全文获取类型
收费全文 | 1039篇 |
免费 | 29篇 |
国内免费 | 11篇 |
专业分类
化学 | 874篇 |
晶体学 | 13篇 |
力学 | 9篇 |
数学 | 69篇 |
物理学 | 114篇 |
出版年
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 22篇 |
2014年 | 30篇 |
2013年 | 40篇 |
2012年 | 42篇 |
2011年 | 49篇 |
2010年 | 30篇 |
2009年 | 42篇 |
2008年 | 54篇 |
2007年 | 50篇 |
2006年 | 67篇 |
2005年 | 60篇 |
2004年 | 67篇 |
2003年 | 46篇 |
2002年 | 42篇 |
2001年 | 11篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 27篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 26篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 5篇 |
排序方式: 共有1079条查询结果,搜索用时 31 毫秒
121.
Oleg N. Ulenikov Eizi Hirota Mitsuru Akiyama S. Alanko M. Koivusaari R. Anttila G. Guelachvili R. N. Tolchenov 《Journal of Molecular Spectroscopy》1996,180(2):423-432
The infrared spectrum of doubly deuterated methane CH2D2has been recorded in the region from 1900 to 2400 cm−1at almost Doppler-limited resolution by using two high-resolution Fourier transform spectrometers. The vibrational bands observed include 2ν4, ν4+ ν7, 2ν7, ν2, ν8, ν4+ ν9, and ν7+ ν9, which were analyzed by taking into account Coriolis and Fermi interactions among them and also those with ν4+ ν5, ν3+ ν7, and ν5+ ν7. Most of the centrifugal distortion constants were constrained to appropriate values, while the vibrational term value and three rotational constants in each of the seven excited states were adjusted along with Coriolis and Fermi interaction parameters by the least-squares analysis of the observed spectrum. The vibration–rotation interaction constants αsthus determined for the ν2and ν8states were combined with those of other fundamental states already published to calculate the equilibrium C–H distance. 相似文献
122.
This paper deals with the critical case of the global smoothing estimates for the Schrödinger equation. Although such estimates fail for critical orders of weights and smoothing, it is shown that they are still valid if one works with operators with symbols vanishing on a certain set. The geometric meaning of this set is clarified in terms of the Hamiltonian flow of the Laplacian. The corresponding critical case of the limiting absorption principle for the resolvent is also established. Obtained results are extended to dispersive equations of Schrödinger type, to hyperbolic equations and to equations of other orders. 相似文献
123.
124.
Kazuhiko Mase Mitsuru Nagasono Shin-ichiro Tanaka Tsuneo Urisu Eiji Ikenaga Tetsuji Sekitani Ken-ichiro Tanaka 《Surface science》1997,390(1-3):97-101
Ion desorption induced by a resonant excitation of O 1s of condensed amorphous H2O has been studied by total ion and total electron yield spectroscopy, nonderivative Auger electron spectroscopy (AES) and Auger electron photo-ion coincidence (AEPICO) spectroscopy. The spectrum of total ion yield divided by total electron yield exhibits a characteristic threshold peak at hν = 533.4 eV, which is assigned to the 4a1 ← O 1s resonant transition. The AES at the 4a1 ← O 1s resonance is interpreted as being composed of the spectator-AES of the surface H2O, and the normal-AES of the bulk H2O, where the 4a1 electron is delocalized before Auger transitions. H+ is found to be the only ion species in AEPICO spectra measured at the 4a1 ← O 1s resonance and at the O 1s ionization (hν = 560 eV). The electron kinetic energy dependence of the AEPICO yield (AEPICO yield spectrum) at the 4a1 ← O 1s resonance is found to be greatly different from that at the O 1s ionization. The peak positions of the AEPICO yield spectrum at the 4a1 ← O 1s resonance are found to correspond to those of the spectator-AES of the surface H2O, which is extracted from the AES at the 4a1 ← O 1s resonance. Furthermore, the AEPICO yield is greatly enhanced at the 4a1 ← O 1s resonance as compared with that at the O 1s ionization. On the basis of these results, a spectator-Auger-stimulated ion desorption mechanism and/or ultra-fast ion desorption mechanism are concluded to be responsible for the H+ desorption at the 4a1 ← O 1s resonance. The enhancement of the H+ yield is ascribed to the O---H anti-bonding character of the 4a1 orbital. 相似文献
125.
Amornrat Lertworasirikul Yuuya Arikawa Tatsuo Kaneko Toshiyuki Kida Mitsuru Akashi 《Journal of polymer science. Part A, Polymer chemistry》2008,46(19):6489-6495
Highly flexible and transparent polylactic acids (PLAs) films were successfully prepared by manipulating their crystallization. The semicrystalline poly(L ‐lactic acid) (L) was blended with a noncrystalline poly(DL ‐lactic acid) (DL) together with diglycerol tetraacetate (DGTA). Optimal DGTA content to plasticize PLAs was about 17%. Addition of DL hindered the crystallization of the films. Tensile strengths of the films having DL content more than 5% were about 10 MPa while the elongations at break were boosted as DL content increased. Films having L/DL ratio of 50/50 showed elongations at break of 270%. Stretch ability and clarity of films containing 15–50% DL were fair although they were subjected to annealing at 60 °C for 1 h. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6489–6495, 2008 相似文献
126.
Koichiro Yonetake Kunio Maruyama Jun-Ichi Sugiyama Toru Masuko Mitsuru Ueda 《Journal of polymer science. Part A, Polymer chemistry》1994,32(8):1415-1421
Poly[4-(4-hydroxyphenoxy) benzoic acid] was prepared by the bulk polycondensation of 4-(4-acetoxyphenoxy) benzoic acid. Polycondensation was conducted at 350°C for 3 h under a reduced pressure of 0.1 mmHg and gave a polymer with X?n of 255. The polymer was characterized by elemental analysis, IR spectroscopy, differential scanning calorimetry, and wide-angle X-ray measurement. The crystal/nematic and nematic/isotropic phase transition temperatures of polymer, which depend on the molecular weight, were observed at about 300°C and 410°C, respectively. The polymers with low molecular weights showed nematic textures above 300°C. This nematic/isotropic phase transition temperature is lower than that of poly (4-hydroxybenzoic acid). This thermal behavior of polymer comes from ether units, which increase the flexibility (the rotation or torsion of skeletal bonds) of the polymer chain. © 1994 John Wiley & Sons, Inc. 相似文献
127.
128.
Mitsuru Nakayama Hiroshi Yamaoka Shizuko Eguchi Terukiyo Hanafusa Shûichi Hayashi 《Journal of mass spectrometry : JMS》1977,12(6):416-417
For some homochromones, it was confirmed by labelling C-9 with deuterium that the CHO radical expelled from the molecular ion contains either the methine hydrogen or one of the methylene hydrogens of the cyclopropane ring. The origin of the CO group in the expelled CHO radical was also inferred, and a plausible mechanistic interpretation is presented. 相似文献
129.
130.
The Dirichlet irregularity of the origin which is a boundary point of a Zalcman domainR is shown to be sufficient but not necessary for the occurrence of the Myrberg phenomenonH
∞
(R) =H
∞
(R) o φ for a two-sheeted unlimited smooth covering surface~R ofR with projection mapφ. The importance of the uniqueness theorem in such a study of the Myrberg phenomenon is stressed. A condition under which
the Myrberg phenomenon fails for the covering surface (~R, R, φ) is also considered.
To complete the present work the first (second, resp.) named author was supported in part by Grant-in-Aid for Scientific Research,
No. 07640154 (07640196, 08640194, 09640180, 09640230, resp.), Japanese Ministry of Education, Science and Culture. 相似文献