全文获取类型
收费全文 | 7408篇 |
免费 | 1375篇 |
国内免费 | 1191篇 |
专业分类
化学 | 6059篇 |
晶体学 | 81篇 |
力学 | 392篇 |
综合类 | 83篇 |
数学 | 786篇 |
物理学 | 2573篇 |
出版年
2024年 | 30篇 |
2023年 | 149篇 |
2022年 | 324篇 |
2021年 | 311篇 |
2020年 | 359篇 |
2019年 | 412篇 |
2018年 | 306篇 |
2017年 | 286篇 |
2016年 | 404篇 |
2015年 | 416篇 |
2014年 | 459篇 |
2013年 | 586篇 |
2012年 | 708篇 |
2011年 | 665篇 |
2010年 | 414篇 |
2009年 | 426篇 |
2008年 | 458篇 |
2007年 | 369篇 |
2006年 | 358篇 |
2005年 | 320篇 |
2004年 | 276篇 |
2003年 | 242篇 |
2002年 | 325篇 |
2001年 | 267篇 |
2000年 | 167篇 |
1999年 | 150篇 |
1998年 | 128篇 |
1997年 | 74篇 |
1996年 | 83篇 |
1995年 | 63篇 |
1994年 | 64篇 |
1993年 | 51篇 |
1992年 | 77篇 |
1991年 | 49篇 |
1990年 | 50篇 |
1989年 | 30篇 |
1988年 | 22篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1959年 | 2篇 |
1957年 | 2篇 |
1936年 | 3篇 |
排序方式: 共有9974条查询结果,搜索用时 15 毫秒
991.
采用水热法结合银镜反应制备出一系列不同Ag负载量(2.2%、4.0%、6.4%,w/w)改性的3D纳米网状结构Ag@Ti O2薄膜电极。利用电感耦合等离子体技术(ICP)、X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和X射线能谱(EDX)等表征手段测试所合成材料的形貌及成分,实验结果表明Ag纳米颗粒可以成功沉积在Ti O2纳米线表面。电化学测试数据则表明,4.0%(w/w)负载量的Ag@Ti O2相比于未改性和其他负载量的Ti O2纳米线具有更好的倍率性能和更稳定的可逆容量。在50,100,200,400,800和1 200 m A·g~(-1)的电流密度条件下,该改性电极的放电容量可分别达到261.4,253.7,239.5,216.5,193.1和185.1 m Ah·g~(-1),在200 m A·g~(-1)下循环80次后容量保持率仍能达到99.8%。 相似文献
992.
This work was focused on the influence of match degree of structure parameters i.e. molecular size, volume and polarity (denoted as Rd, Vd and Pd) between imprinted cavities in Qu-MIP and Xn on the adsorption selectivity. The results presented that the influence of Rd on the adsorption selectivity was the largest and the most regular, while the influence of Pd was the smallest and the most irregular. Besides, the influence degree of Vd was decreased in general with the increase of Rd. However, as Rd was in the threshold of [0.99, 1.02], Vd would rise to the major influence factor. Furthermore, utilizing data obtained from experiment, the influence authority of Rd, Vd and Pd on the adsorption selectivity was calculated theoretically through multiple linear regression and principal component analysis of IBM SPSS Statistics 20, and results showed the authority order was Rd, Vd and Pd at any circumstance despite the value was different, which was in accordance with the result we directly inducted from the experiment. 相似文献
993.
994.
The fourth power mean of the general 2-dimensional Kloostermann sums mod <Emphasis Type="Italic">p</Emphasis>
下载免费PDF全文
![点击此处可从《数学学报(英文版)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The main purpose of this paper is using the analytic methods and the properties of Gauss sums to study the computational problem of one kind fourth power mean of the general 2-dimensional Kloostermann sums mod p, and give an exact computational formula for it. 相似文献
995.
Novel Bi2MoO6 Nanosheets/Vertical TiO2 Nanorods Arrays Heterojunction with Enhanced Photoelectrochemical Performance under Visible Light Irradiation
下载免费PDF全文
![点击此处可从《化学物理学报(中文版)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xiang Gao Jia-wei Xue Ying Luo Xiao-di Zhu Song Sun Jun Bao Wen-dong Wang 《化学物理学报(中文版)》2017,30(5):576-580
Novel Bi2MoO6/TiO2 heterojunction was fabricated by growing Bi2MoO6 nanosheets arrays on the vertically aligned TiO2 nanorods arrays via a two-step solvothermal method. The obtained Bi2MoO6/TiO2 hierarchical heterojunction showed excellent visible light photoelectrochemical performance. Compared with the pure TiO2 and Bi2MoO6, the photocurrent density of the heterojunction was increased 57 and 29 times, respectively. Furthermore, the hydrogen generation rate of the Bi2MoO6/TiO2 for photoelectrocatalytic water-splitting was about 6 times higher than that of the pure Bi2MoO6. The improved performance can be attributed to the synergistic effects of enhanced absorption of visible light, increase of migration rate and separation efficiency of photo-induced carriers. 相似文献
996.
Tinghai Yan Haijun Bin Yankang Yang Lingwei Xue Zhi-Guo Zhang Yongfang Li 《中国科学:化学(英文版)》2017,60(4):537-544
The medium band gap donor-acceptor(D-A) copolymer J61 based on bi(alkylthio-thienyl)benzodithiophene as donor unit and fluorobenzotriazole as acceptor unit and thiophene as π-bridge has demonstrated excellent photovoltaic performance as donor material in nonfullerene polymer solar cells(PSCs) with narrow bandgap n-type organic semiconductor ITIC as acceptor.For studying the effect of π-bridges on the photovoltaic performance of the D-A copolymers,here we synthesized a new D-A copolymer J61-F based on the same donor and acceptor units as J61 but with furan π-bridges instead of thiophene.J61-F possesses a deeper the highest occupied molecular orbital(HOMO) level at-5.45 eV in comparison with that(-5.32 eV) of J61.The non-fullerene PSCs based on J61-F:ITIC exhibited a maximum power conversion efficiency(PCE) of 8.24%with a higher open-circuit voltage(V_(oc)) of 0.95 V,which is benefitted from the lower-lying HOMO energy level of J61-F donor material.The results indicate that main chain engineering by changing π-bridges is another effective way to tune the electronic energy levels of the conjugated D-A copolymers for the application as donor materials in non-fullerene PSCs. 相似文献
997.
Yunfeng Xu Chong Zhang Pan Mu Na Mao Xue Wang Qian He Feng Wang Jia-Xing Jiang 《中国科学:化学(英文版)》2017,60(8):1075-1083
Two novel tetra-armed conjugated microporous polymers with different geometries have been designed and synthesized via Suzuki-Miyaura cross coupling polycondensation. Both polymers are stable in various organic solvents tested and are thermally stable. The pyrene-containing polymer of PrPy with the rigid pyrene unit shows a higher Brunauer-Emmet-Teller specific surface area of 1219 m2 g?1 than the tetraphenylethylene-containing polymer of PrTPE (770 m2 g?1), which leads to a high CO2 uptake ability of 3.89 mmol g?1 at 1.13 bar/273 K and a H2 uptake ability of 1.69 wt% at 1.13 bar/77 K. The photocatalytic hydrogen production experiments revealed that PrPy also shows a better photocatalytic performance than PrTPE due to the higher conjugation degree and planar structure, the broader UV-visible (UV-Vis) absorption, the lower photoluminescence lifetime, and the higher specific surface area. 相似文献
998.
Da-Wei Zuo Yi-Tian Gao Yu-Jie Feng Long Xue Yu-Hao Sun 《Theoretical and Mathematical Physics》2017,191(2):725-737
We investigate an AB system, which can be used to describe marginally unstable baroclinic wave packets in a geophysical fluid. Using the generalized Darboux transformation, we obtain higher-order rogue wave solutions and analyze rogue wave propagation and interaction. We obtain bright rogue waves with one and two peaks. For the wave packet amplitude and the mean-flow correction resulting from the self-rectification of the nonlinear wave, the positions and values of the wave crests and troughs are expressed in terms of a parameter describing the state of the basic flow, in terms of a parameter responsible for the interaction of the wave packet and the mean flow, and in terms of the group velocity. We show that the interaction of the wave packet and mean flow and also the group velocity affect the propagation and interaction of the amplitude of the wave packet and the self-rectification of the nonlinear wave. 相似文献
999.
1000.
氮化钛微粉增强镍磷化学复合镀层的组织及其摩擦磨损性能研究 总被引:1,自引:0,他引:1
利用自蔓延高温合成法得到的氮化钛微粉制备了Ni-P-TiN化学复合镀层,采用X射线衍射仪,扫描电子显微镜和电子探针分析了镀层的组织和结构,并在球-块摩擦磨损试验机上对镀层的摩擦学特性进行了研究,结果表明,TiN微粉可使Ni-P化学镀层的组织明显细化,且能提高镀层的最佳时效硬化温度随着Ni-P-TiN化学复合镀层中TiN共析量的增摩擦系数逐渐降低并趋于稳定,耐磨性则存在的一个最佳TiN含量;TiN微 相似文献