全文获取类型
收费全文 | 8739篇 |
免费 | 1046篇 |
国内免费 | 379篇 |
专业分类
化学 | 2015篇 |
晶体学 | 99篇 |
力学 | 2818篇 |
综合类 | 105篇 |
数学 | 1959篇 |
物理学 | 3168篇 |
出版年
2024年 | 14篇 |
2023年 | 85篇 |
2022年 | 235篇 |
2021年 | 235篇 |
2020年 | 267篇 |
2019年 | 206篇 |
2018年 | 218篇 |
2017年 | 269篇 |
2016年 | 283篇 |
2015年 | 232篇 |
2014年 | 317篇 |
2013年 | 538篇 |
2012年 | 476篇 |
2011年 | 500篇 |
2010年 | 361篇 |
2009年 | 453篇 |
2008年 | 523篇 |
2007年 | 581篇 |
2006年 | 607篇 |
2005年 | 489篇 |
2004年 | 401篇 |
2003年 | 372篇 |
2002年 | 337篇 |
2001年 | 310篇 |
2000年 | 269篇 |
1999年 | 238篇 |
1998年 | 197篇 |
1997年 | 175篇 |
1996年 | 141篇 |
1995年 | 134篇 |
1994年 | 112篇 |
1993年 | 96篇 |
1992年 | 95篇 |
1991年 | 64篇 |
1990年 | 58篇 |
1989年 | 25篇 |
1988年 | 25篇 |
1987年 | 32篇 |
1986年 | 31篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1977年 | 8篇 |
1976年 | 16篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
对强流脉冲离子束(IPIB)辐照Ti靶的烧蚀效应进行了二维数值研究.得到了表面烧蚀物质随脉冲时间的变化关系.得出TEMP Ⅱ 型加速器产生的脉冲束流辐照靶材时引起的汽、液化均是从表面开始、并且汽化过程中表面物质被层层烧蚀的结论.同时,得到中心区的平均烧蚀速度为10m/s 数量级,它远小于产生的烧蚀等离子体的喷发速度.得到脉冲期间靶材内部不同位置烧蚀斑痕形状的时间演化过程,以及束流中含有的离子种类分额不同时IPIB辐照过程产生的不同效果.
关键词:
强流脉冲离子束
靶
烧蚀过程
二维数值模拟 相似文献
992.
提出了一种新的用于浓度场测量的差分吸收光谱CT技术。利用差分吸收原理进行浓度场多方位积分测量,采用少数投影最大熵重建算法进行层析图像重建。数值模拟结果表明,在0°~180°视场范围内,在4个不同的投影视角方向获取投影数据的条件下,能有效地重建出待测场分布。该技术具有较高的重建精度和良好的抗噪声性能。 相似文献
993.
994.
HeSuxiang HanHua 《高校应用数学学报(英文版)》2005,20(2):243-251
The dual algorithm for minimax problems is further studied in this paper. The resulting theoretical analysis shows that the condition number of the corresponding Hessian of the smooth modified Lagrange function with changing parameter in the dual algorithm is proportional to the reciprocal of the parameter,which is very important for the efficiency of the dual algorithm. At last ,the numerical experiments are reported to validate the analysis results. 相似文献
995.
V. A. Mamedov I. Z. Nurkhametova S. K. Kotovskaya A. T. Gubaidullin Ya. A. Levin I. A. Litvinov V. N. Charushin 《Russian Chemical Bulletin》2004,53(11):2568-2576
A procedure was developed for the synthesis of thiazolo[3,4-a]quinoxaline derivatives based on a new strategy for construction of the pyrazine ring. The key step of the process involves the reaction of 4-hydroxy-3,5-diphenyl-2-phenyliminothiazolidines with o-phenylenediamines.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2462–2470, November, 2004. 相似文献
996.
Three-dimensional direct simulations and structure of expanding turbulent methane flames 总被引:1,自引:0,他引:1
D. Thvenin 《Proceedings of the Combustion Institute》2005,30(1):629-637
Direct numerical simulations (DNS) are ideally suited to investigate in detail turbulent reacting flows in simple geometries. For an increasing number of applications, detailed models must be employed to describe the chemical processes with sufficient accuracy. Despite the huge cost of such simulations, recent progress has allowed the direct numerical simulation of turbulent premixed flames while employing complete reaction schemes. We briefly describe our own developments in this field and use the resulting DNS code to investigate more extensively the structure of premixed methane flames expanding in a three-dimensional turbulent velocity field, initially homogeneous and isotropic. This situation typifies, for example, the initial flame development after spark ignition in a gas turbine or an internal combustion engine. First investigation steps have been carried out at low turbulence levels on this same configuration in the past Symposium, and we build on top of these former results. Here, a considerably higher Reynolds number is considered, the simulation has been repeated twice in to limit the possibility of spurious, very specific results, and several complementary post-processing steps are carried out. Characteristic features concerning the observed combustion regime are presented. We then investigate in a quantitative manner the evolution of flame surface area, global stretch-rate, flame front curvature, flame thickness, and correlation between thickness and curvature. The possibility of obtaining reliable information on flame front curvature from two-dimensional slices is checked by comparison with the exact procedure. 相似文献
997.
Summary Mixed ligand nickel(II) complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligands.
The magnetic susceptibility data, the IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms
bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds in the crystal state were observed. All complexes
are sensitive for moisture. The bis complex proved to be the more stable complex. 相似文献
998.
SERS技术研究电化学中的共吸附顾仁敖(苏州大学化学系苏州215006)SERSStudiesonElectrochemicalCoadsorptionGuRenao(DepartmentChemistry,SuzhouUniversitySuzho... 相似文献
999.
排烟增湿脱硫活化反应器内液滴──脱硫剂颗粒碰撞的数值模拟 总被引:5,自引:0,他引:5
排烟增湿脱硫活化反应器内液滴──脱硫剂颗粒碰撞的数值模拟唐庆,徐旭常(清华大学热能工程系北京100084)关键词液滴-颗粒碰撞,脱硫,数值模拟要有效的控制SOZ的污染,降低燃煤电厂排烟中SOZ的浓度显得尤为重要。在众多的烟气脱硫技术中,排烟增湿活化脱... 相似文献
1000.
K. Sasaki O. Takahashi N. Takada M. Nagatsu T. Tsukishima T. Okada S. Okajima Y. Tsunawaki S. Sudo K. N. Sato et al. 《International Journal of Infrared and Millimeter Waves》1995,16(12):2133-2146
Spectrally narrow, pulsed outputs consisting of almost a single mode have been obtained from an optically-pumped high-power (200kW) D2O laser by adopting the injection seeding method, where single-mode radiation (seed pulse) from a low-power, compact D2O laser has been injected into the main D2O laser. Spectrally narrow outputs with high power having spectral widths as narrow as 5 MHz have been obtained, when the seed pulses with frequency tuned to one longitudinal mode of the main D2O laser have been injected at a time sufficiently before the lasing of the main laser took place. The experimental results have been compared with those of numerical simulation modified to include the injection field with varying injection times. 相似文献