全文获取类型
收费全文 | 2660篇 |
免费 | 249篇 |
国内免费 | 111篇 |
专业分类
电工技术 | 164篇 |
综合类 | 150篇 |
化学工业 | 439篇 |
金属工艺 | 139篇 |
机械仪表 | 156篇 |
建筑科学 | 267篇 |
矿业工程 | 82篇 |
能源动力 | 67篇 |
轻工业 | 201篇 |
水利工程 | 34篇 |
石油天然气 | 154篇 |
武器工业 | 12篇 |
无线电 | 285篇 |
一般工业技术 | 357篇 |
冶金工业 | 159篇 |
原子能技术 | 24篇 |
自动化技术 | 330篇 |
出版年
2024年 | 15篇 |
2023年 | 51篇 |
2022年 | 70篇 |
2021年 | 109篇 |
2020年 | 69篇 |
2019年 | 92篇 |
2018年 | 86篇 |
2017年 | 115篇 |
2016年 | 80篇 |
2015年 | 94篇 |
2014年 | 134篇 |
2013年 | 176篇 |
2012年 | 176篇 |
2011年 | 203篇 |
2010年 | 144篇 |
2009年 | 143篇 |
2008年 | 108篇 |
2007年 | 118篇 |
2006年 | 138篇 |
2005年 | 126篇 |
2004年 | 72篇 |
2003年 | 80篇 |
2002年 | 106篇 |
2001年 | 82篇 |
2000年 | 71篇 |
1999年 | 61篇 |
1998年 | 59篇 |
1997年 | 52篇 |
1996年 | 33篇 |
1995年 | 32篇 |
1994年 | 27篇 |
1993年 | 29篇 |
1992年 | 21篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1951年 | 1篇 |
1943年 | 2篇 |
1935年 | 1篇 |
1934年 | 1篇 |
排序方式: 共有3020条查询结果,搜索用时 0 毫秒
1.
2.
火焰喷涂是激光熔覆前合金粉末的预置方法之一。本文在实验的基础上,探讨了工艺过程,并讨论了影响质量的因素。 相似文献
3.
A Nu?ez C De la Roza ML Rodrigo-Angulo W Bu?o F Reinoso-Suárez 《Canadian Metallurgical Quarterly》1997,754(1-2):1-11
This study analyses the relationship between the use of rotating instruments, the production of a smear layer and the presence of alterations to enamel microstructures. The rotating instruments used were carbide (8-12 blade) and diamond tipped (30-15 m) cutters. Cavities were made in extracted teeth. Subsequently, half the sample was analysed using the rugosimeter before and after the application of ortophosphoric acid at 35% for 15 and the other half suing a Scansion Electronic microscope (SEM). The results obtained showed on the one hand that carbide cutters leave a smoother surfacer than diamond tipped cutters, and on the other that the smear layer is eliminated better by carbide cutters compared to diamond tipped cutters. Moreover, there are no major traumatic-type alterations at the level of the enamel affecting the microstructure after the use of carbide cutters. 相似文献
4.
钻速模式动态辨识方法研究 总被引:1,自引:0,他引:1
目的:钻进过程是一个复杂的工艺过程,影响钻速的因素错综复杂。为钻井参数优化和实时控制,提出钻速动态模型。方法:对影响钻速的因素进行分析,用系统辨识方法建立钻速模式。结果:利用该方法建立了华北油田岔河集地区的钻速模型,取得满意结果。结论:此动态钻速模式能更准确、科学地描述钻进过程,并在钻井参数最优化、钻井过程的闭环控制等方面具有广阔的应用前景。 相似文献
5.
Ma Weidong Liu Wen Wenmin Wang Luo Yong Bu Qinlian Xiouli Zhao Jiang Shan Li Wei 《Photonics Technology Letters, IEEE》2007,19(15):1115-1117
An athermal 40-channel dense wavelength-division-multiplexing multi/demultiplexer using a novel combination technology is proposed. It consists of one 1times4 100- to 400-GHz spacing interleaver filter and four sub-arrayed-waveguide gratings (AWGs). The temperature-dependent wavelength shift of the combined device is successfully suppressed to 0.058 nm in the -20degC to 70degC temperature range. Moreover, the combined device's adjacent crosstalk (typically -35 dB) is much better than conventional AWGs (typically -25 dB). 相似文献
6.
RLL码的计算机辅助设计 总被引:1,自引:1,他引:0
本文着重讨论计算机辅助设计RLL码的具体实现问题.该过程首先根据RLL码两个参数d,k确定一个编码率p/q,然后构造出RLL码的高阶状态转换-输出符号矩阵并求相应的近似特征向量.最后通过状态分裂和状态归并过程,即可得到一个满足d,k约束的编码输出表.其中状态转换-输出符号矩阵为实现计算机辅助设计RLL码提供了有效的数据结构,而且要优化RLL码编码器,就必须有选择地进行状态分裂. 相似文献
8.
SynthesisandSpectralPropertiesofMixedLigandComplexesofLanthanidePerchloratewithBis(phenylsulfinyl)ethaneandOrganicLewisBase... 相似文献
9.
Han-Shue Tan Fanping Bu Bougler B. 《Intelligent Transportation Systems, IEEE Transactions on》2007,8(3):538-548
This paper describes the development process and the initial field test results of an automated snowblower, focusing on one of the more difficult snow removal operations: blowing snow off the freeway alongside a guardrail without the snowblower touching the guardrail. The development process includes transforming this highway winter maintenance operation into a control problem, modeling a snowblower, designing control algorithms, devising a human-machine interface, and equipping a 20-ton snowblower with sensors and an actuator. Specific challenges include modeling the low-speed tire-induced oscillation, designing high-gain automatic control on front wheels while keeping rear steering under driver control, and implementing such a system under practical limitations. A new dynamic deflection tire model is incorporated into a bicycle model to account for the additional lateral dynamics. A low-order controller was first generated based on the understanding of the specific control problem and, then, refined and tuned iteratively using linear-matrix-inequality optimization. The initial winter field tests were successfully conducted with embedded magnetic markers along the guardrails installed on the shoulders of Interstate-80 in the Sierra Mountain region close to Donner Summit, CA, during the winter of 2005. 相似文献
10.
Interfacial polycondensation of diphenolic acid (DPA) and isophthaloyl chloride (IPC) in various solvent/water systems was investigated with tetrabutyl ammonium chloride as a phase transfer catalyst. It was found that a large mass of capsules were formed at the beginning of the reaction for all solvents examined but the capsule morphology and reaction results depended on the solvents. It is believed that the capsule shells make up of the reaction zone and a mechanism of the interfacial polycondensation is proposed accordingly. The effect of the solvents on the reaction was interpreted from the interaction between the polymer and the solvent according to the mechanism. The reaction conditions were optimized, and poly(DPA-IPC) with high intrinsic viscosity was prepared in high yield under the optimal condition. It is an amorphous polymer with glass transition temperature of about 160°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献