全文获取类型
收费全文 | 27772篇 |
免费 | 869篇 |
国内免费 | 190篇 |
专业分类
化学 | 18214篇 |
晶体学 | 255篇 |
力学 | 926篇 |
综合类 | 1篇 |
数学 | 2347篇 |
物理学 | 6461篇 |
综合类 | 627篇 |
出版年
2023年 | 154篇 |
2022年 | 410篇 |
2021年 | 496篇 |
2020年 | 434篇 |
2019年 | 450篇 |
2018年 | 339篇 |
2017年 | 319篇 |
2016年 | 731篇 |
2015年 | 633篇 |
2014年 | 806篇 |
2013年 | 1494篇 |
2012年 | 1983篇 |
2011年 | 2183篇 |
2010年 | 1317篇 |
2009年 | 1155篇 |
2008年 | 1776篇 |
2007年 | 1691篇 |
2006年 | 1573篇 |
2005年 | 1478篇 |
2004年 | 1289篇 |
2003年 | 1030篇 |
2002年 | 1007篇 |
2001年 | 699篇 |
2000年 | 606篇 |
1999年 | 351篇 |
1998年 | 255篇 |
1997年 | 295篇 |
1996年 | 336篇 |
1995年 | 258篇 |
1994年 | 274篇 |
1993年 | 277篇 |
1992年 | 270篇 |
1991年 | 210篇 |
1990年 | 158篇 |
1989年 | 145篇 |
1988年 | 147篇 |
1987年 | 125篇 |
1986年 | 97篇 |
1985年 | 170篇 |
1984年 | 115篇 |
1983年 | 99篇 |
1982年 | 124篇 |
1981年 | 91篇 |
1980年 | 82篇 |
1978年 | 83篇 |
1977年 | 87篇 |
1976年 | 96篇 |
1975年 | 103篇 |
1974年 | 83篇 |
1973年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
31.
32.
J. W. Lee Y. Takase B. A. Newman J. I. Scheinbeim 《Journal of Polymer Science.Polymer Physics》1991,29(3):273-277
Cold-drawn Nylon-11 films, which were prepared by stretching the melt-quenched films to a draw ratio of 2.8: 1 at room temperature, were found to exhibit an electric displacement versus electric field hysteresis loop. The results confirmed that the Nylon-11 film exhibited ferroelectric behavior at or below room temperature. The coercive fields were 65, 98, 125, 160, and 215 MV/m at 20, 0, ?20, ?40, and ?60°C and the remanent polarization at ?20°C (where there was considerably less dc conduction) was 56 mC/m2. Switching of the polarization was almost completed within 20 ms. 相似文献
33.
Wai-Hung Ng S F Lee 《厦门大学学报(自然科学版)》2002,(Z1)
With a unique corporate culture based on ancient Ch in ese wisdom being implemented at workplace for more than 10 years, we have been e ncountering various issue of managing conflicts, in particular at organization r estructure period, although we perceive that conflict does not necessarily have dysfunctional effect on our group performance. However, conflicts between and am ong various levels of the organization hierarchy are inevitably creating certain impact on our organization cohesiveness, performa... 相似文献
34.
Jin Kyu Park Dong Hun Lee Bok Ju Song Jae Buem Oh Hwan Kyu Kim 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1326-1342
We have designed and synthesized novel perfluorinated polyimides with 3D controlled structure. At first, we successfully developed the new synthetic routes to diamines with pendant bulky perfluorinated aromatic units in a multi‐step synthetic procedure. Novel perfluorinated polyimides were prepared in a two‐step reaction in N‐methyl‐2‐pyrrolidinone (NMP) solution: The first step was for the synthesis of polyamic acids (PAAs) and the second reaction was for the imidization of PAA. The polymer yield was over 89% and the inherent viscosity of PAAs was in the range of 0.24–0.36 dL/g. The thin films were prepared by spin‐coating the PAA solution in NMP onto various substrates such as a Si wafer or a KBr pellet, dried at 80 °C and further cured at 230 °C. The resultant polyimides are thermally stable over 400 °C. The refractive index and birefringence of the resultant polyimides are 1.5858–1.6452 and 0.01–0.005, respectively. The refractive index of polyimide decreases with increasing the fluorine content. The copolymerization and the ether linkages into the backbone reduce the birefringence of polyimides. Surprisingly, the pendant ether linkage is not a crucial factor in reducing the polyimide birefringence. Their birefringence is comparatively very low, compared with that of previous polyimides. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1326–1342, 2006 相似文献
35.
36.
37.
38.
We construct functions Mα which are piecewise homogeneous polynomials on the (d+1)-dimensional torus Ud+1. These functions possess complete symmetry with respect to the independent variables. The symmetry and homogeneous relations
for these functions are exploited to obtain a recurrence relation and explicit representations. Furthermore, we show that
, where ω=e12x/k, 0≤jt≤k−1, are linearly independent. By restricting Mα to Ud, we obtain the complex analogue of polynomial box splines on a (d+1)-direction mesh on Ud, which is a multivariate analogue of B-splines on the circle studied by I.J. Schoenberg[8]. 相似文献
39.
40.
Lee SH 《Physical review D: Particles and fields》1989,40(7):2484-2486