全文获取类型
收费全文 | 29129篇 |
免费 | 4808篇 |
国内免费 | 4240篇 |
专业分类
化学 | 21374篇 |
晶体学 | 438篇 |
力学 | 1691篇 |
综合类 | 364篇 |
数学 | 3555篇 |
物理学 | 10755篇 |
出版年
2024年 | 60篇 |
2023年 | 467篇 |
2022年 | 675篇 |
2021年 | 876篇 |
2020年 | 993篇 |
2019年 | 1127篇 |
2018年 | 930篇 |
2017年 | 936篇 |
2016年 | 1323篇 |
2015年 | 1373篇 |
2014年 | 1758篇 |
2013年 | 2285篇 |
2012年 | 2536篇 |
2011年 | 2827篇 |
2010年 | 2067篇 |
2009年 | 2077篇 |
2008年 | 2188篇 |
2007年 | 2056篇 |
2006年 | 1815篇 |
2005年 | 1579篇 |
2004年 | 1291篇 |
2003年 | 1021篇 |
2002年 | 1122篇 |
2001年 | 853篇 |
2000年 | 742篇 |
1999年 | 537篇 |
1998年 | 404篇 |
1997年 | 311篇 |
1996年 | 310篇 |
1995年 | 234篇 |
1994年 | 231篇 |
1993年 | 180篇 |
1992年 | 170篇 |
1991年 | 140篇 |
1990年 | 121篇 |
1989年 | 117篇 |
1988年 | 80篇 |
1987年 | 61篇 |
1986年 | 57篇 |
1985年 | 58篇 |
1984年 | 36篇 |
1983年 | 23篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 16篇 |
1978年 | 18篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
82.
83.
Xiao Qi ZHENG Yong Hui WANG Qing Xiang GUO* Li YANG You Cheng LIU Department of Chemistry University of Science Technology of China Hefei National Laboratory of Applied Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2003,(8)
As artificial enzymes, the binding constants of cyclodextrins (CDs) and their substrates are expected to be high1. For this purpose, many kinds of bridged cyclodextrin dimers2 whose two cyclodextrins are linked by various spacers have been constructed. It was of interest to make the dimers, whose binding constants would exceed 108dm3/mol3. Up to date, the bridged cyclodextrin dimers have been extensively studied as enzyme models and as molecular receptors4-6. Recently, we synthesized a brid… 相似文献
84.
85.
Two quantities ηrel and are applied to study the nonideal acetone–water association mixture. An all-atom acetone model and a TIP5P water model have been adopted for molecular dynamics simulation. We study the transport properties of the system comparing the 's of strong hydrogen bond and weak contact based on transport properties, MD simulations together with NMR experimental data and find good agreement of concentration dependence, which exhibits the cooperation effect. 相似文献
86.
Kosuke Morita Kouji Morimoto Daiya Kaji Yu Liang Zhao Atsushi Yoshida Toshimi Suda Akira Yoneda Tetsuya Ohnishi Hiromitsu Haba Eiji Ideguchi Hu Shan Xu Tao Zheng Hisaaki Kudo Keisuke Sueki Kenji Katori Isao Tanihata 《Acta Physica Hungarica A》2004,19(1-2):53-60
A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element 271[110] have been performed using the 208Pb(64Ni,1n)271[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope 271[110] of element 110. 相似文献
87.
The effect of α‐cyclodextrin (α‐CD) on the crystallization behavior of poly(3‐hydroxybutyrate) (PHB) was investigated with polarized optical microscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. We found that the addition of α‐CD can greatly accelerate the crystallization of PHB and that α‐CD has a potential not only to enhance the nucleation but also to accelerate the crystallization of PHB. Compared to a conventional nucleation agent, such as talc, α‐CD is a natural product and has many advantages because it is environmentally friendly and safe to humans. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3461–3469, 2004 相似文献
88.
Non-dispersive atomic fluorescence spectrometry (NDAFS) coupled with vapor generation (VG) sample introduction was applied to the determination of the concentrations of hazardous heavy metals, such as arsenic, cadmium, lead and mercury, in seawater, soils and total airborne particulate matter (PM) collected around the Xiamen area in China. Almost 100% sample introduction efficiency was achieved by using thiourea and ascorbic acid for the pre-reduction of As(V) to As(III), K3Fe(CN)6 and tartaric acid for pre-oxidation of Pb(II) to Pb(IV), and masking the interferences arising from the co-existing transition metals to As, Cd, Hg and Pb during their vapor generation process. Moreover, a novel sample pretreatment device was developed to avoid the loss of mercury, lead, cadmium and arsenic during sample pretreatment. With such methods, the detection limit (DL) of arsenic, cadmium, lead and mercury was down to 0.08, 0.03, 0.05, 0.01 ng mL(-1) (3sigma), respectively. The relative standard deviations (RSD, n = 11) for arsenic, cadmium, lead and mercury at 10 ng mL(-1) were 0.9%, 1.6%, 1.3% and 2.0%, respectively. The concentrations of hazardous heavy metals in the environmental samples collected in Xiamen, China are in the range from 0.02 +/- 0.001 ng mL(-1) in seawater to 15.3 +/- 0.2 microg g(-1) in soils. Besides flame/GF-AAS and ICP-AES/MS, VG-NDAFS should be another choice for the determination of hazardous heavy metals in environmental samples. 相似文献
89.
90.
以PCl3为脱水剂,将邻氨基硫酚与水杨酸脱水环化合成出2-(2-羟基苯基)苯并噻唑,并进一步将所得产物与乙酸锌反应合成出2-(2-羟基苯基)苯并噻唑螯合锌(Zn(BTZ)2)材料。以该配合物作为发光层制备出结构为ITO/PVK:TPD/Zn(BTZ)2/Al近白色电致发光器件,其色坐标位于白场之内(x=0.242,y=0.359),在驱动电压为16V时,亮度达3200cdm2,对应的量子效率为0.32%。进一步在Zn(BTZ)2中掺入橙红色染料Rubrene,制成ITO/PVK:TPD/Zn(BTZ)2:Rubrene/Al结构器件,实现了纯白色发光(色坐标值:x=0.324,y=0.343),非常接近于白色等能点,且量子效率达0.47%。最后对上述器件的发光和电学性能进行了深入的研究和探讨。 相似文献