全文获取类型
收费全文 | 9215篇 |
免费 | 178篇 |
国内免费 | 20篇 |
专业分类
化学 | 5744篇 |
晶体学 | 143篇 |
力学 | 198篇 |
数学 | 1325篇 |
物理学 | 2003篇 |
出版年
2020年 | 84篇 |
2019年 | 80篇 |
2016年 | 156篇 |
2015年 | 130篇 |
2014年 | 152篇 |
2013年 | 287篇 |
2012年 | 292篇 |
2011年 | 374篇 |
2010年 | 219篇 |
2009年 | 210篇 |
2008年 | 314篇 |
2007年 | 296篇 |
2006年 | 318篇 |
2005年 | 281篇 |
2004年 | 291篇 |
2003年 | 256篇 |
2002年 | 236篇 |
2001年 | 168篇 |
2000年 | 212篇 |
1999年 | 137篇 |
1998年 | 129篇 |
1997年 | 122篇 |
1996年 | 157篇 |
1995年 | 174篇 |
1994年 | 151篇 |
1993年 | 132篇 |
1992年 | 138篇 |
1991年 | 127篇 |
1990年 | 122篇 |
1989年 | 140篇 |
1988年 | 146篇 |
1987年 | 126篇 |
1986年 | 123篇 |
1985年 | 151篇 |
1984年 | 109篇 |
1983年 | 143篇 |
1982年 | 145篇 |
1981年 | 153篇 |
1980年 | 129篇 |
1979年 | 153篇 |
1978年 | 135篇 |
1977年 | 119篇 |
1976年 | 111篇 |
1975年 | 91篇 |
1974年 | 105篇 |
1973年 | 109篇 |
1972年 | 65篇 |
1971年 | 80篇 |
1970年 | 66篇 |
1968年 | 65篇 |
排序方式: 共有9413条查询结果,搜索用时 15 毫秒
41.
Wolfgang Werner 《Fresenius' Journal of Analytical Chemistry》1992,342(10):783-786
Summary Systematic quality assurance, e.g. in accordance with the provisions of ISO 9000, requires not only the targeted use of quality as a management tool, but also a revised attitude to operational procedures. Although sophisticated checking of the final results of a procedure (e.g. results of analyses, sales products, reports) meets the legal requirements and often also the customers' requirements, this misses the chance of being able to influence the quality of a final result at the earliest possible stage. It is then only possible subsequently to take the uneconomic decision as to whether the result of the work is useable or must be discarded or the object reworked. Within quality assurance, all operations are to be considered as processes with the aim of arriving at a statistically controlled process. The advantages of statistical process control are explained by way of examples from analytical procedures and production. The status of internal audits is explained as it interrelates with process control. 相似文献
42.
43.
44.
45.
46.
Kurt V. Schenker Wolfgang Von Philipsborn C. Anderson Evans Werner Skuballa Georg-Alexander Hoyer 《Helvetica chimica acta》1986,69(7):1718-1727
The configurations of the 5,6-double bond in the carbacyclins iloprost ( 3 ; (E)) and isoiloprost ( 4 ; (Z)) are based on a complete assignment of the 13C and 1H resonances determined by 1D and 2D 13C-NMR and 1H-NMR methods. 相似文献
47.
48.
49.
Viorica Lopez-Avila Richard Young Werner F. Beckert 《Journal of separation science》1997,20(9):487-492
This paper describes the extraction of 49 organophosphorus pesti-cides (OPPs) from water samples using solid-phase microextraction (SPME). Three fibers, including a 15-μm XAD-coated fiber, a 85-μm polyacrylate-coated fiber, and a 30-μm polydimethylsilox-ane-coated fiber (PDMS), were evaluated here. The effects of stirring and the addition of NaCl to the sample were examined for the polyacrylate-coated fiber. The precision of the technique was examined for all three fibers and the extraction kinetics were investigated using the XAD- and polyacrylate-coated fibers. With some exceptions, the XAD- and polyacrylate-coated fibers performed better than the PDMS-coated fiber. The superiority of the XAD-nd polyacrylate-coated fiber. The superiority of the XAD- and polyacrylate-coated fibers over the PDMS-coated fibers can be attribuibuted to the aromatic functionalities of the XAD and the polar functionalities in the polyacrylate. The relatively high percent RSDs indicate that the SPME technique needs to be further refined before it can be used for anything other than screening. A more effective form of agitation than mechanical stirring may be neccessary to reduce variability and achieve a faster equilibrium between the sample and the SPME fiber. 相似文献
50.