全文获取类型
收费全文 | 1127篇 |
免费 | 185篇 |
国内免费 | 113篇 |
专业分类
化学 | 779篇 |
晶体学 | 10篇 |
力学 | 91篇 |
综合类 | 3篇 |
数学 | 94篇 |
物理学 | 448篇 |
出版年
2024年 | 2篇 |
2023年 | 21篇 |
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 41篇 |
2019年 | 52篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 51篇 |
2015年 | 43篇 |
2014年 | 39篇 |
2013年 | 71篇 |
2012年 | 117篇 |
2011年 | 123篇 |
2010年 | 85篇 |
2009年 | 63篇 |
2008年 | 67篇 |
2007年 | 57篇 |
2006年 | 51篇 |
2005年 | 42篇 |
2004年 | 50篇 |
2003年 | 26篇 |
2002年 | 28篇 |
2001年 | 23篇 |
2000年 | 31篇 |
1999年 | 35篇 |
1998年 | 28篇 |
1997年 | 19篇 |
1996年 | 29篇 |
1995年 | 22篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1425条查询结果,搜索用时 15 毫秒
991.
Kuang Y Balakrishnan K Gandhi V Peng X 《Journal of the American Chemical Society》2011,133(48):19278-19281
The major concern for anticancer chemotherapeutic agents is the host toxicity. The development of anticancer prodrugs targeting the unique biochemical alterations in cancer cells is an attractive approach to achieve therapeutic activity and selectivity. We designed and synthesized a new type of nitrogen mustard prodrug that can be activated by high level of reactive oxygen species (ROS) found in cancer cells to release the active chemotherapy agent. The activation mechanism was determined by NMR analysis. The activity and selectivity of these prodrugs toward ROS was determined by measuring DNA interstrand cross-links and/or DNA alkylations. These compounds showed 60-90% inhibition toward various cancer cells, while normal lymphocytes were not affected. To the best of our knowledge, this is the first example of H(2)O(2)-activated anticancer prodrugs. 相似文献
992.
Zhang L Zhang J Kuang Q Xie S Jiang Z Xie Z Zheng L 《Journal of the American Chemical Society》2011,133(43):17114-17117
Controlled syntheses of multicomponent metal nanocrystals (NCs) and high-index surfaces have attracted increasing attention due to the specific physical and chemical properties of such NCs. Taking advantage of copper underpotential deposition as a bridge, hexoctahedral Au-Pd alloy NCs with {hkl} facets exposed were successfully synthesized, while phase separation occurred in the absence of Cu(2+) ions. The as-prepared hexoctahedral Au-Pd alloy NCs exhibited very excellent performance in terms of both formic acid electro-oxidation and methanol tolerance due to synergism between the high-index facets and the alloy. 相似文献
993.
In this paper, a new lattice hydrodynamic model for bidirectional pedestrian flow is proposed by considering the pedestrian’s visual field effect. The stability condition of this model is obtained by the linear stability analysis. The mKdV equation near the critical point is derived to describe the density wave of pedestrian jam by applying the reductive perturbation method. The phase diagram indicates that the phase transition occurs among the freely moving phase, the coexisting phase, and the uniformly congested phase below the critical point \(a_c\) . Furthermore, the analytical results show that the visual field effect plays an important role in jamming transition. To take into account the visual information about the motion of more pedestrian in front can improve efficiently the stability of pedestrian system. In addition, the numerical simulations are in accordance with the theoretical analysis. 相似文献
994.
Dr. Xiao‐Feng Wang Xiu‐Lian Zhang Xin Zhou Dr. Jun Li Yun‐Fei Kuang Ji‐Hao Chen 《无机化学与普通化学杂志》2012,638(9):1365-1369
A two dimensional coordination polymer with pseudo‐Kagomé net [Cu3(btc)2(NH3)8(H2O)] was prepared from Cu(NO3)2 · 3H2O and 1, 3, 5‐benzenetricarboxylic acid (btc) in ammonia aqua solution and was structurally characterized by X‐ray diffraction. The magnetic susceptibility measurements, measured from 2 to 300 K, revealed a weak anti‐ferromagnetic interaction between the CuII ions via the btc ligands. 相似文献
995.
Yinjie Kuang Bohua Wu Dan Hu Xiaohua Zhang Jinhua Chen 《Journal of Solid State Electrochemistry》2012,16(2):759-766
A facile method for one-pot synthesis of highly dispersed palladium nanoparticles on acetylenic ionic liquid polymer functionalized
carbon nanotubes (PdNPs-AILP-CNTs) has been developed in this paper. The nanohybrids are prepared by polymerization of acetylenic
ionic liquid monomers catalyzed by PdCl2, which is further reduced to PdNPs by NaBH4 on CNTs in one pot and characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis,
and transmission electron microscopy. The electrocatalytic oxidation of glucose on the PdNPs-AILP-CNT nanohybrids is also
investigated by cyclic voltammetry and chronoamperometry. The results show that the PdNPs with a particle size of around 3.5 nm
disperse uniformly on CNTs, and PdNPs-AILP-CNT nanohybrids have good electrocatalytic performance for glucose oxidation. 相似文献
996.
Kuang Y Cui Y Zhang Y Yu Y Zhang X Chen J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(5):1522-1527
Carbon nanotubes (CNTs) were non-covalently functionalized by 1-pyrenecarboxaldehyde (PCA) via π-π stacking interactions. PCA not only acts as the reductant for the deposition of PtRu nanoparticles, but the oxidation product of PCA can also effectively anchor and stabilize the in-situ-produced PtRu?NPs on the surface of CNTs. Transmission electron microscopy demonstrates that PtRu?NPs are uniformly dispersed on the surface of CNTs with small particles sizes of about 1.7 nm. The obtained PtRu-NP/CNT composites have higher electrochemical surface areas, electrocatalytic activities, and better stability towards methanol oxidation compared to PtRu?NPs supported on pristine CNTs. 相似文献
997.
The structural evolution and bonding of a series of early transition-metal oxide clusters, V(n)O(q) (n = 3-9, q = 0,-1), have been investigated with the aid of previous photoelectron spectroscopy (PES) and theoretical calculations. For each vanadium monoxide cluster, many low-lying isomers are generated using the Saunders "Kick" global minimum stochastic search method. Theoretical electron detachment energies (both vertical and adiabatic) were compared with the experimental measurements to verify the ground states of the vanadium monoxide clusters obtained from the DFT calculations. The results demonstrate that the combination of photoelectron spectroscopy experiments and DFT calculation is not only powerful for obtaining the electronic and atomic structures of size-selected clusters, but also valuable in resolving structurally and energetically close isomers. The second difference energies and adsorption energies as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. The adsorption energies of one O atom on the anionic (6.64 → 8.16 eV) and neutral (6.41 → 8.13 eV) host vanadium clusters are shown to be surprisingly high, suggesting strong capabilities to activate O by structural defects in vanadium oxides. 相似文献
998.
BX Lei QP Luo XY Yu WQ Wu CY Su DB Kuang 《Physical chemistry chemical physics : PCCP》2012,14(38):13175-13179
A novel hierarchical TiO(2) flower consisting of anatase TiO(2) nanotubes on a Ti foil substrate has been prepared via a mild hydrothermal reaction of TiO(2) nanoparticles/Ti foil. The photovoltaic performance of DSSC based on hierarchical TiO(2) flowers/Ti (7.2%) is much higher than that of TiO(2) nanoparticle/Ti (6.63%) because of its superior light scattering ability and fast electron transport. Moreover, full flexible DSSC based on the novel hierarchical TiO(2) flowers/Ti foil photoelectrode and electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT) on indium tin oxide-coated poly(ethylene terephthalate) (ITO-PET) counter electrode shows a significant power conversion efficiency of 6.26%, accompanying a short-circuit current density of 11.96 mA cm(-2), an open-circuit voltage of 761 mV and a fill factor of 0.69. 相似文献
999.
匡继昌 《数学物理学报(A辑)》2013,33(1):1-5
基于利用一个积分恒等式的新技巧,建立了赋范线性空间中新的Hilbert型积分不等式.这些新的结果包含了n维欧氏空间中n重积分的Hilbert型积分不等式作为其特殊情形. 相似文献
1000.
同步辐射光源中的高次谐波会使透射光栅衍射效率标定精度变差。为了校正光源中的高次谐波对透射光栅衍射效率标定的影响,提出了一种光源存在弱谐波情况下的透射光栅衍射效率标定方法,通过使用谐波X射线的衍射效率修正基波衍射效率标定中谐波的影响,从而得到更为准确的透射光栅衍射效率。使用该标定方法在北京同步辐射光源上开展了透射光栅相对衍射效率标定工作。实验结果表明:在100~800eV存在高次谐波能段,修正后透射光栅一级与零级的相对衍射效率与理论模拟结果吻合较好,修正后光栅二级与一级的相对衍射效率更接近理论模拟结果,但与理论模拟结果仍有较大偏差,该偏差主要来源光栅较弱的二级衍射。 相似文献