全文获取类型
收费全文 | 282994篇 |
免费 | 79470篇 |
国内免费 | 53581篇 |
专业分类
电工技术 | 35894篇 |
技术理论 | 3篇 |
综合类 | 31801篇 |
化学工业 | 36419篇 |
金属工艺 | 31836篇 |
机械仪表 | 13663篇 |
建筑科学 | 19644篇 |
矿业工程 | 17247篇 |
能源动力 | 10789篇 |
轻工业 | 30145篇 |
水利工程 | 10168篇 |
石油天然气 | 16841篇 |
武器工业 | 5180篇 |
无线电 | 39894篇 |
一般工业技术 | 38136篇 |
冶金工业 | 10609篇 |
原子能技术 | 3022篇 |
自动化技术 | 64754篇 |
出版年
2024年 | 2973篇 |
2023年 | 6132篇 |
2022年 | 9016篇 |
2021年 | 10975篇 |
2020年 | 12353篇 |
2019年 | 20079篇 |
2018年 | 21665篇 |
2017年 | 23368篇 |
2016年 | 22565篇 |
2015年 | 23463篇 |
2014年 | 23282篇 |
2013年 | 23493篇 |
2012年 | 24704篇 |
2011年 | 21573篇 |
2010年 | 19914篇 |
2009年 | 16304篇 |
2008年 | 14680篇 |
2007年 | 13782篇 |
2006年 | 11787篇 |
2005年 | 10146篇 |
2004年 | 11370篇 |
2003年 | 8840篇 |
2002年 | 8410篇 |
2001年 | 7424篇 |
2000年 | 6661篇 |
1999年 | 5625篇 |
1998年 | 4650篇 |
1997年 | 4055篇 |
1996年 | 3896篇 |
1995年 | 3864篇 |
1994年 | 3198篇 |
1993年 | 2888篇 |
1992年 | 2796篇 |
1991年 | 2033篇 |
1990年 | 1585篇 |
1989年 | 1460篇 |
1988年 | 1119篇 |
1987年 | 360篇 |
1986年 | 320篇 |
1985年 | 238篇 |
1984年 | 171篇 |
1983年 | 130篇 |
1982年 | 169篇 |
1981年 | 178篇 |
1980年 | 138篇 |
1976年 | 233篇 |
1975年 | 210篇 |
1972年 | 239篇 |
1971年 | 132篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
Yan Jing Zhu Rongying Wu Fan Zhao Ziyin Ye Huan Hou Mengying Liu Yong Yin Lichen 《Nano Research》2020,13(10):2706-2715
Nano Research - Insufficient intratumoral penetration greatly hurdles the anticancer performance of nanomedicine. To realize highly efficient tumor penetration in a precisely and spatiotemporally... 相似文献
34.
在新型二次电池产业的发展中,氢镍电池市场不断萎缩,锂离子电池市场正处于黄金时代。通过对日本和中国新型二次电池产业发展历程分析,我国主要针对低端市场,高端市场为日本占据,并从日本发展经验中提出了可供我国锂离子电动车电池发展的借鉴之处。 相似文献
35.
Jie-Long He An-Te Chen Jyong-Huei Lee Shih-Kang Fan 《International journal of molecular sciences》2015,16(9):22319-22332
The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed. 相似文献
36.
37.
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
38.
针对基站柜式空调耗电量大的问题,创造性地使用基站分布式冷却的方式,达到精确送风,节能高效的目的.在应用实践中检验了分布式冷却系统实际节能量和应用效果,总结出分布式冷却系统应用场景和范围,为更大范围推广应用DCS分布式冷却系统提供实践依据. 相似文献
39.
We investigate the effect of dopant random fluctuation on threshold voltage and drain current variation in a two-gate nanoscale transistor. We used a quantum-corrected technology computer aided design simulation to run the simulation (10000 randomizations). With this simulation, we could study the effects of varying the dimensions (length and width), and thicknesses of oxide and dopant factors of a transistor on the threshold voltage and drain current in subthreshold region (off) and overthreshold (on). It was found that in the subthreshold region the variability of the drain current and threshold voltage is relatively fixed while in the overthreshold region the variability of the threshold voltage and drain current decreases remarkably, despite the slight reduction of gate voltage diffusion (compared with that of the subthreshold). These results have been interpreted by using previously reported models for threshold current variability, load displacement, and simple analytical calculations. Scaling analysis shows that the variability of the characteristics of this semiconductor increases as the effects of the short channel increases. Therefore, with a slight increase of length and a reduction of width, oxide thickness, and dopant factor, we could correct the effect of the short channel. 相似文献
40.
The fracture behaviour and morphologies of high-strength boron steel were investigated at different temperatures at a constant strain rate of 0.1 s-1 based on isothermal tensile tests. Fracture mechanisms were also analyzed based on the relationship between microstructure transformation and continuous cooling transformation(CCT) curves. It is found that 1) fractures of the investigated steel at high temperatures are dimple fractures; 2) the deformation of high-strength boron steel at high temperatures accelerates diffusion transformations; thus, to obtain full martensite, a higher cooling rate is needed; and 3) the investigated steel has the best plasticity when the deformation temperature is 750 °C. 相似文献