全文获取类型
收费全文 | 110226篇 |
免费 | 13012篇 |
国内免费 | 7170篇 |
学科分类
工业技术 | 130408篇 |
出版年
2024年 | 515篇 |
2023年 | 2273篇 |
2022年 | 4556篇 |
2021年 | 6228篇 |
2020年 | 4448篇 |
2019年 | 3557篇 |
2018年 | 3847篇 |
2017年 | 3987篇 |
2016年 | 3456篇 |
2015年 | 5286篇 |
2014年 | 6366篇 |
2013年 | 7091篇 |
2012年 | 8516篇 |
2011年 | 8723篇 |
2010年 | 7794篇 |
2009年 | 7289篇 |
2008年 | 7039篇 |
2007年 | 6501篇 |
2006年 | 5802篇 |
2005年 | 4748篇 |
2004年 | 3589篇 |
2003年 | 3469篇 |
2002年 | 3870篇 |
2001年 | 3362篇 |
2000年 | 2155篇 |
1999年 | 1538篇 |
1998年 | 891篇 |
1997年 | 732篇 |
1996年 | 599篇 |
1995年 | 484篇 |
1994年 | 379篇 |
1993年 | 344篇 |
1992年 | 237篇 |
1991年 | 150篇 |
1990年 | 121篇 |
1989年 | 93篇 |
1988年 | 89篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 27篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 33篇 |
1979年 | 19篇 |
1978年 | 1篇 |
1959年 | 12篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Feng Wenran Li Zhen Chen Yingying Chen Jinyang Lang Haoze Wan Jianghong Gao Yan Dong Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in... 相似文献
2.
3.
4.
5.
Xin Li Yurui Wang Minxuan Xu Yueqin Shi Hemiao Wang Xin Yang Haoting Ying Qi Zhang 《应用聚合物科学杂志》2021,138(19):50406
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field. 相似文献
7.
大气波导干扰是特定气象条件下发生的时分双工(time-division duplex,TDD)系统内干扰,是TDD移动通信系统大规模组网面临的顽疾。在总结分析大气波导干扰成因和分类等的基础上,对大气波导干扰进行建模和表征,验证了海量干扰源在时域和频域的功率集总特征,并结合大量4G/5G现网实测数据给出了典型条件下内陆波导和海面波导的量化干扰信号传播模型,对于干扰的预测和预防具有重要意义。基于干扰特征,给出了TDD系统预防大气波导干扰的帧结构与组网的4项设计原则,5G现网数据表明干扰控制方案有效,上行干扰下降10 dB以上,相关原则对于6G系统的设计也具有指导意义。 相似文献
8.
在医疗卫生、金融证券等应用领域,经常会同时出现零观测值、一观测值较多的情况. 为更好地拟合这类数据,提出0–1膨胀几何分布模型并进行客观贝叶斯分析. 通过参数变换,得到Jeffreys先验和reference先验. 设计后验分布的抽样算法,设置不同的样本量和参数真值,采用数值模拟方法对不同客观先验下的估计效果进行评估. 相似文献
9.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献
10.
Zhen Hong Mingshan Xue Yidan Luo Zuozhu Yin Chan Xie Junfei Ou Fajun Wang 《应用聚合物科学杂志》2021,138(2):49657
With the continuous development of bionics, such as, geckos and virginia creeper with both superhydrophobic and super-adhesive, the surface wetting and super-adhesive properties of various porous materials have attracted extensive attention of the scientific and medical communities. Here, the honeycomb polyurethane (PU) porous films with strong adhesion were successfully prepared by microphase separation method and the effects of growth parameters on their microstructure and adhesive strength to ice were investigated. It was found that a high relative humidity (e.g., 100%) and a low solution concentration (e.g., 2%) facilitated the formation of ordered honeycomb PU porous films, and as-prepared PU pores with average pore diameter as small as 5 μm are better ordered and more uniform than these in related documents. Although the contact angle of water droplets on the surface of PU porous films increased from the premodification value of 85–130° to more than 160° after surface modification with polydopamine (PDA), the corresponding rolling angle remained approximately constant (180°), indicating that the surface of PU porous films has strong adhesion similar to geckos and virginia creeper. Furthermore, at lower temperature, the PU porous films exhibited the high adhesive strength of 142.13 kPa on ice, which was strongly dependent on the porous microstructures and surface compositions. The improved adhesive behavior to ice of honeycomb PU porous films modified with PDA provides new strategies for surface modification of materials and potential applications in medical domain. 相似文献