全文获取类型
收费全文 | 5300篇 |
免费 | 873篇 |
国内免费 | 593篇 |
专业分类
化学 | 3695篇 |
晶体学 | 61篇 |
力学 | 312篇 |
综合类 | 35篇 |
数学 | 594篇 |
物理学 | 2069篇 |
出版年
2024年 | 16篇 |
2023年 | 111篇 |
2022年 | 143篇 |
2021年 | 171篇 |
2020年 | 201篇 |
2019年 | 153篇 |
2018年 | 164篇 |
2017年 | 144篇 |
2016年 | 234篇 |
2015年 | 236篇 |
2014年 | 310篇 |
2013年 | 351篇 |
2012年 | 460篇 |
2011年 | 473篇 |
2010年 | 355篇 |
2009年 | 323篇 |
2008年 | 329篇 |
2007年 | 330篇 |
2006年 | 297篇 |
2005年 | 258篇 |
2004年 | 201篇 |
2003年 | 139篇 |
2002年 | 163篇 |
2001年 | 125篇 |
2000年 | 107篇 |
1999年 | 120篇 |
1998年 | 111篇 |
1997年 | 98篇 |
1996年 | 95篇 |
1995年 | 68篇 |
1994年 | 83篇 |
1993年 | 55篇 |
1992年 | 57篇 |
1991年 | 57篇 |
1990年 | 35篇 |
1989年 | 55篇 |
1988年 | 38篇 |
1987年 | 35篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有6766条查询结果,搜索用时 15 毫秒
91.
Ohsuna T Slater B Gao F Yu J Sakamoto Y Zhu G Terasaki O Vaughan DE Qiu S Catlow CR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(20):5031-5040
High-resolution electron microscopy (HREM) has been used to image the surface structure of nano- and micrometer-sized synthetic crystals of zeolite-Linde-L (LTL). Columnar holes and rotational, nano-sized, wheel-like defects were observed within the crystals, where the hole has a minimum size equal to that of the rotational defect. Predictions of surface structure from atomistic computer simulation concur with the observations from HREM and provide insight into the crystal growth mechanism of perfect and defective LTL. Analysis of the energetics of the formation of rotational defect structures reveals that the driving force for defect creation is thermodynamic and furthermore, the rotational defects could be created in high concentrations. Formation of a columnar hole is found to be slightly energetically unfavourable and therefore we speculate that the incidence of both rotational and nano-sized vacancy defects is strongly dependent on kinetic factors and reaction conditions. The morphology of nano- and microcrystalline LTL is contradistinct and we use insights from simulation to propose an explanation of the disparity in crystal shape. 相似文献
92.
A simple and sensitive HPLC method for quantitative determination of guanidine in high salt and protein matrices was developed. The HPLC system consisted of an Agilent 1100 pump with an online degasser, a UV detector, an autosampler, and Dionex CS 14 cation-exchange guard (4 mm x 50 mm) and analytical (4 mm x 250 mm) columns. The mobile phase was 3.75 mM methanesulfonic acid (MSA) with a flow rate of 1 mL/min. The other analysis parameters were: 50 microL injection volume, 195 nm UV detection, and 21 min runtime. The limit of quantitation (LOQ) for guanidine HCl was determined to be 0.25 mg/L and the standard curve ranged from 0.25 mg/L to 10 mg/L. Sample preparation was required for the samples containing high protein concentrations. Proteins were removed by centrifuging a sample in a 30 K NanoSep centrifugal filter at 15,300 x g for 20 min. The method could determine guanidine accurately in sample matrices containing up to 200 mM sodium ion or up to 50 mM potassium ion. The method can be used for clearance testing of guanidine in biopharmaceutical products. 相似文献
93.
CO hydrogenation on tungsten carbides has been investigated.The methanation activitiesof tungsten carbides are comparable to that of supported Group VIII metal catalysts.Temperature-programmed thermal desorption spectra of CO on tungsten carbide show that CO is adsorbed non-dissociatively,and the surface—CO bond appears to be rather weak. 相似文献
94.
95.
96.
97.
98.
99.
偏最小二乘法在原子吸收光谱分析中的应用——钴和铟的同时测定 总被引:4,自引:1,他引:3
本文用偏最小二乘法(PLS)校正了火焰原子吸收分析In252.137nm对Co252.136nm的吸收线重叠干扰,对混合样中Co和In的含量进行了测定,结果令人满意。 相似文献
100.