全文获取类型
收费全文 | 46909篇 |
免费 | 12272篇 |
国内免费 | 4046篇 |
专业分类
化学 | 49165篇 |
晶体学 | 516篇 |
力学 | 1197篇 |
综合类 | 227篇 |
数学 | 3773篇 |
物理学 | 8349篇 |
出版年
2024年 | 18篇 |
2023年 | 299篇 |
2022年 | 387篇 |
2021年 | 707篇 |
2020年 | 1859篇 |
2019年 | 3200篇 |
2018年 | 1576篇 |
2017年 | 1254篇 |
2016年 | 4071篇 |
2015年 | 4334篇 |
2014年 | 4383篇 |
2013年 | 5191篇 |
2012年 | 4392篇 |
2011年 | 3723篇 |
2010年 | 4021篇 |
2009年 | 3921篇 |
2008年 | 3570篇 |
2007年 | 2803篇 |
2006年 | 2397篇 |
2005年 | 2388篇 |
2004年 | 1926篇 |
2003年 | 1564篇 |
2002年 | 1220篇 |
2001年 | 1061篇 |
2000年 | 740篇 |
1999年 | 374篇 |
1998年 | 258篇 |
1997年 | 240篇 |
1996年 | 216篇 |
1995年 | 207篇 |
1994年 | 153篇 |
1993年 | 137篇 |
1992年 | 113篇 |
1991年 | 108篇 |
1990年 | 79篇 |
1989年 | 54篇 |
1988年 | 67篇 |
1987年 | 40篇 |
1986年 | 44篇 |
1985年 | 42篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 4篇 |
1965年 | 3篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Marija argonja Darko Mekterovi Paula
urga Jagoda Ravli‐Gulan Iva Bogdanovi Radovi Gordana
auhar 《X射线光谱测定》2021,50(1):68-79
During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m3, respectively, whereas in the nearby city, daily PM2.5 concentrations are on average 11 μg/m3. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded. 相似文献
2.
Mathematical Programming - We seek tight bounds on the viable parallelism in asynchronous implementations of coordinate descent that achieves linear speedup. We focus on asynchronous coordinate... 相似文献
3.
通过引入参数,构造了一个全平面上的、含双曲函数的非齐次核函数。利用正切函数的有理分式展开,建立了最佳常数因子与正切函数高阶导数相关联的Hilbert型积分不等式。 作为应用,通过赋予参数不同的值,建立了一些有意义的特殊结果。 相似文献
4.
In this article a coupled version of the improved divergence‐free‐condition compensated method will be proposed to simulate time‐varying geometries by direct forcing immersed boundary method. The proposed method can be seen as a quasi‐multi‐moment framework due to the fact that the momentum equations are discretized by both cell‐centered and cell‐face velocity. For simulating time‐varying geometries, a semi‐implicit iterative method is proposed for calculating the direct forcing terms. Treatments for suppressing spurious force oscillations, calculating drag/lift forces, and evaluating velocity and pressure for freshly cells will also be addressed. In order to show the applicability and accuracy, analytical as well as benchmark problems will be investigated by the present framework and compared with other numerical and experimental results. 相似文献
5.
Journal of Algebraic Combinatorics - APR tilts for path algebra kQ can be realized as the mutation of the quiver Q in $${\mathbb Z}Q$$ with respect to the translation. In this paper, we show that... 相似文献
6.
Miao Xiu-feng Xu Yao-qun Yao Feng-ge 《International Journal of Theoretical Physics》2021,60(7):2604-2612
International Journal of Theoretical Physics - This paper mainly studied the observer design of Lipschitz stochastic discrete system. For the first time, generalized Lipschitz conditions are... 相似文献
7.
Science China Mathematics - In this paper, we obtain a necessary and sufficient condition for a U(n)-invariant complex Finsler metric F on domains in ?n to be strongly convex, which also... 相似文献
8.
We generalize the P(N)-graded Lie superalgebras of Martinez-Zelmanov. This generalization is not so restrictive but suffcient enough so that we are able to have a classification for this generalized P(N)-graded Lie superalgebras. Our result is that the generalized P(N)-graded Lie super-algebra L is centrally isogenous to a matrix Lie superalgebra coordinated by an associative superalgebra with a super-involution. Moreover, L is P(N)-graded if and only if the coordinate algebra R is commutative and the super-involution is trivial. This recovers Martinez-Zelmanov's theorem for type P(N). We also obtain a generalization of Kac's coordinatization via Tits-Kantor-Koecher construction. Actually, the motivation of this generalization comes from the Fermionic-Bosonic module construction. 相似文献
9.
Song Zi-Long Zhu Yun Liu Jing-Rui Guo Shu-Ke Gu Yu-Cheng Han Xinya Dong Hong-Qiang Sun Qi Zhang Wei-Hua Zhang Ming-Zhi 《Molecular diversity》2021,25(1):205-221
Molecular Diversity - Based on the strategy of diversity-oriented synthesis and the structures of natural product pimprinine and streptochlorin, two series of novel pimprinine derivatives... 相似文献
10.