全文获取类型
收费全文 | 1006篇 |
免费 | 41篇 |
国内免费 | 2篇 |
专业分类
化学 | 691篇 |
晶体学 | 24篇 |
力学 | 15篇 |
数学 | 128篇 |
物理学 | 191篇 |
出版年
2023年 | 15篇 |
2022年 | 19篇 |
2021年 | 15篇 |
2020年 | 38篇 |
2019年 | 30篇 |
2018年 | 31篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 20篇 |
2014年 | 33篇 |
2013年 | 61篇 |
2012年 | 56篇 |
2011年 | 83篇 |
2010年 | 36篇 |
2009年 | 32篇 |
2008年 | 54篇 |
2007年 | 59篇 |
2006年 | 37篇 |
2005年 | 47篇 |
2004年 | 29篇 |
2003年 | 24篇 |
2002年 | 25篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1991年 | 7篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 8篇 |
1968年 | 8篇 |
1964年 | 4篇 |
1963年 | 6篇 |
1962年 | 8篇 |
1961年 | 11篇 |
1958年 | 7篇 |
1955年 | 5篇 |
排序方式: 共有1049条查询结果,搜索用时 15 毫秒
71.
Dey KK Prasad S Ash JT Deschamps M Grandinetti PJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,185(2):326-330
A sensitivity enhancement method based on selective adiabatic inversion of a satellite transition has been employed in a (pi/2)CT-(pi)ST1-(pi/2)CT spectral editing sequence to both enhance and resolve multisite NMR spectra of quadrupolar nuclei. In addition to a total enhancement of 2.5 times for spin 3/2 nuclei, enhancements up to 2.0 times is reported for the edited sites in a mixture of rubidium salts. 相似文献
72.
Boyle-Roden E Hoefer N Dey KK Grandinetti PJ Caffrey M 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,189(1):13-19
The cubic mesophase formed by monoacylglycerols and water is an important medium for the in meso crystallogenesis of membrane proteins. To investigate molecular level lipid and additive interactions within the cubic phase, a method was developed for improving the resolution of (1)H NMR spectra when using a conventional solution state NMR probe. Using this approach we obtained well-resolved J-coupling multiplets in the one-dimensional NMR spectrum of the cubic-Ia3d phase prepared with hydrated monoolein. A high resolution t-ROESY two-dimensional (1)H NMR spectrum of the cubic-Ia3d phase is also reported. Using this new methodology, we have investigated the interaction of two additive molecules, L-tryptophan and ruthenium-tris(2,2-bipyridyl) dichloride (rubipy), with the cubic mesophase. Based on the measured chemical shift differences when changing from an aqueous solution to the cubic phase, we conclude that L-tryptophan experiences specific interactions with the bilayer interface, whereas rubipy remains in the aqueous channels and does not associate with the lipid bilayer. 相似文献
73.
74.
Sharmistha Pal B. N. Roopa Khalid Abu Sulur G. Manjunath Sudhir Nambiar 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2261-2268
Thermal techniques, differential scanning calorimetry (DSC), and hot stage microscopy (HSM) have been used to study the interactions between furosemide and caffeine that are known to form a 1:1 cocrystal. This system has been used as an example to study the probable mechanism of cocrystal formation when the individual components, which are polymorphic, are heated. The study indicates that the phase transition of the low temperature stable polymorph of furosemide initiates cocrystal formation. This result suggests increased mass transfer rate can trigger cocrystal formation. The binary phase diagram (composition–temperature plots) of furosemide–cocrystal–caffeine system was determined from the DSC curves. The results imply that the cocrystal forms eutectic with caffeine but not with furosemide. This study has thus exemplified the use of DSC in understanding binary phase system where the two components form a cocrystal. 相似文献
75.
Sharmistha Karmakar Dr. Ayan Datta 《Angewandte Chemie (International ed. in English)》2014,53(36):9587-9591
At room temperature, 1,2‐hydrogen‐transfer reactions of N‐heterocyclic carbenes, like the imidazol‐2‐ylidene to give imidazole is shown to occurr almost entirely (>90 %) by quantum mechanical tunneling (QMT). At 60 K in an Ar matrix, for the 2, 3‐dihydrothiazol‐2‐ylidene→thiazole transformation, QMT is shown to increase the rate about 105 times. Calculations including small‐curvature tunneling show that the barrier for intermolecular 1,2‐hydrogen‐transfer reaction is small, and QMT leads to a reduced rate of the forward reaction because of nonclassical reflections even at room temperature. A small barrier also leads to smaller kinetic isotope effects because of efficient QMT by both H and D. QMT does not always lead to faster reactions or larger KIE values, particularly when the barrier is small. 相似文献
76.
The excellent properties of Methyl Ammonium Lead Iodide (MAPI) have already created an extensive research interest in photovoltaic applications. However, their utility in thermoelectric application is still not realized thoroughly by researchers. By continuing this interest, we have explored the formation of low dimensional CH3NH3PbI3 (MAPI) perovskite in presence of Polyaniline (PANI) and Multi-Walled Carbon Nanotubes (MWCNT) and its thermoelectric performance. For this purpose, a two stage, in-situ synthesis method was developed to prepare various composites such as MAPI-PANI, MWCNT-MAPI and MWCNT-PANI-MAPI. The as-formed MWCNT-PANI-MAPI composite revealed p-type conductivity with enhanced ZT (up to ~20,000 times) and power factor (3000 times) at room temperature as compared to pristine MAPI sample. Finally, we have demonstrated a proto-type thermoelectric power generator (TE device) fabricated using the best performing composite sample and measured its power output and efficiency at varied δT. 相似文献
77.
Kaushik Dey Shebeeb Kunjattu H. Anurag M. Chahande Rahul Banerjee 《Angewandte Chemie (International ed. in English)》2020,59(3):1161-1165
Covalent organic frameworks (COFs) have attracted attention due to their ordered pores leading to important industrial applications like storage and separation. Combined with their modular synthesis and pore engineering, COFs could become ideal candidates for nanoseparations. However, the fabrication of these microcrystalline powders as continuous, crack‐free, robust films remains a challenge. Herein, we report a simple, slow annealing strategy to construct centimeter‐scale COF films ( Tp‐Azo and Tp‐TTA ) with micrometer thickness. The as‐synthesized films are porous (SABET=2033 m2 g?1 for Tp‐Azo ) and chemically stable. These COFs have distinct size cut‐offs (ca. 2.7 and ca. 1.6 nm for Tp‐Azo and Tp‐TTA , respectively), which allow the size‐selective separation of gold nanoparticles. Unlike, other conventional membranes, the durable structure of the COF films allow for excellent recyclability (up to 4 consecutive cycles) and easy recovery of the gold nanoparticles from the solution. 相似文献
78.
Amit Mondal Biswajit Bhattacharya Susobhan Das Surojit Bhunia Rituparno Chowdhury Somnath Dey C. Malla Reddy 《Angewandte Chemie (International ed. in English)》2020,59(27):10971-10980
Ductility is a common phenomenon in many metals but is difficult to achieve in molecular crystals. Organic crystals bend plastically on one or two face‐specific directions but fracture when stressed in any other arbitrary directions. An exceptional metal‐like ductility and malleability in the isomorphous crystals of two globular molecules, BH3NMe3 and BF3NMe3, is reported, with characteristic tensile stretching, compression, twisting, and thinning. The mechanically deformed samples, which transition to lower symmetry phases, retain good long‐range order amenable to structure determination by single‐crystal X‐ray diffraction. Molecules in these high‐symmetry crystals interact through electrostatic forces (B??N+) to form columnar structures with multiple slip planes and weak dispersive forces between columns. On the other hand, the limited number of facile slip planes and strong dihydrogen bonding in BH3NHMe2 negates ductility. Our study has implications for the design of soft ferroelectrics, solid electrolytes, barocalorics, and soft robotics. 相似文献
79.
Monte Carlo simulation is a very powerful tool for simulation of transient and steady state crystal size distribution (CSD) in a continuous crystallizer under stochastic dispersion effects. In the present work, transient CSD in a continuous crystallizer has been reported when shape factor and growth rate dispersions conform to normal distribution. For the steady state run, the algorithm reported by Sen Gupta and Dutta elsewhere has been used to validate the results obtained in the present work when the steady state is reached. 相似文献
80.
A p‐Hydroxyphenacyl–Benzothiazole–Chlorambucil Conjugate as a Real‐Time‐Monitoring Drug‐Delivery System Assisted by Excited‐State Intramolecular Proton Transfer
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shrabani Barman Sourav K. Mukhopadhyay Sandipan Biswas Surajit Nandi Moumita Gangopadhyay Satyahari Dey Anakuthil Anoop N. D. Pradeep Singh 《Angewandte Chemie (International ed. in English)》2016,55(13):4194-4198
Among the well‐known phototriggers, the p‐hydroxyphenacyl (pHP) group has consistently enabled the very fast, efficient, and high‐conversion release of active molecules. Despite this unique behavior, the pHP group has been ignored as a delivery agent, particularly in the area of theranostics, because of two major limitations: Its excitation wavelength is below 400 nm, and it is nonfluorescent. We have overcome these limitations by incorporating a 2‐(2′‐hydroxyphenyl)benzothiazole (HBT) appendage capable of rapid excited‐state intramolecular proton transfer (ESIPT). The ESIPT effect also provided two unique advantages: It assisted the deprotonation of the pHP group for faster release, and it was accompanied by a distinct fluorescence color change upon photorelease. In vitro studies showed that the p‐hydroxyphenacyl–benzothiazole–chlorambucil conjugate presents excellent properties, such as real‐time monitoring, photoregulated drug delivery, and biocompatibility. 相似文献