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   117篇
  免费   6篇
  国内免费   2篇
  125篇
  2024年   1篇
  2023年   1篇
  2022年   1篇
  2021年   7篇
  2020年   2篇
  2019年   3篇
  2018年   3篇
  2017年   1篇
  2016年   3篇
  2015年   3篇
  2014年   6篇
  2013年   7篇
  2012年   2篇
  2011年   2篇
  2010年   4篇
  2009年   1篇
  2008年   7篇
  2007年   2篇
  2006年   4篇
  2005年   2篇
  2004年   9篇
  2003年   6篇
  2002年   4篇
  2001年   3篇
  2000年   3篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1993年   3篇
  1992年   2篇
  1991年   3篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1984年   5篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1974年   1篇
  1973年   1篇
排序方式: 共有125条查询结果,搜索用时 15 毫秒
71.
According to recent molecular phylogenetic data, the rare Australian endemic Maundia triglochinoides does not form a clade with taxa traditionally classified as members of Juncaginaceae. Therefore, views on the morphological evolution and taxonomy of Alismatales require re‐assessment. As the morphology of Maundia is poorly known and some key features have been controversially described in the literature, the flowers, fruits, inflorescence axes and peduncles were studied using light and scanning electron microscopy. Inflorescences are bractless spikes with flowers arranged in trimerous whorls. Except in the inflorescence tip (where the flower groundplan is variable), flowers possess two tepals in transversal‐abaxial positions, six stamens in two trimerous whorls and four carpels in median and transversal positions. Fruits are indehiscent. The shared possession of orthotropous ovules supports the molecular phylogenetic placement of Maundia as sister to a large clade including Potamogetonaceae and related families. Maundia and Aponogeton spp. share the same highly unusual floral groundplan, a homoplastic similarity that can be explained by spatial constraints in developing inflorescences. The nucellar coenocyte of Maundia appears to be unique among monocots. As Maundia exhibits a mosaic of features characteristic of other families of tepaloid core Alismatales, its segregation as a separate family is plausible. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 12–45.  相似文献   
72.
A standard aqueous extract of Mangifera indica L., used in Cuba as antioxidant under the brand name VIMANG, was tested in vivo for its anti-inflammatory activity, using commonly accepted assays. The standard extract of M. indica, administered orally (50-200mg/kg body wt.), reduced ear edema induced by arachidonic acid (AA) and phorbol myristate acetate (PMA) in mice. In the PMA model, M. indica extract also reduced myeloperoxidase (MPO) activity. In vitro studies were performed using macrophage cell line J774 stimulated with pro-inflammatory stimuli lipopolysaccharide-interferon gamma (LPS-IFNgamma) or calcium ionophore A23187 to determine prostaglandin PGE(2) or leukotriene LTB(4) release, respectively. The extract inhibited the induction of PGE(2) and LTB(4) with IC(50) values of 21.7 and 26.0microg/ml, respectively. Mangiferin (a glucosylxanthone isolated from the extract) also inhibited these AA metabolites (PGE(2), IC(50) value=17.2microg/ml and LTB(4), IC(50) value=2.1microg/ml). These results represent an important contribution to the elucidation of the mechanism involved in the anti-inflammatory and anti-nociceptive effects reported for the standard extract of M. indica VIMANG.  相似文献   
73.
In this paper, mechanical properties of the anterior malleolar ligament (AML) of human middle ear were studied through the uniaxial tensile, stress relaxation and failure tests. The digital image correlation (DIC) method was used to assess the boundary effect in experiments and calculate the strain on specimens. The constitutive behavior of the AML was described by a transversely isotropic hyperelastic model which consists of a first-order Ogden model augmented by a I (4)-type reinforcing term. The material parameters of the model were estimated and the viscoelasticity of the AML was illustrated by hysteresis phenomena and stress relaxation function. The mechanical strength of the AML was obtained through the failure test and the mean ultimate stress and stretch ratio were measured as 1.05 MPa and 1.51, respectively. Finally, a linear Young's modulus-stress relationship of the AML was derived based on constitutive equation of the AML within a stress range of 0-0.5 MPa.  相似文献   
74.
A subtracted cDNA library forDavidia involucrata was constructed using suppression subtractive hybridization (SSH). mRNA isolated from young leaves was used as a “driver,” and mRNAs isolated from young bracts were used as “testers.” The differentially expressed cDNA fragments in bracts were identified by differential screening. Of the 16 clones selected randomly from the screened library, 8 were known genes found in GenBank, and 2 had no similar sequences. Northern blot analysis revealed that the expression level of P1A5 cDNAs selected randomly was dominantly expressed in bracts. This indicates that SSH can be used to clone differentially expressed cDNAs inD. involucrata bracts.  相似文献   
75.
目的 分析慢性化脓性中耳炎(CSOM)患者耳道分泌物的病原菌分布及其药敏情况,为临床合理应用抗菌药物提供参考。方法 收集浙江省立同德医院100例(116耳)CSOM患者耳道分泌物标本进行常规病原菌分离、鉴定及药敏试验。结果 116耳中有97耳培养出病原菌,检出率为83.6%。共检出病原菌103株,其中革兰阳性菌占53.4%(55/103),革兰阴性菌占41.7%(43/103),真菌占4.9%(5/103)。金黄色葡萄球菌和表皮葡萄球菌对青霉素和磺胺甲恶唑/甲氧苄啶耐药性较高,对利福平和莫西沙星敏感性较高,对呋喃妥因和万古霉素完全敏感。铜绿假单胞菌和肺炎克雷伯菌对头孢唑啉、氨苄西林、头孢吡肟、头孢曲松、哌拉西林/舒巴坦耐药性均较高,对妥布霉素、氨曲南、哌拉西林/他唑巴坦敏感性较高,对阿米卡星、美罗培南及亚胺培南完全敏感。真菌对氟胞嘧啶、两性霉素B及制霉菌素均敏感,而对酮康唑和氟康唑有一定的耐药性。结论 CSOM患者耳道分泌物中病原菌以金黄色葡萄球菌、表皮葡萄球菌、铜绿假单胞菌及肺炎克雷伯菌为主,这4种病原菌对多数常用抗菌药物有较强的耐药性,治疗时需根据细菌培养及药敏分析结果合理选用抗菌药物。  相似文献   
76.
77.
78.
Summary The distribution and origin of nerve fibers of presumed sensory nature in the ear drum and middle-ear mucosa of the rat were studied by a retrograde tracing technique in combination with immunocytochemistry.Application of True Blue (TB) on the ear drum or on the middle-ear mucosa labeled nerve cell bodies in the jugular, trigeminal, geniculate and cervical dorsal root ganglia (C2–C4). Judging from the number of TB-labeled nerve cell bodies the jugular and trigeminal ganglia contributed the major component to the sensory innervation of the ear drum and the middle-ear mucosa, while the contribution from the geniculate and cervical dorsal root ganglia was relatively minor.The majority of the TB-labeled nerve cell bodies contained calcitonin gene-related peptide (CGRP), whereas minor populations stored substance P (SP) and neurokinin A (NKA). Nerve fibers containing SP, NKA and CGRP were moderate in number in the middle-ear mucosa and few in the ear drum. Double immunostaining revealed that SP invariably coexisted with NKA in nerve cell bodies in the ganglia examined. The SP/NKA-containing nerve cell bodies constituted a subpopulation of those storing CGRP.The findings indicate that several ganglia project to the ear drum and middle-ear mucosa and that many neuropeptides are involved in the mediation of middle-ear sensitivity.  相似文献   
79.
草麻黄雌性生殖器官的个体发生和畸形式样研究   总被引:2,自引:1,他引:2  
杨永 《Acta Botanica Sinica》2001,43(10):1011-1017
用扫描电镜观察并分析了草麻黄(Ephedra sinica Stapf)雌性生殖器官的个体发生及畸形式样。该种雌球花个体发生式样与麻黄属其他具双胚朱球果的类群基本一致。外珠被以一对近轴侧突起物出现以及该突起物与苞片成交互排列的发育式样支持前人关于该构造叶性本质的论述,而内珠被与珠心的发育相关,因此可能是真正的珠被,基于返祖性畸形三胚珠球花的出现及其他形态特征,认为麻黄属胚珠数目减少是该属内物种特化的一个趋势;利用雌球花发育的畸形现象及外珠被的形态学本质提出麻黄属的雌球果为复轴性构造,雌性生殖单位是由类似于科达类的次级生殖枝构造经系统发育变态,融合,简化成现存的生胚珠构造式样,每一可育苞片及其腋内雌性生殖单位共同组成了麻黄属的苞鳞-种鳞复合体。  相似文献   
80.
Detailed enzymatic properties of the ureido ring synthetase purified from Pseudomonas graveolens were investigated. Nucleotide specificity studies indicated that CTP, UTP, GTP, and ITP were each tenth to one-fifth as active as ATP. The effect of substrate concentration was examined. The Km values for 7,8-diaminopelargonic acid, biotin diaminocarboxylic acid, NaHCO3, ATP, and MgCl2 were 1 × 10?4 M, 4 × 10?5 M, 1 × 10?2 m, 5 × 10?5 M, and 3 × 10?3 M, respectively. It was elucidated that only ADP was produced from ATP in both the reaction of desthiobiotin synthesis from 7,8-diaminopelargonic acid and biotin synthesis from biotin diaminocarboxylic acid. The reaction was remarkably inhibited by Ni2+, Cd2+, Cu2+, Ag+, and As3+, while Mn2+ remarkably enhanced the enzyme reaction. The reaction was remarkably inhibited by metal-chelating reagents. It was elucidated that ADP had a competitively inhibiting effect on this enzyme reaction. 7,8-DiaminopeIargonic acid, which is the substrate for the desthiobiotin synthesis, competitively inhibited the biotin synthesis from biotin diaminocarboxylic acid. The stoichiometry of the desthiobiotin synthesis indicated that the formation ratio of desthiobiotin to ADP was 1 to 1.  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