全文获取类型
收费全文 | 133969篇 |
免费 | 11075篇 |
国内免费 | 9546篇 |
专业分类
化学 | 80515篇 |
晶体学 | 1669篇 |
力学 | 7782篇 |
综合类 | 514篇 |
数学 | 16063篇 |
物理学 | 48047篇 |
出版年
2023年 | 1299篇 |
2022年 | 2365篇 |
2021年 | 3088篇 |
2020年 | 3556篇 |
2019年 | 3727篇 |
2018年 | 3882篇 |
2017年 | 3718篇 |
2016年 | 4918篇 |
2015年 | 3724篇 |
2014年 | 5175篇 |
2013年 | 7104篇 |
2012年 | 7780篇 |
2011年 | 9329篇 |
2010年 | 6678篇 |
2009年 | 6586篇 |
2008年 | 6487篇 |
2007年 | 5960篇 |
2006年 | 5558篇 |
2005年 | 4988篇 |
2004年 | 5132篇 |
2003年 | 4128篇 |
2002年 | 4137篇 |
2001年 | 3589篇 |
2000年 | 2638篇 |
1999年 | 2378篇 |
1998年 | 2250篇 |
1997年 | 1969篇 |
1996年 | 1864篇 |
1995年 | 1610篇 |
1994年 | 1576篇 |
1993年 | 1758篇 |
1992年 | 1758篇 |
1991年 | 1595篇 |
1990年 | 1588篇 |
1989年 | 1459篇 |
1988年 | 1074篇 |
1987年 | 1009篇 |
1986年 | 1009篇 |
1985年 | 1014篇 |
1984年 | 970篇 |
1983年 | 879篇 |
1982年 | 842篇 |
1979年 | 805篇 |
1978年 | 815篇 |
1977年 | 811篇 |
1976年 | 923篇 |
1975年 | 817篇 |
1974年 | 847篇 |
1973年 | 850篇 |
1972年 | 753篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
101.
高能重带电粒子能直接穿透靶原子核外电子层,与原子核发生直接碰撞,发生散裂反应,产生一系列具有放射性的剩余产物核.重带电粒子诱发靶材放射性剩余核与辐射防护和人员安全有着密切联系,当前,大部分剩余核产额主要依靠蒙特卡罗粒子输运程序进行模拟计算,其准确程度亟需通过实验测量进行准确评估.本文利用能量为80.5 MeV/u的(12)^C6+粒子对薄铜靶开展了辐照实验与伽玛射线测量,结合伽玛谱学分析方法,得出了辐照产生的18种放射性剩余产物的初始活度和产生截面值,并与PHITS模拟结果进行对比.结果表明,PHITS模拟程序对放射性剩余核种类的估计具有较高可靠性,在其绝对产额方面,与实验测量仍具有较大偏差. 相似文献
102.
Yablokov M. Yu. Shchegolikhin A. N. Lebedev O. V. Goncharuk G. P. Ozerin A. N. 《Russian Chemical Bulletin》2021,70(9):1816-1821
Russian Chemical Bulletin - Gradient polymer composites were prepared by melt-mixing of carbon black and polypropylene in a compounder and subsequent hot pressing of pellets. The thermally treated... 相似文献
103.
104.
Kinetics and Catalysis - A series of Cu-SSZ-13@CeO2 catalysts with surface modification with CeO2 was prepared by the modified self-resemble method based on the one-pot synthesized Cu-SSZ-13... 相似文献
105.
Gelikonov G. V. Ksenofontov S. Yu. Shilyagin P. A. Gelikonov V. M. 《Radiophysics and Quantum Electronics》2019,62(3):228-236
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in... 相似文献
106.
Physics of Atomic Nuclei - The article presents the concept of a channel-type reactor with a combined cooled moderator. The moderator consists of ceramic beryllium oxide and a liquid... 相似文献
107.
A new asymmetric Salamo‐based ligand H2L was synthesized using 3‐tert‐butyl‐salicylaldehyde and 6‐methoxy‐2‐[O‐(1‐ethyloxyamide)]‐oxime‐1‐phenol. By adjusting the ratio of the ligand H2L and Cu (II), Co (II), and Ni (II) ions, mononuclear, dinuclear, and trinuclear transition metal (II) complexes, [Cu(L)], [{Co(L)}2], and [{Ni(L)(CH3COO)(CH3CH2OH)}2Ni] with the ligand H2L possessing completely different coordination modes were obtained, respectively. The optical spectra of ligand H2L and its Cu (II), Co (II) and Ni (II) complexes were investigated. The Cu (II) complex is a mononuclear structure, and the Cu (II) atom is tetracoordinated to form a planar quadrilateral structure. The Co (II) complex is dinuclear, and the two Co (II) atoms are pentacoordinated and have coordination geometries of distorted triangular bipyramid. The Ni (II) complex is a trinuclear structure, and the terminal and central Ni (II) atoms are all hexacoordinated, forming distorted octahedral geometries. Furthermore, optical properties including UV–Vis, IR, and fluorescence of the Cu (II), Co (II), and Ni (II) complexes were investigated. Finally, the antibacterial activities of the Cu (II), Co (II), and Ni (II) complexes were explored. According to the experimental results, the inhibitory effect was found to be enhanced with increasing concentrations of the Cu (II), Co (II), and Ni (II) complexes. 相似文献
108.
Chunhong Wang Qi Cui Zhixin Zhang Prof. Zhu-Jun Yao Dr. Shaozhong Wang Prof. Zhi-Xiang Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9821-9826
1,3-Azaprotio transfer of propargylic α-ketocarboxylate oximes, a new type of alkynyl oximes featuring an ester tether, has been explored by taking advantage of gold catalysis. The incorporation of an oxygen atom to the chain of alkynyl oximes led to the formation of two different oxa-cyclic nitrones. It was found that internal alkynyl oximes with an E-configuration deliver five-membered nitrones, whereas terminal alkynyl oximes with an E-configuration afford six-membered nitrones. DFT calculations on four possible pathways supported a stepwise formation of C−N and C−H bonds, in which a 1,3-acyloxy-migration competes with the 1,3-azaprotio-transfer, especially in the case of internal alkynyl oximes. The relative nucleophilic properties of oxygen in the carbonyl group and the nitrogen in the oxime, the electronic effects of alkynes, and the influence of the ring system have been investigated computationally. 相似文献
109.
Anfimov N. V. Vorobel V. Kovalev Yu. S. Kodyš P. 《Physics of Particles and Nuclei Letters》2019,16(6):820-825
Physics of Particles and Nuclei Letters - The Silicon Photomultiplier (SiPM) is a novel semiconducting photodetector which can detect single photons. It consists of many microcells (pixels)... 相似文献
110.
Nonlinear Dynamics - Global dynamics of a flexible asymmetrical rotor resting on vibrating supports is investigated. Hamilton’s principle is used to derive the partial differential governing... 相似文献