全文获取类型
收费全文 | 576348篇 |
免费 | 7910篇 |
国内免费 | 2441篇 |
专业分类
化学 | 308651篇 |
晶体学 | 6929篇 |
力学 | 25469篇 |
综合类 | 72篇 |
数学 | 70149篇 |
物理学 | 175429篇 |
出版年
2021年 | 4457篇 |
2020年 | 5334篇 |
2019年 | 5777篇 |
2018年 | 7471篇 |
2017年 | 7390篇 |
2016年 | 11204篇 |
2015年 | 7168篇 |
2014年 | 10923篇 |
2013年 | 26449篇 |
2012年 | 20877篇 |
2011年 | 25506篇 |
2010年 | 17953篇 |
2009年 | 17768篇 |
2008年 | 23612篇 |
2007年 | 23580篇 |
2006年 | 21910篇 |
2005年 | 19678篇 |
2004年 | 18044篇 |
2003年 | 15595篇 |
2002年 | 14358篇 |
2001年 | 16961篇 |
2000年 | 12523篇 |
1999年 | 9462篇 |
1998年 | 7869篇 |
1997年 | 7803篇 |
1996年 | 7550篇 |
1995年 | 7078篇 |
1994年 | 7093篇 |
1993年 | 6852篇 |
1992年 | 7592篇 |
1991年 | 7675篇 |
1990年 | 7339篇 |
1989年 | 7087篇 |
1988年 | 7028篇 |
1987年 | 6925篇 |
1986年 | 6605篇 |
1985年 | 8769篇 |
1984年 | 8906篇 |
1983年 | 7228篇 |
1982年 | 7464篇 |
1981年 | 7259篇 |
1980年 | 6702篇 |
1979年 | 7257篇 |
1978年 | 7595篇 |
1977年 | 7538篇 |
1976年 | 7467篇 |
1975年 | 6935篇 |
1974年 | 7011篇 |
1973年 | 6993篇 |
1972年 | 5124篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Gaineev A. M. Galkina I. V. Davletshin R. R. Davletshina N. V. Kuznetsov N. O. Grishaev D. Yu. Shulayeva M. P. Pozdeev O. K. 《Russian Journal of General Chemistry》2022,92(7):1208-1213
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a... 相似文献
102.
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103.
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
104.
Achieving tunable band gaps in a structure by external stimuli is of great importance in acoustic applications. This paper aims to investigate the tunability of band gaps in square-lattice-like elastic periodic structures that are usually not featured with notable band gaps.Endowed with chirality, the periodic structures here are able to undergo imperfection-insensitive large deformation under extension or compression. The influences of geometric parameters on band gaps are discussed via the nonlinear finite element method. It is shown that the band gaps in such structures with curved beams can be very rich and, more importantly, can be efficiently and robustly tuned by applying appropriate mechanical loadings without inducing buckling. As expected, geometry plays a more significant role than material nonlinearity does in the evolution of band gaps. The dynamic tunability of band gaps through mechanical loading is further studied. Results show that closing, opening, and shifting of band gaps can be realized by exerting real-time global extension or compression on the structure. The proposed periodic structure with well-designed chiral symmetry can be useful in the design of particular acoustic devices. 相似文献
105.
106.
E. L. Belokoneva A. S. Karamysheva O. V. Dimitrova A. S. Volkov 《Crystallography Reports》2018,63(5):734-737
Crystals of new indium iodate (K0.6Na0.4Ba)In[IO3]6 were prepared by the hydrothermal synthesis. The unit-cell parameters are a = 11.3984(3) Å, с = 11.3817(3) Å, sp. gr. R3?. The chemical formula of the compound was derived from the structure determination and refinement with anisotropic displacement parameters to R = 0.0284. In the structure the InO6 octahedra share vertices with six umbrella-like [IO3]–groups typical of iodates and form isolated 3?-symmetric charged \(\rm{In[IO_{3}]_6^{3-}}\) clusters. Large Ba, K, and Na cations occupy a common site on a threefold axis due to the isomorphous substitution and compensate the charge of the clusters. The new structure extends the family of the recently discovered alkali-metal and barium iodates containing Ti and Zr atoms in octahedral sites. The iodate K2Ge[IO3]6 containing Ge atoms in the centers of octahedra is the parent compound of this structural family. 相似文献
107.
We will study all finite groups and their subgroups with at most four relative centralizers. 相似文献
108.
In this corrigendum, we correct the statement and proof of Lemma 3.2, revise the proofs of Lemma 3.3 and Theorem 3.5, retract Proposition 3.10 and correct several typographical errors. 相似文献
109.
110.
We describe the static charge susceptibility and correlation function of the charge density in the twodimensional t-J-V model based on the method of equations of motion for the relaxation functions of the Hubbard operators. We obtain the dependence of the susceptibility and correlation function on the hole concentration and temperature. Charge density waves can develop if the intersite Coulomb interaction is sufficiently strong. 相似文献