全文获取类型
收费全文 | 1395篇 |
免费 | 122篇 |
国内免费 | 103篇 |
专业分类
化学 | 755篇 |
晶体学 | 10篇 |
力学 | 16篇 |
综合类 | 14篇 |
数学 | 576篇 |
物理学 | 249篇 |
出版年
2023年 | 7篇 |
2022年 | 26篇 |
2021年 | 33篇 |
2020年 | 52篇 |
2019年 | 35篇 |
2018年 | 39篇 |
2017年 | 42篇 |
2016年 | 49篇 |
2015年 | 49篇 |
2014年 | 65篇 |
2013年 | 139篇 |
2012年 | 68篇 |
2011年 | 57篇 |
2010年 | 61篇 |
2009年 | 88篇 |
2008年 | 76篇 |
2007年 | 90篇 |
2006年 | 68篇 |
2005年 | 54篇 |
2004年 | 70篇 |
2003年 | 67篇 |
2002年 | 51篇 |
2001年 | 43篇 |
2000年 | 28篇 |
1999年 | 42篇 |
1998年 | 25篇 |
1997年 | 34篇 |
1996年 | 20篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 11篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有1620条查询结果,搜索用时 31 毫秒
991.
Es werden die wesentlichsten Probleme und Aufgaben des Umweltschutzes hinsichtlich der verschiedenen Komponenten der natürlichen und zivilisatorischen Strahlenbelastung, die Überwachung auf Radioaktivität als Folge der Kernwaffenversuche und die Umgebungsüberwachung von Kernanlagen beschrieben. Es wird ein Überblick über die verschiedenen Bestimmungsmethoden der Radionuklide, die Schritte der Probenaufbereitung, die zur Alpha-, Beta- und Gammamessung verwendeten Verfahren sowie die Meßwertverarbeitung gegeben. 相似文献
992.
Von den radioaktiven Falloutprodukten ist das 90Sr bei weitem das gefährlichste, da es von den Pflanzen und Tieren wegen seiner chemischen Verwandtschaft zum Calcium wie dieses im Organismus eingebaut wird und auf dem Wege der Verteilerkette Boden–Pflanze–Tier–Mensch schließlich auch im menschlichen Organismus eingebaut wird. 相似文献
993.
Let h be a positive integer and S?=?{x 1,?…?,?x h } be a set of h distinct positive integers. We say that the set S is a divisor chain if x σ(1) ∣?…?∣ x σ(h) for a permutation σ of {1,?…?,?h}. If the set S can be partitioned as S?=?S 1?∪?S 2?∪?S 3, where S 1, S 2 and S 3 are divisor chains and each element of S i is coprime to each element of S j for all 1?≤?i?<?j?≤?3, then we say that the set S consists of three coprime divisor chains. The matrix having the ath power (x i , x j ) a of the greatest common divisor of x i and x j as its i, j-entry is called the ath power greatest common divison (GCD) matrix on S, denoted by (S ?a ). The ath power least common multiple (LCM) matrix [S ?a ] can be defined similarly. In this article, let a and b be positive integers and let S consist of three coprime divisor chains with 1?∈?S. We show that if a?∣?b, then the ath power GCD matrix (S ?a ) (resp., the ath power LCM matrix [S ?a ]) divides the bth power GCD matrix (S ?b ) (resp., the bth power LCM matrix [S ?b ]) in the ring M h (Z) of h?×?h matrices over integers. We also show that the ath power GCD matrix (S ?a ) divides the bth power LCM matrix [S ?b ] in the ring M h (Z) if a?∣?b. However, if a???b, then such factorizations are not true. Our results extend Hong's and Tan's theorems and also provide further evidences to the conjectures of Hong raised in 2008. 相似文献
994.
995.
996.
Martial Longla 《Statistics & probability letters》2013,83(10):2439-2445
We study dependence coefficients for copula-based Markov chains. We provide new tools to check the convergence rates of mixing coefficients of copula-based Markov chains. We apply results to the Metropolis–Hastings algorithm. A necessary condition for symmetric copulas is given and mixtures of copulas are studied. 相似文献
997.
Ekaterina Sokolovskaya Jaewon Yoon Asish C. Misra Stefan Brse Jrg Lahann 《Macromolecular rapid communications》2013,34(19):1554-1559
A novel water insoluble, multifunctional poly(ethylene glycol), poly(hydrazide ethylene glycol‐co‐benzyl glycidyl ether) (P(HZ‐co‐BnGE)), is synthesized via thiol‐ene click reaction of poly(allyl glycidyl ether‐co‐benzyl glycidyl ether) (P(AGE‐co‐BnGE)). The base polymer P(AGE‐co‐BnGE) is previously prepared by anionic ring‐opening copolymerization of the corresponding monomers. To demonstrate utility, bicompartmental microspheres and microcylinders containing P(HZ‐co‐BnGE) in one of the compartments are prepared via electrohydrodynamic (EHD) co‐jetting. Next, spatially controlled surface reactivity toward sugars is demonstrated by selective binding of 2α‐mannobiose to the P(HZ‐co‐BnGE) compartment only, as confirmed by a carbohydrate‐lectin‐binding assay. These sugar‐reactive hydrazide‐presenting microparticles have potential applications for glyco‐targeted drug delivery.
998.
Baozhong Zhang Anja Kroeger A. Dieter Schlüter Gerhard Wegner 《Macromolecular rapid communications》2013,34(19):1537-1541
The intrinsic viscosity [η] of dendronized linear macromolecules dissolved in thermodynamically good solvents depends both on chain length that is contour length Lc of the backbone of the polymer and on the persistence length lp. Investigating a set of samples of identical Lc but differing in the generation number for which data on lp are available, it becomes possible to establish a generalized viscosity law in the form [η] = K(M/Mp)α in which Mp denotes the molar mass of the objects per lp, M is the total molar mass, K is a constant, and α is the Mark–Howink exponent, which is found to be 0.55.
999.
The problem is analysed for extrapolating power series, derived for an asymptotically small variable, to the region of finite values of this variable. The consideration is based on the self-similar approximation theory. A new method is suggested for defining the odd self-similar factor approximants by employing an optimisation procedure. The method is illustrated by several examples having the mathematical structure typical of the problems in statistical and chemical physics. It is shown that the suggested method provides a good accuracy even when the number of terms in the perturbative power series is small. 相似文献
1000.