首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6538篇
  免费   202篇
  国内免费   19篇
化学   3791篇
晶体学   102篇
力学   192篇
数学   661篇
物理学   2013篇
  2023年   57篇
  2022年   117篇
  2021年   107篇
  2020年   128篇
  2019年   135篇
  2018年   123篇
  2017年   91篇
  2016年   186篇
  2015年   139篇
  2014年   192篇
  2013年   430篇
  2012年   362篇
  2011年   444篇
  2010年   259篇
  2009年   237篇
  2008年   347篇
  2007年   346篇
  2006年   306篇
  2005年   271篇
  2004年   204篇
  2003年   156篇
  2002年   135篇
  2001年   108篇
  2000年   90篇
  1999年   62篇
  1998年   55篇
  1997年   53篇
  1996年   70篇
  1995年   72篇
  1994年   66篇
  1993年   86篇
  1992年   66篇
  1991年   42篇
  1990年   62篇
  1989年   55篇
  1988年   61篇
  1987年   58篇
  1986年   48篇
  1985年   69篇
  1984年   61篇
  1983年   64篇
  1982年   57篇
  1981年   60篇
  1980年   61篇
  1979年   50篇
  1978年   61篇
  1977年   46篇
  1976年   56篇
  1974年   51篇
  1973年   49篇
排序方式: 共有6759条查询结果,搜索用时 15 毫秒
41.
The disagreement of Danyluk and King's (Chem. Phys.25, 343 (1977)) rotational constants for levels lying near the dissociation limit of B-state I2 with the mechanical behavior predicted by near-dissociation theory is investigated. The discrepancies are shown to be much too large to be explained by either the neglect of centrifugal distortion effects in the original analysis or by rotational or spin-rotation coupling to a nearby repulsive 1u state. These differences are therefore attributed to experimental error, a conclusion which is confirmed by more recent experimental results. A reanalysis of the best available data for levels near the dissociation limit of B-state I2 then yields improved values for the B-state dissociation limit D = 20 043.16 (±0.02) cm?1 of the vibrational index at dissociation vD = 87.32 (±0.04) and of the long-range potential constant C5 = 2.88 (±0.03) × 105cm?1A?5. This in turn implies a slightly improved ground-state dissociation energy of D0 = 12 440.18 (±0.02) cm?1.  相似文献   
42.
This study sets out to examine whether the demand for softwood lumber in the United States is responsive to various market factors including the price of softwood lumber, the price of other building materials, and the level of economic activity (e.g. housing starts). Concern in the analysis is focused on overcoming some of the methodological shortcomings found in previous studies of this issue. The results are conclusive. The quantity of softwood lumber demanded does respond to the various economic factors considered. Moreover, when the structural stability of the estimated relationships is investigated, the results suggest that the demand for softwood lumber regionally in the United States has remained unaltered over the sample period (1950–1985).  相似文献   
43.
In this paper, we give sufficient conditions for the existence of (pseudo) weakly conformal and conformal families of measures for fibred systems. We describe a general construction principle for these families, modelled on the one developed by Denker and Urbanski for conformal measures. For those systems that are fibrewise local homeomorphisms, the constructed families are (pseudo) conformal. If a system is, moreover, weakly topologically exact along fibres, then each measure in the associated family is supported on the whole fibre where it is naturally defined.  相似文献   
44.
This paper presents an algorithm and the supporting theory for solving a class of nonlinear multiple criteria optimization problems using Zionts—Wallenius type of interaction. The Zionts—Wallenius method, as extended in this paper, can be used for solving multiple criteria problems with concave objective and (implicit) value functions and convex feasible regions. Modifications of the method to handle nonconvex feasible regions and general nonlinear objective functions are also discussed.This research was supported, in part, by a Faculty Research Development Award and by a Council of 100 Research Grant from Arizona State University (Roy), and by a grant from Y. Jahnsson Foundation, Finland (Wallenius). The research was performed while the second author was a Visiting Professor at Arizona State University.  相似文献   
45.
LetM n denote the space ofn×n matrices. GivenX, ZM n define
  相似文献   
46.
The analysis in this paper looks at two important elements in modelling the market for timber in the United States. First, the issue of directional causality between price and quantity and its implications in a modelling effort is investigated. Second, the extent of the geographic market for timber is discussed and a method of detecting it is suggested. The method for detecting the extent of the geographical market is tractable and can be applied in a straightforward way. Both considerations are applied to the softwood lumber market in the United States.  相似文献   
47.
The ferromagnetic shape memory alloy with nominal composition Ni54Fe19Ga27 is investigated by Ac susceptibility and resistivity measurements. The alloy shows long-range ferromagnetic order below 290 K. The anomaly due to the martensitic transition is observed in the susceptibility and resistivity data in the temperature range around 220 K, which is associated with clear thermal hysteresis. Minor hysteresis loop technique was used to investigate the phase coexistence across the martensitic transition, and our analysis indicate that both martensite and austenite phases mutually coexist in the region of hysteresis.  相似文献   
48.
The weak phase γ is conventionally probed by theB sρ 0 mode. The predicted rate is tiny. Even if aB sρ 0 K s rate difference could be established, it would not be clear that sin 2γ had been measured, because amplitudes with other weak phases may contribute significantly. Non-CP eigenstates, such asB s D s ± K ?, have a two-fold advantage overB sρ 0 K s. Their rates are orders of magnitude above that forB sρ 0 K s, and they probe theCP-violating phase γ, without any contamination from other weak phases. Detailed time-dependent studies of non-CP eigenstates remove possible final-state phases and extract the weak phase γ.  相似文献   
49.
50.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号