全文获取类型
收费全文 | 20758篇 |
免费 | 1478篇 |
国内免费 | 673篇 |
专业分类
电工技术 | 977篇 |
技术理论 | 3篇 |
综合类 | 1240篇 |
化学工业 | 3725篇 |
金属工艺 | 994篇 |
机械仪表 | 1259篇 |
建筑科学 | 1602篇 |
矿业工程 | 431篇 |
能源动力 | 552篇 |
轻工业 | 1456篇 |
水利工程 | 329篇 |
石油天然气 | 1057篇 |
武器工业 | 153篇 |
无线电 | 2177篇 |
一般工业技术 | 3060篇 |
冶金工业 | 1157篇 |
原子能技术 | 248篇 |
自动化技术 | 2489篇 |
出版年
2024年 | 73篇 |
2023年 | 281篇 |
2022年 | 441篇 |
2021年 | 583篇 |
2020年 | 488篇 |
2019年 | 446篇 |
2018年 | 465篇 |
2017年 | 591篇 |
2016年 | 530篇 |
2015年 | 698篇 |
2014年 | 837篇 |
2013年 | 1093篇 |
2012年 | 1160篇 |
2011年 | 1244篇 |
2010年 | 1059篇 |
2009年 | 1028篇 |
2008年 | 1097篇 |
2007年 | 1048篇 |
2006年 | 1135篇 |
2005年 | 1103篇 |
2004年 | 692篇 |
2003年 | 652篇 |
2002年 | 604篇 |
2001年 | 522篇 |
2000年 | 672篇 |
1999年 | 725篇 |
1998年 | 626篇 |
1997年 | 553篇 |
1996年 | 490篇 |
1995年 | 456篇 |
1994年 | 333篇 |
1993年 | 248篇 |
1992年 | 208篇 |
1991年 | 169篇 |
1990年 | 133篇 |
1989年 | 116篇 |
1988年 | 90篇 |
1987年 | 44篇 |
1986年 | 48篇 |
1985年 | 43篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
半导体激光线阵(LDB)在制作和封装过程中会发生弯曲,从而引起发光弯曲,即"smile",这影响其在抽运固体激光和外腔半导体激光阵列线宽窄化中的使用.利用平凸柱面镜在一定程度上可矫正半导体激光线阵的"smile".通过几何光学方法对平凸柱面镜矫正半导体激光线阵的"smile"进行理论分析,利用不同焦距平凸柱面镜对不同半导体激光线阵的"smile"进行矫正,并通过ORIGIN软件对"smile"的矫正进行模拟,其结果与实验相吻合.结果显示,抛物线状"smile"矫正效果很好,相对矫正量高达90%,选择合适小焦距平凸柱面镜对"smile"矫正较明显且模拟误差小,修正透镜焦距参数可减小误差. 相似文献
172.
提出了一种用SMIC 0.18μm CMOS混合信号工艺实现的全集成CMOS微阵列生物芯片,并成功地实现了其与一种新的生物纳米系统的集成. 该电路实现了19μm×19μm电极的4×4 (16单元)阵列,反相电极,电流模式放大器,译码电路,以及逻辑控制电路的单片集成,并能够提供-1.6~1.6V的组装电压,8bit的电位分辨率及39.8dB的电流增益,电源电压为1.8V,而失调和噪声电流分别为5.9nA和25.3pArms. 在实验中,利用该电路实现了对30nm聚乙烯醇包裹的磁性粒子的片上选择性组装,并对实验结果进行了讨论,从而验证了该电路的正确性和该集成方法的可行性. 相似文献
173.
使用Levenberg-Marquardt训练函数的神经网络算法在复合材料板上进行声发射定位,采用声波到达时间作为输入向量,训练得到了到达各个传感器的声波触发时间与板上坐标的良好的映射关系。考虑到波形衰减,用传统的固定门槛提取的到达时间容易与实际情况偏差较大,讨论了一种相对准确的适合工程使用的到达时间提取方法。 相似文献
174.
175.
We theoretically predict the appearance of a persistent charge current in a Rashba ring with a normal and a ferromagnetic lead under no external bias. This charge current is the result of the breaking of the time inversion symmetry in the original persistent pure spin current induced by the Rashba spin-orbit coupling (RSOC) in the ring due to the existence of the ferromagnetic lead. With the Keldysh Green''s function technique, we find that not only the magnitude and sign but also the spin polarization of the generated charge current is determined by the system parameters such as the magnetization direction of the ferromagnetic lead, the tunneling coefficient, the strength of the RSOC and the exchange energy of the ferromagnetic lead, which are all tunable in experiments, that is, a controllable persistent spin-polarized charge current can be obtained in such a device. 相似文献
176.
177.
Yujie Chen Johannes Herrnsdorf Benoit Guilhabert Yanfeng Zhang Alexander L. Kanibolotsky Peter J. Skabara Erdan Gu Nicolas Laurand Martin D. Dawson 《Organic Electronics》2012,13(7):1129-1135
Control of the emission wavelength of a random laser (RL) system over a 7-nm waveband is demonstrated using a green-emitting π-conjugated polymer infiltrated into a photonic glass formed by nano/micro-size monodisperse silica spheres. The use of a solution-based conjugated polymer enables the complete filling of the voids within the photonic glass without suffering from quenching and the gain can therefore be maximized. The emission wavelength of these structures is set by a combination of the material system spectral gain and of the transport mean free path, the latter being controlled by the mean diameter of the spheres in the nano-scale range. Transport mean free paths of photons in the RL’s active region are calculated using Mie scattering theory and corroborated with coherent backscattering measurements. Further wavelength modification is also possible by changing the pump spot size and the pump fluence. 相似文献
178.
Ruxing Fu Hongjun Li Ruoxin Li Kyle McGrath Gianpietro Dotti Zhen Gu 《Advanced functional materials》2021,31(44):2009489
Chimeric antigen receptor (CAR) T cells exhibit promising results for cancer immunotherapy. However, the clinical success is still restricted to certain types of blood cancers, while in solid tumors the clinical activity is modest and potential toxicities remain a concern. There are various barriers that prevent CAR T cells from combating solid tumors. Therefore, distinct strategies have been explored to augment CAR T cell proliferative capacity, persistence, and effector function. Altering the tumor microenvironment, and in particular its physiochemical properties and immunosuppressive milieu, is of great significance to facilitate CAR T cell therapy. In this article, emerging strategies implemented to overcome the barriers of CAR T cell therapy in solid tumors are reviewed. Enhancing infiltration, activation, and persistence of CAR T cells has been addressed in several preclinical models. The future development of this field to promote innovation and clinical translation is also discussed. 相似文献
179.
Bin Liu Xinquan Gu Qiannan Sun Shengjie Jiang Jing Sun Kai Liu Fan Wang Yan Wei 《Advanced functional materials》2021,31(19):2010779
Malignant bone tumors are often accompanied by osteolytic destruction and severe pathological fractures. Current therapeutic strategies can largely inhibit tumor proliferation, but the high recurrence rate of tumors and related bone defects remain a significant challenge. This study aims to address these issues by developing a novel near-infrared (NIR) light-responsive and a mechanically strong hydrogel that offers excellent photothermal tumor therapy and bone fracture repair capabilities. The as-prepared hydrogel exhibits good biocompatibility and an ultra-strong photothermal effect due to the formation of a complex network with up-conversion lanthanide-Au hybrid nanoparticles and alginate molecules. A subcutaneous tumor model is used to demonstrate that tumors can be efficiently eradicated via local photothermal treatment, where there is no tumor recurrence within the observation period. Moreover, the injected hydrogel becomes mechanically strong due to in situ Ca2+ crosslinking, which provides a supportive matrix to promote the repair of bone defects via stabilization of the fractured bone structure. The high photothermal effect and robust support offered by this single material demonstrate the potential of using the proposed hydrogel for the simultaneous treatment of bone tumor removal and bone healing. 相似文献
180.
Xiaoxia Ma Shuai Gu Yuxiang Li Jian Lu Guangcheng Yang Kaili Zhang 《Advanced functional materials》2021,31(42):2103199
Transient microchips have promising applications in data security and privacy protection. A simple fabrication process and short transient time are two crucial requirements for transient microchips. In this study, a facile drop-casting method is used to develop a transient microchip based on an energetic film and a microheater on a substrate. It is found that the graphene oxide-energetic coordination polymer composite based energetic film plays an important role in simplifying the fabrication process and achieving fast transient time due to its inherent film forming ability, strong binding to substrate, and highly energetic characteristics. The interlayer confinement effect of graphene oxide (GO) can significantly reduce the size of energetic coordination polymer (ECP) to nanometer scale. Van der Waals forces between GO layers and coordination bonds between GO and metal ions are responsible for the film formation ability. Furthermore, the reduction of ECP size and the compact stacking lay the foundation for the excellent combustion and pressure production performance of the energetic film. The strong adhesion of the energetic film and the substrate is confirmed by drop experiments. More importantly, the fabricated silicon based transient microchip can achieve self-destruction within 1 second. 相似文献