全文获取类型
收费全文 | 625737篇 |
免费 | 10115篇 |
国内免费 | 1891篇 |
专业分类
电工技术 | 11881篇 |
综合类 | 872篇 |
化学工业 | 90753篇 |
金属工艺 | 21746篇 |
机械仪表 | 17795篇 |
建筑科学 | 16700篇 |
矿业工程 | 1573篇 |
能源动力 | 17834篇 |
轻工业 | 62222篇 |
水利工程 | 5107篇 |
石油天然气 | 4875篇 |
武器工业 | 21篇 |
无线电 | 81145篇 |
一般工业技术 | 116916篇 |
冶金工业 | 120374篇 |
原子能技术 | 9432篇 |
自动化技术 | 58497篇 |
出版年
2021年 | 4247篇 |
2019年 | 4101篇 |
2018年 | 6691篇 |
2017年 | 6595篇 |
2016年 | 6929篇 |
2015年 | 5400篇 |
2014年 | 8995篇 |
2013年 | 29871篇 |
2012年 | 15562篇 |
2011年 | 22018篇 |
2010年 | 17212篇 |
2009年 | 19565篇 |
2008年 | 20887篇 |
2007年 | 21016篇 |
2006年 | 18671篇 |
2005年 | 17287篇 |
2004年 | 16832篇 |
2003年 | 16402篇 |
2002年 | 15891篇 |
2001年 | 15934篇 |
2000年 | 13840篇 |
1999年 | 15029篇 |
1998年 | 36376篇 |
1997年 | 26265篇 |
1996年 | 20351篇 |
1995年 | 16398篇 |
1994年 | 14785篇 |
1993年 | 14176篇 |
1992年 | 10538篇 |
1991年 | 10121篇 |
1990年 | 9691篇 |
1989年 | 9284篇 |
1988年 | 8949篇 |
1987年 | 7531篇 |
1986年 | 7632篇 |
1985年 | 9149篇 |
1984年 | 8425篇 |
1983年 | 7591篇 |
1982年 | 7008篇 |
1981年 | 7081篇 |
1980年 | 6634篇 |
1979年 | 6424篇 |
1978年 | 6000篇 |
1977年 | 7322篇 |
1976年 | 9806篇 |
1975年 | 5152篇 |
1974年 | 4932篇 |
1973年 | 4852篇 |
1972年 | 3929篇 |
1971年 | 3418篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Vlad F. Avram Imen Chamkha Eleonor sander-Frostner Johannes K. Ehinger Romulus Z. Timar Magnus J. Hansson Danina M. Muntean Eskil Elmr 《International journal of molecular sciences》2021,22(1)
Statins are the cornerstone of lipid-lowering therapy. Although generally well tolerated, statin-associated muscle symptoms (SAMS) represent the main reason for treatment discontinuation. Mitochondrial dysfunction of complex I has been implicated in the pathophysiology of SAMS. The present study proposed to assess the concentration-dependent ex vivo effects of three statins on mitochondrial respiration in viable human platelets and to investigate whether a cell-permeable prodrug of succinate (complex II substrate) can compensate for statin-induced mitochondrial dysfunction. Mitochondrial respiration was assessed by high-resolution respirometry in human platelets, acutely exposed to statins in the presence/absence of the prodrug NV118. Statins concentration-dependently inhibited mitochondrial respiration in both intact and permeabilized cells. Further, statins caused an increase in non-ATP generating oxygen consumption (uncoupling), severely limiting the OXPHOS coupling efficiency, a measure of the ATP generating capacity. Cerivastatin (commercially withdrawn due to muscle toxicity) displayed a similar inhibitory capacity compared with the widely prescribed and tolerable atorvastatin, but did not elicit direct complex I inhibition. NV118 increased succinate-supported mitochondrial oxygen consumption in atorvastatin/cerivastatin-exposed platelets leading to normalization of coupled (ATP generating) respiration. The results acquired in isolated human platelets were validated in a limited set of experiments using atorvastatin in HepG2 cells, reinforcing the generalizability of the findings. 相似文献
102.
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
103.
Skeletal muscle is an essential organ, responsible for many physiological functions such as breathing, locomotion, postural maintenance, thermoregulation, and metabolism. Interestingly, skeletal muscle is a highly plastic tissue, capable of adapting to anabolic and catabolic stimuli. Skeletal muscle contains a specialized smooth endoplasmic reticulum (ER), known as the sarcoplasmic reticulum, composed of an extensive network of tubules. In addition to the role of folding and trafficking proteins within the cell, this specialized organelle is responsible for the regulated release of calcium ions (Ca2+) into the cytoplasm to trigger a muscle contraction. Under various stimuli, such as exercise, hypoxia, imbalances in calcium levels, ER homeostasis is disturbed and the amount of misfolded and/or unfolded proteins accumulates in the ER. This accumulation of misfolded/unfolded protein causes ER stress and leads to the activation of the unfolded protein response (UPR). Interestingly, the role of the UPR in skeletal muscle has only just begun to be elucidated. Accumulating evidence suggests that ER stress and UPR markers are drastically induced in various catabolic stimuli including cachexia, denervation, nutrient deprivation, aging, and disease. Evidence indicates some of these molecules appear to be aiding the skeletal muscle in regaining homeostasis whereas others demonstrate the ability to drive the atrophy. Continued investigations into the individual molecules of this complex pathway are necessary to fully understand the mechanisms. 相似文献
104.
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
105.
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
106.
107.
Qudavasov Sh. K. Abdullayev N. A. Jalilli J. N. Badalova Z. I. Mamedova I. A. Nemov S. A. 《Semiconductors》2021,55(12):985-988
Semiconductors - By spectroscopic ellipsometry, the imaginary and real parts of the dielectric functions of Bi2Se3 and Bi2Se3〈Cu〉 single crystals are obtained in the photon-energy... 相似文献
108.
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
109.
Samuel J. Bunce Yiming Wang Sheena E. Radford Andrew J. Wilson Carol K. Hall 《American Institute of Chemical Engineers》2021,67(3):e17101
Determining the structure of the (oligomeric) intermediates that form during the self-assembly of amyloidogenic peptides is challenging because of their heterogeneous and dynamic nature. Thus, there is need for methodology to analyze the underlying molecular structure of these transient species. In this work, a combination of fluorescence quenching, photo-induced crosslinking (PIC) and molecular dynamics simulation was used to study the assembly of a synthetic amyloid-forming peptide, Aβ16-22. A PIC amino acid containing a trifluormethyldiazirine (TFMD) group—Fmoc(TFMD)Phe—was incorporated into the sequence (Aβ*16–22). Electrospray ionization ion-mobility spectrometry mass-spectrometry (ESI-IMS-MS) analysis of the PIC products confirmed that Aβ*16–22 forms assemblies with the monomers arranged as anti-parallel, in-register β-strands at all time points during the aggregation assay. The assembly process was also monitored separately using fluorescence quenching to profile the fibril assembly reaction. The molecular picture resulting from discontinuous molecule dynamics simulations showed that Aβ16-22 assembles through a single-step nucleation into a β-sheet fibril in agreement with these experimental observations. This study provides detailed structural insights into the Aβ16-22 self-assembly processes, paving the way to explore the self-assembly mechanism of larger, more complex peptides, including those whose aggregation is responsible for human disease. 相似文献
110.
Roselin Kiruba R. Sree Sharmila T. 《Multidimensional Systems and Signal Processing》2021,32(2):405-430
Multidimensional Systems and Signal Processing - The recent growth of World Wide Web (WWW) and development of the next-generation internet facilitates a huge amount of data being conveniently... 相似文献