全文获取类型
收费全文 | 133083篇 |
免费 | 33743篇 |
国内免费 | 38176篇 |
专业分类
化学 | 86987篇 |
晶体学 | 4065篇 |
力学 | 9130篇 |
综合类 | 3025篇 |
数学 | 19849篇 |
物理学 | 81946篇 |
出版年
2024年 | 544篇 |
2023年 | 1126篇 |
2022年 | 2812篇 |
2021年 | 2641篇 |
2020年 | 2694篇 |
2019年 | 3083篇 |
2018年 | 2971篇 |
2017年 | 4749篇 |
2016年 | 3739篇 |
2015年 | 5052篇 |
2014年 | 5530篇 |
2013年 | 8035篇 |
2012年 | 8780篇 |
2011年 | 10752篇 |
2010年 | 14425篇 |
2009年 | 15044篇 |
2008年 | 9870篇 |
2007年 | 8474篇 |
2006年 | 8123篇 |
2005年 | 7720篇 |
2004年 | 7311篇 |
2003年 | 5611篇 |
2002年 | 5415篇 |
2001年 | 5818篇 |
2000年 | 5282篇 |
1999年 | 4063篇 |
1998年 | 2897篇 |
1997年 | 2537篇 |
1996年 | 2809篇 |
1995年 | 3254篇 |
1994年 | 3276篇 |
1993年 | 3342篇 |
1992年 | 2874篇 |
1991年 | 2415篇 |
1990年 | 2070篇 |
1989年 | 2180篇 |
1988年 | 2122篇 |
1987年 | 1369篇 |
1986年 | 1398篇 |
1985年 | 966篇 |
1984年 | 1107篇 |
1983年 | 515篇 |
1982年 | 997篇 |
1981年 | 819篇 |
1980年 | 830篇 |
1979年 | 602篇 |
1978年 | 560篇 |
1977年 | 642篇 |
1976年 | 1053篇 |
1972年 | 532篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
A graph is called supereulerian if it has a spanning closed trail. Let G be a 2-edge-connected graph of order n such that each minimal edge cut SE(G) with |S|3 satisfies the property that each component of G−S has order at least (n−2)/5. We prove that either G is supereulerian or G belongs to one of two classes of exceptional graphs. Our results slightly improve earlier results of Catlin and Li. Furthermore, our main result implies the following strengthening of a theorem of Lai within the class of graphs with minimum degree δ4: If G is a 2-edge-connected graph of order n with δ(G)4 such that for every edge xyE(G) , we have max{d(x),d(y)}(n−2)/5−1, then either G is supereulerian or G belongs to one of two classes of exceptional graphs. We show that the condition δ(G)4 cannot be relaxed. 相似文献
123.
完全非线性偏微分方程解的Gevrey微局部正则性 总被引:1,自引:1,他引:0
本文中,我们首先简要回顾了Gevrey类中的仿微分运算,然后考察了相关的完全非线性偏微分方程的象征的一些性质。作为应用,我们得到解在椭圆点附近的Gevrey微局部正则性。 相似文献
124.
可变抽样区间的非参数控制图 总被引:1,自引:1,他引:0
最近几年一些学者研究了可变抽样区间的质量控制图。Amin等提出了可变抽样区间(VSI)的非参数控制图———符号 (Sign)统计量图〔1〕。本文在此基础上研究位置VSI符号控制图的制定方法 ,并设计离散VSI符号控制图。符号控制图的优点是对非正态总体亦可应用 ,并且不需要过程方差的信息。本文将所设计的VSI符号控制图同固定抽样区间 (FSI)的常规图作比较 ,并举实例说明符号控制图的应用 相似文献
125.
A. A. Vertiy S. P. Gavrilov I. V. Voynovskyy V. N. Stepanyuk Sunullah Ozbek 《International Journal of Infrared and Millimeter Waves》2002,23(10):1413-1444
In the present paper new results of modeling and experimental investigation on millimeter wave subsurface tomography are submitted. Tomographic algorithm is employed for imaging of subsurface objects in the case when conductivity of probed medium is not equal to zero. The possibilities and restrictions of this algorithm for image processing are shown both as a result of modeling and as a result of experiments. A new tomography setup allowing obtaining images of different inhomogeneities in dielectric media is considered. 相似文献
126.
127.
128.
Solitary waves and their bifurcations of KdV like equation with higher order nonlinearity 总被引:3,自引:1,他引:2
We investigate the KdV like equation with higher order nonlinearity ut + a(1 +bun)unux + uxxx = 0with n ≥ 1, a, b ∈ R and α≠ 0. The bifurcations and explicit expressions of solitary wave solutions for theequation are discussed by using the bifurcation method and qualitative theory of dynamical systems. Thebifurcation diagrams, existence and number of the solitary waves are given. 相似文献
129.
Guofen Yu Yuanci Gao Shenggang Liu Wenxiang Wang Jin Wu 《International Journal of Infrared and Millimeter Waves》2002,23(8):1261-1269
Analysis of the field distributions in a single biological cell under electromagnetic wave is given. With Debye approximation, the dielectric relaxation of each part of the cell, including the extracellular and cellular media, the cell membrane and the nuclear membrane, was taken into account. Making use of some typical parameters for a cell, the voltage across nuclear and cytoplasma membranes under electromagnetic waves are calculated up to millimeter wave frequency range. The calculated result indicates that it is unlikely to generate electroporation by present available millimeter wave sources. 相似文献
130.
Proton conductivity of phosphoric acid derivative of fullerene 总被引:1,自引:0,他引:1
The proton conductive property of methano [60] fullerene diphosphoric acid has been investigated under various humidity conditions at the temperature range between 15 and 45 °C. It shows proton conductivity as high as 10−2 S cm−1 at 25 °C under relative humidity of 95%. Thermal analyses including TG–DTA and thermal desorption mass spectroscopy (TDS) confirm that the compound is thermally stable up to 200 °C. Proton conduction of the compound depends very much on humidity or water content. The logarithmic conductivity at 25 °C is increased linearly with increasing relative humidity. The activation energy (Ea) estimated from the slope of log(σT) vs. 1/T is decreased from 1.08 to 0.52 eV, as the relative humidity is increased from 40% to 75%. The humidity dependence of conductivity is discussed in the light of the observed hydration isotherm. 相似文献