全文获取类型
收费全文 | 2096篇 |
免费 | 43篇 |
国内免费 | 5篇 |
专业分类
化学 | 1508篇 |
晶体学 | 34篇 |
力学 | 20篇 |
数学 | 90篇 |
物理学 | 492篇 |
出版年
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 20篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 36篇 |
2015年 | 26篇 |
2014年 | 29篇 |
2013年 | 101篇 |
2012年 | 86篇 |
2011年 | 98篇 |
2010年 | 66篇 |
2009年 | 55篇 |
2008年 | 107篇 |
2007年 | 110篇 |
2006年 | 118篇 |
2005年 | 117篇 |
2004年 | 107篇 |
2003年 | 72篇 |
2002年 | 68篇 |
2001年 | 64篇 |
2000年 | 43篇 |
1999年 | 35篇 |
1998年 | 20篇 |
1997年 | 28篇 |
1996年 | 40篇 |
1995年 | 27篇 |
1994年 | 22篇 |
1993年 | 19篇 |
1992年 | 30篇 |
1991年 | 29篇 |
1990年 | 24篇 |
1989年 | 18篇 |
1988年 | 27篇 |
1987年 | 24篇 |
1986年 | 23篇 |
1985年 | 35篇 |
1984年 | 38篇 |
1983年 | 35篇 |
1982年 | 21篇 |
1981年 | 28篇 |
1980年 | 17篇 |
1979年 | 28篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 21篇 |
1975年 | 20篇 |
1974年 | 11篇 |
1973年 | 10篇 |
1967年 | 11篇 |
排序方式: 共有2144条查询结果,搜索用时 15 毫秒
181.
Hawthorn DG Hill RW Proust C Ronning F Sutherland M Boaknin E Lupien C Tanatar MA Paglione J Wakimoto S Zhang H Taillefer L Kimura T Nohara M Takagi H Hussey NE 《Physical review letters》2003,90(19):197004
The transport of heat and charge in cuprates was measured in single crystals of La(2-x)Sr(x)CuO(4+delta) (LSCO) across the doping phase diagram at low temperatures. In underdoped LSCO, the thermal conductivity is found to decrease with increasing magnetic field in the T-->0 limit, in striking contrast to the increase observed in all superconductors, including cuprates at higher doping. In heavily underdoped LSCO, where superconductivity can be entirely suppressed with an applied magnetic field, we show that a novel thermal metal-to-insulator transition takes place upon going from the superconducting state to the field-induced normal state. 相似文献
182.
Kimura M Wada K Iwashima Y Ohta K Hanabusa K Shirai H Kobayashi N 《Chemical communications (Cambridge, England)》2003,(19):2504-2505
Sol-gel polymerization of tetraethoxysilane in the presence of amphiphilic phthalocyanine polymer 2 produced organic-inorganic composites with the rod-like phthalocaynine polymers incorporated within ordered hexagonal channels. 相似文献
183.
Akaike S Sumino M Sekine T Seo S Kimura N Ikegami F 《Chemical & pharmaceutical bulletin》2003,51(2):197-199
A new ent-clerodane diterpene, named bacchariol (1) was isolated from the aerial parts of Baccharis gaudichaudiana DC. (Compositae), together with known ent-clerodane diterpenes (2, 3), eight known flavonoids (4-11) and 3, 5-dicaffeoylquinic acid (12). Their structures were determined by spectroscopic analyses. Flavonoids (7, 8, 11) and 12 showed moderate scavenging activities toward 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radicals. 相似文献
184.
Kimura M Sakaguchi A Ohta K Hanabusa K Shirai H Kobayashi N 《Inorganic chemistry》2003,42(9):2821-2823
A new class of sterically hindered phthalocyanine has been synthesized and characterized. Pentaphenylbenzene units were introduced at the periphery of each phthalocyanine to yield a sterically protected metal center. The attachment of the bulky oligophenylbenzene units resulted in the complete isolation of individual MPc molecules. The pockets around a cobalt center affect selectivity in the ligation of pyridines that have different sizes and shapes. 相似文献
185.
186.
Kimura T Yao S Watanabe K Kondo S Ho IK Yamamoto I 《Chemical & pharmaceutical bulletin》2001,49(1):111-113
Methyl (2), ethyl (3), propyl (4), butyl (5), allyl (6), benzyl (7), o-, m-, p-xylyl (8-10), and alpha-phenylethyl (11) derivatives of arabinofuranosyluracil (1) were synthesized and their pharmacological effects in mice were examined by using hypnotic activity and synergism with pentobarbital as indices for the CNS depressant effects. At a dose of 2.0 micromol/mouse by intracerebroventricular injection, the values of mean sleeping time induced by 7-11 were 144, 154, 117, 33, and 34 min, respectively, whereas the alkyl (2-6) derivatives did not cause any hypnotic activity. N3-o-Xylylarabinofuranosyluracil (8) displayed the most potent hypnotic activity among the derivatives tested. Certain derivatives (6-11) significantly prolonged the pentobarbital-induced sleeping time compared to control. The present study indicated that substitution with benzyl and/or related groups on the N3-position of arabinofuranosyluracil produced CNS depressant effects. 相似文献
187.
188.
Suzuki M Waraksa CC Nakayama H Hanabusa K Kimura M Shirai H 《Chemical communications (Cambridge, England)》2001,(19):2012-2013
L-Lysine derivatives of viologens form supramolecular assemblies of fibers and ribbons in some aromatic solvents, and the charge separation reaction in these self-assembling systems proceeds with a similar efficiency to the MV2+ system. 相似文献
189.
A single-atom-sized gold wire was successfully observed in real time by a newly developed defocus-image modulation processing electron microscope. Because of phase retrieval processing with spherical aberration correction, the single-atom strand wire was observed with high contrast and without contrast blurring. By carefully looking at the atomic distance, the contrast, and the dynamic behavior of the wire, we recognized that there are two stages of the wire. In the first stage the wire maintained the atomic distance in the bulk crystal, but in the second stage the wire showed the atomic distance of the nearest-neighbor atoms with weaker contrast. The gold wire was rather stable for a few seconds under strong electron beam illumination. 相似文献
190.
Fujiwara H Kimura A Yanagawa Y Kamiya T Hattori M Hiraga T 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,150(2):156-160
Size dependency of the relaxation time T(1) was measured for laser-polarized (129)Xe gas encapsulated in different sized cavities made by glass bulbs or gelatin capsules. The use of laser-polarized gas enhances the sensitivity a great deal, making it possible to measure the longer (129)Xe relaxation time in quite a short time. The size dependency is analyzed on the basis of the kinetic theory of gases and a relationship is derived in which the relaxation rate is connected with the square inverse of the diameter of the cavity. Such an analysis provides a novel parameter which denotes the wall effect on the relaxation rate when a gas molecule collides with the surface once in a second. The relaxation time of (129)Xe gas is also dependent on the material which forms the cavity. This dependency is large and the relaxation study using polarized (129)Xe gas is expected to offer important information about the state of the matter of the cavity wall. 相似文献