全文获取类型
收费全文 | 30137篇 |
免费 | 4243篇 |
国内免费 | 2722篇 |
专业分类
化学 | 20651篇 |
晶体学 | 286篇 |
力学 | 1953篇 |
综合类 | 277篇 |
数学 | 3295篇 |
物理学 | 10640篇 |
出版年
2024年 | 108篇 |
2023年 | 605篇 |
2022年 | 930篇 |
2021年 | 970篇 |
2020年 | 1134篇 |
2019年 | 1092篇 |
2018年 | 919篇 |
2017年 | 824篇 |
2016年 | 1289篇 |
2015年 | 1285篇 |
2014年 | 1545篇 |
2013年 | 2053篇 |
2012年 | 2640篇 |
2011年 | 2675篇 |
2010年 | 1652篇 |
2009年 | 1640篇 |
2008年 | 1743篇 |
2007年 | 1664篇 |
2006年 | 1502篇 |
2005年 | 1235篇 |
2004年 | 945篇 |
2003年 | 790篇 |
2002年 | 759篇 |
2001年 | 564篇 |
2000年 | 560篇 |
1999年 | 655篇 |
1998年 | 578篇 |
1997年 | 578篇 |
1996年 | 659篇 |
1995年 | 508篇 |
1994年 | 464篇 |
1993年 | 388篇 |
1992年 | 372篇 |
1991年 | 323篇 |
1990年 | 256篇 |
1989年 | 202篇 |
1988年 | 158篇 |
1987年 | 136篇 |
1986年 | 127篇 |
1985年 | 118篇 |
1984年 | 88篇 |
1983年 | 61篇 |
1982年 | 41篇 |
1981年 | 36篇 |
1980年 | 18篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1975年 | 28篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Particular solutions to the Einstein equations with cosmological constant are presented and discussed for an isotropic, spatially homogeneous, and spatially flat space-time in the case that the matter fields are
4,
6, and sine-Gordon fields. 相似文献
994.
995.
996.
Sandy AR Mochrie SG Zehner DM Grübel G Huang KG Gibbs D 《Physical review letters》1992,68(14):2192-2195
997.
998.
Xingang Kong Jiarui Zhang Jianfeng Huang Jiayin Li Yi Qin Ting Zhao Qi Feng 《中国化学快报》2019,30(3):771-774
SnNb2O6 and Sn2Nb2O7 nanosheets were synthetized via microwave assisted hydrothermal method, and innovatively employed as anode materials for lithium-ion battery. Compared with Sn2Nb2O7 and the previously reported pure Sn-based anode materials, the SnNb2O6 electrode exhibited outstanding cycling performance. 相似文献
999.
Chao Chen Yu-Lin Yang Kun-Lin Huang Zhen-Hua Sun Wei Wang Zhuo Yi Yun-Ling Liu Wen-Qin Pang 《Polyhedron》2004,23(18):3033-3042
With a hydrothermal technique, a layered titanium phosphate with the formula Ti2(H2PO4)(HPO4)(PO4)2 · 0.5C6N2H16 (denoted TP-J2) has been prepared by treating the Ti/H3PO4/H2O/1-methylpiperazine system directly. The as-synthesized products were characterized by powder X-ray diffraction, CP-MAS solid-state 31P NMR spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA). The structure was solved by single-crystal X-ray diffraction analysis and it presents an extended γ-phase intercalated with organic amine. Crystal data: triclinic, , a = 8.106 (2) Å, b = 8.197 (2) Å, c = 11.658 (2) Å. = 78.32 (3)°, β = 80.85 (3)°, γ = 77.90 (3)°, Z = 2. Additionally, the intercalation behavior of TP-J2 with n-alkyl monoamine (n = 2, 3, 4, 6, 8, 10 and 12) was investigated. Owing to the strong brønsted base, N,N′-dimethylpiperazine, resides in the interlayer, it presented unusual features of TP-J2 in contrast with that of γ-Tip. 相似文献
1000.
The grafting of ethylene glycol dimethacrylate (EGDMA) onto silk in aqueous alcohol systems using potassiumpersulfate (KPS) in the presence of air was investigated. Effects of grafting conditions, such as concentrations of monomer,initiator and formic acid, temperature and time, on the graft yield were determined. The optimum graft conditions were foundto be: T = 80℃, t = 30 min, [KPS] = 1.85% [on the weight ofmonomer (owm)]; [formic acid] = 0.2% (V/V); [EGDMA] =80% [on the weight of fiber (owf)]. The activation energy of grafting at 50-80℃ was found to be 71.31 kJ/mol for EGDMA.Grafting equations were also evaluated. The graft yield value can be regulated by the concentration of monomer. The graftcopolymerization of EGDMA onto silk is effective in improving the crease-proofing of silk fabrics. 相似文献