全文获取类型
收费全文 | 8080篇 |
免费 | 1463篇 |
国内免费 | 1453篇 |
专业分类
化学 | 6924篇 |
晶体学 | 89篇 |
力学 | 355篇 |
综合类 | 104篇 |
数学 | 902篇 |
物理学 | 2622篇 |
出版年
2024年 | 30篇 |
2023年 | 160篇 |
2022年 | 250篇 |
2021年 | 258篇 |
2020年 | 367篇 |
2019年 | 414篇 |
2018年 | 356篇 |
2017年 | 293篇 |
2016年 | 419篇 |
2015年 | 482篇 |
2014年 | 490篇 |
2013年 | 656篇 |
2012年 | 688篇 |
2011年 | 679篇 |
2010年 | 540篇 |
2009年 | 531篇 |
2008年 | 553篇 |
2007年 | 482篇 |
2006年 | 452篇 |
2005年 | 377篇 |
2004年 | 358篇 |
2003年 | 342篇 |
2002年 | 391篇 |
2001年 | 262篇 |
2000年 | 218篇 |
1999年 | 205篇 |
1998年 | 139篇 |
1997年 | 107篇 |
1996年 | 81篇 |
1995年 | 60篇 |
1994年 | 61篇 |
1993年 | 33篇 |
1992年 | 39篇 |
1991年 | 47篇 |
1990年 | 32篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1968年 | 4篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
TEM investigation of formation mechanism of monocrystal-thick b-oriented pure silica zeolite MFI film 总被引:3,自引:0,他引:3
Li S Li Z Bozhilov KN Chen Z Yan Y 《Journal of the American Chemical Society》2004,126(34):10732-10737
The first direct transmission electron microscopic (TEM) observation has been carried out on the continuous monocrystal-thick b-oriented pure silica zeolite MFI films produced by in situ crystallization. The self-supporting film samples for TEM study were fabricated by dissolving the steel substrate with acid. This TEM study is free of those artifacts that are typically associated with TEM sample preparations, and allows us to investigate the "true" structure and texture of a very large area of the film and at the same time to focus at will on each individual zeolite crystal in the film. Abundant TEM information including crystallographic orientation relationships among crystals in the film (both out-of-plane and in-plane), grain boundaries, and each crystal grain was obtained. This TEM investigation provides direct unambiguous new evidence to support the homogeneous nucleation mechanism, by which the films form through homogeneous nucleation and crystal growth in the bulk to form equal-sized disk-shape crystals, followed by self-assembly of these crystals onto the substrate to produce a two-dimensional close-packed structure. The last stage of the film formation involves simultaneous space-limited growth and rotation of the individual crystals to realize the in-plane crystallographic control within the film. 相似文献
103.
104.
通过2,4-二苯基-2,3-二氢-1H-1,5-苯并二氮杂(艹卓)与苯甲酰氯苯腙的[2+3]环加成反应制备了标题化合物,用X射线单晶衍射仪测定了其晶体结构.晶体属正交晶系,空间群为Fdd2.晶胞参数:a=1.762 8(4)nm,b=5.751 2(12)nm,c=1.022 7 nm,V=10.368(5)nm3,Z=16,Dc=1.262 g·cm-3,μ=0.075 mm-1,F(000)=4 160,1 139个可观测衍射点,R-0.046 1,Rw=0.056 0. 相似文献
105.
106.
107.
108.
JinShengZHAO ZhenYuYANG YiHeZHANG ZhengYuYANG 《中国化学快报》2004,15(11):1361-1364
Cellulose/cellulose acetate membranes were prepared and functionalized by introducingamino group on it, and then immobilized the glucose oxidase (Gox) on the functionalizd membrane.SECM was applied for the detection of enzyme activity immobilized on the membrane.Immobilized biomolecules on such membranes was combined with analysis apparatus and can beused in bioassays. 相似文献
109.
Xin Gen Luo Hai Sheng Chen Shuang Liang Mao Huang Wei Dong Xuan Li Jin College of Pharmacy Second Military Medical University Shanghai China Department of Pharmacy Guangzhou Military General Hospital Guangzhou China Center of New Drug Evaluation Institute of Basic Medical Sciences Second Military Medical University Shanghai China 《中国化学快报》2007,18(6):697-699
Six indole alkaloids were isolated from the stems of Ervatamia yunnanensis. Among them, yunnanensine (I) is new. The other five are known alkaloids, namely: 19,20-E-vallesamine (II), 19s-heyneanine (HI), ibogaine (IV), ibogamine (V), coronaridine (VI). The structural elucidation of the alkaloids was based on spectral means. 相似文献
110.
In order to explore the transfer mechanism of chromium(III) in mammals, a novel complex [Cr(ASA)(en)2]Cl· 2H2O, bis(ethylenediamine‐ κ 2 N,N′)(4‐aminosalicylic acid‐ κ 2 O,O′) chromium(III) monochloride dihydrate was synthesized (4‐aminosalicylic acid=H2ASA, ethylenediamine=en). The crystal structure belongs to orthorhombic system with the space group P212121 by means of X‐ray diffraction. The characteristic for transfer of Cr3+ from the compound to the low‐molecular‐mass chelator EDTA and the iron‐binding protein apoovotransferrin (apoOTf) was followed by UV‐visible (UV‐Vis) and fluorescence spectra in 0.01 mol·L?1 Hepes at pH 7.4. The second order rate constants were calculated. Those spectra in conjunction were used to obtain more accurate information about the interaction of chromium complex with apoOTf. The experimental results indicate that Cr3+ can be transferred from the complex to apoOTf with the retention of the 4‐aminosalicylic acid acting as a synergistic anion. 相似文献