全文获取类型
收费全文 | 29582篇 |
免费 | 5000篇 |
国内免费 | 6666篇 |
专业分类
化学 | 12033篇 |
晶体学 | 859篇 |
力学 | 1229篇 |
综合类 | 581篇 |
数学 | 2354篇 |
物理学 | 8721篇 |
无线电 | 15471篇 |
出版年
2024年 | 134篇 |
2023年 | 363篇 |
2022年 | 1125篇 |
2021年 | 1096篇 |
2020年 | 956篇 |
2019年 | 862篇 |
2018年 | 815篇 |
2017年 | 1269篇 |
2016年 | 971篇 |
2015年 | 1457篇 |
2014年 | 1778篇 |
2013年 | 2231篇 |
2012年 | 2386篇 |
2011年 | 2569篇 |
2010年 | 2629篇 |
2009年 | 2626篇 |
2008年 | 2797篇 |
2007年 | 2598篇 |
2006年 | 2520篇 |
2005年 | 2095篇 |
2004年 | 1584篇 |
2003年 | 1160篇 |
2002年 | 967篇 |
2001年 | 1008篇 |
2000年 | 1013篇 |
1999年 | 465篇 |
1998年 | 236篇 |
1997年 | 179篇 |
1996年 | 167篇 |
1995年 | 134篇 |
1994年 | 138篇 |
1993年 | 143篇 |
1992年 | 166篇 |
1991年 | 64篇 |
1990年 | 83篇 |
1989年 | 64篇 |
1988年 | 81篇 |
1987年 | 56篇 |
1986年 | 44篇 |
1985年 | 35篇 |
1984年 | 37篇 |
1983年 | 42篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 8篇 |
1979年 | 30篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1971年 | 4篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
81.
由于血液管理对于环境条件的特殊要求,针对血液管理分析提出了将传感技术与RFID技术结合后应用于其中的想法。简要介绍了RFID传感器标签的设计,分析了将其运用于血液管理分析后对加强流程监控、提高工作效率的好处,并主要从血液的出入库管理、跟踪管理、质控管理三个方面详细描述,阐明了方法的可行性。 相似文献
82.
83.
84.
85.
86.
N- aryl substituted benzenesulfamides are often used as heating-sensitive recording material1, thermal printing material2, sensitizer3 and developer4. Moreover, some of the benzenesulfamides have antifungal activities5. Many methods have been described for preparation of sulfamides. They are used to carry out in solvent8 or in solid phase condition9. These methods required solvent or solid support and even required heating or cooling. At the same time, the process of these methods is complex. Now we have developed a new method to prepare N-aryl substituted toluenesulfamides under solvent-free conditions.In recent years, solvent-free technology has gained popularity in organic synthesis. For instance,solidstate reaction and microwave reaction have received considerable attention. Solvent-free synthesis of amides has been reported10-11. This technology has many advantages such as high efficiency and selectivity, easy separation and environmental acceptability. All these merits are in accord with green chemistry's requirements of energy-saving, high efficiency and environmental benefits.In our paper, we used a simple and efficient method for preparing N-aryl substituted toluenesulfamides under solvent-free conditions, as a replacement for classic solvent, which gives many environmental benefits.All reactions were completed at room temperature by co-grinding in an agate mortar for 3-20min and the results are shown in Table 1.In conclusion, we have developed an efficient and convenient method of preparation N-aryl substituted toluenesulfamides in high yields. It symbols an improvement for synthesis of benzenesulfamides. 相似文献
87.
YAN Xiaomin ZHAO Lin SHAO Jianhui TAN Xin SONG Zhengxiao School of Chemical Engineering Technology Tianjin University Tianjin China Slichem Liquid Material Co. Ltd. Shijiazhuang China 《Chinese Journal of Reactive Polymers》2004,(Z1)
1. INTRODUCTION Methionine, namely 2-amido-4-thiomethyl butyric acid with a structure of CH3SCH2CH2CHCOOH, is one of the essential amino acids and has two natural enantionmers, D and L-methionine. The mixture of L- and D-isomers can be used as analeptics or nutritive additives to maintain the equilibrium of amino acids of feed [1,2]. L-methionine can release active methyl and accelerate the synthesis of choline, which further speeds up the conversion of the lipid accumulated in liv… 相似文献
88.
Direct Observation of Non-covalent Complexes for Phosphorylated Flavonoid-protein Interaction by ESI
XiaoLanCHEN TingZHANG HongXiaLIU LingBoQU YouZhuYU YuFenZHAO 《中国化学快报》2004,15(3):343-346
Diethyl flavon-7-yl phosphate was synthesized by modified Atheron-Todd reaction. The result of ESI shows that the phosphated flavonoids possess stronger binding affinities toward proteins such as myoglobin, insulin and lysozyme and are easier to form the non-covalent complexes with them. 相似文献
89.
The First Intramolecular Charge Transfer Transition Based on 2-Ureido-4[1H]-pyrimidinone Binding Module 总被引:1,自引:0,他引:1
The first intramolecular charge transfer transition based on 2-ureido-4[1H]-pyrimidinone binding module was reported. 相似文献
90.
基于改进遗传算法的布局优化子问题 总被引:2,自引:0,他引:2
本针对子问题,构造了布局子问题(关于同构布局等价类)的改进遗传算法。将该算法应用于二维布局优化子问题,数值实验表明该算法能够在很好地保持图元的邻接关系的前提下找到子问题的最优解。由于布局优化问题可分解为有限个子问题,所以利用该算法可以找到整个布局优化问题的全局最优解。 相似文献