全文获取类型
收费全文 | 23013篇 |
免费 | 3332篇 |
国内免费 | 2454篇 |
专业分类
化学 | 16180篇 |
晶体学 | 277篇 |
力学 | 1355篇 |
综合类 | 190篇 |
数学 | 2299篇 |
物理学 | 8498篇 |
出版年
2024年 | 67篇 |
2023年 | 429篇 |
2022年 | 744篇 |
2021年 | 846篇 |
2020年 | 852篇 |
2019年 | 843篇 |
2018年 | 716篇 |
2017年 | 741篇 |
2016年 | 1016篇 |
2015年 | 1042篇 |
2014年 | 1173篇 |
2013年 | 1613篇 |
2012年 | 1870篇 |
2011年 | 1997篇 |
2010年 | 1302篇 |
2009年 | 1268篇 |
2008年 | 1464篇 |
2007年 | 1353篇 |
2006年 | 1224篇 |
2005年 | 972篇 |
2004年 | 775篇 |
2003年 | 660篇 |
2002年 | 633篇 |
2001年 | 461篇 |
2000年 | 455篇 |
1999年 | 484篇 |
1998年 | 423篇 |
1997年 | 426篇 |
1996年 | 465篇 |
1995年 | 367篇 |
1994年 | 381篇 |
1993年 | 272篇 |
1992年 | 255篇 |
1991年 | 233篇 |
1990年 | 167篇 |
1989年 | 129篇 |
1988年 | 118篇 |
1987年 | 97篇 |
1986年 | 95篇 |
1985年 | 85篇 |
1984年 | 58篇 |
1983年 | 49篇 |
1982年 | 39篇 |
1981年 | 28篇 |
1980年 | 31篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 7篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
{Nb288O768(OH)48(CO3)12}: A Macromolecular Polyoxometalate with Close to 300 Niobium Atoms 下载免费PDF全文
Yan‐Lan Wu Dr. Xin‐Xiong Li Yan‐Jie Qi Hao Yu Lu Jin Prof. Dr. Shou‐Tian Zheng 《Angewandte Chemie (International ed. in English)》2018,57(28):8572-8576
A protein‐sized (ca. 4.2×4.2×3.6 nm3) non‐biologically derived molecule {Nb288O768(OH)48(CO3)12} ( Nb288 ) containing up to 288 niobium atoms has been obtained, which is by far the largest and the highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb288 is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb288 can be described as a giant windmill‐like cluster aggregate of six nanoscale high‐nuclearity PONb units {Nb47O128(OH)6(CO3)2} ( Nb47 ) joined together by six additional Nb ions. Interestingly, the 47‐nuclearity Nb47 units generated in situ can be isolated and bridged by copper complexes to form an inorganic–organic hybrid three‐dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb47 cluster also provides a new type of topology to very limited family of Nb‐O clusters. 相似文献
992.
Dr. Hong Wang Dr. Lu Wang Dr. Qiang Wang Shuyang Ye Dr. Wei Sun Yue Shao Zhiping Jiang Dr. Qiao Qiao Dr. Yimei Zhu Prof. Pengfei Song Dr. Debao Li Prof. Le He Prof. Xiaohong Zhang Prof. Jiayin Yuan Prof. Tom Wu Prof. Geoffrey A. Ozin 《Angewandte Chemie (International ed. in English)》2018,57(38):12360-12364
Ammonia, a key precursor for fertilizer production, convenient hydrogen carrier, and emerging clean fuel, plays a pivotal role in sustaining life on Earth. Currently, the main route for NH3 synthesis is by the heterogeneous catalytic Haber–Bosch process (N2+3 H2→2 NH3), which proceeds under extreme conditions of temperature and pressure with a very large carbon footprint. Herein we report that a pristine nitrogen‐doped nanoporous graphitic carbon membrane (NCM) can electrochemically convert N2 into NH3 in an acidic aqueous solution under ambient conditions. The Faradaic efficiency and rate of production of NH3 on the NCM electrode reach 5.2 % and 0.08 g m?2 h?1, respectively. Functionalization of the NCM with Au nanoparticles dramatically enhances these performance metrics to 22 % and 0.36 g m?2 h?1, respectively. As this system offers the potential to be scaled to industrial levels it is highly likely that it might displace the century‐old Haber–Bosch process. 相似文献
993.
In this work, P2-Na0.6[Mg(II)0.3Mn(IV)0.7] O2 with inoxidizable elements (Na+, Mg2+ and Mn4+) except O2- was synthesized and investigated, which exhibited high reversible capacity (~210 mAh/g) with highly reversible ARR characteristic. 相似文献
994.
Shengqiang?LiEmail author Xu?Liu Shuchao?Pang Ruojun?Lu Yonghua?Liu MeiHong?Fan Zhijie?Jia Hongxue?Bai 《Mikrochimica acta》2018,185(9):433
An electrochemical biosensor for determination of DNA is described that is based on the reaction of regulated DNA (reg-DNA) first with substrated DNA (subs-DNA) to form a reaction intermediate. The intermediate binds target DNA (T) by hybridization and initiates a branch migration leading to the production of complex of substrated DNA and target DNA (TC). Once TC is produced, it reacts with assisted DNA (ass-DNA) through a toehold exchange mechanism, yielding the product complex of substrated DNA and assisted DNA (CS). The target is then released back into the solution and and catalyzes the next cycle of toehold-exchange with the reaction intermediate of substrated DNA and regulated DNA (CPR). Unlike in a conventional DNA toehold that is hardwired with the branch migration domain, the allosteric DNA toehold is designed into a reg-DNA which is independent of the branch migration domain. Under the optimal experimental conditions and at a working potential as low as 0.18 V, response to DNA is linear in the 1 fM to 1000 pM concentration range, and the detection limit is 0.83 fM. The assay is highly specific and can discriminate target DNA even from a single-base mismatch. It was applied to the analysis of DNA spiked plasma samples. 相似文献
995.
使用溶剂热合成法,以p-bitmb配体(1,4-二(1-咪唑基-亚甲基)-2,3,5,6-四甲基苯)与[(η6-cymene)Os(μ-Cl)Cl]2或[(η6-bip)Os(μ-Cl)Cl]2为原料,合成了2种单核芳基锇配合物,并利用核磁、质谱、元素分析和X射线单晶衍射等手段对配合物进行了表征。配合物1属于单斜晶系,P21/c空间群,为一个单核锇的结构。中心锇原子与2个配体p-bitmb上的氮原子以及氯原子进行配位,2个配体的另一个咪唑基团通过一个亚甲基碳原子进行连接形成咪唑嗡离子,形成一个类似"碗"状的结构。一个氯离子通过氢键装载在结构的空腔内。利用核磁共振氢谱研究了结构中亚甲基的来源,并研究了配合物在缓冲溶液中的稳定性。用紫外吸收光谱、圆二色谱以及粘度法研究了配合物与DNA的相互作用,结果表明,配合物中的亚甲基来自于溶剂二氯甲烷。配合物以嵌入的方式与CT-DNA相互作用,结合常数分别为3.222×10~4 L·mol-1 (1)和1.53×10~4 L·mol-1 (2),同时配合物会减弱DNA的碱基堆积作用并可以使DNA发生解旋。 相似文献
996.
用中和法合成了氨基酸离子液体(AAIL)1-己基-3-甲基苏氨酸盐[C6mim][Thr],并用核磁共振氢谱(1H NMR)和核磁共振碳谱(13C NMR)进行了表征。以苯甲酸为参考物质,用恒温热重法确定了AAIL[C6mim][Thr]的蒸汽压和在平均温度下(Tav= 438.15 K)的蒸发焓(ΔglHm? (Tav) =128.5 ± 6.0 kJ·mol-1)。利用Verevkin等人提出的方法计算得到AAIL[C6mim][Thr]气态和液态的恒压热容差(ΔglCpm? = -70.8 J·K-1·mol-1),进而计算了不同温度的蒸发焓,其中参考温度(298.15 K)下的蒸发焓ΔglHm? (298.15 K) = 138.4 kJ·mol-1,只比应用我们提出的蒸发焓理论模型估算值大1.6 kJ·mol-1,小于恒温热重法的实验误差3.0 kJ·mol-1,说明这个蒸发焓的理论模型有一定的合理性。借助Clausius-Clapeyron方程估算了AAIL[C6mim][Thr]的假想的正常沸点Tb= 522.07 K,以及沸点的蒸发熵ΔglSm? (Tb) = 228.5 J·K-1·mol-1,进一步得到了不同温度的蒸发熵和蒸发自由能ΔglGm? (T),其结果表明蒸发自由能随着温度的上升而减小,达到沸点温度Tb时变为零,而蒸发熵则随着温度上升而增大,是AAIL[C6mim][Thr]蒸发过程的驱动力。 相似文献
997.
998.
Griffiths G. Keegan E. Young E. Wotherspoon A. Palmer T. Lu K. Davis J. Alexander J. Jolly L. Nevers N. Delaunay F. Collins J. M. Dimayuga I. Bergeron A. Samuleev P. Dai Z. Holliday K. Robel M. Knight K. 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(2):365-378
Journal of Radioanalytical and Nuclear Chemistry - Physical characterization is one of the most broad and important categories of techniques to apply in a nuclear forensic examination. Physical... 相似文献
999.
The fluorescence quenching of Rhodamine 6G (R6G) by graphene oxide (GO) was interrogated by R6G fluorescence measurements using a set of controlled GO samples with varied C/O ratios as the quencher.The carbonyl groups on the GO nanosheet turned to play a dominant role in quenching the R6G fluorescence.The quenching in the static regime can be described by the "sphere of action" model.The significant absorption of the R6G fluorescence by the ground-state complex formed between R6G and GO was identified to be responsible for the static quenching.This work offers helpful insights into the fluorescence quenching mechanisms in the R6G/GO system. 相似文献
1000.
Direct Observation of Transition Metal Dichalcogenides in Liquid with Scanning Tunneling Microscopy 下载免费PDF全文
Ze Wang Ji-hao Wang Wei-feng Ge Wen-jie Meng Jing Zhang Qi-yuan Feng Yu-bin Hou Qing-you Lu 《化学物理学报(中文版)》2018,31(6):767-771
We present atomic-resolution images of TiSe\begin{document}$_2$\end{document} , MoTe\begin{document}$_2$\end{document} and TaS\begin{document}$_2$\end{document} single crystals in liquid condition using our home-built scanning tunneling microscopy (STM). By facilely cleaving of single crystals in liquid, we were able to keep the fresh surface not oxidized within a few hours. Using the high-stable home-built STM, we have obtained atomic resolution images of TiSe\begin{document}$_2$\end{document} accompanied with the single atom defects as well as the triangle defects in solution for the first time. Besides, the superstructure of MoTe\begin{document}$_2$\end{document} and hexagonal charge-density wave domain structure in nearly commensurate phase of TaS\begin{document}$_2$\end{document} were also obtained at room temperature (295 K). Our results provide a more efficient method in investigating the lively surface of transition metal dichalcogenides. Besides, the high stable liquid-phase STM will support the further investigations in liquid-phase catalysis or electrochemistry. 相似文献