全文获取类型
收费全文 | 10460篇 |
免费 | 908篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 124篇 |
综合类 | 17篇 |
化学工业 | 2687篇 |
金属工艺 | 389篇 |
机械仪表 | 490篇 |
建筑科学 | 152篇 |
矿业工程 | 3篇 |
能源动力 | 389篇 |
轻工业 | 1223篇 |
水利工程 | 38篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 1725篇 |
一般工业技术 | 2424篇 |
冶金工业 | 639篇 |
原子能技术 | 92篇 |
自动化技术 | 984篇 |
出版年
2024年 | 14篇 |
2023年 | 161篇 |
2022年 | 252篇 |
2021年 | 420篇 |
2020年 | 293篇 |
2019年 | 285篇 |
2018年 | 379篇 |
2017年 | 410篇 |
2016年 | 488篇 |
2015年 | 433篇 |
2014年 | 556篇 |
2013年 | 740篇 |
2012年 | 777篇 |
2011年 | 984篇 |
2010年 | 687篇 |
2009年 | 641篇 |
2008年 | 534篇 |
2007年 | 449篇 |
2006年 | 366篇 |
2005年 | 312篇 |
2004年 | 305篇 |
2003年 | 253篇 |
2002年 | 187篇 |
2001年 | 166篇 |
2000年 | 165篇 |
1999年 | 148篇 |
1998年 | 242篇 |
1997年 | 145篇 |
1996年 | 116篇 |
1995年 | 64篇 |
1994年 | 70篇 |
1993年 | 53篇 |
1992年 | 42篇 |
1991年 | 27篇 |
1990年 | 26篇 |
1989年 | 26篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1974年 | 7篇 |
1971年 | 7篇 |
1970年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Jin Young Kim Hyun Suk Jung Kug Sun Hong 《Journal of the American Ceramic Society》2005,88(3):784-787
The influences of acetic acid addition to Mg-methoxide on the stability of the precursor and the crystallization behavior of sol–gel-derived MgO nano-powders and thin films were investigated using X-ray powder diffraction, transmission electron microscopy, Fourier-transformed infrared spectroscopy, and thermogravimetry. The addition of acetic acid enhanced the stability of the alkoxide against precipitation. Moreover, during postheat treatment of the gel powders treated with acetic acid, a significantly lowered crystallization temperature (250°C) was observed as compared to the untreated counterpart (350°C). The low-temperature crystallization of MgO, induced by the modification of Mg-methoxide with acetic acid, was related to the decomposition of organics at a lower temperature. These results could be explained in terms of the decrease of the O–R bond strength depending on the increase in the alkyl group size. MgO thin films having a high degree of crystallinity were successfully obtained from the Mg-methoxide treated with acetic acid at 300°C. The low-temperature crystallization of sol–gel-derived MgO thin films showed the feasibility for their application as a protective layer in alternative current plasma display panel cells. 相似文献
82.
G. R. Agladze G. S. Tsurtsumia B. -I. Jung J. -S. Kim G. Gorelishvili 《Journal of Applied Electrochemistry》2007,37(9):985-990
The technological and economic aspects of using the Fenton process to treat industrial wastewater containing morpholyne and
diethylethanolamine, as well as sodium salts of naphthalene sulfonic acid and of ethylenediaminetetraacetic acid based on
data obtained in pilot tests are discussed. Chemical Fenton technology was tested using commercial 30–35% solutions of H2O2 and iron (II) salts, which was followed by the additional electrochemical destruction of organic pollutants in an undivided
reactor with catalytic stable anodes (CSA) and 1 g L−1 NaCl as a supporting electrolyte and a source of active chlorine. An alternative electrochemical method involving the electrogeneration
of hydrogen peroxide in polluted water at the gas
-diffusion cathode was studied both with the addition of ferrous salt to the electrolyte prior to electrolysis (in-cell electro-Fenton)
as well as with the post-electrolysis addition of Fe2+ in another reactor (ex-cell electro-Fenton). The accumulation of hydrogen peroxide in concentrations sufficient for the mineralization
of organic pollutants was achieved in both cases with near 100% current efficiency. In comparison with wastewater treatment
processes which use a purchased hydrogen peroxide reagent, the Fenton-like processes achieved an economic savings of as much
as 64.5% in running costs due to the on-site electrochemical generation of H2O2. Preparative electrolysis in the membrane reactor showed higher current efficiencies and lower specific energy consumptions
for H2O2 electrogeneration in comparison with the results of tests carried out in an undivided cell. 相似文献
83.
Unsaturated polyester (UP)/montmorillonite (MMT) nanocomposite was prepared by using hydroxypropylacrylate (HPA) as a reactive diluent instead of conventional styrene monomer and the effect of polarity of reactive diluent on properties of nanocomposite was investigated. X‐ray and mechanical test data indicated that mixing for an extended period of time is essential to enhance the physical properties of nanocomposites in the UP/Cloisite 6A system. This was attributed to the high polarity of HPA that may disturb the preintercalation of UP resin into the galleries of MMT. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 238–242, 2004 相似文献
84.
Momoji Kubo Tsuguo Kubota Changho Jung Minako Ando Satoshi Sakahara Kenji Yajima Kotaro Seki Rodion Belosludov Akira Endou Seiichi Takami Akira Miyamoto 《Catalysis Today》2004,89(4):479-493
Recently, we introduced a concept of combinatorial chemistry to computational chemistry and proposed a new method called “combinatorial computational chemistry”, which enables us to perform a theoretical high-throughput screening of catalysts. In the present paper, we reviewed our recent application of our combinatorial computational chemistry approach to the design of new catalysts for high-quality transportation fuels. By using our combinatorial computational chemistry techniques, we succeeded to predict new catalysts for methanol synthesis and Fischer–Tropsch synthesis. Moreover, we have succeeded in the development of chemical reaction dynamics simulator based on our original tight-binding quantum chemical molecular dynamics method. This program realizes more than 5000 times acceleration compared to the regular first-principles molecular dynamics method. Electronic- and atomic-level information on the catalytic reaction dynamics at reaction temperatures significantly contributes the catalyst design and development. Hence, we also summarized our recent applications of the above quantum chemical molecular dynamics method to the clarification of the methanol synthesis dynamics in this review. 相似文献
85.
Changho Jung Hideyuki Tsuboi Michihisa Koyama Momoji Kubo Ewa Broclawik Akira Miyamoto 《Catalysis Today》2006,111(3-4):322-327
CO adsorption over Pd4 and Pt4 cluster supported by c-ZrO2(1 1 1) and CeO2(1 1 1) catalyst systems was investigated using periodic density functional method in order to clarify the support effect on CO activation. We found that the support increases the CO activation for bridge and three-fold sites but decreases for the atop site. Moreover, it was found that the support changes the site preference for the CO adsorption. Bridge site on both the Pt4/c-ZrO2 and Pt4/CeO2 show larger CO adsorption energies than those on the other sites while the atop site is energetically preferable on isolated Pt4 cluster. c-ZrO2 supported Pd shows the largest CO activation with large charge transfer from the catalyst to the CO molecule. This reveals that ZrO2 supported Pd can be a good catalyst for CO activation because of its higher probability to the three-fold site CO adsorption. We also found that positively charged M4 clusters on the support keep their strong electron-donating properties and have enough charge density to contribute to the activation of an adsorbed CO molecule by a charge transfer. 相似文献
86.
Jun-Bin Ko Sung Wook Lee Dong Eun Kim Young Un Kim Gang Li Seung Goo Lee Tae-Sun Chang Dojin Kim Yong Lak Joo 《Journal of Porous Materials》2006,13(3):325-330
(1 − x)SiO2-(x)ZrO2 (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl
orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction
(XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite
fibers having a tetragonal crystalline ZrO2 were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and
crystallization of ZrO2 in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did
not depend on the sintering temperature. 相似文献
87.
Case-based context ontology construction using fuzzy set theory for personalized service in a smart home environment 总被引:1,自引:1,他引:0
Mye Sohn Sunghwan Jeong Hyun Jung Lee 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(9):1715-1728
To provide context-based personalized services utilizing smart appliances in a smart home environment, we propose a framework for PersonAlized Service disCovery Using FuZZY-based CBR and Context Ontology (PASCUZZY). Basically, the PASCUZZY framework is implemented on case-based context ontology. To generate and manage the case instances on the case-based context ontology, we adopt the fuzzy set theory to transpose numerical-type context data sensed from the surrounding environment. The context is transposed to linguistic-type context instances on the context ontology. In addition, to formalize and manage the context and services as multi-attributed data, the context ontology was developed reflecting the structure of cases borrowed from case-based reasoning. Furthermore, we propose adaptation methods to adjust the generic fuzzy membership functions depending on the inhabitants’ context. It is performed by modifying the values of the membership number and/or modifying the numbers of the linguistic terms that are based on the inhabitants’ context to affect the membership numbers. The adapted membership functions return the personalized degree of memberships depending on the specialized context of a specific fuzzy variable. Inevitably, the number of cases on the case-based context ontology will be increased from time to time. We apply Ward’s method not only to reduce the search effort via a hierarchical clustering on the case-based context ontology but also to find the most similar service as a solution to the new context. To verify the superiority of the PASCUZZY framework, we perform two kinds of evaluations. First, we evaluate the effectiveness of the adaptation of the fuzzy membership functions. Second, we verify the effectiveness of the application of a clustering method to the case instances of the case-based context ontology to identify the most similar service. Results of the experiment verified the effectiveness and superiority of the PASCUZZY framework. 相似文献
88.
Tae Oan Ahn Chang Kee Kim Byung Kyu Kim Han Mo Jeong Jung Do Huh 《Polymer Engineering and Science》1990,30(6):341-349
Binary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH-62) and 71 (EVOH-71) mole percent vinyl alcohols, with nylons (nylon-6, nylon-6/12, and nylon-12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH-62/nylon-6 and EVOH-71/nylon-6 blends showed homogeneous phase morphologies in the nylon-6-rich region, and fine phase separations (c.a. 2 × 10?7 m) in the EVOH-rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH-71/nylon-6/12 and EVOH-71 /nylon-12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed. 相似文献
89.
The effects of potassium on the catalytic behavior in CO hydrogenation over K-promoted Fe/carbon catalysts having low K/Fe
ratios were investigated. Even though the doses of potassium were low the promotional effects were pronounced, especially
on the olefin-to-paraffin ratio, and theC
3
toC
4
olefin selectivities of the K-promoted catalysts were as high as 51 to 66 mol%. Over the catalysts having no or low potassium
content the olefin-to-paraffin ratio and the ratio of the CO2 formation rate to the rate of CO conversion to hydrocarbons remained roughly the same regardless of temperature, while over
the K-promoted catalysts having higher potassium content they increased with temperature. Formation of significant amounts
of filamentous carbon was observed in the K-promoted catalysts; however, the carbon deposition did not appear to affect the
inherent activity and selectivity of the K-promoted catalysts. 相似文献
90.
Hong-Gi Lee Jung Youn Lee Kyung-Duk Kim Hoon Kang 《International Journal of Control, Automation and Systems》2014,12(5):1124-1130
Unlike the continuous-time case, algebraic necessary and sufficient conditions for a single output discrete-time system to be state equivalent to a nonlinear observer canonical form have been found and are easier to verify for those who are not accustomed to differential geometry. The geometric conditions look very different from the algebraic conditions. In this paper, we show direct equivalence of the geometric conditions and the algebraic conditions in order to enhance the understanding of the geometric conditions. 相似文献