全文获取类型
收费全文 | 478篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
化学 | 306篇 |
晶体学 | 6篇 |
力学 | 20篇 |
数学 | 47篇 |
物理学 | 121篇 |
出版年
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 27篇 |
2012年 | 21篇 |
2011年 | 30篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 29篇 |
2007年 | 24篇 |
2006年 | 26篇 |
2005年 | 26篇 |
2004年 | 28篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1963年 | 1篇 |
排序方式: 共有500条查询结果,搜索用时 46 毫秒
231.
A new sensitive and selective resin spot test for nanogram quantities of molybdenum(Vl) with tiron is proposed. The limit of identification is 8 ng(1:5 · 106) after 1 hour standing. Vanadium(V), chromium(VI), uraniuni(lV), titanium (IV), palladiuin(II), platinum(lV), silver(I) and gold(III) interfere. Uranium(VI) (20 ng 1:2·106) can be detected similarly. 相似文献
232.
We give examples of the interior derivative blow-up solutions for the curvature evolution of capillary surfaces over a bounded domain in .
233.
Akinori Koukitu Naoyuki Takahashi Tetsuya Taki Hisashi Seki 《Journal of Crystal Growth》1997,170(1-4):306-311
A chemical equilibrium model is applied to the growth of the InxGa1−xN alloy grown by metalorganic vapor-phase epitaxy (MOVPE). The equilibrium partial pressures and the phase diagram of deposition are calculated for the InxGa1−xN alloy. The vapor-solid distribution relationship is discussed in comparison with the experimental data reported in the literature. It is shown that the solid composition of the InxGa1−xN alloy grown by MOVPE is thermodynamically controlled and that the incorporation of group III elements into the solid phase deviates from a linear function of the input mole ratio of the group III metalorganic sources under the conditions of high mole fraction of decomposed NH3 (high value of ), high temperature and low input V/III ratio. The origin of the deviation of the solid composition from the linear relation is also discussed. 相似文献
234.
235.
Kazumasa Funabiki Naoyuki Sugiyama Ji-Ye Jin Yasutake Kato Masaki Matsui 《Journal of fluorine chemistry》2006,127(2):257-262
Four kinds of ring-fluorinated fluoresceins and sulfofluorescein from tetrafluororesorcinol and/or tetrafluorophthalic anhydride have been synthesized and the photochemical properties of the zinc oxide nanocrystalline electrode sensitized by the ring-fluorinated fluoresceins were investigated. 相似文献
236.
M Tanno H Yamada T Muraki H Tabuchi H Murata K Chiba M Asatsu Y Onodera R Chida K Someya 《Radioisotopes》1983,32(6):271-274
The present studies examine the effect of starvation together with cold or hot exposure on thyroid hormone levels in rats. At 23 degrees C starved for 5 days, serum thyroid hormone levels decreased significantly compared with fed rats, averaging 3.6 +/- 0.5 micrograms/dl of thyroxine (T4), 47 +/- 11 ng/dl of triiodothyronine (T3), 1.4 +/- 0.3 ng/dl of free T4 and 39.6 +/- 5.1 pg/ml of reverse T3, respectively. At 15 degrees C rats starved for 5 days, serum free T4 level significantly more increased than that of 23 degrees C starved rats, while serum T4 level and T3 did not increase significantly. At 30 degrees C rats whether concomitant starvation or not, serum thyroid hormone levels of both group markedly more decreased than control rats. These experiment provide additional evidence that thyroid gland and the peripheral metabolism of thyroid hormone respond to variety situations such as cold or hot exposure together with starvation or not. 相似文献
237.
Fujioka H Fujita T Kotoku N Ohba Y Nagatomi Y Hiramatsu A Kita Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(21):5386-5397
A new chiral auxiliary, a 3-endo-phenyl norbornene aldehyde derivative, which is a crystalline, very stable, and easily handled, was developed for the desymmetrization of meso-1,3- and meso-1,4-diols. The key step of the method, an intramolecular bromoetherification, proceeded in a highly diastereoselective manner. A four-step sequence, 1) acetalization, 2) intramolecular bromoetherification followed by acid hydrolysis, 3) protection of the alcohol, and 4) retrobromoetherification, transformed the meso-diols into optically active derivatives. The 3-endo-phenyl norbornene aldehyde derivative was simultaneously reformed and could be used repeatedly. This is the first chemical example of a single auxiliary that is applicable for highly enantioselective desymmetrization of meso-1,3- and meso-1,4-diols; to the best of our knowledge, this is the best chemical method available for the desymmetrization of meso-1,4-diols. 相似文献
238.
Ishida N Sakamoto M Miyahara M Higashitani K 《Journal of colloid and interface science》2002,253(1):112-116
The very strong and long-ranged interaction force between hydrophobic surfaces in water has been a debated issue for a long time. Recent studies suggest that the long-range attraction is attributable to the bridging of nanoscopic bubbles attached on the surfaces. However, it is still unclear at present whether such a bridging is able to exit stably or not. To clarify the existence of the gas bridge, we conducted the optical observation and the force measurement between the hydrophobic glass particle and plate in water simultaneously, using a combined apparatus of an atomic force microscope and an optical inverted microscope. It is found that (i) the image of the dark ring of ca. 1 mum in diameter appears in the region where the existence of the bridge is confirmed by force curves, but disappears when the separation between surfaces becomes shorter than the low limit of the wavelength of visible light, and (ii) the sudden disappearance of the image coincides well with the breakage of the bridge estimated from the separating force curve. The results obtained here are consistent with the above-mentioned mechanism for the long-range attraction between hydrophobic surfaces in water. 相似文献
239.
Masahiro Mikuriya Naoyuki Masuda Yoshihisa Kakuta Shinya Minato Takaya Inui Daisuke Yoshioka 《Chemical Papers》2016,70(1):126-130
Cobalt (III) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H2sbba) and N-salicylidene-2-hydroxy-5-chlorobenzylamine (H2scba), [n-(C4H9)4N][Co(sbba)2] (I) and [n-(C4H9)4N][Co(scba)2] (II), were synthesized. The crystal structure of II was determined by the single-crystal X-ray diffraction method at 90 K confirming its crystallization in the monoclinic space group P21/n with a = 11.729(2) Å, b = 16.901(3) Å, c = 21.483(4) Å, β = 98.840(4)°, V = 4208.2(14) Å3, Dx = 1.295 g cm?3, and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values of 0.0664 and 0.1920, respectively, for all 9521 independent reflections. The compound is composed of a tetra(n-butyl)ammonium cation and an octahedral cobalt(III) complex anion with two scba2? ligands in a meridional fashion. The electronic spectral features of I and II are consistent with the octahedral cobalt(III) ion with an N2O4 donor set. 相似文献