全文获取类型
收费全文 | 28233篇 |
免费 | 4777篇 |
国内免费 | 4555篇 |
专业分类
化学 | 22034篇 |
晶体学 | 454篇 |
力学 | 1349篇 |
综合类 | 327篇 |
数学 | 3160篇 |
物理学 | 10241篇 |
出版年
2024年 | 37篇 |
2023年 | 517篇 |
2022年 | 742篇 |
2021年 | 954篇 |
2020年 | 1131篇 |
2019年 | 1151篇 |
2018年 | 952篇 |
2017年 | 1033篇 |
2016年 | 1488篇 |
2015年 | 1537篇 |
2014年 | 1915篇 |
2013年 | 2362篇 |
2012年 | 2798篇 |
2011年 | 2856篇 |
2010年 | 2109篇 |
2009年 | 1884篇 |
2008年 | 2150篇 |
2007年 | 1853篇 |
2006年 | 1709篇 |
2005年 | 1401篇 |
2004年 | 1094篇 |
2003年 | 862篇 |
2002年 | 850篇 |
2001年 | 767篇 |
2000年 | 532篇 |
1999年 | 544篇 |
1998年 | 354篇 |
1997年 | 273篇 |
1996年 | 247篇 |
1995年 | 244篇 |
1994年 | 192篇 |
1993年 | 174篇 |
1992年 | 147篇 |
1991年 | 131篇 |
1990年 | 112篇 |
1989年 | 96篇 |
1988年 | 61篇 |
1987年 | 59篇 |
1986年 | 64篇 |
1985年 | 40篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
JingXiaWANG ChengYouKAN DeShanLIU 《中国化学快报》2004,15(10):1161-1163
Two novel polymerizable dyes with anthraquinone residue have been prepared, and their structures were characterized by FTIR, ^1HNMR and EA. 相似文献
102.
Zhaoyang Yin 《Monatshefte für Mathematik》2004,141(4):337-344
We prove under quite general assumptions the existence of a bounded positive solution to the semilinear Schrödinger equation in a two-dimensional exterior domain. 相似文献
103.
104.
105.
106.
The compression behaviour of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state is determined by fitting the experimental data according to the Birch-Murnaghan equation. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa. Within the pressure range from zero to the experimental one, the pressure-induced structural relaxation is reversible. 相似文献
107.
神经网络法计算镉(Ⅱ),羟基及碳酸根三元体系的形态分布 总被引:2,自引:0,他引:2
采用前馈线笥网络BP算法,计算了Cd62+-OH^-CO^2-3三元体系的累积稳定常数。用Hopfield反馈网络研究了体系中络合物的形态分布。溶液中溶解的CO2对lgβ1的计算结果有重要影响,对lgβ2,lgβ3,lgβ4的结果影响不大。 相似文献
108.
109.
110.
We study the expected delay in cyclic polling models with general ‘branching-type’ service disciplines. For this class of
models, which contains models with exhaustive and gated service as special cases, we obtain closed-form expressions for the
expected delay under standard heavy-traffic scalings. We identify a single parameter associated with the service discipline
at each queue, which we call the ‘exhaustiveness’. We show that the scaled expected delay figures depend on the service policies
at the queues only through the exhaustiveness of each of the service disciplines. This implies that the influence of different
service disciplines, but with the same exhaustiveness, on the expected delays at the queues becomes the same when the system
reaches saturation. This observation leads to a new classification of the service disciplines. In addition, we show monotonicity
of the scaled expected delays with respect to the exhaustiveness of the service disciplines. This induces a complete ordering
in terms of efficiency of the service disciplines. The results also lead to new rules for optimization of the system performance
with respect to the service disciplines at the queues. Further, the exact asymptotic results suggest simple expected waiting-time
approximations for polling models in heavy traffic. Numerical experiments show that the accuracy of the approximations is
excellent for practical heavy-traffic scenarios.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献