全文获取类型
收费全文 | 47006篇 |
免费 | 5435篇 |
国内免费 | 3687篇 |
专业分类
电工技术 | 6157篇 |
综合类 | 4442篇 |
化学工业 | 8786篇 |
金属工艺 | 1582篇 |
机械仪表 | 1644篇 |
建筑科学 | 4940篇 |
矿业工程 | 2218篇 |
能源动力 | 1535篇 |
轻工业 | 6337篇 |
水利工程 | 2390篇 |
石油天然气 | 2060篇 |
武器工业 | 399篇 |
无线电 | 2013篇 |
一般工业技术 | 3941篇 |
冶金工业 | 1182篇 |
原子能技术 | 301篇 |
自动化技术 | 6201篇 |
出版年
2024年 | 320篇 |
2023年 | 1017篇 |
2022年 | 1700篇 |
2021年 | 1991篇 |
2020年 | 1915篇 |
2019年 | 1823篇 |
2018年 | 1641篇 |
2017年 | 1762篇 |
2016年 | 1905篇 |
2015年 | 1974篇 |
2014年 | 2687篇 |
2013年 | 3042篇 |
2012年 | 3121篇 |
2011年 | 3327篇 |
2010年 | 2445篇 |
2009年 | 2767篇 |
2008年 | 2486篇 |
2007年 | 2936篇 |
2006年 | 2605篇 |
2005年 | 2248篇 |
2004年 | 1922篇 |
2003年 | 1553篇 |
2002年 | 1290篇 |
2001年 | 1122篇 |
2000年 | 1028篇 |
1999年 | 968篇 |
1998年 | 775篇 |
1997年 | 655篇 |
1996年 | 584篇 |
1995年 | 479篇 |
1994年 | 429篇 |
1993年 | 344篇 |
1992年 | 334篇 |
1991年 | 214篇 |
1990年 | 139篇 |
1989年 | 122篇 |
1988年 | 82篇 |
1987年 | 63篇 |
1986年 | 47篇 |
1985年 | 30篇 |
1984年 | 48篇 |
1983年 | 37篇 |
1982年 | 38篇 |
1981年 | 14篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1955年 | 3篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Surface Energy and Surface Stability of Ag Nanocrystals at Elevated Temperatures and Their Dominance in Sublimation‐Induced Shape Evolution
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Long‐Bing He Lei Zhang Xiao‐Dong Tan Lu‐Ping Tang Tao Xu Yi‐Long Zhou Zhan‐Yong Ren Yun Wang Chun‐Yu Teng Li‐Tao Sun Jian‐Feng Nie 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(27)
The surface energy and surface stability of Ag nanocrystals (NCs) are under debate because the measurable values of the surface energy are very inconsistent, and the indices of the observed thermally stable surfaces are apparently in conflict. To clarify this issue, a transmission electron microscope is used to investigate these problems in situ with elaborately designed carbon‐shell‐capsulated Ag NCs. It is demonstrated that the {111} surfaces are still thermally stable at elevated temperatures, and the victory of the formation of {110} surfaces over {111} surfaces on the Ag NCs during sublimation is due to the special crystal geometry. It is found that the Ag NCs behave as quasiliquids during sublimation, and the cubic NCs represent a featured shape evolution, which is codetermined by both the wetting equilibrium at the Ag–C interface and the relaxation of the system surface energy. Small Ag NCs (≈10 nm) no longer maintain the wetting equilibrium observed in larger Ag NCs, and the crystal orientations of ultrafine Ag NCs (≈6 nm) can rotate to achieve further shape relaxation. Using sublimation kinetics, the mean surface energy of Ag NCs at 1073 K is calculated to be 1.1–1.3 J m?2. 相似文献
952.
Ji Chan Park Shin Wook Kang Jeong-Chul Kim Jae In Kwon Sanha Jang Geun Bae Rhim Mijong Kim Dong Hyun Chun Ho-Tae Lee Heon Jung Hyunjoon Song Jung-II Yang 《Nano Research》2017,(3):1044-1055
A cobalt-silica hybrid nanocatalyst bearing small cobalt particles of diameter ~5 nm was prepared through a hydrothermal reaction and hydrogen reduction.The resulting material showed very high CO conversion (>82%) and high hydrocarbon productivity (~1.0 gHc·g-1cat,·h-11) with high activity (~8.5 x 10-5 molco·g-1Co·S-1) in the Fischer-Tropsch synthesis reaction. 相似文献
953.
To attain the general form of stable coalition structure, this paper addressed the problem of retailers’ coalition stability in a two-stage supply chain consisting of one supplier and multiple retailers. A profit gain function was established via introducing market gain coefficient and coalition cost coefficient for different coalition structures. Based on the function, the profit of each retailer in all kinds of coalition structures was analysed, and the general feature of a stable coalition structure was attained by the largest consistent set method and the stable set method. Furthermore, some insights were obtained. For example, stable coalition structures are equidistributed or approximate equidistributed; with supplier’s cost increasing, the size of the retailers’ coalition increases. Finally, the above conclusions are verified by numerical simulation. The results of this paper provide a reference for retailers’ coalition in a supply chain, such as automobile or Information Technology supply chain. 相似文献
954.
A mobile ad hoc network (MANET) has abundant mobile nodes that are free to communicate independently in many locations. Many existing energy models address the inadequacy of resources based on Ad hoc On-demand Multipath Distance Vector and Optimized Link State Protocol (OLSP) routing protocols for MANET along with various parameters. The architecture of energy-efficient routing mechanisms is a challenging problem in a MANET. In this work, a novel energy-aware routing model is introduced for MANET comprising an ant colony optimization (ACO) enhanced approach to energy-efficient-optimized link state routing (named ACO–EEOLSR). Initially, the route discovery is progressed by means of neighbor estimation and also with the authentication of link stability. Parameters such as energy, distance, and hop count are employed as willingness nodes, where both the energy and distance are entrenched through the OLSP. Consequently, the hop count is applied via the ACO system that is beneficial for link stability. After the acceptance of an acknowledgement, the hop count is authorized for further performance analysis. This approach increases the Quality of Service and also uses less energy compared to other energy models. The accomplished simulation upshot depicts that the ACO–EEOLSR outperforms the EEOLSR scheme with respect to the performance metrics of energy consumption, packet delivery ratio, total remaining time, average network lifetime, and a variance of energy. 相似文献
955.
The seismic stability of the underground cavern complex, which houses the Baihetan hydropower plant in Yunnan Province, China, currently the world’s 2nd largest underground rock cavern group, is studied in this article. A preliminary performance-based seismic assessment approach specified for underground rock caverns is firstly proposed. The seismic performance objectives are classified. Reference earthquake motions are specified with the determination of the seismic variables. Detailed dynamic response analyses (Method 2B) are conducted based on the parameters given by the cyclic dynamic loading tests with medium strain rate. The seismic response of acceleration, stress, displacement and failure zones are studied. In addition, the seismic spectrum characteristics are analysed with a newly introduced wavelet packet technique. The mechanism of the support measures for seismic stability is also discussed. The assessment for seismic performance of the underground cavern complex is obtained by integrating these results. Serviceability objective of the underground cavern complex under operating basis earthquake may be satisfied, and the safety objective be feasible but with the presence of the proposed reinforcement system. The seismic isolation design is preferred, yet not necessary. And if any seismic isolation design is to be adopted, the frequency absorption range of the isolation material is expected to be 1–4 Hz. 相似文献
956.
Ousama Rachid F. Estelle R. Simons Mutasem Rawas-Qalaji Stephen Lewis Keith J. Simons 《Drug development and industrial pharmacy》2016,42(1):131-135
Context: Prompt injection of epinephrine (adrenaline) from epinephrine auto-injectors (EAIs) is the primary treatment for anaphylaxis in out-of-hospital settings. Storage of EAIs at room temperature (25?°C) is advised; however, storage at excessively high temperatures sometimes occurs. To our knowledge, there are no previous publications on the doses of epinephrine ejected from EAIs after storage at such temperatures.Objective: We examined the epinephrine doses delivered from activated EAIs stored constantly or cyclically at 70?°C.Methods: Twenty-five in-date EAIs were stored constantly or cyclically at 70?°C (excessive heat) or 25?°C (controls) for 5?d or 10?d. EAIs were activated and the epinephrine doses in the ejected solutions were measured using HPLC-UV. The enantiomeric purity of epinephrine was also measured by HPLC-UV.Results: Control EAIs ejected a volume of 0.300?±?0.006?mL containing 103.7?±?3.3% of labeled dose (LD). After 5?d or 10?d of constant storage at 70?°C and activation at 70?°C, EAIs ejected a volume of 0.367?±?0.008?mL containing 96.8?±?3.8% LD and 0.373?±?0.007?mL containing 77.7?±?3.3% LD, respectively. After 5?d of cyclic storage at 70?°C and cooling to 25?°C before activation, EAIs ejected a volume of 0.311?±?0.008?mL containing 87.2?±?1.9% LD. Under the experimental conditions of this study, the resultant chromatographic peaks of epinephrine solutions from all EAIs represented only the pure l-enantiomer of epinephrine.Conclusion: EAIs should be stored under recommended conditions of the manufacturer. EAIs stored at excessively high temperatures cannot be used to treat humans while still hot, and when cooled, cannot be relied on to deliver the labeled epinephrine dose in anaphylaxis. 相似文献
957.
958.
Enhancing Interfacial Bonding between Anisotropically Oriented Grains Using a Glue‐Nanofiller for Advanced Li‐Ion Battery Cathode
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
959.
960.
Simultaneous Near‐Infrared and Two‐Photon In Vivo Imaging of H2O2 Using a Ratiometric Fluorescent Probe based on the Unique Oxidative Rearrangement of Oxonium
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)