全文获取类型
收费全文 | 52281篇 |
免费 | 2690篇 |
国内免费 | 1380篇 |
专业分类
电工技术 | 1001篇 |
技术理论 | 11篇 |
综合类 | 691篇 |
化学工业 | 10908篇 |
金属工艺 | 2744篇 |
机械仪表 | 2231篇 |
建筑科学 | 2072篇 |
矿业工程 | 364篇 |
能源动力 | 3993篇 |
轻工业 | 4036篇 |
水利工程 | 411篇 |
石油天然气 | 567篇 |
武器工业 | 61篇 |
无线电 | 4571篇 |
一般工业技术 | 9596篇 |
冶金工业 | 2243篇 |
原子能技术 | 904篇 |
自动化技术 | 9947篇 |
出版年
2024年 | 67篇 |
2023年 | 1001篇 |
2022年 | 1038篇 |
2021年 | 1381篇 |
2020年 | 1330篇 |
2019年 | 1237篇 |
2018年 | 1162篇 |
2017年 | 1874篇 |
2016年 | 1928篇 |
2015年 | 1856篇 |
2014年 | 2842篇 |
2013年 | 3777篇 |
2012年 | 3199篇 |
2011年 | 3705篇 |
2010年 | 3277篇 |
2009年 | 3606篇 |
2008年 | 2759篇 |
2007年 | 3838篇 |
2006年 | 3235篇 |
2005年 | 1988篇 |
2004年 | 1156篇 |
2003年 | 1296篇 |
2002年 | 1194篇 |
2001年 | 963篇 |
2000年 | 749篇 |
1999年 | 863篇 |
1998年 | 1040篇 |
1997年 | 533篇 |
1996年 | 360篇 |
1995年 | 258篇 |
1994年 | 225篇 |
1993年 | 181篇 |
1992年 | 144篇 |
1991年 | 137篇 |
1990年 | 138篇 |
1989年 | 124篇 |
1988年 | 248篇 |
1987年 | 451篇 |
1986年 | 412篇 |
1985年 | 146篇 |
1984年 | 95篇 |
1983年 | 73篇 |
1982年 | 53篇 |
1981年 | 72篇 |
1980年 | 64篇 |
1979年 | 72篇 |
1978年 | 63篇 |
1977年 | 19篇 |
1976年 | 39篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(8):10852-10861
Carbon cloth was used as a flexible substrate for bismuth telluride (Bi2Te3) particles to provide flexibility and improve the overall thermoelectric performance. Bi2Te3 on carbon cloth (Bi2Te3/CC) was synthesized via a hydrothermal reaction with various reaction times. After over 12 h, the Bi2Te3 particles showed a clear hexagonal shape and were evenly adhered to the carbon cloth. Selenium (Se) atoms were doped into the Bi2Te3 structure to improve its thermoelectric performance. The electrical conductivity increased with increasing Se-dopant content until 40% Se was added. Moreover, the maximum power factor was 1300 μW/mK2 at 473 K for the 30% Se-doped sample. The carbon cloth substrate maintained its electrical resistivity and flexibility after 2000 bending cycles. A flexible thermoelectric generator (TEG) fabricated using the five pairs of 30% Se-doped sample showed an open-circuit voltage of 17.4 mV and maximum power output of 850 nW at temperature difference ΔT = 30 K. This work offers a promising approach for providing flexibility and improving the thermoelectric performance of inorganic thermoelectric materials for wearable device applications using flexible carbon cloth substrate for low temperature range application. 相似文献
2.
《Journal of the European Ceramic Society》2022,42(5):2429-2440
A ring-on-ring (ROR) test is a prevailing test method for evaluating the equi-biaxial strength of glass materials. However, current ROR test standards limit the strength and size of glass to prevent a nonlinear behavior. In this study, the feasibility of ROR testing for non-standard, high-strength glass, such as tempered or ion-exchanged rectangular glass is investigated. To this end, ROR simulation based on theory and experiment is conducted for thirty non-standard glasses with widths of 100–300 mm and aspect ratios of 1.0–2.0. As a result, the maximum measurable stress was about 215.6 MPa for 100 × 200 mm glass and 481.3 MPa for 300 × 600 mm glass with a 3% deviation, which is well above the strength of regular tempered glass. The main purpose of this work is to understand the range of aspect ratio of horizontal and vertical widths of a glass plate that can be evaluated by the standard ROR test. 相似文献
3.
Ohmic heating (OH) allows a natural synergy between thermal and electrical effects, appearing as an efficient approach to the thermal extraction of biocompounds. Different electrical field intensities (e.g., 12 and 217 V/cm), treatment temperatures (from 50 to 100 °C) and heating strategies (continuous and pulsed heating) were combined to enhance for the first time the extraction of nutrients from microalgae Coelastrella sp. LFR1, which is highly adapted to extreme survival conditions. Results showed that OH applied at 217 V/cm, through a fast and single heating pulse (OHP), and at maximum peak temperature of approximately 100 °C (with <1 s of holding time), resulted in the maximum recovery of 50% of chlorophyll a (e.g., 1.02 mg/gDW) and 20.4% of proteins (29.4 mg/gDW) from biomass; lipids and carbohydrates were equally extracted resulting on extraction of 40 and 52%, respectively. OHP allowed to obtain nutrient rich extracts from Coelastrella sp. LFR1 with a significant radical scavenging activity ranging from 20 to 60%. 相似文献
4.
5.
Atsuki Yamaguchi Kazuki Fukui Yuki Fujiwara Shingo Tamaki Sachie Kusaka Fuminobu Sato 《Journal of Nuclear Science and Technology》2021,58(1):80-86
ABSTRACT It is important to perform neutron transport simulations with accurate nuclear data in the neutronics design of a fusion reactor. However, absolute values of large-angle scattering cross sections vary among nuclear data libraries even for well-examined nuclide of iron. Benchmark experiments focusing on large-angle scattering cross sections were thus performed to confirm the correctness of nuclear data libraries. The series benchmark experiments were performed at a DT neutron source facility, OKTAVIAN of Osaka University, Japan, by the unique experimental system established by the authors’ group, which can extract only the contribution of large-angle scattering reactions. This system consists of two shadow bars, target plate (iron), and neutron detector (niobium). Two types of shadow bars were used and four irradiations were conducted for one experiment, so that contribution of room-return neutrons was effectively removed and only large-angle scattering neutrons were extracted from the measured four Nb reaction rates. The obtained experimental results were compared with calculations for five nuclear data libraries including JENDL-4.0, JEFF.-3.3, FENDL-3.1, ENDF/B- VII, and recently released ENDF/B-VIII. It was found from the comparison that ENDF/B-VIII showed the best result, though ENDF/B-VII showed overestimation and others are in large underestimation at 14 MeV. 相似文献
6.
Hiromi Eba Yuki Masuzoe Toru Sugihara Hayao Yagi Tian Liu 《International Journal of Hydrogen Energy》2021,46(18):10642-10652
Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe3N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide. 相似文献
7.
《International Journal of Hydrogen Energy》2021,46(73):36291-36300
A new reverse build-up method is developed to fabricate an economical H2-permeable composite membrane. Sputtering and electroplating are used for the formation of a membrane comprised of a 3.7-μm-thick Pd60Cu40 (wt.%) alloy layer and a 13-μm-thick porous Ni support layer, respectively. The H2-permeation measurements are performed under the flow of a gaseous mixture of H2 and He at 300–320 °C and 50–100 kPa of H2 partial pressure. The H2/He selectivity values exceed 300. The activation energy at 300–320 °C is 10.9 kJ mol−1. The H2 permeability of the membrane is 1.25 × 10−8 mol m−1 s−1 Pa−0.5 at 320 °C after 448 h. The estimated Pd cost of the proposed membrane is approximately 1/8 of the cost for a pure Pd60Cu40 membrane. This study demonstrates that the proposed method allows the facile production of low-cost, Pd-based membranes for H2 separation. 相似文献
8.
《Ceramics International》2021,47(23):32969-32978
In this study, hydroxyapatite-based hydroxyapatite-wollastonite-boron nitride (HAp-Wo-BN) composite film was formed on the surface of Ti6Al4V by pulsed laser deposition (PLD). Based on a survey in scientific literature, it is presumed that this is the first time such a process is being undertaken. The wear and corrosion resistance of this film were analyzed comparatively in simulated body fluid (SBF) to simulate the human body environment. In the coating, HAp was used to form a bone-like layer, wollastonite was to enhance bone-tissue regeneration and BN was used for its bone-tissue healing and anti-bacterial properties. The results showed that the wear as well as the corrosion resistance of all samples after PLD treatment increased. Relatively the best wear resistance was achieved from boron nitride and wollastonite doped hydroxyapatite layers, where the best corrosion resistance was from the ones that consisted of only hydroxyapatite. 相似文献
9.
Aniruddha Nag Mohammed Asif Ali Jiabei Zhou Makoto Ogawa Tatsuo Kaneko 《大分子材料与工程》2021,306(11):2100459
Aromatic and functional polymers with processibility derived from biobased starting materials are prerequisite considering sustainable society. Poly(2,5-benzimidazole)s are rigid-rod polymers to show ultrahigh thermal stability such as flame retardance, while usually suffer from poor solubility. Here, poly(benzimidazole-co-amide)s are synthesized from two biobased monomers, 3,4-diaminobenzoic acid and a semirigid comonomer, 4-aminohydrocinnamic acid. The copolymers with an amide composition of 80 mol% and higher are soluble in widely used polar solvents to fabricate the films keeping high flame retardance, which is comparable with popular high-performance polymers such as aromatic polyimides, polyetheretherketone, polyphenylene sulfide, etc. 相似文献
10.
《Advanced Powder Technology》2022,33(8):103602
To operate a bag filter continuously, pulse-jet cleaning of dust particles from the filter medium is commonly required, and the pulse-jet pressure significantly affects the filter performance. In this study, the accumulation structure of residual dust particles inside and on the surface of a filter medium at different pulse-jet pressures was investigated by constructing a simple model, and the influence of the dust structure on the filter performance was clarified. Using a simple model, we determined the effective ratio of filtration area β, which represents the ratio of the filterable area to the total filtration area, the true resistance coefficient due to the primary dust layer ζp’ thinly deposited on the filter surface, and the true resistance coefficient inside the filter media itself ζf’. The effective ratio of filtration area β decreased with operation time for all pulse-jet pressures; however, it maintained a high value when the pulse-jet pressure was high. The validity of β analyzed by the model was verified using two different methods, and the results showed good agreement, indicating that the model is effective in identifying real conditions. The true resistance coefficient due to the primary dust layer ζp’ decreased as the pulse-jet pressure increased; however, the true resistance coefficient inside the filter media itself ζf’ was the highest at 0.5 MPa. In addition, the dust collection efficiency was different at each pulse-jet pressure, which was considered to be caused by the difference in the dust particle accumulation structure. 相似文献