全文获取类型
收费全文 | 14871篇 |
免费 | 3609篇 |
国内免费 | 1872篇 |
专业分类
化学 | 8534篇 |
晶体学 | 259篇 |
力学 | 1093篇 |
综合类 | 123篇 |
数学 | 1187篇 |
物理学 | 9156篇 |
出版年
2024年 | 27篇 |
2023年 | 174篇 |
2022年 | 475篇 |
2021年 | 535篇 |
2020年 | 740篇 |
2019年 | 615篇 |
2018年 | 615篇 |
2017年 | 681篇 |
2016年 | 770篇 |
2015年 | 663篇 |
2014年 | 827篇 |
2013年 | 1286篇 |
2012年 | 1090篇 |
2011年 | 1138篇 |
2010年 | 975篇 |
2009年 | 1000篇 |
2008年 | 945篇 |
2007年 | 1008篇 |
2006年 | 901篇 |
2005年 | 793篇 |
2004年 | 712篇 |
2003年 | 650篇 |
2002年 | 678篇 |
2001年 | 508篇 |
2000年 | 432篇 |
1999年 | 317篇 |
1998年 | 303篇 |
1997年 | 223篇 |
1996年 | 203篇 |
1995年 | 162篇 |
1994年 | 142篇 |
1993年 | 97篇 |
1992年 | 109篇 |
1991年 | 81篇 |
1990年 | 60篇 |
1989年 | 61篇 |
1988年 | 48篇 |
1987年 | 34篇 |
1986年 | 43篇 |
1985年 | 44篇 |
1984年 | 43篇 |
1983年 | 17篇 |
1982年 | 31篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 16篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Summary A system for capillary electrophoresis combined with enzymatic assay has been evaluated for the two enzymes glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Instrumentation included a post-column reactor coupled to the separation capillary by a liquid junction. A technique for generating a substrate solution flow into the reactor by utilizing two high voltage supplies is proposed. This method offers a high degree of freedom in optimizing the separation and enzymatic reaction conditions individually. Possibilities for improving the enzymatic assay sensitivity were also examined. 相似文献
22.
Regis Guyonnet 《Journal of statistical physics》1991,65(1-2):269-289
The NMR properties of nuclei linked to long linear polymer molecules are sensitive to the influence of hard walls. In this context, the residual energy of tensorial spin-spin interactions is calculated using a path integral approach. Several thermodynamic quantities of the polymer system (free energy, equation of state,...) are also expressed, taking chain stiffness effects and the presence of two repulsive walls into consideration. 相似文献
23.
24.
A. B. Mazo 《Fluid Dynamics》2002,37(6):913-918
Plane ideal incompressible flow in a rectangular channel partitioned by a thin permeable barrier (lattice) is considered. In flowing through the lattice the stream suddenly (jumpwise) changes direction and loses energy. The flow is assumed to be vortical; the vorticity is discontinuous on the lattice. A mathematical formulation of the problem for the stream function is proposed in the form of a nonlinear elliptic equation with coefficients discontinuous on the lattice line. A numerical solution is constructed using the finite-element iteration method. The results of the numerical simulation show how the flow velocity profile in the channel can be controlled by means of permeable barriers. 相似文献
25.
We have obtained expressions of the accelerating effect in Kerr-Newman Kasuya field. These expressionsinclude four parameters: mass m, angular momentum a, electric charge q, and magnetic charge φ. Furthermore we studyits special case (vi = 0). We get the following conclusion. In the gravitation field of souse mass with electric charge qand magnetic charge b, the acceleration of test particle has not only radial component but also transverse component.When θ = 0, the acceleration is minimum, and when θ = π/2, the acceleration is maximum. Furthermore, we discussthe effects of electric charge q and magnetic charge φ respectively. 相似文献
26.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
27.
NMR screening techniques in drug discovery and drug design 总被引:7,自引:0,他引:7
Brian J. Stockman Claudio Dalvit 《Progress in Nuclear Magnetic Resonance Spectroscopy》2002,41(3-4):187-231
28.
在北京同步辐射装置(BSRF)1W1B光束线和XAFS实验站上国内首次建立了硬X射线波段的磁圆二色实验(XMCD)方法. 以单晶金刚石作为相位延迟片, 在透射劳埃(Laue)模式下, 利用衍射双折射效应, 将入射的单色线偏振光转变为相应的左旋和右旋圆偏振光, 测量磁化样品对左旋和右旋圆偏振光吸收的差异, 获得了XMCD信号. 本实验使用透射方法测量了Pt-Fe合金Pt L2,3边的XMCD, 获得了XMCD信号. XMCD实验方法的建立, 为研究磁性材料尤其是磁性薄膜材料的电子结构和磁结构提供了实验基础. 相似文献
29.
在聚合物基体中掺入少量的层状硅酸盐所制备的聚合物/粘土纳米复合材料,其阻隔性能明显地优于纯聚合物及其传统的复合材料。实验及分析结果表明,聚合物/粘土纳米复合材料的微观结构和阻隔性能主要受控于粘土剥离后的径厚比.一简单的重整化群模型被用来评估粘土几何因素(诸如径厚比、取向、剥离程度等)对聚合物/粘土纳米复合材料阻隔性能的影响,所得到的逾渗阈值及最佳粘土含量与实验结果吻合。 相似文献
30.