全文获取类型
收费全文 | 44902篇 |
免费 | 1632篇 |
国内免费 | 44篇 |
专业分类
化学 | 29151篇 |
晶体学 | 398篇 |
力学 | 820篇 |
数学 | 7152篇 |
物理学 | 9057篇 |
出版年
2023年 | 345篇 |
2022年 | 299篇 |
2021年 | 600篇 |
2020年 | 729篇 |
2019年 | 738篇 |
2018年 | 1001篇 |
2017年 | 929篇 |
2016年 | 1717篇 |
2015年 | 1393篇 |
2014年 | 1409篇 |
2013年 | 3020篇 |
2012年 | 2866篇 |
2011年 | 3162篇 |
2010年 | 1897篇 |
2009年 | 1601篇 |
2008年 | 2585篇 |
2007年 | 2432篇 |
2006年 | 2172篇 |
2005年 | 1939篇 |
2004年 | 1589篇 |
2003年 | 1247篇 |
2002年 | 1169篇 |
2001年 | 868篇 |
2000年 | 772篇 |
1999年 | 593篇 |
1998年 | 459篇 |
1997年 | 375篇 |
1996年 | 514篇 |
1995年 | 388篇 |
1994年 | 379篇 |
1993年 | 405篇 |
1992年 | 366篇 |
1991年 | 287篇 |
1990年 | 267篇 |
1989年 | 215篇 |
1988年 | 229篇 |
1987年 | 226篇 |
1986年 | 223篇 |
1985年 | 327篇 |
1984年 | 293篇 |
1983年 | 250篇 |
1982年 | 231篇 |
1981年 | 229篇 |
1980年 | 219篇 |
1979年 | 222篇 |
1978年 | 229篇 |
1977年 | 227篇 |
1976年 | 210篇 |
1975年 | 187篇 |
1973年 | 198篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
152.
153.
In the procduction of high-voltage insulating systems, disintegration and non-homogeneity occur in some cases and these factors can lead to the deterioration and even the breakdown such systems. In research into the causes of these phenomena DTA and TG were applied to study the course of hardening of the systems and to quantify the leaking substances. The results demonstrate the great value of thermal analysis in this field. 相似文献
154.
Dislocation motion in the real lattice of alloys is highly complex. In a certain temperature range the dynamic strain ageing phenomena have been reported. In this paper the influence of mobile solute atoms (as obstacles) on the motion of dislocation is analysed. Both processes are assumed to be thermally activated. A new model based on this assumption is proposed. The dislocation velocity and the friction stress (due to solute-dislocation interactions) are calculated. A change in the friction stress caused by solute mobility is discussed. 相似文献
155.
We have investigated the structure of spider dragline silk by X-ray diffraction over a broad temperature range from room temperature
up to thermal denaturation conditions. The dominating signal from the β-sheet crystallites is analyzed. Pronounced changes
of scattering intensity starting at temperatures around 150 °C are observed. These changes are discussed in view of the respective
lattice constants, crystal size, size distribution, crystallite number density and amino acid composition.
PACS 87.68.+z; 87.15.-v; 87.64.Bx 相似文献
156.
Rostislav Vodák 《Mathematical Methods in the Applied Sciences》2007,30(1):43-75
We consider a sequence of curved rods which consist of isotropic material and which are clamped on the lower base or on both bases. We study the asymptotic behaviour of the stress tensor and displacement under the assumptions of linearized elasticity when the cross‐sectional diameter of the rods tends to zero and the body force is given in the particular form. The analysis covers the case of a non‐smooth limit line of centroids. We show how the body force and the choice of the approximating curved rods can affect the strong convergence and the limit form of the stress tensor for the curved rods clamped on both bases. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
157.
A. S. Rodríguez L. R. B. Macías 《Journal of Radioanalytical and Nuclear Chemistry》1994,186(3):205-212
Ammonium uranate was precipitated from uranyl nitrate solution using gaseous ammonia, then filtered, washed with demineralized water and dried. The influence of pH and ammonia flow rate on their composition and structure were examined by X-ray diffraction analysis, making use of additional information obtained from infrared analysis. 相似文献
158.
Reduced charge montmorillonites (RCM) were prepared by the thermal treatment of lithiumsaturated montmorillonite. Samples prepared by mild thermal treatment with lithium contained more water sorbed than the original montmorrilonite. When RCMs were prepared, part of the lithium cations reacted with hydroxyl groups in the octahedral sheet and released protons, which reacted with the structure. Acid treatment probably enhanced the surface area. which was reflected in the amount of water sorbed. Deprotonation of hydroxyl groups was proved by the measurements of the ignition loss. The heating of lithium saturated montmorillonite at higher temperatures brough about the collapse of the interlayers and a decrease in the amount of water sorbed. 相似文献
159.
Manuel Fernández-López Eduardo García-Río Demir N. Kupeli 《Annals of Global Analysis and Geometry》2002,21(1):1-13
A characterization of time functions on a spacetime is made by using theMöbius equation. It is shown that a time function characterized in this wayyields past timelike geodesic incompleteness and local Lorentzian warpedproduct decomposition of spacetime, provided that the stress-energy tensoris a fluid. Also, by imposing additional assumptions on the stress-energytensor and global analytic structure of the spacetime, more restrictivedecompositions closer to Robertson–Walker spacetimes are obtained. 相似文献
160.
The primary resource for quantum computation is Hilbert-space dimension. Whereas Hilbert space itself is an abstract construction, the number of dimensions available to a system is a physical quantity that requires physical resources. Avoiding a demand for an exponential amount of these resources places a fundamental constraint on the systems that are suitable for scalable quantum computation. To be scalable, the effective number of degrees of freedom in the computer must grow nearly linearly with the number of qubits in an equivalent qubit-based quantum computer. 相似文献