全文获取类型
收费全文 | 3540篇 |
免费 | 91篇 |
国内免费 | 8篇 |
专业分类
化学 | 2822篇 |
晶体学 | 24篇 |
力学 | 39篇 |
数学 | 172篇 |
物理学 | 582篇 |
出版年
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 42篇 |
2019年 | 54篇 |
2018年 | 34篇 |
2017年 | 20篇 |
2016年 | 55篇 |
2015年 | 51篇 |
2014年 | 74篇 |
2013年 | 158篇 |
2012年 | 132篇 |
2011年 | 206篇 |
2010年 | 74篇 |
2009年 | 93篇 |
2008年 | 174篇 |
2007年 | 182篇 |
2006年 | 174篇 |
2005年 | 212篇 |
2004年 | 163篇 |
2003年 | 128篇 |
2002年 | 138篇 |
2001年 | 112篇 |
2000年 | 138篇 |
1999年 | 49篇 |
1998年 | 38篇 |
1997年 | 34篇 |
1996年 | 56篇 |
1995年 | 30篇 |
1994年 | 48篇 |
1993年 | 36篇 |
1992年 | 50篇 |
1991年 | 44篇 |
1990年 | 39篇 |
1989年 | 39篇 |
1988年 | 53篇 |
1987年 | 43篇 |
1986年 | 61篇 |
1985年 | 54篇 |
1984年 | 56篇 |
1983年 | 31篇 |
1982年 | 34篇 |
1981年 | 36篇 |
1980年 | 30篇 |
1979年 | 31篇 |
1978年 | 28篇 |
1977年 | 26篇 |
1976年 | 21篇 |
1975年 | 32篇 |
1974年 | 28篇 |
1972年 | 21篇 |
排序方式: 共有3639条查询结果,搜索用时 9 毫秒
141.
Prof. Dr. Yasuchika Hasegawa Takafumi Matsui Dr. Yuichi Kitagawa Dr. Takayuki Nakanishi Dr. Tomohiro Seki Prof. Dr. Hajime Ito Prof. Dr. Yuta Nakasaka Prof. Dr. Takao Masuda Prof. Dr. Koji Fushimi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12308-12315
Oxygen-sensitive and near-infrared (NIR) luminescent YbIII coordination polymers incorporating ligands based on pyrene derivatives were synthesized: YbIII–TBAPy and YbIII–TIAPy (TBAPy: 1,3,6,8-tetrakis(p-benzoate)pyrene; TIAPy: 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene). The coordination structures of these materials have been characterized by means of electrospray ionization mass spectrometry, X-ray diffraction analysis, and thermogravimetric analysis. Moreover, the porous structure of YbIII–TIAPy has been evaluated by measuring its N2 adsorption isotherm. The NIR luminescence properties of YbIII–TBAPy and YbIII–TIAPy have been examined by acquiring emission spectra and determining emission lifetimes under air or argon and in vacuo. YbIII–TIAPy exhibited high thermal stability (with a decomposition temperature of 400 °C), intense luminescence (with an emission quantum yield under argon of 6.6 %), and effective oxygen-sensing characteristics. These results suggest that NIR luminescent YbIII coordination polymers prepared using pyrene derivatives could have applications in novel thermo-stable oxygen sensors. 相似文献
142.
Wenjie Tao Xiaoming Wang Shingo Ito Kyoko Nozaki 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):474-477
Herein, we report the synthesis of palladium complexes bearing an N‐heterocyclic carbene (NHC)‐sulfonamide bidentate ligand and their application in ethylene oligomerization and ethylene/polar monomer cooligomerization. These catalysts could smoothly catalyze ethylene oligomerization and ethylene/methyl acrylate cooligomerization albeit the performance was lower compared to that of a NHC–phenoxide catalyst. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 474–477 相似文献
143.
Dr. Yusaku Nomura Dr. Frédéric Thuaud Dr. Daisuke Sekine Prof. Dr. Akihiro Ito Satoko Maeda Dr. Hiroyuki Koshino Dr. Daisuke Hashizume Dr. Atsuya Muranaka Dr. Thomas Cruchter Prof. Dr. Masanobu Uchiyama Prof. Dr. Satoshi Ichikawa Prof. Dr. Akira Matsuda Prof. Dr. Minoru Yoshida Prof. Dr. Go Hirai Prof. Dr. Mikiko Sodeoka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(35):8387-8392
A synthetic methodology to access all possible stereoisomers of spectomycin A1 (SMA1) and A2 (SMA2) has been established through late-stage diversification. The key reaction for the construction of all four diastereomers is an intramolecular cyclization based on the umpolung of π-allyl palladium species with bis(pinacolato)diborane (B2(pin)2). Silyl group assisted direct benzylic oxidation of each isomer enabled construction of the fragile β-hydroxytetralone skeleton to provide the SMAs. The relative and absolute stereochemistry of SMA2 was also determined, and the absolute stereochemistry of SMA1 was extrapolated based on the optical rotation of SMA2. The axial chirality of SMAs is discussed based on circular dichroism spectra and DFT calculations, and it is concluded that the M isomer is predominant in solution. Biochemical assessment of all isomers in vitro revealed that the C9 hydroxyl group and dimeric structure were both important for protein SUMOylation-inhibitory activity. 相似文献
144.
Dr. Yui Sasaki Satoshi Ito Zhoujie Zhang Xiaojun Lyu Dr. Shin-ya Takizawa Dr. Riku Kubota Prof. Dr. Tsuyoshi Minami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16236-16240
An artificial tongue that detects astringent components for a comprehensive evaluation of taste has not been established to date. Herein, we first propose fluorescent polythiophene (PT) derivatives ( S1 – S3 ) modified with 3-pyridinium boronic acid as supramolecular chemosensors for wine components including astringent procyanidin C1. After numerous attempts for the synthetic conditions, more than 95 mol % of the PT unit was modified with the pyridinium boronic acid moiety. To evaluate the PT derivatives as chemosensors of the artificial tongue, qualitative and quantitative analyses were performed with four types of wine components (i.e., sweet, sour, bitter, and astringent tastes) in combination with pattern recognition models. Notably, procyanidin C1 in the actual wine sample was successfully detected in a quantitative manner. In other words, we have established an authentic artificial tongue using PT based supramolecular chemosensors. 相似文献
145.
Katsuro Oda Nobusato Kojima Kunio Ito Hiromitsu Ino Setsuo Kajiwara 《Hyperfine Interactions》1990,54(1-4):853-859
A Mössbauer effect measurement has been done for Fe?N, Fe?Al?C and Fe?Ni?C austenite in order to study the interaction between the interstitial atoms and their distribution among the octahedral sites of the fcc lattice, together with the influence of Al and Ni atoms. The spectra for Fe?N and Fe?Al?C austenite are decomposed into three components; one singlet γ0, and two sets of doublet γ1 and γ2, with different quadrupole splittings, while no γ2 component is found in the spectrum for Fe?Ni?C. By analyzing the component ratio in each spectrum, it is concluded that, in Fe?N and Fe?Al?C, the interaction between 2nd nearest neighboring nitrogen or carbon atoms is attractive, and is repulsive between 1st nearest for Fe?N, and that the interaction between 2nd nearest atoms is repulsive for Fe?Ni?C. By measuring the spectra of Fe?Ni?C in magnetic field, the sign of EFG for most of the γ1 component is determined to be negative. 相似文献
146.
Yasuhiko Syono Atsuko Ito Setsu Morimoto 《Journal of Physics and Chemistry of Solids》1981,42(6):483-486
The Mössbauer spectra of ilmenite (FeTiO3), Fe2+-doped ilmenites, MTiO3 (M = Cd, Mn, Zn, Co, Mg and Ni) and MGeO3 (M = Mn, Zn and Mg), have been studied from 4.2 K to room temperature. Systematic variations in the isomer shift and quadrupole splitting at room temperature are correlated with the change in ionic radii of the host M ions and the c/a ratio of the host crystal, respectively. The quadrupole splittings show a remarkable temperature variation; the magnetic ilmenites show either a sudden increase or a sudden decrease of quadrupole splittings below the Néel temperature, depending on the orientation of the spin axis with respect to the c axis. 相似文献
147.
Semiconductor diamond is considered the best heater material to generate ultra-high temperatures in a Kawai cell. In two pioneering studies, a mixture of graphite and amorphous boron (or boron carbide, B4C) was converted to semiconductor diamond in the diamond stability field and was confirmed to generate 2000°C and 3500°C, respectively. Following these works, we synthesized a homemade boron-doped graphite block with fine machinability. With this technical breakthrough, we developed a semiconductor diamond heater in a smaller Kawai-type cell assembly. Here, we report the procedure for making machinable boron-doped graphite, and the performance of the material as a heater in a Kawai cell at 15?GPa using tungsten carbide anvils and at ~50?GPa using sintered diamond anvils. Furthermore, we present a finite element simulation of the temperature distribution generated by a semiconductor diamond heater, which is much more homogeneous than that generated by a metal heater. 相似文献
148.
Hashi K Shimizu T Goto A Kiyoshi T Matsumoto S Wada H Fujito T Hasegawa K Yoshikawa M Miki T Ito S Hamada M Hayashi S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):318-321
We have developed a 920-MHz NMR system and performed the proton NMR measurement of H(2)O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR. 相似文献
149.
We present a design technique of retarders suitable for nonlinear optical systems. A thin sample of LiNbO3 crystal is utilized as a retarder for wide-ranging applications. Analysis shows that the same crystal can be used for single-wave or two-wave retardations, changing the orientation of the crystal only. As an application, the retarder is used to polarize two waves orthogonal, as necessary for difference frequency mixing in an AgGaSe2 crystal. 相似文献
150.
S. Ito 《Applied physics. B, Lasers and optics》1996,63(1):1-7
Continuous operations at a high repetition rate up to 3 kHz for discharge-pumped XeCl excimer laser are presented. The dependence of the clearing ratio on laser-gas pressure and input energy densities is studied. It was found that suitable laser-gas pressures minimize the clearing ratio for various input-energy densities. It is also shown that few density disturbances in the discharge region are induced by gas heating in a discharge-pumped XeCl excimer laser with low input-energy density 相似文献