全文获取类型
收费全文 | 22984篇 |
免费 | 834篇 |
国内免费 | 61篇 |
专业分类
化学 | 14804篇 |
晶体学 | 378篇 |
力学 | 720篇 |
综合类 | 1篇 |
数学 | 1789篇 |
物理学 | 6187篇 |
出版年
2023年 | 231篇 |
2022年 | 468篇 |
2021年 | 527篇 |
2020年 | 591篇 |
2019年 | 710篇 |
2018年 | 647篇 |
2017年 | 629篇 |
2016年 | 919篇 |
2015年 | 640篇 |
2014年 | 1058篇 |
2013年 | 1908篇 |
2012年 | 1552篇 |
2011年 | 1689篇 |
2010年 | 1100篇 |
2009年 | 932篇 |
2008年 | 1118篇 |
2007年 | 1088篇 |
2006年 | 867篇 |
2005年 | 748篇 |
2004年 | 598篇 |
2003年 | 465篇 |
2002年 | 417篇 |
2001年 | 252篇 |
2000年 | 240篇 |
1999年 | 186篇 |
1998年 | 125篇 |
1997年 | 154篇 |
1996年 | 184篇 |
1995年 | 173篇 |
1994年 | 163篇 |
1993年 | 184篇 |
1992年 | 222篇 |
1991年 | 157篇 |
1990年 | 146篇 |
1989年 | 161篇 |
1988年 | 139篇 |
1987年 | 138篇 |
1986年 | 118篇 |
1985年 | 166篇 |
1984年 | 184篇 |
1983年 | 137篇 |
1982年 | 143篇 |
1981年 | 135篇 |
1980年 | 142篇 |
1979年 | 148篇 |
1978年 | 152篇 |
1977年 | 138篇 |
1976年 | 96篇 |
1975年 | 92篇 |
1974年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
Xiaona Wen Yu-Chuan Ou Galina Bogatcheva Giju Thomas Anita Mahadevan-Jansen Bhuminder Singh Eugene C. Lin Rizia Bardhan 《Chemical science》2020,11(36):9863
Rapid and accurate response to targeted therapies is critical to differentiate tumors that are resistant to treatment early in the regimen. In this work, we demonstrate a rapid, noninvasive, and label-free approach to evaluate treatment response to molecular inhibitors in breast cancer (BC) cells with Raman spectroscopy (RS). Metabolic reprogramming in BC was probed with RS and multivariate analysis was applied to classify the cells into responsive or nonresponsive groups as a function of drug dosage, drug type, and cell type. Metabolites identified with RS were then validated with mass spectrometry (MS). We treated triple-negative BC cells with Trametinib, an inhibitor of the extracellular-signal-regulated kinase (ERK) pathway. Changes measured with both RS and MS corresponding to membrane phospholipids, amino acids, lipids and fatty acids indicated that these BC cells were responsive to treatment. Comparatively, minimal metabolic changes were observed post-treatment with Alpelisib, an inhibitor of the mammalian target of rapamycin (mTOR) pathway, indicating treatment resistance. These findings were corroborated with cell viability assay and immunoblotting. We also showed estrogen receptor-positive MCF-7 cells were nonresponsive to Trametinib with minimal metabolic and viability changes. Our findings support that oncometabolites identified with RS will ultimately enable rapid drug screening in patients ensuring patients receive the most effective treatment at the earliest time point.Rapid and accurate response to targeted therapies is critical to differentiate tumors that are resistant to treatment early in the regimen. 相似文献
232.
Krishna Raman Surendra S. Parmar Shiva P. Singh 《Journal of heterocyclic chemistry》1980,17(5):1137-1139
A series of 1-(5-phenyl-2H-tetrazol-2-ylacetyl)-4-substituted thiosemicarbazids were prepared as possible antiinflammatory agents. Their antiproteolytic activity was reported. 相似文献
233.
Summary New dioxomolybdenum(VI) complexes MoO2L · H2O (LH2=Schiff base) derived from Salicylhydrazide and salicylaldehyde, 5-chloro-, 5-bromo-, 5-nitro-, 3-methoxy, 3-ethoxy-, 3,5-dichlorosalicylaldehyde and 2-hydroxy-1-naphthaldehyde have been synthesized and characterized, together with the MoO2L · THF adducts. The complexes are monomers, nonelectrolytes and diamagnetic, and contain acis O=Mo=O 相似文献
234.
Chloride1), borohydrides2) and hydrides3) of dicyclopentadienyl thallium (III) and diindenyl thallium (III) have already been reported. The present communication deals with a study on the preparation and characterization of difluorenyl thallium (III) chloride, -hydride and -borohydride. 相似文献
235.
An efficient route for the regio- and stereoselective ring opening of N-tosylaziridines with zinc dihalides (ZnX2, X = Cl, Br, I) is described. Depending on the solvent and Zn(II) halide, β-halo amines or imidazolines are obtained selectively in good to excellent yields. 相似文献
236.
Molecular simulation study of effect of molecular association on vapor-liquid interfacial properties
Vapor-liquid interfacial properties of square-well associating fluids are studied via transition-matrix Monte Carlo simulation. Results for one-site and two-site association models are presented. Coexistence properties, surface tension, cluster distribution, density profile, and orientation profile are presented. Molecular association affects the interfacial properties and cluster fractions more than it affects the bulk densities. We observe that the surface tension exhibits a maximum with respect to association strength. This behavior is in agreement with the recent study of Peery and Evans for one site system using a square-gradient approach. 相似文献
237.
The treatment of 3,4-dihydropyrimidin-2-ones with n-BuLi at −78 °C, followed by quenching with various electrophiles furnished N3-substituted derivatives, regioselectively. Further, N1,N3-diacyl derivatives were found to transfer N1-acyl groups to nucleophilic sites. 相似文献
238.
We examine a model system to study the effect of pressure on the surface tension of a vapor-liquid interface. The system is a two-component mixture of spheres interacting with the square-well (A-A) and hard-sphere (B-B) potentials and with unlike (A-B) interactions ranging (for different cases) from hard sphere to strongly attractive square well. The bulk-phase and interfacial properties are measured by molecular dynamics simulation for coexisting vapor-liquid phases for various mixture compositions, pressures, and temperatures. The variation of the surface tension with pressure compares well to values given by surface-excess formulas derived from thermodynamic considerations. We find that surface tension increases with pressure only for the case of an inert solute (hard-sphere A-B interactions) and that the presence of A-B attractions strongly promotes a decrease of surface tension with pressure. An examination of density and composition profiles is made to explain these effects in terms of surface-adsorption arguments. 相似文献
239.
Akhilesh K. Verma Rupesh Kumar Amit Saxena Subho Mozumdar 《Tetrahedron letters》2005,46(31):5229-5232
A novel method for effecting the aza-Michael reactions of N-alkyl- and N-arylpiperazines with acrylonitrile using Cu-nanoparticles is described. The method features the use of 10 mol % Cu (14-17 nm) nanoparticles under mild reaction conditions to afford the addition products in good to excellent yields. The Cu-nanoparticles selectively catalysed the aza-Michael reaction of N-alkyl- and N-arylpiperazines in the presence of aromatic amino or aliphatic hydroxy groups. 相似文献
240.
N. L. Chutke M. N. Ambulkar V. K. N. Singh A. N. Garg 《Fresenius' Journal of Analytical Chemistry》1994,350(12):723-726
A multielemental instrumental neutron activation analysis (INAA) method has been employed for the determination of 30 elements in seven garden soil samples from Nagpur City and two intercomparison soil standards from IAEA, Vienna and Institute of Radioecology and Applied Nuclear Techniques (IRANT), Slovak Republic. Environmental implications of elemental concentrations in different soils have been discussed. 相似文献