全文获取类型
收费全文 | 8459篇 |
免费 | 786篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 112篇 |
综合类 | 6篇 |
化学工业 | 2235篇 |
金属工艺 | 396篇 |
机械仪表 | 577篇 |
建筑科学 | 105篇 |
矿业工程 | 5篇 |
能源动力 | 380篇 |
轻工业 | 641篇 |
水利工程 | 16篇 |
石油天然气 | 11篇 |
无线电 | 1465篇 |
一般工业技术 | 2030篇 |
冶金工业 | 378篇 |
原子能技术 | 115篇 |
自动化技术 | 794篇 |
出版年
2023年 | 125篇 |
2022年 | 160篇 |
2021年 | 279篇 |
2020年 | 199篇 |
2019年 | 262篇 |
2018年 | 291篇 |
2017年 | 312篇 |
2016年 | 359篇 |
2015年 | 283篇 |
2014年 | 418篇 |
2013年 | 530篇 |
2012年 | 658篇 |
2011年 | 758篇 |
2010年 | 503篇 |
2009年 | 540篇 |
2008年 | 457篇 |
2007年 | 347篇 |
2006年 | 302篇 |
2005年 | 246篇 |
2004年 | 257篇 |
2003年 | 250篇 |
2002年 | 247篇 |
2001年 | 163篇 |
2000年 | 164篇 |
1999年 | 151篇 |
1998年 | 155篇 |
1997年 | 127篇 |
1996年 | 111篇 |
1995年 | 73篇 |
1994年 | 66篇 |
1993年 | 69篇 |
1992年 | 48篇 |
1991年 | 50篇 |
1990年 | 33篇 |
1989年 | 21篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 35篇 |
1984年 | 21篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 12篇 |
1976年 | 18篇 |
1975年 | 9篇 |
1974年 | 9篇 |
排序方式: 共有9266条查询结果,搜索用时 15 毫秒
91.
Koo Hyun Lee Ki Suk Nam Youl Min Park Pyung Woo Shin Deuk Yong Lee Yo-Seung Song 《Metals and Materials International》2002,8(4):381-385
Plasma nitrocarburized AISI 1020 steels were oxidized for 15, 30 and 60 min to evaluate their corrosion and microstructural properties. After plasma nitrocarburizing for 3 h at 570°C in a gas mixture comprising 85 vol.% N2, 12vol.% H2 and 3 vol.% CH4, the compound layer composed of ɛ-Fe2–3(N,C) and γ’-Fe4(N,C) phases and the diffusion layer above the matrix were observed. The top oxide layer, consisting mainly of magnetite (Fe2O4) and hematite (Fe2O3) phases, forms after post-oxidation treatment at 500°C. However, the oxide layer was severely degraded by spallation as a result of increases in post-oxidizing time. The difference in corrosion resistance should be attributed to the thickness of the top oxide layer, which was governed by post-oxidizing time. 相似文献
92.
Pil-Ryung Cha Ho-Seok Nam Dae-Yeong Jeon Jong-Kyu Yoon 《Metals and Materials International》2002,8(1):119-127
This study presents a simple and robust algorithm for the optimal design of the system with coupled complex transport phenomena:
the transport phenomena comprise fluid flow, heat and mass transfer. The (1+1)-Evolution Strategy method is adopted as the optimization method. In order to analyze the transport phenomena in the complex geometry generated
during the optimization procedure, thefinite volume method with a boundary fitted curvilinear coordinate system is used. To confirm the validity of the present method, the optimal
design for the inner shape of the simplified two-dimensionalSubmerged Entry Nozzle in the continuous slab caster is conducted. It is shown that the resulting design of the nozzle is consistent with the purpose
and constraints of the design. 相似文献
93.
Baik Joon Hyun Yim Sung Dae Nam In-Sik Mok Young Sun Lee Jong-Hwan Cho Byong K. Oh Se H. 《Topics in Catalysis》2004,30(1-4):37-41
Topics in Catalysis - Among the catalysts screened, Cu-ion exchanged ZSM5 zeolite exhibited the highest NO removal activity, particularly at low reaction temperatures below 200 °C,... 相似文献
94.
Irina Tsarenko Sang Park Honghua Du Woo Y. Lee 《Journal of the American Ceramic Society》2003,86(9):1622-1624
A 25 nm thick α-alumina layer was deposited on a turbine-grade silicon nitride by sol-gel dip coating and subsequent heat treatment in air at 1200°C. This layer had a nanometer grain structure. Silicon nitride protected by this thin layer showed a significant improvement in oxidation resistance over its uncoated counterpart after 200 cyclic exposures in air at 1250°C. The oxide layer grown on the coated silicon nitride also exhibited superior surface morphology, compared with the uncoated silicon nitride. 相似文献
95.
Copoly(amide-ethers) containing two types of tertiary amine units were made as antistatic modifiers for poly(ethylene terephthalate) (PET) fibers. The filaments of the copolymers were melt-spun and reacted with three alkylating agents in order to quaternize the tertiary amine into a sulfo-betaine, a carbobetaine, and an ammonium ion. The apparent electric resistivity of the filaments was greatly reduced by this reaction, being in the range of 106 to 108 Ω/cm. However, because these quaternized copolymers incurred decomposition during blend spinning with PET, a blend PET fiber containing one type of copoly(amide-ether) was melt-spun and subjected to quaternization of the amino groups as well as to surface crosslinking with various alkylating and epoxy agents. The quaternized blend fibers obtained showed improved antistatic properties compared with the original blend fiber. Particularly, the fibers crosslinked with epoxy compounds were found to have the best antistatic properties that had ever been attained with this type of modification. The antistatic properties were retained even after dyeing, because both hydrophilic and ionic groups had been effectively immobilized on the surface. Since this quaternization and crosslinking could be conducted on-line with spinning and drawing within a short reaction time, this modification technique is called “spin-finishing method”, which should be superior to the conventional methods in terms of cost performance and productivity. 相似文献
96.
High‐density polyethylene (HDPE) beads were successfully surface‐crosslinked in a modified plasma reactor. The modified plasma reactor treats large amounts of beads, which are uniformly surface‐crosslinked. In this study, effects of the gas pressure, radio‐frequency (RF) power, and the treatment time on the degree of surface crosslinking were systematically investigated. Degree of surface crosslinking was measured by solvent extraction method (boiling xylene method, BXM). The gel content of plasma‐treated HDPE increases from 0.0 to 1.05% within 10 min at 100 mTorr, 200 W. FTIR and DSC analyses show that the crosslinked layer after plasma treatment is limited only at HDPE surface without changing the bulk thermal property of HDPE. Through the analysis of FTIR, it was confirmed that main peaks corresponding to CH2 bands were decreased and two peaks corresponding to CF2 and CF3 were observed after plasma surface modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2921–2929, 2002; DOI 10.1002/app.10295 相似文献
97.
Summary The surface modification of low-density polyethylene(PE) by liquid phase photograft polymerization with acrylic acid(AA), acrylamide(AM) and glycidyl methacrylate(GMA) was described. The grafting of AA and AM was proved and characterized by electron spectroscopy for chemical analysis(ESCA). It was found that fully hydrophilic surface can be obtained in very short irradiation time. With ESCA and attenuated total reflection infrared spectroscopy(ATR-IR), it can be confirmed that bifunctional monomer GMA was grafted onto the PE film surface. Through further reaction with GMA grafted film, heparin and protamine were immobilized onto the grafted film surface. 相似文献
98.
99.
Jin-Kwang Bok Heeman Lee Jay Woo Chang Sunwon Park 《Korean Journal of Chemical Engineering》2002,19(4):545-551
This paper presents a hybrid refinery scheduling system combining mathematical programming model and expert system. Mixed-integer
linear programming models for crude oil movement between units are merged into the expert system that is for qualitative issues
concerning crude vessel unloading operations. The target problem ranging from the crude unloading to the crude charging to
distillation towers is decomposed into several module problems for efficiency. Compared with existing scheduling approaches
for oil movement, the proposed hybrid refinery scheduling system is very effective in dealing with timing decisions involving
vessel unloading operations due to the advantages of an expert system. Since the proposed scheduling system can generate solutions
so fast, it is expected to play a key role in the real processes.
This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University. 相似文献
100.
The synergistic effects of boron nitride (BN) powder and die on the rheology and processability of metallocene‐catalyzed low density polyethylene (mLDPE) were investigated. The processability in the extrusion process is closely related to the interfacial properties between the polymer melts and the die wall. BN powder was added to mLDPE to reduce the friction coefficient and surface energy. Adding 0.5 wt% BN powder to mLDPE was very effective in improving the processability and the extrudate appearance. To study the effect of die surface property, three different dies were applied in capillary extrusion. One was conventional tungsten carbide (TC) die, and the others were hot‐pressed BN (hpBN) die and hot‐pressed BN composite (hpBNC) die. The applications of these BN dies were quite effective in delaying surface melt fracture (sharkskin) and postponing gross melt fracture to higher shear rate compared to the TC die. These improvements result from the fact that BN dies reduce the wall shear stress significantly and promote slip. The synergistic effect of processability could be obtained when both BN powder and hpBN die were used together. 相似文献