT-III complex members, although its precise function in either yeast or mammalian cells is unknown. We deleted the CHMP5 gene in mice, resulting in a phenotype of early embryonic lethality, reflecting defective late endosome function and dysregulation of signal transduction. Chmp5-/- cells exhibit enlarged late endosomal compartments that contain abundant internal vesicles expressing proteins that are characteristic of late endosomes and lysosomes. This is in contrast to ESCRT-III mutants in yeast, which are defective in multivesicular body (MVB) formation. The degradative capacity of Chmp5-/- cells was reduced, and undigested proteins from multiple pathways accumulated in enlarged MVBs that failed to traffic their cargo to lysosomes. Therefore, CHMP5 regulates late endosome function downstream of MVB formation, and the loss of CHMP5 enhances signal transduction by inhibiting lysosomal degradation of activated receptors.  相似文献   
76.
77.
Plant leaf is a natural composite biomaterial, and its strength is closely related to the microstructure. In this paper, themechanical characteristics of eight species of plant leaves were investigated and analyzed. The ultimate strength of leaves andthe hardness of leaf surfaces were measured by using universal testing machine and nanoindenter tester, respectively. The tensilestrength of the parallel microstructure was investigated based on its cross-sectional mechanical model. The results of tensiontests indicate that the ultimate strength of a leaf is related to the material composition and structure. The coriaceous leavesusually exhibit higher tensile strength. For example, the Phyllostachys pubescens leaf can achieve the maximum ultimatestrength of 5.9091 N·mm-2. It is concluded from the results of hardness tests that material components of leaf surface caninfluence the surface hardness evidently. The leaf surface composed of more lignin and cellulose materials shows a highersurface hardness than that composed of more carbohydrates materials.  相似文献   
78.
The essential oils from two Chinese endemic Meconopsis species, i. e., M. punicea and M. delavayi, were analyzed by using GC-MS for the first time. The major constituents were hexadecanoic acid (16.8%), 1,2-dimethyl naphthalene (11.4%), 1,4-dimethyl naphthalene (6.6%), 1,3-dimethyl-5-ethyl naphthalene (5.9%), and 3-methyl biphenyl (5.6%) for M. punicea, and hexadecanoic acid (9.9%), 1,2-dimethyl naphthalene (7.9%), 1,3-dimethyl-5-ethyl naphthalene (6.2%), tetradecane (5.9%), and hexyl cinnamaldehyde (5.5%) for M. delavayi.  相似文献   
79.
Essential hypertension (EH) is thought to result from theinteraction of environmental and genetic factors. The molecular genetics of EH has witnessed considerable progress during the past few years. However, the number of genes involved, their chromosomal location and the magnitude of their effect on EH susceptibility are unknown. We conducted the present study to screen susceptibility genes to essential hypertension using a genome-wide scanning method in a group of Han people from Fangshan district located in the southwest of Beijing. A case-control study and affected sibpair were performed. Genotyping was carried out using a fluorescence-based semiautomated technique on automated DNA sequencer (ABI 377, PE). The basis for the genome-screen was the ABI prism linkage mapping sets of 400 microsatellite markers (version 2, PE, Co.). PCR for amplification of markers was carried out as multiplex reactions with Ampli Taq gold (PE, Co.) following protocols developed in our laboratory. Data were exported as a text file from genotyper for subsequent two-point affected sibpair linkage analysis. The data from case-control association study showed a linkage disequilibrium between EH and marker D1S249 locus (X2 = 14.6, P = 0.002). There are 12 alleles in the D1S249 locus. The frequency of A9 allele in hypertension was higher than in normotensives, (13.6% v.s. 2.7%, X2 = 6.30, p = 0.01, OR = 4.57, 95%CI = 1.24-25.4). The data from two-point affected sibpair linkage analysis demonstrated a linkage between EH and A9 allele, P<0.05. It suggested that microsatellite marker D1S249 locus might be associated with the genetic susceptibility to essential hypertension in Han Chinese.  相似文献   
80.
水蜡蛾一新属一新种:(鳞翅目:水蜡蛾科)   总被引:2,自引:0,他引:2  
Brahmaea属是Walker(1855)以Bombyx certhia Fabricius为模式种成立的。Mell(1929)根据成虫形态特征、后翅翅脉的差异(有无连接Sc+R_1和Rs脉的横脉),将亚洲的水蜡蛾分为二群,建立一个新亚属 Brahmophthalma Mell并绘有Brahmaea Walker属与新亚属内每个种的翅脉简图以示区别;Bryk(1949)将Brahmophthalma提升为属。我们在整理和研究水蜡蛾的标本中,发现Brahmaea Walker属中实际存在着成虫形态和外生殖器差别很大的两个类群,作者认为有必要将其分为两个属,建立一个新属,并记述一新种。  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