全文获取类型
收费全文 | 51964篇 |
免费 | 2427篇 |
国内免费 | 4787篇 |
专业分类
化学 | 30265篇 |
晶体学 | 1321篇 |
力学 | 657篇 |
综合类 | 261篇 |
数学 | 18071篇 |
物理学 | 8603篇 |
出版年
2023年 | 345篇 |
2022年 | 1064篇 |
2021年 | 992篇 |
2020年 | 900篇 |
2019年 | 1156篇 |
2018年 | 1001篇 |
2017年 | 1045篇 |
2016年 | 1138篇 |
2015年 | 1215篇 |
2014年 | 1801篇 |
2013年 | 3896篇 |
2012年 | 2314篇 |
2011年 | 3513篇 |
2010年 | 3032篇 |
2009年 | 3370篇 |
2008年 | 3526篇 |
2007年 | 3452篇 |
2006年 | 2940篇 |
2005年 | 2606篇 |
2004年 | 2400篇 |
2003年 | 2015篇 |
2002年 | 2076篇 |
2001年 | 1359篇 |
2000年 | 1364篇 |
1999年 | 1131篇 |
1998年 | 1104篇 |
1997年 | 884篇 |
1996年 | 830篇 |
1995年 | 808篇 |
1994年 | 752篇 |
1993年 | 632篇 |
1992年 | 614篇 |
1991年 | 450篇 |
1990年 | 372篇 |
1989年 | 398篇 |
1988年 | 293篇 |
1987年 | 253篇 |
1986年 | 187篇 |
1985年 | 272篇 |
1984年 | 241篇 |
1983年 | 122篇 |
1982年 | 159篇 |
1981年 | 211篇 |
1980年 | 184篇 |
1979年 | 124篇 |
1978年 | 150篇 |
1977年 | 124篇 |
1976年 | 106篇 |
1975年 | 57篇 |
1974年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Peter Naur 《BIT Numerical Mathematics》1986,26(2):175-187
The questions raised by A. M. Turing in his paper on thought and machines are discussed. Human thought is considered in turn as a concept of normal language usage, as a basic concept of psychology, and as the basis of intellectual activity. It is concluded that neither of these notions of thought identifies something specific that a human being can or cannot do. The imitation game proposed by Turing for deciding whether a machine can think is found to result from an arbitrary empoverishment of the channel of communication between the interrogator and the item under investigation. Turing's notions of thinking are shown to lead to logical difficulties. An alternative view of consciousness, that would place it beyond the reach of any finite test, is finally discussed. 相似文献
62.
Mass distributions of fragments in the low-energy fission of nuclei from 187Ir to 213At have been analysed. This analysis has shown that shell effects in symmetric-mode fragment mass yields from the fission of pre-actinide nuclei could be described if one assumes the existence of two strongly deformed neutron shells in the arising fragments with neutron numbers N1 ≈ 52 and N2 ≈ 68. A new method has been proposed for quantitatively describing the mass distributions of the symmetric fission mode for pre-actinides with A ≈ 180–220. 相似文献
63.
J. Schropp 《Numerische Mathematik》1997,78(1):87-101
Summary. We use the qualitative properties of the solution flow of the gradient equation to compute a local minimum of a real-valued function . Under the regularity assumption of all equilibria we show a convergence result for bounded trajectories of a consistent,
strictly stable linear multistep method applied to the gradient equation. Moreover, we compare the asymptotic features of
the numerical and the exact solutions as done by Humphries, Stuart (1994) and Schropp (1995) for one-step methods. In the
case of -stable formulae this leads to an efficient solver for stiff minimization problems.
Received July 10, 1995 / Revised version received June 27, 1996 相似文献
64.
Dorina Mitrea Marius Mitrea Jill Pipher 《Journal of Fourier Analysis and Applications》1997,3(2):131-192
We study boundary value problems for the time-harmonic form of the Maxwell equations, as well as for other related systems
of equations, on arbitrary Lipschitz domains in the three-dimensional Euclidean space. The main goal is to develop the corresponding
theory for Lp-integrable bounday data for optimal values of p's. We also discuss a number of relevant applications in electromagnetic scattering. 相似文献
65.
66.
67.
In [5] Phillips proved that one can obtain the additive group of any nonstandard model *? of the ring ? of integers by using a linear mod 1 function h : F ?, where F is the α-dimensional vector space over ? when α is the cardinality of *?. In this connection it arises the question whether there are linear mod 1 functions which are neither addition nor quasi-linear. We prove that this is the case. 相似文献
68.
同步荧光法测定食品中维生素B1 总被引:7,自引:0,他引:7
本文研究了食品中维生素B1的同步荧光法测定条件,采用氯化钾-乙醇作柱层析洗脱液,碱性介质中氧化后立即调为中性,并加入表面活性剂OP对体系增稳增敏,取代丁醇萃取,经济方便,用于几种粮食样品的测定,结果满意。 相似文献
69.
Summary. We present a simple proof, based on modified logarithmic Sobolev inequalities, of Talagrand’s concentration inequality for
the exponential distribution. We actually observe that every measure satisfying a Poincaré inequality shares the same concentration
phenomenon. We also discuss exponential integrability under Poincaré inequalities and its consequence to sharp diameter upper
bounds on spectral gaps.
Received: 10 June 1996 / In revised form: 9 August 1996 相似文献
70.
Hiromichi Kurosu Mizuyo Kikuchi Isao Ando 《Journal of Polymer Science.Polymer Physics》1995,33(5):769-775
The solid-state 15N CP/MAS NMR spectra and 15N spin-lattice relaxation times (T1) of doped and dedoped 15N-labeled polypyrroles prepared by electrochemical polymerization, have been measured by means of high-resolution solid-state 15N NMR. The 15N signal of polypyrrole consists of four peaks decomposed by line shape analysis. The four peaks obtained have been assigned to the various structures of polypyrrole. Further, the half-width of the 15N NMR spectra of polypyrroles is discussed as related to the electrical conductivity. © 1995 John Wiley & Sons, Inc. 相似文献