全文获取类型
收费全文 | 127998篇 |
免费 | 9136篇 |
国内免费 | 19916篇 |
专业分类
化学 | 105517篇 |
晶体学 | 2721篇 |
力学 | 2901篇 |
综合类 | 1169篇 |
数学 | 15193篇 |
物理学 | 29549篇 |
出版年
2024年 | 186篇 |
2023年 | 1452篇 |
2022年 | 3319篇 |
2021年 | 3313篇 |
2020年 | 3711篇 |
2019年 | 3497篇 |
2018年 | 2948篇 |
2017年 | 4122篇 |
2016年 | 4303篇 |
2015年 | 3621篇 |
2014年 | 4982篇 |
2013年 | 10078篇 |
2012年 | 8501篇 |
2011年 | 7585篇 |
2010年 | 6508篇 |
2009年 | 8518篇 |
2008年 | 8529篇 |
2007年 | 8738篇 |
2006年 | 7962篇 |
2005年 | 6837篇 |
2004年 | 6382篇 |
2003年 | 5315篇 |
2002年 | 6236篇 |
2001年 | 3932篇 |
2000年 | 3646篇 |
1999年 | 3307篇 |
1998年 | 2853篇 |
1997年 | 2293篇 |
1996年 | 1982篇 |
1995年 | 1886篇 |
1994年 | 1672篇 |
1993年 | 1392篇 |
1992年 | 1284篇 |
1991年 | 903篇 |
1990年 | 721篇 |
1989年 | 689篇 |
1988年 | 532篇 |
1987年 | 392篇 |
1986年 | 349篇 |
1985年 | 325篇 |
1984年 | 311篇 |
1983年 | 167篇 |
1982年 | 258篇 |
1981年 | 243篇 |
1980年 | 241篇 |
1979年 | 236篇 |
1978年 | 208篇 |
1977年 | 160篇 |
1976年 | 130篇 |
1973年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
双(十二烷基亚磺酰)乙烷溶剂萃取钯及其机理的研究 总被引:2,自引:0,他引:2
本文研究用双(十二烷基亚磺酰)乙烷萃取钯的性能,在KI存在下从7mol/L盐酸介质中用含有BDSE的氯仿能定量萃取钯,有机的钯可被硫脲或氨溶液反萃继之用TMK-TritonX-100光度法测定,研究了萃取的最佳条件及干扰情况,斜率法测得萃合物组成为Pd:I:BDSE=1:2:1,红外光谱证实萃合物中BDSE的二个亚砜以硫原子与钯配位,萃合物为异位体络合物,提出了选择性萃取分离钯的新方法。 相似文献
992.
Summary.
We consider a discontinuous Galerkin finite element method
applied in time to a model Volterra equation of the second kind.
A residual-based computable
Galerkin-error estimate is derived
for .
This estimate does not explicitly
contain the time step and therefore the time step
control must be based
on a heuristic criterion, the estimate can then be used to
demonstrate the integrity, or otherwise, of the finite element
solution. After performing some numerical experiments
we conclude that this approach is at least competetive
with classical discretizations since it is
computationally simple to implement,
but has the added advantage of
reliable error feedback.
Received June 25, 1995 相似文献
993.
Glucose, maltose, sucrose, lactose, ethanol and urea concentrations were monitored simultaneously during the cultivation of Escherichia coli and Saccharomyces cerevisiae by means of enzyme field effect transistors (EnFETs) applying glucose dehydrogenase (GDH), maltase (MAL)/GDH, invertase (INV)/GDH, β-galactosidase (β-GAL)/galactosedehydrogenase (GALDH), alcoholdehydrogenase (ADH)/aldehydedehydrogenase (ALDH), and urease. These enzymes were (co)immobilized on the pH sensitive gates of an eight-FET array. The FET array was integrated in a commercial FIA system. 相似文献
994.
Michael Bildhauer 《manuscripta mathematica》1998,97(3):389-406
H?lder continuity up to the free boundary is proved for minimizing solutions if they meet the supporting surface in an angle
which is bounded away from zero. The problem is localized by proving the continuity of the distance function, a result which
is also true for stationary points.
Received: 14 April 1998 相似文献
995.
996.
997.
Summary. A third-order accurate Godunov-type scheme for the approximate solution of hyperbolic systems of conservation laws is presented.
Its two main ingredients include: 1. A non-oscillatory piecewise-quadratic reconstruction of pointvalues from their given
cell averages; and 2. A central differencing based on staggered evolution of the reconstructed cell averages. This results in a third-order central scheme, an extension along the lines
of the second-order central scheme of Nessyahu and Tadmor \cite{NT}. The scalar scheme is non-oscillatory (and hence – convergent),
in the sense that it does not increase the number of initial extrema (– as does the exact entropy solution operator). Extension to systems is carried out by componentwise application of the scalar framework. In particular, we have the advantage that, unlike upwind schemes, no (approximate) Riemann
solvers, field-by-field characteristic decompositions, etc., are required. Numerical experiments confirm the high-resolution
content of the proposed scheme. Thus, a considerable amount of simplicity and robustness is gained while retaining the expected
third-order resolution.
Received April 10, 1996 / Revised version received January 20, 1997 相似文献
998.
999.
本文报导了聚4-氨基联苯的电化学合成,测定了它的ESR、IR及紫外可见光谱。聚合物在THF、DMF和DMSO中能全部溶解。界面移动法测得聚4-氨基联苯的DMF饱和溶液中正离子的迁移率为1.48×10~(-8)m~2·S~(-1)·V~(-1)。 相似文献
1000.