全文获取类型
收费全文 | 4833篇 |
免费 | 956篇 |
国内免费 | 1385篇 |
专业分类
化学 | 3634篇 |
晶体学 | 155篇 |
力学 | 259篇 |
综合类 | 135篇 |
数学 | 754篇 |
物理学 | 2237篇 |
出版年
2024年 | 17篇 |
2023年 | 65篇 |
2022年 | 162篇 |
2021年 | 157篇 |
2020年 | 163篇 |
2019年 | 176篇 |
2018年 | 163篇 |
2017年 | 204篇 |
2016年 | 158篇 |
2015年 | 249篇 |
2014年 | 264篇 |
2013年 | 354篇 |
2012年 | 381篇 |
2011年 | 430篇 |
2010年 | 347篇 |
2009年 | 380篇 |
2008年 | 440篇 |
2007年 | 422篇 |
2006年 | 379篇 |
2005年 | 324篇 |
2004年 | 256篇 |
2003年 | 210篇 |
2002年 | 265篇 |
2001年 | 232篇 |
2000年 | 218篇 |
1999年 | 147篇 |
1998年 | 93篇 |
1997年 | 58篇 |
1996年 | 53篇 |
1995年 | 50篇 |
1994年 | 51篇 |
1993年 | 47篇 |
1992年 | 37篇 |
1991年 | 25篇 |
1990年 | 26篇 |
1989年 | 26篇 |
1988年 | 19篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有7174条查询结果,搜索用时 15 毫秒
131.
Photo-Induced Ultrafast Electron Dynamics in Anatase and Rutile TiO2: Effects of Electron-Phonon Interaction 下载免费PDF全文
The photo-induced ultrafast electron dynamics in both anatase and rutile TiO\begin{document}$_{2}$\end{document} are investigated by using the Boltzmann transport equation with the explicit incorporation of electron-phonon scattering rates. All structural parameters required for dynamic simulations are obtained from ab initio calculations. The results show that although the longitudinal optical modes significantly affect the electron energy relaxation dynamics in both phases due to strong Fr?hlich-type couplings, the detailed relaxation mechanisms have obvious differences. In the case of a single band, the energy relaxation time in anatase is 24.0 fs, twice longer than 11.8 fs in rutile. This discrepancy is explained by the different diffusion distributions over the electronic Bloch states and different scattering contributions from acoustic modes in the two phases. As for the multiple-band situation involving the lowest six conduction bands, the predicted overall relaxation times are about 47 fs and 57 fs in anatase and rutile, respectively, very different from the case of the single band. The slower relaxation in rutile is attributed to the existence of multiple rate-controlled steps during the dynamic process. The present findings may be helpful to control the electron dynamics for designing efficient TiO\begin{document}$_{2}$\end{document} -based devices. 相似文献
132.
该研究优化了医用口罩样本中16种有机磷酸酯(OPEs)的萃取和净化前处理过程,建立了超高效液相色谱-串联质谱(UPLC-MS/MS)测定方法。样本经甲醇超声萃取后,采用ENVI-18固相萃取小柱净化,最终使用Acquity UPLC BEH C18色谱柱以5 mmol/L乙酸铵缓冲溶液-甲醇为流动相进行分离,采用UPLC-MS/MS测定,内标法定量。结果表明,16种OPEs在0.1~50 μg/L质量浓度范围内呈良好的线性关系(r > 0.995),方法检出限为0.004 60~1.03 ng/dm2,定量下限为0.015 2~3.43 ng/dm2,加标回收率为68.8%~140%,相对标准偏差为0.70%~18%。采用所建立的方法对42个医用口罩中16种OPEs进行测定,其总浓度为6.60~2 387 ng/dm2,其中12种OPEs的检出率高于50%,表明这些OPEs在医用口罩中普遍存在。磷酸三苯酯(TPHP)和磷酸三(1-氯-2-丙基)酯(TCIPP)为主要的OPEs,浓度分别为0.131~2 274 ng/dm2和0.370~79.8 ng/dm2。整体上OPEs的浓度均较低,推测口罩样本中的OPEs可能是生产和包装过程中受空气或塑料包装污染所致。 相似文献
133.
WeiPing Liu ZhiHong Li JiangJun He XiaoDong Tang Gang Lian Zhu An JianJun Chang Han Chen QingHao Chen XiongJun Chen ZhiJun Chen BaoQun Cui XianChao Du ChangBo Fu Lin Gan Bing Guo GuoZhu He Alexander Heger SuQing Hou HanXiong Huang Ning Huang BaoLu Jia LiYang Jiang Shigeru Kubono JianMin Li KuoAng Li Tao Li YunJu Li Maria Lugaro XiaoBing Luo HongYi Ma ShaoBo Ma DongMing Mei YongZhong Qian JiuChang Qin Jie Ren YangPing Shen Jun Su LiangTing Sun WanPeng Tan Isao Tanihata Shuo Wang Peng Wang YouBao Wang Qi Wu ShiWei Xu ShengQuan Yan LiTao Yang Yao Yang XiangQing Yu Qian Yue Sheng Zeng HuanYu Zhang Hui Zhang LiYong Zhang NingTao Zhang QiWei Zhang Tao Zhang XiaoPeng Zhang XueZhen Zhang ZiMing Zhang Wei Zhao Zuo Zhao Chao Zhou JUNA Collaboration 《中国科学:物理学 力学 天文学(英文版)》2016,59(4):642001
Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of~(25)Mg(p,γ)~(26)Al,~(19)F(p,α)~(16)O,~(13)C(α,n)~(16)O and ~(12)C(α,γ)~(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given. 相似文献
134.
JianJun He ShiWei Xu ShaoBo Ma Jun Hu LiYong Zhang ChangBo Fu NingTao Zhang Gang Lian Jun Su YunJu Li ShengQuan Yan YangPing Shen SuQing Hou BaoLu Jia Tao Zhang XiaoPeng Zhang Bing Guo Shigeru Kubono WeiPing Liu 《中国科学:物理学 力学 天文学(英文版)》2016,59(5):652001
In 2014, the National Natural Science Foundation of China(NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory(JUNA) project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch(AGB) stars, measuring the key ~(19)F( p,α)~(16)O reaction at effective burning energies(i.e., at Gamow window) is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions. 相似文献
135.
Chromatographia - The application of temperature gradient interaction chromatography (TGIC) as an advanced technique for the characterisation of polymers is discussed, in comparison to other liquid... 相似文献
136.
137.
Chun Lian Zhang Xi Fu Jiang Li Yang Shu Hua Zhang Shao Ming Shi 《Journal of Cluster Science》2014,25(2):459-466
A rare heterometallic cluster-based polymer [Cu4(Hbhea)4(μ 2-OCH3) K(CH3OH))] n ·(H2O) n (1) (H3bhea = 2-[bis-(2-hydroxy-ethyl)-amino]-ethanesulfonic acid), has been synthesized and structurally determined by single crystal X-ray diffraction, elemental analysis. Crystallographic unit of 1 consists of four Cu(II), four Hbhea ligands, one methanol molecule, one methanol anion, one K ion and one crystal lattice water and formed anion cluster [Cu4(Hbhea)4(CH3O)]? which further constructed a 3-D polymer by linking the six-coordination K ions. 相似文献
138.
Xiaotian Tian Sai Lian Limin Zhao Xiaomei Chen Zhiyong Huang Xi Chen 《Journal of Solid State Electrochemistry》2014,18(9):2375-2382
A novel electrochemiluminescence (ECL) biosensor based on platinum nanoflowers (PtNFs)/graphene oxide (GO)/glucose oxidase (GODx) was discovered for glucose detection. PtNFs/GO was synthesized using a nontoxic, rapid, one-pot and template-free method and characterized by transmission electron microscopy (TEM) and high-resolution TEM techniques. The as-prepared PtNFs/GO with clean surface and multiporous structure was used to assemble GODx to form a glucose biosensor. Based on ECL results, the PtNFs/GO/GODx film-modified electrode displayed a high electrocatalytic activity towards the oxidation of glucose, which generated hydrogen peroxide (H2O2) to react with the luminol radicals thus enhanced the luminol ECL. Under the optimized conditions, two linear regions of ECL intensity to glucose concentration were valid in the range from 5 to 80 μmol/L (r?=?0.9957) and 80 to 1,000 μmol/L (r?=?0.9909) with a detection limit (S/N?=?3) of 2.8 μmol/L. In order to verify the reliability, the thus-fabricated biosensor was applied to determine the glucose concentration in glucose injection, glucose functional drink, and blood serum. The results indicated that the proposed biosensor presented good characteristics in terms of high sensitivity and good reproducibility for glucose determination, promising the applicability of this sensor in practical analysis. 相似文献
139.
HOU Hong-Ying 《物理化学学报》2014,30(8):1393-1407
最近,碱性聚合物电解质膜燃料电池(APEMFC)因具有电极反应动力学快以及不依赖于贵金属铂催化剂等诸多优点而成为一个热门话题.作为其中一个关键部件,碱性聚合物电解质膜直接影响燃料电池的性能和成本.然而,迄今为止,仍然没有令人满意的碱性电解质膜材料.为此,大量研究被开展和报道.本文综述了近三年内文献中关于燃料电池碱性聚合物电解质膜的最新研究进展:包括各种各样的合成策略,构效关系,水管理以及非原位或原位稳定性测试等等.尤其是一些新的金属离子基阴离子交换膜和冠醚基阴离子交换膜首次被提及和评论.此外,还进一步预测了将来的发展趋势. 相似文献
140.
An oligosaccharide donor, acetylated sept-o-glucopyranose tetradecyl carbamate, was designed and synthesized. This compound could be easily linked to hydroxyl-containing compounds through an Oglycosidic bond. Characterization of all the oligosaccharide intermediates and the final product was thoroughly discussed. 相似文献