全文获取类型
收费全文 | 150385篇 |
免费 | 13163篇 |
国内免费 | 6818篇 |
专业分类
电工技术 | 9117篇 |
技术理论 | 4篇 |
综合类 | 9753篇 |
化学工业 | 23956篇 |
金属工艺 | 8508篇 |
机械仪表 | 9182篇 |
建筑科学 | 11199篇 |
矿业工程 | 3903篇 |
能源动力 | 4256篇 |
轻工业 | 10744篇 |
水利工程 | 2841篇 |
石油天然气 | 7577篇 |
武器工业 | 1185篇 |
无线电 | 19255篇 |
一般工业技术 | 18786篇 |
冶金工业 | 7345篇 |
原子能技术 | 1644篇 |
自动化技术 | 21111篇 |
出版年
2024年 | 575篇 |
2023年 | 2274篇 |
2022年 | 3993篇 |
2021年 | 5932篇 |
2020年 | 4243篇 |
2019年 | 3659篇 |
2018年 | 4102篇 |
2017年 | 4684篇 |
2016年 | 4211篇 |
2015年 | 5690篇 |
2014年 | 7265篇 |
2013年 | 9109篇 |
2012年 | 9944篇 |
2011年 | 11041篇 |
2010年 | 9415篇 |
2009年 | 9061篇 |
2008年 | 8862篇 |
2007年 | 8540篇 |
2006年 | 8683篇 |
2005年 | 7124篇 |
2004年 | 4913篇 |
2003年 | 4089篇 |
2002年 | 3916篇 |
2001年 | 3421篇 |
2000年 | 3426篇 |
1999年 | 3595篇 |
1998年 | 3287篇 |
1997年 | 2797篇 |
1996年 | 2517篇 |
1995年 | 2104篇 |
1994年 | 1721篇 |
1993年 | 1306篇 |
1992年 | 1014篇 |
1991年 | 812篇 |
1990年 | 627篇 |
1989年 | 504篇 |
1988年 | 424篇 |
1987年 | 282篇 |
1986年 | 238篇 |
1985年 | 188篇 |
1984年 | 120篇 |
1983年 | 84篇 |
1982年 | 90篇 |
1981年 | 74篇 |
1980年 | 72篇 |
1979年 | 45篇 |
1978年 | 38篇 |
1977年 | 37篇 |
1976年 | 68篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
121.
The in-situ fabrication of an electron-blocking layer between the Ba-containing anode and the ceria-based electrolyte is an effective approach in suppressing the internal electronic leakage in ceria-based solid oxide fuel cell (SOFC). To improve the thickness of the electron-blocking layer and to research the effect of the layer thickness on the improvement of SOFC, a Ba-containing compound (0.6NiO-0.4BaZr0.1Ce0.7Y0.2O3-δ) modified by Y stabilized zirconia (YSZ) was employed as a composite anode in this research. SEM analyses demonstrated that the thickness of the interlayer can be simply controlled by regulating the proportion of YSZ at anode. The in-situ formed interlayer in the cell with the anode modified by 20?mol% YSZ possesses a thickness of 0.9?µm which is more suitable for the cell achieving an enhanced performance. 相似文献
122.
Wenyun Yang Qiwei Hu Guanyi Qiao Liang Zha Shunquan Liu Jingzhi Han Honglin Du Yan Zhang Yingchang Yang Changsheng Wang 《中国稀土学报(英文版)》2019,37(10):1102-1107
In this work, we report the tuning effect of the Si substitution on the magnetic and high frequency electromagnetic properties of R2Fe17 compounds and their paraffin composites. It is found that the introduction of Si can remarkably improve the magnetic and electromagnetic properties of the R2Fe17 compounds, making the R2Fe17–xSix-paraffin composites excellent microwave absorption materials (MAMs). By introducing the Si element, their saturation magnetizations decrease slightly, while much higher Curie temperatures are obtained. Furthermore, better impedance match is reached due to the decrease of the high-frequency permittivity ε′ by about 40%–50%, which finally enhances the performance of the microwave absorption. The peak frequency (fRL) of the reflection loss (RL) curve moves toward high frequency domain and the qualified bandwidth (QB, RL ≤ ?10 dB) increases remarkably. The maximum QB of 3.3 GHz (12.0–15.3 GHz) is obtained for the Sm1.5Y0.5Fe15Si2-paraffin composite (d = 1.0 mm) and the maximum RL of ?53.6 dB is achieved for Nd2Fe15Si2-paraffin composite (d = 2.2 mm), both surpassing most of the reported MAMs. Additionally, a distinguished dielectric microwave absorption peak is observed, which further increases the QB in these composites. 相似文献
123.
124.
125.
Lin Gao Stefano Selleri Giorgio Battistelli Luigi Chisci Giuseppe Pelosi 《国际射频与微波计算机辅助工程杂志》2020,30(9)
This paper presents a novel approach to the localization of moving targets in a complex environment based on the measurement of the perturbations induced by the target presence on an independently‐generated time‐varying electromagnetic field. Field perturbations are measured via a set of sensors deployed over the domain of interest and used to detect and track a possible target by resorting to a particle Bernoulli filter (PBF). To comply with real‐time operation, the PBF works along with an artificial neural network (ANN) model of the environment trained offline via finite elements (FEs). The performance of the proposed algorithm is assessed via simulation experiments. 相似文献
126.
Yang Yang Yibei Zhou Juan Ren Qiaoji Zheng Kwok Ho Lam Dunmin Lin 《Journal of the European Ceramic Society》2018,38(2):557-566
Perovskite ferroelectrics possess the fascinating piezoelectric properties near a morphotropic phase boundary, attributing to a low energy barrier that the results in structural instability and easy polarization rotation. In this work, a new lead-free system of (1-x)BaTiO3-xCaHfO3 was designed, and characterized by a coexistence of ferroelectric rhombohedral-orthorhombic-tetragonal (R-O-T) phases. With the increase amount of CaHfO3 (x), a stable coexistence region of three ferroelectric phases (R-O-T) exists at 0.06 ≤ x ≤ 0.08. Both large piezoelectric coefficient (d33~400 pC/N), inverse piezoelectric coefficient (d33*~547 pm/V) and planar electromechanical coupling factor (kp~58.2%) can be achieved for the composition with x = 0.08 near the coexistence of three ferroelectric phases. Our results show that the materials with the composition located at a region where the three ferroelectric R-O-T phases coexist would have the lowest energy barrier and thus greatly promote the polarization rotation, resulting in a strong piezoelectric response. 相似文献
127.
Machine Learning - Recently, the $${ Tensor}~{ Nuclear}~{ Norm}~{ (TNN)}$$ regularization based on t-SVD has been widely used in various low tubal-rank tensor recovery tasks. However, these models... 相似文献
128.
针对目标探测类空间红外相机大范围成像、高灵敏度探测、高精度定位等应用需求,文中提出采用像方远心光路和低温光学技术结合的解决方案,设计了物方视场角8°×8°、入瞳口径265 mm、工作温度200 K的像方远心折射式光学系统。镜头最大口径280 mm,采用多级分散的弹性支撑设计,解决大口径低温透镜装框、透镜组件支撑和镜头整体安装各环节的热应力卸载问题。在保证高刚度和低漏热的情况下,使低温下透镜的热应力对镜头能量集中度的影响降低到可接受范围内。镜头完成装调及室温下像质确认后,进行了力学振动试验,并将其制冷到200 K水平测试像质,测试结果表明,镜头能量集中度达到轴上75%,边缘视场72%。 相似文献
129.
Locke Davenport Huyer Serena Mandla Yufeng Wang Scott B. Campbell Bess Yee Christian Euler Benjamin F. Lai A. Dawn Bannerman Dawn S. Y. Lin Miles Montgomery Kayla Nemr Timothy Bender Slava Epelman Radhakrishnan Mahadevan Milica Radisic 《Advanced functional materials》2021,31(6):2003341
Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA. 相似文献
130.
Yingchao Hu Wenqiang Liu Yuandong Yang Xianliang Tong Qianjun Chen Zijian Zhou 《Ceramics International》2018,44(14):16668-16677
Li4SiO4 sorbents for high-temperature CO2 removal have drawn extensive attention owing to their potential application in carbon capture and storage (CCS). The major challenge in the application lies in the poor CO2 capture performance under realistic conditions of low CO2 concentrations, owing to the dense structure and poor porosity. In this work, Li4SiO4 sorbents were prepared with porous micromorphologies and large contact areas using a variety of organometallic Li-precursors, achieving fast CO2 sorption kinetics, high capacity and excellent cyclic stability at a low CO2 concentration (15?vol%). It was found that a high conversion of ~?74% was maintained for pure Li4SiO4 even after 100 sorption/desorption cycles. Moreover, by doping with Na2CO3 to reduce the CO2 diffusion resistance, the conversion of the sorbent was further enhanced to 93.2%. The enhancement mechanism of alkali carbonate have been proven here to be ascribed to the formation of the eutectic melt of Li/Na carbonates, the existence and function of which has been confirmed in this study. 相似文献