全文获取类型
收费全文 | 1525篇 |
免费 | 92篇 |
国内免费 | 111篇 |
专业分类
化学 | 957篇 |
晶体学 | 22篇 |
力学 | 49篇 |
综合类 | 12篇 |
数学 | 117篇 |
物理学 | 571篇 |
出版年
2023年 | 8篇 |
2022年 | 28篇 |
2021年 | 27篇 |
2020年 | 28篇 |
2019年 | 20篇 |
2018年 | 18篇 |
2017年 | 33篇 |
2016年 | 46篇 |
2015年 | 39篇 |
2014年 | 42篇 |
2013年 | 94篇 |
2012年 | 98篇 |
2011年 | 122篇 |
2010年 | 85篇 |
2009年 | 76篇 |
2008年 | 109篇 |
2007年 | 99篇 |
2006年 | 102篇 |
2005年 | 91篇 |
2004年 | 59篇 |
2003年 | 44篇 |
2002年 | 53篇 |
2001年 | 31篇 |
2000年 | 31篇 |
1999年 | 26篇 |
1998年 | 15篇 |
1997年 | 14篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有1728条查询结果,搜索用时 15 毫秒
961.
962.
963.
The interplay of surface ordering and segregation at the (001) surface of Cu3Au is studied. The calculations are carried out using the tetrahedron approximation of the cluster variation method. The almost continuous disordering observed by low-energy electron diffraction and the Au enrichment observed by low-energy ion scattering spectroscopy can be consistently and accurately reproduced by our model. 相似文献
964.
J. A. Hodges P. Imbert J. B. Marimon da Cunha J. P. Sanchez 《Hyperfine Interactions》1989,50(1-4):569-574
Superconducting and non-superconducting samples of DyBa2Cu3O7?x have been examined by Mössbauer spectroscopy down to 0.05 K. The saturated Dy3+ sublattice 4f shell magnetic moments and quadrupole interactions show fairly wide distributions in both samples. These are attributed to crystal field inhomogeneities. Neither the Dy3+ paramagnetic relaxation rates nor the isomer shifts show any evidence of coupling between Dy3+ and a possible conduction band. 相似文献
965.
966.
V. Petraccone I. C. Sanchez R. S. Stein 《Journal of Polymer Science.Polymer Physics》1975,13(10):1991-2029
A theory for amorphous orientation in spherulitic polymers is presented based upon a consideration of conformational changes in the chains, loops, and cilia located between crystalline lamellae within a spherulite which is assumed to undergo an affine deformation. Chain statistics are worked out on the basis of (a) an analytical method involving random walks on a cubic lattice between barriers following a technique proposed by DiMarzio and Rubin and (b) a Monte Carlo computer simulation on a tetrahedral lattice. The latter method is considered more appropriate in view of the chain constraints such that lattice geometry becomes important. Values of the amorphous orientation are calculated as a function of the degree of crystallinity, initial lamellar separation, mole fraction of bonds in amorphous chains of each type, and chain lengths of each type of amorphous chain. It is found that tie chains are the principal contributor to amorphous orientation and the amount increases with increasing fraction and decreasing length of these. Results are compared with measurements of amorphous orientation by the birefringence x-ray and the infrared dichroism technique. It is concluded that the tie chains must be initially quite highly elongated and that the assumed affineness of spherulite deformation is not closely obeyed. 相似文献
967.
The spin liquid properties of Gd3Ga5O12 have been examined using 155Gd M?ssbauer spectroscopy down to 0.027 K. Information has been obtained concerning both the directional properties of the short range correlated moments and the thermal dependence of their spin fluctuation rates. Each Gd3+ spin (S=7/2) is found to be confined to a plane and its fluctuation rate decreases from approximately 2.8 x 10(9) s(-1) at 0.4 K to approximately 0.03 x 10(9) s(-1) at 0.09 K following a close-to-quadratic thermal dependence. 相似文献
968.
Boissiere C Grosso D Amenitsch H Gibaud A Coupé A Baccile N Sanchez C 《Chemical communications (Cambridge, England)》2003,(22):2798-2799
Meso-organisation of SiO2 and TiO2 particles prepared by spray drying have been for the first time analysed through in-situ SAXS. Both processing and chemical parameters are critical to obtain meso-organised spheres. 相似文献
969.
Laura Schioppa Dr. Claire Beaufay Dr. Natacha Bonneau Dr. Marianela Sanchez Dr. Cynthia Girardi Dr. Aurélie Leverrier Dr. Sergio Ortiz Prof. Jorge Palermo Prof. Jacques H. Poupaert Prof. Joëlle Quetin-Leclercq 《ChemistryOpen》2021,10(9):896-903
Research for innovative drugs is crucial to contribute to parasitic infections control and eradication. Inspired by natural antiprotozoal triterpenes, a library of 12 hemisynthetic 3-O-arylalkyl esters was derived from ursolic and oleanolic acids through one-step synthesis. Compounds were tested on Trypanosoma, Leishmania and the WI38 cell line alongside with a set of triterpenic acids. Results showed that the triterpenic C3 esterification keeps the antitrypanosomal activity (IC50≈1.6–5.5 μm ) while reducing the cytotoxicity compared to parent acids. Unsaturation of the ester alkyl chain leads to an activity loss interestingly kept when a sterically hindered group replaces the double bond or shields the ester group. An ursane/oleanane C3 hydroxylation was the only important feature for antileishmanial activity. Two candidates, dihydrocinnamoyl and 2-fluorophenylpropionyl ursolic acids, were tested on an acute mouse model of African trypanosomiasis with significant parasitemia reduction at day 5 post-infection for the dihydrocinnamoyl derivative. Further evaluation on other alkyl/protective groups should be investigated both in vitro and in vivo. 相似文献
970.
采用分子束外延(MBE)方法在Ba F_2(111)衬底上直接外延生长了Pb Te薄膜。反射高能电子衍射(RHEED)实时监控的衍射图样揭示了Pb Te在Ba F_2(111)表面由三维生长向二维生长的变化过程。转动对称性的研究结合第一性原理密度泛函理论(DFT)的计算揭示了在富Pb及衬底温度(Tsub)为350°C的生长条件下,得到的Pb Te(111)薄膜具有稳定的(2×1)重构表面。Pb Te(111)-(2×1)表面覆盖Te膜后,通过300°C的退火处理,重构表面可完全复原,这为大气环境下Pb Te薄膜表面结构的保护提供了有效的方法。 相似文献