全文获取类型
收费全文 | 208814篇 |
免费 | 3610篇 |
国内免费 | 1486篇 |
专业分类
化学 | 105571篇 |
晶体学 | 2711篇 |
力学 | 9921篇 |
综合类 | 70篇 |
数学 | 23499篇 |
物理学 | 72138篇 |
出版年
2021年 | 1860篇 |
2020年 | 2128篇 |
2019年 | 2310篇 |
2018年 | 2980篇 |
2017年 | 2875篇 |
2016年 | 4174篇 |
2015年 | 2706篇 |
2014年 | 4057篇 |
2013年 | 9706篇 |
2012年 | 7954篇 |
2011年 | 9534篇 |
2010年 | 6581篇 |
2009年 | 6427篇 |
2008年 | 8512篇 |
2007年 | 8544篇 |
2006年 | 8223篇 |
2005年 | 7253篇 |
2004年 | 6725篇 |
2003年 | 5894篇 |
2002年 | 5423篇 |
2001年 | 6395篇 |
2000年 | 4816篇 |
1999年 | 3697篇 |
1998年 | 2935篇 |
1997年 | 3000篇 |
1996年 | 2720篇 |
1995年 | 2684篇 |
1994年 | 2515篇 |
1993年 | 2372篇 |
1992年 | 2709篇 |
1991年 | 2657篇 |
1990年 | 2594篇 |
1989年 | 2384篇 |
1988年 | 2431篇 |
1987年 | 2417篇 |
1986年 | 2254篇 |
1985年 | 2934篇 |
1984年 | 3196篇 |
1983年 | 2603篇 |
1982年 | 2772篇 |
1981年 | 2718篇 |
1980年 | 2599篇 |
1979年 | 2697篇 |
1978年 | 2787篇 |
1977年 | 2803篇 |
1976年 | 2864篇 |
1975年 | 2650篇 |
1974年 | 2625篇 |
1973年 | 2755篇 |
1972年 | 1743篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Tuskaev V. A. Bogdanov V. S. Gagieva S. Ch. Kurmaev D. A. Shatokhin S. S. Evseeva M. D. Golubev E. K. Buzin M. I. Nikiforova G. G. Bulychev B. M. 《Russian Chemical Bulletin》2022,71(1):76-82
The catalytic activity of the systems based on titanium(iv) alkoxides (Ti(OPri)4, Ti(OPri)2(OCH(CF3)2)2, and Ti(OCH(CF3)2)4) and mixtures of alkylaluminum chlorides (Et2AlCl or Et3Al2Cl3) with dibutylmagnesium in ethylene polymerization and ethylene copolymerization with propylene and 5-ethylidene-2-norbornene was studied. Ultrahigh-molecular-weight polyethylene with the molecular weight reaching 4.9 · 106 Da was found to be formed in the homopolymerization reaction, whereas copolymerization gives ter-copolymers containing propylene (up to 35 mol.%) and 5-ethylidene-2-norbornene (4.3 mol.%) units.
相似文献52.
Pasyukov D. V. Chernenko A. Yu. Lavrentev I. V. Baydikova V. A. Minyaev M. E. Starovoytova O. A. Chernyshev V. M. 《Russian Chemical Bulletin》2022,71(5):993-1008
Russian Chemical Bulletin - The reaction of 1,4-disubstituted thiosemicarbazides with N,N-dimethylformamide dimethyl acetal afforded 1,4-disubstituted 1,2,4-triazolium-3-thiolates. Heating of the... 相似文献
53.
54.
Two new divalent copper (C1) and zinc (C2) chelates having the formulae [M(PIMC)2] (where M = Cu(II), Zn(II) and PIMC = Ligand [(E)-3-(((3-hydroxypyridin-2-yl)imino)methyl)-4H-chromen-4-one] were obtained and characterized by several techniques. Structures and geometries of the synthesized complexes were judged based on the results of alternative analytical and spectral tools supporting the proposed formulae. IR spectral data confirmed the coordination of the ligands to the copper and zinc centers as monobasic tridentate in the enol form. Thermal analysis, UV-Vis spectra and magnetic moment confirmed the geometry around the copper center to be tetrahedral, square pyramidal and octahedral. Study of the binding ability of the synthesized compounds with Circulating tumor DNA (CT-DNA) bas been evaluated applying UV-Vis spectral titration and viscosity measurements. The copper and zinc oxides were achieved from the copper and zinc nano-particles structures Schiff base complexes as the raw material after calcination for 5 hr at 600°C. On the other hand, synthesized of C1 and C2 NPs were used as suitable precursors to the preparation of CuO and ZnO NPs. Finally, the synthesized of the two complexes exhibited enhanced activity against the tested bacterial (Staphylococcus aureus and Escherichia Coli) and fungal strains (Candida albicans and Aspergillus fumigatus) as compared to HPIMC. Among all these synthesized compounds, C1 exhibits good cleaving ability compared to other newly synthesized C2. 相似文献
55.
56.
57.
The problem of describing the behavior of a highly filled polymeric material under compression, which was preceded by preliminary compression and unloading, is considered. The peculiarity of the compression diagrams obtained in the experiment is the downward convexity of the curves of the stress modulus versus time. To solve this problem, a variant of the non-linear endochronic theory of aging viscoelastic materials with several aging and viscosity functions and a numerical-graphical method for identifying the properties of viscoelasticmaterials proposed by the authors earlier, suggesting comparison of the deformation diagrams of intact samples and those that received preliminary damage, are used. 相似文献
58.
Mathematical Programming - The results on regularity behavior of solutions to variational inequalities over polyhedral sets proved in a series of papers by Robinson, Ralph and Dontchev-Rockafellar... 相似文献
59.
K. E. Prikhodko M. M. Dementyeva B. A. Gurovich D. A. Komarov L. V. Kutuzov 《Crystallography Reports》2018,63(2):241-244
The change in the free-electron density in ultrathin (5 nm) superconducting NbN films in the initial state and after irradiation by O+ ions to doses of (0.1–0.9) × 1017 cm–2 has been studied by electron energy-loss spectroscopy (EELS). The analysis has been performed on cross section samples prepared by the focused ion beam method, using plasmon oscillations with energies up to 50 eV. The radiation-induced replacement of nitrogen atoms with oxygen atoms in niobium nitride is found to change the electrical properties of the material, which leads to a decrease in the free-electron density with an increase in the irradiation dose. 相似文献
60.
G. Kalkabay A. L. Kozlovskiy M. A. Ibragimova D. I. Shlimas M. V. Zdorovets D. B. Borgekov A. V. Tikhonov 《Crystallography Reports》2018,63(1):90-95
Nickel nanotubes have been synthesized by electrochemical deposition, and their reactivity in aggressive media has been investigated. Kinetic curves of the variation in the atomic ratio between Ni and O in the nanotube crystal structure as a function of the medium acidity are built. 相似文献