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   1146篇
  免费   115篇
  国内免费   399篇
  2024年   6篇
  2023年   42篇
  2022年   61篇
  2021年   70篇
  2020年   60篇
  2019年   73篇
  2018年   53篇
  2017年   54篇
  2016年   79篇
  2015年   65篇
  2014年   89篇
  2013年   81篇
  2012年   58篇
  2011年   77篇
  2010年   59篇
  2009年   49篇
  2008年   52篇
  2007年   72篇
  2006年   80篇
  2005年   72篇
  2004年   67篇
  2003年   56篇
  2002年   48篇
  2001年   38篇
  2000年   25篇
  1999年   23篇
  1998年   14篇
  1997年   15篇
  1996年   22篇
  1995年   7篇
  1994年   5篇
  1993年   11篇
  1992年   7篇
  1991年   8篇
  1990年   13篇
  1989年   5篇
  1988年   3篇
  1987年   4篇
  1986年   5篇
  1985年   7篇
  1984年   3篇
  1983年   5篇
  1982年   4篇
  1981年   4篇
  1980年   7篇
  1979年   2篇
排序方式: 共有1660条查询结果,搜索用时 15 毫秒
41.
目的:探讨术前访视应用ipad在术前访视中对手术患者心理状态的影响。方法:将300例择期手术患者随机分为对照组(150例)和实验组(150例),对照组采用常规术前访视方案;实验组在此基础上结合ipad展示围术期相关信息,采用焦虑自量表评估两组病人入院时和入手术室时的焦虑状况及血压、心率等指标,并且进行术后并发症和满意度的调查。结果:改良术前访视后焦虑评分、收缩压、舒张压、心率实验组明显低于对照组。结论:术前访视应用ipad可明显减轻手术病人术前的焦虑。  相似文献   
42.
近年来,埃博拉病毒(EBOV)因其在非洲造成的严峻疫情而引起了广泛关注。本文对涉及埃博拉病毒检测与防治技术方面的在中国申请的国内外专利申请数量、年代分布、技术发展状况等信息进行分析,对国内埃博拉病毒检测、免疫、治疗相关专利技术进行简要总结,并对目前热点关注药物(jk-05,ZMapp,VSV-EBOV)专利申请信息进行比较概括,结果表明,我国申请人在提出的相关专利申请数量以及技术多样性上与国外申请人存在差距,为国内科研人员提供了相关技术领域参考。  相似文献   
43.
Leaching of metals due to enhanced mobility during ethylenediaminetetraacetic acid (EDTA)-assisted phytoextraction has been demonstrated as one of the potential hazards associated with this technology. This study was conducted to determine phytoextraction efficiency of Chenopodium album L. for Pb and EDTA-assisted (1.5, 3, and 9 mmol kg?1) phytoextraction and potential for leaching of Pb. The results demonstrated that BCFshoot (bioconcentration factor) was relatively higher than the BCFroot. Translocation factor in the shoot was higher than the roots. Thus, plant species would be applicable for Pb phytoextraction. EDTA enhanced translocation of Pb from roots to shoots. Lead content in the plant parts was maximum in the shoot and root of 9EDTA and 3EDTA, respectively. However, there was no significant difference between 3EDTA and 9EDTA. Lead concentration in the plant parts increased significantly from vegetative stage into flowering stage. Lead content taken up by the plant was lowest when EDTA was applied in a single dose. Therefore, application of EDTA in several increments rather than a single split reduced the leaching risk. Totally, optimum phytoextraction was observed when 3 mmol kg?1 EDTA was added in triple dosage 60 days after the plant cultivation under triple application mode. The results indicated the plant has the potential for Pb phytoextraction, but it should not be used unless the biomass containing such accumulated metal is removed for disposal. Significant improvement over current ETDA-assisted phytoextraction of Pb may be possible but should be implemented cautiously because of environmental risk.  相似文献   
44.
Binding and energy transfer of an erbium ion with rhaponticin (RH) was investigated and a simple spectrofluorimetric method was developed for determination of RH using an Er3+ probe. Results using spectra, chromatography and density functional theory (DFT) indicated that binding of Er3+ to RH occurred at the hydroxyl group of C‐11 and at the methoxy group at C‐12 of the conjugated aromatic ring through hydrogen bonding. Resonance energy transfer (RET) occurred from intramolecular charge transfers (ICT), the binding of RH to Er3+ ion induced fluorescence enhancement (FE) of the Er3+ ion. This method was applied to the pharmacokinetic detection of RH. The main advantages of the proposed method compared with previously reported ones are its simplicity and lower cost. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
45.
随着重症医学的发展,血流动力学监测也受到越来越多的关注。准确判断患者血流动力学变化能指导临床医生做出正确的治疗措施。在重症患者中,患者的前负荷,后负荷及心肌收缩力均发生巨大改变且三者相互影响。在这种情况下,准确判断患者血流动力学变化是临床工作中面临的重大挑战。目前临床上,很多血流动力学监测设备正在使用,帮助临床医生做出准确判断。近十年来,血流动力学监测从有创向微创甚至无创的方向发展,由短时监测向长时连续监测的方向发展。无创血流动力学监测设备因其操作简单及无创伤性在临床使用越来越广泛。本文主要回顾分析临床中常用几种无创血流动力学监测仪,介绍它们的作用原理,及各自的优缺点。  相似文献   
46.
The ability of the classic tumour‐suppressive let‐7 family to inhibit carcinogenesis, tumour progression, recurrence and pluripotency of cancer stem cells has generated significant interest in the field of cancer research. Through suppressing and degrading downstream‐targeted mRNAs, let‐7 affected most aspects of cell biology. It is perplexing how let‐7 affects oncogenesis, as the large influx of new miRNAs and other kinds of non‐coding RNAs are continuously defined. In this review, we delineate the complex functions of let‐7 and discuss the future direction of let‐7 research.  相似文献   
47.
与常规治疗药物相比,抗体药物具有靶向性强、特异性好等优点,其作为一类重要的治疗性药物,近年来在临床中的应用逐渐增多,为疾病的治疗提供了新的选择,应用范围逐渐从肿瘤、自身免疫性疾病及慢性炎症扩展到心血管和感染性等疾病中。人源抗体的全部结构是由人类抗体基因所编码的,因此避免了异种蛋白长期应用引起的不良反应,加之人源抗体制备技术的不断发展完善,使其逐渐成为治疗性抗体研发的首要选择。综述了近年来治疗性人源抗体的主要制备技术及其在临床中应用的最新进展,同时探讨了人源抗体制备技术的不足之处,以期为人源抗体的发展提供借鉴和思路。  相似文献   
48.
In the present study, field micro-plot experiments were conducted to investigate the basal and foliar application of a tested organic fertilizer amendment (OFA) for decreasing the risk of Cd accumulating in rice. The results showed that applications of OFA significantly increased rice yields in Cd-polluted soil and reduced the level of Cd in rice plants, especially in rice grain. In addition, three application methods of OFA were investigated (single basal application (B1, B2, and B3), combined basal application (+LM, +D, and +Z), and foliar application (F1, F2)). Treat B, F, +LM, +D were all higher than control on rice yield with 25.03, 28.05, 30.61, 22.50 g pot?1 on average, respectively. Among which, rice cadmium depress to 0.33 mg kg?1 in foliar application is considered to be a more efficient and economical method of heavy metal remediation. The mechanism of foliar application to alleviate the accumulation of Cd in brown rice may be related to the probable Cd sequestration in the leaves and straws. And the doses of the foliar application were 2.25–3.75 kg hm?2, approximately 1.0–2.5% of the basal application amount yet with more effect (0.10 mg kg?1 more than single basal; 0.23 mg kg?1 more than combined basal) on Cd reduction.  相似文献   
49.
Conservation genetics is a well‐established scientific field. However, limited information transfer between science and practice continues to hamper successful implementation of scientific knowledge in conservation practice and management. To mitigate this challenge, we have established a conservation genetics community, which entails an international exchange‐and‐skills platform related to genetic methods and approaches in conservation management. First, it allows for scientific exchange between researchers during annual conferences. Second, personal contact between conservation professionals and scientists is fostered by organising workshops and by popularising knowledge on conservation genetics methods and approaches in professional journals in national languages. Third, basic information on conservation genetics has been made accessible by publishing an easy‐to‐read handbook on conservation genetics for practitioners. Fourth, joint projects enabled practitioners and scientists to work closely together from the start of a project in order to establish a tight link between applied questions and scientific background. Fifth, standardised workflows simplifying the implementation of genetic tools in conservation management have been developed. By establishing common language and trust between scientists and practitioners, all these measures help conservation genetics to play a more prominent role in future conservation planning and management.  相似文献   
50.
同一组织中的细胞往往具有类似的结构和功能,然而通过对单个细胞进行测序分析后,发现每个细胞都具有一定异质性.单细胞全基因组扩增技术是进行单细胞测序的前提,该技术可用于揭示单细胞基因组结构差异,同时在肿瘤研究、发育生物学、微生物学等研究中发挥重要作用,并成为生命科学研究技术的热点之一.单细胞全基因组扩增技术的难点在于单细胞的分离和全基因组的扩增.本文介绍了单细胞全基因组扩增技术中常用的单细胞分离技术和单细胞全基因组扩增技术,并对各技术间的优缺点进行比较,同时着重讨论该技术在肿瘤研究、发育生物学和微生物学研究中的应用.  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