全文获取类型
收费全文 | 2108篇 |
免费 | 191篇 |
国内免费 | 217篇 |
专业分类
化学 | 1439篇 |
晶体学 | 22篇 |
力学 | 104篇 |
综合类 | 12篇 |
数学 | 309篇 |
物理学 | 630篇 |
出版年
2024年 | 4篇 |
2023年 | 8篇 |
2022年 | 56篇 |
2021年 | 63篇 |
2020年 | 42篇 |
2019年 | 59篇 |
2018年 | 50篇 |
2017年 | 47篇 |
2016年 | 72篇 |
2015年 | 71篇 |
2014年 | 84篇 |
2013年 | 162篇 |
2012年 | 156篇 |
2011年 | 169篇 |
2010年 | 126篇 |
2009年 | 103篇 |
2008年 | 144篇 |
2007年 | 123篇 |
2006年 | 145篇 |
2005年 | 112篇 |
2004年 | 80篇 |
2003年 | 67篇 |
2002年 | 85篇 |
2001年 | 52篇 |
2000年 | 62篇 |
1999年 | 47篇 |
1998年 | 30篇 |
1997年 | 29篇 |
1996年 | 28篇 |
1995年 | 32篇 |
1994年 | 23篇 |
1993年 | 16篇 |
1992年 | 18篇 |
1991年 | 5篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 4篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 6篇 |
排序方式: 共有2516条查询结果,搜索用时 15 毫秒
1.
J. Giroire T. Ha‐Duong V. Moumas 《Mathematical Methods in the Applied Sciences》2005,28(13):1527-1552
This article deals with a boundary value problem for Laplace equation with a non‐linear and non‐local boundary condition. This problem comes from petroleum engineering and is used to obtain an estimation of well productivity. The non‐linear and non‐local boundary condition is written on the well boundary. On the outer reservoir boundaries, we have both Dirichlet and Neumann conditions. In this paper, we prove the existence and uniqueness of a solution to this problem. The existence is proved by Schauder theorem and the uniqueness is obtained under more restricted conditions, when the involved operator is a contraction. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
2.
通过把全息透镜嵌入挡风玻璃,实现全息透镜在车辆中的两种应用,即将具有颜色选择性的窄带全息透镜用于车辆的平视显示,将具有角度选择性的宽带全息透镜用于车辆的阳光防护。 相似文献
3.
用线性插值法求单摆运动周期的近似解 总被引:6,自引:1,他引:5
利用线性插值的方法,提出了一个任意摆角条件下的单摆运动周期的近似公式.并利用Mathematica软件将该公式与精确解进行了比较,还与其他近似公式进行了对比.结果表明,该公式的近似程度相当好. 相似文献
4.
Ha Yong Lee Se Hun Jung Soo Yong Lee Young Ho You Kyung Hyun Ko 《Applied Surface Science》2005,252(5):1891-1898
Al-Al2O3 composite coatings with different Al2O3 particle shapes were prepared on Si and Al substrate by cold spray. The powder compositions of metal (Al) and ceramic (Al2O3) having different sizes and agglomerations were varied into ratios of 10:1 wt% and 1:1 wt%. Al2O3 particles were successfully incorporated into the soft metal matrix of Al. It was found that crater formation between the coatings and substrate, which is typical characteristic signature of cold spray could be affected by initial starting Al2O3 particles. In addition, when the large hard particles of fused Al2O3 were employed, the deep and big craters were generated at the interface between coatings and hard substrates. In the case of pure soft metal coating such as Al on hard substrate, it is very hard to get proper adhesion due to lack of crater formation. Therefore, the composite coating would have certain advantages. 相似文献
5.
JUGuo-Xing ZhaoXian-Lin 《理论物理通讯》2002,37(4):397-404
The solution transformations and properties of the R-matrices for two-component systems under these transformations are analyzed in details.Not all transformed R-matrices can be put into the Skalyanin‘s formalism.For those R-matrices with all required properties,the effects of solution transformations to the six-and eight-vertex systems with open boundary conditions are discussed.these effects can be one of the following types:the Hamiltonian is invariant or transposition-invariant or made in a similarity transformation,or its coupling coefficients are multiplied by an overall factor,or the spin of the system is rotated around the z axis or/and reflected with respect to some plane.In these cases,the transformed systems remain to be integrable. 相似文献
6.
7.
The basic theory of symplectic algorithm was introduced. A comparison between Runge-Kutta method and symplectic integration method was preformed in the simulation of the long time behavior of H + H2 system on BKMP potential energy surface. Our results reveal a dis-sipative behavior in the integral of ordinary differential equation by the fourth order Runge-Kutta method, which causes incorrect simulation results in QCT calculations. However, when the symplectic integration method is applied, the dissipative behavior is not found in the same system. When the initial state is the same, the energy deviation of fourth order symplectic integral method is almost one percent of that of fourth order Runge-Kutta method in a 60000-step simulation, and that of sixth order symplectic integral method is much less. These results show that the symplectic integral methods are always the better choice in the integral calculation of the long time behavior in maintaining energy conservation. 相似文献
8.
The surface-enhanced Raman scatterings of dimethyl sulfide, diethyl sulfide and dimethyl disulfide have been investigated in silver sol. The dimethyl disulfide molecule decomposes on silver to the corresponding mercaptide implying facile cleavage of its S---S bond. The C---S bond in dialkyl monosulfide appears not to cleave on silver. For diethyl sulfide, the C2 conformation seems to be favorable on silver than other conformations. 相似文献
9.
本文用变分过渡态理论,首次对无鞍点的释能反应O+CS→CO+S、O+CO→CO+O和S+CS→CS+S进行了动力学研究,考察了反应动力学瓶颈区性质,计算了反应的速度常数,并将O+CS反应的速度常数值与实验值及经典轨迹计算结果进行了比较,三者基本相符. 相似文献
10.
Although there are numerous methods available to hydrolyze glycans utilizing strong acids, it all requires lengthy steps to obtain quantitative yield. We have developed a new simple one-step method for analysis of amino and neutral monosaccharides of glycoproteins quantitatively. Free monosaccharides were found to be stable during hydrolysis of glycans with 6 N HCI at 80 degrees C up to 2 h. Using this condition, analysis of free monosaccharides hydrolyzed from the bovine fetuin showed sugar composition of Gal: Man: GlcN: GaIN = 13.2: 11.0: 15.5: 2.6, which is closely matched with the reported value of 12.4: 9.6: 17.2: 2.7 (Townsend et al., ABRF News 8: 14, 1997). This method was shown to be applicable to varieties of well-characterized glycoproteins, erythropoietin, fibrinogen and soybean agglutinin. The amounts of sugars released under the condition were very close to the experimental values by other procedures or to the theoretical ones. This condition was found to be suitable for direct sugar analysis of fetuin, which have been immobilized onto polyvinylidene difluoride membrane. Based on these results, it support that the 6 N HCl/80 degrees C/2 h is the simplest method for quantitative analysis of monosaccharide composition of glycoproteins. 相似文献