全文获取类型
收费全文 | 7099篇 |
免费 | 1497篇 |
国内免费 | 848篇 |
专业分类
化学 | 4155篇 |
晶体学 | 68篇 |
力学 | 631篇 |
综合类 | 70篇 |
数学 | 1247篇 |
物理学 | 3273篇 |
出版年
2024年 | 13篇 |
2023年 | 81篇 |
2022年 | 135篇 |
2021年 | 238篇 |
2020年 | 325篇 |
2019年 | 278篇 |
2018年 | 235篇 |
2017年 | 271篇 |
2016年 | 350篇 |
2015年 | 297篇 |
2014年 | 422篇 |
2013年 | 637篇 |
2012年 | 427篇 |
2011年 | 432篇 |
2010年 | 343篇 |
2009年 | 436篇 |
2008年 | 408篇 |
2007年 | 374篇 |
2006年 | 417篇 |
2005年 | 346篇 |
2004年 | 368篇 |
2003年 | 304篇 |
2002年 | 270篇 |
2001年 | 226篇 |
2000年 | 223篇 |
1999年 | 200篇 |
1998年 | 173篇 |
1997年 | 150篇 |
1996年 | 132篇 |
1995年 | 112篇 |
1994年 | 104篇 |
1993年 | 93篇 |
1992年 | 88篇 |
1991年 | 58篇 |
1990年 | 64篇 |
1989年 | 46篇 |
1988年 | 62篇 |
1987年 | 51篇 |
1986年 | 47篇 |
1985年 | 30篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 18篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1973年 | 8篇 |
排序方式: 共有9444条查询结果,搜索用时 890 毫秒
71.
本文导出了考虑外场和束流效应后束流均方根发射度平方变化方程的一般表达式,并就仅考虑外场,仅考虑空间电荷场和仅考虑尾场等三种特殊情况进行了分析。 相似文献
72.
S. Sarkar A. D. Thakur C. V. Tomy G. Balakrishnan D. McK Paul S. Ramakrishnan A. K. Grover 《Pramana》2006,66(1):193-207
New experimental data are presented on the scan rate dependence of the magnetization hysteresis width ΔM(H) (∞ critical current densityJ
c(H)) in isothermalMH scans in a weakly pinned single crystal of Ca3Rh4Sn13, which displays second magnetization peak (SMP) anomaly as distinct from the peak effect (PE). We observe an interesting
modulation in the field dependence of a parameter which purports to measure the dynamical annealing of the disordered bundles
of vortices injected through the sample edges towards the destined equilibrium vortex state at a givenH. These data, in conjunction with the earlier observations made while studying the thermomagnetic history dependence inJ
c(H) in the tracing of the minor hysteresis loops, imply that the partially disordered state heals towards the more ordered state
between the peak field of the SMP anomaly and the onset field of the PE. The vortex phase diagram in the given crystal of
Ca3Rh4Sn13 has been updated in the context of the notion of the phase coexistence of the ordered and disordered regions between the
onset field of the SMP anomaly and the spinodal line located just prior to the irreversibility line. A multi-critical point
and a critical point in the (H,T) region of the Bragg glass phase have been marked in this phase diagram and the observed behavior is discussed in the light
of recent data on multi-critical point in the vortex phase diagram in a single crystal of Nb. 相似文献
73.
74.
We make a thorough non-covariant analysis of the derivation of the equation of motion for a charged particle, including radiation reaction, by means of a simple model for the charge: a dumbbell. This model and our method to expand retarded quantities, based on complex-variable theory, allow us to avoid some of the usual approximations, so we can show several features of the radiation reaction problem. 相似文献
75.
76.
Prof. A. D. Drozdov 《Archive of Applied Mechanics (Ingenieur Archiv)》1995,65(2):99-109
Summary Dynamic stability of an elastic bar with voids is considered. Using the Lyapunov approach some new sufficient stability conditions are obtained and explicit expressions for the critical load are derived. 相似文献
77.
Investigation on ultrafast thrid—order optical nonlinearity of metal(dmit)2/mnt)2 Charge transfer complexes 下载免费PDF全文
We have investigated the transient third-order optical nonlinearity of the solutions of Metal(dmit)2/(mnt)2 salts in acetone by employing femtosecond optical Kerr gate measurement at 830nm wavelength.An order of enhancement on the second-order hyperppolarizability is found for the above salts with central atoms of Cu and Ni.We have suggested an explanation for the enhancement based on the extension of electronic conjugation by the entring Cu or Ni atom. 相似文献
78.
Guey‐Sheng Liou Hung‐Yi Lin Yu‐Lun Hsieh Yi‐Lung Yang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4921-4932
N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine was synthesized from N‐(4‐nitrophenyl)‐diphenylamine by the Vilsmeier‐Haack reaction. Soluble aromatic poly(azomethine)s (PAMs) were prepared by the solution polycondensation of N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine and aromatic diamine in N‐methyl‐2‐pyrrolidone (NMP) at room temperature under reduced pressure. All the PAMs are highly soluble in various organic solvents, such as N,N‐dimethylacetamide (DMAc), chloroform (CHCl3), and tetrahydrofuran (THF). Differential scanning calorimetry (DSC) indicated that these PAMs had glass‐transition temperatures (Tgs) in the range of 170–230 °C, and a 10% weight‐loss temperatures in excess of 490 °C with char yield at 800 °C in nitrogen higher than 60%. These PAMs in NMP solution showed UV‐Vis charge‐transfer (CT) absorption at 405–421 nm and photoluminescence peaks around 462–466 nm with fluorescence quantum efficiency (ΦF) 0.10–0.99%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of these PAMs can be determined from cyclic voltammograms as 4.86–5.43 and 3.31–3.34 eV, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4921–4932, 2007 相似文献
79.
80.
Orewczyk J. Jasieńska S. Iwanczenko S. 《Journal of Thermal Analysis and Calorimetry》1998,54(1):79-84
This paper presents applications of thermal analysis to observe the course of reduction of acidic pellets, metallurgical substances
whose reducibility and strength are basic parameters of use in blast furnace processes. Both parameters depend on the mineral
composition of the samples. The investigations included determination of the chemical and phase compositions of the initial
samples and reduction products.
Research was conducted on acidic pellets from Połtawa (Poland), applied in the T. Sendzimir Steelworks (Poland), in comparison
with pellets from Brazil, Canada and Lebedyn (Russia).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献