全文获取类型
收费全文 | 1506篇 |
免费 | 69篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 88篇 |
综合类 | 3篇 |
化学工业 | 453篇 |
金属工艺 | 67篇 |
机械仪表 | 30篇 |
建筑科学 | 22篇 |
矿业工程 | 1篇 |
能源动力 | 85篇 |
轻工业 | 124篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 83篇 |
一般工业技术 | 358篇 |
冶金工业 | 59篇 |
原子能技术 | 48篇 |
自动化技术 | 148篇 |
出版年
2023年 | 9篇 |
2022年 | 7篇 |
2021年 | 36篇 |
2020年 | 16篇 |
2019年 | 39篇 |
2018年 | 40篇 |
2017年 | 34篇 |
2016年 | 54篇 |
2015年 | 38篇 |
2014年 | 40篇 |
2013年 | 78篇 |
2012年 | 84篇 |
2011年 | 112篇 |
2010年 | 71篇 |
2009年 | 91篇 |
2008年 | 83篇 |
2007年 | 76篇 |
2006年 | 54篇 |
2005年 | 50篇 |
2004年 | 60篇 |
2003年 | 46篇 |
2002年 | 38篇 |
2001年 | 40篇 |
2000年 | 27篇 |
1999年 | 34篇 |
1998年 | 35篇 |
1997年 | 31篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 15篇 |
1993年 | 23篇 |
1992年 | 20篇 |
1991年 | 26篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有1578条查询结果,搜索用时 15 毫秒
101.
102.
Rare-earth (RE: Lu, Gd, Nd, 0.10 mol%)-doped alumina nanopowders were prepared by a new sol-gel route using polyhydroxoaluminum (PHA) and RECl3 solutions under α-alumina (∼ 75 nm) seeding. Among the rare-earth dopants studied, Lu yields the most suitable nanopowders for low-temperature densification. The 0.10 mol% Lu-doped nanopowders, which were obtained at a calcination temperature of 900 °C under 5 mass% α-alumina seeding, consisted of ∼ 80-nm α-alumina particles and γ-alumina nanoparticles. Using these Lu-doped alumina nanopowders, fully densified alumina ceramics with a uniform microstructure composed of fine grains with an average size of 0.61 μm could be obtained at 1400 °C by pressureless sintering. Clearly, the Lu-doped nanopowders obtained here represent a viable option for fabricating dense, finer-grained alumina ceramics because an undoped sample with 5 mass% seeds gave a microstructure with an average grain size of 1.78 μm at 1400 °C. 相似文献
103.
To identify the differences in the knowledge production between disciplines, we analyzed the relation between the average
paper length and impact factor of 100 journals from 5 disciplines. We found negative correlation between the average length
and the impact factor in the natural sciences, but not in the social sciences. We also analyzed the structures of paper and
the citation patterns. These analyses are expanded to the comparison between Mode 1 and Mode 2. All results showed the natural
sciences articles could emphasize the differences from previous studies and be diffused effectively by the short standardized
style of paper.
This research is partly funded by International Program in Special Coordinating Funds for Promoting S&T from Science and Technology
Agency of Japan. 相似文献
104.
S Fujikawa 《Journal of microscopy》1979,117(2):261-267
The present study was undertaken to report a new method which reveals the ultrastructure of freeze-fractured membrane faces. The method consists of initial replication of fractured surfaces of frozen specimens with evaporated carbon and treatment of the replicas with a negative staining solution after dissolution of specimens. This negative staining-carbon replica method reveals clear distribution, ultrastructures and precise size of intramembrane particles on the fractured membrane faces by means of density difference of negative staining solution which is deposited on the surfaces of carbon replicas. 相似文献
105.
Increase of stress intensity near interface edge of elastic-creep Bi-material under a sustained load
The transition from small-scale creep to large-scale creep ahead of a crack tip or an interface edge with strong elastic stress singularity at the loading instant causes stress relaxation and the decrease of stress intensity in general. However, this study shows that the stress near the interface edge of bi-material with no or weak elastic stress singularity increases after the loading instant and brings about the stress concentration during the transition. In addition, the creep strain distribution of this bi-material after the loading instant is different from that occurred in the transition of an interface edge with strong elastic stress singularity or a crack tip (notch root). The criterion for the increase or decrease of stress intensity near the interface edge proved by the finite element method is proposed in this study. The stress intensity near the interface edge increases when the elastic stress singularity is lower than the creep stress singularity (λel < λcr) and vice versa. 相似文献
106.
107.
Kazuya Sasaki Takayuki Terai Akihiro Suzuki 《International Journal of Applied Ceramic Technology》2009,6(3):362-372
The microstructure of a thermal shielding material affects its thermal conductivity and mechanical property. In this study, the effects of the sintering temperature and the polymethyl methacrylate powder as a pore-former on the microstructure of a sintered porous yttria-stabilized zirconia (YSZ), which is used as a durable thermal shielding material, were investigated. It became clear that the microstructure of the sintered YSZ could be controlled by the particle size and the amount of the pore-former and the sintering temperature. The effect of the yttria amount in the YSZ on the microstructure was also clarified. 相似文献
108.
This paper presents a precise and stable time integration method for dynamic analysis of vibration or multibody systems A total system is divided into several subsystems and then responses are calculated separately, while the coupling effect is treated equivalently as constant force during time steps By using iterative procedure to improve equivalent coupling forces, a precise and stable solution is obtained Some examples such as a seismic response and multibody analyses were carried out to demonstrate its usefulness
相似文献109.
110.
Rong-Jun Xie Naoto Hirosaki Mamoru Mitomo Takayuki Suehiro Xin Xu Hidehiko Tanaka 《Journal of the American Ceramic Society》2005,88(10):2883-2888
Rare-earth-doped Ca-α-SiAlON phosphors, with the compositions of (Ca1−3/2 x RE x ) m /2 Si12− m − n Al m+n O n N16− n (RE=Ce, Sm, and Dy, 0.5≤ m =2 n ≤3.0), were prepared by sintering at 1700°C for 2 h under 10 atm N2 . The concentration of rare earths varied from 3 to 30 at.% with respect to Ca. The photoluminescence (PL) properties were investigated as functions of the composition of the host matrix (i.e., m ) and the concentration of rare earths (i.e., x ). The results show that the emission properties can be optimized by tailoring m and x . The Ce3+ luminescence originating from the 4 f –5 d interconfigurational transitions is greatly affected by the environment surrounding the Ce3+ ions, which differs from the Sm3+ or Dy3+ luminescence arising from the 4 f –4 f intraconfigurational transitions. X-ray diffraction and scanning electron microscopy were used to explain the composition and concentration dependence of PL properties. 相似文献