全文获取类型
收费全文 | 25757篇 |
免费 | 3038篇 |
国内免费 | 1875篇 |
专业分类
化学 | 14648篇 |
晶体学 | 1417篇 |
力学 | 1765篇 |
综合类 | 195篇 |
数学 | 6353篇 |
物理学 | 6292篇 |
出版年
2024年 | 39篇 |
2023年 | 326篇 |
2022年 | 674篇 |
2021年 | 729篇 |
2020年 | 1024篇 |
2019年 | 773篇 |
2018年 | 663篇 |
2017年 | 683篇 |
2016年 | 1142篇 |
2015年 | 1046篇 |
2014年 | 1249篇 |
2013年 | 2052篇 |
2012年 | 1380篇 |
2011年 | 1587篇 |
2010年 | 1246篇 |
2009年 | 1532篇 |
2008年 | 1522篇 |
2007年 | 1681篇 |
2006年 | 1542篇 |
2005年 | 1217篇 |
2004年 | 1137篇 |
2003年 | 983篇 |
2002年 | 794篇 |
2001年 | 705篇 |
2000年 | 683篇 |
1999年 | 569篇 |
1998年 | 552篇 |
1997年 | 491篇 |
1996年 | 424篇 |
1995年 | 309篇 |
1994年 | 273篇 |
1993年 | 231篇 |
1992年 | 202篇 |
1991年 | 160篇 |
1990年 | 138篇 |
1989年 | 111篇 |
1988年 | 103篇 |
1987年 | 85篇 |
1986年 | 88篇 |
1985年 | 69篇 |
1984年 | 68篇 |
1983年 | 28篇 |
1982年 | 35篇 |
1981年 | 41篇 |
1980年 | 29篇 |
1979年 | 33篇 |
1978年 | 48篇 |
1977年 | 48篇 |
1976年 | 46篇 |
1974年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Paul Cowper Yu Jin Michael D. Turton Dr. Gabriele Kociok‐Köhn Dr. Simon E. Lewis 《Angewandte Chemie (International ed. in English)》2016,55(7):2564-2568
Azulenesulfonium salts may be readily prepared from the corresponding azulenes by an SEAr reaction. These azulene sulfonium salts are bench‐stable species that may be employed as pseudohalides for cross‐coupling. Specifically, their application in Suzuki–Miyaura reactions has been demonstrated with a diverse selection of coupling partners. These azulenesulfonium salts possess significant advantages in comparison with the corresponding azulenyl halides, which are known to be unstable and difficult to prepare in pure form. 相似文献
992.
Edon Vitaku David T. Smith Prof. Dr. Jon T. Njardarson 《Angewandte Chemie (International ed. in English)》2016,55(6):2243-2247
Nitrogen heterocycles are found in a majority of approved small‐molecule pharmaceuticals, and the number of approved fluorinated drugs is increasing each decade. Therefore, new approaches for accessing fluorinated nitrogen heterocycles are of great significance. A novel, scalable, and metal‐free method for accessing a wide range of fluorinated indoles is described. This oxidative‐dearomatization‐enabled approach assembles 2‐trifluoromethyl NH‐indole products from simple commercially available anilines with hexafluoroacetylacetone in the presence of an organic oxidant. The nature of the aniline N‐capping group is critical for the success of this new reaction. Furthermore, the indole products contain a 3‐trifluoroacetyl group, which can be exploited to access a plethora of useful functional groups. 相似文献
993.
Exploiting the Multidentate Nature of Chiral Disulfonimides in a Multicomponent Reaction for the Asymmetric Synthesis of Pyrrolo[1,2‐a]indoles: A Remarkable Case of Enantioinversion 下载免费PDF全文
Dr. Alicia Galván Dr. Adán B. González‐Pérez Prof. Dr. Rosana Álvarez Prof. Dr. Angel R. de Lera Prof. Dr. Francisco J. Fañanás Prof. Félix Rodríguez 《Angewandte Chemie (International ed. in English)》2016,55(10):3428-3432
A new multicomponent coupling reaction for the enantioselective synthesis of pyrrolo[1,2‐a]indoles under the catalysis of a chiral disulfonimide is described. The high specificity of the reaction is a consequence of the multidentate character of the Brønsted acid catalyst. Insights from DFT calculations helped explain the unexpected high enantioselectivity observed with the simplest 3,3′‐unsubstituted binaphthyl catalyst as a result of transition‐state stabilization by a network of cooperative noncovalent interactions. The remarkable enantioinversion resulting from the simple introduction of substituents at 3‐ and 3′‐positions, the first reported example of this phenomenon in the context of binaphthalene‐derived Brønsted acid catalysis, was instead attributed to destabilizing steric interactions. 相似文献
994.
Lingyan Zhu Rabih O. Al‐Kaysi Christopher J. Bardeen 《Angewandte Chemie (International ed. in English)》2016,55(25):7073-7076
Photomechanical molecular crystals can undergo a variety of light‐induced motions, including expansion, bending, twisting, and jumping. The use of more complex crystal shapes may provide ways to turn these motions into useful work. To generate such shapes, pH‐driven reprecipitation has been used to grow branched microcrystals of the anthracene derivative 4‐fluoroanthracenecarboxylic acid. When these microcrystals are illuminated with light of λ=405 nm, an intermolecular [4+4] photodimerization reaction drives twisting and bending of the individual branches. These deformations drive a rotation of the overall crystal that can be repeated over multiple exposures to light. The magnitude and direction of this rotation vary because of differences in the crystal shape, but a typical branched crystal undergoes a 50° net rotation after 25 consecutive irradiations for 1 s. The ability of these crystals to undergo ratchet‐like rotation is attributed to their chiral shape. 相似文献
995.
Dr. Garrett K. Drayna Christian Hallas Kenneth Wang Dr. Sergio R. Domingos Sandra Eibenberger Prof. Dr. John M. Doyle David Patterson 《Angewandte Chemie (International ed. in English)》2016,55(16):4957-4961
Cooling molecules in the gas phase is important for precision spectroscopy, cold molecule physics, and physical chemistry. Measurements of conformational relaxation cross sections shed important light on potential energy surfaces and energy flow within a molecule. However, gas‐phase conformational cooling has not been previously observed directly. In this work, we directly observe conformational dynamics of 1,2‐propanediol in cold (6 K) collisions with atomic helium using microwave spectroscopy and buffer‐gas cooling. Precise knowledge and control of the collisional environment in the buffer‐gas allows us to measure the absolute collision cross‐section for conformational relaxation. Several conformers of 1,2‐propanediol are investigated and found to have relaxation cross‐sections with He ranging from σ=4.7(3.0)×10?18 cm2 to σ>5×10?16 cm2. Our method is applicable to a broad class of molecules and could be used to provide information about the potential energy surfaces of previously uninvestigated molecules. 相似文献
996.
Chemical Synthesis of Phosphorylated Histone H2A at Tyr57 Reveals Insight into the Inhibition Mode of the SAGA Deubiquitinating Module 下载免费PDF全文
997.
Integration of Nine Steps into One Membrane Reactor To Produce Synthesis Gases for Ammonia and Liquid Fuel 下载免费PDF全文
Wenping Li Prof. Xuefeng Zhu Prof. Shuguang Chen Prof. Weishen Yang 《Angewandte Chemie (International ed. in English)》2016,55(30):8566-8570
The synthesis of ammonia and liquid fuel are two important chemical processes in which most of the energy is consumed in the production of H2/N2 and H2/CO synthesis gases from natural gas (methane). Here, we report a membrane reactor with a mixed ionic‐electronic conducting membrane, in which the nine steps for the production of the two types of synthesis gases are shortened to one step by using water, air, and methane as feeds. In the membrane reactor, there is no direct CO2 emission and no CO or H2S present in the ammonia synthesis gas. The energy consumption for the production of the two synthesis gases can be reduced by 63 % by using this membrane reactor. This promising membrane reactor process has been successfully demonstrated by experiment. 相似文献
998.
Dr. Nicholas J. Green Dr. Anthony C. Willis Prof. Dr. Michael S. Sherburn 《Angewandte Chemie (International ed. in English)》2016,55(32):9244-9248
[Pd(PPh3)4] catalyzes a Suzuki–Miyaura‐like twofold cross‐coupling sequence between underivatized propargylic diols and either aryl or alkenyl boronic acids to furnish highly substituted 1,3‐dienes. Thus, 2,3‐diaryl‐1,3‐butadienes and their dialkenic congeners ([4]dendralenes) are delivered in a (pseudo)halogen‐free, single‐step synthesis which supersedes existing methods. Allenols are also readily formed. Treatment of these single‐ and twofold cross‐coupled products with acid leads to remarkably short syntheses of highly‐substituted benzofulvenes and aryl indenes, respectively. 相似文献
999.
Dr. Santosh Kumar Meena Prof. Marialore Sulpizi 《Angewandte Chemie (International ed. in English)》2016,55(39):11960-11964
Directly manipulating and controlling the size and shape of metal nanoparticles is a key step for their tailored applications. In this work, molecular dynamics simulations were applied to understand the microscopic origin of the asymmetric growth mechanism in gold nanorods. Different factors influencing the growth were selectively included in the models to unravel the role of the surfactants and ions. In the early stage of the growth, when the seed is only a few nanometers large, a dramatic symmetry breaking occurs as the surfactant layer preferentially covers the (100) and (110) facets, leaving the (111) facets unprotected. This anisotropic surfactant layer in turn promotes anisotropic growth with the less protected tips growing faster. When silver salt is added to the growth solution, the asymmetry of the facets is preserved, but the Br? concentration at the interface increases, resulting in increased surface passivation. 相似文献
1000.
Direct Identification of Protein–Protein Interactions by Single‐Molecule Force Spectroscopy 下载免费PDF全文
Dr. Andrés M. Vera Dr. Mariano Carrión‐Vázquez 《Angewandte Chemie (International ed. in English)》2016,55(45):13970-13973
Single‐molecule force spectroscopy based on atomic force microscopy (AFM‐SMFS) has allowed the measurement of the intermolecular forces involved in protein‐protein interactions at the molecular level. While intramolecular interactions are routinely identified directly by the use of polyprotein fingerprinting, there is a lack of a general method to directly identify single‐molecule intermolecular unbinding events. Here, we have developed an internally controlled strategy to measure protein–protein interactions by AFM‐SMFS that allows the direct identification of dissociation force peaks while ensuring single‐molecule conditions. Single‐molecule identification is assured by polyprotein fingerprinting while the intermolecular interaction is reported by a characteristic increase in contour length released after bond rupture. The latter is due to the exposure to force of a third protein that covalently connects the interacting pair. We demonstrate this strategy with a cohesin–dockerin interaction. 相似文献