全文获取类型
收费全文 | 194355篇 |
免费 | 1891篇 |
国内免费 | 2549篇 |
专业分类
化学 | 140281篇 |
晶体学 | 54篇 |
力学 | 1572篇 |
综合类 | 72篇 |
数学 | 2727篇 |
物理学 | 54089篇 |
出版年
2023年 | 184篇 |
2022年 | 201篇 |
2021年 | 178篇 |
2020年 | 159篇 |
2019年 | 132篇 |
2018年 | 200篇 |
2017年 | 123篇 |
2016年 | 269篇 |
2015年 | 231篇 |
2014年 | 452篇 |
2013年 | 359篇 |
2012年 | 17599篇 |
2011年 | 24674篇 |
2010年 | 4070篇 |
2009年 | 969篇 |
2008年 | 18296篇 |
2007年 | 18677篇 |
2006年 | 19217篇 |
2005年 | 18346篇 |
2004年 | 14187篇 |
2003年 | 10442篇 |
2002年 | 9105篇 |
2001年 | 5924篇 |
2000年 | 7263篇 |
1999年 | 2006篇 |
1998年 | 774篇 |
1997年 | 653篇 |
1996年 | 2875篇 |
1995年 | 1982篇 |
1994年 | 2596篇 |
1993年 | 3507篇 |
1992年 | 3079篇 |
1991年 | 1230篇 |
1990年 | 1212篇 |
1989年 | 1052篇 |
1988年 | 883篇 |
1987年 | 841篇 |
1986年 | 965篇 |
1985年 | 850篇 |
1984年 | 250篇 |
1983年 | 169篇 |
1982年 | 156篇 |
1981年 | 152篇 |
1979年 | 118篇 |
1975年 | 165篇 |
1958年 | 192篇 |
1957年 | 123篇 |
1956年 | 109篇 |
1955年 | 118篇 |
1948年 | 130篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
141.
A high efficiency and high peak power laser system with short-pulse and good beam quality has been demonstrated by using a master oscillator power amplifier with two-pass amplification configuration. The master oscillator, end-pumped with a fiber-coupled laser diode array, provides low power but excellent beam quality pulses, and the amplifier boosts the pulse energy by orders without significant beam quality degradation. Short pulses of 8.5 ns with energy up to 130 mJ and approximately diffraction limited beam quality have been demonstrated. 相似文献
142.
CHENG Chuanfu SONG Hongsheng LIU Chunxiang REN Xiaorong ZHANG Ningyu TENG Shuyun & XU Zhizhan . Shanghai Institute of Optics Fine Mechanics Chinese Academy of Sciences P. O. Box - Shanghai China . Department of Physics Shandong Normal University Jinan China . Shandong Institute of Architecture Engineering Jinan China 《中国科学G辑(英文版)》2004,47(3):365-380
Speckle fields are the random light wave distributions produced when the light fields are scattered from random surfaces or a random medium. They appear in many optical phenomena that are related to light propagations[1,2] and have found wide appli-cations in a variety of scientific and technical fields. The examples of the recent impor-tant applications of speckles include the analysis of the movement of the granules[3], the three-dimensional imaging for the microstructures of metal nanocryst… 相似文献
143.
采用基于相对论平均场的耦合常数解析延拓方法研究球形核的单粒子共振态.具体计算了Zr同位素链中巨晕核的核芯核122Zr阈值附近的中子共振态的能量、宽度和波函数,其结果同相应的散射相移法的结果一致. Using analytic continuation in the coupling constant (ACCC) method within the framework of the self-consistent relativistic mean field (RMF) theory, the energies, widths and wave functions for single-particle resonant states close to the continuum threshold are evaluated. Predictions are also compared with corresponding results obtained by the scattering phase shift method. 相似文献
144.
U. Goginava 《分析论及其应用》2007,23(3):255-265
In this paper we prove that iff ∈ C([-π,π]2) and the function f is bounded partial p-variation for some p ∈ [1, ∞), then the double trigonometric Fourier series of a function f is uniformly (C;-α,-β) summable (α β< 1/p,α,β> 0) in the sense of Pringsheim. If α β≥ 1/p, then there exists a continuous function f0 of bounded partial double trigonometric Fourier series of fo diverge over cubes. 相似文献
145.
C.M.Lin C.T. Chia Y.J. Shu Y.K. Tseng 《光散射学报》2005,17(3):216-218
Weperformedthehigh-pressureRaman measurementofthethreenanosizedZnOcrystals. Wefoundthesmallerthesize,thehigherthe pressuretoinducethephasetransitionfrom w櫣rzitetorock-saltstructure. High-pressureRamanmeasurementsof nona-shapedZnOcrystalswerepreformed.The… 相似文献
146.
LI Wangliang XING Jianmin XIONG Xiaochao SHAN Guobin & LIU Huizhou . Laboratory of Separation Science Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing China . Graduate School of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2005,(6)
More and more stringent regulations of gasoline and diesel oil were proposed with the awareness of environmental protection. Hydrodesulfurization (HDS) is a conventional method to remove sulfur compounds for industrial purpose. The main drawbacks of this … 相似文献
147.
This paper studies the problem of uniformly dissipative solutions of somefifth order non-linear differential equations by the use of frequency domaintechnique. We use the generalized theorem of Yacubovich on dissipativity toobtain some new sufficient conditions of the existence of solutions that aredissipative for (1.1) and (1.2). 相似文献
148.
ZHANG Zhi-Li WANG Hong-Tao WANG Xiao-Wei MA Xiao-Yan LIU Jun-Yi R.J. Griff B.T. Golding 《有机化学》2003,23(Z1):10-10
Cobalamin-dependent methionine synthase plays a crucial role in folate metabolism and such would appear to be an excellent target for rational antifolate drug design. However, to date, no anticancer agents directed at this enzyme are available, but the enzyme is efficiently and specifically inhibited by N2O and this has proven invaluable for evaluating the biochemical consequence of enzyme inhibition and for mechanistic studies. [1,2] 2,5-Diamino-4-oxo-6-(3-butenyl) pyrimidine, a key intermediate in synthetic inhibitors of methionine synthase, was first synthesized using γbutenyl-β-ketoester and guanidine carbonate (Scheme 1). [3] 相似文献
149.
BinayakS.Choudhury 《分析论及其应用》2003,19(2):99-107
In the present paper we introduce a random iteration scheme for three random operators defined on a closed and convex subset of a uniformly convex Banach space and prove its convergence to a common fixed point of three random operators. The result is also an extersion of a known theorem in the corresponding non-random case. 相似文献
150.
One of the Prussian blue analogs, molecular magnet Cu3^Ⅲ [Fe^Ⅲ (CN)6]2.11.6H2 O, was investigated by Moessbauer spectroscopy. It was found that transition temperature was around Tc = 18.5 K from paramagnetic phase to ferromagnetic phase. The β value of the critical exponent is around 0.338 at magnetic ordering temperature.Therefore, the ferromagnetic coupling interaction of Cu-Fe cyanide could be clearly explained by spin wave theory. 相似文献