全文获取类型
收费全文 | 109384篇 |
免费 | 12175篇 |
国内免费 | 7922篇 |
专业分类
电工技术 | 9083篇 |
技术理论 | 6篇 |
综合类 | 10293篇 |
化学工业 | 15439篇 |
金属工艺 | 6594篇 |
机械仪表 | 7371篇 |
建筑科学 | 9072篇 |
矿业工程 | 3695篇 |
能源动力 | 3279篇 |
轻工业 | 11033篇 |
水利工程 | 2977篇 |
石油天然气 | 4229篇 |
武器工业 | 1328篇 |
无线电 | 12111篇 |
一般工业技术 | 10786篇 |
冶金工业 | 4287篇 |
原子能技术 | 1736篇 |
自动化技术 | 16162篇 |
出版年
2024年 | 658篇 |
2023年 | 2033篇 |
2022年 | 4216篇 |
2021年 | 5417篇 |
2020年 | 3957篇 |
2019年 | 3008篇 |
2018年 | 3210篇 |
2017年 | 3600篇 |
2016年 | 3261篇 |
2015年 | 4809篇 |
2014年 | 6031篇 |
2013年 | 7203篇 |
2012年 | 8452篇 |
2011年 | 8691篇 |
2010年 | 8126篇 |
2009年 | 7934篇 |
2008年 | 7800篇 |
2007年 | 7409篇 |
2006年 | 6771篇 |
2005年 | 5446篇 |
2004年 | 3984篇 |
2003年 | 2921篇 |
2002年 | 2898篇 |
2001年 | 2565篇 |
2000年 | 2185篇 |
1999年 | 1573篇 |
1998年 | 989篇 |
1997年 | 814篇 |
1996年 | 730篇 |
1995年 | 563篇 |
1994年 | 499篇 |
1993年 | 366篇 |
1992年 | 316篇 |
1991年 | 238篇 |
1990年 | 185篇 |
1989年 | 162篇 |
1988年 | 95篇 |
1987年 | 74篇 |
1986年 | 61篇 |
1985年 | 43篇 |
1984年 | 31篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 20篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1970年 | 2篇 |
1964年 | 2篇 |
1959年 | 13篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
3.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献
4.
围绕人工智能与智慧海洋建设这条主线,论述人工智能、智慧海洋的概念,列举当前较为成熟的人工智能与海洋科技在海洋观测方面融合的切入点,初步展现一种海洋技术与装备智能化的发展路径,提出加快人工智能技术向智慧海洋建设赋能的几点建议。 相似文献
5.
KH550, KH560, CTAB, and F127 were adopted to modify silicon (Si) to improve the dispersity and stability of Si in the polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO) polymer solutions. The influence of surfactants on rheological behaviors of PAN/DMSO/Si blending polymer solutions was investigated by an advanced solution and melt rotation rheometer. The homogeneity and stability were also studied. The results showed that the surfactants could change the viscosity dependence of blending polymer solutions on shear rate, temperature and storage time by increase the steric hindrance of Si. Among the four solutions, PAN/DMSO/Si blending polymer solution with F127 exhibited the lowest viscosity, activation energy and the smallest structural viscosity index and exhibited the trend close to the Newtonian fluids. Moreover, PAN/DMSO/Si blending polymer solution with F127 exhibited the best dispersity and stability, indicating its best physical properties and machinability. 相似文献
6.
目的建立超高效液相色谱-串联质谱法同时测定糕点中6种常用合成甜味剂的分析方法。方法选用超纯水作为提取溶剂,涡旋和超声提取后,低温离心,取部分上清液加入正己烷除脂,Waters Atlantis■T3色谱柱、甲醇-5 mmol/L甲酸铵(含0.1%甲酸)作为流动相、亲水亲脂平衡型固相萃取柱HLB(hydrophile-lipophile balance)净化。结果6种甜味剂在质量浓度为10~200 ng/mL的曲线范围内呈良好线性关系,相关系数r均大于0.999,平均加标回收率在85.0%-98.2%之间,相对平均偏差(relative standard deviation,RSD)为1.3%~6.7%。结论该方法具有前处理简单、灵敏度高、检测速度快等优点,适合糖精钠、甜蜜素、三氯蔗糖、阿斯巴甜、阿力甜、纽甜的检测,但不适用于安赛蜜的检测。 相似文献
7.
首都体育馆作为北京冬奥会的重要竞赛场馆,在改造过程中深入贯彻"绿色办奥"理念,采用二氧化碳制冰、LED照明、无障碍设施、新风系统、"海绵城市"等可持续性相关措施,为落成已经超过半个世纪的首都体育馆注入了新鲜的"绿色血液". 相似文献
8.
Developing the thermal stability of metal-based ceramic composites or their films has always been challenging and bottlenecks for the utilization of energy. In this paper, the novel mesh-like functional Al doped-MoO3 nanocomposite film with even distribution and high purity was firstly fabricated by the high-efficiency electrophoretic deposition and surface modification. The optimal suspension turned out to be the mixture of isopropanol and the additives of polyethyleneimine and benzoic acid. The microtopography, crystalline structure, environmental resistance and thermal stability were analyzed by field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), exposure and droplet-impacting test, DSC analysis and ignition test, respectively. The water contact angle and sliding angle of product can reach ~170° and <1°, indicating the excellent anti-wetting property. In addition, the high heat-release (~3180 J/g) of product all kept almost unchangeable after six months exposure experiments, demonstrating the outstanding thermostability. The exquisite design idea here can perfectly match microelectromechanical system (MEMS), providing the valuable reference for fabricating other metal-based high-energy composites with long lifespan for real industrial applications. 相似文献
9.
Qianying Hoo Xiaohu Wang Feng Yuan Xuewei Cao Tiewa Cao Maolin Zhang 《Journal of the European Ceramic Society》2021,41(6):3816-3822
Jingdezhen is famous for its bluish white (Qingbai) porcelains of the Song Dynasty, and those decorated with iron spots are distinctive among them. Herein, iron spots on a bluish white porcelain were investigated using a series of microscopic and spectroscopic characterizations. We found the decreasing iron content from more than 8 wt% to about 2 wt% during the glaze color transition from rusty to brown and finally into green, which built a connection on the coloring mechanism of iron-rich crystallized glaze and celadon glaze. We identified the rare ε-Fe2O3, a promising magnetic material, in both the dark brown crystals and the triangular crystals in the rusty area, which is its first discovery among bluish white porcelains. Based on these findings, we discussed the coloring mechanism of iron-spot decoration along with the physical form of the iron oxide crystals, indicating the partially reducing atmosphere during firing process. 相似文献
10.
Zhang Qi Wang Yujing Zhang Xueling Song Jun Li Yinlei Wu Xuehong Yuan Kunjie 《Journal of Materials Science》2022,57(14):7208-7224
Journal of Materials Science - Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after... 相似文献