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   1826篇
  免费   291篇
  国内免费   175篇
电工技术   416篇
技术理论   1篇
综合类   204篇
化学工业   176篇
金属工艺   16篇
机械仪表   57篇
建筑科学   46篇
矿业工程   43篇
能源动力   157篇
轻工业   46篇
水利工程   70篇
石油天然气   18篇
武器工业   5篇
无线电   114篇
一般工业技术   155篇
冶金工业   21篇
自动化技术   747篇
  2024年   12篇
  2023年   76篇
  2022年   82篇
  2021年   98篇
  2020年   81篇
  2019年   85篇
  2018年   62篇
  2017年   74篇
  2016年   77篇
  2015年   71篇
  2014年   109篇
  2013年   124篇
  2012年   134篇
  2011年   139篇
  2010年   116篇
  2009年   124篇
  2008年   120篇
  2007年   103篇
  2006年   100篇
  2005年   79篇
  2004年   74篇
  2003年   64篇
  2002年   46篇
  2001年   52篇
  2000年   40篇
  1999年   28篇
  1998年   14篇
  1997年   10篇
  1996年   7篇
  1995年   12篇
  1994年   11篇
  1993年   9篇
  1992年   7篇
  1991年   10篇
  1990年   4篇
  1989年   4篇
  1988年   2篇
  1985年   2篇
  1984年   5篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1976年   4篇
  1975年   3篇
  1974年   2篇
  1973年   1篇
  1961年   1篇
排序方式: 共有2292条查询结果,搜索用时 15 毫秒
1.
d -Amino acid containing peptides are promising as drug lead compounds because of their expected higher stability in vivo. A heterochiral random peptide library called the one-bead–2n-peptide (OB2nP) library, which can display 2n peptide diastereomers per bead, has been developed. Through screening of the OB2nP library and subsequent binding assay among the peptide diastereomers synthesized in parallel by means of the SPOTs method, new heterochiral mimotopes for the anti-β-endorphin monoclonal antibody have been obtained. One mimotope was a new ligand for the μ-opioid receptor. The screening strategy enabled d -amino acid containing drug leads to be obtained efficiently by expanding searchable chemical space without increasing the experimental scale.  相似文献   
2.
针对跨数据中心的资源调度问题,提出了一种基于组合双向拍卖(PCDA)的资源调度方案。首先,将云资源拍卖分为三个部分:云用户代理报价、云资源提供商要价、拍卖代理组织拍卖;其次,在定义用户的优先级及任务紧迫度的基础上,在拍卖过程中估算每一个工作发生的服务等级协议(SLA)违规并以此计算云提供商的收益,同时每轮竞拍允许成交多项交易;最终达到根据用户等级合理分配云资源调度的效果。仿真实验结果表明该算法保证了竞拍成功率,与传统一次拍卖成交一项的组合双向拍卖方案相比,PCDA在竞拍时间段产生的能耗降低了35.00%,拍卖云提供商的利润提高了约38.84%。  相似文献   
3.
Concerns over dramatic increasing electricity demand, exacerbating power shortage and changing climatic condition are emerging associated with municipal electric power systems (EPS). In this study, a risk-explicit mixed-integer full-infinite programming (RMFP) approach is developed for planning carbon emission trading (CET) in EPS. RMFP-CET has advantages in risk reflection and policy analysis, particularly when the input parameters are provided as crisp and functional intervals as well as probabilistic distributions. The developed method is applied to a real case study of CET planning of EPS in Beijing. Various electricity policies are incorporated within the modeling formulation for enhancing the RMFP-CET's capability. The results indicate that reasonable solutions have been generated, which are useful for making decisions of electricity production and supply as well as gaining insight into the tradeoffs among electricity supply risk, system cost, and CO2 mitigation strategy.  相似文献   
4.
DNA-templated self-assembly is an emerging strategy for generating functional supramolecular systems, which requires the identification of potent multi-point binding ligands. In this line, we recently showed that bis-functionalized guanidinium compounds can interact with ssDNA and generate a supramolecular complex through the recognition of the phosphodiester backbone of DNA. In order to probe the importance of secondary interactions and to identify side groups that stabilize these DNA-templated self-assemblies, we report herein the implementation of a dynamic combinatorial approach. We used an in situ fragment assembly process based on reductive amination and tested various side groups, including amino acids. The results reveal that aromatic and cationic side groups participate in secondary supramolecular interactions that stabilize the complexes formed with ssDNA.  相似文献   
5.
In order to make full use of renewable energy and improve the utilization of wind power, a new joint optimization scheme of the wind-hydrogen system coupled with transmission project is proposed in this paper, in which wind power is reasonably allocated for grid integration and for hydrogen production. Aiming at maximize the annul wind-hydrogen system benefit, the optimal sizes of wind power transmission project and hydrogen system are obtained under different hydrogen production modes, hydrogen trading modes and hydrogen demand levels. In addition, the penalty cost of wind curtailment and hydrogen supply shortage and the system environmental benefits are taken into account. Results show: during the long-term of insufficient of wind power, it is better to produce hydrogen using wind power and grid-assisted power to avoid hydrogen supply shortage; considering the future increase of hydrogen demand, the optimal supply number of hydrogen refueling stations in the wind-hydrogen system is two. Also, the low utilization of fuel cells means that the benefit from regeneration cannot offset the high cost, which leads to the abnegation of fuel cells in the wind-hydrogen system.  相似文献   
6.
遗传算法在反演概率积分法预计参数时从参数取值范围内的串集开始搜索,并使用弹性策略来维持群体的多样性,使得算法可以跨过局部收敛的障碍,向全局最优解方向进化;但这种概率化的寻优算法存在局部探索能力差、结果不稳定的缺陷,只能获得问题的近似最优解。模矢法是一种降梯度算法,算法局部探索能力强、收敛快;但这种算法对初值选取敏感,初值选择不当易陷入局部极值。本文提出并实现了一种模矢法与遗传算法结合的组合算法:先使用遗传算法求得参数的全局近似最优解,然后将近似最优解作为探索初值,使用模矢法获得参数的稳定、精确最优解。研究结果表明:组合算法反演概率积分法预计参数的精确度高、收敛快、稳定性好,综合性能较遗传算法和模矢法有明显优势。  相似文献   
7.
本研究探讨了蛋白酶、α-淀粉酶和葡萄糖苷酶组合酶解作用对鹰嘴豆发酵乳品质改善的影响。结果表明:经过蛋白酶、α-淀粉酶与葡糖苷酶组合酶解处理的鹰嘴豆浆固形物含量和总糖含量均显著增加,分别增加了23.76%、8.22%;经过三酶组合处理后的样品pH降低、持水力显著提高,粘度增大,稳定性增强;随着发酵时间的延长,发酵乳在0~24 h,各组持水力均随发酵时间呈增加而增大,C4(三酶组合)组增大了17.25%;24 h后,除C0(空白)组下降,其余各组持水力增幅趋缓;各组还原糖含量均随发酵时间呈下降趋势,C4(三酶组合)组在12~48 h还原糖含量回升了3.22%;感官品评显示酶处理较显著地影响了鹰嘴豆发酵乳的气味、外观、滋味和质构。与C0组相比,经过C4(三酶组合)组处理后感官指标提高,总体可接受性评分从6.13提高到8.53,提高了39.15%,表明组合酶解作用有利于鹰嘴豆发酵乳品质的改善。  相似文献   
8.
Abstract

We have developed combinatorial generation function methods that combine M?bius inversion and character cycle indices for the enumeration of stereo, position and chiral isomers of icosahedral giant fullerenes C180 and C240. Techniques are also developed for the machine perception of symmetries of especially giant fullerenes. The techniques yield, symmetries, position, stereo and chiral isomers of giant fullerenes which we illustrate with applications to icosahedral C180(Ih), and C240(Ih). We have obtained combinatorial tables for the isomers of C180Xk and C240Xk. Our results point to errors in previous computations on C240 permutations. We have also outlined applications to NMR and ESR spectroscopy.  相似文献   
9.
In recent years, the interests of disassembly line have increased owing to economic reasons and the increase of environmental awareness. Effective line can provide many advantages in terms of economic aspect and it facilitates competition the companies with others. This study contributes to the relevant literature by a branch, bound and remember algorithm for disassembly line balancing problem with AND/OR precedence. The proposed exact solution method employs the memory-based dominance rule to eliminate the reduplicated sub-problems by storing all the searched sub-problems and to utilise cyclic best-first search strategy to obtain high-quality complete solutions fast. In this paper, minimising the number of stations is taken as the performance measure. The proposed methodology is tested on a set of 260 instances and compared with the mathematical model using CPLEX solver and five well-known metaheuristics. Computational results show that the proposed method is capable of obtaining the optimal solutions for all the tested instances with less than 0.1?seconds on average. Additionally, comparative study demonstrates that the proposed method is the state-of-the-art algorithm and outperforms the CPLEX solver and metaheuristics in terms of both solution quality and search speed aspects.  相似文献   
10.
断裂带老顶的判别准则及在浅埋煤层中的应用   总被引:16,自引:2,他引:16  
侯忠杰 《煤炭学报》2003,28(1):8-12
从20世纪50年代的铰接岩块假说到砌体梁理论的建立,都把断裂带老顶结构作为主要研究对象,在讨论有关断裂带老顶结构假说和理论的基础上,根据老顶初次断裂拱式平衡和周期断裂砌体梁平衡条件,考虑到岩块间铰点挤压接触面的实际高度,推导出了断裂带老顶判别的理论公式,即老顶分层厚度大于其下自由空间高度1.5倍时该分层进入断裂带,通过与实际观测值及所建立的经验公式比较,证明理论公式的计算值与实际一致,从而使长期悬而未解的断裂带老顶层位问题在理论上得以解决,同时也进一步说明了浅埋煤层组合关键层覆岩全厚切落的必然性。  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