全文获取类型
收费全文 | 41982篇 |
免费 | 10585篇 |
国内免费 | 2573篇 |
专业分类
化学 | 45692篇 |
晶体学 | 421篇 |
力学 | 896篇 |
综合类 | 77篇 |
数学 | 2981篇 |
物理学 | 5073篇 |
出版年
2024年 | 20篇 |
2023年 | 117篇 |
2022年 | 293篇 |
2021年 | 400篇 |
2020年 | 1473篇 |
2019年 | 2782篇 |
2018年 | 1230篇 |
2017年 | 875篇 |
2016年 | 3632篇 |
2015年 | 3802篇 |
2014年 | 3774篇 |
2013年 | 4477篇 |
2012年 | 3508篇 |
2011年 | 2746篇 |
2010年 | 3269篇 |
2009年 | 3227篇 |
2008年 | 2817篇 |
2007年 | 2127篇 |
2006年 | 1847篇 |
2005年 | 1943篇 |
2004年 | 1706篇 |
2003年 | 1603篇 |
2002年 | 2363篇 |
2001年 | 1671篇 |
2000年 | 1456篇 |
1999年 | 514篇 |
1998年 | 179篇 |
1997年 | 148篇 |
1996年 | 127篇 |
1995年 | 90篇 |
1994年 | 102篇 |
1993年 | 81篇 |
1992年 | 75篇 |
1991年 | 62篇 |
1990年 | 49篇 |
1989年 | 58篇 |
1988年 | 52篇 |
1987年 | 41篇 |
1986年 | 55篇 |
1985年 | 53篇 |
1984年 | 47篇 |
1983年 | 34篇 |
1982年 | 26篇 |
1981年 | 18篇 |
1980年 | 26篇 |
1979年 | 16篇 |
1977年 | 16篇 |
1976年 | 24篇 |
1975年 | 19篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Daria E. Lonsdale Geoffrey Johnston‐Hall Amanda Fawcett Craig A. Bell Carl N. Urbani Michael R. Whittaker Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3620-3625
In this work, we propose that retardation in vinyl acetate polymerization rate in the presence of toluene is due to degradative chain transfer. The transfer constant to toluene (Ctrs) determined using the Mayo method is equal to 3.8 × 10?3, which is remarkably similar to the value calculated from the rate data, assuming degradative chain transfer (2.7 × 10?3). Simulations, including chain‐length‐dependent termination, were carried out to compare our degradative chain transfer model with experimental results. The conversion–time profiles showed excellent agreement between experiment and simulation. Good agreement was found for the Mn data as a function of conversion. The experimental and simulation data strongly support the postulate that degradative chain transfer is the dominant kinetic mechanism. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3620–3625, 2007 相似文献
142.
J‐F. Masson Slaana Bundalo‐Perc Ana Delgado 《Journal of Polymer Science.Polymer Physics》2005,43(3):276-279
Differential scanning calorimetry (DSC) does not allow for easy determination of the glass‐transition temperature (Tg) of the polystyrene (PS) block in styrene–butadiene–styrene (SBS) block copolymers. Modulated DSC (MDSC), which deconvolutes the standard DSC signal into reversing and nonreversing signals, was used to determine the (Tg) of both the polybutadiene (PB) and PS blocks in SBS. The Tg of the PB block was sharp, at ?92 °C, but that for the PS blocks was extremely broad, from ?60 to 125 °C with a maximum at 68 °C because of blending with PB. PS blocks were found only to exist in a mixed PS–PB phase. This concurred with the results from dynamic mechanical analysis. Annealing did not allow for a segregation of the PS blocks into a pure phase, but allowed for the segregation of the mixed phase into two mixed phases, one that was PB‐rich and the other that was PS‐rich. It is concluded that three phases coexist in SBS: PB, PB‐rich, and PS‐rich phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 276–279, 2005 相似文献
143.
Kwang-Hua W. Chu 《International Journal of Theoretical Physics》2007,46(12):3230-3233
The modified Gross–Pitaevskii equation was derived and solved to obtain the 1D solution in the zero-energy limit. This stationary
solution could account for the dominated contributions due to the kinetic effect as well as the chemical potential in inhomogeneous
Bose gases. 相似文献
144.
145.
The new phenylpropanoid diglycoside ligusinenoside A ( 1 ), and the two new 8,4′‐oxyneolignan(‘8‐O‐4′‐neolignan’) diglycosides ligusinenosides B ( 2 ) and C ( 3 ), together with nine known compounds, were isolated from the rhizomes of Ligusticum sinensis Oliv. The structures of 1 – 3 were elucidated on the basis of spectroscopic analyses. 相似文献
146.
147.
148.
149.
150.
对Sn-C60薄膜进行紫外可见光吸收,X-射线衍射和扫描电镜的测定结果显示,薄膜样品紫外可见光吸收的两个短波段吸收峰比纯C60薄膜的吸收峰显著下降,说明Sn-C60薄膜的电子光吸收跃迁为间接跃迁,能带中有杂质能级的存在;样品的X射线衍射峰则对应于面心立方结构;扫描电镜结果显示薄膜为纳米级颗粒组成。 相似文献