全文获取类型
收费全文 | 12292篇 |
免费 | 1042篇 |
国内免费 | 554篇 |
专业分类
电工技术 | 929篇 |
技术理论 | 2篇 |
综合类 | 790篇 |
化学工业 | 2120篇 |
金属工艺 | 708篇 |
机械仪表 | 739篇 |
建筑科学 | 776篇 |
矿业工程 | 292篇 |
能源动力 | 320篇 |
轻工业 | 809篇 |
水利工程 | 239篇 |
石油天然气 | 726篇 |
武器工业 | 102篇 |
无线电 | 1357篇 |
一般工业技术 | 1557篇 |
冶金工业 | 656篇 |
原子能技术 | 183篇 |
自动化技术 | 1583篇 |
出版年
2024年 | 49篇 |
2023年 | 225篇 |
2022年 | 351篇 |
2021年 | 528篇 |
2020年 | 405篇 |
2019年 | 338篇 |
2018年 | 386篇 |
2017年 | 425篇 |
2016年 | 374篇 |
2015年 | 495篇 |
2014年 | 645篇 |
2013年 | 684篇 |
2012年 | 729篇 |
2011年 | 880篇 |
2010年 | 680篇 |
2009年 | 677篇 |
2008年 | 732篇 |
2007年 | 723篇 |
2006年 | 670篇 |
2005年 | 589篇 |
2004年 | 412篇 |
2003年 | 398篇 |
2002年 | 455篇 |
2001年 | 367篇 |
2000年 | 266篇 |
1999年 | 228篇 |
1998年 | 200篇 |
1997年 | 180篇 |
1996年 | 169篇 |
1995年 | 145篇 |
1994年 | 134篇 |
1993年 | 73篇 |
1992年 | 72篇 |
1991年 | 39篇 |
1990年 | 26篇 |
1989年 | 34篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1967年 | 2篇 |
1961年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
鼎湖山自然保护区胡椒属植物生物学特性研究 总被引:3,自引:0,他引:3
研究了鼎湖山自然保护区分布的8种胡椒属植物的外部形态,根尖和茎法细胞的染色体数目,花粉外部形态和繁殖保护方法,并根据研究结果对该保护区内关于本属植物存在的问题和应对策略作了初步探讨。 相似文献
53.
Georgina To'a Salazar Ziyi Huang Ningyan Zhang Xue-Guang Zhang Zhiqiang An 《工程(英文)》2021,7(11):1541-1551
In analyses of protein families that may serve as drug targets, membrane-associated G-protein-coupled receptors (GPCRs) dominate, followed by ion channels, transporters, and—to a lesser extent—membrane-bound enzymes. However, various challenges put such membrane proteins among key groups of underutilized opportunities for the application of therapeutic antibodies. Antibodies hold the promise of exquisite specificity, as they are able to target even specific conformations of a particular membrane protein, as well as adaptability through engineering into various antibody formats. However, the ease of raising and isolating specific, effective antibodies targeting membrane proteins depends on many factors. In particular, the generation of specific antibodies is easier when targeting larger, simpler, extracellular domains with greater uniqueness of amino acid sequence. The rareness of such ideal conditions is illustrated by the limited number of approved biologics for targeting GPCRs and other complex membrane proteins. Challenges in developing antibodies to complex membrane proteins such as GPCRs, ion channels, transporters, and membrane-bound enzymes can be addressed by the design of the antigen, antibody-generation strategies, lead optimization technologies, and antibody modalities. A better understanding of the membrane proteins being targeted would facilitate mechanism-based drug discovery. This review describes the advantages and challenges of targeting complex membrane proteins with antibodies and discusses the preparation of membrane protein antigens and antibody generation, illustrated by select examples of success. 相似文献
54.
着重介绍金属切削液的分类、功能及其在轴承加工中的选用。在轴承加工中,一般有车削、铣削、钻削、铰削和磨削等多种加工工艺,其中磨削加工是一道非常重要的精密加工工序,如内圆磨削、外圆磨削、平面磨削和沟槽磨削等。轴承加工中使用的水基切削液不仅要具有冷却作用,还要有润滑、清洗和防锈的功能。重点介绍金属切削液的主要功能及其在轴承加工中的应用。 相似文献
55.
W-based versus latent variables spatial autoregressive models: evidence from Monte Carlo simulations
In this paper, we compare by means of Monte Carlo simulations two approaches to take spatial autocorrelation into account: the classical spatial autoregressive model and the structural equations model with latent variables. The former accounts for spatial dependence and spillover effects in georeferenced data by means of a spatial weights matrix W. The latter represents spatial dependence and spillover effects by means of a latent variable in the structural (regression) model while the observed spatially lagged variables are related to the latent spatial dependence variable in the measurement model. The simulation results based on Anselin’s Columbus, Ohio, crime data set show that the misspecified latent variables approach slightly trails the correctly specified classical approach in terms of bias and root mean squared error of the coefficient estimators. 相似文献
56.
The effect of compression on the crystallization behavior and corrosion resistance of Al(86)Ni9La5 amorphous ribbons was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning elec-tron microscopy (SEM) and electrochemistry test. The XRD and TEM results reveal that the compressed Al(86)Ni9La5 ribbons spun with the circumferential speed (R) of 29.3 m/s are in fully amorphous state; however, the compressed ribbons spun with R=14.7 m/s have crystalline phases embedded in the amorphous matrix. The SEM images indicate that after compression, the toughness of the ribbons increases. Electrochemical results show that the compression decreases the stability of the passive film of the Al(86)Ni9La5 amorphous ribbons, because of the compression-introduced free volume, shear bands and crystalline phases; meanwhile, with R=14.7 m/s, the compression-induced crystalline phases in the Al(86)Ni9La5 ribbons increase the corrosion potential. 相似文献
57.
为满足现代生产生活中对颜色快速测量的需求,设计了一种基于RGB三基色原理,采用光纤波导及融合技术、应用白平衡调节手段的数字式比色仪。仪器由白光LED光源、Y型混合石英光纤束光波导探头、微透镜发射耦合及透镜准直接收部件、以颜色传感器和MSP430单片机为核心的信号采集及处理部件等组成,采用C语言编程进行数据采集、存储、白平衡调整、颜色识别及显示。经与比色卡对比测试,其测量准确度和速度相对于当前广泛应用的比色卡均有很大提高。 相似文献
58.
Liquan Shen Zhi Liu Tao Yan Zhaoyang Zhang Ping An 《Signal Processing: Image Communication》2010,25(2):88-93
In the joint multiview video model (JMVM) proposed by JVT, the variable block-size motion estimation (ME) and disparity estimation (DE) have been employed to determine the best coding mode for each macroblock (MB). These give a high coding efficiency for multiview video coding (MVC), however, they cause a very high computational complexity in encoding system. This paper proposes to reduce the complexities of the ME and DE processes with an early SKIP mode decision algorithm based on the analysis of prediction mode distribution regarding the corresponding MBs in the neighbor view. In this method, the mode decision procedures of most of MBs can be early terminated, and thus much of computation for ME and DE can be greatly reduced. Simulation results demonstrate that our algorithm can achieve computational saving of 46–57% (depending on the tested sequences) with no significant loss of rate-distortion performance. 相似文献
59.
数据库在专家系统中的应用 总被引:2,自引:0,他引:2
本文介绍一个将多种数据信息,控制信息引入到数据库中进行管理控制的专家系统,整个系统的运行靠数据库来驱动,系统调整起来非常方便,运行效率得到了提高,结构得到了优化。 相似文献
60.