全文获取类型
收费全文 | 100795篇 |
免费 | 4237篇 |
国内免费 | 2995篇 |
专业分类
化学 | 40422篇 |
晶体学 | 1065篇 |
力学 | 8044篇 |
综合类 | 241篇 |
数学 | 34343篇 |
物理学 | 23912篇 |
出版年
2024年 | 81篇 |
2023年 | 510篇 |
2022年 | 830篇 |
2021年 | 832篇 |
2020年 | 990篇 |
2019年 | 910篇 |
2018年 | 10995篇 |
2017年 | 10800篇 |
2016年 | 7037篇 |
2015年 | 1860篇 |
2014年 | 1576篇 |
2013年 | 1975篇 |
2012年 | 5804篇 |
2011年 | 12426篇 |
2010年 | 6966篇 |
2009年 | 7309篇 |
2008年 | 8025篇 |
2007年 | 10040篇 |
2006年 | 1538篇 |
2005年 | 2356篇 |
2004年 | 2359篇 |
2003年 | 2660篇 |
2002年 | 1609篇 |
2001年 | 754篇 |
2000年 | 796篇 |
1999年 | 744篇 |
1998年 | 675篇 |
1997年 | 572篇 |
1996年 | 629篇 |
1995年 | 502篇 |
1994年 | 434篇 |
1993年 | 418篇 |
1992年 | 322篇 |
1991年 | 294篇 |
1990年 | 284篇 |
1989年 | 217篇 |
1988年 | 177篇 |
1987年 | 141篇 |
1986年 | 154篇 |
1985年 | 111篇 |
1984年 | 79篇 |
1983年 | 75篇 |
1982年 | 78篇 |
1981年 | 59篇 |
1980年 | 54篇 |
1979年 | 50篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
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
142.
从现有的PCDFs分子的正辛醇 /水分配系数 (logKow)实验数据出发 ,建立定量结构 性质关系方程(QSPR) .采用G98W程序包中的PM3方法对 13 5个多氯代二苯并呋喃 (PCDFs)分子和二苯并呋喃进行了优化计算 ,作业命令为 #pPM3optfreqscf(conver =9) ,以计算所得的分子轨道能量、碳原子电荷作为PCDFs分子结构描述符 ,运用多元线性回归技术建立了PCDFs的logKow与分子结构描述符的四元方程 ,最优相关系数为 0 .95 0 7,标准偏差为 0 .173 7,经检验该模型的稳健性好 ,并对未有实验数据的 85个PCDFs的logKow进行预测 相似文献
143.
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
144.
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
145.
146.
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
147.
This paper analyzes the compromise social choice correspondence derived from the τ-value of digraph games. Monotonicity of
this correspondence is shown. A connection between several properties of social choice correspondences based on game theoretical
solutions and game theoretical properties of the underlying solutions is given. Applications to several game theoretic solutions
are provided. 相似文献
148.
Polarization self-modulation effect in a free oscillated Nd:YAG laser is investigated after a quarter wave plate is introduced independently in the two positions of the cavity. As described in the previous experiments, the intensity components in the orthogonal directions are modulated with a period of the round-trip time or twice. Different pulse shapes reveal that the seed field from the spontaneous emission is not uniform and seems to be stochastic for each pulse. 相似文献
149.
The original article to which this Erratum refers was published in Journal of Graph Theory 47:129–146,2004 . 相似文献
150.
A new reagent, potassium permanganate adsorbed on aluminum silicate, suitable for the oxidation of primary and secondary alcohols to the corresponding carbonyl compounds is described. 相似文献