全文获取类型
收费全文 | 2594篇 |
免费 | 73篇 |
国内免费 | 19篇 |
专业分类
化学 | 1894篇 |
晶体学 | 26篇 |
力学 | 26篇 |
数学 | 257篇 |
物理学 | 483篇 |
出版年
2023年 | 18篇 |
2021年 | 28篇 |
2020年 | 32篇 |
2019年 | 35篇 |
2018年 | 22篇 |
2017年 | 20篇 |
2016年 | 28篇 |
2015年 | 48篇 |
2014年 | 56篇 |
2013年 | 146篇 |
2012年 | 109篇 |
2011年 | 144篇 |
2010年 | 82篇 |
2009年 | 72篇 |
2008年 | 142篇 |
2007年 | 153篇 |
2006年 | 134篇 |
2005年 | 149篇 |
2004年 | 144篇 |
2003年 | 127篇 |
2002年 | 116篇 |
2001年 | 64篇 |
2000年 | 55篇 |
1999年 | 48篇 |
1998年 | 42篇 |
1997年 | 31篇 |
1996年 | 30篇 |
1995年 | 21篇 |
1994年 | 21篇 |
1993年 | 30篇 |
1992年 | 35篇 |
1991年 | 32篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 22篇 |
1985年 | 32篇 |
1984年 | 38篇 |
1983年 | 23篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1979年 | 33篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1975年 | 14篇 |
1974年 | 35篇 |
1973年 | 18篇 |
排序方式: 共有2686条查询结果,搜索用时 0 毫秒
1.
2.
Masaaki Sugihara 《Numerische Mathematik》1997,75(3):379-395
Summary. In the light of the functional analysis theory we establish the optimality of the double exponential formula. The argument
consists of the following three ingredients: (1) introduction of a number of spaces of functions analytic in a strip region
about the real axis, each space being characterized by the decay rate of their elements (functions) in the neighborhood of
the infinity; (2) proof of the (near-) optimality of the trapezoidal formula in each space introduced in (1) by showing the
(near-) equality between an upper estimate for the error norm of the trapezoidal formula and a lower estimate for the minimum
error norm of quadratures; (3) nonexistence theorem for the spaces, the characterizing decay rate of which is more rapid than
the double exponential.
Received September 15, 1995 / Accepted December 14, 1995 相似文献
3.
4.
5.
N Murakami T Morimoto H Imamura T Ueda S Nagai J Sakakibara N Yamada 《Chemical & pharmaceutical bulletin》1991,39(9):2277-2281
Seven new monogalactosyl diacylglycerols (1-7) and six new digalactosyl diacylglycerols (11-16) were isolated from an axenically cultured cyanobacterium, P. tenue. Their structures were elucidated on the basis of physicochemical evidence and the results of enzymatic hydrolysis using a lipase (from Rhizopus arrhizus). Comparison of antialgal activity for P. tenue between monogalactosyl diacylglycerols (1-8) and digalactosyl diacylglycerols (11-19) revealed that the former showed more potent activity than the latter. 相似文献
6.
Shigeyuki Toki Igors Sics Benjamin S. Hsiao Syozo Murakami Masatoshi Tosaka Sirilux Poompradub Shinzo Kohjiya Yuko Ikeda 《Journal of Polymer Science.Polymer Physics》2004,42(6):956-964
The molecular orientation and strain‐induced crystallization of synthetic rubbers—polyisoprene rubber, polybutadiene rubber, and butyl rubber [poly(isobutylene isoprene)]—during uniaxial deformation were studied with in situ synchrotron wide‐angle X‐ray diffraction. The high intensity of the synchrotron X‐rays and the new data analysis method made it possible to estimate the mass fractions of the strain‐induced crystals and amorphous chain segments in both the oriented and unoriented states. Contrary to the conventional concept, the majority of the molecules (50–75%) remained in an unoriented amorphous state at high strains. Each synthetic rubber showed a different behavior of strain‐induced crystallization and molecular orientation during extension and retraction. Our results confirmed the occurence of strain‐induced networks in the synthetic rubbers due to the inhomogeneity of the crosslink distribution. The strain‐induced networks containing microfibrillar crystals and oriented amorphous tie chains were responsible for the ultimate mechanical properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 956–964, 2004 相似文献
7.
Takayuki Nakai Yoshiko Murakami Yoshiaki Sasaki Isamu Fujiwara Shoji Tagashira 《Analytical sciences》2004,20(1):235-237
The extraction and separation of copper(II), zinc(II), cobalt(II), and cadmium(II) were investigated. Both copper(II) and zinc(II) formed ammine-complexes, while cadmium(II) and cobalt(II) formed hydroxide precipitates in an ammonia medium. By the addition of sodium dodecylsulfate (SDS), a copper(II) complex formed an ion-pair (copper-ammine-DS), which was extracted into the SDS phase. However, a zinc(II) complex did not form an ion-pair, and was soluble in water. Copper(II) ion was recovered by stripping (back-extraction) after the addition of hydrochloric acid. This method was applied to the separation of copper(II) in a brass alloy. 相似文献
8.
9.
In this paper, we provide numerical means to compute the quasi-stationary (QS) distributions inM/GI/1/K queues with state-dependent arrivals andGI/M/1/K queues with state-dependent services. These queues are described as finite quasi-birth-death processes by approximating the general distributions in terms of phase-type distributions. Then, we reduce the problem of obtaining the QS distribution to determining the Perron-Frobenius eigenvalue of some Hessenberg matrix. Based on these arguments, we develop a numerical algorithm to compute the QS distributions. The doubly-limiting conditional distribution is also obtained by following this approach. Since the results obtained are free of phase-type representations, they are applicable for general distributions. Finally, numerical examples are given to demonstrate the power of our method. 相似文献
10.
Recently extremal double circulant self-dual codes have been classified for lengths n ≤ 62. In this paper, a complete classification
of extremal double circulant self-dual codes of lengths 64 to 72 is presented. Almost all of the extremal double circulant
singly-even codes given have weight enumerators for which extremal codes were not previously known to exist. 相似文献