全文获取类型
收费全文 | 36801篇 |
免费 | 8444篇 |
国内免费 | 1598篇 |
专业分类
化学 | 40987篇 |
晶体学 | 340篇 |
力学 | 526篇 |
综合类 | 43篇 |
数学 | 2006篇 |
物理学 | 2941篇 |
出版年
2024年 | 8篇 |
2023年 | 41篇 |
2022年 | 81篇 |
2021年 | 195篇 |
2020年 | 1267篇 |
2019年 | 2639篇 |
2018年 | 1068篇 |
2017年 | 682篇 |
2016年 | 3409篇 |
2015年 | 3552篇 |
2014年 | 3468篇 |
2013年 | 4086篇 |
2012年 | 2995篇 |
2011年 | 2182篇 |
2010年 | 2867篇 |
2009年 | 2863篇 |
2008年 | 2348篇 |
2007年 | 1721篇 |
2006年 | 1426篇 |
2005年 | 1636篇 |
2004年 | 1427篇 |
2003年 | 1319篇 |
2002年 | 2000篇 |
2001年 | 1419篇 |
2000年 | 1299篇 |
1999年 | 394篇 |
1998年 | 77篇 |
1997年 | 66篇 |
1996年 | 38篇 |
1995年 | 39篇 |
1994年 | 25篇 |
1993年 | 25篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 34篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 22篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1971年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
Azobenzene‐Functionalized Metal–Organic Polyhedra for the Optically Responsive Capture and Release of Guest Molecules 下载免费PDF全文
Dr. Jinhee Park Dr. Lin‐Bing Sun Ying‐Pin Chen Zachary Perry Prof. Dr. Hong‐Cai Zhou 《Angewandte Chemie (International ed. in English)》2014,53(23):5842-5846
Stimuli‐responsive metal–organic polyhedra (srMOPs) functionalized with azobenzene showed UV‐irradiation‐induced isomerization from the insoluble trans‐srMOP to the soluble cis‐srMOP, whereas irradiation with blue light reversed this process. Guest molecules were trapped and released upon cis‐to‐trans and trans‐to‐cis isomerization of the srMOPs, respectively. This study provides a new direction in the ever‐diversifying field of MOPs, while laying the groundwork for a new class of optically responsive materials. 相似文献
952.
Transition from π Radicals to σ Radicals: Substituent‐Tuned Cyclization of Hydrazonyl Radicals 下载免费PDF全文
Xiu‐Long Yang Prof. Dr. Wei Yu Prof. Dr. Bing Han 《Angewandte Chemie (International ed. in English)》2014,53(12):3158-3162
Hydrazonyl radicals are known for their π‐electronic structures; however, their σ‐electronic structures have not been reported as yet. Herein, we show that readily accessible β,γ‐ and γ,δ‐unsaturated N‐trichloroacetyl and N‐trifluoroacetyl hydrazones can be conveniently converted into hydrazonyl σ radicals, which subsequently undergo 5‐exo‐trig radical cyclization at the N1 or N2 atom to form pyrazolines and azomethine imines, respectively. 相似文献
953.
The Origin of the Selectivity and Activity of Ruthenium‐Cluster Catalysts for Fuel‐Cell Feed‐Gas Purification: A Gas‐Phase Approach 下载免费PDF全文
Dr. Sandra M. Lang Prof. Dr. Thorsten M. Bernhardt Marjan Krstić Prof. Dr. Vlasta Bonačić‐Koutecký 《Angewandte Chemie (International ed. in English)》2014,53(21):5467-5471
Gas‐phase ruthenium clusters Run+ (n=2–6) are employed as model systems to discover the origin of the outstanding performance of supported sub‐nanometer ruthenium particles in the catalytic CO methanation reaction with relevance to the hydrogen feed‐gas purification for advanced fuel‐cell applications. Using ion‐trap mass spectrometry in conjunction with first‐principles density functional theory calculations three fundamental properties of these clusters are identified which determine the selectivity and catalytic activity: high reactivity toward CO in contrast to inertness in the reaction with CO2; promotion of cooperatively enhanced H2 coadsorption and dissociation on pre‐formed ruthenium carbonyl clusters, that is, no CO poisoning occurs; and the presence of Ru‐atom sites with a low number of metal–metal bonds, which are particularly active for H2 coadsorption and activation. Furthermore, comprehensive theoretical investigations provide mechanistic insight into the CO methanation reaction and discover a reaction route involving the formation of a formyl‐type intermediate. 相似文献
954.
Youn Jeong Jang Dr. Jae Young Kim Won Yong Kim Prof. Jeong Kon Seo Prof. Sungjee Kim Prof. Kun‐Hong Lee Prof. Jae Sung Lee 《Angewandte Chemie (International ed. in English)》2014,53(23):5852-5857
As a photocathode for CO2 reduction, zinc‐blende zinc telluride (ZnTe) was directly formed on a Zn/ZnO nanowire substrate by a simple dissolution–recrystallization mechanism without any surfactant. With the most negative conduction‐band edge among p‐type semiconductors, this new photocatalyst showed efficient and stable CO formation in photoelectrochemical CO2 reduction at ?0.2–?0.7 V versus RHE without a sacrificial reagent. 相似文献
955.
Organozinc Pivalate Reagents: Segregation,Solubility, Stabilization,and Structural Insights 下载免费PDF全文
Dr. Alberto Hernán‐Gómez Emma Herd Prof. Eva Hevia Dr. Alan R. Kennedy Prof. Dr. Paul Knochel Prof. Dr. Konrad Koszinowski Sophia M. Manolikakes Prof. Robert E. Mulvey Christoph Schnegelsberg 《Angewandte Chemie (International ed. in English)》2014,53(10):2706-2710
The pivalates RZnOPiv?Mg(OPiv)X?n LiCl (OPiv=pivalate; R=aryl; X=Cl, Br, I) stand out amongst salt‐supported organometallic reagents, because apart from their effectiveness in Negishi cross‐coupling reactions, they show more resistance to attack by moist air than conventional organometallic compounds. Herein a combination of synthesis, coupling applications, X‐ray crystallographic studies, NMR (including DOSY) studies, and ESI mass spectrometric studies provide details of these pivalate reagents in their own right. A p‐tolyl case system shows that in [D8]THF solution these reagents exist as separated Me(p‐C6H4)ZnCl and Mg(OPiv)2 species. Air exposure tests and X‐ray crystallographic studies indicate that Mg(OPiv)2 enhances the air stability of aryl zinc species by sequestering H2O contaminants. Coupling reactions of Me(p‐C6H4)ZnX (where X=different salts) with 4‐bromoanisole highlight the importance of the presence of Mg(OPiv)2. Insight into the role of LiCl in these multicomponent mixtures is provided by the molecular structure of [(THF)2Li2(Cl)2(OPiv)2Zn]. 相似文献
956.
Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster 下载免费PDF全文
Nathan A. Seifert Dr. Daniel P. Zaleski Dr. Cristóbal Pérez Dr. Justin L. Neill Prof. Brooks H. Pate Montserrat Vallejo‐López Prof. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Fernando Castaño Prof. Isabelle Kleiner 《Angewandte Chemie (International ed. in English)》2014,53(12):3210-3213
Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. 相似文献
957.
Molecular Engineering of Push–Pull Porphyrin Dyes for Highly Efficient Dye‐Sensitized Solar Cells: The Role of Benzene Spacers 下载免费PDF全文
Shaik M. Zakeeruddin Shu‐Nung Chang Chi‐Hung Hsieh Chen‐Yu Yeh Michael Grätzel 《Angewandte Chemie (International ed. in English)》2014,53(11):2973-2977
Porphyrins have drawn much attention as sensitizers owing to the large absorption coefficients of their Soret and Q bands in the visible region. In a donor and acceptor zinc porphyrin we applied a new strategy of introducing 2,1,3‐benzothiadiazole (BTD) as a π‐conjugated linker between the anchoring group and the porphyrin chromophore to broaden the absorption spectra to fill the valley between the Soret and Q bands. With this novel approach, we observed 12.75 % power‐conversion efficiency under simulated one‐sun illumination (AM1.5G, 100 mW cm?2). In this study, we showed the importance of introducing the phenyl group as a spacer between the BTD and the zinc porphyrin in achieving high power‐conversion efficiencies. Time‐resolved fluorescence, transient‐photocurrent‐decay, and transient‐photovoltage‐decay measurements were employed to determine the electron‐injection dynamics and the lifetime of the photogenerated charge carriers. 相似文献
958.
Interaction with the Surrounding Water Plays a Key Role in Determining the Aggregation Propensity of Proteins 下载免费PDF全文
Dr. Song‐Ho Chong Prof. Sihyun Ham 《Angewandte Chemie (International ed. in English)》2014,53(15):3961-3964
Understanding the molecular determinants of the relative propensities of proteins to aggregate in a cellular environment is a central issue for treating protein‐aggregation diseases and developing peptide‐based therapeutics. Despite the expectation that protein aggregation can largely be attributed to direct protein–protein interactions, a crucial role the surrounding water in determining the aggregation propensity of proteins both in vitro and in vivo was identified. The overall protein hydrophobicity, defined solely by the hydration free energy of a protein in its monomeric state sampling its equilibrium structures, was shown to be the predominant determinant of protein aggregation propensity in aqueous solution. Striking discrimination of positively and negatively charged residues by the surrounding water was also found. This effect depends on the protein net charge and plays a crucial role in regulating the solubility of the protein. These results pave the way for the design of aggregation‐resistant proteins as biotherapeutics. 相似文献
959.
Inside Back Cover: Patternable Large‐Scale Molybdenium Disulfide Atomic Layers Grown by Gold‐Assisted Chemical Vapor Deposition (Angew. Chem. Int. Ed. 5/2014) 下载免费PDF全文
960.
Hexafluoroantimonic Acid Catalysis: Formal [3+2+2] Cycloaddition of Aziridines with Two Alkynes 下载免费PDF全文
Ming‐Bo Zhou Ren‐Jie Song Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2014,53(16):4196-4199
A practical method for the synthesis of azepine derivatives, a typical seven‐membered heterocyclic ring system, was developed and involves the use of hexafluoroantimonic acid to catalyze a formal [3+2+2] cycloaddition of aziridines with two alkynes. This method was applicable to two of the same or different terminal alkynes for the [3+2+2] cycloaddition with unactivated aziridines, and furnished the corresponding azepine derivatives in good yields with good levels of chemo‐ and regioselectivity. The mechanism was also discussed according to the results of the in situ HRMS and 1H NMR analysis. 相似文献