全文获取类型
收费全文 | 127381篇 |
免费 | 1631篇 |
国内免费 | 461篇 |
专业分类
化学 | 70782篇 |
晶体学 | 2041篇 |
力学 | 4972篇 |
综合类 | 5篇 |
数学 | 12316篇 |
物理学 | 39357篇 |
出版年
2016年 | 1337篇 |
2015年 | 1072篇 |
2014年 | 1401篇 |
2013年 | 4938篇 |
2012年 | 3575篇 |
2011年 | 4590篇 |
2010年 | 2838篇 |
2009年 | 2644篇 |
2008年 | 4089篇 |
2007年 | 4154篇 |
2006年 | 4234篇 |
2005年 | 4158篇 |
2004年 | 3592篇 |
2003年 | 3272篇 |
2002年 | 3169篇 |
2001年 | 3594篇 |
2000年 | 2697篇 |
1999年 | 2210篇 |
1998年 | 1903篇 |
1997年 | 1901篇 |
1996年 | 1824篇 |
1995年 | 1791篇 |
1994年 | 1556篇 |
1993年 | 1545篇 |
1992年 | 1769篇 |
1991年 | 1759篇 |
1990年 | 1691篇 |
1989年 | 1692篇 |
1988年 | 1687篇 |
1987年 | 1686篇 |
1986年 | 1598篇 |
1985年 | 2148篇 |
1984年 | 2274篇 |
1983年 | 1892篇 |
1982年 | 2222篇 |
1981年 | 2029篇 |
1980年 | 2079篇 |
1979年 | 2064篇 |
1978年 | 2189篇 |
1977年 | 2092篇 |
1976年 | 2118篇 |
1975年 | 2054篇 |
1974年 | 1897篇 |
1973年 | 2102篇 |
1972年 | 1282篇 |
1971年 | 975篇 |
1970年 | 912篇 |
1969年 | 923篇 |
1968年 | 1050篇 |
1967年 | 1101篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
A. Sanusi M. Z. A. Yahya S. Navaratnam W. J. Basirun Y. Alias N. S. Mohamed A. K. Arof 《Ionics》2003,9(3-4):253-257
In this study, lead sulphide (PbS) was prepared by the chemical bath deposition technique. The sample was characterized by
X-ray diffraction (XRD), Energy Dispersive Analysis of X-rays (EDAX) and cyclic voltammetry. EDAX spectrum shows peaks attributable
to lead and sulphur. The EDAX analysis also shows that the prepared sample is stoichiometric. Cyclic voltammetry experiments
were recorded at 100 mV·s−1 and 400 mV·s−1 scan rates. Results show that the rate controlling electrochemical reaction is electron transfer. The presence of redox waves
shows that the lithium intercalation and deintercalation can occur as a result of lattice expansion in PbS. There were no
differences in the PbS XRD data before and after the cyclic voltammetry experiments indicating that the PbS structure is not
modified upon lithium ion intercalation and deintercalation in PbS. The discharge characteristics for 35 cycles of the cell
using the LiCoO2/PbS couple is presented indicating the possible development of such materials as anode in lithium ion cells. 相似文献
132.
133.
Ohne Zusammenfassung 相似文献
134.
David S. McGuinness Edward L. Marshall Vernon C. Gibson Jonathan W. Steed 《Journal of polymer science. Part A, Polymer chemistry》2003,41(23):3798-3803
Hetero‐bimetallic Fe(II) alkoxide/aryloxides were evaluated as initiators for the ring‐opening polymerization of rac‐lactide. [(THF)NaFe(OtBu)3]2 ( 1 ) and [(THF)4Na2Fe(2,6‐diisopropylphenolate)4] ( 2 ) (THF = tetrahydrofuran) both polymerized lactide efficiently at room temperature, with complex 1 affording better control over the molecular weight parameters of the resultant polymer. At conversions below 70%, a linear increase in molecular weight with conversion was observed, indicative of a well‐controlled polymerization process. Complex 2 is the first example of a dianionic Fe(II) alkoxide and has been structurally characterized to reveal a distorted square planar FeO4 array in which both Na counterions bridge two aryloxide ligands and are further complexed by two THF ligands. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3798–3803, 2003 相似文献
135.
Pascher W. Den Besten J. H. Caprioli D. Leijtens X. Smit M. van Dijk R. 《Optical and Quantum Electronics》2003,35(4-5):453-464
Based on a rigorous vectorial analysis, a fast travelling-wave Mach–Zehnder modulator is modelled and designed. The cross-section of the semiconductor layer stack and the lossy electrodes are carefully modelled using the method of lines in order to investigate propagation characteristics, velocity and losses. This yields an accurate microwave and optical field distribution to explain the behaviour of the component. In order to enhance the modulation efficiency, design curves are derived and the cross-sectional dimensions for minimum microwave loss are determined. The loss of the optimized modulator agrees very well with small-signal measurements up to 40 GHz and HFSS simulations. The layerstack of the fabricated device is suitable for integration with InP multi-wavelength lasers. 相似文献
136.
137.
138.
139.
140.
G. Jander und W. Brösse 《Fresenius' Journal of Analytical Chemistry》1929,77(3-4):147-148
Ohne Zusammenfassung 相似文献