全文获取类型
收费全文 | 148590篇 |
免费 | 11276篇 |
国内免费 | 7789篇 |
专业分类
化学 | 72949篇 |
晶体学 | 1514篇 |
力学 | 11259篇 |
综合类 | 566篇 |
数学 | 40319篇 |
物理学 | 41048篇 |
出版年
2024年 | 158篇 |
2023年 | 1451篇 |
2022年 | 2118篇 |
2021年 | 2472篇 |
2020年 | 2778篇 |
2019年 | 2650篇 |
2018年 | 12194篇 |
2017年 | 11842篇 |
2016年 | 8916篇 |
2015年 | 4075篇 |
2014年 | 4095篇 |
2013年 | 5456篇 |
2012年 | 9893篇 |
2011年 | 16531篇 |
2010年 | 9797篇 |
2009年 | 10098篇 |
2008年 | 10868篇 |
2007年 | 12545篇 |
2006年 | 4070篇 |
2005年 | 4620篇 |
2004年 | 4168篇 |
2003年 | 3964篇 |
2002年 | 2829篇 |
2001年 | 1872篇 |
2000年 | 1803篇 |
1999年 | 1809篇 |
1998年 | 1560篇 |
1997年 | 1358篇 |
1996年 | 1459篇 |
1995年 | 1227篇 |
1994年 | 1096篇 |
1993年 | 987篇 |
1992年 | 843篇 |
1991年 | 751篇 |
1990年 | 620篇 |
1989年 | 548篇 |
1988年 | 449篇 |
1987年 | 413篇 |
1986年 | 371篇 |
1985年 | 364篇 |
1984年 | 260篇 |
1983年 | 219篇 |
1982年 | 198篇 |
1981年 | 155篇 |
1980年 | 134篇 |
1979年 | 102篇 |
1978年 | 98篇 |
1977年 | 77篇 |
1975年 | 81篇 |
1973年 | 88篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
YaoKui ChenZhixiang 《分析论及其应用》2003,19(2):115-120
This paper gives the weighted Lp convergence rate estimations of the Gruenwald interpolatory polynomials based on the zeros of Chebyshev polymomials of the first kind,and proves that the order of the estimations is optimal for p≥1. 相似文献
262.
You‐Liang Zhao Chuan‐Fu Chen Fu Xi 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2156-2165
The atom transfer radical copolymerization of N‐substituted maleimides such as N‐phenylmaleimide (PhMI), N‐cyclohexylmaleimide (ChMI), and N‐butylmaleimide (NBMI) with styrene initiated with dendritic polyarylether 2‐bromoisobutyrates in an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF6]), at room temperature and anisole at 110 °C was investigated. The dendritic‐linear block copolymers obtained in ionic liquid possessed well‐defined molecular weight and low polydispersity (1.05 < Mw/Mn < 1.32) and could be used as a macroinitiator for chain‐extension polymerization, suggesting the living nature of the reaction system. The ionic liquids containing catalyst could be recycled in the atom transfer radical polymerization systems without further treatment. Compared with polymerization conducted in anisole, the polymerization in ionic liquid had a stronger tendency for alternation. The tendency for alternation decreased in the order PhMI > NBMI > ChMI in [bmim][PF6] and PhMI > ChMI > NBMI in anisole. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2156–2165, 2003 相似文献
263.
264.
265.
Howard Robinson 《Acta Analytica》2005,20(3):7-10
Nicholas Nathan tries to resist the current version of the causal argument for sense-data in two ways. First he suggests that,
on what he considers to be the correct re-construction of the argument, it equivocates on the sense of proximate cause. Second
he defends a form of disjunctivism, by claiming that there might be an extra mechanism involved in producing veridical hallucination,
that is not present in perception. I argue that Nathan’s reconstruction of the argument is not the appropriate one, and that,
properly interpreted, the argument does not equivocate on proximate cause. Furthermore, I claim that his postulation of a
modified mechanism for hallucinations is implausibly ad hoc. 相似文献
266.
Chris Pollett 《Archive for Mathematical Logic》2003,42(5):469-488
The paper establishes lower bounds on the provability of 𝒟=NP and the MRDP theorem in weak fragments of arithmetic. The
theory I
5
E
1
is shown to be unable to prove 𝒟=NP. This non-provability result is used to show that I
5
E
1
cannot prove the MRDP theorem. On the other hand it is shown that I
1
E
1
proves 𝒟 contains all predicates of the form (∀i≤|b|)P(i,x)^Q(i,x) where ^ is =, <, or ≤, and I
0
E
1
proves 𝒟 contains all predicates of the form (∀i≤b)P(i,x)=Q(i,x). Here P and Q are polynomials. A conjecture is made that 𝒟 contains NLOGTIME. However, it is shown that this conjecture would not be sufficient
to imply 𝒟=N P. Weak reductions to equality are then considered as a way of showing 𝒟=NP. It is shown that the bit-wise less than predicate,
≤2, and equality are both co-NLOGTIME complete under FDLOGTIME reductions. This is used to show that if the FDLOGTIME functions
are definable in 𝒟 then 𝒟=N P.
Received: 13 July 2001 / Revised version: 9 April 2002 /
Published online: 19 December 2002
Key words or phrases: Bounded Arithmetic – Bounded Diophantine Complexity 相似文献
267.
268.
269.
A novel and simple two-frequency Brillouin fiber laser is presented. It is based on a fiber Fabry-Perot cavity with fiber Bragg gratings as reflectors. The model of stimulated Brillouin scattering in fiber grating-based Fabry-Perot resonator is investigated. The laser allows conversion efficiency of close to 100% and suppresses the higher-order Stokes waves. The theoretical prediction is presented and the experimental demonstration is realized. 相似文献
270.
Grégory Duby 《Archive for Mathematical Logic》2003,42(5):435-447
This paper generalizes results of F. K?rner from [4] where she established the existence of maximal automorphisms (i.e. automorphisms
moving all non-algebraic elements). An ω-maximal automorphism is an automorphism whose powers are maximal automorphisms. We
prove that any structure has an elementary extension with an ω-maximal automorphism. We also show the existence of ω-maximal
automorphisms in all countable arithmetically saturated structures. Further we describe the pairs of tuples (ˉa,ˉb) for which there is an ω-maximal automorphism mapping ˉa to ˉb.
Received: 12 December 2001 /
Published online: 10 October 2002
Supported by the ``Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture'
Mathematics Subject Classification (2000): Primary: 03C50; Secondary: 03C57
Key words or phrases: Automorphism – Recursively saturated structure 相似文献