全文获取类型
收费全文 | 1482篇 |
免费 | 33篇 |
国内免费 | 14篇 |
专业分类
化学 | 1051篇 |
晶体学 | 11篇 |
力学 | 63篇 |
数学 | 160篇 |
物理学 | 244篇 |
出版年
2023年 | 11篇 |
2022年 | 16篇 |
2021年 | 26篇 |
2020年 | 24篇 |
2019年 | 26篇 |
2018年 | 25篇 |
2017年 | 13篇 |
2016年 | 25篇 |
2015年 | 22篇 |
2014年 | 46篇 |
2013年 | 50篇 |
2012年 | 70篇 |
2011年 | 96篇 |
2010年 | 69篇 |
2009年 | 52篇 |
2008年 | 99篇 |
2007年 | 86篇 |
2006年 | 81篇 |
2005年 | 69篇 |
2004年 | 75篇 |
2003年 | 78篇 |
2002年 | 58篇 |
2001年 | 24篇 |
2000年 | 28篇 |
1999年 | 12篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 17篇 |
1992年 | 9篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 19篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1975年 | 9篇 |
1970年 | 7篇 |
1969年 | 6篇 |
1967年 | 7篇 |
排序方式: 共有1529条查询结果,搜索用时 5 毫秒
91.
The short and efficient asymmetric synthesis of (-)-1-hydroxyquinolizidinone was achieved in seven steps and 25.2% overall yield from readily available 5-chloropentanal. It is a key intermediate in the formal syntheses of (-)-homopumilotoxin 223G and (-)-epiquinamide. 相似文献
92.
The possibility of coulometric titrations of cysteine, 2-thio-uracil, 6-mercaptopurine, and 6-thioguanine with iodine and bromine in methanol and with bromine in acetic acid has been investigated. Conditions have been found for the direct titration of the test substances with iodine in methanol based on their 1-electron oxidation to the corresponding disulphides and for their direct and indirect determination with bromine in acetic acid based on their 6-electron oxidation to the corresponding sulphonic acids.On leave from Department of Analytical Chemistry, Charles University, Prague, Czechoslovakia 相似文献
93.
94.
In this study, through the method of rapid controlled precipitation (RCP), the influence of temperature and dissolved CO2 on the scaling capacity of mineral water in the presence of copper and zinc ions was studied in laboratory experiments. The
results indicated that with a rise in temperature or concentration of dissolved CO2, the scaling time of Salvetat water greatly decreased and the rate of precipitation considerably increased; therefore, the
minimum dosage of copper or zinc ion for achieving total inhibition of scaling needed to be increased, which would provide
better guidance for practical use of metal ions in inhibiting the scaling of drinking water. 相似文献
95.
96.
In order to evaluate the behavior of three probabilistic location set covering models we propose a new method that allows the ex-post measurement of the so called minimum local reliability level, both under the independence and under the dependence assumption. We show experimentally, by means of a set of test problems, that the proposed loss-system version of Ball and Lin's model (1993) does almost always achieve the required reliability level. Moreover, if we compare this new version with the other two already known probabilistic models and consider as a second additional criteria the least number of required vehicles, we show that the new version has a better behavior both under the independence and the dependence assumption. In this paper we further propose a new model with the aim of reducing the number of required vehicles while satisfying the fixed reliability level. Our new model is formulated like Ball and Lin's model incorporating the servers workload estimate of the Binomial PLSCP of ReVelle and Hogan (1988). Finally, we check the precision of our ex-post evaluation method over the four considered models through a simulation study. 相似文献
97.
Here we describe the synthesis of a mesoporous composite material using the self-assembly of well defined tubular building blocks obtained from the exfoliation of [Nb6O17(4-)]n sheets. 相似文献
98.
Franck Leprévost 《manuscripta mathematica》1992,75(1):303-326
We construct here, forl=2g
2
+2g+1 or2g
2
+3g+1, a family with one parameter of hyperelliptic curves of genusg overQ such that its jacobian has a point of orderl rational overQ(t). Wheng=2 the method allows to construct, forl=17, 19 or 21 a family with one parameter of hyperelliptic curves of genus 2 overQ such that its jacobian has a point of orderl rational overQ(t).
相似文献
99.
100.