全文获取类型
收费全文 | 1956篇 |
免费 | 50篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 75篇 |
化学工业 | 441篇 |
金属工艺 | 29篇 |
机械仪表 | 51篇 |
建筑科学 | 23篇 |
能源动力 | 91篇 |
轻工业 | 153篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 207篇 |
一般工业技术 | 268篇 |
冶金工业 | 492篇 |
原子能技术 | 69篇 |
自动化技术 | 106篇 |
出版年
2023年 | 8篇 |
2022年 | 25篇 |
2021年 | 37篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 30篇 |
2017年 | 25篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 44篇 |
2013年 | 112篇 |
2012年 | 65篇 |
2011年 | 83篇 |
2010年 | 54篇 |
2009年 | 87篇 |
2008年 | 70篇 |
2007年 | 52篇 |
2006年 | 49篇 |
2005年 | 47篇 |
2004年 | 47篇 |
2003年 | 58篇 |
2002年 | 51篇 |
2001年 | 47篇 |
2000年 | 31篇 |
1999年 | 55篇 |
1998年 | 194篇 |
1997年 | 117篇 |
1996年 | 93篇 |
1995年 | 65篇 |
1994年 | 43篇 |
1993年 | 50篇 |
1992年 | 20篇 |
1991年 | 6篇 |
1990年 | 13篇 |
1989年 | 27篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1978年 | 10篇 |
1977年 | 20篇 |
1976年 | 22篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有2010条查询结果,搜索用时 15 毫秒
1.
2.
Closed-loop expressions for the minimum energy control of a single-input linear digital system are described. They are obtained by two different methods. The optimal inputs are given by state feedback with the bounded variable gains. The gains are independent of the initial state of the system 相似文献
3.
A 4*4 directional coupler switch matrix is developed which uses, for the first time, the quantum confined Stark effect of InGaAlAs/InAlAs multiquantum well structures. The rearrangeable nonblocking 4*4 network with six 2*2 switches is shown to be perfectly functional with switching voltages between 5 and 6 V and crosstalk below -17 dB in all the operation states.<> 相似文献
4.
A newly developed graded-index polymer optical fiber (GI-POF) with high-temperature and high-humidity stability was proposed. As it was found that the high numerical aperture and high glass transition temperature (T/sub g/) at the core center of the GI-POF were key issues to achieve both high-temperature and humidity stability, a partially fluorinated polymer material was adopted to obtain both characteristics in the GI-POF. The newly developed GI-POF had low-loss (140 dB/km at 650-nm wavelength), high-bandwidth (higher than 1 GHz for 100 m transmission), high-temperature and humidity stability at 70/spl deg/C, 80% relative humidity (R.H.) and low bending loss. 相似文献
5.
6.
Takeshi Kondo Hiroyuki Ito Kazuhide Kusakabe Kazuhiro Ohkawa Kensuke Honda Yasuaki Einaga Akira Fujishima Takeshi Kawai 《Diamond and Related Materials》2008,17(1):48-54
The effect of CF4 plasma etching on diamond surfaces, with respect to treatment time, was investigated using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. SEM observations and Raman spectra indicated an increase in surface roughening on a scale of 10–20 nm, and an increase in crystal defect density was apparent with treatment time in the range of 10 s to 30 min. In contrast, alteration of the diamond surface terminations from oxygen to fluorine was found to be rather rapid, with saturation of the F/C atomic ratio estimated from XPS analysis after treatment durations of 1 min and more. The redox kinetics of Fe(CN)63−/4− was also found to be significantly modified after 10 s of CF4 plasma treatment. This behavior shows that C–F terminations predominantly affect the redox kinetics compared to the effect on the surface roughness and crystal defects. The double-layer capacitance (Cdl) of the electrolyte/CF4 plasma-treated boron-doped diamond interface was found to show a minimum value at 1 min of treatment. These results indicate that a short-duration CF4 plasma treatment is effective for the fabrication of fluorine-terminated diamond surfaces without undesirable surface damage. 相似文献
7.
Takeshi Kondo Sang Min Lee Michal Malicki Benoit Domercq Seth R. Marder Bernard Kippelen 《Advanced functional materials》2008,18(7):1112-1118
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs. 相似文献
8.
Recently published studies indicate a potential clinical application of PET in head and neck tumors. In the preoperative staging phase, PET enables confirmation of regional lymph node extension and guides nodal neck dissection or systemic treatment. In this phase, a high negative predictive value, near 100%, could make it possible to avoid many negative neck dissections. This is a reliable technique for confirming or excluding the presence of recurrent/residual tumor and for obtaining an early evaluation of chemotherapeutic and radiotherapeutic response. PET imaging in many cases makes it possible to locate and guide histological study of tumors with an unknown primary. PET imaging for these indications is a perfect complementary method for clinical exploration and better than other imaging techniques. 相似文献
9.
The DNA binding selectivity of new dicationic ligands based on the bis(vinylpyridinium)benzene unit has been investigated by means of UV-Vis absorption spectroscopy. From the experimental results it is concluded that these extended pi-electron bridged viologens have relatively high affinity to AT base pair sequences whereas the binding to GC pairs is about 10 times lower, and binding affinity depends on minor variation in the ligand structure. Linear type ligand exhibits two binding mode interaction, intercalation at high dye concentration which undergoes switching to groove binding at low ligand concentration. 相似文献
10.
T Akahoshi T Nagaoka R Namai N Sekiyama H Kondo 《Canadian Metallurgical Quarterly》1997,16(6):231-235
The effects of monosodium urate (MSU) crystals on apoptosis of cultured peripheral blood neutrophils were investigated. MSU crystals at low concentrations decreased the rate of spontaneous apoptosis of neutrophils in a dose- and time-dependent manner. The culture supernatant of MSU crystal stimulated neutrophils also promoted a delay in neutrophil apoptosis. MSU crystals at higher concentrations rapidly caused cell lysis. These findings indicated that MSU crystals are capable of amplifying the inflammatory responses of gouty arthritis by decreasing the rates of neutrophil apoptosis at lower concentrations and inducing cell lysis at higher concentrations. 相似文献