全文获取类型
收费全文 | 12750篇 |
免费 | 349篇 |
国内免费 | 273篇 |
专业分类
电工技术 | 323篇 |
综合类 | 526篇 |
化学工业 | 1512篇 |
金属工艺 | 710篇 |
机械仪表 | 1170篇 |
建筑科学 | 1201篇 |
矿业工程 | 692篇 |
能源动力 | 438篇 |
轻工业 | 890篇 |
水利工程 | 149篇 |
石油天然气 | 703篇 |
武器工业 | 103篇 |
无线电 | 508篇 |
一般工业技术 | 1596篇 |
冶金工业 | 577篇 |
原子能技术 | 345篇 |
自动化技术 | 1929篇 |
出版年
2024年 | 17篇 |
2023年 | 75篇 |
2022年 | 280篇 |
2021年 | 235篇 |
2020年 | 188篇 |
2019年 | 142篇 |
2018年 | 164篇 |
2017年 | 212篇 |
2016年 | 296篇 |
2015年 | 344篇 |
2014年 | 617篇 |
2013年 | 678篇 |
2012年 | 740篇 |
2011年 | 903篇 |
2010年 | 757篇 |
2009年 | 685篇 |
2008年 | 651篇 |
2007年 | 744篇 |
2006年 | 755篇 |
2005年 | 689篇 |
2004年 | 585篇 |
2003年 | 609篇 |
2002年 | 516篇 |
2001年 | 410篇 |
2000年 | 382篇 |
1999年 | 350篇 |
1998年 | 274篇 |
1997年 | 226篇 |
1996年 | 185篇 |
1995年 | 163篇 |
1994年 | 120篇 |
1993年 | 88篇 |
1992年 | 66篇 |
1991年 | 36篇 |
1990年 | 38篇 |
1989年 | 50篇 |
1988年 | 23篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(10):6710-6720
Herein, molybdenum disulfide nanoflakes decorated copper phthalocyanine microrods (CuPc-MoS2) are synthesized via two step simple hydrothermal method. The as synthesized hybrid along with pure molybdenum disulfide (MoS2) nanoflower and pure copper phthalocyanine (CuPc) microrods are well characterized by various techniques that confirm phase, morphology, elemental compositions etc. Next, electrocatalytic oxygen reduction reaction towards fuel cell is investigated in alkaline medium and obtained results proclaim that our CuPc-MoS2 heterostructure outperforms the other two constituent materials. Efficient oxygen reduction is achieved following four electron pathway by CuPc-MoS2 whereas partial reduction is done through two electron process by CuPc and MoS2 separately. Long-time durability test reveals almost 97.6% retention after 8000s that eventually dictate us that CuPc-MoS2 heterostructure can be the efficient cathode electrocatalyst for future generation fuel cell. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(12):8130-8144
Compared to liquid/gas hydrogen tank, the pipeline is an economical way for hydrogen transportation. With the quick development of utility tunnel in China, hydrogen pipeline enters the gas compartment can be expected soon. However, all the safety requirements of the gas compartment in the current standards are designed for natural gas, and the applicability for hydrogen is unknown. Therefore, a series of studies were started to investigate the safety of hydrogen in utility tunnel. In this work, a real utility tunnel locates at Shanghai was selected as the physical object. A 3D numerical model was built and successfully validated by a scaled tunnel test. The model has the maximum deviation of +9.5%. After that, a comparatively study of the dispersion behavior of CH4 and H2 was conducted. The assumed scenario was a 20 mm small-hole leaks with gauge pressure of 1.0 MPa in the middle of the tunnel. Numerical results shown that, H2 has a larger dispersion velocity and higher concentration, and is more dangerous compared to CH4. The current emergency ventilation strategy of air change rate of 12 times/h is not effective enough to dilute the H2 flammable cloud. The alarm time of the testing points shown strong linear law. There was a sharp variation in the range of 20%–100% LFL (Lower Flammable Limit), so the alarm strategy in the tunnel standards is too ideal for both CH4 and H2. The numerical results in the present study could provide a guidance for the design and safety management of the hydrogen tunnel. 相似文献
3.
《Ceramics International》2022,48(9):12281-12290
Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg3Gd2Ge3O12: Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO4] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs. 相似文献
4.
Jiao Zhang Junjie Li Ayesha Murtaza Aamir Iqbal Lijuan Zhu Shinawar Waseem Ali Muhammad Usman Roshan Yameen Siyi Pan Wanfeng Hu 《International Journal of Food Science & Technology》2022,57(2):963-973
This work evaluated the synergistic effects of combined high-intensity ultrasound (HIU) with β-cyclodextrin (β-CD) treatments on inhibiting browning of apple juice and explored the mechanism through simulation system. The combined treatment of 300 W HIU with 0.006 g mL−1 β-CD had a synergistic impact on maintaining juice colour, resulting in a 39.06% reduction in browning degree, only a 36.64% decrease in total phenolic content, and a 17.82% reduction in PPO activity. The inhibition of enzymatic browning in simulated system revealed that HIU suppressed the enzyme (Polyphenol oxidase, PPO) and β-CD inhibited enzyme (PPO) and embedded substrate (polyphenol). The results of spectroscopic analysis showed that the particle-size distribution of PPO narrowed, the content of α-helix in the secondary structure increased, the fluorescence intensity increased, and the maximum wavelength was red-shifted after HIU and β-CD treatment. Changes in structure could further result in PPO activity loss. Hence, the combined treatment could synthetically alleviate the browning of apple juice. 相似文献
5.
6.
7.
《International Journal of Hydrogen Energy》2022,47(57):24242-24253
As hydrogen refueling stations become increasingly common, it is clear that a high level of economic efficiency and safety is crucial to promoting their use. One way to reduce costs is to use a simple orifice instead of an excess flow valve, which Japanese safety regulations have identified as a safety device. However, there is concern about its effect on refueling time and on risk due to hydrogen leakage. To clarify the effect, we did a study of model-based refueling time evaluation and quantitative risk assessment for a typical refueling station. This study showed that an orifice is an effective alternative safety device. The increase in refueling time was less than 10%, based on simulations using a dynamic physical model of the station. Neither was there a significant difference in the risk between a configuration with excess flow valves and one with an orifice. 相似文献
8.
Hitoshi Muta 《Journal of Nuclear Science and Technology》2019,56(5):367-368
Recent activities in the field of Nuclear Operational Management and Nuclear Safety Engineering, the studies related to risk analysis methodology, design, and operational management, physical phenomena, and emergency preparedness and nuclear security, have been progressed. Especially, ‘risk analysis methodology’ and ‘design and operational management’ are the main categories of the field, in which more than half of published articles on Journal of Nuclear Science and Technology are related to these categories. 相似文献
9.
Guangbo Zeng Dongqing Zhang Liuming Yan Baohua Yue Ting Pan Yidong Hu Shufa He Hongbin Zhao Jiujun Zhang 《International Journal of Hydrogen Energy》2021,46(39):20664-20677
Side-chain optimized poly (2,6-dimethyl-1,4-phenylene oxide)-g-poly (styrene sulfonic acid) (PPO-g-PSSA) is designed with balanced water-resistance and sulfonation degree. The PPO-g-PSSA is synthesized by controlled atom-transfer radical polymerization (ATRP) from brominated poly (2,6-dimethyl-1,4-phenylene oxide) (PPO-xBr) and ethyl styrene-4-sulfonate and followed by hydrolysis. A series of PPO-g-PSSA are prepared possessing different bromination degree (x) of PPO-xBr and polymerization degree (m) of the side-chains and the water-resistances of the fabricated membranes are investigated. The results show that a PPO-g-PSSA at relatively low x (x < 0.2) and high m (m > 4) exhibits good balance between the water-resistance and the sulfonation degree. Namely, it displays suitable proton conductivity with compromised water-resistance. Moreover, a maximum ion exchange capacity (IEC) of 3.24 mmol g?1 is reached without the sacrifice of water-resistance. In addition, PPO-g-0.08PSSA-13 and PPO-g-0.14PSSA-4 are chosen characterized by thermogravimetric analysis, proton conductivities and mechanical properties. At 90% RH, the optimized PPO-g-0.08PPSA-13 possesses a proton conductivity of 37.9 mS cm?1 at 40 °C and 45.5 mS cm?1 at 95 °C, respectively. 相似文献
10.
Anh Tuan Thanh Pham Oanh Kieu Truong Le Dung Van Hoang Truong Huu Nguyen Trang Huyen Cao Pham Phuong Thanh Ngoc Vo Thang Bach Phan Vinh Cao Tran 《Journal of the European Ceramic Society》2021,41(6):3493-3500
Structure modification has been found to tune significantly the transparent-conducting performance, especially mobility and conductivity of hydrogenated Ga-doped ZnO (HGZO) films. The strong correlation between film thickness and mobility of the films is revealed. The mobility increases quickly with increasing the thickness from 350 to 900 nm, and then tends to be saturated at further thicknesses. A higher mobility than 50 cm2/Vs can be achieved, which is an extra-high value for polycrystalline ZnO films deposited by using the sputtering technique. The thickness-dependent mobility originates from scatterings on grain boundaries and dislocation-induced defects controlled by thin-film growth. Based on the Volmer-Weber model, an expansion model is built up to describe the thickness-dependent crystal growth of the HGZO films, especially at the thick films. As a result, the 800 nm-thick HGZO film obtains the highest performance with high mobility of 51.5 cm2/Vs, low resistivity of 5.3 × 10?4 Ωcm, and good transmittance of 83.3 %. 相似文献