全文获取类型
收费全文 | 104346篇 |
免费 | 9767篇 |
国内免费 | 6495篇 |
专业分类
化学 | 44567篇 |
晶体学 | 1887篇 |
力学 | 4655篇 |
综合类 | 425篇 |
数学 | 18259篇 |
物理学 | 50815篇 |
出版年
2023年 | 466篇 |
2022年 | 696篇 |
2021年 | 909篇 |
2020年 | 1495篇 |
2019年 | 1752篇 |
2018年 | 1658篇 |
2017年 | 1613篇 |
2016年 | 1600篇 |
2015年 | 1547篇 |
2014年 | 2225篇 |
2013年 | 3395篇 |
2012年 | 2992篇 |
2011年 | 3441篇 |
2010年 | 3674篇 |
2009年 | 8428篇 |
2008年 | 9293篇 |
2007年 | 8024篇 |
2006年 | 7192篇 |
2005年 | 5242篇 |
2004年 | 4908篇 |
2003年 | 5031篇 |
2002年 | 5479篇 |
2001年 | 4248篇 |
2000年 | 3981篇 |
1999年 | 3746篇 |
1998年 | 3121篇 |
1997年 | 2237篇 |
1996年 | 2063篇 |
1995年 | 2503篇 |
1994年 | 2407篇 |
1993年 | 1800篇 |
1992年 | 1344篇 |
1991年 | 1077篇 |
1990年 | 839篇 |
1989年 | 728篇 |
1988年 | 657篇 |
1987年 | 495篇 |
1985年 | 1002篇 |
1984年 | 670篇 |
1983年 | 519篇 |
1982年 | 678篇 |
1981年 | 828篇 |
1980年 | 740篇 |
1979年 | 579篇 |
1978年 | 592篇 |
1977年 | 541篇 |
1976年 | 546篇 |
1975年 | 320篇 |
1974年 | 358篇 |
1973年 | 465篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The radius of spatial analyticity for solutions of the KdV equation is studied. It is shown that the analyticity radius does not decay faster than as time t goes to infinity. This improves the works of Selberg and da Silva (2017) [30] and Tesfahun (2017) [34]. Our strategy mainly relies on a higher order almost conservation law in Gevrey spaces, which is inspired by the I-method. 相似文献
52.
In this paper we present a-posteriori KAM results for existence of d-dimensional isotropic invariant tori for n-DOF Hamiltonian systems with additional independent first integrals in involution. We carry out a covariant formulation that does not require the use of action-angle variables nor symplectic reduction techniques. The main advantage is that we overcome the curse of dimensionality avoiding the practical shortcomings produced by the use of reduced coordinates, which may cause difficulties and underperformance when quantifying the hypotheses of the KAM theorem in such reduced coordinates. The results include ordinary and (generalized) iso-energetic KAM theorems. The approach is suitable to perform numerical computations and computer assisted proofs. 相似文献
53.
54.
55.
Chaonan Xie Qin Li Gang Han Huan Liu Jien Yang Jincheng Li 《Biomedical chromatography : BMC》2019,33(5)
Tricaine methanesulfonate is one of most commonly used anesthetics in fish during blood sampling, artificial propagation and long‐distance transportation. In this study, an accurate method for the quantitative determination of tricaine in fish samples by a stable isotope dilution assay coupled with high‐performance liquid chromatography–triple quadrupole mass spectrometry was developed. Tricaine‐D5 was synthesized and used as an isotopically labeled internal standard for the determination of tricaine. The analytical performance of the method was validated for tricaine determination in marine fish and freshwater fish. The determination of tricaine was linear in the range of 2.0–200.0 μg L?1. The limit of detection and limit of quantitation for fish muscle tissues were 1.0 and 4.0 μg kg?1, respectively. Good recoveries were obtained in the range of 92.08–97.50%. The inter‐ and intra‐assay relative standard deviations (RSD values) were investigated, and the values were 0.39–3.01 and 0.85–2.77%, respectively. The values of CCα and CCβ were 10.21–10.43 and 10.42–10.87 μg kg?1, respectively. The clearance of MS‐222 from grass carp was further studied using our method. The results demonstrate that MS‐222 could be well absorbed and rapidly eliminated after bath administration. 相似文献
56.
57.
58.
59.
60.