全文获取类型
收费全文 | 6014篇 |
免费 | 1345篇 |
国内免费 | 781篇 |
专业分类
化学 | 1799篇 |
晶体学 | 46篇 |
力学 | 393篇 |
综合类 | 147篇 |
数学 | 2413篇 |
物理学 | 3342篇 |
出版年
2024年 | 22篇 |
2023年 | 77篇 |
2022年 | 136篇 |
2021年 | 132篇 |
2020年 | 94篇 |
2019年 | 77篇 |
2018年 | 57篇 |
2017年 | 67篇 |
2016年 | 115篇 |
2015年 | 233篇 |
2014年 | 646篇 |
2013年 | 407篇 |
2012年 | 590篇 |
2011年 | 666篇 |
2010年 | 556篇 |
2009年 | 356篇 |
2008年 | 435篇 |
2007年 | 313篇 |
2006年 | 290篇 |
2005年 | 456篇 |
2004年 | 426篇 |
2003年 | 257篇 |
2002年 | 235篇 |
2001年 | 232篇 |
2000年 | 170篇 |
1999年 | 124篇 |
1998年 | 95篇 |
1997年 | 91篇 |
1996年 | 84篇 |
1995年 | 93篇 |
1994年 | 77篇 |
1993年 | 74篇 |
1992年 | 77篇 |
1991年 | 80篇 |
1990年 | 62篇 |
1989年 | 61篇 |
1988年 | 38篇 |
1987年 | 34篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 1篇 |
排序方式: 共有8140条查询结果,搜索用时 15 毫秒
51.
今天能有机会参加“第五届全国周培源大学生力学竞赛颁奖式”,并与大家见面,感到非常荣幸.首先,请允许我代表周培源基金会,向在这次竞赛当中获奖的同学表示热烈的祝贺!向在这次活动中付出辛勤劳动的老师、工作人员以及支持单位和各位领导表示衷心的感谢! 相似文献
52.
ZhongWeffang WuYongdong WuGuorong LiangYide 《Acta Mechanica Solida Sinica》2003,16(3):262-268
The acoustical scattering by a cracked elastic structure is studied. The mixed method of boundary element and fractal finite element is adopted to solve the cracked structure-acoustic coupling problem. The fractal two-level finite element method is employed for the cracked structure, which can reduce the degree of freedoms (DOFs) greatly, and the boundary element method is used for the exterior acoustic field which can automatically satisfy Sommerfeld‘s radiation condition. Numerical examples show that the resonance frequency is lower with the crack‘s depth increase, and that the effect on the acoustical field by the crack is particularly pronounced in the vicinity of the crack tip. This mixed method of boundary element and finite element is effective in solving the scattering problem by a cracked structure. 相似文献
53.
Based on the fluid-structure coupling theory, a localized variational principle for analyzing the sound radiation from elastic
structure submerged in water due to harmonic excitations is presented. It will be a powerful tool to formulate various numerical
methods for steady response of structural-acoustic systems. By means of this variational principle a hybrid element method,
in which an analytical solution valid in most of the surrounding water is incorporated with finite elements distributed in
the structure and its neighboring water, is devised. Computational examples are then given to demonstrate its high accuracy
and time saving.
The project supported by the National Natural Science Foundation of China (10172038) and the Doctoral Program Foundation of
Institution of Higher Education of China (20040487013). The English text was polished by Yunming Chen. 相似文献
54.
力学学科“九五”期间重点项目情况介绍孟庆国靳征谟国家自然科学基金委员会数理科学部,北京100083国家自然科学基金委员会受理和资助面上、重点和重大三个层次的基金项目.面上项目以一年为一个单元,依据所提交的申请书,经过专家同行评议,最后由学科评审组会议... 相似文献
55.
56.
57.
SPATIAL AND SEASONAL DISTRIBUTIONS OF ATMOSPHERIC CARBONACEOUS AEROSOLS IN PEARL RIVER DELTA REGION, CHINA 总被引:11,自引:0,他引:11
Concentrations and spatial distributions of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were measured at 8 sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of Pearl River Delta Region (PRDR), China during 2001 winter period and 2002 summer period. PM2.5 (particie diameter smaller than 2.5 um) and PM10 (particie diameter smaller than 10 um) samples were collected on pre-fired quartz filters with mini-volume samplers and analyzed using thermal optical reflectance (TOR) method. The average PM2.5and PM10 Ievel were 60.1 and 93.1 μg·m-3, respectively, with PM2.5 constituting 65.3% of the PM10 mass. The average OC and EC concentrations in PM2.5 were 12.0 and 5.1 μg·m-3, respectively, while those in PM10 were 16.0 and 6.5 μg·m-3, respectively. The carbo-naceous aerosol accounted for 37.2% of the PM2.5 and 32.8% of the PM10. The highest concentrations of OC and EC were observed at Guangzhou city in both vvinter and summer seasons. The average OC/EC ratios were 2. 相似文献
58.
INFLUENCE OF ASIAN DUSTS ON THE PHYSICOCHEMICAL PROPERTIES OF ATMOSPHERIC AEROSOLS IN TAIWAN DISTRICT USING THE PENGHU ISLANDS AS AN EXAMPLE 总被引:1,自引:0,他引:1
Chung-Shin Yuan* Cheng-Chung Sau Ming-Chung Chen Institute of Environmental Engineering Sun Yat-sen University Kaohsiung China 《中国颗粒学报》2004,2(4):144-152
1. Introduction In the early months of each year, Asian dusts transport frequently from Northwest China and Mongolia to the Pa-cific-Rim countries (Kagawa et al., 2001; Uno et al., 2002). It causes significant environmental effects such as ambient air quality deterioration, atmospheric visibility impairment, radiation energy reduction, mineral deposition, and acid rain neutralization (Terada et al., 2002; Zhang & An, 1999). During Asian dust periods, significant increases of atmos-pheric … 相似文献
59.
60.
《中国惯性技术学报》2005,13(5):57-57
《中国惯性技术学报》第四届编委会第三次工作会议于2005年9月7~9日在乌鲁木齐市召开。编委会委员及编辑部成员共16人参加了会议。 相似文献