全文获取类型
收费全文 | 2509篇 |
免费 | 53篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 155篇 |
综合类 | 4篇 |
化学工业 | 473篇 |
金属工艺 | 42篇 |
机械仪表 | 61篇 |
建筑科学 | 46篇 |
能源动力 | 110篇 |
轻工业 | 129篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 327篇 |
一般工业技术 | 486篇 |
冶金工业 | 461篇 |
原子能技术 | 65篇 |
自动化技术 | 198篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 34篇 |
2020年 | 17篇 |
2019年 | 34篇 |
2018年 | 30篇 |
2017年 | 26篇 |
2016年 | 48篇 |
2015年 | 20篇 |
2014年 | 54篇 |
2013年 | 120篇 |
2012年 | 81篇 |
2011年 | 93篇 |
2010年 | 99篇 |
2009年 | 96篇 |
2008年 | 109篇 |
2007年 | 86篇 |
2006年 | 81篇 |
2005年 | 102篇 |
2004年 | 68篇 |
2003年 | 62篇 |
2002年 | 55篇 |
2001年 | 57篇 |
2000年 | 53篇 |
1999年 | 58篇 |
1998年 | 172篇 |
1997年 | 121篇 |
1996年 | 96篇 |
1995年 | 59篇 |
1994年 | 40篇 |
1993年 | 66篇 |
1992年 | 39篇 |
1991年 | 58篇 |
1990年 | 37篇 |
1989年 | 36篇 |
1988年 | 31篇 |
1987年 | 18篇 |
1986年 | 40篇 |
1985年 | 39篇 |
1984年 | 17篇 |
1983年 | 22篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 18篇 |
1977年 | 20篇 |
1976年 | 25篇 |
1974年 | 8篇 |
1972年 | 5篇 |
排序方式: 共有2567条查询结果,搜索用时 125 毫秒
11.
The objectives of this paper are to quantify the effect of Marangini convection on the absorption performance for the ammonia–water absorption process, and to visualize Marangoni convection that is induced by adding a heat transfer additive, n-octanol. A real-time single-wavelength holographic interferometer is used for the visualization using a He–Ne gas laser. The interface temperature is always the highest due to the absorption heat release near the interface. It was found that the thermal boundary layer (TBL) increased faster than the diffusion boundary layer (DBL), and the DBL thickness increased by adding the heat transfer additive. At 5 s after absorption started, the DBL thickness for 5 mass% NH3 without and with the heat transfer additive was 3.0 and 4.5 mm, respectively. Marangoni convection was observed near the interface only in the cases with heat transfer additive. The Marangoni convection was very strong just after the absorption started and it weakened as time elapsed. It was concluded that the absorption performance could be improved by increasing the absorption driving potential (xvb−xvi) and by increasing the heat transfer additive concentration. The absorption heat transfer was enhanced as high as 3.0–4.6 times by adding the heat transfer additive that generated Marangoni convection. 相似文献
12.
Hideaki Katayama Tsutomu Tawa Shinzaburo Ito Masahide Yamamoto Yoshio Wada 《Polymer Bulletin》1992,29(3-4):365-367
Summary The effect of side chain length on intramolecular triplet energy migration of naphthalene containing polymers was investigated by a delayed fluorescence (DF) spectroscopy for the solid solution of the polymers. The degree of triplet energy migration depends strongly on whether the chromophores are directly attached to the main chain or not. 相似文献
13.
An attempt was made to deposit carbon films by electrolysis of a water-ethylene glycol solution. Carbon plate and an n-type silicon substrate were dipped in the solution and a high d.c. potential was negatively applied on the silicon substrate. Some deposits were observed in the region between the boiling point curve and the line approximately 50 °C below and parallel to the boiling point, when electrolysis was carried out at 1 kV for 6 h. For higher potentials of 1.4–2.0 kV and longer electrolysis of 12 h, some samples showed a broad X-ray diffraction peak and Raman peaks, corresponding to graphitic carbon. 相似文献
14.
A Wada Y Masuda M Fukayama T Hatakeyama Y Yanagawa H Watanabe T Inamatsu 《Canadian Metallurgical Quarterly》1996,40(10):767-771
Zinc is an important trace element for immune function. Here, we show that zinc addition in a serum- and lipopolysaccharide-free cell culture system leads to significantly enhanced levels of interleukin 1 beta (IL-1 beta) and tumour necrosis factor alpha (TNF-alpha) and to expression of the corresponding mRNA in human peripheral blood mononuclear cells (PBMC). Structurally related divalent cations like cobalt, nickel, and mercury also partially increase monokine secretion but to a much lower and thus insignificant extent. They fail to induce mRNA of TNF-alpha after 3 h of culture. Therefore, monokine induction is a zinc-specific effect influenced by the physicochemical properties of the ion. Confirmation of the unique significance of zinc for immune function provides a better understanding of the mechanisms of specific zinc-mediated immune modulation. 相似文献
15.
16.
17.
J Tsutsui K Kadomatsu S Matsubara A Nakagawara M Hamanoue S Takao H Shimazu Y Ohi T Muramatsu 《Canadian Metallurgical Quarterly》1993,53(6):1281-1285
Midkine (MK) and heparin-binding growth-associated molecule/pleiotrophin form a new family of heparin-binding growth/differentiation factors. We studied MK gene expression in human tumors. In normal human reference tissues, MK was highly expressed in the mucosal tissue of the small intestine, moderately in the thyroid, weakly in the tissues of the lung, colon, stomach, kidney, and spleen, and not at all in the liver. All of 6 surgically removed specimens of Wilms' tumor highly expressed MK. Also, a moderate to intense level of MK expression was noted in the majority of surgically removed hepatocellular carcinomas. The MK mRNA level was analyzed in a number of cultured and nude mice-transplanted lines of human tumors. In stomach, colon, pancreatic, lung, and esophageal carcinomas, a moderate to high level of MK expression was found in the majority of them. These results suggest an important role of MK in the development and/or biological behavior of tumors and raised a possibility to use MK as a diagnostic marker. Heparin-binding growth associated molecule/pleiotrophin mRNA was low or scarcely detectable in samples analyzed thus far except for significant levels of the expression that were observed in PA-1 teratocarcinoma cells and in some surgical specimens of Wilms' tumor. 相似文献
18.
Hiroyuki Miki Takanori Takeno Toshiyuki Takagi Alexei Bozhko Mikhail Shupegin Hideya Onodera Takao Komiyama Takashi Aoyama 《Diamond and Related Materials》2006,15(11-12):1898
Superconductivity in a tungsten-containing carbon-oxide film was reported. The film with 500 nm thickness was deposited onto polycrystalline silicon oxides using chemical vapor deposition and the co-sputtering of a tungsten metal target. The bonding state of the carbon atoms and the macroscopic and microscopic crystal structure of the film were investigated by Raman spectroscopy, X-ray diffraction and transmission electron microscopy measurements. From the experimental results, we determined that this film essentially had an amorphous structure. The temperature dependence on resistivity was measured in the temperature range of 2–300 K. Resistive superconducting transition was observed at 3.8 K. The dc magnetizations were measured in the temperature range of 1.8–6.5 K. The diamagnetism resulting from a superconductive state was observed below 3.75 K, which is consistent with a resistive superconducting transition. It is thought that the finite sized clusters of the different superconductive transition temperatures cooperatively produce a macroscopic superconducting phenomenon. 相似文献
19.
Ten-user truly asynchronous gigabit OCDMA transmission experiment with a 511-chip SSFBG en/decoder 总被引:8,自引:0,他引:8
Hamanaka T. Xu Wang Naoya Wada Nishiki A. Kitayama K. 《Lightwave Technology, Journal of》2006,24(1):95-102
A ten-user truly asynchronous gigabit coherent-optical-code-division-multiple-access (OCDMA) transmission was experimentally demonstrated without using any timing coordination. The enabling technologies are a record-length 511-chip superstructured-fiber-Bragg-grating (SSFBG) en/decoder and a supercontinuum (SC)-based optical-thresholding technique to significantly suppress the signal interference beat noise as well as the multiple-access-interference (MAI) noise. 相似文献
20.
It is considered that refractory dissolved organic substances have caused an increase in the COD concentration in Lake Biwa in recent years. We investigated the organic matter in the first flush of stormwater runoff from a road in the watershed area of the lake, and studied the possibility of improvement in the water environment from that aspect. After percolating the stormwater through soil, we analyzed organic substances fractionated by using GPC-TC. And we examined the effect of removal of organic substances by comparing the peak height before and after percolation. In the result of the experiments, we found that soil infiltration reduced the refractory dissolved organic substance and we successfully designed a system for a simple and easy experimental facility to treat urban runoff. 相似文献