全文获取类型
收费全文 | 1957篇 |
免费 | 47篇 |
国内免费 | 13篇 |
专业分类
化学 | 1321篇 |
晶体学 | 12篇 |
力学 | 47篇 |
数学 | 348篇 |
物理学 | 289篇 |
出版年
2022年 | 23篇 |
2021年 | 22篇 |
2020年 | 31篇 |
2019年 | 34篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 35篇 |
2015年 | 31篇 |
2014年 | 50篇 |
2013年 | 91篇 |
2012年 | 105篇 |
2011年 | 142篇 |
2010年 | 63篇 |
2009年 | 67篇 |
2008年 | 105篇 |
2007年 | 134篇 |
2006年 | 119篇 |
2005年 | 93篇 |
2004年 | 95篇 |
2003年 | 87篇 |
2002年 | 79篇 |
2001年 | 24篇 |
2000年 | 38篇 |
1999年 | 23篇 |
1998年 | 20篇 |
1997年 | 24篇 |
1996年 | 21篇 |
1995年 | 41篇 |
1994年 | 30篇 |
1993年 | 17篇 |
1992年 | 29篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 29篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1970年 | 6篇 |
排序方式: 共有2017条查询结果,搜索用时 15 毫秒
1.
2.
3.
E.Ann Hallinan Clifford R. DornWilliam M. Moore Gina M. JeromePamela T. Manning Barnett S. Pitzele 《Tetrahedron letters》2003,44(39):7345-7347
Described is a method of introducing trifluoroalkyl groups at C-6 of lysine. This chemistry has the potential to introduce a variety of functionality at C-6 of lysine. 相似文献
4.
Vishal Sipani Ann Kirsch Alec B. Scranton 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):4409-4416
The effective propagation rate constant (kp; averaged over all the propagating active centers) was characterized for solvent‐free cationic photopolymerizations of phenyl glycidyl ether over the entire range of conversions, including the high conversion regime in which mass transfer limitations become important. The profile for the kp as a function of conversion was found to exhibit a constant plateau value at low to intermediate conversions, followed by a monotonic increase above a threshold value of conversion. To explain this trend, it is proposed that at high conversion the diffusional mobility of the photoinitiator counterion is reduced whereas the mobility of the cationic active center remains high because of reactive diffusion. Therefore, with increasing conversion, the average distance between the active centers and counterions may increase, resulting in an increase in the propagation rate constant. The profiles for the kp values were investigated as a function of the temperature, photoinitiator anion, and photoinitiator concentration. As the photoinitiator concentration was increased, the plateau value of the effective propagation rate constant decreased whereas the threshold conversion increased. All of the experimental trends are consistent with the proposed increase in ion separation at high conversions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4409–4416, 2004 相似文献
5.
6.
7.
A Network Simulation of High-congestion Road-traffic Flows in Cities with Marine Container Terminals
James A. Pope Terry R. Rakes Loren Paul Rees Ingrid W. M. Crouch 《The Journal of the Operational Research Society》1995,46(9):1090-1101
Port cities where marine cargo terminals are located are generally near urban areas characterized by high-congestion road traffic. Changes in cargo traffic volumes into a marine terminal, or in the surrounding traffic arteries, which carry this traffic, can significantly affect the terminal's operations. Conversely, activity at the terminal can have an impact on the traffic levels and congestion for a considerable distance from the terminal. This paper demonstrates a methodology useful for studying the impact of road traffic flows on marine container terminals located in highly congested areas. This model was developed at the request of the Virginia Center for World Trade and was used to answer three planning questions in the port of Hampton Roads, Virginia, USA-what would be the impact of: opening a new section of interstate highway, a projected doubling of container traffic at one terminal, and a daily unit train in the vicinity of another terminal. The problem was made more challenging by limited data-collection funds. None the less, the model was deemed valid by a panel of traffic experts and officials from several major state and private agencies involved in marine traffic management. The model results were subsequently a factor in two major decisions related to terminal management. 相似文献
8.
9.
10.