全文获取类型
收费全文 | 5576篇 |
免费 | 444篇 |
国内免费 | 442篇 |
专业分类
化学 | 548篇 |
晶体学 | 12篇 |
力学 | 703篇 |
综合类 | 114篇 |
数学 | 4322篇 |
物理学 | 763篇 |
出版年
2024年 | 7篇 |
2023年 | 64篇 |
2022年 | 75篇 |
2021年 | 74篇 |
2020年 | 118篇 |
2019年 | 140篇 |
2018年 | 157篇 |
2017年 | 164篇 |
2016年 | 188篇 |
2015年 | 167篇 |
2014年 | 253篇 |
2013年 | 430篇 |
2012年 | 281篇 |
2011年 | 301篇 |
2010年 | 230篇 |
2009年 | 332篇 |
2008年 | 358篇 |
2007年 | 355篇 |
2006年 | 315篇 |
2005年 | 298篇 |
2004年 | 254篇 |
2003年 | 240篇 |
2002年 | 224篇 |
2001年 | 176篇 |
2000年 | 175篇 |
1999年 | 158篇 |
1998年 | 137篇 |
1997年 | 108篇 |
1996年 | 103篇 |
1995年 | 68篇 |
1994年 | 81篇 |
1993年 | 43篇 |
1992年 | 57篇 |
1991年 | 41篇 |
1990年 | 35篇 |
1989年 | 32篇 |
1988年 | 23篇 |
1987年 | 25篇 |
1986年 | 21篇 |
1985年 | 18篇 |
1984年 | 28篇 |
1983年 | 8篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1973年 | 2篇 |
排序方式: 共有6462条查询结果,搜索用时 171 毫秒
161.
Comment on “On the Neumann function and the method of images in spherical and ellipsoidal geometry”
下载免费PDF全文
![点击此处可从《Mathematical Methods in the Applied Sciences》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this note, we point out two errors in the article “On the Neumann function and the method of images in spherical and ellipsoidal geometry” by Dassios and Sten. Two corrections are then proposed. 相似文献
162.
Giuseppe Maria Coclite 《偏微分方程通讯》2013,38(8):1253-1272
We consider a shallow water equation of the Camassa–Holm type, which contains nonlinear dispersive effects as well as fourth order dissipative effects. We prove that as the diffusion and dispersion parameters tend to zero, with a condition on the relative balance between these two parameters, smooth solutions of the shallow water equation converge to discontinuous weak solutions of a scalar conservation law. The proof relies on deriving suitable a priori estimates together with an application of the compensated compactness method in the L p setting. 相似文献
163.
This paper presents an exhaustive approach to optimality theory in semi-infinite linear programming, placing a special emphasis on generality. After surveying optimality conditions for general problems, a detailed analysis is made of problems in which the coefficients are continuous functions of a parameter which varies on a compact set, adopting a feasible directions approach. Lastly, the case of analytical coefficients over an interval is considered in some detail. 相似文献
164.
J. Pouget 《Phase Transitions》2013,86(1-4):251-260
On the basis of a lattice model the domain structure for ferroelastic transformations is examined. The model accounts for both strongly nonlinear and competing interactions which allow for, in some situations, the propagation of nonlinear excitations. The model can be mostly applied to proper ferroelastic transformations of which In-Tl, Ti-Ni, etc.… are good prototypes. The phonon dispersion of the transverse acoustic waves obtained in the linearized case is discussed and the results show first a phonon softening at nonzero wave-number and next an upwards convexity of the phonon branch near the long-wavelength limit. This can be seen as pre-transitional effects. In a fully nonlinear case we consider vanishing dilatation transformations and the continuum approximation is applied to the one-dimensional version. Then, we investigate nonlinear excitations; three main classes of solution are found: i) quasi-harmonic solutions corresponding to periodically modulated structures in space which is a precursor effect of the elastic transformation, ii) an array of solitons made of periodic arrangements of parent-elastic domains and iii) a moving strain soliton. All the significant results are numerically illustrated by means of the microscopic model. Finally, the similarity to martensitic transformations and some extensions of the model are outlined. 相似文献
165.
Guangwen Yang Wentao Wu Zhixiang Li Naiwu Chen Jian Qin Guoping Hu Yang Zhang Jian Li Shuhui Chen 《Tetrahedron letters》2018,59(6):532-536
hNav1.7 had received great interest in the past decade owing to its attractive mechanism of actions in pain processing pathway. More recently, we developed a series of efficacious hNav1.7 inhibitors for analgesic, which were characterized with a novel aminocyclohexene as pharmacophore. Herein, we reported our synthetic efforts to construct the unique scaffold, which can be rapidly accessed from readily available 7-azanorbornenes via an unexpected catalyst-free, LiAlH4 mediated tandem double bond migration-ring opening sequence. A probable mechanism was proposed to illuminate the good regio- and stereoselectivity. 相似文献
166.
《应用有机金属化学》2017,31(6)
{Fe3O4@SiO2@(CH2)3‐thiourea dioxide‐SO3H/HCl}, a newly reported nanomagnetic core–shell supported solid acid catalyst, was successfully employed in the preparation of 4,4′‐(arylmethylene)bis(1H –pyrazol‐5‐ol) and pyrano[3,2‐c ]pyrazole derivatives. The presented methods are very efficient and high‐yielding. Also, the catalyst exhibited powerful potential for reusability in both types of reactions. 相似文献
167.
By taking the coupling effect into consideration, we study the resonance condition of a photonic wire microring resonator (PWRR) sensor and compare our results with the previous work. Simulation results show that the resonant wavelength and sensitivity strongly depend on the coupling strength. The difference caused by the coupling effect can be up to tens of nanometers for the resonant peak position and tens of nm/RIU for the sensitivity in a silicon-on-insulator (SOI) PWRR. Such a giant influence from coupling effect cannot be disregarded and should be considered seriously for the design and application of PWRRs. It also shows an alternative tuning technique by controlling the coupling strength. 相似文献
168.
《Optimization》2012,61(11):2277-2287
Two adaptive choices for the parameter of Dai–Liao conjugate gradient (CG) method are suggested. One of which is obtained by minimizing the distance between search directions of Dai–Liao method and a three-term CG method proposed by Zhang et al. and the other one is obtained by minimizing Frobenius condition number of the search direction matrix. Global convergence analyses are made briefly. Numerical results are reported; they demonstrate effectiveness of the suggested adaptive choices. 相似文献
169.
Distinguishability plays a crucial rule in studying observability of hybrid system such as switched system. Recently, for two linear systems, Lou and Si gave a condition not only necessary but also sufficient to the distinguishability of linear systems. However, the condition is not easy enough to verify. This paper will give a new equivalent condition which is relatively easy to verify. 相似文献
170.
Synergetic catalytic effect of rGO,Pd, Fe3O4 and PPy as a magnetically separable and recyclable nanocomposite for coupling reactions in green media
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, rGO/Pd–Fe3O4@PPy as an efficient stable nanocomposite was synthesized. To understand the synergetic effects of rGO, Pd, Fe3O4 and PolyPyrrole, the performance of rGO/Pd–Fe3O4@PPy as a heterogeneous recyclable nanocatalyst in the green synthesis of C‐C and C‐O coupling products, as well as different conditions are studied. Synthesized rGO/Pd–Fe3O4@PPy was characterized by FT‐IR, XRD, FE‐SEM, EDS, TGA and AFM analysis. Best results are obtained under sonication in H2O for C‐C coupling and by ball‐milling for C‐O coupling. The benefits of this method include: green solvents and conditions, absence of external base, low reaction times with high yield and easy work‐up method. 相似文献