全文获取类型
收费全文 | 15544篇 |
免费 | 2569篇 |
国内免费 | 1873篇 |
专业分类
化学 | 11624篇 |
晶体学 | 186篇 |
力学 | 806篇 |
综合类 | 100篇 |
数学 | 1385篇 |
物理学 | 5885篇 |
出版年
2024年 | 53篇 |
2023年 | 277篇 |
2022年 | 522篇 |
2021年 | 581篇 |
2020年 | 654篇 |
2019年 | 651篇 |
2018年 | 574篇 |
2017年 | 478篇 |
2016年 | 770篇 |
2015年 | 725篇 |
2014年 | 868篇 |
2013年 | 1212篇 |
2012年 | 1382篇 |
2011年 | 1351篇 |
2010年 | 935篇 |
2009年 | 939篇 |
2008年 | 1048篇 |
2007年 | 945篇 |
2006年 | 852篇 |
2005年 | 758篇 |
2004年 | 620篇 |
2003年 | 524篇 |
2002年 | 570篇 |
2001年 | 396篇 |
2000年 | 292篇 |
1999年 | 306篇 |
1998年 | 250篇 |
1997年 | 224篇 |
1996年 | 204篇 |
1995年 | 169篇 |
1994年 | 142篇 |
1993年 | 111篇 |
1992年 | 108篇 |
1991年 | 107篇 |
1990年 | 69篇 |
1989年 | 58篇 |
1988年 | 41篇 |
1987年 | 31篇 |
1986年 | 35篇 |
1985年 | 35篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 9篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971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
131.
[structure: see text] Platinum(II) terpyridyl acetylide complex (1) was incorporated into Nafion membranes as a photosensitizer, and the Nafion was immersed in an aqueous or organic solution of 7-dehydrocholesterol, alpha-pinene, or cyclopentadiene. This photosensitizer system can generate singlet oxygen ((1)O(2)) in high quantum yield to oxidize the alkenes in the solution outside the Nafion and can be easily removed from the reaction vessel at the end of the photooxidation. 相似文献
132.
The adsorption and photocatalutic decomposition of citric acid on both Pt/TiO2 powder and n-TiO2 single crystal electrode were studied in aqueous solutions of various pH. It was found that citrate ions were chemisorbed on TiO2, which could increase the interfacial capacity and the filling factor of photocurrent-potential curves. The quantity of adsorption, slope of mott-Shottky plot and the rate of photocatalytic decomposition of citric acid were found to depend strongly on pH of solution. The phot ocatalytic decomposition of citric acid was discussed in light of its adsorption on TiO2. 相似文献
133.
本文报道了一类新型全硫冠醚聚合物的合成,即由聚环硫氯丙烷与二巯基化合物反应,生成具有冠醚环结构单元的交联型聚合物。并研究了这些聚合物的对金属离子的络合性能。 相似文献
134.
A piezoelectric nucleic acid sensor was constructed ofr detection of tumor necrosis factor gene.Two methods were employed for immobilization of nucleic acid probe on gold electrode of piezoelectric crystal.The results show that polyethyleneimine adbesion and glutaraldehyde cross-linking method has higher sensitivity,stability and selectivity than protein A method.The solid-phase nucleic acid hybridization of oligo unclecotides and tumor necrosis factor target gene sequence were monitorde using this sensor.Tumor necrosis factor gene sequence(580bp) was detected by this nucleic acid sensor for the first time. 相似文献
135.
关于Liesegang环形成机理的研究 总被引:1,自引:0,他引:1
本文研究了Liesegang环的形成,受到两扩散电解质溶液的浓度比、离子浓度积及光照等条件影响。侧重对成环的微观汇聚过程进行了探讨。 相似文献
136.
For the first time the isomerization of 1,3,2-diazaphospholidine-2-sclenide dervatives in refluxing benzene in the presence of trace water was observed. The structures of isomerized products were determined by IR, ^1H NMR,^31P NMR, elemental analysis and X-ray crystallography. The mechanism of isomerization was also proposed. 相似文献
137.
138.
The new electrical and optical properties of nanomaterials depend sensitively on both size and shape, which are of both fundamental and technological interest. This paper introduces a simple chemical method to produce copper particles, which has the ability to shape the particle without using any capping agent or template. In our synthetic procedure, the reactant concentration and temperature exerted a strong influence on the shape of the copper particles. At low reactant concentrations, the particles were cubic; at high reactant concentrations, obtained particles were spherical. The number of hollow particles greatly increased when the synthesis was performed at low temperature. We also synthesized a copper cubic ring at lower temperature, and it has been rarely reported. The absorption spectrum of hollow particles showed obvious red shifts, which suggests the possible assembly of novel optical materials. 相似文献
139.
140.
锂辉石—石灰石烧结中煤粉代替重油作燃料的研究和实践 总被引:1,自引:0,他引:1
目前世界锂工业原料以锂辉石为主。我国锂辉石储量居世界首位,主要分布于新疆、四川、湖南等地,其中又以四川的储量占全国第一。锂的主要基础化合物LiOHH2O系用锂辉石-石灰石烧结法而得,烧结燃料是影响LiOHH2O产品价格的重要因素之一。过去国内外均采用... 相似文献