全文获取类型
收费全文 | 43733篇 |
免费 | 4065篇 |
国内免费 | 1993篇 |
专业分类
电工技术 | 2608篇 |
技术理论 | 4篇 |
综合类 | 2858篇 |
化学工业 | 7182篇 |
金属工艺 | 2497篇 |
机械仪表 | 2702篇 |
建筑科学 | 3652篇 |
矿业工程 | 1247篇 |
能源动力 | 1245篇 |
轻工业 | 3089篇 |
水利工程 | 779篇 |
石油天然气 | 2132篇 |
武器工业 | 375篇 |
无线电 | 5038篇 |
一般工业技术 | 5415篇 |
冶金工业 | 2106篇 |
原子能技术 | 531篇 |
自动化技术 | 6331篇 |
出版年
2024年 | 280篇 |
2023年 | 866篇 |
2022年 | 1515篇 |
2021年 | 2098篇 |
2020年 | 1624篇 |
2019年 | 1268篇 |
2018年 | 1314篇 |
2017年 | 1545篇 |
2016年 | 1399篇 |
2015年 | 1841篇 |
2014年 | 2179篇 |
2013年 | 2539篇 |
2012年 | 2671篇 |
2011年 | 2838篇 |
2010年 | 2478篇 |
2009年 | 2317篇 |
2008年 | 2328篇 |
2007年 | 2153篇 |
2006年 | 2107篇 |
2005年 | 2021篇 |
2004年 | 1420篇 |
2003年 | 1165篇 |
2002年 | 1106篇 |
2001年 | 942篇 |
2000年 | 959篇 |
1999年 | 1048篇 |
1998年 | 939篇 |
1997年 | 792篇 |
1996年 | 803篇 |
1995年 | 652篇 |
1994年 | 550篇 |
1993年 | 443篇 |
1992年 | 326篇 |
1991年 | 261篇 |
1990年 | 210篇 |
1989年 | 179篇 |
1988年 | 146篇 |
1987年 | 100篇 |
1986年 | 78篇 |
1985年 | 47篇 |
1984年 | 48篇 |
1983年 | 32篇 |
1982年 | 30篇 |
1981年 | 20篇 |
1980年 | 30篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 15篇 |
1976年 | 8篇 |
1971年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
13.
氩等离子体辐照反相乳液接枝改性涤纶织物的研究 总被引:1,自引:0,他引:1
首次提出了在等离子体辐照后再用反相乳液接枝改性涤纶织物的新方法,探讨了接枝颗粒特征以及织物各项物理力学性能.接枝织物的结构及性能的测试结果表明:接枝物的尺寸远小于纤维的直径,在提高织物吸湿性的同时,对织物透气性能和强力等无明显影响;实验也证实了乳液中未接枝单体可以再次聚合. 相似文献
14.
Hui Chen D.T.K. Tong 《Photonics Technology Letters, IEEE》2005,17(4):801-803
Symmetric interference in two-dimensional multimode silicon waveguides is experimentally investigated. For a 100/spl times/100 /spl mu/m/sup 2/ cross section, 2700-/spl mu/m-long waveguide fabricated on silicon-on-insulator substrate, an 8/spl times/8 matrix of replicated images with high contrast ratio is demonstrated for 1530-1570 nm wavelength range. Symmetric interference results in reduced device length, and the actual device length is consistent with the theoretical expectation. The device also exhibits stable imaging in terms of good loss uniformity, and low wavelength and polarization dependencies among the replicated images. 相似文献
15.
A high-power and high-repetition-rate passively Q -switched ytterbium-doped single-mode double-clad fiber laser was built using a Cr4+:YAG saturable absorber (SA). Two different SAs with initial transmissions of Tomicron = 30% and Tomicron = 50% were studied. At the maximum coupled pump power of 9.8 W, an output power of 4.7 W, pulse duration of 143 ns, pulse repetition rate of 253 KHz, pulse energy of 18.5 muJ, and slope efficiency of 49% were obtained with the Tomicron = 30% SA. 相似文献
16.
Wei Li Zhang Wei Pan Bin Luo Xi Hua Zou Meng Yao Wang 《Photonics Technology Letters, IEEE》2008,20(9):712-714
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications. 相似文献
17.
In this paper we verified the submodeling technique applied in the thermomechanical reliability assessment of a flip-chip BGA under accelerated thermal cycling test conditions. Since the steady-state creep model was implemented for the solder bump to better represent its realistic mechanical behavior, submodeling procedures developed specifically for path-dependent thermomechanical problems were considered. A detailed global model for the flip-chip BGA was built up to verify submodeling solutions. This model also served as a benchmark to examine solution discrepancies caused by different simplifications of the global model. 相似文献
18.
综述了近年来超分子主体化合物在分析化学领域的应用研究与进展。分别以冠醚、环糊精、杯芳烃、卟啉4类超分子为主体功能化合物的研究进行了详细的评述,并对这几类主体化合物在分析化学中的应用研究进行了展望。 相似文献
19.
煤气吹扫时惰性气体抑爆用量的优选 总被引:1,自引:0,他引:1
运用惰性气体消防抑爆理论,采用数学积分法计算出吹扫煤气设施时抑爆所需最少惰性气体需要量. 相似文献
20.
新型超微晶软磁合金FePCCuMoSi微观结构缺陷的正电子湮没研究 总被引:1,自引:0,他引:1
用正电子湮没方法研究了新型超微晶软磁合金的微观结构缺陷,样品选用的是在不同温度下退火的Fe81P12C3Cu1Mo0.5Si2.5合金,结果表明,合金的微观结构构陷大小,密度随退火温度有规律地变化,这种现象可能与非晶的晶化过程有关。 相似文献