全文获取类型
收费全文 | 1977篇 |
免费 | 310篇 |
国内免费 | 155篇 |
专业分类
化学 | 1343篇 |
晶体学 | 25篇 |
力学 | 144篇 |
综合类 | 12篇 |
数学 | 174篇 |
物理学 | 744篇 |
出版年
2024年 | 6篇 |
2023年 | 34篇 |
2022年 | 75篇 |
2021年 | 84篇 |
2020年 | 71篇 |
2019年 | 59篇 |
2018年 | 74篇 |
2017年 | 67篇 |
2016年 | 96篇 |
2015年 | 114篇 |
2014年 | 121篇 |
2013年 | 157篇 |
2012年 | 186篇 |
2011年 | 197篇 |
2010年 | 113篇 |
2009年 | 124篇 |
2008年 | 125篇 |
2007年 | 121篇 |
2006年 | 101篇 |
2005年 | 75篇 |
2004年 | 40篇 |
2003年 | 33篇 |
2002年 | 35篇 |
2001年 | 31篇 |
2000年 | 36篇 |
1999年 | 31篇 |
1998年 | 24篇 |
1997年 | 24篇 |
1996年 | 32篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1991年 | 15篇 |
1990年 | 24篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1981年 | 2篇 |
1976年 | 2篇 |
1957年 | 1篇 |
1942年 | 1篇 |
1941年 | 1篇 |
1936年 | 4篇 |
1930年 | 2篇 |
1929年 | 1篇 |
1927年 | 1篇 |
1923年 | 1篇 |
排序方式: 共有2442条查询结果,搜索用时 15 毫秒
991.
992.
激光准直自动化监测大坝变形方法的研究 总被引:2,自引:0,他引:2
本文介绍了一种用激光准直法对大坝变形进行监测的方法,阐述了其中的关键光学元件-菲涅耳波带片的应用,并采用CCD技术求取象点中心位置的精确处理方法,从而通过象点位置变化来跟踪大坝的变形.在分析其工作原理的基础上建立了一套测量装置,通过原理实验,论证了该方法的可行性与精确性. 相似文献
993.
Shi Xunqing John HL Pang Yang Qianjin Wang Zhiping Nie Jingxu 《Acta Mechanica Sinica》2002,18(4):356-367
In the present study, a facility, i.e., a mechanical deflection system (MDS), was established and applied to assess the long-term
reliability of the solder joints in plastic ball grid array (BGA) assembly. It was found that the MDS not only quickly assesses
the long-term reliability of solder joints within days, but can also mimic similar failure mechanisms in accelerated thermal
cycling (ATC) tests. Based on the MDS and ATC reliability experiments, the acceleration factors (AF) were obtained for different
reliability testing conditions. Furthermore, by using the creep constitutive relation and fatigue life model developed in
part I, a numerical approach was established for the purpose of virtual life prediction of solder joints. The simulation results
were found to be in good agreement with the test results from the MDS. As a result, a new reliability assessment methodology
was established as an alternative to ATC for the evaluation of long-term reliability of plastic BGA assembly.
The project supported by the National Natural Science Foundation of China (59705008) 相似文献
994.
995.
996.
Antitrypsin in human serum was determined by using both the SAW-impedance sensor system and spectrophotometry, indicating that the mean value for women was significantly higher than the mean value for men; the value for acute pancreasis patients is about 2-folds of the normal values, and there is no significant difference between the acute pancreasis patients and the pancreatic cancer patients. 相似文献
997.
998.
Qi Wei Li Liu Zuo-Ren Nie Hui-Qiao Chen Jing-Xia Zou 《Journal of Sol-Gel Science and Technology》2007,44(2):105-110
Fluorocarbon groups were used to modify the pore channels of ethane-bridged periodic mesoporous organosilica by the co-condensation
of 1,2-Bis(triethoxysilyl)ethane (BTESE) and trifluoropropyltrimethoxysilane (TFPTMS) in the presence of Poly(ethylene glycol)-B-Poly(propylene
glycol)-B-Poly(ethylene glycol) (P123) surfactants under acidic conditions. The functionalized materials were investigated
in detail by means of XRD, TEM, FT-IR, solid-state NMR, and N2 adsorption. The effect of fluorocarbon groups concentration on the mesoscopic order and pore structure of the functionalized
materials was also studied. The results show that bridging groups in the framework do not cleave and fluorocarbon groups are
attached covalently to the pore wall of periodic mesoporous organosilica after functionalization. The samples functionalized
with 20% TFPTMS remain desired mesoporous architecture, with a narrow pore size distribution centered at 4.1 nm, a large surface
of 834 m2/g and a pore volume of 0.91 cm3g−1, without pronounced change compared to the pure periodic mesoporous organosilica. Unfortunately the functionalized materials
become structurally disordered with increasing amount of fluorocarbon groups. 相似文献
999.
1000.
Nie AiHua Xiao JunHai Wang LiLi Liao GuoChao Liu HongYing Ren Shen Li Song 《中国科学B辑(英文版)》2007,50(3):405-417
By choosing neuroimmunophilin FKBP12 as a therapeutical target, we have attempted to discover a new structural drug for treating
neurodegenerative disease. This drug should possess neurotrophic activity and not affect the immune system. Based on the crystal
structure of FKBP12, FK506 and Calcineurin complex, a series of small organic molecules were designed. These molecules were
to have the ability of binding to FKBP12 in a virtual screening. By using a solution parallel synthetic method, these compounds
were synthesized. The neuroprotective and neuroregenerative activities of these compounds were evaluated by binding assays,
PC12 cells survival and neurite outgrowth model, chick dorsal root ganglion cultures (DRG) and 6-OHDA lesioned mice sympathetic
nerve endings model. The evaluation results of these compounds showed that compound N308 has great promise as a candidate
for a neuroprotective and neuroregenerative agent.
Supported by the National Basic Research Program of China (Grant No. G1998051107) and Hi-tech Research and Development Program
of China (Grant No. 2002AA233051) 相似文献