全文获取类型
收费全文 | 16745篇 |
免费 | 1540篇 |
国内免费 | 783篇 |
专业分类
化学 | 11675篇 |
晶体学 | 152篇 |
力学 | 615篇 |
综合类 | 41篇 |
数学 | 1569篇 |
物理学 | 5016篇 |
出版年
2024年 | 34篇 |
2023年 | 193篇 |
2022年 | 339篇 |
2021年 | 395篇 |
2020年 | 425篇 |
2019年 | 387篇 |
2018年 | 355篇 |
2017年 | 314篇 |
2016年 | 598篇 |
2015年 | 581篇 |
2014年 | 710篇 |
2013年 | 1076篇 |
2012年 | 1253篇 |
2011年 | 1396篇 |
2010年 | 858篇 |
2009年 | 791篇 |
2008年 | 1062篇 |
2007年 | 931篇 |
2006年 | 915篇 |
2005年 | 831篇 |
2004年 | 704篇 |
2003年 | 570篇 |
2002年 | 557篇 |
2001年 | 365篇 |
2000年 | 349篇 |
1999年 | 314篇 |
1998年 | 233篇 |
1997年 | 209篇 |
1996年 | 258篇 |
1995年 | 200篇 |
1994年 | 209篇 |
1993年 | 184篇 |
1992年 | 162篇 |
1991年 | 129篇 |
1990年 | 130篇 |
1989年 | 129篇 |
1988年 | 87篇 |
1987年 | 78篇 |
1986年 | 69篇 |
1985年 | 88篇 |
1984年 | 53篇 |
1983年 | 46篇 |
1982年 | 47篇 |
1981年 | 43篇 |
1980年 | 36篇 |
1979年 | 41篇 |
1977年 | 28篇 |
1976年 | 31篇 |
1975年 | 23篇 |
1973年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Hee Seok Choi Young Han Kim Shun Myung Shin 《Journal of polymer science. Part A, Polymer chemistry》2006,44(8):2428-2439
An in‐line monitoring device using a quartz crystal resonator for thin film polymerization was proposed, and its performance has been evaluated by implementing in the UV polymerization of 2‐hydroxyethyl methacrylate with a photoinitiator of 1‐chloroanthraquinone. Because the variation of resonant resistance of the resonator is proportional to the square root of viscosity change that is closely related to the polymerization degree, the resistance can be used as a measure of the polymerization degree. The resistance measurements were compared with the outcome of instrumental analyses of polymerization degree using an FTIR spectrometer and a gel permeation chromatograph. The experimental results showed that the resistance measurements were consistent with the experimental outcome of the instrumental analyses, and this indicates the effectiveness of the proposed device. Owing to the simplicity and availability of the resonator system, its wide utilization in the monitoring of a variety of film polymerization processes, including photoresistor application, is expected. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2428–2439, 2006 相似文献
42.
Chae Kyu Kim Eun Seok Song Hyung Joo Kim Chiyoung Park Young Chul Kim Jai Kyeong Kim Jae Woong Yu Chulhee Kim 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):254-263
We have synthesized conjugated dendrimer with triazine peripheries, and their luminescence properties were investigated. The dendrimers consist of dendritic triazine wedges for electron transport, distyrylbenzene core as an emitting moiety, and t‐butyl peripheral groups for good processing properties. The dendrimers have LUMO values of about ?2.7 eV possibly because of the triazine moiety with high electron affinity. Photoluminescence study indicates that energy transfer occurs from the triazine wedges to the stilbene bridge, and finally to the core chromophore units due to a cascade decrease of bandgap from the peripheral wedge to core moiety. Therefore, the emission wavelength was determined by the structure of the core unit. The energy transfer efficiency of distyrylbenzene‐cored dendrimers was about 75 and 55% for Trz‐1GD‐DSB and Trz‐2GD‐DSB, respectively. A preliminary electroluminescence property also was investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 254–263, 2006 相似文献
43.
J.-S. Kang G. Kim S.S. Lee S. Choi S. Cho S.W. Han H.J. Shin B.I. Min 《Journal of magnetism and magnetic materials》2006
The spatial concentration distribution and local electronic structure of ferromagnetic Ge1−xTx (T=Cr, Mn, Fe) DMS single crystals have been investigated by using scanning photoelectron microscopy (SPEM), X-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES). It is found that doped T ions in Ge1−xTx crystals are chemically phase-separated, suggesting that the observed ferromagnetism arises from the phase-separated T-rich phases in Ge1−xTx. 相似文献
44.
M.C. Robinson D.J. Morris P.D. Hayenga J.H. Cho C.D. Richards R.F. Richards D.F. Bahr 《Applied Physics A: Materials Science & Processing》2006,85(2):135-140
Piezoelectric membranes have been fabricated that incorporate a gold bottom electrode with an adhesion layer of titanium–tungsten (10:90 wt. %). For solution-deposited acetic acid based lead zirconate titanate (HoAc-PZT) with a Zr:Ti ratio of 40:60, the film’s average piezoelectric coefficient, e31, is -5.31 C/m2, with a dielectric constant of 814 at 200 Hz, which is similar to values for platinum bottom electrodes. The PZT structure remains columnar on both types of bottom electrodes. Initial fabrication attempts resulted in cracking that initiated in the PZT layer of the structure. X-ray photoelectron spectroscopy was utilized to establish how processing affects diffusion throughout the composite membrane structure. Crack-free membranes were fabricated and tested. This paper discusses the performance properties and piezoelectric fatigue results for these membranes. PACS 77.84.-s; 77.84.Lf 相似文献
45.
For structural parameters with uncertainties, interval mathematics can, in the case where the probabilistic distribution density
of uncertain variables is unavailable, deal with the influence of uncertainties in structural parameters on the response of
structures. In order to evaluate the region containing natural frequencies of structures with interval parameters, the interval
parameter perturbation method is presented in this paper. The advantage of the present method is its computational efficiency
in evaluating the region containing natural frequencies. A numerical example is used to illustrate the efficiency of the method
proposed.
The project is supported by National Youth Natural Science Foundation of China and National Outstanding Youth Science Foundation
of China. 相似文献
46.
47.
48.
49.
Summary We propose and analyse a method of estimating the poles near the unit circleT of a functionG whose values are given at a grid of points onT: we give an algorithm for performing this estimation and prove a convergence theorem. The method is to identify the phase for an estimate by considering the peaks of the absolute value ofG onT, and then to estimate the modulus by seeking a bestL
2 fit toG over a small arc by a first order rational function. These pole estimates lead to the construction of a basis ofL
2 which is well suited to the numerical representation of the Hankel operator with symbolG and thereby to the numerical solution of the Nehari problem (computing the bestH
, analytic, approximation toG relative to theL
norm), as analysed in [HY]. We present the results of numerical tests of these algorithms.Partially supported by grants from the AFOSR and NSF 相似文献
50.