全文获取类型
收费全文 | 43459篇 |
免费 | 4341篇 |
国内免费 | 2731篇 |
专业分类
化学 | 25045篇 |
晶体学 | 559篇 |
力学 | 2829篇 |
综合类 | 276篇 |
数学 | 4610篇 |
物理学 | 17212篇 |
出版年
2023年 | 627篇 |
2022年 | 692篇 |
2021年 | 940篇 |
2020年 | 1179篇 |
2019年 | 1154篇 |
2018年 | 1061篇 |
2017年 | 936篇 |
2016年 | 1496篇 |
2015年 | 1354篇 |
2014年 | 1788篇 |
2013年 | 2638篇 |
2012年 | 3374篇 |
2011年 | 3744篇 |
2010年 | 2412篇 |
2009年 | 2389篇 |
2008年 | 2594篇 |
2007年 | 2524篇 |
2006年 | 2370篇 |
2005年 | 1933篇 |
2004年 | 1572篇 |
2003年 | 1271篇 |
2002年 | 1161篇 |
2001年 | 1375篇 |
2000年 | 1069篇 |
1999年 | 1063篇 |
1998年 | 852篇 |
1997年 | 845篇 |
1996年 | 829篇 |
1995年 | 687篇 |
1994年 | 651篇 |
1993年 | 538篇 |
1992年 | 531篇 |
1991年 | 463篇 |
1990年 | 384篇 |
1989年 | 313篇 |
1988年 | 251篇 |
1987年 | 219篇 |
1986年 | 194篇 |
1985年 | 193篇 |
1984年 | 144篇 |
1983年 | 97篇 |
1982年 | 68篇 |
1981年 | 64篇 |
1980年 | 33篇 |
1979年 | 32篇 |
1978年 | 36篇 |
1977年 | 41篇 |
1976年 | 47篇 |
1975年 | 55篇 |
1974年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
21.
Journal of Visualization - A large software system contains millions of lines of source code, and the development often involves many developers over a long period. How to understand and... 相似文献
22.
Huang Huaijing Wu Zhaoqi Zhu Chuanxi Fei Shao-Ming 《International Journal of Theoretical Physics》2021,60(7):2368-2379
International Journal of Theoretical Physics - Quantifying the quantumness of ensembles is a vital and practical task in quantum information theory. In this paper, we quantify the quantumness of... 相似文献
23.
Li-Hua Su Tian-Ze Li Yun-Bao Ma Chang-An Geng Xiao-Yan Huang Xin Zhang Zhen Gao Ji-Jun Chen 《中国化学》2022,40(1):104-114
Inspired by the intriguing structures and remarkable activities of sesquiterpenoid dimers,12 new sesquiterpenoid dimers,artematrovirenolides A—D(1—4)and artematrolides S—Z(8—12),were isolated from the EtOAc fraction of Artemisia atrovirens through a bioactivity-guided approach.Their structures were elucidated by comprehensive spectroscopic data and absolute configuration was assigned based on single crystal X-ray diffraction data and ECD calculations.Structurally,all compounds are presumably formed via[4+2]cycloaddition involving three connecting model.Compounds 1—4 are four novel hetero-dimeric[4+2]Diels-Alder adducts dimerized from a rotundane-type unit and a guaiane-type monomer,and compounds 5—12 are eight new homo-dimeric[4+2]adducts derived from two guaianolide moieties.A putative biosynthetic pathway for compounds 1—4 was also proposed.Compounds 4,6,7,and 10 demonstrated moderate cytotoxicity against HepG2,SMMC-7721,and Huh7 cell lines with IC50 values ranging from 9.3 to 62.3μmol/L.Interestingly,compounds 5 and 11 manifested cytotoxicity with IC50 values of 13.6 and 12.8(HepG2),18.5 and 13.1(SMMC-7721),and 16.5 and 19.4μmol/L(Huh7),respectively,which were equivalent to the positive control,sorafenib.This investigation suggests that compounds 5 and 11 might be considered as potent antihepatoma candidates and deserve further structural modification and mechanism study. 相似文献
24.
Nonlinear Dynamics - This paper mainly investigates the dynamics of the non-resonant and near-resonant Hopf–Hopf bifurcations caused by the interaction of the lateral and yaw motion in a... 相似文献
25.
Non-noble bifunctional electrocatalysts with robust activity and stability toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are greatly significant but challenging for Zn-air batteries. Here, in situ confinement of FeNx active sites in high porosity carbon framework (FeNx/CMCC) derived from chelate of carboxymethylcellulose (CMC) and iron ions were synthesized. Particularly, construction of FeNx within porous carbon framework accelerates the electron transfer and the sufficient utilization of active centers, and then expedites the reaction kinetics of ORR and OER. As expected, the optimized FeNx/CMCC exhibits superior ORR activity with a larger half-wave potential of 0.869 V. The rechargeable Zn-air battery delivers a higher power density of 99.6 mW/cm2 and a special capacity of 781.9 mA h/gZn at 10 mA/cm2, together with excellent durability of over 335 h. Remarkably, the as-assembled solid-state battery exhibits a higher open circuit voltage (OCV) of 1.5 V, a special capacity of 709.7 mA h/gZn, as well as prolonged cycling stability (90 h). Moreover, the flexible solid-state battery displays negligible loss of electrochemical performance under various bending angles, illustrating its potential application in flexible electronic devices. 相似文献
26.
本文基于新的Kronecker型替换,给出两个由黑盒表示的稀疏多项式的新确定性插值算法.令f∈R[x1,……,xn]是一个稀疏黑盒多项式,其次数上界为D.当R是C或者是有限域时,相对于已有算法,新算法具有更好的计算复杂度或者关于D的复杂度更低.特别地,对于一般黑盒模型,D是复杂度中的主要因素,而在所有的确定性算法中,本文的第二个算法的复杂度关于D是最低的. 相似文献
27.
Fluid Dynamics - To predict the boundary layer transition on swept wings, experimental and numerical researches were conducted to obtained the accurate boundary layer transition front and to... 相似文献
28.
Journal of Applied Spectroscopy - The speciation of extracted chromium from ZSM-5 into an ionic liquid (IL) was studied using X-ray absorption near-edge structure (XANES) spectroscopy. The main... 相似文献
29.
In this paper,we consider the deformed Hermitian-Yang-Mills equation on closed almost Hermitian manifolds.In the case of the hypercritical phase,we derive a priori estimates under the existence of an admissible C-subsolution.As an application,we prove the existence of solutions for the deformed Hermitian-Yang-Mills equation under the condition of existence of a supersolution. 相似文献
30.