全文获取类型
收费全文 | 416篇 |
免费 | 62篇 |
国内免费 | 27篇 |
专业分类
化学 | 11篇 |
力学 | 37篇 |
综合类 | 7篇 |
数学 | 226篇 |
物理学 | 224篇 |
出版年
2023年 | 2篇 |
2022年 | 18篇 |
2021年 | 27篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 9篇 |
2014年 | 25篇 |
2013年 | 29篇 |
2012年 | 21篇 |
2011年 | 45篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有505条查询结果,搜索用时 31 毫秒
171.
Tamiya N Yagi T 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2011,87(3):41-52
Erabutoxins a and b are neurotoxins isolated from venom of a sea snake Laticauda semifasciata (erabu-umihebi). Amino acid sequences of the toxins indicated that the toxins are members of a superfamily consisting of short and long neurotoxins and cytotoxins found in sea snakes and terrestrial snakes. The short neurotoxins to which erabutoxins belong act by blocking the nicotinic acetylcholine receptor on the post synaptic membrane in a manner similar to that of curare. X-ray crystallography and NMR analyses showed that the toxins have a three-finger structure, in which three fingers made of three loops emerging from a dense core make a gently concave surface of the protein. The sequence comparison and the location of essential residues on the protein suggested the mechanism of binding of the toxin to the acetylcholine receptor. Classification of snakes by means of sequence comparison and that based on different morphological features were inconsistent, which led the authors to propose a hypothesis "Evolution without divergence." 相似文献
172.
173.
Fayez Abu-Ajamieh 《中国物理C(英文版)》2022,46(1):013101-013101-12
We adopt a bottom-up Effective Field Theory(EFT)approach to derive a model-independent Veltman condition to cancel out the quadratic divergences in the Higgs mass.We show using the equivalence theorem that all the deviations in the Higgs couplings to the W and Z from the SM predictions should vanish.We argue based on tree-level unitarity that any new physics that naturally cancels out the quadratic divergences should be ≤19 TeV.We show that the level of fine-tuning required is unless the O(0:1%-1%) UV sector has a symmetry that forces the satisfaction of the model-independent Veltman condition,in which case all fine-tuning is eliminated.We also conjecture that,if no new physics that couples to the Higgs is observed up to~19 TeV,or if the Higgs couplings to the SM particles conform to the SM predictions,then the Higgs either does not couple to any UV sector or is fine-tuned. 相似文献
174.
S. Chakraborty 《International Journal of Mathematical Education in Science & Technology》2013,44(3):407-412
In the simple one-dimensional random walk setup, a path is described as follows. Toss a coin. If the result is head, score +1 and move one step forward; otherwise score ?1 and move one step backward. One is interested to know the position after a given number of steps. In this paper, once again a coin-tossing experiment is carried out. But this time, going by the philosophy of Bhanu et al. if score ?2, the result is head, otherwise score +1. The situation studied is the case that one decides to stop at the score of a given number n. Unlike their earlier case, the paper considers a general coin with probability of head equal to θ for 0?θ?1 and get more general results. It is shown that all these general results reduce to those obtained by Bhanu et al. when θ?=?1/2. 相似文献
175.
Steen Markvorsen 《International Journal of Mathematical Education in Science & Technology》2013,44(7):879-888
Using only fairly simple and elementary considerations–essentially from first year undergraduate mathematics–we show how the classical Stokes' theorem for any given surface and vector field in ?3 follows from an application of Gauss' divergence theorem to a suitable modification of the vector field in a tubular shell around the given surface. The two stated classical theorems are (like the fundamental theorem of calculus) nothing but shadows of the general version of Stokes' theorem for differential forms on manifolds. However, the main point in the present article is first, that this latter fact usually does not get within reach for students in first year calculus courses and second, that calculus textbooks in general only just hint at the correspondence alluded to above. Our proof that Stokes' theorem follows from Gauss' divergence theorem goes via a well-known and often used exercise, which simply relates the concepts of divergence and curl on the local differential level. The rest of this article uses only integration in 1, 2 and 3 variables together with a ‘fattening’ technique for surfaces and the inverse function theorem. 相似文献
176.
177.
本文研究黎曼流形上散度型算子的低阶特征值.利用Rayleigh-Ritz不等式,得到了这种算子的低阶特征值所满足的一个不等式.而且,对于拉普拉斯算子的低阶特征值,本文的结果是最佳的. 相似文献
178.
《Journal of computational and graphical statistics》2013,22(3):592-614
This article shows how to smoothly “monotonize” standard kernel estimators of hazard rate, using bootstrap weights. Our method takes a variety of forms, depending on choice of kernel estimator and on the distance function used to define a certain constrained optimization problem. We confine attention to a particularly simple kernel approach and explore a range of distance functions. It is straightforward to reduce “quadratic” inequality constraints to “linear” equality constraints, and so our method may be implemented using little more than conventional Newton–Raphson iteration. Thus, the necessary computational techniques are very familiar to statisticians. We show both numerically and theoretically that monotonicity, in either direction, can generally be imposed on a kernel hazard rate estimator regardless of the monotonicity or otherwise of the true hazard rate. The case of censored data is easily accommodated. Our methods have straightforward extension to the problem of testing for monotonicity of hazard rate, where the distance function plays the role of a test statistic. 相似文献
179.
文章在已知实数项级数收敛及区间数列收敛概念的基础上,具体阐述了区间数项级数的定义及其性质.然后,给出了几个关于正区间数项级数敛散性判断定理与推论.最后,关于一般项区间数级数敛散性的判别作了讨论. 相似文献
180.