全文获取类型
收费全文 | 114360篇 |
免费 | 6915篇 |
国内免费 | 4846篇 |
专业分类
化学 | 49896篇 |
晶体学 | 1298篇 |
力学 | 9004篇 |
综合类 | 299篇 |
数学 | 36076篇 |
物理学 | 29548篇 |
出版年
2024年 | 95篇 |
2023年 | 773篇 |
2022年 | 1065篇 |
2021年 | 1266篇 |
2020年 | 1542篇 |
2019年 | 1454篇 |
2018年 | 11383篇 |
2017年 | 11127篇 |
2016年 | 7684篇 |
2015年 | 2590篇 |
2014年 | 2417篇 |
2013年 | 3002篇 |
2012年 | 6960篇 |
2011年 | 13808篇 |
2010年 | 7906篇 |
2009年 | 8235篇 |
2008年 | 8999篇 |
2007年 | 10826篇 |
2006年 | 2378篇 |
2005年 | 2978篇 |
2004年 | 2841篇 |
2003年 | 3057篇 |
2002年 | 2036篇 |
2001年 | 1093篇 |
2000年 | 1167篇 |
1999年 | 997篇 |
1998年 | 939篇 |
1997年 | 833篇 |
1996年 | 895篇 |
1995年 | 737篇 |
1994年 | 619篇 |
1993年 | 524篇 |
1992年 | 480篇 |
1991年 | 394篇 |
1990年 | 355篇 |
1989年 | 297篇 |
1988年 | 262篇 |
1987年 | 230篇 |
1986年 | 210篇 |
1985年 | 198篇 |
1984年 | 147篇 |
1983年 | 107篇 |
1982年 | 102篇 |
1981年 | 74篇 |
1980年 | 62篇 |
1979年 | 54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 15 毫秒
191.
本文对一般微分代数方程给出了几类可解集的概念,并讨论了多项式微分代数方程的可解集,得到子多项式系统具有唯一解。特别是有多于一个的解的条件,并得到了低次多项式在一定意义下的充分必要条件。 相似文献
192.
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
193.
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
194.
195.
A method for fabricating well-dispersed nanowire suspension has been demonstrated in the paper. Thin gold nanowires were prepared by template synthesis, and then functionalized with sulphonate group-terminated thiols before suspended in different solvents. The degree of aggregation of the obtained suspension was evaluated with transmission electron microscopy (TEM) and UV-vis spectroscopy. It was found that the degree of aggregation was predominated by the solvents, and the best degree of dispersion was obtained when isopropyl alcohol (IPA) was used as the solvent. The gold nanowires from the suspension can be selectively assembled onto chemically patterned substrates. This well-dispersed nanowire suspension is potentially useful for fabricating novel nanodevices. 相似文献
196.
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
197.
Some new oscillation criteria are established for a second order neutral delay differential equations. These results improve oscillation results of Y.V. Rogo-vchenko for the retarded delay differential equations. The relevance of our theorems is illustrated with two carefully selected examples. 相似文献
198.
199.
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
200.
A technique is described for the measurement of all components of mean velocity and Reynolds stresses, in a complex turbulent flow where achieving coincidence data acquisition is difficult. The method is based on data recorded using four orientations of the laser probe. It is shown that the measurement errors are not the same for all the components of the Reynolds tensor, but they are sufficiently small to give a good accuracy. An application to a turbomachinery flow is given to illustrate the method. 相似文献