全文获取类型
收费全文 | 332319篇 |
免费 | 25170篇 |
国内免费 | 12527篇 |
专业分类
电工技术 | 17902篇 |
技术理论 | 56篇 |
综合类 | 19712篇 |
化学工业 | 56619篇 |
金属工艺 | 18555篇 |
机械仪表 | 21196篇 |
建筑科学 | 25744篇 |
矿业工程 | 10978篇 |
能源动力 | 9776篇 |
轻工业 | 18733篇 |
水利工程 | 5264篇 |
石油天然气 | 22988篇 |
武器工业 | 2614篇 |
无线电 | 36666篇 |
一般工业技术 | 39817篇 |
冶金工业 | 18405篇 |
原子能技术 | 3229篇 |
自动化技术 | 41762篇 |
出版年
2024年 | 1291篇 |
2023年 | 5221篇 |
2022年 | 8890篇 |
2021年 | 12490篇 |
2020年 | 9833篇 |
2019年 | 8012篇 |
2018年 | 9214篇 |
2017年 | 10387篇 |
2016年 | 9292篇 |
2015年 | 12248篇 |
2014年 | 15891篇 |
2013年 | 19211篇 |
2012年 | 20208篇 |
2011年 | 22472篇 |
2010年 | 19229篇 |
2009年 | 18370篇 |
2008年 | 17995篇 |
2007年 | 17424篇 |
2006年 | 18299篇 |
2005年 | 16140篇 |
2004年 | 10361篇 |
2003年 | 9146篇 |
2002年 | 8142篇 |
2001年 | 7483篇 |
2000年 | 8011篇 |
1999年 | 9663篇 |
1998年 | 8166篇 |
1997年 | 6773篇 |
1996年 | 6366篇 |
1995年 | 5345篇 |
1994年 | 4382篇 |
1993年 | 3091篇 |
1992年 | 2493篇 |
1991年 | 1961篇 |
1990年 | 1505篇 |
1989年 | 1233篇 |
1988年 | 1020篇 |
1987年 | 682篇 |
1986年 | 535篇 |
1985年 | 342篇 |
1984年 | 243篇 |
1983年 | 206篇 |
1982年 | 196篇 |
1981年 | 129篇 |
1980年 | 130篇 |
1979年 | 67篇 |
1978年 | 33篇 |
1977年 | 38篇 |
1976年 | 55篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Dan Ye Kaiyu Wang Haijiao Yang Xingang Zhao 《International Journal of Adaptive Control and Signal Processing》2020,34(11):1677-1696
In this article, an adaptive fuzzy output feedback control method is presented for nonlinear time-delay systems with time-varying full state constraints and input saturation. To overcome the problem of time-varying constraints, the integral barrier Lyapunov functions (IBLFs) integrating with dynamic surface control (DSC) are applied for the first time to keep the state from violating constraints. The effects of unknown time delays can be removed by using designed Lyapunov-Krasovskii functions (LKFs). An auxiliary design system is introduced to solve the problem of input saturation. The unknown nonlinear functions are approximated by the fuzzy logic systems (FLS), and the unmeasured states are estimated by a designed fuzzy observer. The novel controller can guarantee that all signals remain semiglobally uniformly ultimately bounded and satisfactory tracking performance is achieved. Finally, two simulation examples illustrate the effectiveness of the presented control methods. 相似文献
82.
Chuntao Lan Haiyang Zou Longfei Wang Meng Zhang Shuang Pan Ying Ma Yiping Qiu Zhong Lin Wang Zhiqun Lin 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2005481
Despite recent rapid advances in metal halide perovskites for use in optoelectronics, the fundamental understanding of the electrical-poling-induced ion migration, accounting for many unusual attributes and thus performance in perovskite-based devices, remain comparatively elusive. Herein, the electrical-poling-promoted polarization potential is reported for rendering hybrid organic–inorganic perovskite photodetectors with high photocurrent and fast response time, displaying a tenfold enhancement in the photocurrent and a twofold decrease in the response time after an external electric field poling. First, a robust meniscus-assisted solution-printing strategy is employed to facilitate the oriented perovskite crystals over a large area. Subsequently, the electrical poling invokes the ion migration within perovskite crystals, thus inducing a polarization potential, as substantiated by the surface potential change assessed by Kelvin probe force microscopy. Such electrical-poling-induced polarization potential is responsible for the markedly enhanced photocurrent and largely shortened response time. This work presents new insights into the electrical-poling-triggered ion migration and, in turn, polarization potential as well as into the implication of the latter for optoelectronic devices with greater performance. As such, the utilization of ion-migration-produced polarization potential may represent an important endeavor toward a wide range of high-performance perovskite-based photodetectors, solar cells, transistors, scintillators, etc. 相似文献
83.
84.
World Wide Web - Infectious diseases such as Influenza and Ebola pose a serious threat to everyone but certain demographics and cohorts face a higher risk of infection than others. This research... 相似文献
85.
86.
87.
88.
89.
90.
Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong built-in electric field(BEF) in strained wurtzite Zn O/Mg0:25Zn0:75O quantum dots(QDs), the optical properties of ionized donor-bound excitons(D+, X)are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of(D+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of(D+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth. 相似文献