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   15902篇
  免费   1631篇
  国内免费   1189篇
电工技术   600篇
技术理论   1篇
综合类   1432篇
化学工业   2157篇
金属工艺   611篇
机械仪表   962篇
建筑科学   1781篇
矿业工程   392篇
能源动力   537篇
轻工业   866篇
水利工程   438篇
石油天然气   495篇
武器工业   152篇
无线电   1153篇
一般工业技术   2548篇
冶金工业   741篇
原子能技术   262篇
自动化技术   3594篇
  2024年   97篇
  2023年   398篇
  2022年   711篇
  2021年   735篇
  2020年   673篇
  2019年   566篇
  2018年   559篇
  2017年   644篇
  2016年   651篇
  2015年   627篇
  2014年   960篇
  2013年   1072篇
  2012年   1025篇
  2011年   1145篇
  2010年   784篇
  2009年   877篇
  2008年   821篇
  2007年   908篇
  2006年   745篇
  2005年   678篇
  2004年   568篇
  2003年   508篇
  2002年   444篇
  2001年   375篇
  2000年   302篇
  1999年   275篇
  1998年   231篇
  1997年   209篇
  1996年   163篇
  1995年   162篇
  1994年   120篇
  1993年   99篇
  1992年   82篇
  1991年   80篇
  1990年   78篇
  1989年   70篇
  1988年   61篇
  1987年   33篇
  1986年   19篇
  1985年   23篇
  1984年   20篇
  1983年   24篇
  1982年   15篇
  1980年   9篇
  1979年   8篇
  1966年   6篇
  1964年   6篇
  1959年   7篇
  1958年   5篇
  1955年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
目的 开展中国新一代载人飞船卫生区的空间优化研究,探索功能性空间优化设计方法,提高载人飞船空间利用效率,同时提升航天员的舒适性体验。方法 以中国空间站卫生区的功能和结构为依据,探讨中国新一代载人飞船卫生区功能组件的构成;依据航天员在微重力状态下使用卫生区的动作与姿态,建立卫生区空间布置的初步概念;根据卫生区的舱壁布局、微重力下航天员视野区域及最佳操作空间分析,开展相关功能组件建模,基于卫生区的人机交互节点,利用JACK软件进行仿真分析与评估,结合评估结果改进设计方案,并通过追踪航天员活动轨迹产生的包络体完成卫生区的空间优化。结论 通过对比中国新一代载人飞船卫生区优化前后设计方案的舒适性、可操作性和空间尺寸,验证了功能性空间优化设计方法的有效性和可靠性,为载人航天器舒适性与集成化设计提供了参考。  相似文献   
42.
目的 旨在有效解决稠油化学冷采过程中降黏剂窜流现象严重、油藏动用效率低的问题,支撑稠油绿色高效开发。方法 基于稠油冷采降黏剂高效降黏洗油与冻胶分散体调剖剂储层调控的协同效应,采用复配方式构建了稠油冷采用冻胶分散体调驱体系,测试其基本性能,并使用界面扩张流变仪以及流变仪,考查了体系的界面流变特性和剪切应力特性。结果 体系由质量分数为0.06%~0.12%的冻胶分散体和质量分数为0.05%~0.15%的降黏剂组成,为粒径均一的低黏流体,能够降低界面张力并乳化稠油,降黏率达到95%以上。体系中降黏剂在油水界面的吸附行为决定了体系的乳化降黏能力,降黏剂通过吸附在冻胶分散体的表面提高了体系的聚结稳定性,并考查了组分含量及油藏条件对以上过程的影响。结论 构建了一种兼具储层调控和高效降黏能力稠油冷采用冻胶分散体调驱体系,探明了体系中各组分间的相互作用机制,为稠油化学冷采提供了技术支持。  相似文献   
43.
在人们情绪压力不断增大的当今社会,艺术疗愈以其创造性特征和非语言媒介帮助疗愈对象改善心理或身体状态,旨在讨论艺术疗愈空间中的环境媒介与疗愈过程中的具身交互关系、设计实践与价值。借助CiteSpace可视化软件分析近十年来的重要文献,揭示艺术疗愈的研究现状;运用文献计量学方法,探索环境媒介在艺术疗愈空间的应用,定义环境媒介的具身性、主体间性、沉浸性特征及三者间的关联;以具身交互理论为线索,结合设计案例分析疗愈空间中环境媒体的具身性实践与作用方式,以期进一步探索结合新兴技术的环境媒介未来在我国的应用发展。艺术疗愈空间的环境媒介能具身地影响疗愈对象的交互行为与认知,提高疗愈的效率和质量。环境媒介与具身交互能增进疗愈过程中的不同主体间的体验共享,并辅助疗愈对象沉浸地参与或融入艺术疗愈;数字技术的发展不断地丰富环境媒介的形式,提高艺术疗愈的效果。  相似文献   
44.
王旭 《模具制造》2007,7(12):32-33
结合三峡电机铜管弯曲模具结构设计,对小半径铜管弯曲过程中可能出现的缺陷进行了探讨,提出了预防措施.  相似文献   
45.
Drug discovery, which aids to identify potential novel treatments, entails a broad range of fields of science, including chemistry, pharmacology, and biology. In the early stages of drug development, predicting drug–target affinity is crucial. The proposed model, the prediction of drug–target affinity using a convolution model with self-attention (CSatDTA), applies convolution-based self-attention mechanisms to the molecular drug and target sequences to predict drug–target affinity (DTA) effectively, unlike previous convolution methods, which exhibit significant limitations related to this aspect. The convolutional neural network (CNN) only works on a particular region of information, excluding comprehensive details. Self-attention, on the other hand, is a relatively recent technique for capturing long-range interactions that has been used primarily in sequence modeling tasks. The results of comparative experiments show that CSatDTA surpasses previous sequence-based or other approaches and has outstanding retention abilities.  相似文献   
46.
47.
Hfq is a pleiotropic regulator that mediates several aspects of bacterial RNA metabolism. The protein notably regulates translation efficiency and RNA decay in Gram-negative bacteria, usually via its interaction with small regulatory RNAs. Previously, we showed that the Hfq C-terminal region forms an amyloid-like structure and that these fibrils interact with membranes. The immediate consequence of this interaction is a disruption of the membrane, but the effect on Hfq structure was unknown. To investigate details of the mechanism of interaction, the present work uses different in vitro biophysical approaches. We show that the Hfq C-terminal region influences membrane integrity and, conversely, that the membrane specifically affects the amyloid assembly. The reported effect of this bacterial master regulator on membrane integrity is discussed in light of the possible consequence on small regulatory RNA-based regulation.  相似文献   
48.
Plants have various self-defense mechanisms against biotic attacks, involving both physical and chemical barriers. Physical barriers include spines, trichomes, and cuticle layers, whereas chemical barriers include secondary metabolites (SMs) and volatile organic compounds (VOCs). Complex interactions between plants and herbivores occur. Plant responses to insect herbivory begin with the perception of physical stimuli, chemical compounds (orally secreted by insects and herbivore-induced VOCs) during feeding. Plant cell membranes then generate ion fluxes that create differences in plasma membrane potential (Vm), which provokes the initiation of signal transduction, the activation of various hormones (e.g., jasmonic acid, salicylic acid, and ethylene), and the release of VOCs and SMs. This review of recent studies of plant–herbivore–infection interactions focuses on early and late plant responses, including physical barriers, signal transduction, SM production as well as epigenetic regulation, and phytohormone responses.  相似文献   
49.
Patients with liver diseases not only experience the adverse effects of liver-metabolized drugs, but also the unexpected adverse effects of renally excreted drugs. Bile acids alter the expression of renal drug transporters, however, the direct effects of bile acids on drug transport remain unknown. Renal drug transporter organic anion-transporting polypeptide 4C1 (OATP4C1) was reported to be inhibited by chenodeoxycholic acid. Therefore, we predicted that the inhibition of OATP4C1-mediated transport by bile acids might be a potential mechanism for the altered pharmacokinetics of renally excreted drugs. We screened 45 types of bile acids and calculated the IC50, Ki values, and bile acid–drug interaction (BDI) indices of bile acids whose inhibitory effect on OATP4C1 was >50%. From the screening results, lithocholic acid (LCA), glycine-conjugated lithocholic acid (GLCA), and taurine-conjugated lithocholic acid (TLCA) were newly identified as inhibitors of OATP4C1. Since the BDI index of LCA was 0.278, LCA is likely to inhibit OATP4C1-mediated transport in clinical settings. Our findings suggest that dose adjustment of renally excreted drugs may be required in patients with renal failure as well as in patients with hepatic failure. We believe that our findings provide essential information for drug development and safe drug treatment in clinics.  相似文献   
50.
(1) Background: Depending on the type of hydrophilic polymer used, different types of hydrogels may be chemically stable or may degrade and eventually disintegrate, or dissolve upon exposure to sunlight. Many over-the-counter medications are now stored with a limited control of temperature, humidity and lighting. Therefore, in this study, the photostability of a gel made of cross-linked polyacrylic acid (PA), methylcellulose (MC) and aristoflex (AV) was assessed, and the interaction between the polymers used and ascorbic acid and its ethylated derivative was investigated. (2) Methods: The samples were continuously irradiated at constant temperature for six hours. The stability of the substance incorporated into the gels was assessed using a UV-Vis spectrophotometer. FTIR-ATR infrared spectroscopy was used to measure changes during the exposure. (3) Results: Ascorbic acid completely decomposed between the first and second hours of illumination in all samples. The exception is the preparation based on polyacrylic acid with glycerol, in which the decomposition of ascorbic acid slowed down significantly. After six hours of irradiation, the ethylated ascorbic acid derivative decomposed in about 5% for the polyacrylic acid-based gels and aristoflex, and in the methylcellulose gel it decomposed to about 2%. In the case of ascorbic acid, the most stable formulation was a gel based on polyacrylic acid and polyacrylic acid with glycerol, and in the case of the ethyl derivative, a gel based on methylcellulose. (4) Conclusions: The experiment showed significant differences in the decomposition rate of both compounds, resulting from their photostability and the polymer used in the hydrogel.  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