全文获取类型
收费全文 | 70913篇 |
免费 | 10085篇 |
国内免费 | 7486篇 |
专业分类
化学 | 37223篇 |
晶体学 | 543篇 |
力学 | 3451篇 |
综合类 | 399篇 |
数学 | 6068篇 |
物理学 | 20077篇 |
无线电 | 20723篇 |
出版年
2024年 | 257篇 |
2023年 | 1643篇 |
2022年 | 2013篇 |
2021年 | 2581篇 |
2020年 | 2589篇 |
2019年 | 2289篇 |
2018年 | 2002篇 |
2017年 | 1956篇 |
2016年 | 2786篇 |
2015年 | 2986篇 |
2014年 | 3630篇 |
2013年 | 4655篇 |
2012年 | 5727篇 |
2011年 | 5688篇 |
2010年 | 4065篇 |
2009年 | 4082篇 |
2008年 | 4451篇 |
2007年 | 3957篇 |
2006年 | 3895篇 |
2005年 | 3406篇 |
2004年 | 2587篇 |
2003年 | 2154篇 |
2002年 | 1966篇 |
2001年 | 1710篇 |
2000年 | 1563篇 |
1999年 | 1750篇 |
1998年 | 1477篇 |
1997年 | 1322篇 |
1996年 | 1424篇 |
1995年 | 1228篇 |
1994年 | 1116篇 |
1993年 | 932篇 |
1992年 | 864篇 |
1991年 | 672篇 |
1990年 | 570篇 |
1989年 | 420篇 |
1988年 | 375篇 |
1987年 | 306篇 |
1986年 | 231篇 |
1985年 | 229篇 |
1984年 | 189篇 |
1983年 | 158篇 |
1982年 | 112篇 |
1981年 | 85篇 |
1980年 | 67篇 |
1979年 | 40篇 |
1978年 | 30篇 |
1976年 | 31篇 |
1975年 | 36篇 |
1974年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
氢脆具有很强的微观组织敏感性,威胁着各类高强结构材料的安全服役.采用激光-电弧复合焊工艺对BS960E型高强钢进行焊接,并对接头在原位电化学充氢的条件下进行慢应变速率(10-5s-1)拉伸试验,结合微观组织和断裂特征进行分析并对接头的氢脆行为进行研究.结果 表明,焊接热循环所形成的富马氏体中的细晶区可以使接头表现出一定的氢脆敏感性,马氏体较大的氢扩散系数和较低的氢溶解度以及氢在晶界上的快速扩散是引起接头对氢脆敏感的主要原因,通过控制焊接工艺参数可抑制焊接热循环所引起的马氏体转变量,能够降低BS960E型高强钢激光-电弧复合焊接头的氢脆敏感性. 相似文献
12.
Electric nanogenerators that directly convert the energy of moving drops into electrical signals require hydrophobic substrates with a high density of static electric charge that is stable in “harsh environments” created by continued exposure to potentially saline water. The recently proposed charge-trapping electric generators (CTEGs) that rely on stacked inorganic oxide–fluoropolymer (FP) composite electrets charged by homogeneous electrowetting-assisted charge injection (h-EWCI) seem to solve both problems, yet the reasons for this success have remained elusive. Here, systematic measurements at variable oxide and FP thickness, charging voltage, and charging time and thermal annealing up to 230 °C are reported, leading to a consistent model of the charging process. It is found to be controlled by an energy barrier at the water-FP interface, followed by trapping at the FP-oxide interface. Protection by the FP layer prevents charge densities up to −1.7 mC m−2 from degrading and the dielectric strength of SiO2 enables charge decay times up to 48 h at 230 °C, suggesting lifetimes against thermally activated discharging of thousands of years at room temperature. Combining high dielectric strength oxides and weaker FP top coatings with electrically controlled charging provides a new paradigm for developing ultrastable electrets for applications in energy harvesting and beyond. 相似文献
13.
Nonlinear Dynamics - The classical Kuramoto model serves as a useful tool for studying synchronization transitions in coupled oscillators that is limited to the sinusoidal and pairwise... 相似文献
14.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed... 相似文献
15.
Liu Jingze Fei Qingguo Wu Shaoqing Tang Zhenhuan Zhang Dahai 《Nonlinear dynamics》2021,106(3):1869-1890
Nonlinear Dynamics - Rolling bearing and squeeze film damper will introduce structural nonlinearity into the dynamic model of aeroengine. Rubbing will occur due to the clearance reduction design of... 相似文献
16.
Yi-Tong Xu Tian-Yang Zhang Zheng Li Xiang-Nan Liu Yuan-Cheng Zhu Wei-Wei Zhao Hong-Yuan Chen Jing-Juan Xu 《Electroanalysis》2022,34(6):947-955
Photoelectrochemical (PEC) cytosensors, a combination of the PEC process and the living-cell assay, have emerged as a powerful tool in the analytical and biological science. This mini review provides a brief introduction of this arena and summaries the key steps about the development of PEC cytosensors with representative examples, followed by future prospects based on our own opinions. 相似文献
17.
Li Quanxin Li Zheng He Cheng Sun Huilin Tan Shengheng Zhang Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2105-2115
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with... 相似文献
18.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
19.
Lili Hao Jiaxiang Li Peng Wang Zongliang Wang Zhenxu Wu Yu Wang Zixue Jiao Min Guo Tongfei Shi Qigang Wang Yoshihiro Ito Yen Wei Peibiao Zhang 《Advanced functional materials》2021,31(15):2009661
The degradation behavior of implants is significantly important for bone repair. However, it is still unprocurable to spatiotemporally regulate the degradation of the implants to match bone ingrowth. In this paper, a magneto-controlled biodegradation model is established to explore the degradation behavior of magnetic scaffolds in a magnetothermal microenvironment generated by an alternating magnetic field (AMF). The results demonstrate that the scaffolds can be heated by magnetic nanoparticles (NPs) under AMF, which dramatically accelerated scaffold degradation. Especially, magnetic NPs modified by oleic acid with a better interface compatibility exhibit a greater heating efficiency to further facilitate the degradation. Furthermore, the molecular dynamics simulations reveal that the enhanced motion correlation between magnetic NPs and polymer matrix can accelerate the energy transfer. As a proof-of-concept, the feasibility of magneto-controlled degradation for implants is demonstrated, and an optimizing strategy for better heating efficiency of nanomaterials is provided, which may have great instructive significance for clinical medicine. 相似文献
20.