全文获取类型
收费全文 | 24889篇 |
免费 | 963篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 347篇 |
综合类 | 38篇 |
化学工业 | 5681篇 |
金属工艺 | 381篇 |
机械仪表 | 477篇 |
建筑科学 | 1308篇 |
矿业工程 | 100篇 |
能源动力 | 627篇 |
轻工业 | 1896篇 |
水利工程 | 233篇 |
石油天然气 | 71篇 |
无线电 | 1828篇 |
一般工业技术 | 4535篇 |
冶金工业 | 4613篇 |
原子能技术 | 202篇 |
自动化技术 | 3548篇 |
出版年
2023年 | 217篇 |
2022年 | 360篇 |
2021年 | 570篇 |
2020年 | 338篇 |
2019年 | 431篇 |
2018年 | 536篇 |
2017年 | 464篇 |
2016年 | 635篇 |
2015年 | 560篇 |
2014年 | 754篇 |
2013年 | 1422篇 |
2012年 | 1167篇 |
2011年 | 1514篇 |
2010年 | 1078篇 |
2009年 | 1016篇 |
2008年 | 1152篇 |
2007年 | 1086篇 |
2006年 | 944篇 |
2005年 | 763篇 |
2004年 | 753篇 |
2003年 | 661篇 |
2002年 | 568篇 |
2001年 | 431篇 |
2000年 | 368篇 |
1999年 | 410篇 |
1998年 | 778篇 |
1997年 | 567篇 |
1996年 | 451篇 |
1995年 | 416篇 |
1994年 | 384篇 |
1993年 | 368篇 |
1992年 | 274篇 |
1991年 | 198篇 |
1990年 | 274篇 |
1989年 | 260篇 |
1988年 | 218篇 |
1987年 | 228篇 |
1986年 | 229篇 |
1985年 | 267篇 |
1984年 | 225篇 |
1983年 | 225篇 |
1982年 | 210篇 |
1981年 | 196篇 |
1980年 | 172篇 |
1979年 | 195篇 |
1978年 | 166篇 |
1977年 | 189篇 |
1976年 | 236篇 |
1975年 | 161篇 |
1974年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
Freddy A. Bernal Dr. Marcel Kaiser Prof. Dr. Bernhard Wünsch Prof. Dr. Thomas J. Schmidt 《ChemMedChem》2020,15(1):68-78
Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model. 相似文献
23.
24.
25.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows. 相似文献
26.
Interactions of hexamethylenetetramine ligand in atom transfer radical polymerization initiated by activator generated by electron transfer were studied. Polymerization of methyl methacrylate was done using two-step experimental procedure in 2 L emulsion batch reactor at 50, 60, and 80°C. The selection of reactant ratios was quite challenging for a reactor of this size. Replicate runs were conducted for data reproducibility purpose. Gravimetry method and gel permeation chromatography were used to determine monomer conversion, Mn, and PDI of polymer samples. PMMA produced was also characterized by means of dynamic light scattering, Fourier-transform infrared spectroscopy and nuclear Magnetic Resonance spectroscopy. Results showed high monomer conversion up to 93% and Mn ranging 243–274 kg/mol with PDI from 1.45 to 1.60. Besides, combining HMTA with sodium dodecyl sulfate, an anionic surfactant, a well-controlled polymer with a lower Mn of 201 kg/mol and PDI of 1.56 was obtained in 3 hr reaction time. 相似文献
27.
We demonstrate that alkali-halide salts, particularly potassium bromide, can reduce the photothermal emission (PTE) from single walled carbon nanotubes (SWNT). PTE is a prominent spectral feature in Raman spectroscopy when a near infrared laser is used to analyze a dark colored sample. We subsequently show that trapping salts inside SWNT and coating SWNT with the salt has a more pronounced impact on not only reducing PTE, but also enhancing the intensity of the Raman spectral features. The effect, which we have called nanotube enhanced Raman spectroscopy (NERS), has differences and similarities to the widely studied surface enhanced Raman spectroscopy (SERS). 相似文献
28.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology. 相似文献
29.
Using an integrated process of data and modeling in HRA 总被引:1,自引:0,他引:1
John Wreathall Dennis Bley Emilie Roth Jordan Multer Thomas Raslear 《Reliability Engineering & System Safety》2004,83(2):221
The paper describes an approach taken to estimate the probabilities of failure associated with various railroad tasks to prevent accidents (principally collisions and derailments). These probabilities were estimated using an expert elicitation process that used partially relevant data available from a variety of databases and that were filtered and scaled to make them more directly relevant to the analyses being performed. Extensive qualitative studies were performed prior to the elicitation process to identify relevant contexts under which the tasks can be performed. 相似文献
30.
T. Choi J.‐H. Jang C.K. Ullal M.C. LeMieux V.V. Tsukruk E.L. Thomas 《Advanced functional materials》2006,16(10)
The probing of the micromechanical properties within a two‐dimensional polymer structure with sixfold symmetry fabricated via interference lithography reveals a nonuniform spatial distribution in the elastic modulus “imprinted” with an interference pattern in work reported by Tsukruk, Thomas, and co‐workers on p. 1324. The image prepared by M. Lemieux and T. Gorishnyy shows how the interference pattern is formed by three laser beams and is transferred to the solid polymer structure. The elastic and plastic properties within a two‐dimensional polymer (SU8) structure with sixfold symmetry fabricated via interference lithography are presented. There is a nonuniform spatial distribution in the elastic modulus, with a higher elastic modulus obtained for nodes (brightest regions in the laser interference pattern) and a lower elastic modulus for beams (darkest regions in the laser interference pattern) of the photopatterned films. We suggest that such a nonuniformity and unusual plastic behavior are related to the variable material properties “imprinted” by the interference pattern. 相似文献