全文获取类型
收费全文 | 11257篇 |
免费 | 601篇 |
国内免费 | 2783篇 |
专业分类
化学 | 13450篇 |
晶体学 | 103篇 |
力学 | 46篇 |
综合类 | 120篇 |
数学 | 95篇 |
物理学 | 827篇 |
出版年
2024年 | 25篇 |
2023年 | 215篇 |
2022年 | 1075篇 |
2021年 | 837篇 |
2020年 | 729篇 |
2019年 | 574篇 |
2018年 | 525篇 |
2017年 | 511篇 |
2016年 | 652篇 |
2015年 | 567篇 |
2014年 | 538篇 |
2013年 | 1023篇 |
2012年 | 823篇 |
2011年 | 637篇 |
2010年 | 432篇 |
2009年 | 594篇 |
2008年 | 572篇 |
2007年 | 559篇 |
2006年 | 471篇 |
2005年 | 411篇 |
2004年 | 362篇 |
2003年 | 310篇 |
2002年 | 485篇 |
2001年 | 197篇 |
2000年 | 209篇 |
1999年 | 191篇 |
1998年 | 165篇 |
1997年 | 131篇 |
1996年 | 120篇 |
1995年 | 115篇 |
1994年 | 99篇 |
1993年 | 77篇 |
1992年 | 64篇 |
1991年 | 62篇 |
1990年 | 37篇 |
1989年 | 62篇 |
1988年 | 40篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Z. H. Ismail M. M. Ghorab E. M. A. Mohamed H. M. Aly M. S. A. El-Gaby 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2541-2554
Some novel thiourea,1,2,4-triazole, quinazoline, thieno[2,3-d]pyrimi-dine, and thiazolidine derivatives were synthesized to evaluate their antitumor activity. Compound (3f) is nearly as active as reference drug, (Doxorubicin) as positive control. 相似文献
72.
合成了一系列以两个亚甲基为联接基的杂双子咪唑表面活性剂([Cm-2-Cnim]Br2, m, n=8, 10, 12, 14, 16; m≠n). 用氢谱和质谱对其结构进行了表征. 探索了物料比、反应温度和时间对反应产率的影响. 对合成的杂双子咪唑表面活性剂的表面活性进行了研究,讨论了分子结构的不对称程度对表面活性的影响. 相似文献
73.
《Physics and Chemistry of Liquids》2012,50(4):345-349
Abstract Isobaric vapour-liquid equilibrium data are measured at 200, 500 and 707 mm Hg at ten compositions spread evenly over the entire liquid mole fraction range, employing a Swietoslawski type ebulliometer. The liquid phase composition vs. bubble temperature (x-t) data are found to be well represented by Wilson model The optimum Wilson parameters are used to calculate the vapour phase compositions, activity coefficients and the excess Gibbs free energies. 相似文献
74.
《合成通讯》2012,42(1):85-96
AbstractTwelve bis-thiadiazole derivatives were synthesized in high yield via the reaction of 2,2′-terephthaloyl bis(N-phenylhydrazine carbothioamide) with a variety of hydrazonoyl chlorides in ethanol containing catalytic amounts of TEA. All the newly synthesized compounds were characterized by physical and chemical tools (FT-IR, 1H NMR, 13C NMR, and Mass spectrometry). Moreover, all the novel synthesized derivatives were screened for their antihypertensive α-blocking efficacy against to assess their pharmaceutical significance. The encouraging promising results obtained from antihypertensive α-blocking activity studies on the newly synthesized derivatives make the synthesis of a new series of these compounds and studying of their pharmaceutical importance an active area for more and more investigations. The molecular docking of the most active derivative 15?b against the human dopamine D3 receptor was performed by the Molecular Operating Environment (MOE 2014. 0901) program. 相似文献
75.
76.
《Journal of Coordination Chemistry》2012,65(16-18):2622-2631
AbstractA new 2D Co(II) based coordination polymer (CP), {[Co2(tib)2(NO3)3(H2O)2·NO3]n (1), has been synthesized using 1,3,5-tris(1-imidazolyl)benzene (tib) ligand. The single crystal X-ray diffraction study indicates that 1 possesses an infinite 2D layer, which is further extended into a 3D supramolecular network via O–H···O hydrogen bonding interactions. Additionally, the thermogravimetric analysis (TGA) of CP indicates its decomposition temperature was about 268?°C. The UV/Vis diffuse-reflection spectrum of 1 indicates its semiconducting nature on the basis of which the photocatalytic properties of 1 against photodecomposition of organic dyes have been studied. The possible mechanism associated with the photocatalytic activity of 1 against organic dyes is addressed using density of states (DOS) calculations. 相似文献
77.
《Journal of Coordination Chemistry》2012,65(19):3492-3501
Four MnIII-porphyrin complexes, chloro(tetraphenylporphinato)MnIII(1,6-diaminohexane), bromo(tetraphenylporphinato)MnIII(1,6-diaminohexane), azido(tetraphenylporphinato)MnIII(1,6-diaminohexane), and thiocyanato(tetraphenylporphinato)MnIII(1,6-diaminohexane), have been synthesized. These complexes have been characterized using UV-Vis, IR, ESI-mass spectra, elemental analyses, magnetic susceptibility measurements, and conductivity measurement. The molar conductance values of these complexes in ethanol indicate non-electrolytes. The utility of these complexes in de-polymerization of coal using humic acid as the coal model has been tested by the optical density method. 相似文献
78.
Aishakhanam H. Pathan Ganesh N. Naik Raghavendra P. Bakale Shrinath S. Machakanur Kalagouda B. Gudasi 《应用有机金属化学》2012,26(3):148-155
A series of Co(II), Ni(II), Cu(II), and Zn(II) complexes of a tridentate hydrazone were prepared and characterized by various spectro‐analytical techniques and magnetic moment studies. The complexes were found to be monomeric and non‐electrolytes. The copper complex is electrochemically active in the applied potential range. The compounds synthesized in the present study have shown promising antiproliferative activity when screened using the in vitro method against two human cancer cell lines: HeLa and HepG2. The Escherichia coli DNA‐binding properties of all the compounds were investigated with UV–visible absorption spectrophotometric titrations, viscosity measurements, DNA melting experiments and gel electrophoreses measurements. The compounds were demonstrated to act as DNA intercalators with appreciable DNA‐binding constant values. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
79.
Recently, thioredoxin reductase as a target for treatment of tumors has attracted the attention of scientists. 1,2‐[Bis(1,2‐benzisoselenazolone‐3(2 H)‐ketone)]ethane (ethaselen, BBSKE, PCT: CN02/00412), designed and synthesized previously, is an effective thioredoxin reductase inhibitor; presently it is in phase II clinical trials, targeting gastric cancer, lung cancer and colon cancer. To seek more novel and effective anticancer drugs, we have developed many selenazole‐based compounds. Evaluation of the thioredoxin reductase inhibitory effect and investigation of the mechanism of anticancer drugs require abundant thioredoxin reductase, but since commercial thioredoxin reductase is expensive its use is often limited. Therefore, the preparation of thioredoxin reductase is necessary. Base on the above investigation, in this work we have prepared thioredoxin reductase and evaluated selenazole‐based compounds, and found that 44 compounds have high inhibitory effect on thioredoxin reductase with IC50 < 10 µ m , of which 16 compounds have IC50 values below 1 µ m . This is helpful in investigating and elucidating the mechanism of this kind of compound. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
80.