全文获取类型
收费全文 | 149900篇 |
免费 | 25862篇 |
国内免费 | 13037篇 |
专业分类
化学 | 93934篇 |
晶体学 | 1171篇 |
力学 | 6200篇 |
综合类 | 702篇 |
数学 | 12594篇 |
物理学 | 34429篇 |
无线电 | 39769篇 |
出版年
2024年 | 466篇 |
2023年 | 2673篇 |
2022年 | 3495篇 |
2021年 | 4381篇 |
2020年 | 5504篇 |
2019年 | 6508篇 |
2018年 | 4636篇 |
2017年 | 4205篇 |
2016年 | 7983篇 |
2015年 | 8651篇 |
2014年 | 9500篇 |
2013年 | 11853篇 |
2012年 | 12078篇 |
2011年 | 11468篇 |
2010年 | 9558篇 |
2009年 | 9641篇 |
2008年 | 9493篇 |
2007年 | 8174篇 |
2006年 | 7631篇 |
2005年 | 6887篇 |
2004年 | 5433篇 |
2003年 | 4554篇 |
2002年 | 5020篇 |
2001年 | 3901篇 |
2000年 | 3783篇 |
1999年 | 3039篇 |
1998年 | 2341篇 |
1997年 | 1996篇 |
1996年 | 1977篇 |
1995年 | 1742篇 |
1994年 | 1544篇 |
1993年 | 1406篇 |
1992年 | 1216篇 |
1991年 | 1029篇 |
1990年 | 834篇 |
1989年 | 681篇 |
1988年 | 565篇 |
1987年 | 443篇 |
1986年 | 397篇 |
1985年 | 402篇 |
1984年 | 277篇 |
1983年 | 228篇 |
1982年 | 203篇 |
1981年 | 142篇 |
1980年 | 102篇 |
1979年 | 82篇 |
1978年 | 77篇 |
1977年 | 71篇 |
1975年 | 70篇 |
1973年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
162.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献
163.
Compact, time‐harmonic, acoustic sources produce waves that decay too slowly to be square‐integrable on a line away from the sources. We introduce an inner product, arising directly from Green's second theorem, to form a Hilbert space of these waves and present examples of its computation.1 © 2005 Wiley Periodicals, Inc. 相似文献
164.
A novel finger‐sensing nanocomposite with remarkable and reversible piezoresistivity is successfully fabricated by dispersing homogeneously conductive graphite nanosheets (GNs) in a silicone rubber (SR) matrix. Because of the high aspect ratio of the graphite nanosheets, the nanocomposite displays a very low percolation threshold. The SR/GN nanocomposite with a volume fraction of conductive nanosheets closest to that for the percolation threshold presents a sharp positive‐pressure coefficient effect of the resistivity under very low pressure, namely, in the finger‐pressure range (0.3–0.7 MPa), whereby the abrupt transition could be attributed to compressive‐stress‐induced deformation of the conducting network. The super‐sensitive piezoresistive behavior of the nanocomposite is accounted for by an extension of the tunneling conduction theory which provides a good approximation to the piezoresistive effect. 相似文献
165.
Junhua Chen 《Journal of organometallic chemistry》2006,691(3):470-474
Four novel hexadentate imidazolium salts were synthesized from hexakis(bromomethyl)benzene and 1-substituted imidazole. The arylation of aldehydes with arylboronic acids was effected conveniently and in high yields by a catalyst system generated in situ from these hexadentate imidazolium salts, [Rh(COD)Cl]2 and a base. 相似文献
166.
随着电容测量技术的迅速发展,电容传感器在非电量测量和自动检测中得到广泛应用,但它在使用过程中也存在一些问题,针对在使用电容传感器过程中存在的几个问题,从电容传感器的原理和工作过程两个方面进行了讨论,并提出行之有效的处理方法。 相似文献
167.
An experimental study of an optical burst switching network based on wavelength-selective optical switches 总被引:1,自引:0,他引:1
Li Xinwan Chen Jianping Wu Guiling Wang Hui Ye Ailun 《Communications Magazine, IEEE》2005,43(5):S3-10
In this article we report the system structure and test results of an experimental optical burst switching network with three edge router's and one core node. Wavelength-selective switches developed for this system and their characteristics are depicted. The implementation and performance of our new scheme for the just-in-time protocol are described. We also report experimental results of FTP and VOD services on this system. Some parameters, including traffic rate, average burst data length, and assembly time, are studied. 相似文献
168.
The inhomogeneous Dirichlet problems concerning divergence form elliptic equations are studied. Optimal regularity requirements on the coefficients and domains for the W1,p theory, 1 < p < ∞, are obtained. The principal coefficients are supposed to be in the John‐Nirenberg space with small BMO seminorms. The domain is a Reifenberg domain. These conditions for the W1,p theory not only weaken the requirements on the coefficients but also lead to a more general geometric condition on the domains. In fact, these domains might have fractal dimensions. © 2004 Wiley Periodicals, Inc. 相似文献
169.
物理模型教学与创新能力的培养 总被引:1,自引:0,他引:1
现代教学以能力培养为重点.学生获得研究问题、探索问题的能力是十分重要的,物理模型的教学过程对培养学生研究问题、探索问题、发展创造思维、培养辩证唯物主义思想方法都极为有利,因此,必须重视物理模型教学. 相似文献
170.
On effective offloading services for resource-constrained mobile devices running heavier mobile internet applications 总被引:1,自引:0,他引:1
Kun Yang Shumao Ou Hsiao-Hwa Chen 《Communications Magazine, IEEE》2008,46(1):56-63
Rapid advances in wireless mobile network technologies and mobile handsets (MHs) facilitate ubiquitous infrastructure that can support a range of mobile services and applications in addition to conventional mobile Internet access. One recent trend is to effectively run desktop PC-oriented heavier applications on MHs. However, due to their miniature, portable size, MHs are resource-constrained and therefore, running these applications directly on an MH is not satisfactory given a user's expectations. To cope with this problem, this article proposes a novel offloading service that can seamlessly offload some of the tasks of a mobile application from an MH to nearby, resource-rich PCs (called surrogates). The system architecture and key components of the proposed offloading service are presented, prototyped, and evaluated. The results of experiments and simulations have demonstrated the effectiveness and efficiency of this offloading service for mobile applications. 相似文献