全文获取类型
收费全文 | 25325篇 |
免费 | 4795篇 |
国内免费 | 7304篇 |
专业分类
化学 | 19702篇 |
晶体学 | 780篇 |
力学 | 1701篇 |
综合类 | 852篇 |
数学 | 3192篇 |
物理学 | 11197篇 |
出版年
2024年 | 82篇 |
2023年 | 361篇 |
2022年 | 957篇 |
2021年 | 1014篇 |
2020年 | 1014篇 |
2019年 | 995篇 |
2018年 | 874篇 |
2017年 | 1134篇 |
2016年 | 1083篇 |
2015年 | 1305篇 |
2014年 | 1620篇 |
2013年 | 2066篇 |
2012年 | 2196篇 |
2011年 | 2208篇 |
2010年 | 1938篇 |
2009年 | 2034篇 |
2008年 | 2320篇 |
2007年 | 2032篇 |
2006年 | 1894篇 |
2005年 | 1679篇 |
2004年 | 1346篇 |
2003年 | 981篇 |
2002年 | 987篇 |
2001年 | 861篇 |
2000年 | 898篇 |
1999年 | 658篇 |
1998年 | 398篇 |
1997年 | 302篇 |
1996年 | 259篇 |
1995年 | 235篇 |
1994年 | 216篇 |
1993年 | 219篇 |
1992年 | 183篇 |
1991年 | 140篇 |
1990年 | 139篇 |
1989年 | 158篇 |
1988年 | 115篇 |
1987年 | 90篇 |
1986年 | 71篇 |
1985年 | 53篇 |
1984年 | 54篇 |
1983年 | 42篇 |
1982年 | 38篇 |
1981年 | 34篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1978年 | 6篇 |
1974年 | 8篇 |
1965年 | 20篇 |
1964年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
In the ever fusion experiments in SWIP, pellet forming process was carried out through adjusting relative devices by staff member in site, which will make every pellet-forming process slight distinction and will result in pellet difference in shape, size and intensity. In the intervals of HL-2A discharges, staff member have to go site to accomplish the pellet-forming process, this wastes human power and increase the potential danger. So it is necessary to develop a remote control system to perform the pellet-forming process. The control system needs have the features of real-time, reliability and be easy to operate and maintain. 相似文献
13.
Comparing with the exact solutions of the model system of one and two particles coupled to an axial rotor, the quality of the semi classical tilted axis cranking approximation is investigated. Extensive comparisons of the energies and M1 and E2 transition probabilities are carried out for the lowest bands. Very good agreement is found, except near band crossings. Various recipes to take into account finite K within the frame of the usual principal axis cranking are included into the comparison. A set of rules is suggested that permits to construct the excited bands from the cranking configurations, avoiding spurious states. 相似文献
14.
15.
Nickel complexes 1–4 ligated with 2,9-disubstituted-1,10-phenanthroline were synthesized and characterized by FT-IR spectra and elemental analysis.
The molecular structure of complex 2 was confirmed by X-ray crystal diffraction analysis. Activated with methylaluminoxane (MAO), those complexes showed moderate
activities for ethylene oligomerization.
Published in Kinetika i Kataliz, 2007, Vol. 48, No. 5, pp. 710–714.
This article was submitted by the authors in English. 相似文献
16.
求解一类非单调线性互补问题的宽邻域内点方法及其计算复杂性 总被引:1,自引:0,他引:1
对于一类非单调线性互补问题给出了一种新的算法——宽邻域内点算法,并讨论了其计算复杂性。 相似文献
17.
基于CSCW的协同编著系统的设计 总被引:3,自引:0,他引:3
讨论了计算机支持的协同工作(CSCW)的主要技术,其中重点讨论了协同编著系统设计中的并发控制技术,指出了其与传统的并发控制技术的区别。根据CSCW的基本原理设计出了一个基于Browse/Server结构的协同编著系统的系统模型。该系统模型比传统的模型更加方便了用户之间通过Internet的浏览器进行协作。 相似文献
18.
Burn‐in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, we consider the problem of determining the optimal burn‐in time and optimal work size maximizing the long‐run average amount of work saved per time unit in the computer applications. Assuming that the underlying lifetime distribution of the computer has an initially decreasing or/and eventually increasing failure rate function, an upper bound for the optimal burn‐in time is derived for each fixed work size and a uniform (with respect to the burn‐in time) upper bound for the optimal work size is also obtained. Furthermore, it is shown that a non‐trivial lower bound for the optimal burn‐in time can be derived if the underlying lifetime distribution has a large initial failure rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
19.
20.
Jie Da Thieo E. Hogen‐Esch 《Journal of polymer science. Part A, Polymer chemistry》2004,42(2):360-373
The synthesis is reported of copolymers of N,N‐dimethylacrylamide (DMA) and methacrylates containing 2,2′‐dihydroperfluorodecanoyl (RF) groups separated from the methacrylate by long polyethylene glycol (PEG) tether groups (between 1000 and 14,000 Da). At concentrations of between 1 and 8 wt % the copolymers with macromonomer contents of 1 mol % or less give gels in organic solvents such as dioxane, THF, or methanol, as well as in water. Given the low molecular weights, this indicates very efficient association of very low numbers of RF groups. Association and gel formation is enormously enhanced in the presence of longer PEG tethers. This is consistent with smaller poly(N,N,‐dimethylacrylamide) (PDMA) intermolecular excluded volume effects that are mediated by the longer PEG tethers and possibly by the incompatibility of PEG and PDMA that may lead to the formation of PEG microdomains. This increases the local concentrations of the RF groups in the PEO domains that are not diluted by the PDMA chains, as would be the case in the absence of PEG tethers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 360–373, 2004 相似文献