全文获取类型
收费全文 | 12049篇 |
免费 | 1058篇 |
国内免费 | 106篇 |
专业分类
电工技术 | 15篇 |
综合类 | 293篇 |
化学工业 | 4976篇 |
金属工艺 | 72篇 |
机械仪表 | 113篇 |
建筑科学 | 210篇 |
矿业工程 | 32篇 |
能源动力 | 154篇 |
轻工业 | 6606篇 |
水利工程 | 35篇 |
石油天然气 | 177篇 |
武器工业 | 1篇 |
无线电 | 50篇 |
一般工业技术 | 307篇 |
冶金工业 | 64篇 |
原子能技术 | 30篇 |
自动化技术 | 78篇 |
出版年
2024年 | 84篇 |
2023年 | 228篇 |
2022年 | 451篇 |
2021年 | 550篇 |
2020年 | 460篇 |
2019年 | 449篇 |
2018年 | 422篇 |
2017年 | 479篇 |
2016年 | 529篇 |
2015年 | 521篇 |
2014年 | 600篇 |
2013年 | 781篇 |
2012年 | 776篇 |
2011年 | 738篇 |
2010年 | 535篇 |
2009年 | 533篇 |
2008年 | 522篇 |
2007年 | 622篇 |
2006年 | 507篇 |
2005年 | 402篇 |
2004年 | 360篇 |
2003年 | 318篇 |
2002年 | 289篇 |
2001年 | 219篇 |
2000年 | 276篇 |
1999年 | 192篇 |
1998年 | 207篇 |
1997年 | 122篇 |
1996年 | 152篇 |
1995年 | 131篇 |
1994年 | 108篇 |
1993年 | 106篇 |
1992年 | 120篇 |
1991年 | 100篇 |
1990年 | 60篇 |
1989年 | 43篇 |
1988年 | 30篇 |
1987年 | 37篇 |
1986年 | 35篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
101.
Marco Sarcletti Dustin Vivod Tobias Luchs Tobias Rejek Luis Portilla Lukas Müller Hanno Dietrich Andreas Hirsch Dirk Zahn Marcus Halik 《Advanced functional materials》2019,29(15)
Various hydrocarbons are efficiently extracted from water by using a new sorbent material based on covalently functionalized magnetic nanoparticles. The functionalization of the magnetite nanoparticles with a self‐assembled monolayer of hexadecylphosphonic acid renders the nanoparticles oleophilic and the magnetic nature of magnetite allows for simple extraction of the hydrocarbon‐soaked sorbent. The sorbent material is capable of extracting single contaminants such as alkanes and aromatics and complex hydrocarbon mixtures such as crude oils in high extraction rates of up to 14 times the sorbent volume. Experimental results are explained by molecular dynamics simulations on the adsorption of single components from a hydrocarbon‐water mixture to the alkylphosphonic acid layer on the nanoparticles. The core–shell sorbent material is highly stable and therefore, reusable over several successive extraction cycles without degradation. The extraction performance is determined at different water temperatures, different water sources, and different magnetic core materials and evaluated compared to heptadecanoic acid functionalized magnetite. The new sorbent material provides the opportunity for an efficient, reliable, inexpensive, and environmental friendly removal of hydrocarbons from water. 相似文献
102.
Hiroyuki Koide Satoshi Hirano Takafumi Ide Kazuhiro Saito Hikaru Suzuki Go Yasuno Yoshitaka Hamashima Sei Yonezawa Naoto Oku Tomohiro Asai 《Advanced functional materials》2021,31(3):2005641
Protein affinity reagents (e.g., antibodies) are often used for basic research, diagnostics, separations, and disease therapy. Although a lot of “synthetic” protein affinity reagents have been developed as a cost-effective alternative to antibodies, their low biocompatibility is a considerable problem for clinical application. Lipid nanoparticles (LNP) represent a highly biocompatible drug delivery agent. However, little has been reported that LNP itself works as a protein affinity reagent in living animals. Here, LNP is engineered for binding to and neutralizing a target toxic peptide in living animals by multifunctionalization with amino acid derivatives. Multifunctionalized LNP (MF-LNP) is prepared using amino acid derivative-conjugated lipids. Optimized MF-LNP exhibits nanomolar affinity to the target toxic peptide and inhibits toxic peptide-dependent hemolysis and cytotoxicity. In addition, MF-LNP captures and neutralizes the toxic peptide after intravenous injection in the bloodstream; in addition, MF-LNP does not release the toxic peptide in the accumulated organ. These results reveal the potential of using LNP as a highly biocompatible protein affinity reagent such as an antidote. 相似文献
103.
Ashit Rao Subhash C. Ayirala Mohammed B. Alotaibi Michel H. G. Duits A. A. Yousef Frieder Mugele 《Advanced functional materials》2021,31(51):2106396
Dissolution is inherent to fluid-mineral systems. Yet its impact on minerals reacting with electrolytes is overlooked. Here, a novel nonmonotonic behavior for the surface interactions of carbonates (calcite and Mg-calcite) with organic acids is reported. Applying a bioinspired approach, Mg-calcite sensors via amorphous precursors, avoiding any preconditioning with functional groups are synthesized. A quartz crystal microbalance is used to study the mass changes of the mineral on contact with organic acids under varying ionic conditions, temperatures, and flow velocities. Supported by confocal Raman microscopy and potentiometric titrations, nonmonotonous mass developments are found as a function of Ca2+ concentration and flowrate, and attributed to three coupled chemical reactions: i) carbonate dissolution via Ca2+ ion complexation with organic molecules, and the formation of organo-calcium compounds as ii) a surface phase at the mineral–water interface, and iii) particles in the bulk fluid. These processes depend on local ion contents and the precipitation onset (i.e., saturation index) of organo-calcium salts, both of which substantially differ in the bulk fluid and in the fluid boundary layer at mineral interfaces. This continuum between dissolution and precipitation provides a conceptual framework to address reactions at mineral interfacial across disciplines including biomineralization, ocean acidification and reservoir geochemistry. 相似文献
104.
研究了固体有机样品的太赫兹介电谱与组分体积含量之间的关系。通过分析有效介质理论中的CRI(Complex Refractive Index)模型,得到样品的介电参数与组分体积含量的关系式。利用太赫兹时域光谱技术测得室温下两种氨基酸样品在0.5~2.7 THz的介电性质,样品的折射率、介电系数及介电损耗均随氨基酸体积含量增加而增大。选取氨基酸介电损耗谱特征峰位处的介电参数,根据CRI模型进行拟合,得到折射率与体积含量的线性关系式,介电系数和介电损耗与体积含量的二次函数关系式。研究结果有利于扩展太赫兹波段的定性定量分析手段,并对聚合物基复合材料制备有一定参考意义。 相似文献
105.
Hyungjin Kim Tomofumi Uto Takami Akagi Masanori Baba Mitsuru Akashi 《Advanced functional materials》2010,20(22):3925-3931
Size‐regulated amphiphilic poly(amino acid) nanoparticles (NPs) composed of poly(γ‐glutamic acid) (γ‐PGA) and the hydrophobic amino acid derivative, L ‐phenylalanine ethyl ester (Phe) are prepared to evaluate the effects of particle size on dendritic cell (DC) uptake of NPs and their immune stimulatory activities as delivery carriers and adjuvants. The size of the Phe‐conjugated γ‐PGA NPs (γ‐PGA–Phe NPs) is easily controlled by regulating the aggregated γ‐PGA–Phe numbers. Each of the differently sized γ‐PGA–Phe NPs could efficiently encapsulate ovalbumin (OVA), and the amount of encapsulated OVA per milligram of NPs is almost the same despite the differences in size. The DC uptake of small NPs is lower than for the larger NPs, but the effect of DC activation by NPs is high in the small sizes. The DC activation is significantly affected by the size of the NPs, which suggests that not only the uptake process of the NPs, but also the surface interactions between the NPs and DCs, is important for the induction of DC maturation. The precisely size‐controllable γ‐PGA–Phe NPs have significant potential as an antigen carrier and vaccine adjuvant. These results should provide guidelines for adjuvant design in the development of an effective vaccine. 相似文献
106.
An Effective Approach for High‐Efficiency Photoelectrochemical Solar Cells by Using Bifunctional DNA Molecules Modified Photoanode 下载免费PDF全文
Özlem Ateş Sönmezoğlu Seçkin Akın Begüm Terzi Serdal Mutlu Savaş Sönmezoğlu 《Advanced functional materials》2016,26(47):8776-8783
This paper firstly reports the effect of deoxyribonucleic acid (DNA) molecules extracted from chickpea and wheat plants on the injection/recombination of photogenerated electrons and sensitizing ability of dye‐sensitized solar cells (DSSCs). These high‐yield DNA molecules are applied as both linker bridging unit as well as thin tunneling barrier (TTB) at titanium dioxide (TiO2 )/dye interface, to build up high‐efficient DSSCs. With its favorable energy levels, effective linker bridging role, and double helix structure, bifunctional DNA modifier shows an efficient electron injection, suppressed charge recombination, longer electron lifetime, and higher light harvesting efficiency, which leads to higher photovoltaic performance. In particular, a photoconversion efficiency (PCE) of 9.23% is achieved by the binary chickpea and wheat DNA‐modified TiO2 (CW@TiO2) photoanode. Furthermore, time‐resolved fluorescence spectroscopy measurements confirm a better electron transfer kinetics for DNA‐modified TiO2 photoanodes, implying a higher electron transfer rate (kET). This work highlights a great contribution for the photoanodes that are linked with DNA molecule, which act as both bridging unit and TTB to control the charge recombination and injection dynamics, and hence, boost the photovoltaic performance in the DSSCs. 相似文献
107.
综述了近年来以氨基酸为手性源在合成手性生物碱、手性氨基醇、手性氨基醛和手性催化剂等化合物中的研究现状,并对氨基酸作为手性源在有机合成中的应用前景进行了展望。 相似文献
108.
M. GOBBETTI M. S. SIMONETTI J. ROSSI L COSSIGNANI A. CORSETTI P. DAMIANI 《Journal of food science》1994,59(4):881-884
The evolution of free D- and L-amino acids in sourdoughs started with various lactic acid bacteria (LAB) and yeasts was studied. Lactobacillus brevis subsp. lindneri CB1 and Lactobacillus plantrum DC400 had high proteolytic activity. During sourdough fermentation, Saccharomyces cerevisiae 141 and Saccharomyces exiguus M14 sequentially utilized free amino acids produced by bacterial activity. Due to increased cell yeast autolysis, more S. exiguus M14 inocula caused more free amino acids which were partially utilized by LAB without causing hydrolysis of wheat flour protein. D-alanine, D-glutamic acid and traces of other D-isomers were observed in sourdoughs fermented with L. brevis subsp. lindneri CB1 and S. cerevisiae 141. Free total D- and L-amino acid content decreased by more than 44% after baking the sourdoughs. No abiotic generation of new D-amino acid isomers was detected in the baked sourdoughs. 相似文献
109.
ALEJANDRO G. MARANGONI 《Journal of food science》1994,59(5):1096-1099
Candida rugosa lipase (CRL) and Pseudomonas fluorescein lipase (PFL) were used to hydrolyze a low-melting point butteroil fraction in the absence of orgaic solvents. CRL and PFL displayed pH activity optima of 6.7 and 7.8, and temperature-activity optima of 40–50°C and 35°C, respectively. Maximum activity for PFL was observed at 5% (v/v) water content. CRL showed higher specificity towards butyric acid relative to PFL after 3 hours of hydrolysis at 40°C (22.3 mol% vs 7.8 mol%, respectively). Both enzymes displayed, however, high specificities towards palmitic and oleic acids. CRL's inherent specificity towards butyric acid makes it an ideal choice for a biological catalyst to generate useful dairy flavor profiles. 相似文献
110.