全文获取类型
收费全文 | 24389篇 |
免费 | 2376篇 |
国内免费 | 4658篇 |
专业分类
化学 | 6823篇 |
晶体学 | 420篇 |
力学 | 974篇 |
综合类 | 266篇 |
数学 | 7283篇 |
物理学 | 3664篇 |
综合类 | 11993篇 |
出版年
2024年 | 76篇 |
2023年 | 208篇 |
2022年 | 433篇 |
2021年 | 504篇 |
2020年 | 581篇 |
2019年 | 589篇 |
2018年 | 593篇 |
2017年 | 840篇 |
2016年 | 944篇 |
2015年 | 842篇 |
2014年 | 1341篇 |
2013年 | 1858篇 |
2012年 | 1716篇 |
2011年 | 1760篇 |
2010年 | 1495篇 |
2009年 | 1611篇 |
2008年 | 1606篇 |
2007年 | 1888篇 |
2006年 | 1567篇 |
2005年 | 1437篇 |
2004年 | 1168篇 |
2003年 | 1032篇 |
2002年 | 1020篇 |
2001年 | 843篇 |
2000年 | 813篇 |
1999年 | 704篇 |
1998年 | 602篇 |
1997年 | 524篇 |
1996年 | 481篇 |
1995年 | 413篇 |
1994年 | 370篇 |
1993年 | 288篇 |
1992年 | 244篇 |
1991年 | 199篇 |
1990年 | 189篇 |
1989年 | 158篇 |
1988年 | 136篇 |
1987年 | 57篇 |
1986年 | 46篇 |
1985年 | 42篇 |
1984年 | 38篇 |
1983年 | 20篇 |
1982年 | 30篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
采用正交试验方法研究了现有原燃料及设备条件下水钢高炉的最佳炉料结构;在此基础上进一步优化炉料结构,并对它们的冶金性能进行了试验.结果表明:目前水钢高炉最佳炉料结构为86%的烧结矿(二元碱度为1.8)配加14%的印度块矿与越南块矿的混合矿(混合比例为1:1);此种炉料结构的软熔性能好,还原性能达到优良水平,炉渣碱度合适,但低温还原粉化性能不佳;若采用二元碱度为1.7的烧结矿,使炉渣的碱度低于1.2,则熟料率达到90%的炉料结构是完全可行的. 相似文献
982.
电磁阻尼器性能参数试验研究 总被引:2,自引:1,他引:1
电磁阻尼器性能与多种因素有关,在电磁阻尼器基本性能试验研究基础上,制作了一个电磁阻尼器模型,进行了涡流板厚度参数影响的试验研究:做了3种厚度涡流板在不同频率、不同位移情况下的试验,得到了涡流板厚度对阻尼器性能影响的定性结论。 相似文献
983.
以特殊的线性振荡方程y" g(t)y=0(其中limg(t)= ∞)为例讨论了高振荡微分方程数值解问题.分析了梯形格式的整体截断误差,并对梯形格式做了修改,讨论了修改后格式的整体截断误差,使得整体截断误差中的T9/4变成了T-1/4. 相似文献
984.
Stefan Dieckhöfer Dr. Denis Öhl João R. C. Junqueira Thomas Quast Prof. Dr. Thomas Turek Prof. Dr. Wolfgang Schuhmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(19):5906-5912
Discerning the influence of electrochemical reactions on the electrode microenvironment is an unavoidable topic for electrochemical reactions that involve the production of OH− and the consumption of water. That is particularly true for the carbon dioxide reduction reaction (CO2RR), which together with the competing hydrogen evolution reaction (HER) exert changes in the local OH− and H2O activity that in turn can possibly affect activity, stability, and selectivity of the CO2RR. We determine the local OH− and H2O activity in close proximity to a CO2-converting Ag-based gas diffusion electrode (GDE) with product analysis using gas chromatography. A Pt nanosensor is positioned in the vicinity of the working GDE using shear-force-based scanning electrochemical microscopy (SECM) approach curves, which allows monitoring changes invoked by reactions proceeding within an otherwise inaccessible porous GDE by potentiodynamic measurements at the Pt-tip nanosensor. We show that high turnover HER/CO2RR at a GDE lead to modulations of the alkalinity of the local electrolyte, that resemble a 16 m KOH solution, variations that are in turn linked to the reaction selectivity. 相似文献
985.
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
986.
用分子动力学模拟方法研究了五种不同冷却速率对Lennard-Jones体系凝固过程中结构与动力学性质的影响。采用两种不同的方法来确定玻璃转变温度Tg,并且对结晶温度Tc、径向分布函数g(r)、均方位移函数MSD与扩散系数D、平均配位数进行比较分析。结果表明:冷却速率影响Lennard-Jones体系凝固过程中的结构。当使用足够高的冷却速率冷却时,体系发生玻璃化转变,而且冷却速率越快,玻璃转变温度越高;当冷却速率较小时,体系形成晶体,而且冷却速率越慢,结晶温度越高,结晶程度也越高。同时发现,冷却速率对扩散系数和平均配位数也有很大影响,二者在体系发生玻璃转变时都有一个缓变的过程,表明了过冷液相区的存在。 相似文献
987.
Charge redistribution and a shortening of the Fe—As bond at the quantum critical point of SmO1–xFxFeAs 下载免费PDF全文
Jie Cheng Peng Dong Wei Xu Shengli Liu Wangsheng Chu Xianhui Chen Ziyu Wu 《Journal of synchrotron radiation》2015,22(4):1030-1034
Many researchers have pointed out that there is a quantum critical point (QCP) in the F‐doped SmOFeAs system. In this paper, the electronic structure and local structure of the superconductive FeAs layer in SmO1–xFxFeAs as a function of the F‐doping concentration have been investigated using Fe and As K‐edge X‐ray absorption spectroscopy. Experiments performed on the X‐ray absorption near‐edge structure showed that in the vicinity of the QCP the intensity of the pre‐edge feature at the Fe‐edge decreases continuously, while there is a striking rise of the shoulder‐peak at the As edge, suggesting the occurrence of charge redistribution near the QCP. Further analysis on the As K‐edge extended X‐ray absorption fine structure demonstrated that the charge redistribution originates mostly from a shortening of the Fe—As bond at the QCP. An evident relationship between the mysterious QCP and the fundamental Fe—As bond was established, providing new insights on the interplay between QCP, charge dynamics and the local structural Fe—As bond in Fe‐based superconductors. 相似文献
988.
989.
990.