全文获取类型
收费全文 | 968篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
化学 | 543篇 |
晶体学 | 9篇 |
力学 | 29篇 |
数学 | 59篇 |
物理学 | 371篇 |
出版年
2023年 | 18篇 |
2022年 | 15篇 |
2021年 | 27篇 |
2020年 | 35篇 |
2019年 | 33篇 |
2018年 | 28篇 |
2017年 | 31篇 |
2016年 | 34篇 |
2015年 | 23篇 |
2014年 | 35篇 |
2013年 | 54篇 |
2012年 | 42篇 |
2011年 | 52篇 |
2010年 | 42篇 |
2009年 | 31篇 |
2008年 | 46篇 |
2007年 | 47篇 |
2006年 | 48篇 |
2005年 | 39篇 |
2004年 | 39篇 |
2003年 | 26篇 |
2002年 | 17篇 |
2001年 | 23篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1933年 | 3篇 |
排序方式: 共有1011条查询结果,搜索用时 94 毫秒
41.
42.
43.
44.
Efficient sunlight-responsive BiOBr–CoWO4 heterostructured nanocomposite photocatalysts were prepared via a chemical precipitation route at 100°C in 4 hours. The prepared BiOBr–CoWO4 heterostructures were characterized for phase identification, chemical composition, surface morphology, optical properties and surface area using various techniques. The X-ray diffraction pattern of the BiOBr–CoWO4 nanocomposite was composed of diffraction peaks equivalent to both the tetragonal phase of BiOBr and the monoclinic phase of CoWO4 nanoparticles. X-ray photoelectron spectral study of the BiOBr–CoWO4 nanocomposite revealed orbitals of both BiOBr and CoWO4 compounds. Transmission electron microscopy images revealed that spherical particles of CoWO4 (20–25 nm) were dispersed on the surface of BiOBr. UV–visible–near-infrared spectral study of the BiOBr–CoWO4 nanocomposite showed good visible-light absorption. Among the manufactured materials, BiOBr–CoWO4-2 nanocomposite showed better charge carrier separation efficiency, as demonstrated by photoluminescence and time-resolved fluorescence. To study the practical utility of the prepared materials, their photocatalytic capability was examined for the degradation of rhodamine B (RhB) aqueous solution under sunlight irradiation. The photodegradation results showed that BiOBr–CoWO4-2 nanocomposite degraded 98.69% RhB solution and the degradation constant was 0.067 min−1, which was 5.6 and 22.5 times larger than that of pure BiOBr and CoWO4 nanoparticles, respectively, after 60 minutes of sunlight irradiation. The superior photoactivity was facilitated by electron–hole pair separation and transfer driven by the heterostructure interface between BiOBr particles and CoWO4 nanoparticles. The removal of RhB was initiated by photogenerated h+, O2• − and •OH reactive species based on the scavenger effect. 相似文献
45.
Singh Swati Bawitlung Laldingngheti Singh Munmun Kumar Chauhan Amit Padalia Rajendra Chandra Pal Anirban Verma Ram Swaroop 《Chemistry of Natural Compounds》2022,58(1):161-162
Chemistry of Natural Compounds - 相似文献
46.
Basak Anirban Sadhu Arindam Das Kunal Sharma Kapil K. 《International Journal of Theoretical Physics》2019,58(9):3158-3179
In this paper, an attempt is made to present a method of quantum cost minimization or optimization technique for quantum reversible circuits using proposed merger rules in Exclusive Sum of Product (ESOP) method. These modified ESOP methods are used to minimize the quantum circuits. We found that the quantum cost is drastically decreased than the previous ESOP method. It will be easy to find the quantum cost and quantum gate optimized quantum circuits implementation. It will also reduce quantum error while the quantum circuit is executed in real quantum processor.
相似文献47.
48.
49.
50.
Dr. Dipanwita Das Hemlata Agarwala Dr. Abhishek Dutta Chowdhury Tuhin Patra Dr. Shaikh M. Mobin Prof. Dr. Biprajit Sarkar Prof. Dr. Wolfgang Kaim Prof. Dr. Goutam Kumar Lahiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7384-7394
The complex series [Ru(pap)(Q)2]n ([ 1 ]n–[ 4 ]n; n=+2, +1, 0, ?1, ?2) contains four redox non‐innocent entities: one ruthenium ion, 2‐phenylazopyridine (pap), and two o‐iminoquinone moieties, Q=3,5‐di‐tert‐butyl‐N‐aryl‐1,2‐benzoquinonemonoimine (aryl=C6H5 ( 1+ ); m‐(Cl)2C6H3 ( 2+ ); m‐(OCH3)2C6H3 ( 3+ ); m‐(tBu)2C6H3 ( 4 +)). A crystal structure determination of the representative compound, [ 1 ]ClO4, established the crystallization of the ctt‐isomeric form, that is, cis and trans with respect to the mutual orientations of O and N donors of two Q ligands, and the coordinating azo N atom trans to the O donor of Q. The sensitive C? O (average: 1.299(3) Å), C? N (average: 1.346(4) Å) and intra‐ring C? C (meta; average: 1.373(4) Å) bond lengths of the coordinated iminoquinone moieties in corroboration with the N?N length (1.292(3) Å) of pap in 1 + establish [RuIII(pap0)(Q.?)2]+ as the most appropriate electronic structural form. The coupling of three spins from one low‐spin ruthenium(III) (t2g5) and two Q.? radicals in 1 +– 4 + gives a ground state with one unpaired electron on Q.?, as evident from g=1.995 radical‐type EPR signals for 1 +– 4 +. Accordingly, the DFT‐calculated Mulliken spin densities of 1 + (1.152 for two Q, Ru: ?0.179, pap: 0.031) confirm Q‐based spin. Complex ions 1 +– 4 + exhibit two near‐IR absorption bands at about λ=2000 and 920 nm in addition to intense multiple transitions covering the visible to UV regions; compounds [ 1 ]ClO4–[ 4 ]ClO4 undergo one oxidation and three separate reduction processes within ±2.0 V versus SCE. The crystal structure of the neutral (one‐electron reduced) state ( 2 ) was determined to show metal‐based reduction and an EPR signal at g=1.996. The electronic transitions of the complexes 1 n– 4 n (n=+2, +1, 0, ?1, ?2) in the UV, visible, and NIR regions, as determined by using spectroelectrochemistry, have been analyzed by TD‐DFT calculations and reveal significant low‐energy absorbance (λmax>1000 nm) for cations, anions, and neutral forms. The experimental studies in combination with DFT calculations suggest the dominant valence configurations of 1 n– 4 n in the accessible redox states to be [RuIII(pap0)(Q.?)(Q0)]2+ ( 1 2+– 4 2+)→[RuIII(pap0)(Q.?)2]+ ( 1 +– 4 +)→[RuII(pap0)(Q.?)2] ( 1 – 4 )→[RuII(pap.?)(Q.?)2]? ( 1 ?– 4 ?)→[RuIII(pap.?)(Q2?)2]2? ( 1 2?– 4 2?). 相似文献