全文获取类型
收费全文 | 3621篇 |
免费 | 370篇 |
国内免费 | 176篇 |
专业分类
化学 | 331篇 |
晶体学 | 12篇 |
力学 | 174篇 |
综合类 | 58篇 |
数学 | 1229篇 |
物理学 | 745篇 |
无线电 | 1618篇 |
出版年
2024年 | 7篇 |
2023年 | 40篇 |
2022年 | 62篇 |
2021年 | 83篇 |
2020年 | 98篇 |
2019年 | 80篇 |
2018年 | 96篇 |
2017年 | 136篇 |
2016年 | 160篇 |
2015年 | 161篇 |
2014年 | 277篇 |
2013年 | 253篇 |
2012年 | 245篇 |
2011年 | 247篇 |
2010年 | 194篇 |
2009年 | 235篇 |
2008年 | 230篇 |
2007年 | 216篇 |
2006年 | 184篇 |
2005年 | 166篇 |
2004年 | 127篇 |
2003年 | 134篇 |
2002年 | 112篇 |
2001年 | 97篇 |
2000年 | 99篇 |
1999年 | 87篇 |
1998年 | 71篇 |
1997年 | 49篇 |
1996年 | 35篇 |
1995年 | 25篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有4167条查询结果,搜索用时 15 毫秒
81.
82.
83.
Control of the 1D self‐assembly pattern of colloidal quantum dots (QDs) on PbSO4 nanoribbon (NRb) templates is achieved. The internal structure of the NRbs is investigated by X‐ray diffraction, revealing the isotropic packing of the PbSO4 nanoclusters in the NRbs. Colloidal QDs in a chloroform/hexane mixture are adsorbed onto the region close to the edges of the NRbs and form a 1D assembly of straight single line or double lines by controlling the amount of OAm. This is the first demonstration of a densely packed 1D self‐assembly of colloidal QDs with a straight line pattern without the use of any molecular bridge or adhesive. Atomic force microscopy measurements of the NRbs show depressions in the phase profile along the width of the NRbs, corresponding to the position of the 1D QD chain. The amount of adsorbed QDs on the NRbs in solution decreases as the addition of OAm increases, suggesting that additional OAm prevents interaction between the QDs and NRbs but facilitates the uniform adsorption of the 1D assembly. The low‐dimensional self‐assembly of colloidal QDs in this study opens up the possibility for the creation of anisotropically assembled QD superstructures. 相似文献
84.
In this article we consider linear codes coming from skew-symmetric determinantal varieties, which are defined by the vanishing of minors of a certain fixed size in the space of skew-symmetric matrices. In odd characteristic, the minimum distances of these codes are determined and a recursive formula for the weight of a general codeword in these codes is given. 相似文献
85.
Benjamin Arras Ehsan Azmoodeh Guillaume Poly Yvik Swan 《Stochastic Processes and their Applications》2019,129(7):2341-2375
We provide a bound on a distance between finitely supported elements and general elements of the unit sphere of . We use this bound to estimate the Wasserstein-2 distance between random variables represented by linear combinations of independent random variables. Our results are expressed in terms of a discrepancy measure related to Nourdin–Peccati’s Malliavin–Stein method. The main application is towards the computation of quantitative rates of convergence to elements of the second Wiener chaos. In particular, we explicit these rates for non-central asymptotic of sequences of quadratic forms and the behavior of the generalized Rosenblatt process at extreme critical exponent. 相似文献
86.
Cannibalization is a major concern for a firm when designing a product line. In addition, external options from outside the firm’s product line may also play a significant role. In this paper, we investigate the impact of external options, represented by reservation utility, on product line design and introduction sequence. We find that: (a) heterogeneous reservation utility defines the relative attractiveness of segments and corresponding product line; (b) reservation utility makes it more favorable to introduce products sequentially rather than simultaneously; (c) aggregating segments is an effective way to mitigate cannibalization when it becomes too difficult to manage with different values of reservation utility across multiple segments; and (d) introducing products in a non-monotone order of quality can improve profit from simultaneous introduction when the value of reservation utility of a middle segment is particularly high. 相似文献
87.
Dependency distance, measured by the linear distance between two syntactically related words in a sentence, is generally held as an important index of memory burden and an indicator of syntactic difficulty. Since this constraint of memory is common for all human beings, there may well be a universal preference for dependency distance minimization (DDM) for the sake of reducing memory burden. This human-driven language universal is supported by big data analyses of various corpora that consistently report shorter overall dependency distance in natural languages than in artificial random languages and long-tailed distributions featuring a majority of short dependencies and a minority of long ones. Human languages, as complex systems, seem to have evolved to come up with diverse syntactic patterns under the universal pressure for dependency distance minimization. However, there always exist a small number of long-distance dependencies in natural languages, which may reflect some other biological or functional constraints. Language system may adapt itself to these sporadic long-distance dependencies. It is these universal constraints that have shaped such a rich diversity of syntactic patterns in human languages. 相似文献
88.
I. Babushkin 《Physics letters. A》2010,374(6):896-900
We study deviation from the Poissonian statistics of the frequency spacing distribution, appearing due to coupling of polarizational and transverse degrees of freedom in a perfectly square vertical cavity surface emitting laser. The deviation can be controlled by strength of the intracavity anisotropy and its alignment to the device boundaries. 相似文献
89.
两点源诱偏是对抗反辐射导弹(ARM)的一种有效的手段。首先采用数学方法研究了两点源诱偏反辐射导弹的原理,讨论了两点源诱偏作用下被动雷达导引头的瞄准方向,给出了两点源诱骗反辐射导弹的脱靶距离模型和案例分析,为研究靶场诱偏系统的试验方法和使用原则奠定了基础。 相似文献
90.