全文获取类型
收费全文 | 8273篇 |
免费 | 391篇 |
国内免费 | 42篇 |
专业分类
化学 | 5723篇 |
晶体学 | 58篇 |
力学 | 151篇 |
综合类 | 1篇 |
数学 | 1249篇 |
物理学 | 1524篇 |
出版年
2023年 | 67篇 |
2022年 | 93篇 |
2021年 | 146篇 |
2020年 | 204篇 |
2019年 | 205篇 |
2018年 | 134篇 |
2017年 | 125篇 |
2016年 | 314篇 |
2015年 | 247篇 |
2014年 | 267篇 |
2013年 | 460篇 |
2012年 | 525篇 |
2011年 | 674篇 |
2010年 | 309篇 |
2009年 | 233篇 |
2008年 | 487篇 |
2007年 | 467篇 |
2006年 | 432篇 |
2005年 | 446篇 |
2004年 | 329篇 |
2003年 | 243篇 |
2002年 | 223篇 |
2001年 | 103篇 |
2000年 | 77篇 |
1999年 | 63篇 |
1998年 | 78篇 |
1997年 | 64篇 |
1996年 | 107篇 |
1995年 | 87篇 |
1994年 | 94篇 |
1993年 | 87篇 |
1992年 | 77篇 |
1991年 | 44篇 |
1990年 | 48篇 |
1989年 | 49篇 |
1988年 | 50篇 |
1987年 | 42篇 |
1986年 | 43篇 |
1985年 | 50篇 |
1984年 | 50篇 |
1983年 | 40篇 |
1982年 | 46篇 |
1981年 | 62篇 |
1980年 | 48篇 |
1979年 | 52篇 |
1978年 | 38篇 |
1977年 | 49篇 |
1976年 | 43篇 |
1974年 | 41篇 |
1973年 | 68篇 |
排序方式: 共有8706条查询结果,搜索用时 31 毫秒
11.
Shigeyuki Toki Igors Sics Benjamin S. Hsiao Syozo Murakami Masatoshi Tosaka Sirilux Poompradub Shinzo Kohjiya Yuko Ikeda 《Journal of Polymer Science.Polymer Physics》2004,42(6):956-964
The molecular orientation and strain‐induced crystallization of synthetic rubbers—polyisoprene rubber, polybutadiene rubber, and butyl rubber [poly(isobutylene isoprene)]—during uniaxial deformation were studied with in situ synchrotron wide‐angle X‐ray diffraction. The high intensity of the synchrotron X‐rays and the new data analysis method made it possible to estimate the mass fractions of the strain‐induced crystals and amorphous chain segments in both the oriented and unoriented states. Contrary to the conventional concept, the majority of the molecules (50–75%) remained in an unoriented amorphous state at high strains. Each synthetic rubber showed a different behavior of strain‐induced crystallization and molecular orientation during extension and retraction. Our results confirmed the occurence of strain‐induced networks in the synthetic rubbers due to the inhomogeneity of the crosslink distribution. The strain‐induced networks containing microfibrillar crystals and oriented amorphous tie chains were responsible for the ultimate mechanical properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 956–964, 2004 相似文献
12.
A Geometric Characterization of Automatic Monoids 总被引:1,自引:0,他引:1
13.
Benjamin S. Hsiao Rong-Ming Ho Stephen Z. D. Cheng 《Journal of Polymer Science.Polymer Physics》1995,33(17):2439-2447
Unique crystallization and melting behavior in poly(aryl ether ketone ketone) containing alternated terephthalic and isophthalic moieties were studied by time-resolved synchrotron x-ray methods. Recently, this material has been shown to exhibit three polymorphs (forms I, II, and III). In this work, we further investigated their distinctive thermal properties and found that form I is the dominating and the most thermally stable phase while form II is favored by fast nucleation conditions and is the least stable phase. On the other hand, form III represents a minor intermediate phase that usually coexists with form I and can be transferred from form II and to form I. Structural and morphological changes in form I have been followed by simultaneous wide-angle x-ray diffraction (WAXD)/small-angle x-ray scattering (SAXS) measurements during cold- or melt-crystallization and subsequent melting. In all cases, a larger dimensional change was found in the crystallographic a-axis than the b-axis during heating and cooling. This may be due to the greater lateral stress variation with respect to temperature along the a direction of the primary lamellae which is induced by either the formation of secondary lamellae or the preferential chain-folding direction in poly(aryl ether ketone ketone)s. During the phase transitions of form II ← III in the cold-crystallized specimen and form III ← I in the melt-crystallized samples, lamellar variables (long period, lamellar thickness, and invariant) obtained from SAXS remain almost constant. This indicates that the density distribution in the long spacing is independent of the melting in form II or III. For melt-crystallization, the corresponding changes in unit-cell dimensions and lamellar morphology during the annealing-induced low endotherm are most consistent with the argument that these changes are due to the melting of thin lamellar population. © 1995 John Wiley & Sons, Inc. 相似文献
14.
15.
16.
17.
Sherif Yehia C. Mitros Sanjeev Kumar S. Jha Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1987,34(1-4):415-418
The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported. 相似文献
18.
19.
In this paper, three new direct Mutually Orthogonal Latin Squares (MOLS) constructions are presented for 7 MOLS(24), 7 MOLS(75) and 8 MOLS(36); then using recursive methods, several new constructions for 7 and 8 MOLS are obtained. These reduce the largest value for which 7 MOLS are unknown from 780 to 570, and the largest odd value for which 8 MOLS are unknown from 1935 to 419. © 2003 Wiley Periodicals, Inc. 相似文献
20.
Arnold Neumaier 《Journal of Global Optimization》2003,25(2):175-181
A family of multivariate rational functions is constructed. It has strong local minimizers with prescribed function values at prescribed positions. While there might be additional local minima, such minima cannot be global. A second family of multivariate rational functions is given, having prescribed global minimizers and prescribed interpolating data. 相似文献