全文获取类型
收费全文 | 17736篇 |
免费 | 2864篇 |
国内免费 | 4485篇 |
专业分类
化学 | 12960篇 |
晶体学 | 485篇 |
力学 | 1110篇 |
综合类 | 386篇 |
数学 | 2385篇 |
物理学 | 7759篇 |
出版年
2024年 | 45篇 |
2023年 | 288篇 |
2022年 | 677篇 |
2021年 | 630篇 |
2020年 | 656篇 |
2019年 | 674篇 |
2018年 | 561篇 |
2017年 | 709篇 |
2016年 | 724篇 |
2015年 | 879篇 |
2014年 | 1132篇 |
2013年 | 1361篇 |
2012年 | 1553篇 |
2011年 | 1516篇 |
2010年 | 1278篇 |
2009年 | 1298篇 |
2008年 | 1526篇 |
2007年 | 1312篇 |
2006年 | 1233篇 |
2005年 | 1086篇 |
2004年 | 824篇 |
2003年 | 610篇 |
2002年 | 602篇 |
2001年 | 598篇 |
2000年 | 645篇 |
1999年 | 437篇 |
1998年 | 274篇 |
1997年 | 237篇 |
1996年 | 242篇 |
1995年 | 218篇 |
1994年 | 186篇 |
1993年 | 174篇 |
1992年 | 161篇 |
1991年 | 100篇 |
1990年 | 108篇 |
1989年 | 83篇 |
1988年 | 82篇 |
1987年 | 60篇 |
1986年 | 48篇 |
1985年 | 50篇 |
1984年 | 35篇 |
1983年 | 32篇 |
1982年 | 37篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
The aggregation of dansyl chloride (DNS-Cl) in acetone has been studied in detail by steady-state fluorescence techniques.It has been demonstrated that DNS-Cl is stable in acetone during purification and aggregation study processes.The aggregates are not solvolyzed in acetone,and do not take part n any chemical reactions either.It has been found that DNS-Cl tends to aggregate even when its concentration is much lower than its solubility in acetone.The aggregation is reversible,and both the aggregation and the deaggregation are very slow processes.Introduction of SDS has a positive effect upon the formation and stabilization of the aggregates. 相似文献
42.
43.
44.
I. G. Yudelevich B. I. Zaksas Ye. A. Petrova A. S. Cherevko 《Fresenius' Journal of Analytical Chemistry》1991,340(9):560-563
Summary A method for the atomic emission spectrometric analysis of air and water with inductively coupled and two-jet direct current plasmas has been developed. The method has been applied to the determination of impurity contents with good accuracy and sensitivity. 相似文献
45.
在本文中,我们提出了双凹规划问题和更一般的广义凹规划问题。我们给出了双凹规划问题的整体最优性条件,并构造了一个有限终止外逼近算法。 相似文献
46.
47.
A rapid and sensitive flow-injection spectrophotometric method is proposed for the determination of sulfadiazine and sulfamethoxazole. This method is based on the diazotization of sulfonamide with sodium nitrite, and a coupling reaction of the diazo-compound with alpha-naphthylamine. The optimum experimental conditions are obtained by using the controlled and weighted centroid simplex method. The linear ranges for the determination of sulfadiazine and sulfamethoxazole are 0.2-20 microg ml(-1) and 0.1-20 microg ml(-1), and their detection limits are 0.06 microg ml(-1) and 0.05 microg ml(-1), respectively, and the sampling frequency is 130 samples per hour. The method has been used to determine sulfadiazine and sulfamethoxazole in pharmaceuticals and urine without separation. The results are in agreement with those obtained by a high-performance liquid chromatograph technique at the 95% confidence level. 相似文献
48.
49.
In this paper we consider an obstacle control problem where the state satisfies a quasilinear elliptic variational inequality and the control function is the obstacle. The state is chosen to be close to the desire profile while the H2 norms of the obstacle is not too large. Existence and necessary conditions for the optimal control are established. 相似文献
50.
In this paper we investigate the
probabilistic linear $(n,\delta)$-widths and $p$-average linear
$n$-widths of the Sobolev space $W^r_2$ equipped with the Gaussian
measure $\mu$ in the $L_{\infty}$-norm, and determine the
asymptotic equalities
\begin{eqnarray*}
\lambda_{n,\delta}(W^r_2,\mu,L_{\infty})
&\asymp&\frac{\sqrt{\ln
(n/\delta)}}{n^{r+(s-1)/2}},\\[3pt]
\lambda^{(a)}_n(W^r_2,\mu,L_{\infty})_p &\asymp&\frac{\sqrt{\ln
n}}{n^{r+(s-1)/2}}, \qquad 0 < p < \infty.
\end{eqnarray*} 相似文献