全文获取类型
收费全文 | 2982篇 |
免费 | 234篇 |
国内免费 | 303篇 |
专业分类
化学 | 340篇 |
晶体学 | 17篇 |
力学 | 249篇 |
综合类 | 68篇 |
数学 | 2196篇 |
物理学 | 649篇 |
出版年
2024年 | 3篇 |
2023年 | 34篇 |
2022年 | 47篇 |
2021年 | 44篇 |
2020年 | 66篇 |
2019年 | 79篇 |
2018年 | 70篇 |
2017年 | 75篇 |
2016年 | 81篇 |
2015年 | 60篇 |
2014年 | 104篇 |
2013年 | 218篇 |
2012年 | 111篇 |
2011年 | 115篇 |
2010年 | 158篇 |
2009年 | 200篇 |
2008年 | 196篇 |
2007年 | 215篇 |
2006年 | 158篇 |
2005年 | 172篇 |
2004年 | 168篇 |
2003年 | 152篇 |
2002年 | 155篇 |
2001年 | 124篇 |
2000年 | 117篇 |
1999年 | 97篇 |
1998年 | 106篇 |
1997年 | 87篇 |
1996年 | 63篇 |
1995年 | 46篇 |
1994年 | 50篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有3519条查询结果,搜索用时 15 毫秒
131.
Joachim Gwinner 《Optimization》2018,67(7):1017-1030
AbstractThis paper is concerned with elliptic variational inequalities that depend on two parameters. First, we investigate the dependence of the solution of the forward problem on these parameters and prove a Lipschitz estimate. Then, we study the inverse problem of identification of these two parameters and formulate two optimization approaches to this parameter identification problem. We extend the output least-squares approach, provide an existence result and establish a convergence result for finite-dimensional approximation. Further, we investigate the modified output least-squares approach which is based on energy functionals. This latter approach can be related to vector approximation. 相似文献
132.
针对给出的函数y=f(x),x∈[a,b],将其值域进行n等分,设yi为其中任一分点,对应x=xi(i=1,2,…,m),用GM(1,1)模型对序列{x1,x2,…,xm}进行预测,得到曲线y=f(x)在下一段时间与直线y=yi的交点位置.当GM(1,1)模型的误差较大时,可利用带有残差修正的GM(1,1)模型进行残差修正,以提高GM(1,1)模型预测值的精确度. 相似文献
133.
In this paper, we considered the multiple rogue wave solutions of a (3+1)-dimensional Hirota bilinear equation by using a symbolic computation approach. Based on the bilinear form of this equation, the first-order rogue waves, the second-order rogue waves and the third-order rogue waves are presented. Moreover, some basic properties of multiple rogue waves and their collision structures are explained by drawing the three dimensional plot. 相似文献
134.
Volker D. Burkert 《中国物理 C》2009,33(12):1043-1050
Recent measurements of nucleon resonance transition form factors with CLAS at Jefferson Lab are discussed. The new data confirm the assertion of the symmetric constituent quark model of the Roper as the first radial excitation of the nucleon. The data on high Q2 nπ+ production better constrain the branching ratios liNK and [3Nn. For the first time, the longitudinal transition amplitude to the S11(1535) was extracted from the nπ+ data. Also, new results on the transition amplitudes for the D13(1520) resonance are presented showing a rapid transition from helicity 3/2 dominance seen at the real photon point to helicty 1/2 dominance at higher Q2. I also discuss the status of the search for new excited nucleon states. 相似文献
135.
B. Z. Shavarovskii 《Mathematical Notes》1998,64(5):663-673
The structure of polynomial matrices in connection with their reducibility by semiscalar-equivalent transformations and similarity
transformations to simpler forms is considered. In particular, the canonical form of polynomial matrices without multiple
characteristic roots with respect to the above transformations is indicated. This allows one to establish a canonical form
with respect to similarity for a certain type of finite collections of numerical matrices.
Translated fromMatematicheskie Zametki, Vol. 64, No. 5, pp. 769–782, November, 1998. 相似文献
136.
Within framework of zero curvature representation theory, a family of integrable rational semi-discrete systems is derived from a matrix spectral problem. The Hamiltonian forms of obtained semi-discrete systems are constructed by means of the discrete trace identity. The Liouville integrability for the obtained family is demonstrated. In the end, a reduced family of obtained semi-discrete systems and its Hamiltonian form are worked out. 相似文献
137.
Jiunn-Wei Chen Hiroaki Kohyama Kazuaki Ohnishi Udit Raha Yue-Long Shen 《Physics letters. [Part B]》2010
We present a combined analysis of the space- and time-like electromagnetic pion form factors in light-cone perturbative QCD with transverse momentum dependence and Sudakov suppression. Including the genuine non-perturbative “soft” QCD and the power suppressed twist-3 corrections to the standard twist-2 perturbative QCD result, the experimental form factor data available at moderate energies/momentum transfers can be explained reasonably well. To this end, the bulk of the existing discrepancy between the space- and time-like experimental data is ostensibly reconciled. 相似文献
138.
The importance of anharmonic effect in dissociation of molecular systems especially clusters has been noted. In this paper, we shall study the effect of coupled anharmonic oscillator of the standard bilinear form (SBF) Morse oscillator (MO) potential on unimolecular reaction. We shall use the systematic theoretical approach, YL method, proposed by Yao and Lin (YAO L, et. al. J Phys Chem A, 2007, 111(29): 6722-6729), which can evaluate anharmonic effects on the rate constants based on the transition state theory. In treating the anharmonic effect with the Morse oscillator potential on unimolecular reactions under collision-free conditions by using the RRKM (Rice-Ramsperger-Kassel-Marcus) theory, the in-verse Laplace transformation of the partition functions was used to obtain the total amount of state and density of state by using the first-order and the second-order approximations of the saddle-point method. To demonstrate the anharmonic effect of the SBF Morse model, we choose some model systems and a real reaction as examples. 相似文献
139.
《Analytical letters》2012,45(12):1958-1975
The electrooxidative behavior and determination of lercanidipine (LRC) were investigated in aqueous acetonitrile medium at a boron-doped diamond electrode using voltammetric techniques. The LRC in selected supporting electrolyte presents a well-defined anodic response at 0.944 V, studied by the proposed method. The linear response was obtained in the ranges of 4 × 10?6 to 2 × 10?4 mmol L?1 range in 0.5 mmol L?1 sulfuric acid supporting electrolyte and 1 × 10?5 to 8 × 10?5 mmol L?1 range in spiked serum sample for square wave voltammetric technique. No electroactive interferences from the excipients and endogenous substances were found in the pharmaceutical dosage form and in the biological sample, respectively. 相似文献
140.
Controllable synthesis and characterization of ammonium polyphosphate with crystalline form V by phosphoric acid process 总被引:2,自引:0,他引:2
Gousheng Liu Wenyan Chen Xinchun Liu Jianguo Yu 《Polymer Degradation and Stability》2010,95(9):1834-12155
Ammonium polyphosphate (APP) with crystalline form V (APP-V) was synthesized by heating a mixture of 85% food-grade phosphoric acid and melamine under dry ammonia atmosphere. Effects such as raw material ratios, charging methods, dehydration temperature, condensation temperature and condensation time were investigated. Its water solubility was tested, its XRD and FTIR were characterized and compared with those of industrial APP-I and APP-II. Results showed that the prepared APP-V was insoluble in water, its XRD spectrum was the same as APP-V in literature. The molecular structures of the prepared APP-V and APP-I/APP-II were speculated and discussed in detail. 相似文献