全文获取类型
收费全文 | 611篇 |
免费 | 30篇 |
国内免费 | 4篇 |
专业分类
化学 | 424篇 |
晶体学 | 4篇 |
力学 | 9篇 |
数学 | 29篇 |
物理学 | 179篇 |
出版年
2023年 | 5篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 22篇 |
2013年 | 23篇 |
2012年 | 31篇 |
2011年 | 30篇 |
2010年 | 23篇 |
2009年 | 22篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 21篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 25篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 3篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 21篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 14篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1971年 | 2篇 |
排序方式: 共有645条查询结果,搜索用时 15 毫秒
1.
Koyuki Sakai Hiroki Nishiyama Shinsuke Inagi Ikuyoshi Tomita Yusuke Hibi Motonori Komura Keiji Nose Tomokazu Iyoda 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):E1-E8
A block copolymer composed of a flexible polar poly(ethylene glycol) (PEG) and a less polar liquid crystalline poly(allene) segments is prepared by the living coordination polymerization of an allene derivative possessing trans‐azobenzene‐containing mesogenic substituent by the use of a π‐allylnickel macroinitiator bearing PEG segment. The thin film of the block copolymer is prepared by the spin coating of its solution onto mica or silicon wafer which proves to possess perpendicularly oriented nanocylindrical microphase separated structures as supported by the differential calorimetric, polarized optical microscopic, grazing‐incidence small‐angle X‐ray scattering, transmission electron microscope, and atomic force microscope measurements. 相似文献
2.
Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation 下载免费PDF全文
Dr. Taiga Yurino Yohei Ueda Dr. Yoshiki Shimizu Dr. Shinji Tanaka Haruka Nishiyama Prof. Dr. Hayato Tsurugi Prof. Dr. Kazuhiko Sato Prof. Dr. Kazushi Mashima 《Angewandte Chemie (International ed. in English)》2015,54(48):14437-14441
A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity. 相似文献
3.
Ilia?NegriEmail authorView authors OrcID profile Yoichi?Nishiyama 《Statistical Inference for Stochastic Processes》2017,20(3):387-397
The problem to establish the asymptotic distribution of statistical estimators as well as the moment convergence of such estimators has been recognized as an important issue in advanced theories of statistics. This problem has been deeply studied for M-estimators for a wide range of models by many authors. The purpose of this paper is to present an alternative and apparently simple theory to derive the moment convergence of Z-estimators. In the proposed approach the cases of parameters with different rate of convergence can be treated easily and smoothly and any large deviation type inequalities necessary for the same result for M-estimators do not appear in this approach. Applications to the model of i.i.d. observation, Cox’s regression model as well as some diffusion process are discussed. 相似文献
4.
Siquan Zhang Loris Lombardo Masahiko Tsujimoto Zeyu Fan Ellan K. Berdichevsky Yong-Sheng Wei Kotoha Kageyama Yusuke Nishiyama Satoshi Horike 《Angewandte Chemie (International ed. in English)》2023,62(47):e202312095
Crystalline triazine-based covalent organic frameworks (COFs) are aromatic nitrogen-rich porous materials. COFs typically show high thermal/chemical stability, and are promising for energy applications, but often require harsh synthesis conditions and suffer from low crystallinity. In this work, we propose an environmentally friendly route for the synthesis of crystalline COFs from CO2 molecules as a precursor. The mass ratio of CO2 conversion into COFs formula unit reaches 46.3 %. The synthesis consists of two steps; preparation of 1,4-piperazinedicarboxaldehyde from CO2 and piperazine, and condensation of the dicarboxaldehyde and melamine to construct the framework. The CO2-derived COF has a 3-fold interpenetrated structure of 2D layers determined by powder X-ray diffraction, high-resolution transmission electron microscopy, and select-area electron diffraction. The structure shows a high Brunauer–Emmett–Teller surface area of 945 m2 g−1 and high stability against strong acid (6 M HCl), base (6 M NaOH), and boiling water over 24 hours. Post-modification of the framework with oxone has been demonstrated to modulate hydrophilicity, and it exhibits proton conductivity of 2.5×10−2 S cm−1 at 85 °C, 95 % of relative humidity. 相似文献
5.
Dr. Ziqian Xue Dr. Jia-Jia Zheng Dr. Yusuke Nishiyama Dr. Ming-Shui Yao Dr. Yoshitaka Aoyama Zeyu Fan Dr. Ping Wang Prof. Takashi Kajiwara Prof. Yoshiki Kubota Prof. Satoshi Horike Prof. Ken-ichi Otake Prof. Susumu Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202215234
Exploring new porous coordination polymers (PCPs) that have tunable structure and conductivity is attractive but remains challenging. Herein, fine pore structure engineering by ligand conformation control of naphthalene diimide (NDI)-based semiconducting PCPs with π stacking-dependent conductivity tunability is achieved. The π stacking distances and ligand conformation in these isoreticular PCPs were modulated by employing metal centers with different coordination geometries. As a result, three conjugated PCPs (Co−pyNDI, Ni−pyNDI, and Zn−pyNDI) with varying pore structure and conductivity were obtained. Their crystal structures were determined by three-dimensional electron diffraction. The through-space charge transfer and tunable pore structure in these PCPs result in modulated selectivity and sensitivity in gas sensing. Zn−pyNDI can serve as a room-temperature operable chemiresistive sensor selective to acetone. 相似文献
6.
Kotaro Hayashi Hiroyuki Chaya Shigeto Fukushima Sumiyo Watanabe Hiroyasu Takemoto Kensuke Osada Nobuhiro Nishiyama Kanjiro Miyata Kazunori Kataoka 《Macromolecular rapid communications》2016,37(6):486-493
Polyion complexes (b‐PICs) are prepared by mixing single‐ or double‐stranded oligo RNA (aniomer) with poly(ethylene glycol)‐b‐poly(l ‐lysine) (PEG‐PLL) (block catiomer) to clarify the effect of aniomer chain rigidity on association behaviors at varying concentrations. Here, a 21‐mer single‐stranded RNA (ssRNA) (persistence length: 1.0 nm) and a 21‐mer double‐stranded RNA (small interfering RNA, siRNA) (persistence length: 62 nm) are compared. Both oligo RNAs form a minimal charge‐neutralized ionomer pair with a single PEG‐PLL chain, termed unit b‐PIC (uPIC), at low concentrations (<≈0.01 mg mL−1). Above the critical association concentration (≈0.01 mg mL−1), ssRNA b‐PICs form secondary associates, PIC micelles, with sizes up to 30–70 nm, while no such multimolecular assembly is observed for siRNA b‐PICs. The entropy gain associated with the formation of a segregated PIC phase in the multimolecular PIC micelles may not be large enough for rigid siRNA strands to compensate with appreciably high steric repulsion derived from PEG chains. Chain rigidity appears to be a critical parameter in polyion complex association.
7.
Michiko Shimizu Tsuguyuki Saito Yoshiharu Nishiyama Shinichiro Iwamoto Hiroyuki Yano Akira Isogai Takashi Endo 《Macromolecular rapid communications》2016,37(19):1581-1586
The dimensions of nanocelluloses are important factors in controlling their material properties. The present study reports a fast and robust method for estimating the widths of individual nanocellulose particles based on the turbidities of their water dispersions. Seven types of nanocellulose, including short and rigid cellulose nanocrystals and long and flexible cellulose nanofibers, are prepared via different processes. Their widths are calculated from the respective turbidity plots of their water dispersions, based on the theory of light scattering by thin and long particles. The turbidity‐derived widths of the seven nanocelluloses range from 2 to 10 nm, and show good correlations with the thicknesses of nanocellulose particles spread on flat mica surfaces determined using atomic force microscopy.
8.
The nondestructive testing technique is applied to evaluate the temper embrittlement of normalized and tempered
steel; it is based on the anodic polarization behavior in calcium nitrate solution. The steel specimen is aged at a stress of 210 MPa at 450°C for up to 8800 h in order to examine the effect of applied stress on the enhancement of intergranular segregation of phosphorus. The secondary peak observed in the polarization curve for the material aged under stress was compared with that for the non-stressed. It can be quantified with the degree of intergranular segregation of phosphorus. The data suggest that the enhancement of phosphorus segregation due to the applied stress is only recognized after 3000 h of aging. This effect diminishes with increasing aging time. 相似文献
9.
10.
Xiongchao Lin Keiko Ideta Jin Miyawaki Yusuke Nishiyama Isao Mochida Seong‐Ho Yoon 《Magnetic resonance in chemistry : MRC》2012,50(4):289-294
A general strategy of structural analysis of alumina silicate by combining various solid‐state NMR measurements such as single pulse, multi‐quantum magic angle spinning, double‐quantum homo‐nuclear correlation under magic angle spinning (DQ‐MAS), and cross‐polarization hetero‐nuclear correlation (CP‐HETCOR) was evaluated with the aid of high magnetic field NMR (800 MHz for 1H Larmor frequency) by using anorthite as a model material. The high magnetic field greatly enhanced resolution of 27Al in single pulse, DQ‐MAS, and even in triple‐quantum magic angle spinning NMR spectra. The spatial proximities through dipolar couplings were probed by the DQ‐MAS methods for homo‐nuclear correlations between both 27Al–27Al and 29Si–29Si and by CP‐HETCOR for hetero‐nuclear correlations between 27Al–29Si in the anorthite framework. By combining various NMR methodologies, we elucidated detailed spatial correlations among various aluminum and silicon species in anorthite that was hard to be determined using conventional analytical methods at low magnetic field. Moreover, the presented approach is applicable to analyze other alumina‐silicate minerals. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献