全文获取类型
收费全文 | 7245篇 |
免费 | 1566篇 |
国内免费 | 587篇 |
专业分类
化学 | 3822篇 |
晶体学 | 38篇 |
力学 | 86篇 |
综合类 | 29篇 |
数学 | 70篇 |
物理学 | 5353篇 |
出版年
2024年 | 5篇 |
2023年 | 61篇 |
2022年 | 251篇 |
2021年 | 333篇 |
2020年 | 378篇 |
2019年 | 323篇 |
2018年 | 273篇 |
2017年 | 389篇 |
2016年 | 439篇 |
2015年 | 398篇 |
2014年 | 721篇 |
2013年 | 600篇 |
2012年 | 580篇 |
2011年 | 551篇 |
2010年 | 441篇 |
2009年 | 474篇 |
2008年 | 450篇 |
2007年 | 461篇 |
2006年 | 312篇 |
2005年 | 288篇 |
2004年 | 213篇 |
2003年 | 183篇 |
2002年 | 144篇 |
2001年 | 131篇 |
2000年 | 123篇 |
1999年 | 105篇 |
1998年 | 101篇 |
1997年 | 102篇 |
1996年 | 71篇 |
1995年 | 69篇 |
1994年 | 54篇 |
1993年 | 42篇 |
1992年 | 41篇 |
1991年 | 40篇 |
1990年 | 43篇 |
1989年 | 29篇 |
1988年 | 30篇 |
1987年 | 33篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 9篇 |
1982年 | 20篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有9398条查询结果,搜索用时 578 毫秒
991.
The use of a photoionization detector (PID) coupled to a glass capillary gas chromatography (GC2) separation system for the detection of carcinogenic nitrosamines was investigated. The components analyzed gave a linear response with a lower detection limit of 50 to 100 pg with the 10.2 eV ionization source. No detector response was obtained with an ionization energy of 9.5 eV. Chromatography of meat extracts indicated their complex molecular composition. Simple liquid chromatographic cleaning procedures significantly decreased the complexity of these samples, but not sufficiently for the accurate quantition of nitrosamine components. 相似文献
992.
Summary A simple, corrosion-resistant and non-destructive flow cell optimized for laser induced photoacoustic spectroscopic detection of HPLC effluents is described. The characteristics and analytical figures of merit of the flow cell are presented. Application of the flow cell to the detection of polynuclear aromatic hydrocarbons in HPLC effluent is demonstrated. Limits of detection were on the order of tenths of parts per million. Comparisons with the conventional UV absorbance detector and among various laser powers are discussed. 相似文献
993.
光电精确制导战术武器的发展 总被引:4,自引:0,他引:4
本文简述光电精确制导技术武器发展的基本特征,探讨新一代自动寻的精确制导战术武器发展的趋势和技术途径,分析精确制导战术武器的关键技术。 相似文献
994.
On MR lymphography, a new approach to the lung hilar and mediastinal nodes was developed in an animal model. Five rabbits were made to inhale iron colloid (cideferron) that was nebulized to aerosol. Two days after inhalation of the agent, the mediastinal lymph nodes decreased in signal on SE 2000/30 and SE 2000/60 images and proved to have iron on histological evaluation, whereas the popliteal nodes did not have any iron. Experimental results indicate that inhalational administration can deliver the agent to the pulmonary lymphatic system and has the potential of lung hilar and mediastinal MR lymphography. 相似文献
995.
996.
L. Ghaoui E. Dessai W. E. Wentworth S. Weisner A. Zlatkis E. C. M. Chen 《Chromatographia》1985,20(2):75-78
Summary Many of the isomers of fluorocarbons have boiling points which are less than one degree different. Thus it is necessary to use some other basis for their separation on a chromatographic column. One such possibility is gas-solid chromatography. It has been demonstrated that an alumina porous-layer open-tubular (PLOT) column is especially well suited for the analysis of fluoroalkanes and fluorobenzenes. This column is useful for the specific application of the measurement of electron attachment properties of these molecules using the electron-capture detector because of thelack of column bleed. 相似文献
997.
998.
999.
1000.