全文获取类型
收费全文 | 6132篇 |
免费 | 442篇 |
国内免费 | 16篇 |
专业分类
化学 | 4882篇 |
晶体学 | 36篇 |
力学 | 70篇 |
数学 | 721篇 |
物理学 | 881篇 |
出版年
2024年 | 6篇 |
2023年 | 57篇 |
2022年 | 59篇 |
2021年 | 107篇 |
2020年 | 199篇 |
2019年 | 190篇 |
2018年 | 77篇 |
2017年 | 98篇 |
2016年 | 270篇 |
2015年 | 257篇 |
2014年 | 301篇 |
2013年 | 333篇 |
2012年 | 471篇 |
2011年 | 501篇 |
2010年 | 294篇 |
2009年 | 243篇 |
2008年 | 376篇 |
2007年 | 353篇 |
2006年 | 321篇 |
2005年 | 259篇 |
2004年 | 244篇 |
2003年 | 200篇 |
2002年 | 193篇 |
2001年 | 109篇 |
2000年 | 86篇 |
1999年 | 75篇 |
1998年 | 70篇 |
1997年 | 81篇 |
1996年 | 67篇 |
1995年 | 74篇 |
1994年 | 89篇 |
1993年 | 54篇 |
1992年 | 50篇 |
1991年 | 45篇 |
1990年 | 32篇 |
1989年 | 44篇 |
1988年 | 27篇 |
1987年 | 29篇 |
1986年 | 19篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 19篇 |
1979年 | 13篇 |
1978年 | 21篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1875年 | 4篇 |
排序方式: 共有6590条查询结果,搜索用时 15 毫秒
991.
992.
993.
Marie-Ange Lespinasse Dr. Kaiyao Wei Justine Perrin Dr. Matthias Winkler Sieme Hamaidia Alexis Leroy Dr. Zuzana Macek Jilkova Dr. Christian Philouze Dr. Patrice N. Marche Dr. Carlo Petosa Dr. Jérôme Govin Dr. Anouk Emadali Dr. Yung-Sing Wong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(64):e202202293
The pharmaceutical industry has a pervasive need for chiral specific molecules with optimal affinity for their biological targets. However, the mass production of such compounds is currently limited by conventional chemical routes, that are costly and have an environmental impact. Here, we propose an easy access to obtain new tetrahydroquinolines, a motif found in many bioactive compounds, that is rapid and cost effective. Starting from simple raw materials, the procedure uses a proline-catalyzed Mannich reaction followed by the addition of BF3 ⋅ OEt2, which generates a highly electrophilic aza-ortho-quinone methide intermediate capable of reacting with different nucleophiles to form the diversely functionalized tetrahydroquinoline. Moreover, this enantioselective one-pot process provides access for the first time to tetrahydroquinolines with a cis-2,3 and trans-3,4 configuration. As proof of concept, we demonstrate that a three-step reaction sequence, from simple and inexpensive starting compounds and catalysts, can generate a BD2-selective BET bromodomain inhibitor with anti-inflammatory effect. 相似文献
994.
M. Sc. Steffen Mader Dr. Lise Molinari Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):3910-3913
Various haloalkynes are converted in the presence of a dual activation gold catalyst. Via a dual activation process a completely atom economic head‐to‐tail coupling delivers gem‐dihalogenated conjugated enynes as valuable building blocks for organic synthesis. 相似文献
995.
Multicomponent Self‐Assembly with a Shape‐Persistent N‐Heterotriangulene Macrocycle on Au(111) 下载免费PDF全文
Kang Cui Dr. Florian Schlütter Dr. Oleksandr Ivasenko Dr. Milan Kivala Dr. Matthias G. Schwab Dr. Shern‐Long Lee Dr. Stijn F. L. Mertens Dr. Kazukuni Tahara Prof. Yoshito Tobe Prof. Klaus Müllen Dr. Kunal S. Mali Prof. Steven De Feyter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1652-1659
Multicomponent network formation by using a shape‐persistent macrocycle ( MC6 ) at the interface between an organic liquid and Au(111) surface is demonstrated. MC6 serves as a versatile building block that can be coadsorbed with a variety of organic molecules based on different types of noncovalent interactions at the liquid–solid interface. Scanning tunneling microscopy (STM) reveals the formation of crystalline bicomponent networks upon codeposition of MC6 with aromatic molecules, such as fullerene (C60) and coronene. Tetracyanoquinodimethane, on the other hand, was found to induce disorder into the MC6 networks by adsorbing on the rim of the macrocycle. Immobilization of MC6 itself was studied in two different noncovalently assembled host networks. MC6 assumed a rather passive role as a guest and simply occupied the host cavities in one network, whereas it induced a structural transition in the other. Finally, the central cavity of MC6 was used to capture C60 in a complex three‐component system. Precise immobilization of organic molecules at discrete locations within multicomponent networks, as demonstrated here, constitutes an important step towards bottom‐up fabrication of functional surface‐based nanostructures. 相似文献
996.
We consider an extension of Gödel logic by a unary operator that enables the addition of non-negative reals to truth-values. Although its propositional fragment has a simple proof system, first-order validity is Π 2-hard. We explain the close connection to Scarpellini’s result on Π 2-hardness of ?ukasiewicz’s logic. 相似文献
997.
Michael A. Nichols Rachel M. Sobinsky Allen D. Hunter Matthias Zeller 《Journal of chemical crystallography》2007,37(6):433-438
The crystal structure of butyllithium solvated by 1,2-dipiperidinoethane, BuLi·DPE-6, which has been used as an initiator
for a number of important commercial anionic polymerization reactions, is reported. The complex crystallizes from pentane
as a centrosymmetric dimer in the monoclinic space group P21/n with a = 9.8619(12), b = 17.963(2), c = 10.3655(12) ?, β = 114.090(2)° and Z = 2. The dimer is located on a crystallographic inversion center. The crystal under investigation was found to be non-merohedrally
twinned. In contrast to the two other dimeric BuLi complexes previously structurally characterized in the solid state, BuLi·DPE-6
has a planar central Li2C2 core. Semi-empirical (PM3) calculations were used to determine the lowest energy conformations of the dimer and also identified
three structural motifs that affect Li2C2 dimer ring planarity. 相似文献
998.
Günter Margraf Michael Bolte Matthias Wagner Hans-Wolfram Lerner 《Journal of chemical crystallography》2007,37(7):503-506
The mixed-valence compound [Li(THF)4]Cu2Br4 was synthesized in a redox reaction from 1,4-dihydroxynaphthalene, CuBr2 and LiNtBuSiMe3 in THF. X-ray quality crystals of [Li(THF)4]Cu2Br4 (monoclinic, P21/c) are obtained from the mother liquor at ambient temperature. In the solid state, infinite chains of anionic [Cu2Br4]− units are established. These chains are separated by [Li(THF)4]+ cations. 相似文献
999.
1000.
Inside Cover: Synthesis of an All‐Ferric Cuboidal Iron–Sulfur Cluster [FeIII4S4(SAr)4] (Angew. Chem. Int. Ed. 36/2018) 下载免费PDF全文