全文获取类型
收费全文 | 19128篇 |
免费 | 2369篇 |
国内免费 | 2875篇 |
专业分类
化学 | 15010篇 |
晶体学 | 296篇 |
力学 | 775篇 |
综合类 | 264篇 |
数学 | 2010篇 |
物理学 | 6017篇 |
出版年
2024年 | 32篇 |
2023年 | 180篇 |
2022年 | 432篇 |
2021年 | 482篇 |
2020年 | 513篇 |
2019年 | 577篇 |
2018年 | 472篇 |
2017年 | 432篇 |
2016年 | 744篇 |
2015年 | 802篇 |
2014年 | 977篇 |
2013年 | 1376篇 |
2012年 | 1549篇 |
2011年 | 1601篇 |
2010年 | 1213篇 |
2009年 | 1177篇 |
2008年 | 1462篇 |
2007年 | 1353篇 |
2006年 | 1223篇 |
2005年 | 1027篇 |
2004年 | 969篇 |
2003年 | 861篇 |
2002年 | 961篇 |
2001年 | 751篇 |
2000年 | 581篇 |
1999年 | 445篇 |
1998年 | 281篇 |
1997年 | 288篇 |
1996年 | 240篇 |
1995年 | 214篇 |
1994年 | 189篇 |
1993年 | 176篇 |
1992年 | 161篇 |
1991年 | 115篇 |
1990年 | 104篇 |
1989年 | 89篇 |
1988年 | 50篇 |
1987年 | 54篇 |
1986年 | 42篇 |
1985年 | 37篇 |
1984年 | 26篇 |
1983年 | 18篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
212.
Rui Hong Yi-Xin Jiang Jie Leng Ming-Jin Liu Kai-Zhi Shen Qiang Fu Jie Zhang 《高分子科学》2021,39(6):756-769
General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications. To achieve the reinforcement and broaden the application scope of high-density polyethylene(HDPE), multi-flow vibration injection molding(MFVIM) and ultrahigh molecular weight polyethylene(UHMWPE) are synergistically employed in this work. Herein, the MFVIM has better shear layer control ability and higher fabrication advantage for complex parts than other analogous novel injection molding technologies reported.The reinforcing effect of various filling times and UHMWPE contents as well as the corresponding microstructure evolution are investigated.When 5 wt% UHMWPE is added, MFVIM process with six flow times thickens the shear layer to the whole thickness. The tensile strength and modulus increase to 2.14 and 1.39 times, respectively, compared to neat HDPE on the premise of remaining 70% impact strength. Structural characterizations indicate that the enhancement is attributed to the improvement of shish-kebab content and lamellae compactness, as well as related to the corresponding size distributions of undissolved UHMWPE particles. This novel injection molding technology with great industrial prospects provides a facile and effective strategy to broaden the engineering applications of HDPE materials. Besides, excessive UHMWPE may impair the synergistic enhancement effect, which is also reasonably explained. 相似文献
213.
214.
215.
216.
针对用太阳运动模拟平台实现太阳运行位置的全面预测和重现这一问题,提出了采用单片机对该平台进行控制,电机通过变频实现不同时间段不同速率运动模拟太阳运行轨迹的方法。根据输入日期计算出太阳的高度角和方位角,并转换为驱动电机的脉冲数和频率,电机带动执行机构运动使模拟光源到达预定位置。用编码器测量电机实际脉冲,定期进行误差校正来提高系统的稳定性和精度,减少误差。经过实验验证,该平台能够使模拟光源按照预计的轨迹运动,得出该方法是可行的,所设计的程序具有可靠性的结论。 相似文献
217.
218.
Bipolar resistive switching characteristics are investigated in ZrO2 containing Cu thin layer devices, particularly for the self‐isolated‐structure device fabricated by one step lift‐off process. Compared with the traditional‐structure device, the self‐isolated‐structure device shows more uniform resistive switching characteristics. This is because the isolation of each device cell has negligible influence on each other and thus mitigates possible crosstalk between each cell. These results suggest that the feasibility of good stabilization of the resistive switching parameters can be obtained through one step lift‐off process. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
219.
For the specific slip geometry of two sets of coplanar systems (a total of four systems) in fcc metals, the range of dislocation networks in boundaries aligned with one of the two active slip planes is predicted from the Frank equation for boundaries free of long-range elastic stresses. Detailed comparison with experimental data for eight dislocation boundaries in cold-rolled aluminium grains of the 45° ND rotated Cube orientation is conducted. It is concluded that the boundaries are Low-Energy Dislocation Structures, which are in good agreement with the Frank equation while also lowering the energy by dislocation reactions. Cross slip plays a role in the boundary formation process. 相似文献
220.
Pulsed microwave-driven argon plasma jet with distinctive plume patterns resonantly excited by surface plasmon polaritons 下载免费PDF全文
Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air.The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes.The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons.Moreover,for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave,the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas,frequencies of pulsed modulator,duty cycles of pulsed microwave,peak values of input microwave power,and even by using different materials of dielectric tubes.In addition,the emission spectrum,the plume temperature,and other plasma parameters are measured,which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications. 相似文献