全文获取类型
收费全文 | 10628篇 |
免费 | 1916篇 |
国内免费 | 1668篇 |
专业分类
化学 | 8010篇 |
晶体学 | 144篇 |
力学 | 541篇 |
综合类 | 123篇 |
数学 | 1294篇 |
物理学 | 4100篇 |
出版年
2024年 | 45篇 |
2023年 | 233篇 |
2022年 | 419篇 |
2021年 | 455篇 |
2020年 | 479篇 |
2019年 | 486篇 |
2018年 | 443篇 |
2017年 | 414篇 |
2016年 | 518篇 |
2015年 | 637篇 |
2014年 | 662篇 |
2013年 | 765篇 |
2012年 | 961篇 |
2011年 | 1030篇 |
2010年 | 751篇 |
2009年 | 644篇 |
2008年 | 765篇 |
2007年 | 638篇 |
2006年 | 560篇 |
2005年 | 492篇 |
2004年 | 373篇 |
2003年 | 345篇 |
2002年 | 426篇 |
2001年 | 299篇 |
2000年 | 194篇 |
1999年 | 199篇 |
1998年 | 118篇 |
1997年 | 117篇 |
1996年 | 139篇 |
1995年 | 135篇 |
1994年 | 99篇 |
1993年 | 73篇 |
1992年 | 57篇 |
1991年 | 60篇 |
1990年 | 54篇 |
1989年 | 35篇 |
1988年 | 22篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1965年 | 3篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
991.
Ren Ren Chao‐Jun Chen Xian‐Xian Liu Hui‐Ming Ge Ren‐Xiang Tan Rui‐Hua Jiao 《Helvetica chimica acta》2015,98(10):1435-1441
Three new simple trichothecenes, 15‐acetyltrichoverrol B ( 3 ), 13′‐acetyltrichoverrin B ( 5 ), and 6′‐dehydroxytrichoverrin B ( 6 ), along with five known trichothecenes trichodermadienediol B ( 1 ), trichoverrol B ( 2 ), trichoverrin B ( 4 ), and roridins A ( 7 ) and D ( 8 ), have been isolated from the liquid culture of Myrothecium roridum (strain no. QB‐1). The structures of the new compounds were established by comprehensive analysis of 1D‐ and 2D‐NMR data. All the compounds were evaluated for antifungal activity, only compounds 7 and 8 showed significant antifungal activity against the tested fungi (MIC ranged from 10 to 5 μg/ml). 相似文献
992.
Theoretical prediction of the host–guest interactions between novel photoresponsive nanorings and C60: A strategy for facile encapsulation and release of fullerene 下载免费PDF全文
Kun Yuan Jing‐Shuang Dang Yi‐Jun Guo Xiang Zhao 《Journal of computational chemistry》2015,36(8):518-528
A series of photoresponsive‐group‐containing nanorings hosts with 12~14 Å in diameter is designed by introducing different number of azo groups as the structural composition units. And the host–guest interactions between fullerene C60 and those nanoring hosts were investigated theoretically at M06‐2X/6‐31G(d)//M06‐L/MIDI! and wB97X‐D/6‐31G(d) levels. Analysis on geometrical characteristics and host–guest binding energies revealed that the designed nanoring molecule (labeled as 7 ) which is composed by seven azo groups and seven phenyls is the most feasible host for encapsulation of C60 guest among all candidates. Moreover, inferring from the simulated UV‐vis‐NIR spectroscopy, the C60 guest could be facilely released from the cavity of the host 7 via configuration transformation between trans‐form and cis‐form of the host under the 563 nm photoirradiation. Additionally, the frontier orbital features, weak interaction regions, infrared, and NMR spectra of the C60@7 host–guest complex have also been investigated theoretically. © 2015 Wiley Periodicals, Inc. 相似文献
993.
Multiple‐Stimulus‐Responsive Supramolecular Gels of Two Components and Dual Chiroptical Switches 下载免费PDF全文
Dr. Wangen Miao Dr. Long Qin Dr. Dong Yang Dr. Xue Jin Prof. Dr. Minghua Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1064-1072
A new class of L ‐glutamic gelators, LG12(CH2)nCOOH, containing different lengths of methylene spacer were synthesized. It was found that the gelation ability of these compounds themselves was very weak. However, when another compound, p‐xylylenediamine (XEA), was introduced, the gelation ability was improved greatly. In particular, LG12(CH2)10COOH showed super‐gelation ability in the presence of XEA, which could immobilize almost all of the solvents except methanol. Moreover, the formed supramolecular gels even could be molded. Interestingly, some supramolecular gels of LG12(CH2)nCOOH and XEA could respond to multiple stimuli, such as heating, shaking, sonication, and acid/base. The studies of CD spectra suggested that the supramolecular chirality induced by self‐assembled chiral gelator molecules in gels could be tuned by the length of methylene spacer. In addition, the supramolecular chirality could be regulated as on/off by heating–cooling or external NH3/HCl. This would facilitate the development of dual chiroptical switches by temperature and acid/base. 相似文献
994.
Dr. Li Xu Xiang Chen Jingheng Wu Jinquan Wang Prof. Liangnian Ji Prof. Dr. Hui Chao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):4008-4020
A series of dinuclear ruthenium(II) complexes were synthesised, and the complexes were determined to be new highly selective compounds for binding to telomeric G‐quadruplex DNA. The interactions of these complexes with telomeric G‐quadruplex DNA were studied by using circular dichroism (CD) spectroscopy, fluorescence resonance energy transfer (FRET) melting assays, isothermal titration calorimetry (ITC) and molecular modelling. The results showed that the complexes 1 , 2 and 4 induced and stabilised the formation of antiparallel G‐quadruplexes of telomeric DNA in the absence of salt or in the presence of 100 mM K+‐containing buffer. Furthermore, complexes 1 and 2 strongly bind to and effectively stabilise the telomeric G‐quadruplex structure and have significant selectivity for G‐quadruplex over duplex DNA. In comparison, complex 3 had a much lesser effect on the G‐quadruplex, suggesting that possession of a suitably sized plane for good π–π stacking with the G‐quadruplets is essential for the interaction of the dinuclear ruthenium(II) complexes with the G‐quadruplex. Moreover, telomerase inhibition by the four complexes and their cellular effects were studied, and complex 1 was determined to be the most promising inhibitor of both telomerase and HeLa cell proliferation. 相似文献
995.
Dr. Chun Zhang Zhen Wang Liangxiao Tan Tian‐Long Zhai Dr. Sheng Wang Prof. Bien Tan Prof. Yan‐Song Zheng Prof. Xiang‐Liang Yang Prof. Hui‐Bi Xu 《Angewandte Chemie (International ed. in English)》2015,54(32):9244-9248
A quadrangular prismatic tricyclooxacalixarene cage 1 based on tetraphenylethylene (TPE) was efficiently synthesized by a one‐pot SNAr condensation reaction. As a result of the porous internal structure in the solid state, cage 1 exhibited a good CO2 uptake capacity of 12.5 wt % and a high selectivity for CO2 over N2 adsorption of 80 (273 K, 1 bar) with a BET surface area of 432 m2 g?1. Formation of cage 1 led to the fluorescence of TPE being switched on in solution. The system was employed as a single‐molecule platform to study the mechanism of aggregation‐induced emission (AIE) by examining the restriction of intramolecular rotation (RIR). 相似文献
996.
Cooperative Crystallization of Heterometallic Indium–Chromium Metal–Organic Polyhedra and Their Fast Proton Conductivity 下载免费PDF全文
Dr. Quan‐Guo Zhai Chengyu Mao Dr. Xiang Zhao Dr. Qipu Lin Fei Bu Xitong Chen Prof. Dr. Xianhui Bu Prof. Dr. Pingyun Feng 《Angewandte Chemie (International ed. in English)》2015,54(27):7886-7890
Metal–organic polyhedra (MOPs) or frameworks (MOFs) based on Cr3+ are notoriously difficult to synthesize, especially as crystals large enough to be suitable for characterization of the structure or properties. It is now shown that the co‐existence of In3+ and Cr3+ induces a rapid crystal growth of large single crystals of heterometallic In‐Cr‐MOPs with the [M8L12] (M=In/Cr, L=dinegative 4,5‐imidazole‐dicarboxylate) cubane‐like structure. With a high concentration of protons from 12 carboxyl groups decorating every edge of the cube and an extensive H‐bonded network between cubes and surrounding H2O molecules, the newly synthesized In‐Cr‐MOPs exhibit an exceptionally high proton conductivity (up to 5.8×10?2 S cm?1 at 22.5 °C and 98 % relative humidity, single crystal). 相似文献
997.
Prof. Dr. Suning Wang Deng‐Tao Yang Jiasheng Lu Hiroyuki Shimogawa Prof. Dr. Shaolong Gong Xiang Wang Soren K. Mellerup Prof. Dr. Atsushi Wakamiya Dr. Yi‐Lu Chang Prof. Dr. Chuluo Yang Prof. Dr. Zheng‐Hong Lu 《Angewandte Chemie (International ed. in English)》2015,54(50):15074-15078
New BN‐heterocyclic compounds have been found to undergo double arene photoelimination, forming rare yellow fluorescent BN‐pyrenes that contain two B? N units. Most significant is the discovery that the double arene elimination can also be driven by excitons generated electrically within electroluminescent (EL) devices, enabling the in situ solid‐state conversion of BN‐heterocycles to BN‐pyrenes and the use of BN‐pyrenes as emitters for EL devices. The in situ exciton‐driven elimination (EDE) phenomenon has also been observed for other BN‐heterocycles. 相似文献
998.
采用玻璃微米管支撑的液/液界面通过循环伏安法(CV)研究了二环己基-18冠6(DCH18C6)加速Sr2+在水/1,2-二氯乙烷(W/DCE)界面上的转移反应,考察了DCH18C6加速Sr2+在W/DCE界面转移的影响因素,如DCH18C6和Sr2+浓度等,并求算其络合物的稳定常数。实验结果表明,Sr2+与DCH18C6发生的是一个1:1的扩散控制的界面络合转移过程,其络合常数β为5.31×1023。本研究可为理解溶剂萃取Sr2+行为提供基础理论数据。 相似文献
999.
本文研究了快速测定高温合金中5种非金属元素(As、B、P、Se、Si)的分析方法,以满足高温合金行业对非金属元素检测的需求。利用王水和高氯酸对高温合金进行酸溶解,并系统研究了基体元素和共存元素对分析元素谱线的光谱干扰情况,同时进行了分析谱线的选择。5种非金属元素的检出限在5.5 ~ 11.9 ug/ml,5次数据的相对标准偏差(RSD,n=5)为0.9 % ~ 7 %,各元素的回收率在96 % ~ 102 %之间,该方法适用于高温合金中非金属元素的测定。 相似文献
1000.
采用水热法制备了一系列Bi2WO6/Zn O异质结光催化剂,并对其进行X射线衍射(XRD)、紫外-可见光谱(UV-Vis DRS)、扫描电镜(SEM)、光电子能谱(EDS)等手段对其结构性质进行了表征。在含酚废水的液相反应体系中,研究了异质结Bi2WO6/Zn O复合光催化剂光催化降解苯酚的性能。结果表明,Bi2WO6/Zn O异质结的形成可以有效的抑制光生电子和空穴对的结合,使其光催化活性明显优于纯的Zn O和Bi2WO6;另外,异质结型Bi2WO6/Zn O复合光催化剂的表面OH·自由基更有利于光催化活性的提高。当Bi2WO6复合量为4wt%时,异质结Bi2WO6/Zn O复合光催化剂光催化降解苯酚的效果最佳。 相似文献