全文获取类型
收费全文 | 11173篇 |
免费 | 318篇 |
国内免费 | 77篇 |
专业分类
化学 | 7940篇 |
晶体学 | 115篇 |
力学 | 227篇 |
数学 | 1504篇 |
物理学 | 1782篇 |
出版年
2023年 | 61篇 |
2021年 | 103篇 |
2020年 | 157篇 |
2019年 | 146篇 |
2018年 | 120篇 |
2017年 | 108篇 |
2016年 | 221篇 |
2015年 | 226篇 |
2014年 | 282篇 |
2013年 | 504篇 |
2012年 | 664篇 |
2011年 | 855篇 |
2010年 | 418篇 |
2009年 | 355篇 |
2008年 | 769篇 |
2007年 | 775篇 |
2006年 | 811篇 |
2005年 | 825篇 |
2004年 | 720篇 |
2003年 | 588篇 |
2002年 | 498篇 |
2001年 | 116篇 |
2000年 | 106篇 |
1999年 | 88篇 |
1998年 | 102篇 |
1997年 | 145篇 |
1996年 | 152篇 |
1995年 | 100篇 |
1994年 | 109篇 |
1993年 | 111篇 |
1992年 | 86篇 |
1991年 | 78篇 |
1990年 | 53篇 |
1989年 | 58篇 |
1988年 | 56篇 |
1987年 | 63篇 |
1986年 | 49篇 |
1985年 | 93篇 |
1984年 | 90篇 |
1983年 | 62篇 |
1982年 | 68篇 |
1981年 | 81篇 |
1980年 | 81篇 |
1979年 | 61篇 |
1978年 | 49篇 |
1977年 | 43篇 |
1976年 | 32篇 |
1975年 | 38篇 |
1974年 | 30篇 |
1973年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Dr. Mark R. Ringenberg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(10):2396-2406
Ligands with 1,1′-bis(donor)ferrocene motif are capable of a wide range of binding modes, including the trans chelation mode in which there is a Fe−M interaction (κ3-D,Fe,D), in the form of a dative Fe→TM bond (TM=transition metal). This Minireview will explore the nature of this Fe–TM interaction thorough select examples as well as how to characterize a Fe→TM dative bond using physical, computational, and spectroscopic techniques. 相似文献
102.
Prof. Richard D. Adams Dr. Poonam Dhull Matthew Pennachio Prof. Marina A. Petrukhina Dr. Mark D. Smith 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(16):4234-4239
The reaction of Re2(CO)8(μ-C6H5)(μ-H), 1 with corannulene (C20H10) yielded the product Re2(CO)8(μ-H)(μ-η2-1,2-C20H9), 2 (65 % yield) containing a Re2 metalated corannulene ligand formed by loss of benzene from 1 and the activation of one of the CH bonds of the nonplanar corannulene molecule by an oxidative-addition to 1 . The corannulenyl ligand has adopted a bridging η2-σ+π coordination to the Re2(CO)8 grouping. Compound 2 reacts with a second equivalent of 1 to yield three isomeric doubly metalated corannulene products: Re2(CO)8(μ-H)(μ-η2-1,2-μ-η2-10,11-C20H8)Re2(CO)8(μ-H), 3 (35 % yield), Re2(CO)8(μ-H)(μ-η2-2,1-μ-η2-10,11-C20H8)Re2(CO)8(μ-H), 4 (12 % yield), and Re2(CO)8(μ-H)(μ-η2-1,2-μ-η2-11,10-C20H8)Re2(CO)8(μ-H), 5 (12 % yield), by a second CH activation on a second rim double bond on the corannulene molecule. The isomers differ by the relative orientations of the coordinated Re2(CO)8(μ-H) groupings. All new products were characterized structurally by single crystal X-ray diffraction analysis. 相似文献
103.
Benjamin H. Strudwick Mark A. J. Koenis Hans J. Sanders Valentin P. Nicu Sander Woutersen Prof. Wybren Jan Buma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12560-12566
Vibrational circular dichroism (VCD) studies are reported on a chiral compound in which a fullerene C60 moiety is used as an electron acceptor and local VCD amplifier for an alanine-based peptide chain. Four redox states are investigated in this study, of which three are reduced species that possess low-lying electronic states as confirmed by UV/Vis spectroelectrochemistry. VCD measurements in combination with (TD)DFT calculations are used to investigate (i) how the low-lying electronic states of the reduced species modulate the amplification of VCD signals, (ii) how this amplification depends on the distance between oscillator and amplifier, and (iii) how the spatial extent of the amplifier influences amplification. These results pave the way for further development of tailored molecular VCD amplifiers. 相似文献
104.
Jillian S. K. Clark Michael J. Ferguson Robert McDonald Mark Stradiotto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6457-6461
Base‐metal catalysts capable of enabling the assembly of heteroatom‐dense molecules by cross‐coupling of primary heteroarylamines and (hetero)aryl chlorides, while sought‐after given the ubiquity of unsymmetrical di(hetero)arylamino fragments in pharmacophores, are unknown. Herein, we disclose the new “double cage” bisphosphine PAd2‐DalPhos ( L2 ). The derived air‐stable NiII pre‐catalyst C2 functions well at low loadings in challenging test C?N cross‐couplings with established substrates, and facilitates the first Ni‐catalyzed C?N cross‐couplings of primary five‐ or six‐membered ring heteroarylamines and activated (hetero)aryl chlorides, with synthetically useful scope that is competitive with Pd catalysis. 相似文献
105.
106.
Dr. Todd R. Zeitler Timothy Van Heest Prof. David S. Sholl Dr. Mark D. Allendorf Dr. Jeffery A. Greathouse 《Chemphyschem》2013,14(16):3740-3750
A set of 98 nanoporous framework material (NFM) structures was investigated by classical Grand canonical Monte Carlo simulations for low-pressure O2 adsorption properties (Henry’s constant and isosteric heat of adsorption). The set of materials includes those that have shown high O2 uptake experimentally as well as a subset of more than 2000 structures previously screened for noble-gas uptake. While use of the general force field UFF is fruitful for noble-gas adsorption studies, its use is shown to be limited for the case of O2 adsorption—one distinct limitation is a lack of sufficient O2–metal interactions to be able to describe O2 interaction with open metal sites. Nonetheless, those structures without open metal sites that have very small pores (<2.5 Å) show increased O2/N2 selectivity. Additionally, O2/N2 mixture simulations show that in some cases, H2O or N2 can hinder O2 uptake for NFMs with small pores due to competitive adsorption. 相似文献
107.
Mark J. Logan 《代数通讯》2013,41(8):3739-3742
This note points out a factor of the Poincaré polynomial of the λ-isotypic component of the exterior algebra λL, where L is a complex semisimple Lie algebra and λ is a dominant weight. Although these polynomials have been studied with regard to their factorizations, this particular factor seems to have gone unstated. 相似文献
108.
Mark Krusemeyer 《代数通讯》2013,41(7):657-663
109.
A new three-component cascade reaction for the synthesis of thiohydantoins is reported. The reaction between α-amino esters, nitrostyrenes, and aromatic isothiocyanates is efficiently promoted by organic bases to afford highly substituted thiohydantoins in moderate to good yields and diastereoselectivities. 相似文献
110.