全文获取类型
收费全文 | 2451篇 |
免费 | 168篇 |
国内免费 | 155篇 |
专业分类
化学 | 358篇 |
晶体学 | 17篇 |
力学 | 74篇 |
综合类 | 7篇 |
数学 | 840篇 |
物理学 | 1478篇 |
出版年
2023年 | 10篇 |
2022年 | 12篇 |
2021年 | 35篇 |
2020年 | 19篇 |
2019年 | 36篇 |
2018年 | 25篇 |
2017年 | 33篇 |
2016年 | 29篇 |
2015年 | 31篇 |
2014年 | 43篇 |
2013年 | 57篇 |
2012年 | 58篇 |
2011年 | 149篇 |
2010年 | 155篇 |
2009年 | 331篇 |
2008年 | 309篇 |
2007年 | 247篇 |
2006年 | 236篇 |
2005年 | 142篇 |
2004年 | 78篇 |
2003年 | 102篇 |
2002年 | 109篇 |
2001年 | 77篇 |
2000年 | 79篇 |
1999年 | 82篇 |
1998年 | 58篇 |
1997年 | 13篇 |
1996年 | 26篇 |
1995年 | 22篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 9篇 |
排序方式: 共有2774条查询结果,搜索用时 15 毫秒
961.
Emre Kolotoğlu 《组合设计杂志》2013,21(7):280-302
The problem of the existence of a decomposition of the complete graph ey:10638539:media:jcd21340:jcd21340-math-0001" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/d6fc7852-26a2-4447-ab7b-0388b9650a52/jcd21340-math-0001.png"> into disjoint copies of ey:10638539:media:jcd21340:jcd21340-math-0002" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/9074b2e7-9cfc-4c66-90e8-027b5805086e/jcd21340-math-0002.png"> has been solved for all admissible orders n, except for 27, 36, 54, 64, 72, 81, 90, 135, 144, 162, 216, and 234. In this paper, I eliminate 4 of these 12 unresolved orders. Let Γ be a ey:10638539:media:jcd21340:jcd21340-math-0003" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/a61e6418-7e5a-4dea-b2a8-2c025bb1ed46/jcd21340-math-0003.png">‐design. I show that ey:10638539:media:jcd21340:jcd21340-math-0004" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/a8ed2ff0-bd29-4fed-a250-632f8aef179c/jcd21340-math-0004.png"> divides 2k3 for some ey:10638539:media:jcd21340:jcd21340-math-0005" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/f4ddfec9-7db3-4ab7-bd0e-582b95093971/jcd21340-math-0005.png"> and that ey:10638539:media:jcd21340:jcd21340-math-0006" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/f252b987-f05c-4c1e-a031-be3ffe4227ea/jcd21340-math-0006.png">. I construct ey:10638539:media:jcd21340:jcd21340-math-0007" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/7d6ffd14-136b-4c3c-8887-df2a6684e70a/jcd21340-math-0007.png">‐designs by prescribing ey:10638539:media:jcd21340:jcd21340-math-0008" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/1aee69fe-af32-4924-8ccb-5a574f4f4c71/jcd21340-math-0008.png"> as an automorphism group, and show that up to isomorphism there are exactly 24 ey:10638539:media:jcd21340:jcd21340-math-0009" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/842957cf-160d-45ff-a840-dd2cf8ad6899/jcd21340-math-0009.png">‐designs with ey:10638539:media:jcd21340:jcd21340-math-0010" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/173d172c-ba9c-4ca9-8148-26036172426c/jcd21340-math-0010.png"> as an automorphism group. Moreover, I show that the full automorphism group of each of these designs is indeed ey:10638539:media:jcd21340:jcd21340-math-0011" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/aa34ce76-7813-424d-9b4d-23c6a28303df/jcd21340-math-0011.png">. Finally, the existence of ey:10638539:media:jcd21340:jcd21340-math-0012" class="section_image" src="https://wol-prod-cdn.literatumonline.com/cms/attachment/a9993ac3-c5ea-4ee9-9de1-57fc45570ff6/jcd21340-math-0012.png">‐designs of orders 135, 162, and 216 follows immediately by the recursive constructions given by G. Ge and A. C. H. Ling, SIAM J Discrete Math 21(4) (2007), 851–864. 相似文献
962.
The effect of bias voltage on electron tunneling across a junction with a ferroelectric-ferromagnetic composite barrier is investigated theoretically. Because of the inversion symmetry breaking of the spontaneous ferroelectric polarization, bias voltage dependence of the electron tunneling shows significant differences between the positive bias and the negative one. The differences of spin filtering or tunnel magnetoresistance increase with the increasing absolute value of bias voltage. Such direction preferred electron tunneling is found intimately related with the unusual asymmetry of the electrical potential profile in two-phase composite barrier and provides a unique change to realize rectifying functions in spintronics. 相似文献
963.
Let P = E G be a Zappa-Szp product of a semilattice E with an identity and a group G. In this paper, we first introduce the concept of congruence pairs for P , and then prove that every congruence on P can be described by such a congruence pair. In fact the congruence lattice on P is lattice-isomorphic to the set of all congruence pairs for P . Finally,we characterize group congruences on P . 相似文献
964.
Study of (e, 2e) process on potassium at 6 eV-60 eV above threshold in a second-order Born approximation 下载免费PDF全文
The standard distorted wave Born approximation(DWBA) method has been extended to second-order Born amplitude in order to describe the multiple interactions between the projectile and the atomic target.Second-order DWBA calculations have been preformed to investigate the triple differential cross sections(TDCS) of coplanar doubly symmetric(e,2e) collisions for the alkali target potassium at excess energies of 6 eV-60 eV.Compared with the previous first-order DWBA calculations,the present theoretical model improves the degree of agreement with experiments,especially for the backward scattering angle region of TDCS.This indicates that the present second-order Born term is capable of giving a reasonable correction to the DWBA model in studying coplanar symmetric(e,2e) problems in low and intermediate energy ranges. 相似文献
965.
Bipan Hazarika 《Applied Mathematics Letters》2012,25(3):466-470
In this article, we introduce the concept of lacunary <em>Iem>-convergent sequence of fuzzy real numbers and study some basic properties. 相似文献
966.
Ekrem Savas 《Applied Mathematics Letters》2012,25(4):733-738
Following the line of recent works of Das et al. (2011) [15] and Savas and Das (2011) [19] we apply the notion of ideals to strong matrix summability, and in this note, we introduce the notion of strong <em>Aem><em>Iem>-summability with respect to an Orlicz function. We make certain investigations on the classes of sequences arising out of this new summability method. 相似文献
967.
文中采用氨原子的三种近似波函数,计算了入射电子能量为5599 eV时,敲出电子共面等能分享几何安排下,氦原子双电离He(e,3e)反应全微分截面.结果表明三种波函数的理论计算结果,在误差范围内都与实验数据基本吻合,其中采用Pluvinage波函数所得到的理论数据更接近实验数据. 相似文献
968.
In this study the adsorption geometry of aspirin molecule on a hydroxylated (0 0 1) α-quartz surface has been investigated using DFT calculations. The optimized adsorption geometry indicates that both, adsorbed molecule and substrate are strongly deformed. Strong hydrogen bonding between aspirin and surface hydroxyls, leads to the breaking of the original hydroxyl–hydroxyl hydrogen bonds (Hydrogenbridges) on the surface. In this case new hydrogen bonds on the hydroxylated (0 0 1) α-quartz surface appear which significantly differ from those at the clean surface. The 1.11 eV adsorption energy reveals that the interaction of aspirin with α-quartz is an exothermic chemical interaction. 相似文献
969.
Tianyu Sun Jianpeng Wang Jianyong Ma Yunxia Jin Jianda Shao 《Optics Communications》2009,282(4):451-24197
In this paper, we design resonant reflection grating filters employing the second diffracted orders as the leaky modes, then analyze the bandwidth of the reflection peak and the electric field distributions inside the waveguide under resonance. The numeric calculation confirms that ultra-narrow resonant reflection peaks can be observed in these structures. At the same time, strong electric field enhancement appears under resonance. It provides a new approach to diversify the resonant reflection filters and may open a new way to the realization of ultra-narrow bandwidth filters. 相似文献
970.