全文获取类型
收费全文 | 2155篇 |
免费 | 52篇 |
国内免费 | 7篇 |
专业分类
化学 | 1267篇 |
晶体学 | 19篇 |
力学 | 114篇 |
数学 | 182篇 |
物理学 | 632篇 |
出版年
2023年 | 18篇 |
2022年 | 26篇 |
2021年 | 38篇 |
2020年 | 32篇 |
2019年 | 42篇 |
2018年 | 27篇 |
2017年 | 36篇 |
2016年 | 61篇 |
2015年 | 47篇 |
2014年 | 68篇 |
2013年 | 136篇 |
2012年 | 120篇 |
2011年 | 138篇 |
2010年 | 88篇 |
2009年 | 80篇 |
2008年 | 109篇 |
2007年 | 93篇 |
2006年 | 91篇 |
2005年 | 76篇 |
2004年 | 65篇 |
2003年 | 56篇 |
2002年 | 41篇 |
2001年 | 33篇 |
2000年 | 21篇 |
1999年 | 25篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 24篇 |
1995年 | 27篇 |
1994年 | 24篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 27篇 |
1990年 | 21篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 27篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 17篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1975年 | 19篇 |
1973年 | 11篇 |
1936年 | 13篇 |
排序方式: 共有2214条查询结果,搜索用时 15 毫秒
31.
The ultrasonic velocity (C) and density (ρ) have been measured at different frequencies (1MHz, 3MHz and 5 MHz) in the binary
mixtures of acetone with chlorobenzene over the entire range of mole fraction at temperature 303.16K. The data of C and ρ
have been used to evaluate the isentropic compressibility (β), intermolecular free length (Lf) and acoustic impedance (Z) and their excess values to elucidate the molecular association in the mixture. The variation
of these parameters with solute (acetone) indicates the nature of interaction present in the binary mixture. 相似文献
32.
We study the dynamics of the “Kolkata Paise Restaurant problem”. The problem is the following: In each period, N agents have to choose between N restaurants. Agents have a common ranking of the restaurants. Restaurants can only serve one customer. When more than one customer arrives at the same restaurant, one customer is chosen at random and is served; the others do not get the service. We first introduce the one-shot versions of the Kolkata Paise Restaurant problem which we call one-shot KPR games. We then study the dynamics of the Kolkata Paise Restaurant problem (which is a repeated game version of any given one shot KPR game) for large N. For statistical analysis, we explore the long time steady state behavior. In many such models with myopic agents we get under-utilization of resources, that is, we get a lower aggregate payoff compared to the social optimum. We study a number of myopic strategies, focusing on the average occupation fraction of restaurants. 相似文献
33.
Kuzmann E. Nath A. Chechersky V. Li S. Wei Y. Chen X. Li J. Homonnay Z. Gál M. Garg V. K. Klencsár Z. Vértes A. 《Hyperfine Interactions》2002,139(1-4):631-639
57Fe transmission Mössbauer spectroscopy and X-ray diffractometry were used to study - and -polymorphs of iron phthalocyanines (FePc) to get information about their oxygenation in connection with controlled pyrolysis of flat layered phthalocyanines initiated by radicals at relatively low temperatures, to form acicular carbide particles encaged in carbon. Mössbauer spectroscopy and XRD revealed that the oxygenation of both - and -polymorphs of FePc was successfully achieved. New Mössbauer spectral components (doublets) appeared upon the oxygenation in both and FePc. This can be attributed to iron microenvironments containing oxygen between the layers of iron phthalocyanines. 相似文献
34.
Jitendra Nath Roy 《Optik》2009,120(7):318-324
Interferometric devices for optical processing have been of great interest in recent years. Semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer (MZI) has already taken a significant role in the field of ultra-fast all-optical signal processing. Optical tree architecture (OTA) provides important contributions in optical interconnecting networks. In this communication, we have tried to exploit the advantages of both OTA and SOA-based MZI switches. We have proposed SOA-MZI-based tree architecture, a new and alternative scheme, for integrated all-optical logic and arithmetic operations. This architecture can enable one to perform all-optical processing of signals, including two input logic operations, half-adder, full-adder, full-subtractor, one-bit data comparator, etc. 相似文献
35.
Nilamoni Nath N. Suryaprakash 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,207(2):190-196
The increasing scientific and industrial interest towards metabonomics takes advantage from the high qualitative and quantitative information level of nuclear magnetic resonance (NMR) spectroscopy. However, several chemical and physical factors can affect the absolute and the relative position of an NMR signal and it is not always possible or desirable to eliminate these effects a priori. To remove misalignment of NMR signals a posteriori, several algorithms have been proposed in the literature. The icoshift program presented here is an open source and highly efficient program designed for solving signal alignment problems in metabonomic NMR data analysis. The icoshift algorithm is based on correlation shifting of spectral intervals and employs an FFT engine that aligns all spectra simultaneously. The algorithm is demonstrated to be faster than similar methods found in the literature making full-resolution alignment of large datasets feasible and thus avoiding down-sampling steps such as binning. The algorithm uses missing values as a filling alternative in order to avoid spectral artifacts at the segment boundaries. The algorithm is made open source and the Matlab code including documentation can be downloaded from www.models.life.ku.dk. 相似文献
36.
37.
38.
39.
Two-photon absorption(2PA) in zinc sulphide(ZnS) and Mn2+-doped ZnS quantum dots is reported by the z-scan technique,with nanosecond pulsed laser radiation at 355 nm.The observed values of the 2PA cross section of all the samples are 105 times larger than that of bulk ZnS. 相似文献
40.
Kumar Nagesh Varma G. D. Nath R. Srivastava A. K. 《Applied Physics A: Materials Science & Processing》2011,104(4):1169-1174
In this paper we report a simple method that enables the easy fabrication of ordered ZnO nanowire arrays using Anodic Aluminium
Oxide (AAO) template. We have used a vacuum injection technique to fill solution into the pores of an AAO template. The AAO
template has been fabricated by a two-step anodization process using 0.3 M oxalic acid (H2C2O4) solution under a constant voltage of 40 V. The AAO template formed through this process has been detached from Al substrate
via an anodic voltage pulse using perchloric acid (HClO4) solution (70%). The nanowires of ZnO have been synthesized by injecting the saturated Zn(NO3)2 solution into the pores of the detached AAO template using a vacuum pump. The ZnO nanowires synthesized by this technique
have been found dense & continuous with uniform diameter throughout the length of the wire. The structural characteristics
of AAO template and ZnO nanowires have been studied by Field Emission Scanning Electron Microscope (FESEM), Atomic force microscope
(AFM) and Transmission Electron Microscope (TEM). 相似文献