全文获取类型
收费全文 | 9365篇 |
免费 | 1165篇 |
国内免费 | 1126篇 |
专业分类
化学 | 7916篇 |
晶体学 | 296篇 |
力学 | 250篇 |
综合类 | 107篇 |
数学 | 539篇 |
物理学 | 2548篇 |
出版年
2024年 | 14篇 |
2023年 | 115篇 |
2022年 | 365篇 |
2021年 | 398篇 |
2020年 | 457篇 |
2019年 | 379篇 |
2018年 | 322篇 |
2017年 | 312篇 |
2016年 | 481篇 |
2015年 | 418篇 |
2014年 | 399篇 |
2013年 | 765篇 |
2012年 | 443篇 |
2011年 | 528篇 |
2010年 | 435篇 |
2009年 | 466篇 |
2008年 | 482篇 |
2007年 | 607篇 |
2006年 | 578篇 |
2005年 | 504篇 |
2004年 | 464篇 |
2003年 | 384篇 |
2002年 | 337篇 |
2001年 | 243篇 |
2000年 | 236篇 |
1999年 | 206篇 |
1998年 | 176篇 |
1997年 | 193篇 |
1996年 | 164篇 |
1995年 | 114篇 |
1994年 | 126篇 |
1993年 | 94篇 |
1992年 | 97篇 |
1991年 | 51篇 |
1990年 | 53篇 |
1989年 | 46篇 |
1988年 | 31篇 |
1987年 | 35篇 |
1986年 | 27篇 |
1985年 | 23篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1972年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
101.
Om Prakash Ajay Kumar Richa Prakash Rosa M. Claramunt Ibon Alkorta José Elguero 《Tetrahedron》2005,61(27):6642-6651
Treatment of α,β-unsaturated carbonyl compounds, obtained by the reaction of DHA and aromatic (or heteroaromatic) aldehydes, with o-aminothiophenol results in the formation of 1,5-benzothiazepines and/or 1,4-benzothiazines depending upon the reaction conditions and structure of the aldehydes. The products were characterized by the combined use of multinuclear 1D and 2D NMR and GIAO/DFT calculations of 1H, 13C and 15N chemical shifts. The tautomerism of these compounds in solution was determined, they have an exocyclic CC double bond. 相似文献
102.
Thermodynamic and Equilibrium Composition Analysis of Using Iron Oxide as an Oxygen Carrier in Nonflame Combustion Technology 总被引:1,自引:0,他引:1
Jiayu Xin Hua Wang* Fang He Zhimin Zhang Faculty of Materials Metallurgical Engineering Kunming University of Science Technology Kunming China 《天然气化学杂志》2005,14(4)
1. Introduction The utilization of fossil fuels causes serious neg- ative impacts on the environment and human life. There are many pollutants such as SOx, NOx and CO2 emission produced from the combustion of coal, oil and natural gas. It has been known for more than 100 years that CO2 is a greenhouse gas and that the release of CO2 from fossil fuel combustion may affect the climate of the earth. In the last years the concern over the aspects of an increased release of greenhouse gases has… 相似文献
103.
Thermodynamic and Equilibrium Composition of Using Iron Oxide as an Oxygen Carrier Nonflame Combustion Technology Analysis in
下载免费PDF全文
![点击此处可从《天然气化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
本文介绍了一种新的燃烧体系--熔融盐循环热载体无烟燃烧技术。这种燃烧体系杜绝环境污染气体NOx和CO2的排放,可以实现真正零排放的目标。计算了以Fe2O3作为氧载体的无烟燃烧体系的热力学参数。用最小吉布斯自由能原则,分析了Fe2O3与CH4的平衡组成。分析表明,如果要想在产物中产生高纯度的CH4完全氧化产物CO2和H2O,Fe2O3与CH4必须达到高摩尔比,如果Fe2O3的量不足,就会产生较多的部分氧化产物如CO,H2甚至C 相似文献
104.
105.
106.
107.
A highly sensitive and selective liquid chromatography-mass spectrometry (LC-MS) method has been developed for the determination of epirubicin in serum and cell specimens using daunorubicin as an internal standard. Using atmospheric pressure chemical ionisation (APCI), the epirubicin metabolites were readily distinguishable by their fragmentation pattern in the mass spectrometer. Selected reaction monitoring (SRM) mode was employed for quantitation of epirubicin and the metabolites. Following extraction, chromatography was performed on a C18 column with a mobile phase consisting of water-acetonitrile-formic acid, pH 3.2, with a flow rate of 200 μl/min. The limit of detection (LOD) and the limit of quantitation (LOQ) of this method in serum were determined to be 1.0 and 2.5 ng/ml, respectively. Linearity of the method was verified over the concentration range of 2.5-2000 ng/ml, with a high correlation coefficient (R2 ≥ 0.998). For the extraction procedure, an aliquot of 500 μl serum, spiked with internal standard, was extracted using a chloroform-2-isopropanol (2:1, v/v) mixture. The method has been applied to the analysis of epirubicin in cancer cell samples and the identification of known and unknown metabolites in clinical trial patient serum samples. 相似文献
108.
近年来化学复合镀技术在工业中应用日益广泛 ,本文运用SEM、AES和XPS等手段对用化学复合镀制得的Ni P PTFE镀层的结构和组分进行了分析 ,并就其耐腐蚀性能与前期得到的Ni Sn P[1 ] 、Cu Sn P[2 ] 、Ni P CeO2 [3] 、Ni P SiO2 [4] 镀层进行了比较 ,结果表明 :含量一定的PTFE(聚四氟乙烯 )的共存增强镀层的耐腐蚀性及镀层表面的润滑性。1 实验部分1 1 仪器日产D/MAXⅢA型X 射线衍射仪 ,铜靶 ,管压 2 5kV ,电流 1 0mA。国产JJC 1型润滑湿角测量仪。美国PERKIN ELMERP… 相似文献
109.
Chemical modification of L-asparaginase with N, O-carboxymethyl chitosan and its effects on plasma half-life and other properties 总被引:1,自引:0,他引:1
E.coli L-asparaginase,an antitumor enzyme,was chemically modified with N,O-carboxymethyl chitosan to lower its artigenicity and increase its plasma half-life.The results showed that the modified L-asparaginase has almost the same apparent Km value as that of native enzyme.The modified L-asparaginase also showed a higher protease stability against trypsin and a-chymotrypsin.After being modified,the enzyme exhibited the complete loss of antigenicity towards antiasparaginase serum.In addition,the higher the molecular weight of modifying reagents,the better the effects on reduction of antigenicity.When tested in vivo,the plasma half-life of the modified enzyme (t1/2=40 h) was over 33 times longer than that of the native enzyme (t1/2=1.2 h). 相似文献
110.
A new analytical method for the determination of uric acid (UA) by the perturbation of UA on the Belousov-Zhabotinsky oscillating reaction is proposed. The method is based on the linear relationship between the changes in the oscillating period and the concentration of UA. The calibration curve is linear over the range of 2.0 × 10−5 to 5.0 × 10−4 M, with a detecting limit of 3.28 × 10−6 M. The method features good precision (R.S.D.: 3.59%) and excellent throughput (10 samples h−1). The possible mechanism of the perturbation of UA on the oscillating reaction is discussed. 相似文献