全文获取类型
收费全文 | 71885篇 |
免费 | 5513篇 |
国内免费 | 2899篇 |
专业分类
电工技术 | 3529篇 |
技术理论 | 10篇 |
综合类 | 4187篇 |
化学工业 | 12811篇 |
金属工艺 | 3979篇 |
机械仪表 | 4417篇 |
建筑科学 | 6068篇 |
矿业工程 | 2074篇 |
能源动力 | 2119篇 |
轻工业 | 4310篇 |
水利工程 | 1164篇 |
石油天然气 | 4478篇 |
武器工业 | 552篇 |
无线电 | 8341篇 |
一般工业技术 | 9140篇 |
冶金工业 | 3697篇 |
原子能技术 | 839篇 |
自动化技术 | 8582篇 |
出版年
2024年 | 264篇 |
2023年 | 1152篇 |
2022年 | 1917篇 |
2021年 | 2626篇 |
2020年 | 2054篇 |
2019年 | 1823篇 |
2018年 | 1976篇 |
2017年 | 2290篇 |
2016年 | 2064篇 |
2015年 | 2709篇 |
2014年 | 3350篇 |
2013年 | 4023篇 |
2012年 | 4433篇 |
2011年 | 4654篇 |
2010年 | 4055篇 |
2009年 | 3836篇 |
2008年 | 3757篇 |
2007年 | 3723篇 |
2006年 | 3966篇 |
2005年 | 3427篇 |
2004年 | 2354篇 |
2003年 | 2060篇 |
2002年 | 1987篇 |
2001年 | 1798篇 |
2000年 | 1812篇 |
1999年 | 2102篇 |
1998年 | 1866篇 |
1997年 | 1521篇 |
1996年 | 1451篇 |
1995年 | 1110篇 |
1994年 | 1061篇 |
1993年 | 727篇 |
1992年 | 558篇 |
1991年 | 446篇 |
1990年 | 337篇 |
1989年 | 265篇 |
1988年 | 243篇 |
1987年 | 151篇 |
1986年 | 107篇 |
1985年 | 80篇 |
1984年 | 39篇 |
1983年 | 36篇 |
1982年 | 41篇 |
1981年 | 22篇 |
1980年 | 14篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
11.
东营市CNG公交汽车改装及加气站经济性研究 总被引:1,自引:0,他引:1
对东营市公交汽车改装方案和建设相应的加气站进行了研究,结果表明,以2006年当地90号汽油、0号柴油和CNG价格计算,改装为柴油CNG双燃料公交车比柴油车,每天每车可节省燃料费92.24元,成本回收期为3.6个月;建一座年设计加气量为547.5万m^3、可供200-250辆汽车加气的常规开放式加气站,投资回收期为8年零8个月。改装汽车和建设加气站可利用当地丰富的天然气资源,节约石油,保护环境。 相似文献
12.
A tennis novice watching a match for the first time might be surprised that the crowd erupts with cheers when a player wins one point, then barely applauds when he wins the next. The crowd is not necessarily fickle; some points are genuinely more important than others because a tennis match is hierarchically structured. One match consists of several sets. One set consists of several games. One game consists of several points. The match-winning point is the most important one. How can we make that importance visible? Our goal is to let a fan, a player, or a coach examine tennis data visually, extract the interesting parts, and jump from one item to another quickly and easily. The visualization tool should help parse the elements of a match. We developed an interactive system called TennisViewer to visualize the dynamic, tree-structured data representing a tennis match. It provides an interface for users to quickly explore tennis match information. The visualization tool reveals the overall structure of the match as well as the fine details in a single screen. It uses a 2D display of translucent layers, a design that contains elements of Tree-Maps and of the Visual Scheduler system, which was designed to help faculty and students identify mutually available (transparent) time slots when arranging group meetings. TennisViewer provides MagicLens filters to explore specialized views of the information and a time-varying display to animate all or part of a match 相似文献
13.
This work pertains to output voltage stability of soft adjacent layer biased magnetoresistive heads with abutted permanent magnetic films for domain stabilization. A micromagnetic model has been developed to study the effect of the permanent magnet film microstructure and the micromagnetic properties of the abutted junction interface on head stability. The impact on head stability is analyzed with respect to interfacial ferromagnetic coupling across the junction interface and intergranular exchange coupling in the permanent magnet films among other film properties 相似文献
14.
15.
16.
对掺氟化镨玻璃光纤放大器的小信号增益,用广义的高斯近似公式可获得精确的分析表达。文中研究了限制光纤芯层中央部分的镨掺杂对光纤放大器特性的影响,结果发现限制镨掺杂分布能改进光纤放大器的工作效率,且截止波长比芯层全部均匀掺镨的光纤更长。 相似文献
17.
���þ��ܰ�ȫ�Բ������������� 总被引:1,自引:1,他引:0
本文通过对在用钻机井架的现场实际测试,建立数据库、测评模型,对实测的数据用计算机技术进行分析,提出了初始弯曲应力;数据正态分布检验——x~2检验;建立回归方程;在给定置信度下测评当前承载能力的技术概念。解决了在用钻机A型井架的安全性评估问题,是一种较为合理、可靠、科学的测评技术和方法。 相似文献
18.
Hillmer H. Grabmaier A. Zhu H.-L. Hansmann S. Burkhard A. 《Lightwave Technology, Journal of》1995,13(9):1905-1912
We have implemented and studied a new type of tunable multiple-section semiconductor distributed feedback (DFB) laser using tailored chirped DFB gratings. Arbitrarily and continuously chirped DFB gratings are defined by bent waveguides on homogeneous grating fields with ultrahigh spatial precision. The mathematical bending functions are optimized in this case to provide enlarged wavelength tuning ranges. We present the results of model calculations, the technological device realization and experimental results of the DFB laser characterization e.g. a tuning range of 5.5 nm without wavelength gaps and high side mode suppression ratio 相似文献
19.
20.
Anionic copolymerizations of styrene (M1) with excess 1-(4-dimethyl-aminophenyl)-1-phenylethylene (M2) were conducted in benzene at 25°C for 24h, using sec-butyllithium as initiator. Narrow molecular weight distribution copolymers with M?;n = 16.1 × 103 g/mol (M?w/M?n = 1.04) and 38.2 × 103g/mol (M?w/M?n = 1.05), and 24 and 38 moles of M2 per macromolecule, respectively, were characterized by size exclusion chromatography, 1H NMR spectroscopy and DSC. The monomer reactivity ratio, r1 = 5.6, was obtained from the copolymer composition at complete consumption of M1, assuming that the rate constant k22 =0,i.e. r2 =0. The polymers exhibited Tg values of 128 and 119°C, respectively, which correspond to an estimated Tg = 217°C for the hypothetical homopolymer of M2. 相似文献