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   1154篇
  免费   76篇
  国内免费   2篇
化学   845篇
晶体学   2篇
力学   12篇
数学   159篇
物理学   136篇
无线电   78篇
  2023年   13篇
  2022年   6篇
  2021年   15篇
  2020年   26篇
  2019年   19篇
  2018年   21篇
  2017年   15篇
  2016年   41篇
  2015年   47篇
  2014年   49篇
  2013年   71篇
  2012年   96篇
  2011年   85篇
  2010年   52篇
  2009年   64篇
  2008年   72篇
  2007年   87篇
  2006年   77篇
  2005年   74篇
  2004年   52篇
  2003年   48篇
  2002年   31篇
  2001年   13篇
  2000年   14篇
  1999年   11篇
  1998年   9篇
  1997年   10篇
  1996年   11篇
  1995年   8篇
  1994年   9篇
  1993年   3篇
  1992年   6篇
  1991年   9篇
  1990年   5篇
  1989年   3篇
  1988年   6篇
  1987年   5篇
  1986年   7篇
  1985年   5篇
  1984年   11篇
  1982年   4篇
  1981年   2篇
  1980年   3篇
  1979年   3篇
  1974年   3篇
  1973年   3篇
  1967年   1篇
  1952年   1篇
  1929年   1篇
  1925年   1篇
排序方式: 共有1232条查询结果,搜索用时 468 毫秒
151.
152.
Option pricing and perfect hedging on correlated stocks   总被引:2,自引:0,他引:2  
We develop a theory for option pricing with perfect hedging in an inefficient market model where the underlying price variations are autocorrelated over a time τ0. This is accomplished by assuming that the underlying noise in the system is derived by an Ornstein-Uhlenbeck, rather than from a Wiener process. With a modified portfolio consisting in calls, secondary calls and bonds we achieve a riskless strategy which results in a closed and exact expression for the European call price which is always lower than Black-Scholes price. We obtain the same price and a modified delta hedging if we start from an effective one-dimensional market model. We compare these strategies and study the sensitivity of the call price to several parameters where the correlation effects are also observed.  相似文献   
153.
Both bilirubin and biliverdin, via their cesium salts, have been covalently attached to an insoluble polystyrene matrix (the so-called Nbb-resin), some chemical transformations have been carried out upon the supported pigments, and the resulting products have been detached by alkaline methanol.  相似文献   
154.
Expressions for the second-row nuclei chemical shifts calculation using a CNDO-SCF wave function are outlined. In collating it with the Pugmire and Grant's equations, a term with a changed sign appears. Both sets of equations are applied to a study of carbon-13 chemical shifts in alkanes down to C7; results are interpreted with aid of the Lindeman–Adams' empirical equation. Expressions proposed are confirmed for an excellent agreement with experimental data.  相似文献   
155.
156.
Cooperative transmission can be seen as a “virtual” MIMO system, where the multiple transmit antennas are in fact implemented distributed by the antennas both at the source and the relay terminal. Depending on the system design, diversity/multiplexing gains are achievable. This design involves the definition of the type of retransmission (incremental redundancy, repetition coding), the design of the distributed space-time codes, the error correcting scheme, the operation of the relay (decode & forward or amplify & forward) and the number of antennas at each terminal. Proposed schemes are evaluated in different conditions in combination with forward error correcting codes (FEC), both for linear and near-optimum (sphere decoder) receivers, for its possible implementation in downlink high speed packet services of cellular networks. Results show the benefits of coded cooperation over direct transmission in terms of increased throughput. It is shown that multiplexing gains are observed even if the mobile station features a single antenna, provided that cell wide reuse of the relay radio resource is possible.  相似文献   
157.
An axiomatic characterization of ‘a Banzhaf score’ notion is provided for a class of games called (j,k) simple games with a numeric measure associated to the output set, i.e., games with n players, j ordered qualitative alternatives in the input level and k possible ordered quantitative alternatives in the output. Three Banzhaf measures are also introduced which can be used to determine a player's ‘a priori’ value in such a game. We illustrate by means of several real world examples how to compute these measures. Research partially supported by Grant BFM 2003-01314 of the Science and Technology Spanish Ministry and the European Regional Development Fund.  相似文献   
158.
159.
The metastable phase diagram of the two-component system heptyloxycyanobiphenyl (7OCB)+nonyloxycyanobiphenyl (9OCB) was determined by means of modulated differential scanning calorimetry (MDSC) and optical microscopy measurements. It was experimentally established that the 7OCB+9OCB two-component system exhibits a monotropic re-entrant nematic behavior. A complete quantitative thermodynamic analysis, through Oonk's equal G analysis, was performed, allowing for the calculation of the monotropic re-entrant behavior and the prediction of two tricritical points, one of them experimentally accessible for the SmAd-to-N transition and the other non-experimentally accessible for the RN-to-SmAd transition. From specific-heat measurements, latent heats were obtained for those mixtures displaying a first-order SmAd-to-N transition. Additionally, for some mixtures, the specific-heat critical exponents (alpha), through the second-order SmAd-to-N transition, were obtained. Both batches of data enable us to access to the experimental tricritical temperature for the SmAd-to-N transition.  相似文献   
160.
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