全文获取类型
收费全文 | 1362篇 |
免费 | 200篇 |
国内免费 | 3篇 |
专业分类
化学 | 1057篇 |
晶体学 | 3篇 |
力学 | 271篇 |
综合类 | 1篇 |
数学 | 145篇 |
物理学 | 88篇 |
出版年
2020年 | 8篇 |
2018年 | 11篇 |
2016年 | 32篇 |
2015年 | 71篇 |
2014年 | 109篇 |
2013年 | 155篇 |
2012年 | 95篇 |
2011年 | 26篇 |
2010年 | 113篇 |
2009年 | 129篇 |
2008年 | 24篇 |
2007年 | 17篇 |
2005年 | 9篇 |
2002年 | 7篇 |
1999年 | 7篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 67篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 9篇 |
1977年 | 19篇 |
1976年 | 25篇 |
1975年 | 22篇 |
1974年 | 31篇 |
1973年 | 18篇 |
1972年 | 21篇 |
1971年 | 16篇 |
1970年 | 59篇 |
1969年 | 36篇 |
1968年 | 20篇 |
1967年 | 13篇 |
1965年 | 10篇 |
1963年 | 18篇 |
1962年 | 10篇 |
1961年 | 11篇 |
1960年 | 9篇 |
1959年 | 8篇 |
1958年 | 13篇 |
排序方式: 共有1565条查询结果,搜索用时 15 毫秒
141.
Different Complexation Behavior of P‐Functionalized Ferrocene Derivatives Towards SnCl2, SnCl4 and SnPh2Cl2: Auto‐ionization and Redox‐Type Reactions 下载免费PDF全文
Dipl.‐Chem. Matthias Gawron Dr. Christina Dietz Michael Lutter Dr. Andrew Duthie Prof. Dr. Viatcheslav Jouikov Prof. Dr. Klaus Jurkschat 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16609-16622
The novel phosphonyl‐substituted ferrocene derivatives [Fe(η5‐Cp)(η5‐C5H3{P(O)(O‐iPr)2}2‐1,2)] ( Fc1,2 ) and [Fe{η5‐C5H4P(O)(O‐iPr)2}2] ( Fc1,1′ ) react with SnCl2, SnCl4, and SnPh2Cl2, giving the corresponding complexes [(Fc1,2)2SnCl][SnCl3] ( 1 ), [{(Fc1,1′)SnCl2}n] ( 2 ), [(Fc1,1′)SnCl4] ( 3 ), [{(Fc1,1′)SnPh2Cl2}n] ( 4 ), and [(Fc1,2)SnCl4] ( 5 ), respectively. The compounds are characterized by elemental analyses, 1H, 13C, 31P, 119Sn NMR and IR spectroscopy, 31P and 119Sn CP‐MAS NMR spectroscopy, cyclovoltammetry, electrospray ionization mass spectrometry, and single‐crystal as well as powder X‐ray diffraction analyses. The experimental work is accompanied by DFT calculations, which help to shed light on the origin for the different reaction behavior of Fc1,1′ and Fc1,2 towards tin(II) chloride. 相似文献
142.
On Copper(I) Fluorides,the Cuprophilic Interaction,the Preparation of Copper Nitride at Room Temperature,and the Formation Mechanism at Elevated Temperatures 下载免费PDF全文
Dipl.‐Chem. Patrick Woidy Dr. Antti J. Karttunen Dr. Marc Widenmeyer Prof. Dr. Rainer Niewa Prof. Dr. Florian Kraus 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3290-3303
Our attempts to synthesize the hitherto unknown binary copper(I) fluoride have led to first successes and a serendipitious result: By conproportionation of elemental copper and copper(II) fluoride in anhydrous liquid ammonia, two copper(I) fluorides were obtained as simple NH3 complexes. One of them presents an example of ligand‐unsupported “cuprophilic” interactions in an infinite [Cu2(NH3)4]2+ chain with alternating Cu–Cu distances. We discovered that both copper(I) fluorides can easily be converted into Cu3N at room temperature, just by applying a vacuum. Additionally, we investigated the formation mechanism of the classical synthesis route of Cu3N that starts with CuF2 and flowing NH3 in the temperature range between ambient and 290 °C by means of thermal analysis and in situ neutron diffraction. The reaction proceeds at elevated temperatures through the formation of a blue and amorphous ammoniate Cu(NH3)2F2, the reformation of CuF2, and finally the redox reaction to form Cu3N. 相似文献
143.
Identification of tert‐Butyl Cations in Zeolite H‐ZSM‐5: Evidence from NMR Spectroscopy and DFT Calculations 下载免费PDF全文
Dr. Weili Dai Prof.Dr. Chuanming Wang Dr. Xianfeng Yi Prof. Dr. Anmin Zheng Prof. Dr. Landong Li Prof. Dr. Guangjun Wu Prof. Dr. Naijia Guan Prof. Dr. Zaiku Xie Dipl.‐Chem. Michael Dyballa Prof. Dr. Michael Hunger 《Angewandte Chemie (International ed. in English)》2015,54(30):8783-8786
Experimental evidence for the presence of tert‐butyl cations, which are important intermediates in acid‐catalyzed heterogeneous reactions, on solid acids has still not been provided to date. By combining density functional theory (DFT) calculations with 1H/13C magic‐angle‐spinning NMR spectroscopy, the tert‐butyl cation was successfully identified on zeolite H‐ZSM‐5 upon conversion of isobutene by capturing this intermediate with ammonia. 相似文献
144.
Structure Elucidation and Activity of Kolossin A,the D‐/L‐Pentadecapeptide Product of a Giant Nonribosomal Peptide Synthetase 下载免费PDF全文
Prof. Dr. Helge B. Bode Dr. Alexander O. Brachmann Dr. Kirtikumar B. Jadhav Dr. Lydia Seyfarth Dipl.‐Chem. Christina Dauth Dr. Sebastian W. Fuchs Dr. Marcel Kaiser Dr. Nick R. Waterfield Dipl.‐Phys. Holger Sack Prof. Dr. Stefan H. Heinemann Prof. Dr. Hans‐Dieter Arndt 《Angewandte Chemie (International ed. in English)》2015,54(35):10352-10355
The largest continuous bacterial nonribosomal peptide synthetase discovered so far is described. It consists of 15 consecutive modules arising from an uninterrupted, fully functional gene in the entomopathogenic bacterium Photorhabdus luminescens. The identification of its cryptic biosynthesis product was achieved by using a combination of genome analysis, promoter exchange, isotopic labeling experiments, and total synthesis of a focused collection of peptide candidates. Although it belongs to the growing class of D ‐/ L ‐peptide natural products, the encoded metabolite kolossin A was found to be largely devoid of antibiotic activity and is likely involved in interspecies communication. A stereoisomer of this peculiar natural product displayed high activity against Trypanosoma brucei rhodesiense, a recalcitrant parasite that causes the deadly disease African sleeping sickness. 相似文献
145.
Dipl.‐Chem. Christian Schöttle Dr. Pascal Bockstaller Dr. Radian Popescu Prof. Dr. Dagmar Gerthsen Prof. Dr. Claus Feldmann 《Angewandte Chemie (International ed. in English)》2015,54(34):9866-9870
Mo0, W0, Fe0, Ru0, Re0, and Zn0 nanoparticles—essentially base metals—are prepared as a general strategy by a sodium naphthalenide ([NaNaph])‐driven reduction of simple metal chlorides in ethers (1,2‐dimethoxyethane (DME), tetrahydrofuran (THF)). All the nanoparticles have diameters ≤10 nm, and they can be obtained either as powder samples or long‐term stable suspensions. Direct follow‐up reactions (e.g., Mo0+S8, FeCl3+AsCl3, ReCl5+MoCl5), moreover, allow the preparation of MoS2, FeAs2, or Re4Mo nanoparticles of similar size as the pristine metals (≤10 nm). 相似文献
146.
A Hot‐Segment‐Based Approach for the Design of Cross‐Amyloid Interaction Surface Mimics as Inhibitors of Amyloid Self‐Assembly 下载免费PDF全文
Dr. Erika Andreetto Dipl.‐Chem. Eleni Malideli Dr. Li‐Mei Yan Dipl.‐Ing. Michael Kracklauer MSc. Karine Farbiarz Dipl.‐Chem. Marianna Tatarek‐Nossol Prof. Dr. Gerhard Rammes M. Sc. Elke Prade Tatjana Neumüller Dr. Andrea Caporale M. Sc. Anna Spanopoulou B. Sc. Maria Bakou Prof. Dr. Bernd Reif Prof. Dr. Aphrodite Kapurniotu 《Angewandte Chemie (International ed. in English)》2015,54(44):13095-13100
The design of inhibitors of protein–protein interactions mediating amyloid self‐assembly is a major challenge mainly due to the dynamic nature of the involved structures and interfaces. Interactions of amyloidogenic polypeptides with other proteins are important modulators of self‐assembly. Here we present a hot‐segment‐linking approach to design a series of mimics of the IAPP cross‐amyloid interaction surface with Aβ (ISMs) as nanomolar inhibitors of amyloidogenesis and cytotoxicity of Aβ, IAPP, or both polypeptides. The nature of the linker determines ISM structure and inhibitory function including both potency and target selectivity. Importantly, ISMs effectively suppress both self‐ and cross‐seeded IAPP self‐assembly. Our results provide a novel class of highly potent peptide leads for targeting protein aggregation in Alzheimer’s disease, type 2 diabetes, or both diseases and a chemical approach to inhibit amyloid self‐assembly and pathogenic interactions of other proteins as well. 相似文献
147.
Dipl.‐Chem. Mario Jauker Dipl.‐Chem. Helmut Griesser Prof. Clemens Richert 《Angewandte Chemie (International ed. in English)》2015,54(48):14564-14569
How the biochemical machinery evolved from simple precursors is an open question. Here we show that ribonucleotides and amino acids condense to peptidyl RNAs in the absence of enzymes under conditions established for genetic copying. Untemplated formation of RNA strands that can encode genetic information, formation of peptidyl chains linked to RNA, and formation of the cofactors NAD+, FAD, and ATP all occur under the same conditions. In the peptidyl RNAs, the peptide chains are phosphoramidate‐linked to a ribonucleotide. Peptidyl RNAs with long peptide chains were selected from an initial pool when a lipophilic phase simulating the interior of membranes was offered, and free peptides were released upon acidification. Our results show that key molecules of genetics, catalysis, and metabolism can emerge under the same conditions, without a mineral surface, without an enzyme, and without the need for chemical pre‐activation. 相似文献
148.
Reverse Engineering of Conjugated Microporous Polymers: Defect Structures of Tetrakis(4‐ethynylphenyl)stannane Networks 下载免费PDF全文
M. Sc. Andrea C. Uptmoor M. Sc. Jan Freudenberg M. Sc. S. Thimon Schwäbel Dipl. Chem. Fabian Paulus Dr. Frank Rominger Dr. Felix Hinkel Prof. Uwe H. F. Bunz 《Angewandte Chemie (International ed. in English)》2015,54(49):14673-14676
Two different conjugated microporous polymers (CMPs) based on tetrakis(4‐ethynylphenyl)stannane as the repeating unit were synthesized and their BET surfaces and thermal properties were investigated. The first direct method to elucidate the molecular structure of the organic linkers between the tin centers by digestion of the CMP is described. Selective cleavage of the tin–carbon bonds with chloroacetic acid afforded the isolated bridging units and provided insight into the surprisingly varied chemical composition of these networks. 相似文献
149.
Dipl.‐Chem. Jan Tillmann Dipl.‐Chem. Josef Heinrich Wender Dr. Ute Bahr Dr. Michael Bolte Dr. Hans‐Wolfram Lerner Prof. Dr. Max C. Holthausen Prof. Dr. Matthias Wagner 《Angewandte Chemie (International ed. in English)》2015,54(18):5429-5433
Silicon analogues of the most prominent carbon nanostructures, namely, hollow spheroidals such as C60 and the fullerene family, have been unknown to date. Herein we show that discrete Si20 dodecahedra, stabilized by an endohedral guest and valence saturation, are accessible in preparative yields through a chloride‐induced disproportionation reaction of hexachlorodisilane in the presence of tri(n‐butyl)amine. X‐ray crystallography revealed that each silicon dodecahedron contains an endohedral chloride ion that imparts a net negative charge. Eight chloro substituents and twelve trichlorosilyl groups are attached to the surface of each cluster in a strictly regioregular arrangement, a thermodynamically preferred substitution pattern according to quantum‐chemical assessment. Our results demonstrate that the wet‐chemical self‐assembly of a complex, monodisperse Si nanostructure is possible under mild conditions starting from simple Si2 building blocks. 相似文献
150.
Regioselective Ring‐Opening Polymerization of a Polyhydroxycarboxylic Acid for the Synthesis of a Nanoscale Carrier Material with pH‐Dependent Stability and Sustained Drug Release 下载免费PDF全文
Dipl.‐Chem. Alexander Ewe Dr. Anita Jansen de Salazar Dipl.‐Phys. Katharina Lemmnitzer Michael Marsch Prof. Dr. Achim Aigner Prof. Dr. Armin Geyer 《Angewandte Chemie (International ed. in English)》2015,54(21):6364-6369
Synthetic polyesters are usually composed of monohydroxycarboxylic acids to avoid the problem of regioselectivity during ring‐opening polymerization. In contrast, the linear polyester BICpoly contains four secondary OH groups and is nevertheless esterified regioselectively at only one of these positions. Neither the synthesis of the tricyclic monomers nor the ring‐opening polymerization requires protecting groups, making BICpoly an attractive novel and biocompatible polymer. BICpoly nanoparticles can be loaded with low‐molecular weight drugs or coated onto surfaces as thin films. The release of loaded compounds makes BICpoly an attractive depot for drug release, as shown herein by loading BICpoly with dyes or the cytostatic drug doxorubicin. BICpoly is distinguishable from other polymers by its characteristic pH‐dependent degradation. 相似文献