全文获取类型
收费全文 | 63223篇 |
免费 | 4961篇 |
国内免费 | 2798篇 |
专业分类
电工技术 | 3370篇 |
技术理论 | 6篇 |
综合类 | 4177篇 |
化学工业 | 10716篇 |
金属工艺 | 3988篇 |
机械仪表 | 3936篇 |
建筑科学 | 4768篇 |
矿业工程 | 2248篇 |
能源动力 | 1988篇 |
轻工业 | 3614篇 |
水利工程 | 1093篇 |
石油天然气 | 4651篇 |
武器工业 | 465篇 |
无线电 | 6600篇 |
一般工业技术 | 7374篇 |
冶金工业 | 3421篇 |
原子能技术 | 728篇 |
自动化技术 | 7839篇 |
出版年
2024年 | 261篇 |
2023年 | 1016篇 |
2022年 | 1778篇 |
2021年 | 2529篇 |
2020年 | 1895篇 |
2019年 | 1691篇 |
2018年 | 1876篇 |
2017年 | 2095篇 |
2016年 | 1879篇 |
2015年 | 2418篇 |
2014年 | 3089篇 |
2013年 | 3570篇 |
2012年 | 3765篇 |
2011年 | 4110篇 |
2010年 | 3780篇 |
2009年 | 3375篇 |
2008年 | 3326篇 |
2007年 | 3275篇 |
2006年 | 3276篇 |
2005年 | 2821篇 |
2004年 | 2086篇 |
2003年 | 2190篇 |
2002年 | 2502篇 |
2001年 | 2097篇 |
2000年 | 1629篇 |
1999年 | 1729篇 |
1998年 | 1267篇 |
1997年 | 1075篇 |
1996年 | 1110篇 |
1995年 | 853篇 |
1994年 | 640篇 |
1993年 | 471篇 |
1992年 | 369篇 |
1991年 | 277篇 |
1990年 | 208篇 |
1989年 | 167篇 |
1988年 | 154篇 |
1987年 | 88篇 |
1986年 | 70篇 |
1985年 | 37篇 |
1984年 | 38篇 |
1983年 | 27篇 |
1982年 | 25篇 |
1981年 | 15篇 |
1980年 | 23篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The lack of physical fitness is a contributing factor to the etiology of musculoskeletal disorders resulting from the manual handling of material in industry. Thus the major objectives of this paper were (1) to discuss the role of physical fitness in the control of occupational injuries; (2) to review techniques available in the exercise physiology literature for increasing human physical capacity in industry; and (3) to review and evaluate studies on the effects of physical training on individuals engaged in manual handling tasks. 相似文献
83.
Bistatic radar scattering by a chaff cloud 总被引:7,自引:0,他引:7
The bistatic radar scattering cross section of a chaff cloud is investigated in the ground-based system for arbitrarily polarized transmitters and receivers. The chaff cloud considered consists of a large number of identical thin conducting wires whose thickness is very small compared to their length and to the wavelength. Numerical results for bistatic cross sections for the cases of orientations uniform in azimuth and Gaussian in elevation, and also for uniformly random orientation in both azimuth and in elevation are presented in the form of three-dimensional graphs, for a few typical examples 相似文献
84.
通过对甸镓砷磷半导体激光和常用He-Ne激光生物特性进行初步比较,说明半导体激光对治疗椎基底动脉供血不足疗效较明显。 相似文献
85.
86.
87.
The current carrying capacity of single-walled semiconducting carbon nanotubes (CNTs) is studied by self-consistent quantum
simulations using the non-equilibrium Green’s function formalism with the self-consistent Born approximation. The simulation
shows that the current carrying capacity depends on the bias regime and is drastically different from that of metallic tubes.
For long CNTs (with a length much longer than zone boundary and optical phonon scattering mean free path), the current saturates
around 20 μA in the forward bias regime with unipolar transport due to phonon scattering. In ambipolar transport regime, the
current delivery limit is still about 20 μA due to recombination of electron and hole currents. In contrast, for short semiconducting
CNTs, the current delivery capacity can be above 25 μA in the unipolar transport regime and further double in the ambipolar
transport regime. In reverse bias regime, the current of a long CNT can exceed 20 μA due to the second subband conduction
and increased electron injection from the drain. The simulation provides a coherent explanation to the dependence of current
delivery limit on bias regime and channel length, which is consistent with recent experiments. 相似文献
88.
以氧化锰矿粉为原料,添加ZB粘结剂进行冷固成团,所得冷固团块不仅具有足够的机械强度,而且具有良好的耐湿性,适用于长距离运输和露天堆存,是一种可与块矿性能相媲美的优质炉料,为充分利用矿山及冶炼厂的锰矿粉找到了一条良好的途径. 相似文献
89.
90.
Ashraf Bastawros Abhijit Chandra Yongjin Guo Bo Yan 《Journal of Electronic Materials》2002,31(10):1022-1031
The role of a porous pad in controlling material-removal rate (MRR) during the chemical-mechanical planarization (CMP) process
has been studied numerically. The numerical results are used to develop a phenomenological model that correlates the forces
on each individual abrasive particle to the applied nominal pressure. The model provides a physical explanation for the experimentally
observed domains of pressure-dependent MRR, where the pad deformation controls the load sharing between active-abrasive particles
and direct pad-wafer contact. The predicted correlations between MRR and slurry characteristics, i.e., particle size and concentration,
are in agreement with experimentally measured trends reported by Ouma1 and Izumitani.2 相似文献