全文获取类型
收费全文 | 66412篇 |
免费 | 14697篇 |
国内免费 | 6154篇 |
专业分类
化学 | 63500篇 |
晶体学 | 802篇 |
力学 | 2160篇 |
综合类 | 382篇 |
数学 | 5517篇 |
物理学 | 14902篇 |
出版年
2024年 | 132篇 |
2023年 | 661篇 |
2022年 | 1250篇 |
2021年 | 1443篇 |
2020年 | 2515篇 |
2019年 | 3807篇 |
2018年 | 2204篇 |
2017年 | 1903篇 |
2016年 | 4845篇 |
2015年 | 5090篇 |
2014年 | 5355篇 |
2013年 | 6398篇 |
2012年 | 5913篇 |
2011年 | 5188篇 |
2010年 | 5108篇 |
2009年 | 4913篇 |
2008年 | 4536篇 |
2007年 | 3831篇 |
2006年 | 3331篇 |
2005年 | 3070篇 |
2004年 | 2472篇 |
2003年 | 2164篇 |
2002年 | 2858篇 |
2001年 | 2148篇 |
2000年 | 1916篇 |
1999年 | 980篇 |
1998年 | 504篇 |
1997年 | 418篇 |
1996年 | 348篇 |
1995年 | 310篇 |
1994年 | 295篇 |
1993年 | 235篇 |
1992年 | 205篇 |
1991年 | 189篇 |
1990年 | 165篇 |
1989年 | 125篇 |
1988年 | 99篇 |
1987年 | 71篇 |
1986年 | 76篇 |
1985年 | 56篇 |
1984年 | 25篇 |
1983年 | 25篇 |
1982年 | 24篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1977年 | 4篇 |
1971年 | 4篇 |
1957年 | 4篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
42.
本文主要解决奇异非光滑方程组的解法。应用一种新的次微分的外逆,我们提出了牛顿法和不精确牛顿法,它们的收敛性同时也得到了证明。这种方法能更容易在一引起实际应用中实现。这种方法可以看作是已存在的解非光滑方程组的方法的延伸。 相似文献
43.
44.
与HBV X蛋白相互作用的细胞蛋白的筛选及其鉴定 总被引:1,自引:1,他引:0
参考GenBank核苷酸序列库中的HBV的核苷酸序列设计合成了一对对应于HBx基因的引物,从原发性肝癌(hepatocellular carcinoma,HCC)患者的血清中提取HBV基因组DNA作为模板,扩增HBx编码区并测定了核苷酸序列.将该编码区克隆到酵母双杂交系统的诱饵蛋白表达载体pGBKT7中,转入酵母细胞AH109,进行表型鉴定.然后通过Mating实验从已制备好用于酵母双杂交系统的肝cDNA表达文库中筛选与HBx相互作用的细胞蛋白,并用体外免疫共沉淀实验进一步验证.研究表明,分离得到的与HBx基因编码的蛋白相互作用的4种新的细胞蛋白,分别是醛缩酶B、C8α亚基、一种丝氨酸蛋白酶Hepsin和一种未知蛋白. 相似文献
45.
46.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献
47.
Yan WANG Rong Quan FENG 《数学学报(英文版)》2005,21(4):773-778
A Cayley map is a Cayley graph embedded in an orientable surface such that. the local rotations at every vertex are identical. In this paper, balanced regular Cayley maps for cyclic groups, dihedral groups, and generalized quaternion groups are classified. 相似文献
48.
The inhomogeneous Dirichlet problems concerning divergence form elliptic equations are studied. Optimal regularity requirements on the coefficients and domains for the W1,p theory, 1 < p < ∞, are obtained. The principal coefficients are supposed to be in the John‐Nirenberg space with small BMO seminorms. The domain is a Reifenberg domain. These conditions for the W1,p theory not only weaken the requirements on the coefficients but also lead to a more general geometric condition on the domains. In fact, these domains might have fractal dimensions. © 2004 Wiley Periodicals, Inc. 相似文献
49.
Wang Qing-Lun Zhao Bin Liao Dai-Zheng Yan Shi-Ping Cheng Peng Jiang Zong-Hui 《Transition Metal Chemistry》2003,28(3):326-330
The copper(II) complex Na2[Cu(pba)] · 6H2O has been synthesized and its structure determined. It consists of a novel two-dimensional network of [Cu(pba)]2– anions connected to each other through the sodium ion as a bridge. Spectroscopic and magnetic properties have been measured and a spin distribution calculation has been carried out with the GAUSSIAN-94. Theoretical calculations indicate the rather larger spin density on nitrogen atoms should be responsible for the satellite lines appearing beside the main hyperfine coupling signs of copper(II). The antiferromagnetic interaction may be due to the intermolecular interaction and/or different copper(II) ions through the Na+ bridge in the same layer. 相似文献
50.
Marcelino Maneiro Manuel R. Bermejo M. Isabel Fernndez Ana M. Gonzlez‐Noya Alexei M. Tyryshkin Robin G. Pritchard 《无机化学与普通化学杂志》2003,629(2):285-290
A new MnIII‐Schiff base complex, [MnL(OH2)](ClO4) ( 1 ) (H2L = N, N′‐bis‐(3‐Br‐5‐Cl‐salicylidene)‐1, 2‐diimino‐2‐methylethane), an inorganic model of the catalytic center (OEC, Oxygen Evolving Complex) in photosystem II (PSII), has been synthesized and characterized by elemental analysis, IR and EPR spectroscopy, mass spectrometry, magnetic susceptibility measurement and the study of its redox properties by cyclic and normal pulse voltammetry. This complex mimics reactivity (showing a relevant photolytic activity), and also some structural characteristics (parallel‐mode MnIII EPR signal from partially assembled OEC cluster) of the natural OEC. The complex 1 was found to rearrange in solution into a crystallographically solved square‐pyramidal complex, [MnLL′] ( 2 ) (HL′ = 6‐bromo‐4‐chloro‐2‐cyanophenol), through a process, which probably liberates radical species (detected by EPR), and provokes a C—N bond cleavage in the ligand. A photo‐radical mechanism is discussed to explain this rearrangement. 相似文献