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   963篇
  免费   100篇
  国内免费   108篇
  2024年   2篇
  2023年   40篇
  2022年   38篇
  2021年   65篇
  2020年   45篇
  2019年   56篇
  2018年   56篇
  2017年   48篇
  2016年   61篇
  2015年   46篇
  2014年   65篇
  2013年   74篇
  2012年   43篇
  2011年   44篇
  2010年   48篇
  2009年   61篇
  2008年   47篇
  2007年   74篇
  2006年   43篇
  2005年   36篇
  2004年   33篇
  2003年   28篇
  2002年   21篇
  2001年   17篇
  2000年   17篇
  1999年   7篇
  1998年   7篇
  1997年   14篇
  1996年   2篇
  1995年   5篇
  1994年   3篇
  1993年   1篇
  1992年   3篇
  1991年   11篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1984年   1篇
  1978年   1篇
  1977年   1篇
排序方式: 共有1171条查询结果,搜索用时 15 毫秒
131.
老年性阴道炎是女性绝经后的常见病、多发病,西医认为该病的病因为绝经后或长期闭经后雌激素水平降低,阴道微生态失衡。宏基因组学是近年出现的菌群整体性检测方法,采用宏基因组学技术检测老年性阴道的微观整体状况,将为本病中医证型及疗效评定提供客观精确的量化标准。  相似文献   
132.
目的:观察健脾化瘀中药提高胞嘧啶脱氨酶/单纯疱疹病毒胸苷激酶基因治疗肝细胞癌的作用。方法:脂质体lipofectamine将含有双自杀基因的腺病毒载体pAd-CD/TK导人293细胞,收集病毒上清转染人肝癌细胞BEL7402,MTT法测定BEL7402细胞存活率。裸鼠人肝癌模型转染CD/TK双自杀基因后,给予5-FC500mg/kg,GCV 100mg/kg腹腔注射,同时予健脾化瘀中药960复方灌胃。观察肿瘤生长情况。结果:给予前体药物5-FC和GCV后,CD/TK转染细胞被杀死。并表现出较强的旁观者效应。转染细胞比例达到10%即表现出较强的杀伤作用(P<0.01)。健脾化瘀中药960复方具有提高旁观者效应作用,1.67ml/kg和2.5ml/kg960复方含药血清组细胞存活率显著低于对照组(P<0.01)。转染基因组应用5-FC和GCV治疗后,裸鼠肝癌的生长明显受到抑制(P<0.05),抑瘤率39.42%,单用中药组抑瘤率18.04%,中药与CD/TK 5-FC/GCV联合运用组,较单纯CD/5-FC/HSV-tk/GCV对裸鼠肿瘤模型的生长抑制作用更加明显(P<0.05),抑瘤率55.10%。结伦:腺病毒介导CD/TK自杀基因可有效地杀死人肝癌BEL7402细胞,健脾化瘀中药960复方具有显著提高CD/TK双自杀基因对人肝癌细胞的抑杀作用。  相似文献   
133.
Diverging Understandings of Forest Management in Matsutake Science. As high-value gourmet mushrooms, the matsutake complex of the genus Tricholoma has been the subject of extensive research. This article reviews two trajectories of matsutake research, showing how distinctive regional nodes may develop within a cosmopolitan modern science. The global center of matsutake research is in Japan, where problems of artificial cultivation and the “orchard-style” enhancement of production under forest conditions stimulate basic research. U.S. Pacific Northwest research forms a contrasting regional node, with a focus on sustainable yields in the context of timber production. Regional differences in research design and results point to the importance of distinctive scientific legacies, in this case formed in relation to divergent histories of forest management. Attention to regional distinctions in the framing of scientific problems is particularly important as scientific frameworks are exported to new places; for example, both Japanese and American forms of matsutake science have been extended to China. 高価なグルメきのこであるマツタケとその近縁種群のTricholoma属は広範囲に渡る科学的研究の対象となってきた。本論では二つの地域特徴的なマツタケ研究の軌跡を概観し、文化的差異を超えて世界的に通用する近代科学においても地域固有の関心に応じて特徴のある知識が結節し発展することを示す。マツタケ研究の世界的な中心地である日本では人工増殖やマツタケを殖やすための「果樹園的」な山林作りへの関心が基礎研究の方向性に刺激を与えてきた。一方日本とは対照的に、米国北西岸州では木材の持続的産出に主眼をおいた山林管理の流れの中で研究が進んできた。こうした研究計画や結果的に得られる知識の違いは、地域ごとに特徴のある科学的遺産 - 本件の場合は森林管理の歴史が多様に枝分かれしていること - に注目することが重要であることを知らせてくれる。近年日本や米国で発展したマツタケ研究の方法や成果が中国での研究にも影響を与えているが、特に新しい研究の場を広げる場合には科学的な関心、問題がどのような枠組で組み立てられるか地域によって多様であることを考慮することが重要である。  相似文献   
134.
云南省香格里拉大峡谷藏族神山在自然保护中的意义   总被引:12,自引:1,他引:11  
位于云南省西北部迪庆藏族自治州境内的香格里拉大峡谷拥有独特的自然人文景观和丰富的生物多样性。藏族作为当地最重要的原住民族,他们的文化对当地的自然环境具有重要的影响。为了解藏族传统文化中的神山崇拜对香格里拉大峡谷地区自然环境的影响,本文应用民族生态学、植物生态学和文化人类学的研究方法,结合文献资料的分析,对香格里拉大峡谷的藏族神山进行了调查和研究,并对处于不同保护状态下(神山与非神山)的两个典型植物群落即高山松(Pinus densata)群落和云南黄果冷杉(Abies ernestii var. salouenensis)群落进行了比较。结果显示,在相同的样地面积内(20 m×20 m),神山植物群落在物种数量(20,14)和群落盖度(100%,85%)方面都明显高于非神山植物群落(11,2;70%,60%)。结合入户调查资料,发现广泛分布于香格里拉大峡谷的藏族神山构成了一个“自下而上”的乡土保护体系,它不仅在保护生物多样性、维护当地脆弱的生态环境等方面发挥着重要的作用,而且还可以提供多种非林产品,实现多种生态功能。文章探讨了发挥乡土保护体系的保护功效及应用传统文化知识以促进自然保护的重要性,建议应当尊重和保护原住民的传统文化,发掘其中优秀的自然保护知识和经验,引导其发挥更加有效的自然保护功能,使民族传统保护体系成为现代自然保护体系的有力补充。  相似文献   
135.
Heterogeneity of ginsenosides is an interesting and important issue because those structure-similar secondary metabolites have different or even totally opposite pharmacological activities. In this work, a new enzyme UDP-glucose:ginsenoside Rd glucosyltransferase (UGRdGT), which catalyzes the formation of ginsenoside Rb1 from ginsenoside Rd [Biotechnol. Bioeng. 89: 444–52, 2005], was purified approximately 145-fold from suspended cells of Panax notoginseng with an overall yield of 0.2%. Purification to apparent homogeneity, as judged by SDS-PAGE, was successfully achieved by using sequential ammonium sulphate precipitation, anion-exchange chromatography and native PAGE. The enzyme had a molecular mass of 36 kDa, and its activity was optimal at pH 8.5 and 35 °C. The enzyme activity was enhanced by Mn2+, Ca2+ and Mg2+, but strongly inhibited by Zn2+, Hg2+, Co2+, Fe2+ and Cu2+. The apparent Km value for UDP-glucose and ginsenoside Rd was 0.32 and 0.14 mM, respectively. The biotransformation yield from ginsenoside Rd to Rb1 by UGRdGT in 50 mM Tris–HCl buffer at pH 8.5 and 35 °C was over 80%. This work provides a basis for further molecular study on the ginsenoside Rb1 biosynthesis by P. notoginseng cells and it is also useful for potential application to in vitro biotransformation from ginsenoside Rd to Rb1.  相似文献   
136.
Ranges of species are dynamic and respond to long‐term climate change and contemporary effects such as habitat modification. We report here that moose (Alces alces) have recently colonized coastal temperate rainforests of British Columbia, Canada. Contrary to recent publications, field observations of moose and their sign, combined with their occurrence in wolf (Canis lupus) faeces, suggest that moose are now widespread on the coastal mainland and occur on least three islands. Traditional ecological knowledge (information accumulated by aboriginal peoples about their environment) suggests that colonization occurred during the mid 1900s, concomitant with logging of major watersheds that bisect the Coast Mountain Range. Range expansion by moose may have ecological consequences such as alteration of predator–prey dynamics and transmission of disease to native deer (Odocoileus hemionus).  相似文献   
137.
Building resilience in integrated human and nature systems or social–ecological systems (SES) is key for sustainability. Therefore, developing ways of assessing resilience is of practical as well as theoretical significance. We approached the issue by focusing on the local level and using five lagoon systems from various parts of the world for illustration. We used a framework based on four categories of factors for building resilience: (1) learning to live with change and uncertainty; (2) nurturing diversity for reorganization and renewal; (3) combining different kinds of knowledge; and (4) creating opportunity for self-organization. Under each category, the cases generated a number of items for building resilience, and potential surrogates of resilience, that is, variables through which the persistence of SES emerging through change can be assessed. The following factors were robust across all five lagoon SES cases: learning from crisis, responding to change, nurturing ecological memory, monitoring the environment, and building capacity for self-organization and conflict management.  相似文献   
138.
Objective: Childhood obesity is one of the most challenging issues facing healthcare providers today. The aims of this study were to describe the ambulatory management of childhood obesity by pediatricians (PDs) and family physicians (FPs) and to evaluate knowledge of and adherence to published recommendations. Research Methods and Procedures: A 42‐item, self‐administered questionnaire was mailed to 1207 randomly selected primary care physicians (PDs = 700, FPs = 507) between September 2001 and January 2002. Results: Of 339 (28%) responses, 287 were eligible (PDs = 213, FPs = 74). Most respondents were in group or solo practice (87%) in a suburban or urban, non‐inner city location (67%). The average age was 48 years (range = 31 to 85 years), and the mean years in practice was 17 (range = 1 to 55 years). Nineteen percent of physicians were aware of national recommendations. Three percent of physicians reported adherence to all recommendations. Knowledge of recommendations was not associated with a greater likelihood of adherence. However, physicians who were aware of recommendations were more likely to have positive attitudes about personal counseling ability (odds ratio = 2.4, confidence interval = 1.3 to 4.4) and the overall efficacy of obesity counseling (odds ratio = 4.3, confidence interval = 1.7 to 10.8). Poor patient motivation, patient noncompliance, and treatment futility were perceived as the most frequently encountered barriers to obesity treatment. Discussion: Most physicians are not aware of or adherent to national recommendations regarding childhood obesity. Awareness of recommendations was associated with more positive attitudes about personal counseling ability and the effectiveness of obesity counseling in general.  相似文献   
139.
中药复方保肝作用的组织化学、免疫组织化学研究   总被引:4,自引:0,他引:4  
目的为观察活血化瘀类保肝中药复方对肝损伤的保肝作用,并探讨其抗肝纤维化作用机制.方法采用组织化学酶显示法和免疫组织化学方法,经图像分析系统定量测定对照组、模型组、预防组、治疗组和自然恢复组各组动物标本中琥珀酸脱氢酶,5-核苷酸酶及热休克蛋白70活性与表达程度.结果琥珀酸脱氢酶、5-核苷酸酶活性和热休克蛋白70的表达模型组与对照组比P<0.01;自然恢复组、预防组与模型组比P<0.01;治疗组与自然恢复组比P>0.05.结论活血化瘀类中药复方具有一定的保肝功效.肝星形细胞热休克蛋白70的表达是否提示细胞凋亡的发生,将有待进一步研究.  相似文献   
140.
中药"神曲"对脾虚小鼠肠道菌群的调整及肠保护作用研究   总被引:4,自引:1,他引:3  
目的研究中药"神曲"对脾虚小鼠肠道菌群的调整及肠保护作用.方法1.昆明小白鼠,分成4组:A组(正常对照组),B组(脾虚自然恢复组),C组(神曲治疗组),D组(丽珠肠乐治疗组).2.检测结肠内容物和粪便标本的肠杆菌、肠球菌、双歧杆菌、类杆菌和乳酸杆菌数量.3.结肠组织光镜和电镜观察.结果脾虚小鼠给予神曲水煎剂治疗后,肠杆菌、肠球菌、双歧杆菌、类杆菌和乳酸杆菌数量逐渐恢复正常,肠壁肌层厚度增加,杯状细胞数量增多,肠黏膜微绒毛排列紊乱、线粒体肿胀显著改善,明显好于自然恢复组,与丽珠肠乐治疗组相比差异无显著性.结论中药神曲对脾虚小鼠具有肠道菌群调整及促进损伤肠组织恢复的作用.  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