全文获取类型
收费全文 | 257367篇 |
免费 | 4699篇 |
国内免费 | 1780篇 |
学科分类
工业技术 | 263846篇 |
出版年
2021年 | 2389篇 |
2019年 | 2097篇 |
2018年 | 3370篇 |
2017年 | 3334篇 |
2016年 | 3664篇 |
2015年 | 2791篇 |
2014年 | 4560篇 |
2013年 | 11327篇 |
2012年 | 7679篇 |
2011年 | 10180篇 |
2010年 | 8110篇 |
2009年 | 8662篇 |
2008年 | 9468篇 |
2007年 | 9582篇 |
2006年 | 8429篇 |
2005年 | 7384篇 |
2004年 | 6653篇 |
2003年 | 6200篇 |
2002年 | 6203篇 |
2001年 | 6291篇 |
2000年 | 5567篇 |
1999年 | 5599篇 |
1998年 | 12587篇 |
1997年 | 9308篇 |
1996年 | 6993篇 |
1995年 | 5467篇 |
1994年 | 5045篇 |
1993年 | 4909篇 |
1992年 | 3897篇 |
1991年 | 3711篇 |
1990年 | 3797篇 |
1989年 | 3721篇 |
1988年 | 3485篇 |
1987年 | 2982篇 |
1986年 | 3015篇 |
1985年 | 3391篇 |
1984年 | 3295篇 |
1983年 | 3042篇 |
1982年 | 2675篇 |
1981年 | 2867篇 |
1980年 | 2624篇 |
1979年 | 2821篇 |
1978年 | 2722篇 |
1977年 | 2826篇 |
1976年 | 3680篇 |
1975年 | 2442篇 |
1974年 | 2281篇 |
1973年 | 2309篇 |
1972年 | 1974篇 |
1971年 | 1776篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Alexander Haseloer Tamara Lützenburg Joss Pepe Strache Dr. Jörg Neudörfl Prof. Dr. Ines Neundorf Prof. Dr. Axel Klein 《Chembiochem : a European journal of chemical biology》2021,22(4):694-704
Three chiral tridentate N^N^S coordinating pyridine-carbaldehyde (S)-N4-(α-methylbenzyl)thiosemicarbazones (HTSCmB) were synthesised along with lysine-modified derivatives. One of them was selected and covalently conjugated to the cell-penetrating peptide sC18 by solid-phase peptide synthesis. The HTSCmB model ligands, the HTSCLp derivatives and the peptide conjugate rapidly and quantitatively form very stable PtII chlorido complexes [Pt(TSC)Cl] when treated with K2PtCl4 in solution. The Pt(CN) derivatives were obtained from one TSCmB model complex and the peptide conjugate complex through Cl−→CN− exchange. Ligands and complexes were characterised by NMR, IR spectroscopy, HR-ESI-MS and single-crystal XRD. Intriguingly, no decrease in cell viability was observed when testing the biological activity of the lysine-tagged HdpyTSCLp, its sC18 conjugate HdpyTSCL-sC18 or the PtCl and Pt(CN) conjugate complexes in three different cell lines. Thus, given the facile and effective preparation of such Pt-TSC-peptide conjugates, these systems might pave the way for future use in late-stage labelling with Pt radionuclides and application in nuclear medicine. 相似文献
52.
Dresvyannikov A. F. Petrova E. V. Akhmetova A. N. Kashfrazieva L. I. Tverdov I. D. 《Glass Physics and Chemistry》2021,47(5):489-495
Glass Physics and Chemistry - The scientific foundations for the synthesis of precursors of nanostructured oxide systems Al2O3–ZrO2–MxOy (M = Mg, Y) are developed. The processes... 相似文献
53.
Emil Märcher Rørsted Dr. Anders A. Jensen Prof. Jesper L. Kristensen 《ChemMedChem》2021,16(21):3263-3270
4-(2-((2-hydroxybenzyl)amino)ethyl)-2,5-dimethoxybenzonitrile (25CN-NBOH) was first reported as a potent and selective serotonin 2A receptor (5-HT2AR) agonist in 2014, and it has since found extensive use as a pharmacological tool in a variety of in vitro, ex vivo and in vivo studies. 25CN-NBOH is readily available from a synthetic perspective using standard chemical transformations, and displays favorable physiochemical properties in terms of stability and solubility. Due to its superior selectivity for 5-HT2AR, 25CN-NBOH has been used to investigate the effects of selective 5-HT2AR activation in vivo, and has thus become an important pharmacological tool for the exploration of 5-HT2AR signaling in a range of animal models. In the present review, we outline the discovery of 25CN-NBOH, its pharmacological profile and major findings from studies where it has been used. 相似文献
54.
L. Gale S. Harris S. Pattison J. Baker J. Fowler 《Journal of the European Ceramic Society》2021,41(5):3167-3176
SiC/SiC ceramic matrix composites (CMCs) are being developed for use in aero-engines to replace nickel superalloy components. Sub-element testing acts as the key stepping stone in bridging understanding derived from basic coupon testing and more complex component testing. This study presents the development of high temperature C-shape sub-element testing with the use of digital image correlation to study damage progression. The specimen is designed with a bias towards a mixed mode-stress state more similar to what a CMC component may see in service. Both monotonic and fatigue tests were completed on C specimens and compared with predicted behaviour from modelling. Test data from both test types suggested that specimens were failing once they reached a critical radial stress level. However evidence from fractography of specimens showed that in both monotonic and fatigue tests radial cracks (driven by hoop stresses) are initiating prior to circumferential cracks. 相似文献
55.
Rebecca L. Walton Michael J. Brova Beecher H. Watson Elizabeth R. Kupp Mark A. Fanton Richard J. Meyer Gary L. Messing 《Journal of the European Ceramic Society》2021,41(3):1945-1953
Direct writing is a unique means to align anisotropic particles for the fabrication of textured ceramics by templated grain growth (TGG). We show that alignment of tabular barium titanate (BT) template particles (20–40 μm width and 0.5–2 μm thickness) in a PIN-PMN-PT matrix powder (d50 = 280 nm) is significantly improved during direct writing using anisotropic nozzles at high printing rates. The particle orientation distribution in as-printed filaments, and the texture orientation distribution in sintered ceramic filaments are shown to directly correlate with COMSOL Multiphysics-predicted torque distributions for direct writing with aspect ratio 2, 3 and 5 oval nozzles. Electromechanical strain properties of the textured piezoelectric ceramics significantly improved relative to random ceramics when printed with anisotropic nozzles. Simulations of aspect ratio 20 nozzles and nozzles with interior baffles demonstrate significantly increased torque and near elimination of constant shear stress cores (i.e. plug flow). 相似文献
56.
Automation and Remote Control - We consider the NP-hard integer three-index axial assignment problem. The task of optimal combination of the pairs of feasible solutions of the problem is posed, and... 相似文献
57.
58.
Currently, the efficient detection of fingerprints is essential for the crime investigations. Revealing fingerprints is commonly achieved with fluorescent organic compounds but they are not efficient for fingerprint detection on porous or reflective surfaces. In order to solve the problem of collecting fingerprints on porous/reflective surfaces, inorganic phosphors have been employed, since they have characteristics of variable color emission, afterglow, high chemical stability and nano-size, which allow the fingerprint detection on any porous or non-porous surfaces. Due to these last properties, this review presents a summary about the use of phosphorescent and fluorescent phosphors for the detection of latent fingerprints. First, we discussed the main physical and chemical characteristics of the fingerprints which permit their detection and collection from any surface. After this, we presented the main morphological, structural and luminescent properties of the phosphorescent and fluorescent phosphors that allow their use for fingerprint detection. Later, we demonstrated with pictures of fingerprints (with and without light emission from the phosphors deposited on them) that both, phosphorescent and fluorescent phosphors can be used to visualize fingerprints with high resolution and high contrast without interference of the background surface, which is ideal for its collection and registration in the Automated Fingerprint Identification System (AFIS). We believe that this review could be useful to understand how to select an appropriate phosphorescent or fluorescent material for fingerprint detection depending on the type of surface (porous or non-porous, reflective or not reflective) where the fingerprint is deposited. 相似文献
59.
Tarasova E. A. Khazanova S. V. Golikov O. L. Puzanov A. S. Obolensky S. V. Zemlyakov V. E. 《Semiconductors》2021,55(12):895-898
Semiconductors - The paper presents the results of modeling the electrophysical parameters of AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (pHEMT) structures via... 相似文献
60.
David J. Lawrence Brianna L. Smith Cameron D. Collard Keyton A. Elliott Kyle L. Fakhoury Jeffery D. Mangold Anna N. Soyka 《International Journal of Hydrogen Energy》2021,46(2):1642-1655
Monolithically-integrated tandem photoanodes were fabricated on substrates consisting of epitaxial n-GaAs1-xPx (x ? 0.32) grown on n+-GaAs wafers. A p+-n junction photovoltaic (PV) cell was first formed by zinc diffusion into the n-GaAs0.68P0.32 from a deposited ZnO coating. After diffusion the ZnO serves as a transparent electrical contact to the resulting p+-GaAs0.68P0.32 surface layer. Transparent, conducting SnO2:F provides chemical and mechanical protection for the ZnO and the underlying PV cell, and it electrically connects this cell to a top BiVO4 photocatalyst layer. In some photoanodes, a WO3 thin film was interposed between the SnO2:F and BiVO4. All oxide coatings were produced by ultrasonic spray pyrolysis except WO3, which was spin coated. Unassisted (unbiased) solar water splitting was achieved, with a solar-to-hydrogen efficiency approaching 2%, without addition of any co-catalyst to the BiVO4 surface. This work can provide insights to other researchers regarding scalable, low cost approaches for the planar monolithic integration of oxide photoanode materials with PV cells to create new tandem devices. 相似文献