全文获取类型
收费全文 | 69403篇 |
免费 | 15473篇 |
国内免费 | 7103篇 |
专业分类
化学 | 65677篇 |
晶体学 | 835篇 |
力学 | 2376篇 |
综合类 | 401篇 |
数学 | 6210篇 |
物理学 | 16480篇 |
出版年
2024年 | 108篇 |
2023年 | 767篇 |
2022年 | 1478篇 |
2021年 | 1591篇 |
2020年 | 2649篇 |
2019年 | 3953篇 |
2018年 | 2253篇 |
2017年 | 1971篇 |
2016年 | 5033篇 |
2015年 | 5307篇 |
2014年 | 5703篇 |
2013年 | 6744篇 |
2012年 | 6363篇 |
2011年 | 5637篇 |
2010年 | 5272篇 |
2009年 | 5095篇 |
2008年 | 4757篇 |
2007年 | 3858篇 |
2006年 | 3409篇 |
2005年 | 3130篇 |
2004年 | 2629篇 |
2003年 | 2234篇 |
2002年 | 3018篇 |
2001年 | 2220篇 |
2000年 | 1933篇 |
1999年 | 1101篇 |
1998年 | 560篇 |
1997年 | 470篇 |
1996年 | 416篇 |
1995年 | 383篇 |
1994年 | 307篇 |
1993年 | 289篇 |
1992年 | 210篇 |
1991年 | 200篇 |
1990年 | 176篇 |
1989年 | 162篇 |
1988年 | 118篇 |
1987年 | 88篇 |
1986年 | 90篇 |
1985年 | 74篇 |
1984年 | 46篇 |
1983年 | 36篇 |
1982年 | 36篇 |
1981年 | 24篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
2.
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients... 相似文献
3.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
4.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed... 相似文献
5.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
6.
A graphic sequence π =(d1, d2,..., dn) is said to be forcibly k-edge-connected if every realization of π is k-edge-connected. In this paper, we obtain a new sufficient degree condition for π to be forcibly k-edgeconnected. We also show that this new sufficient degree condition implies a strongest monotone degree condition for π to be forcibly 2-edge-connected and a conjecture about a strongest monotone degree condition for π to be forcibly 3-edge-connected due to... 相似文献
7.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
8.
Nonlinear Dynamics - The nonlinear modes of a non-conservative nonlinear system are sometimes referred to as damped nonlinear normal modes (dNNMs). Because of the non-conservative... 相似文献
9.
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke... 相似文献
10.