全文获取类型
收费全文 | 58374篇 |
免费 | 6137篇 |
国内免费 | 3641篇 |
专业分类
电工技术 | 3792篇 |
技术理论 | 1篇 |
综合类 | 4467篇 |
化学工业 | 9265篇 |
金属工艺 | 3269篇 |
机械仪表 | 3694篇 |
建筑科学 | 4109篇 |
矿业工程 | 1544篇 |
能源动力 | 1445篇 |
轻工业 | 6162篇 |
水利工程 | 1352篇 |
石油天然气 | 2301篇 |
武器工业 | 559篇 |
无线电 | 6933篇 |
一般工业技术 | 6931篇 |
冶金工业 | 2397篇 |
原子能技术 | 691篇 |
自动化技术 | 9240篇 |
出版年
2024年 | 321篇 |
2023年 | 965篇 |
2022年 | 1890篇 |
2021年 | 2461篇 |
2020年 | 1914篇 |
2019年 | 1655篇 |
2018年 | 1853篇 |
2017年 | 2012篇 |
2016年 | 1950篇 |
2015年 | 2587篇 |
2014年 | 3256篇 |
2013年 | 3995篇 |
2012年 | 4461篇 |
2011年 | 4875篇 |
2010年 | 4359篇 |
2009年 | 4268篇 |
2008年 | 4083篇 |
2007年 | 3821篇 |
2006年 | 3467篇 |
2005年 | 2882篇 |
2004年 | 2054篇 |
2003年 | 1614篇 |
2002年 | 1576篇 |
2001年 | 1337篇 |
2000年 | 969篇 |
1999年 | 763篇 |
1998年 | 523篇 |
1997年 | 404篇 |
1996年 | 357篇 |
1995年 | 261篇 |
1994年 | 224篇 |
1993年 | 193篇 |
1992年 | 137篇 |
1991年 | 123篇 |
1990年 | 81篇 |
1989年 | 72篇 |
1988年 | 55篇 |
1987年 | 43篇 |
1986年 | 41篇 |
1985年 | 25篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 30篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 20篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Supported metal catalysts, particularly noble metals supported on SiO2, have attracted considerable attention due to the importance of the silica–metal interface in heterogeneous catalysis and in electronic device fabrication. Several important issues, e.g., the stability of the metal–oxide interface at working temperatures and pressures, are not well-understood. In this review, the present status of our understanding of the metal–silica interface is reviewed. Recent results of model studies in our laboratories on Pd/SiO2/Mo(1 1 2) using LEED, AES and STM are reported. In this work, epitaxial, ultrathin, well-ordered SiO2 films were grown on a Mo(1 1 2) substrate to circumvent complications that frequently arise from the silica–silicon interface present in silica thin films grown on silicon. 相似文献
2.
A 0.9 V 92 dB Double-Sampled Switched-RC Delta-Sigma Audio ADC 总被引:1,自引:0,他引:1
Min Gyu Kim Gil-Cho Ahn Hanumolu P.K. Sang-Hyeon Lee Sang-Ho Kim Seung-Bin You Jae-Whui Kim Temes G.C. Un-Ku Moon 《Solid-State Circuits, IEEE Journal of》2008,43(5):1195-1206
A 0.9 V third-order double-sampled delta-sigma audio ADC is presented. A new method using a combination of a switched-RC technique and a floating switched-capacitor double-sampling configuration enabled low-voltage operation without clock boosting or bootstrapping. A three-level quantizer with simple dynamic element matching was used to improve linearity. The prototype IC implemented in a 0.13 CMOS process achieves 92 dB DR, 91 dB SNR and 89 dB SNDR in a 24 kHz audio signal bandwidth, while consuming 1.5 mW from a 0.9 V supply. The prototype operates from 0.65 V to 1.5 V supply with minimal performance degradation. 相似文献
3.
Min Chan Kim Dong Won Lee Chang Kyun Choi 《Korean Journal of Chemical Engineering》2008,25(6):1239-1244
When a horizontal homogeneous solid is melted from below, convection can be induced in a thermally unstable melt layer. In
this study the onset of buoyancy-driven convection during time-dependent melting is investigated by using similarly transformed
disturbance equations. The critical Rayleigh numbers based on the melt-layer thickness are found numerically for various conditions.
For small superheats, the present predictions approach the well known results of classical Rayleigh-Bénard problems, that
is, critical Rayleigh numbers are located between 1,296 and 1,708, regardless of the Prandtl number. However, for high superheats
the critical Rayleigh number increases with an increase in phase change rate but with decrease in Prandtl number. 相似文献
4.
Takeshi Kondo Sang Min Lee Michal Malicki Benoit Domercq Seth R. Marder Bernard Kippelen 《Advanced functional materials》2008,18(7):1112-1118
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs. 相似文献
5.
Cheol-Min Park Byung-Hyuk Min Jae-Hong Jun Juhn-Suk Yoo Min-Koo Han 《Electron Device Letters, IEEE》1997,18(1):16-18
We have fabricated a self-aligned offset-gated poly-Si thin film transistor (TFT) by employing a novel photoresist reflow process. The gate structure of the new device is consisted of two unique patterns: A main-gate and a sub-gate. The new fabrication method extends the gate-oxide over the offset region. With the assistance of the sub-gate and reflowed photoresist a self-aligned offset region is successfully obtained due to the offset oxide acting as an implantation mask. The poly-Si TFT with symmetrical offsets is easily fabricated and the new method does not require any additional offset mask step. Compared with the misaligned offset gated poly-Si TFTs, excellent symmetric electrical characteristics are obtained 相似文献
6.
KS Min AR Khan MK Kwon YJ Jung Z Yun Y Kiso 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(8):909-915
The performance of a laboratory‐scale anaerobic acidogenic fermenter fed with a mixture of blended kitchen food‐waste and primary sludge from a sewage treatment plant was investigated for the production of volatile fatty acids (VFA). The operating variables for acidogenic fermentation were kitchen food‐waste content (10 and 25 wt %), hydraulic retention time (HRT: 1, 3 and 5 days), temperature (ambient: 18 ± 2 °C, and mesophilic: 35 ± 2 °C) and pH (varied from 5.2 to 6.7). The experimental results indicated that effluent VFA concentrations and VFA production rates were higher at ambient temperature than at mesophilic conditions. The net amount of VFA with 10 wt % food‐waste increased up to 920 mg dm?3 with an increase of HRT, but contrasting results (a decrease of 2610 mg dm?3) were found due to the conversion of VFA into biogas in the case of 25 wt % food‐waste, which increased significantly at HRT of 3–5 days. In terms of biogas composition (CO2 and CH4), the organic matter was converted into CO2 through the oxidative pathway by facultative species at low temperature while mesophilic temperature and optimum pH (6.3–7.8) played a pivotal role in increasing rate of conversion of VFA into biogas by methanogenesis. Rates of VFA production and their conversion are dependent on the food‐waste content in the mixture. Yet, the higher concentration of food‐waste (25% compared with 10%) did not produce VFA proportionally due to the increased rate of conversion of VFA into gaseous products. The maximum VFA production rate (0.318 g VFAproduced g?1 VSfed day?1) was achieved in the 10 wt % food‐waste at ambient temperature and at a 5‐day HRT. Copyright © 2005 Society of Chemical Industry 相似文献
7.
V. S. Bessmertnyi N. I. Min’ko P. S. Dyumina V. P. Krokhin S. V. Semenenko M. A. Lipko 《Glass and Ceramics》2005,62(11-12):386-387
A technology for the synthesis of synthetic minerals (using the example of spinels) using a low-temperature plasma flame is developed. The diagnostic properties of spinels are identified. 相似文献
8.
实验研究了水辐射分解作用对高放废物深地质处置容器材料的影响。在高放废物深地质处置库附近的地下水,受辐射线作用后分解出氧、氢和氧化产物(例如H_2O_2等),于是在高放废物容器周围形成一个氧化场,导致高放废物中的某些重要放射性核素(例如U,Np和Tc)易溶于水,并向远域迁移。本实验中的含FeSO_4(0.13 mol/L)水溶液在吸收剂量为0、20、60、180、500kGy的射线作用下,其氧化还原电位(Eh)值由+357mV增至+414 mV;在不同吸收剂量的射线作用下,金属Cu、金属Al、0.357 mv金属Fe和不锈钢(后者是我国拟采用的高放废物包装容器材料),在水溶液中的氧化侵蚀强度,分别比在无辐射情况下的大0.2-6.1倍。 相似文献
9.
国际乳业的热点论题:蛋白质标准化 总被引:1,自引:0,他引:1
介绍了蛋白质的标准化这一国际乳品界正热的研究和讨论题目,综述了蛋白质标准化的必要性和世界上目前采用的方法,展望了膜技术在蛋白质标准化上的应用前景。 相似文献
10.
地基设计是整个建(构)筑物设计中的重要组成部分,它关系到建(构)筑物的安全及其功能能否正常发挥。本文着重分析探讨了在地基设计中应遵循的原则及注意事项。以保证建(构)筑物的安全和正常使用,充分发挥地基的作用。 相似文献