全文获取类型
收费全文 | 89324篇 |
免费 | 14463篇 |
国内免费 | 10623篇 |
专业分类
化学 | 61605篇 |
晶体学 | 1049篇 |
力学 | 6046篇 |
综合类 | 834篇 |
数学 | 10607篇 |
物理学 | 34269篇 |
出版年
2024年 | 290篇 |
2023年 | 1728篇 |
2022年 | 2969篇 |
2021年 | 3088篇 |
2020年 | 3400篇 |
2019年 | 3253篇 |
2018年 | 2854篇 |
2017年 | 2691篇 |
2016年 | 4059篇 |
2015年 | 4068篇 |
2014年 | 4857篇 |
2013年 | 6327篇 |
2012年 | 7634篇 |
2011年 | 7925篇 |
2010年 | 5323篇 |
2009年 | 5215篇 |
2008年 | 5697篇 |
2007年 | 5143篇 |
2006年 | 4906篇 |
2005年 | 4013篇 |
2004年 | 3165篇 |
2003年 | 2674篇 |
2002年 | 2609篇 |
2001年 | 2073篇 |
2000年 | 1997篇 |
1999年 | 2012篇 |
1998年 | 1712篇 |
1997年 | 1570篇 |
1996年 | 1729篇 |
1995年 | 1453篇 |
1994年 | 1316篇 |
1993年 | 1056篇 |
1992年 | 1001篇 |
1991年 | 856篇 |
1990年 | 743篇 |
1989年 | 568篇 |
1988年 | 475篇 |
1987年 | 385篇 |
1986年 | 352篇 |
1985年 | 325篇 |
1984年 | 229篇 |
1983年 | 167篇 |
1982年 | 116篇 |
1981年 | 93篇 |
1980年 | 43篇 |
1979年 | 32篇 |
1977年 | 25篇 |
1976年 | 20篇 |
1975年 | 28篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Wang Li Duan Liying Wang Enbo Xiao Dongrong Li Yangguang Lan Yang Xu Lin Hu Changwen 《Transition Metal Chemistry》2004,29(2):212-215
The novel complex, Co(H2O)5[Co(2,6-pydc)2] (1) has been prepared in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analyses and i.r. spectra. X-ray structural analysis revealed that three novel compounds each possess both – stacking and hydrogen-bonding interaction three-dimensional (3-D) networks. 相似文献
992.
993.
Gao Ping Li Zhen-Jia Chu Hai-Bo Huang Fen-Rei 《Journal of Radioanalytical and Nuclear Chemistry》1996,206(2):233-237
In this article, postsplenectomy changes of serum tuftsin level were studied on both human subjects and rabbits by using a self-established radioimmunoassay protocol. Antituftsin antibodies were raised in rabbits and roosters.125I-tuftsin was prepared through an Iodogen method. The characteristics of the RIA were satisfactory with a detecting range of 0.5–100 ug/ml and the lowest detection limit of 400ng/ml. Serum tuftsin levels of splenectomized subjects were measured and compared with control groups. The serum tuftsin level from 30 postsplenectomy human beings was 406±179 ng/ml (
± s) while that from a control group of 40 healthy blood donors was 557±256 ng/ml; the serum tuftsin level of 10 postsplenectomy rabbits was found to be 206±75 ng/ml while that of a control group of 10 normal rabbits was 318±96 ng/ml. The results showed that serum tuftsin level decreased markedly after splenectomy. 相似文献
994.
流动注射—化学发光法测定苯甲醛 总被引:1,自引:0,他引:1
依据苯甲醛增强没食子酸-过氧化氢-氢氧化钠体系化学发光的性质,建立了苯甲醛的流动注射化学发光分析法。 相似文献
995.
微分倒数示波计时电位法的研究—定量测试及滴定分析 总被引:3,自引:0,他引:3
首次利用微分倒数示波图定量测试微量金属离子并滴定分析药物,结果满意。 相似文献
996.
997.
One new saponin, named capilliposide D (1), and a known saponin, candidoside (2), were isolated from the whole plants of Lysimachia capillipes. Their structures were determined by 1D and 2D NMR, MS techniques, and chemical methods.
Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 268–270, May–June, 2006. 相似文献
998.
It is proposed that in molecular mechanics calculation points belonging to various stable or meta-sta-ble conformtrs are mixed up and form fractal structures in conformation space.The calculation results show the following two phenomena:(i)Two levels of structure with fractal feature were observed.Around the conformer without mirror symmetry points belonging to the conformer and its enantiomer are mixed up and form the first level of fractal structure; on the boundary of the attractive basin o{ each atlractor,points belonging to different attractors form the second level of fractal structure.(ii) The variation of molecular mechanics parameters will influence the structure and area of each attractive basin significantly The above phenomena may become the basis of a new method for solving the troublesome multi-minimum-point problem in molecular mechanics calculation. 相似文献
999.
动力学体系二维数据的秩分析及其应用 总被引:2,自引:0,他引:2
详细论证了动力学体系中存在的多种共线性情况,以及在此情况下二维数据阵的秩与独立反应数及组分数的关系.分析了通过增秩这一方式来判断体系组分数的条件.讨论了反应间存在物质交换对数据阵秩的影响.建立起一套通过秩分析判断未知动力学体系中存在的反应组分数、独立反应数以及可能反应机理的方法.将秩分析技术应用到聚苯胺与质子酸反应,初步分析了该体系存在的多种吸光性结构及结构变化.确定了[H+]=0.01~0.1 mol•L-1范围内,聚苯胺与质子酸反应存在一个三结构两步互变过程. 相似文献
1000.
Direct band gap copper indium chalcogenides are of great technological importance in part because of their high photovoltaic conversion efficiency. Covalent superlattices constructed from copper indium chalcogenide clusters are of particular interest because they may combine open framework architecture with semiconducting properties. Here two photoluminescent covalent superlattices built from core-shell type copper indium sulfide supertetrahedral clusters are reported. Each cluster consists of 35 metal cations and is so far the largest known supertetrahedral cluster with a metal-to-metal distance of 1.6 nm. In addition, this is the first example of supertetrahedral clusters in heterometallic copper indium chalcogenides. The preparation of these large clusters has narrowed down the size gap between colloidal nanoclusters and small supertetrahedral clusters and revealed new possibilities in the construction of nanoporous semiconducting superlattices with tunable pore size. Through the combination of metal ions with different oxidation states to provide both overall and local charge neutrality, an effective approach has been demonstrated in the rational synthesis of chalcogenide open framework materials with large and unprecedented supertetrahedral clusters. 相似文献