全文获取类型
收费全文 | 195篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 169篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 9篇 |
物理学 | 26篇 |
出版年
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1976年 | 6篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 6篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有207条查询结果,搜索用时 343 毫秒
121.
122.
Makio Iwahashi Motonari Ikumi Hideyo Matsuzawa Yoshikiyo Moroi Mirosaw A. Czarnecki Yukihiro Ozaki 《Vibrational Spectroscopy》1999,20(2):2489-119
The self-association of (R)-, (S)- and (RS)-butan-2-ol in their carbon tetrachloride solutions was studied through the mid-infrared (mid-IR) and near-infrared (NIR) spectroscopic observations. The mid-IR and NIR spectra for each chiral butan-2-ol were compared with those for the racemic (RS)-butan-2-ol. Although it has been reported that the hydrogen bonding among the chiral butan-2-ol molecules was stronger than that among the racemic ones, any distinguishable differences between the chiral and the racemic butan-2-ol in CCl4 solution or even in their pure liquid state were not observed both in their mid-IR and NIR spectra. A superior analytical method, assuming a successive association process for the alcohol molecules, was applied to the analysis of the sharp band at 3630 cm−1 (the OH-stretching vibration mode attributed to free OH-monomer) for the (R)-, (S)- or (RS)-butan-2-ol in CCl4. The mean association number N for each alcohol increased with increasing in concentration until 0.12 mol dm−3 and then becomes constant (about four). On the other hand, Zanker's plotting method, assuming an equilibrium between monomers and only one kind of polymer species, was also applied to the analysis of the above spectroscopic results; the association number n evaluated from the Zanker's method fairly agreed with the N value in the concentration region of 0.12–0.60 mol dm−3. 相似文献
123.
Mayumi Chida Satoru Takahashi Ryunosuke Konishi Dr. Takeshi Matsumoto Dr. Akinobu Nakada Dr. Masanori Wakizaka Dr. Wataru Kosaka Prof. Hitoshi Miyasaka Prof. Ho-Chol Chang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(66):16354-16366
The combination of a cobalt-dioxolene core that exhibits valence tautomerism (VT) with pyridine-3,5-dicarboxylic acid functionalized with chains bearing two, four, or six oxyethylene units led to new complexes ConEGEspy (n = 2, 4, and 6). These complexes commonly form violet crystals of the low-spin (ls)-[CoIII(nEGEspy)2(3,6-DTBSQ)(3,6-DTBCat)] (ls-[CoIII], 3,6-DTBSQ = 3,6-di-tert-butyl semiquinonato, 3,6-DTBCat = 3,6-di-tert-butyl catecholato). Interestingly, violet crystals of Co2EGEspy in the ls-[CoIII] transitioned into a green liquid, accompanied by an almost complete VT shift (94 %) to the high-spin (hs)-[CoII(nEGEspy)2(3,6-DTBSQ)2] (hs-[CoII]) upon melting. In contrast, violet crystals of Co4EGEspy and Co6EGEspy in the ls-[CoIII] exhibited partial VT (33 %) and only a 9.3 % VT shift after melting, respectively. These data demonstrate the tunability of the synchronicity of the molecular VT and macroscopic solid-liquid transitions by optimizing the tethered chains, thus establishing a new strategy for coupling bistable molecules with the macroscopic world. 相似文献
124.
Hiroshi Kobayashi Youkoh Kaizu Hitoshi Kimura Hideyo Matsuzawa Hirohiko Adachi 《Molecular physics》2013,111(6):1009-1030
The DV-Xα molecular-orbital calculations have been carried out on [Crbpy(CO)4](bpy,2,2′-bipyridine) and its electron attachment and detachment products. The one-electron attachment of [Crbpy(CO)4] yields a complex of bipyridine anion radical, while the one-electron detachment results in ionization of the central metal atom. The lowest excited state of [Crbpy(CO)4] is the metal-to-ligand charge-transfer (MLCT) excited state which consists of the bipyridine anion radical and the central metal ionized. The transition-state calculation predicts the lowest MLCT excited states at around 23~30×103 cm?1 and the lowest bipyridine (π,π*) excitations at 36×103 cm?1 and 42~45×103 cm?1. The calculation also concludes that the MLCT excitation induces a counter migration of the other electrons not directly involved in the charge-transfer excitation. The configuration-interaction calculations predict the lowest MLCT excited singlet states at around 21~35×103 cm?1 and the lowest bipyridine (π, π*) excited singlet states at 42~62×103 cm?1, while the emissive lowest MLCT triplet state is at 17×103 cm?1. The transition moments evaluated with the transition-state wavefunctions can reproduce qualitatively the observed absorption spectral profile. The intensity of the MLCT transitions is obtained from the allowed (π, π*) transitions of coordinated bipyridine but is not due to the intrinsic transition moments of MLCT excitations. 相似文献
125.
Masahiro Isaka Hiroaki Homma Masaaki Kimura Akinobu Dote Akira Ohnishi 《Few-Body Systems》2013,54(7-10):1219-1222
The low-lying level structure of ${^{10}_\Lambda{\rm Be}}$ and ${^{12}_\Lambda{\rm Be}}$ has been studied by using the antisymmetrized molecular dynamics for hypernuclei (HyperAMD). In these hypernuclei, it is interesting to reveal the changes of excitation spectra by adding Λ hyperon, because the ground and low-lying states with different deformation coexist in 9Be and 11Be. Based on the HyperAMD calculation, it is found that the first excited state 1/2+ of 9Be is shifted up by about 700 keV in ${^{10}_\Lambda{\rm Be}}$ . In ${^{12}_\Lambda{\rm Be}}$ , the parity-inverted ground state of 11Be is reverted by adding Λ hyperon. In this article, we discuss the reason for these structure changes related to the coexistence of ground and low-lying states with different deformation. 相似文献
126.
Hiroyuki Kawano Tatsuki Okamoto Taku Matsuzawa Hajime Nakajima Junko Makita Yoshitaka Toyoda Tetsuo Funakura Takahito Nakanishi Tatsuya Kunieda Tadashi Minobe 《Optical Review》2013,20(2):254-258
We designed a compact and large depth of field image scanner targeted for auto document feeders (ADF) by using a compound eye system design with plural optical units in which the ray paths are folded by a reflective optics. Though we have previously proposed the principle concept, we advance the design using a free-form surface mirror to reduce the F-number for less illumination energy and to shrink its optical track width to 40 mm. We achieved large depth of field (DOF) of 1.2 mm, defined as a range exceeding 30% modulation transfer function (MTF) at 300 dpi, which is about twice as large as a conventional gradient index (GRIN) lens array contact image sensor (CIS). The aperture stop has a rectangular-shaped aperture, where one side length is as large as 4.0mm for collecting much light, and another side length is as small as 1.88mm for avoiding interference of folded ray paths. 相似文献
127.
The crystallization of poly(vinyl alcohol), derived from its aqueous solution was carried out under a steady-state flow. The effect of the rate of stirring on the crystallization and details of several phenomena observed in stirred solutions during crystallization are presented. Moreover, the structure of crystallized poly(vinyl alcohol) was studied with use of an electron microscope. Evidence is presented for a crystal morphology that includes smooth fibrils and the absence of lamellar overgrowth, i.e., no shish kebabs. 相似文献
128.
F. Nannelli V. S. U. Fazio Y. Matsuzawa L. Komitov K. Ichimura 《Molecular Crystals and Liquid Crystals》2013,570(1):621-630
Abstract Many nematic liquid crystals (NLCs) lack a polar headgroup and thus are not able to form stable monolayers at the air/water (a/w) interface. A way to obtain monomolecular films of these compounds is to incorporate them into host monolayers of amphiphilic molecules. We report a comparative investigation of mixed films of Calix[4]resorcinarene O-octacarboxymethylated (CRO) with the non-amphiphilic NLC MBBA and with the amphiphilic stearic acid (SA). The comparative study is useful for a better understanding of the characteristics of the CRO-MBBA mixed films. Surface-pressure and surface-potential measurements on the monolayers at a/w interface, as well as ellipsometric and spectroscopic measurements on transferred Langmuir-Blodgett (LB) films, confirm that MBBA is additively incorporated into CRO films. 相似文献
129.
Ohta K Sadayama S Togo A Higashi R Tanoue R Nakamura K 《Micron (Oxford, England : 1993)》2012,43(5):612-620
The beam deceleration (BD) method for scanning electron microscopes (SEM) also referred to as "retarding" was applied to back-scattered electron (BSE) imaging of the flat block face of a resin embedded biological specimen under low accelerating voltage and low beam current conditions. BSE imaging was performed with 0-4 kV of BD on en bloc stained rat hepatocyte. BD drastically enhanced the compositional contrast of the specimen and also improved the resolution at low landing energy levels (1.5-3 keV) and a low beam current (10 pA). These effects also functioned in long working distance observation, however, stage tilting caused uncorrectable astigmatism in BD observation. Stage tilting is mechanically required for a FIB/SEM, so we designed a novel specimen holder to minimize the unfavorable tilting effect. The FIB/SEM 3D reconstruction using the new holder showed a reasonable contrast and resolution high enough to analyze individual cell organelles and also the mitochondrial cristae structures (~5 nm) of the hepatocyte. These results indicate the advantages of BD for block face imaging of biological materials such as cells and tissues under low-voltage and low beam current conditions. 相似文献
130.
A chiral tetrathiafulvalene (TTF) dimer bridged by an allene framework (1) was synthesized. An X-ray analysis of 1 revealed an effective conjugation between TTF and the allene backbone. Allene 1 was resolved into both enantiomers, which showed strong chiroptical electrochromic properties. Absolute configuration of the allene was validated by theoretical study of the electronic circular dichroism (ECD) spectrum. ECD spectra of cationic species 1(2+) and 1(4+) exhibited intense Cotton Effects over the visible region. 相似文献