全文获取类型
收费全文 | 9336篇 |
免费 | 2291篇 |
国内免费 | 761篇 |
专业分类
化学 | 1441篇 |
晶体学 | 143篇 |
力学 | 725篇 |
综合类 | 194篇 |
数学 | 4282篇 |
物理学 | 5603篇 |
出版年
2024年 | 16篇 |
2023年 | 95篇 |
2022年 | 223篇 |
2021年 | 287篇 |
2020年 | 274篇 |
2019年 | 251篇 |
2018年 | 261篇 |
2017年 | 355篇 |
2016年 | 379篇 |
2015年 | 297篇 |
2014年 | 566篇 |
2013年 | 866篇 |
2012年 | 597篇 |
2011年 | 724篇 |
2010年 | 573篇 |
2009年 | 595篇 |
2008年 | 663篇 |
2007年 | 719篇 |
2006年 | 594篇 |
2005年 | 488篇 |
2004年 | 431篇 |
2003年 | 461篇 |
2002年 | 391篇 |
2001年 | 324篇 |
2000年 | 301篇 |
1999年 | 237篇 |
1998年 | 214篇 |
1997年 | 210篇 |
1996年 | 153篇 |
1995年 | 121篇 |
1994年 | 82篇 |
1993年 | 86篇 |
1992年 | 66篇 |
1991年 | 53篇 |
1990年 | 52篇 |
1989年 | 47篇 |
1988年 | 60篇 |
1987年 | 39篇 |
1986年 | 30篇 |
1985年 | 46篇 |
1984年 | 24篇 |
1983年 | 11篇 |
1982年 | 33篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 12篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
71.
In this paper, an interior point cutting plane method (IPCPM)is applied to solve optimal power flow (OPF) problems. Comparedwith the simplex cutting plane method (SCPM), the IPCPM is simpler,and efficient because of its polynomial-time characteristic.Issues in implementing IPCPM for OPF problems are addressed,including (1) how to generate cutting planes without using thesimplex tableau, (2) how to identify the basis variables inIPCPM, and (3) how to generate mixed integer cutting planes.The calculation speed of the proposed algorithm is further enhancedby utilizing the sparsity features of the OPF formulation. Numericalsimulations on IEEE 14-300-bus test systems have shown thatthe proposed method is effective. 相似文献
72.
73.
Hirofumi Tsumura. 《Mathematics of Computation》2004,73(245):251-258
In this paper, we give some evaluation formulas for Tornheim's type of alternating series by an elementary and combinatorial calculation of the uniformly convergent series. Indeed, we list several formulas for them by means of Riemann's zeta values at positive integers.
74.
The asymptotic behaviour of partial sums of generalized hypergeometric series of unit argument is investigated.
75.
增长曲线模型中回归系数的广义根方估计 总被引:6,自引:0,他引:6
本文对增长曲线模型中的回归系数B提出了一种新的估计形式-广义根方估计的B(K),其中K=diag(k1,k2,…,kp)并证明了通过广义根方偏参数ki(i=1,2,…,p)的适当选取可使得该估计在均方误差矩阵的意义下优于已有的LS估计和根方估计,及广义根方估计是可容许估计,本文还给出了选取广义根方偏参数的两种方法,算法及一个应用实例。 相似文献
76.
Frequency dependence of ac conductivity from 1 to 105 Hz and time series of the conductivity at 2 kHz were measured along c-axis of thulium nitrate crystal, Tm(NO3)36H2O at temperatures from 203.15 to 293.15 K. The meta-stability was observed. The frequency spectra of the conductivity were similar to those in disorder system. Aging effect was observed. Non-periodic instability (burst) was found. Non-linear dynamical property was characterized by 1/f noise spectrum, limit cycle in return map and dependence of correlation exponent on embedding dimension. 相似文献
77.
Cordula Grüttner Knut Müller Joachim Teller Fritz Westphal Allan Foreman Robert Ivkov 《Journal of magnetism and magnetic materials》2007
Bionized nanoferrite (BNF) particles with high specific power absorption rates were synthesized in the size range of 20–100 nm by high-pressure homogenization for targeted cancer therapy with alternating magnetic fields. Several strategies were used to conjugate antibodies to the BNF particles. These strategies were compared using an immunoassay to find optimal conditions to reach a high immunoreactivity of the final antibody–particle conjugate. 相似文献
78.
Following our investigation of the USA Standard and Poor index anti-bubble that started in August 2000 (Quant. Finance 2 (2002) 468), we analyze 38 world stock market indices and identify 21 “bearish anti-bubbles” and six “bullish anti-bubbles”. An “anti-bubble” is defined as a self-reinforcing price trajectory with self-similar expanding log-periodic oscillations. Mathematically, a bearish anti-bubble is characterize by a power law decrease of the price (or of the logarithm of the price) as a function of time and by expanding log-periodic oscillations. We propose that bearish anti-bubbles are created by positive price-to-price feedbacks feeding overall pessimism and negative market sentiment further strengthened by inter-personal interactions. Bullish anti-bubbles are here identified for the first time. The most striking discovery is that the majority of European and Western stock market indices as well as other stock indices exhibit practically the same log-periodic power law anti-bubble structure as found for the USA S&P500 index. These anti-bubbles are found to start approximately at the same time, August 2000, in all these markets. This shows a remarkable degree of worldwide synchronization. The descent of the worldwide stock markets since 2000 is thus an international event, suggesting the strengthening of globalization. 相似文献
79.
LIU Zhongkui 《数学年刊B辑(英文版)》2004,25(1):129-138
Let (S,≤) be an ordered set. Recall that (S,≤) is artinian if every strictly decreasingsequence of elements of S is ?nite, and that (S,≤) is narrow if every subset of pairwiseorder-incomparable elements of S is ?nite. Let S be a commutative monoid. Unl… 相似文献
80.
In this paper, we suggest and analyze a new two-step predictor–corrector type iterative method free from second derivatives for solving nonlinear equations of the type f(x)=0. This new method includes the two-step Newton method as a special case. We prove that the new iterative method is of fourth-order. Several examples are given to illustrate the efficiency of this new method and its comparison with other iterative methods. This method can be considered as a significant improvement of the Newton method and its variant forms. 相似文献