全文获取类型
收费全文 | 184416篇 |
免费 | 3878篇 |
国内免费 | 196篇 |
专业分类
电工技术 | 3900篇 |
综合类 | 522篇 |
化学工业 | 34849篇 |
金属工艺 | 9696篇 |
机械仪表 | 6081篇 |
建筑科学 | 3644篇 |
矿业工程 | 2054篇 |
能源动力 | 2816篇 |
轻工业 | 10501篇 |
水利工程 | 2847篇 |
石油天然气 | 8760篇 |
武器工业 | 12篇 |
无线电 | 14809篇 |
一般工业技术 | 41030篇 |
冶金工业 | 27946篇 |
原子能技术 | 6956篇 |
自动化技术 | 12067篇 |
出版年
2021年 | 2211篇 |
2019年 | 2139篇 |
2018年 | 3520篇 |
2017年 | 3469篇 |
2016年 | 3937篇 |
2015年 | 2443篇 |
2014年 | 3755篇 |
2013年 | 7713篇 |
2012年 | 4840篇 |
2011年 | 5792篇 |
2010年 | 5168篇 |
2009年 | 5789篇 |
2008年 | 5346篇 |
2007年 | 5240篇 |
2006年 | 4412篇 |
2005年 | 4081篇 |
2004年 | 3853篇 |
2003年 | 3724篇 |
2002年 | 3560篇 |
2001年 | 3573篇 |
2000年 | 3424篇 |
1999年 | 3300篇 |
1998年 | 7187篇 |
1997年 | 5274篇 |
1996年 | 4010篇 |
1995年 | 3096篇 |
1994年 | 2748篇 |
1993年 | 2935篇 |
1992年 | 2402篇 |
1991年 | 2422篇 |
1990年 | 2552篇 |
1989年 | 2484篇 |
1988年 | 2449篇 |
1987年 | 2348篇 |
1986年 | 2423篇 |
1985年 | 2448篇 |
1984年 | 2370篇 |
1983年 | 2306篇 |
1982年 | 2134篇 |
1981年 | 2389篇 |
1980年 | 2217篇 |
1979年 | 2430篇 |
1978年 | 2547篇 |
1977年 | 2575篇 |
1976年 | 3243篇 |
1975年 | 2445篇 |
1974年 | 2490篇 |
1973年 | 2702篇 |
1972年 | 2363篇 |
1971年 | 2060篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
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
162.
163.
Prof. Dr. Hans-René Bjørsvik Prof. Dr. Bjørn Tore Gjertsen Dr. Vijayaragavan Elumalai 《ChemMedChem》2020,15(10):862-870
A previously designed and developed 12-step total synthesis that includes [1,1′-biphenyl]-2-amine and carbazole intermediates and that ultimately produces the carbazole alkaloid carbazomycin G was exploited as a screening compound library with the goal of identifying potential lead compound(s) with cytotoxic effect. These compounds were investigated by using in-vitro tests involving the two human cell lines HL-60 and MOLM-13, which both model acute myeloid leukaemia (AML). The in-vitro biological test results were used together with the molecular structures of the various intermediates in a concise SAR analysis. Several of the intermediates revealed cytotoxicity (IC50<10−4 M), although the final natural product carbazomycin G did not reveal cytotoxicity versus the two said human cell lines. 相似文献
164.
Semiconductors - The optical properties of dielectric nanostructures strongly depend on dielectric nanoparticles (NP) polarizability which can take the high values even interacting with... 相似文献
165.
Maja D. Markovic Vesna V. Panic Sanja I. Seslija Ana D. Milivojevic Pavle M. Spasojevic Nevenka M. Boskovic-Vragolovic Rada V. Pjanovic 《Polymer Engineering and Science》2020,60(8):2008-2022
Carriers for targeted delivery and controlled release of poorly water-soluble active substances (PWSAS) are facing three challenges: (a) the encapsulation issues, (b) limitations of PWSAS water solubility, and (c) burst drug release which can be pharmacologically dangerous and economically inefficient. The present study brings a novel strategy for encapsulation and controlled release of PWSAS—caffeine in concentrations which are higher than its maximal water solubility without the possibility of burst effect. The modification of hydrophilic carrier based on poly(methacylic acid) was done using casein and liposomes. To further increase the maximal caffeine loading inside the carrier nicotinamide was used. The release study of the encapsulated PWSAS was elaborated with respect to morphology of the carriers and interactions that could be established between its structural components. The carriers swelling and the release of caffeine and nicotinamide were also investigated depending on caffeine concentration, the presence of different liposomal formulations and the volume ratio of liposomal formulation, in three media with different pH simulating the path of the carrier through the human gastrointestinal tract. The synthesized carriers are promising candidates for encapsulation of PWSAS in concentrations which are higher than its maximal water solubility and for the targeted delivery of those dosages. 相似文献
166.
A. E. Kudryashov Zh. V. Eremeeva E. A. Levashov V. Yu. Lopatin A. V. Sevost’yanova E. I. Zamulaeva 《Surface Engineering and Applied Electrochemistry》2018,54(5):437-445
Electrospark treatment of OT4-1 titanium alloy was performed sequentially with a STIM-20N hard-alloy electrode (TiC–20% Ni) and carbon-containing material (graphite and carbon-based composite materials). Kinetics of the mass transfer of the hard-alloy electrode was studied. The cathode mass loss during the first minute of the treatment was established. The kinetics results were processed using the methods of mathematical statistics. The erosion resistance of the applied carbon-containing materials was determined. Phase composition and relief of the coatings formed were analyzed. It was found that the application of the carbon-containing material increases the content of refractory phases in the coatings. Increase in the time of the treatment using the carbon-containing materials decreases the roughness of the coatings. 相似文献
167.
Alice Maurer Prof. Dr. Florian P. Seebeck 《Chembiochem : a European journal of chemical biology》2020,21(20):2908-2911
Ergothioneine has emerged as a crucial cytoprotectant in the pathogenic lifestyle of Mycobacterium tuberculosis. Production of this antioxidant from primary metabolites may be regulated by phosphorylation of Thr213 in the active site of the methyltransferase EgtD. The structure of mycobacterial EgtD suggests that this post-translational modification would require a large-scale change in conformation to make the active-site residue accessible to a protein kinase. In this report, we show that, under in vitro conditions, EgtD is not a substrate of protein kinase PknD. 相似文献
168.
169.
170.
Dr. Hui Qiu Richard Caldwell Dr. Lesley Liu-Bujalski Dr. Andreas Goutopoulos Reinaldo Jones Justin Potnick Dr. Brian Sherer Dr. Andrew Bender Dr. Roland Grenningloh Dr. Daigen Xu Dr. Anna Gardberg Dr. Igor Mochalkin Dr. Theresa Johnson Dr. Ariele Viacava Follis Jared Head Dr. Federica Morandi 《ChemMedChem》2019,14(2):217-223
Bruton's tyrosine kinase (Btk) is an attractive target for the treatment of a wide array of B-cell malignancies and autoimmune diseases. Small-molecule covalent irreversible Btk inhibitors targeting Cys481 have been developed for the treatment of such diseases. In clinical trials, probe molecules are required in occupancy studies to measure the level of engagement of the protein by these covalent irreversible inhibitors. The result of this pharmacodynamic (PD) activity provides guidance for appropriate dosage selection to optimize inhibition of the drug target and correlation of target inhibition with disease treatment efficacy. This information is crucial for successful evaluation of drug candidates in clinical trials. Based on the pyridine carboxamide scaffold of a novel solvent-accessible pocket (SAP) series of covalent irreversible Btk inhibitors, we successfully developed a potent and selective affinity-based biotinylated probe 12 (2-[(4-{4-[5-(1-{5-[(3aS,4S,6aR)-2-oxo-hexahydro-1H-thieno[3,4-d]imidazol-4-yl]pentanamido}-3,6,9,12-tetraoxapentadecan-15-amido)pentanoyl]piperazine-1-carbonyl}phenyl)amino]-6-[1-(prop-2-enoyl)piperidin-4-yl]pyridine-3-carboxamide). Compound 12 has been used in Btk occupancy assays for preclinical studies to determine the therapeutic efficacy of Btk inhibition in two mouse lupus models driven by TLR7 activation and type I interferon. 相似文献