全文获取类型
收费全文 | 4900篇 |
免费 | 664篇 |
国内免费 | 665篇 |
专业分类
化学 | 2038篇 |
晶体学 | 43篇 |
力学 | 573篇 |
综合类 | 69篇 |
数学 | 1115篇 |
物理学 | 2391篇 |
出版年
2024年 | 7篇 |
2023年 | 88篇 |
2022年 | 142篇 |
2021年 | 136篇 |
2020年 | 127篇 |
2019年 | 103篇 |
2018年 | 112篇 |
2017年 | 198篇 |
2016年 | 205篇 |
2015年 | 166篇 |
2014年 | 247篇 |
2013年 | 476篇 |
2012年 | 308篇 |
2011年 | 369篇 |
2010年 | 306篇 |
2009年 | 336篇 |
2008年 | 331篇 |
2007年 | 332篇 |
2006年 | 276篇 |
2005年 | 240篇 |
2004年 | 244篇 |
2003年 | 204篇 |
2002年 | 153篇 |
2001年 | 136篇 |
2000年 | 92篇 |
1999年 | 119篇 |
1998年 | 93篇 |
1997年 | 114篇 |
1996年 | 89篇 |
1995年 | 61篇 |
1994年 | 66篇 |
1993年 | 56篇 |
1992年 | 47篇 |
1991年 | 41篇 |
1990年 | 28篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有6229条查询结果,搜索用时 15 毫秒
1.
2.
Addition of functionalized zinc-copper reagents to the title complexes proceeds in a highly diastereoselective fashion to afford dienol complexes. The relative configurations of adducts 3d were determined by single X-ray diffraction analysis. 相似文献
3.
We consider Markov processes built from pasting together pieces of strong Markov processes which are killed at a position
dependent rate and connected via a transition kernel. We give necessary and sufficient conditions for local absolute continuity
of probability laws for such processes on a suitable path space and derive an explicit formula for the corresponding likelihood
ratio process. The main tool is the consideration of the process between successive jumps – what we call ‘elementary experiments’
– and criteria for absolute continuity of laws of the process there. We apply our results to systems of branching diffusions
with interactions and immigrations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
一种新的WDM光网中的共享链路保护策略 总被引:2,自引:2,他引:0
研究了WDM光网中的链路保护问题.提出了一种新的共享链路保护策略--基于SRLG的共享链路保护策略(SRLG-SLP).SRLG(共享风险链路组)定义了对一条工作光通道分配保护资源时的资源可用性的约束.它规定任意两条有着同样故障风险或者说处于同一个SRLG的工作光通道不能利用同样的保护资源.另外,还提出了一种更加符合实际的单链路故障模型,其中链路故障间隔时间和链路故障保持时间被考虑作为两个独立的变量.基于该链路故障模型,通过大量的仿真试验,比较了专用链路保护(DLP)、共享链路保护(SLP)和提出的SRLG-SLP保护策略的资源利用率、保护效率以及业务中断率.结果显示,我们提出的SRLG-SLP在保护效率和业务中断率方面的保护性能远好于DLP和SLP,但会牺牲一些资源利用率. 相似文献
5.
6.
Most of the methods used in the ARCH literature for selecting the appropriate model are based on evaluating the ability of the models to describe the data. An alternative model selection approach is examined based on the evaluation of the predictability of the models in terms of standardized prediction errors. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
7.
Milan V. Patel Samir A. Patel Arabinda Ray Rajni M. Patel 《Journal of polymer science. Part A, Polymer chemistry》2004,42(20):5227-5234
Copolymers of monomers 2,4‐dichlorophenyl methacrylate (2,4‐DMA) and methyl methacrylate (MMA) were synthesized with different monomer feed ratios using toluene as a solvent and 2,2′‐azobisisobutyronitrile (AIBN) as an initiator at 70 °C. The copolymers were characterized by IR‐spectroscopy, and copolymer composition was determined with UV‐spectroscopy. The linearization method of Fineman–Ross was employed to obtain the monomer reactivity ratios. The molecular weights and polydispersity indexes were determined by gel permeation chromatography (GPC). Thermogravimetric analyses of polymers were carried out in nitrogen atmosphere. The homo‐ and copolymers were tested for their antimicrobial properties against selected microorganisms. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5227–5234, 2004 相似文献
8.
Two groups of 10 speech-language pathology graduate students were each given 7 weeks of singing lessons to determine whether voice lessons could have an effect on their clinical and perceptual skills. Pre-, mid-, and posttests to measure various skills were designed and implemented. With use of paired sample statistical testing, statistically significant results were obtained. In addition, the subjective responses of the students show that the lessons were effective in improving pitch perception, breath control, and legato production or easy onset. This study supports efforts to integrate curricula in vocal performance and speech-language pathology. 相似文献
9.
10.
ITERʵ�����ƻ����� 总被引:28,自引:12,他引:16
冯开明 《核聚变与等离子体物理》2006,26(3):161-169
简要介绍了ITER计划的发展历程;综述了ITER实验包层模块计划(ITER-TBM)的历史、主要技术路线和最新的设计与研发进展;概述了与实验包层计划相关的DEMO聚变堆的定义与发展策略。最后,介绍了国内开展的基于固体增殖剂概念的ITER实验包层的初步设计概况,对TBM的研发计划提出了建议。 相似文献