全文获取类型
收费全文 | 513575篇 |
免费 | 9557篇 |
国内免费 | 1806篇 |
专业分类
电工技术 | 8460篇 |
综合类 | 2675篇 |
化学工业 | 74837篇 |
金属工艺 | 19057篇 |
机械仪表 | 15207篇 |
建筑科学 | 14339篇 |
矿业工程 | 1455篇 |
能源动力 | 12799篇 |
轻工业 | 50384篇 |
水利工程 | 4709篇 |
石油天然气 | 2080篇 |
武器工业 | 17篇 |
无线电 | 65728篇 |
一般工业技术 | 95951篇 |
冶金工业 | 84803篇 |
原子能技术 | 5985篇 |
自动化技术 | 66452篇 |
出版年
2021年 | 3255篇 |
2020年 | 2450篇 |
2019年 | 3034篇 |
2018年 | 18587篇 |
2017年 | 17653篇 |
2016年 | 14739篇 |
2015年 | 4881篇 |
2014年 | 7109篇 |
2013年 | 21710篇 |
2012年 | 14989篇 |
2011年 | 25048篇 |
2010年 | 20246篇 |
2009年 | 19150篇 |
2008年 | 21510篇 |
2007年 | 22602篇 |
2006年 | 13861篇 |
2005年 | 13845篇 |
2004年 | 13316篇 |
2003年 | 13006篇 |
2002年 | 11974篇 |
2001年 | 10813篇 |
2000年 | 9882篇 |
1999年 | 10556篇 |
1998年 | 25781篇 |
1997年 | 18496篇 |
1996年 | 14156篇 |
1995年 | 11412篇 |
1994年 | 10133篇 |
1993年 | 9718篇 |
1992年 | 7170篇 |
1991年 | 6856篇 |
1990年 | 6470篇 |
1989年 | 6159篇 |
1988年 | 5902篇 |
1987年 | 4935篇 |
1986年 | 4904篇 |
1985年 | 6057篇 |
1984年 | 5657篇 |
1983年 | 4862篇 |
1982年 | 4561篇 |
1981年 | 4530篇 |
1980年 | 4266篇 |
1979年 | 4133篇 |
1978年 | 3819篇 |
1977年 | 4653篇 |
1976年 | 6372篇 |
1975年 | 3150篇 |
1974年 | 3027篇 |
1973年 | 2925篇 |
1972年 | 2338篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
M.L. Puga J. Venturini W.C. Guaglianoni T.L. Ruwer T.B. Wermuth C.P. Bergmann 《Ceramics International》2021,47(13):18358-18366
Titanium dioxide (TiO2) application in light-harvesting processes is hindered by its wide band gap. Strategies such as morphology shifts from nanoparticles to nanotubes and doping of fabricated nanostructures are widely used to address this issue. Combining both approaches, this work successfully synthesizes, for the first time, aluminium-doped TiO2 nanotubes via a single-step anodization method at three distinct potentials (20, 40 and 60 V). SEM images revealed the successful formation of remarkably thin layers of TiO2 nanotubes produced at 40 and 60 V. X-ray diffractograms and Raman spectra suggest the successful insertion of aluminium into the anatase lattice. Diffuse reflectance confirmed the doping process through a marked effect on the absorbance of visible light for the higher voltages, as well as through a reduction in the optical band gap. For utilization purposes, the photoelectrochemical performance of 40 V Al–TiO2 was able to deliver a comparable response to that of a compact TiO2 layer of the same thickness. The current density developed by the 60 V sample was increased by 120% in comparison to the undoped material, despite having an absorbance much lower than that of the latter. Overall, synthesizing an Al-doped TiO2 nanotubular structure has proven to be a great strategy in the development of materials for application in advanced light-harvesting electrodes. 相似文献
102.
Dr. Walter D. Guerra Dr. Daniel Lucena-Agell Rafael Hortigüela Prof. Roberto A. Rossi Dr. J. Fernando Díaz Prof. José M. Padrón Dr. Silvia M. Barolo 《ChemMedChem》2021,16(19):3003-3016
We prepared a series of free NH and N-substituted dibenzonthiazines with potential anti-tumor activity from N-aryl-benzenesulfonamides. A biological test of synthesized compounds (59 samples) was performed in vitro measuring their antiproliferative activity against a panel of six human solid tumor cell lines and its tubulin inhibitory activity. We identified 6-(phenylsulfonyl)-6H-dibenzo[c,e][1,2]thiazine 5,5-dioxide and 6-tosyl-6H-dibenzo[c,e][1,2]thiazine 5,5-dioxide as the best compounds with promising values of activity (overall range of 2–5.4 μM). Herein, we report the dibenzothiazine core as a novel building block with antiproliferative activity, targeting tubulin dynamics. 相似文献
103.
Dr. Alejandra A. Carriles Alberto Mills Dr. María-José Muñoz-Alonso Dr. Dolores Gutiérrez Dr. Juan M. Domínguez Prof. Dr. Juan A. Hermoso Prof. Dr. Federico Gago 《Chembiochem : a European journal of chemical biology》2021,22(2):374-391
Spontaneous mutations in the EEF1A2 gene cause epilepsy and severe neurological disabilities in children. The crystal structure of eEF1A2 protein purified from rabbit skeletal muscle reveals a post-translationally modified dimer that provides information about the sites of interaction with numerous binding partners, including itself, and maps these mutations onto the dimer and tetramer interfaces. The spatial locations of the side chain carboxylates of Glu301 and Glu374, to which phosphatidylethanolamine is uniquely attached via an amide bond, define the anchoring points of eEF1A2 to cellular membranes and interorganellar membrane contact sites. Additional bioinformatic and molecular modeling results provide novel structural insight into the demonstrated binding of eEF1A2 to SH3 domains, the common MAPK docking groove, filamentous actin, and phosphatidylinositol-4 kinase IIIβ. In this new light, the role of eEF1A2 as an ancient, multifaceted, and articulated G protein at the crossroads of autophagy, oncogenesis and viral replication appears very distant from the “canonical” one of delivering aminoacyl-tRNAs to the ribosome that has dominated the scene and much of the thinking for many decades. 相似文献
104.
Daniel J. Owens Julien Messant Sophie Moog Mark Viggars Arnaud Ferry Kamel Mamchaoui Emmanuelle Lacne Norma Romro Astrid Brull Gisle Bonne Gillian Butler-Browne Catherine Coirault 《International journal of molecular sciences》2021,22(1)
Laminopathies are a clinically heterogeneous group of disorders caused by mutations in the LMNA gene, which encodes the nuclear envelope proteins lamins A and C. The most frequent diseases associated with LMNA mutations are characterized by skeletal and cardiac involvement, and include autosomal dominant Emery–Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy type 1B, and LMNA-related congenital muscular dystrophy (LMNA-CMD). Although the exact pathophysiological mechanisms responsible for LMNA-CMD are not yet understood, severe contracture and muscle atrophy suggest that mutations may impair skeletal muscle growth. Using human muscle stem cells (MuSCs) carrying LMNA-CMD mutations, we observe impaired myogenic fusion with disorganized cadherin/β catenin adhesion complexes. We show that skeletal muscle from Lmna-CMD mice is unable to hypertrophy in response to functional overload, due to defective fusion of activated MuSCs, defective protein synthesis and defective remodeling of the neuromuscular junction. Moreover, stretched myotubes and overloaded muscle fibers with LMNA-CMD mutations display aberrant mechanical regulation of the yes-associated protein (YAP). We also observe defects in MuSC activation and YAP signaling in muscle biopsies from LMNA-CMD patients. These phenotypes are not recapitulated in closely related but less severe EDMD models. In conclusion, combining studies in vitro, in vivo, and patient samples, we find that LMNA-CMD mutations interfere with mechanosignaling pathways in skeletal muscle, implicating A-type lamins in the regulation of skeletal muscle growth. 相似文献
105.
Corey R. Nelson Tyler Mrozowich Sean M. Park Simmone Dsouza Amy Henrickson Justin R. J. Vigar Hans-Joachim Wieden Raymond J. Owens Borries Demeler Trushar R. Patel 《International journal of molecular sciences》2021,22(1)
Rift Valley fever virus (RVFV) is a mosquito-transmitted virus from the Bunyaviridae family that causes high rates of mortality and morbidity in humans and ruminant animals. Previous studies indicated that DEAD-box helicase 17 (DDX17) restricts RVFV replication by recognizing two primary non-coding RNAs in the S-segment of the genome: the intergenic region (IGR) and 5′ non-coding region (NCR). However, we lack molecular insights into the direct binding of DDX17 with RVFV non-coding RNAs and information on the unwinding of both non-coding RNAs by DDX17. Therefore, we performed an extensive biophysical analysis of the DDX17 helicase domain (DDX17135–555) and RVFV non-coding RNAs, IGR and 5’ NCR. The homogeneity studies using analytical ultracentrifugation indicated that DDX17135–555, IGR, and 5’ NCR are pure. Next, we performed small-angle X-ray scattering (SAXS) experiments, which suggested that DDX17 and both RNAs are homogenous as well. SAXS analysis also demonstrated that DDX17 is globular to an extent, whereas the RNAs adopt an extended conformation in solution. Subsequently, microscale thermophoresis (MST) experiments were performed to investigate the direct binding of DDX17 to the non-coding RNAs. The MST experiments demonstrated that DDX17 binds with the IGR and 5’ NCR with a dissociation constant of 5.77 ± 0.15 µM and 9.85 ± 0.11 µM, respectively. As DDX17135–555 is an RNA helicase, we next determined if it could unwind IGR and NCR. We developed a helicase assay using MST and fluorescently-labeled oligos, which suggested DDX17135–555 can unwind both RNAs. Overall, our study provides direct evidence of DDX17135–555 interacting with and unwinding RVFV non-coding regions. 相似文献
106.
Andrew N. Kuhn Haidong Zhao Uzoma O. Nwabara Xiaofei Lu Mingyan Liu Yung-Tin Pan Wenjin Zhu Paul J. A. Kenis Hong Yang 《Advanced functional materials》2021,31(26):2101668
Copper catalysts are widely studied for the electroreduction of carbon dioxide (CO2) to value-added hydrocarbon products. Controlling the surface composition of copper nanomaterials may provide the electronic and structural properties necessary for carbon-carbon coupling, thus increasing the Faradaic efficiency (FE) towards ethylene and other multi-carbon (C2+) products. Synthesis and catalytic study of silver-coated copper nanoparticles (Cu@Ag NPs) for the reduction of CO2 are presented. Bimetallic CuAg NPs are typically difficult to produce due to the bulk immiscibility between these two metals. Slow injection of the silver precursor, concentrations of organic capping agents, and gas environment proved critical to control the size and metal distribution of the Cu@Ag NPs. The optimized Cu@Ag electrocatalyst exhibited a very low onset cell potential of −2.25 V for ethylene formation, reaching a FE towards C2+ products (FEC2+) of 43% at −2.50 V, which is 1.0 V lower than a reference Cu catalyst to reach a similar FEC2+. The high ethylene formation at low potentials is attributed to enhanced C C coupling on the Ag enriched shell of the Cu@Ag electrocatalysts. This study offers a new catalyst design towards increasing the efficiency for the electroreduction of CO2 to value-added chemicals. 相似文献
107.
Camila C. Lopes Wagner A. Pinheiro Daniel Navarro da Rocha José G. Neves Américo Bortolazzo Correr José R.M. Ferreira Rafael M. Barbosa Jefferson R.F. Soares Jheison L. Santos Marcelo H. Prado da Silva 《Ceramics International》2021,47(6):7653-7665
The repair of bone fractures is a clinical challenge for patients with impaired healing, such as osteoporosis. Currently, different strategies have been developed to design new biomaterials, enhancing their interactions with biological systems and conducting the cellular behavior in the desired direction to help fracture healing. In the present work, hydroxyapatite-graphene oxide (HA-GO) nanocomposites were produced and the morphological and physicochemical influences of the addition of 0.5 wt%, 1.0 wt% and 1.5 wt% of GO to HA were observed. FEG-SEM and TEM analyses of HA-GO nanocomposites showed HA nanoparticles adhered to the surface of the GO sheets, suggesting an effective method to form nanostructured graphene-based biomaterials. As confirmation, physicochemical analyses by Raman, FTIR and TGA demonstrated a strong affinity between HA and GO, according to the increase of concentration from 0.5 wt% to 1.5 wt% GO in the HA-GO nanocomposites. Also, in order to evaluate the HA-GO nanocomposites behavior under biological microenvironment, in vitro bioactivity and indirect cytotoxicity tests were performed. FEG-SEM analyses confirmed the positive results for the bioactivity properties of HA-GO nanocomposite and indirect cytotoxicity demonstrated that even with a decrease in the hDPSCs viability and proliferation, when increasing to 1.5 wt% of GO concentration, high level of cell viability was exhibited by HA-GO nanocomposites. These biological results suggested the 0.5 wt% HA-GO nanocomposite as a potential bioactive bone graft and a promising biomaterial for bone tissue regeneration, when compared to the pure HA. 相似文献
108.
Journal of Chemical Ecology - Complex inter-organismal communication among plants, insects, and microbes in natural and agricultural ecological systems is typically governed by emitted and... 相似文献
109.
Khai Gene Leong Elyce Ozols John Kanellis Shawn S. Badal John T. Liles David J. Nikolic-Paterson Frank Y. Ma 《International journal of molecular sciences》2021,22(1)
Cyclophilins have important homeostatic roles, but following tissue injury, cyclophilin A (CypA) can promote leukocyte recruitment and inflammation, while CypD can facilitate mitochondrial-dependent cell death. This study investigated the therapeutic potential of a selective cyclophilin inhibitor (GS-642362), which does not block calcineurin function, in mouse models of tubular cell necrosis and renal fibrosis. Mice underwent bilateral renal ischemia/reperfusion injury (IRI) and were killed 24 h later: treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. In the second model, mice underwent unilateral ureteric obstruction (UUO) surgery and were killed 7 days later; treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. GS-642362 treatment gave a profound and dose-dependent protection from acute renal failure in the IRI model. This protection was associated with reduced tubular cell death, including a dramatic reduction in neutrophil infiltration. In the UUO model, GS-642362 treatment significantly reduced tubular cell death, macrophage infiltration, and renal fibrosis. This protective effect was independent of the upregulation of IL-2 and activation of the stress-activated protein kinases (p38 and JNK). In conclusion, GS-642362 was effective in suppressing both acute kidney injury and renal fibrosis. These findings support further investigation of cyclophilin blockade in other types of acute and chronic kidney disease. 相似文献
110.
Sijie Wang Dr. Aktan Alpsoy Surbhi Sood Sandra Carolina Ordonez-Rubiano Dr. Alisha Dhiman Yixing Sun Guanming Jiao Dr. Casey J. Krusemark Dr. Emily C. Dykhuizen 《Chembiochem : a European journal of chemical biology》2021,22(13):2335-2344
Polycomb group (PcG) proteins are epigenetic regulators that facilitate both embryonic development and cancer progression. PcG proteins form Polycomb repressive complexes 1 and 2 (PRC1 and PRC2). PRC2 trimethylates histone H3 lysine 27 (H3K27me3), a histone mark recognized by the N-terminal chromodomain (ChD) of the CBX subunit of canonical PRC1. There are five PcG CBX paralogs in humans. CBX2 in particular is upregulated in a variety of cancers, particularly in advanced prostate cancers. Using CBX2 inhibitors to understand and target CBX2 in prostate cancer is highly desirable; however, high structural similarity among the CBX ChDs has been challenging for developing selective CBX ChD inhibitors. Here, we utilize selections of focused DNA encoded libraries (DELs) for the discovery of a selective CBX2 chromodomain probe, SW2_152F. SW2_152F binds to CBX2 ChD with a Kd of 80 nM and displays 24-1000-fold selectivity for CBX2 ChD over other CBX paralogs in vitro. SW2_152F is cell permeable, selectively inhibits CBX2 chromatin binding in cells, and blocks neuroendocrine differentiation of prostate cancer cell lines in response to androgen deprivation. 相似文献