全文获取类型
收费全文 | 16219篇 |
免费 | 2846篇 |
国内免费 | 2297篇 |
专业分类
化学 | 11986篇 |
晶体学 | 182篇 |
力学 | 910篇 |
综合类 | 163篇 |
数学 | 2012篇 |
物理学 | 6109篇 |
出版年
2024年 | 45篇 |
2023年 | 340篇 |
2022年 | 626篇 |
2021年 | 644篇 |
2020年 | 712篇 |
2019年 | 775篇 |
2018年 | 615篇 |
2017年 | 575篇 |
2016年 | 821篇 |
2015年 | 870篇 |
2014年 | 1037篇 |
2013年 | 1240篇 |
2012年 | 1490篇 |
2011年 | 1508篇 |
2010年 | 1031篇 |
2009年 | 1052篇 |
2008年 | 1073篇 |
2007年 | 902篇 |
2006年 | 838篇 |
2005年 | 677篇 |
2004年 | 568篇 |
2003年 | 453篇 |
2002年 | 517篇 |
2001年 | 394篇 |
2000年 | 327篇 |
1999年 | 335篇 |
1998年 | 263篇 |
1997年 | 229篇 |
1996年 | 209篇 |
1995年 | 181篇 |
1994年 | 150篇 |
1993年 | 157篇 |
1992年 | 104篇 |
1991年 | 102篇 |
1990年 | 84篇 |
1989年 | 81篇 |
1988年 | 71篇 |
1987年 | 43篇 |
1986年 | 42篇 |
1985年 | 48篇 |
1984年 | 30篇 |
1983年 | 18篇 |
1982年 | 24篇 |
1981年 | 11篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1972年 | 4篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
91.
92.
Xiangdong Liu Hongwei Liu Kexu Yuan Huiping Du 《International Journal of Infrared and Millimeter Waves》1991,12(9):1023-1034
According to the angular-spectrum method, a radiation beam of an antenna horn in the Fresnal region is decomposed into the plane waves with the fast Fourier transform algorithm and the waves diffracted from a reflection grating are superposed as a diffracted beam. Compared with the reflected beam from the same size mirror, the radiation half width of the diffracted beam from a grating is narrower and its lateral shape is shift. These performances have been experimentally verified at Ka-band by: (1). The relative diffraction efficiencies in the first order with two triangular gratings which is put along propagating direction of a beam produced by a conical lens-horn. (2). H-plane lateral width with power—3dB lapsed of the focus beam from a grating and a mirror in a grating spectrometer for millimeter waves (25–100 GHz). 相似文献
93.
用Q-YAG激光的三次谐波(355nm)与调谐的Rh·6G染料激光在β-BaB2O4(BBO)晶体中和频,获得217.3~221.4nm连续调谐输出,和频输出的最大能量为250μJ,转换效率为11%.我们还讨论了获取最大和频输出能量的一些实验条件. 相似文献
94.
Chun Yuan Deng 《Journal of Mathematical Analysis and Applications》2007,335(1):64-71
In this note, the Drazin inverses of products and differences of orthogonal projections on a Hilbert space are established. 相似文献
95.
Crosslinking behaviors of acrylonitrile butadiene rubber (NBR)/poly (vinyl chloride) (PVC) alloy, filled with anhydrous copper sulfate (CuSO4) particles, were investigated for the first time by dynamic mechanical analysis (DMA) under hetero and isothermal modes, respectively. In the heterothermal testing, (NBR/PVC)/CuSO4 compound showed two marked increases in the storage modulus (E′), corresponding to coordination crosslinking of NBR-CuSO4 and self-crosslinking of NBR and PVC respectively. During the isothermal testing, a dramatic increase in E′ was found at the initial stage while that of original NBR/PVC alloy was not detected. The marked increase in E′ of (NBR/PVC)/CuSO4 compound was mainly due to the crosslinking induced by coordination between CN and Cu2+. The increasing extent of E′ increased with the rise of CuSO4 content, suggesting the formation of a greater number of crosslinks. Moreover, the activation energy (Ea) of crosslinking process was about 139 kJ/mol. In this work, fourier transform infrared spectrum (FT-IR) and equilibrium swelling method were also performed for the characterization of the compound. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 41–51, 2007 相似文献
96.
ZHANG Lin-bo LIU Xiao-hua ** JIANG Yuan GUO Ping SHA Li-jin LI Yu . Institute of Mycology . College of Biotechnology Jilin Agricultural University Changchun P.R. China 《高等学校化学研究》2006,(2)
Introduction Parkinson′sdisease(PD),alsocalledshaking palsy,isaneurodegenerativedisorderandfrequently occursinthepeopleabovetheageof65[1].PDisa relativelycommonneurodegenerativedisorder,which hasclinicalsymptomsincludingbradykinesia,rest tremor,rigidity,… 相似文献
97.
In this paper we investigate the acute triangulations of flat Mobius strips. We find out that we can always triangulate a
flat Mobius strip with at most nine acute triangles, and sometimes (but not always) that many triangles are really needed. 相似文献
98.
根据由赝势法得到的非理想玻色气体的自由能和状态方程,研究了相互作用对凝聚温度的影响.从热力学角度揭示了存在引力作用时定压热容量、等温压缩系数、定压膨胀系数的反常热力学特性.研究了引力作用下玻色气体系统的不稳定性,给出了不稳定性的温度判据和粒子数密度判据.
关键词:
相互作用
玻色气体
热力学性质
不稳定性判据 相似文献
99.
By dynamical simulations, we show a transforming process between neutral soliton (spin carrier) and charged soliton (charge carrier) in polymers via photo-excitation, taking a polaron as the transitional bridge. It is photoinduced transformation between spin carrier and charge carrier. In this way, we demonstrate an access for polymers to be applied to spintronics. 相似文献
100.
He Ping LIU Xuan Yuan ZHENG 《数学学报(英文版)》2006,22(2):425-430
We consider the commutators of the HSrmander multiplier with CMO-functions on the Heisenberg group. The result of compactness on L^P spaces is proved. 相似文献