全文获取类型
收费全文 | 5265篇 |
免费 | 459篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 15篇 |
综合类 | 1篇 |
化学工业 | 1886篇 |
金属工艺 | 37篇 |
机械仪表 | 104篇 |
建筑科学 | 199篇 |
矿业工程 | 10篇 |
能源动力 | 132篇 |
轻工业 | 1753篇 |
水利工程 | 48篇 |
石油天然气 | 37篇 |
无线电 | 179篇 |
一般工业技术 | 638篇 |
冶金工业 | 124篇 |
原子能技术 | 7篇 |
自动化技术 | 557篇 |
出版年
2024年 | 17篇 |
2023年 | 90篇 |
2022年 | 346篇 |
2021年 | 387篇 |
2020年 | 206篇 |
2019年 | 230篇 |
2018年 | 228篇 |
2017年 | 229篇 |
2016年 | 265篇 |
2015年 | 193篇 |
2014年 | 284篇 |
2013年 | 424篇 |
2012年 | 396篇 |
2011年 | 424篇 |
2010年 | 314篇 |
2009年 | 311篇 |
2008年 | 265篇 |
2007年 | 236篇 |
2006年 | 169篇 |
2005年 | 130篇 |
2004年 | 110篇 |
2003年 | 84篇 |
2002年 | 76篇 |
2001年 | 39篇 |
2000年 | 45篇 |
1999年 | 46篇 |
1998年 | 27篇 |
1997年 | 21篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 17篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有5727条查询结果,搜索用时 15 毫秒
41.
Maria Buuales Maria Cristina Ballesteros-Briones Manuela Gonzalez-Aparicio Sandra Hervas-Stubbs Eva Martisova Uxua Mancheo Ana Ricobaraza Sara Lumbreras Cristian Smerdou Ruben Hernandez-Alcoceba 《International journal of molecular sciences》2021,22(8)
Immune checkpoint inhibitors (ICIs) have demonstrated remarkable efficacy in a growing number of malignancies. However, overcoming primary or secondary resistances is difficult due to pharmacokinetics issues and side effects associated with high systemic exposure. Local or regional expression of monoclonal antibodies (mAbs) using gene therapy vectors can alleviate this problem. In this work, we describe a high-capacity adenoviral vector (HCA-EFZP-aPDL1) equipped with a mifepristone-inducible system for the controlled expression of an anti-programmed death ligand 1 (PD-L1) blocking antibody. The vector was tested in an immune-competent mouse model of colorectal cancer based on implantation of MC38 cells. A single local administration of HCA-EFZP-aPDL1 in subcutaneous lesions led to a significant reduction in tumor growth with minimal release of the antibody in the circulation. When the vector was tested in a more stringent setting (rapidly progressing peritoneal carcinomatosis), the antitumor effect was marginal even in combination with other immune-stimulatory agents such as polyinosinic-polycytidylic acid (pI:C), blocking mAbs for T cell immunoglobulin, mucin-domain containing-3 (TIM-3) or agonistic mAbs for 4-1BB (CD137). In contrast, macrophage depletion by clodronate liposomes enhanced the efficacy of HCA-EFZP-aPDL1. These results highlight the importance of addressing macrophage-associated immunoregulatory mechanisms to overcome resistance to ICIs in the context of colorectal cancer. 相似文献
42.
Ivn Benito Ignacio J. Encío Fermín I. Milagro María Alfaro Ana Martínez-Peuela Miguel Barajas Florencio Marzo 《International journal of molecular sciences》2021,22(9)
Recent studies have suggested that flavonoids such as quercetin and probiotics such as Bifidobacterium bifidum (Bf) and Lactobacillus gasseri (Lg) could play a relevant role in inhibiting colon cancer cell growth. Our study investigated the role of dietary supplementation with microencapsulated probiotics (Bf and Lg) along with quercetin in the development of mouse colorectal cancer (CRC). Methods: Adenomatous polyposis coli/multiple intestinal neoplasia (ApcMin/+) mice were fed a standard diet or the same diet supplemented with microencapsulated probiotics (Bf and Lg strains, 107 CFU/100 g food) or both probiotics strains plus microencapsulated quercetin (15 mg/100 g food) for 73 days. Changes in body and organ weights, energy metabolism, intestinal microbiota, and colon tissue were determined. The expression of genes related to the Wnt pathway was also analyzed in colon samples. Results: Dietary supplementation with microencapsulated probiotics or microencapsulated probiotics plus quercetin reduced body weight loss and intestinal bleeding in ApcMin/+ mice. An improvement in energy expenditure was observed after 8 weeks but not after 10 weeks of treatment. A supplemented diet with microencapsulated Bf and Lg reduced the number of aberrant crypt foci (ACF) and adenomas by 45% and 60%, respectively, whereas the supplementation with Bf, Lg and quercetin decreased the number of ACF and adenomas by 57% and 80%, respectively. Microencapsulated Bf and Lg in combination with quercetin could exert inhibition of the canonical Wnt/β-catenin signaling pathway in the colon of ApcMin/+ mice Conclusions: The administration of microencapsulated Bf and Lg, individually or in combination with quercetin, inhibits the CRC development in ApcMin/+ mice. 相似文献
43.
Pablo Bonilla Joaquim Hernandez Esther Giraldo Miguel A. Gonzlez-Prez Ana Alastrue-Agudo Hoda Elkhenany María J. Vicent Xavier Navarro Michael Edel Victoria Moreno-Manzano 《International journal of molecular sciences》2021,22(11)
We currently lack effective treatments for the devastating loss of neural function associated with spinal cord injury (SCI). In this study, we evaluated a combination therapy comprising human neural stem cells derived from induced pluripotent stem cells (iPSC-NSC), human mesenchymal stem cells (MSC), and a pH-responsive polyacetal–curcumin nanoconjugate (PA-C) that allows the sustained release of curcumin. In vitro analysis demonstrated that PA-C treatment protected iPSC-NSC from oxidative damage in vitro, while MSC co-culture prevented lipopolysaccharide-induced activation of nuclear factor-κB (NF-κB) in iPSC-NSC. Then, we evaluated the combination of PA-C delivery into the intrathecal space in a rat model of contusive SCI with stem cell transplantation. While we failed to observe significant improvements in locomotor function (BBB scale) in treated animals, histological analysis revealed that PA-C-treated or PA-C and iPSC-NSC + MSC-treated animals displayed significantly smaller scars, while PA-C and iPSC-NSC + MSC treatment induced the preservation of β-III Tubulin-positive axons. iPSC-NSC + MSC transplantation fostered the preservation of motoneurons and myelinated tracts, while PA-C treatment polarized microglia into an anti-inflammatory phenotype. Overall, the combination of stem cell transplantation and PA-C treatment confers higher neuroprotective effects compared to individual treatments. 相似文献
44.
Tracy Q. Gardner Ana I. Flores Richard D. Noble John L. Falconer 《American Institute of Chemical Engineers》2002,48(6):1155-1167
A transient permeation method presented here not only determines the adsorption and diffusion properties of the pores that are the transport pathways through zeolite membranes, but nondestructively estimates the effective thickness of the membrane. Transient responses of the permeate concentration to step changes in the feed were measured on two H-ZSM-5 tubular membranes and modeled assuming Maxwell-Stefan diffusion and Langmuir adsorption. The adsorption isotherms determined from these transient measurements at 298 K of N2 and CO2 were nearly identical to those measured by calorimetry on H-ZSM-5 powders. The CH4 isotherm at 298 K was similar to isotherms measured by calorimetry and gravimetric techniques on Na-ZSM-5 and silicalite powders. The similarity of the isotherms indicates that transport of these light gases occurs mainly through zeolite pores. The Maxwell-Stefan diffusion coefficients DMS depended on concentration and were higher for higher feed partial pressures. Average DMS values for the two membranes were 7.5, 5 and 1.5×10−10 m2/s for N2, CH4, and CO2, respectively; these are in the same range and order as diffusion coefficients measured in zeolite crystals. 相似文献
45.
Male rats maintained at 24 C and then shifted to 5 C for 5 days increased food intake and decreased in growth rate and food
conversion. No modification was observed in Δ6 desaturase activity, while Δ9 desaturase activity decreased after this period
of time. These results were confirmed by liver microsomal and mitochondrial fatty acid composition. The phospholipid composition
of liver microsomes was unaltered, whereas in mitochondria, phosphatidylcholine and sphingomyelin decreased and phosphatidylethanolamine
increased due to the cold environment. The influence of food intake and weight changes on fatty acid metabolism was studied
using (i) rats maintained at 5 C with restricted food intake to match the food intake of those kept at 24 C with food ad libitum
and (ii) rats maintained at 24 C whose food intake was also restricted so that their growth rate would be the same as that
of rats maintained at 5 C with food ad libitum, respectively. These results indicate that the negative metabolic balance state
of these cold conditions is not an active factor modifier of Δ6 desaturase activity, whereas it decreases Δ9 desaturase activity,
reflecting the lipogenic characteristics of the latter enzyme. 相似文献
46.
Lisbeth M Ottosen Ana T Lima Anne J Pedersen Alexandra B Ribeiro 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(4):553-559
The possibility of using fly ash from municipal solid waste incineration (MSWI) in, for example, concrete is considered. MSWI fly ash, however, has too high a concentration of heavy metals, which may cause leaching problems during use or problems with waste handling at the end of the lifetime of the concrete. The Cl content in MSWI fly ash is also too high and will cause corrosion problems in reinforced concrete. The possibility of removing some of the unwanted heavy metals (Cu and Pb) together with Cl from an MSWI fly ash suspended in water using an electrodialytic separation method was investigated. The removal of Pb and Cu was found to be highly pH dependent and the highest contents removed were 41 and 90%, respectively. The Cu concentration of the ash decreased from 2200 to 860 mg kg?1 but the Pb concentration increased from 8560 to 16 800 mg kg?1, showing that Pb is mainly found in the ash fraction that is least soluble. Hence electrodialytic treatment of the ash suspended in water is not a solution to improve the ash quality in terms of Pb. The water‐soluble Cl content per unit weight of the original ash was 12.4%. The removal of water‐soluble Cl was efficient and >98% of Cl was removed (calculated on the basis of mean initial and final concentrations). This result indicates that electrodialytic extraction may be a method that can be used for the removal of Cl from ash prior to its utilization in concrete. Copyright © 2006 Society of Chemical Industry 相似文献
47.
48.
The polymerization of α-methylstyrene (αMeSty) initiated by HI/I2 or HI in the presence of liquid sulfur dioxide has been investigated. The number-average molecular weight increased with
the monomer concentration for reactions initiated by the HI/I2 system. I2 also participates in the initiation process, increasing the number-average polymer chain at higher monomer concentration.
HI alone is also able to initiate the polymerization of αMeSty in the presence of SO2. With this initiator, transfer reaction can be minimized in systems containing low amount of SO2.
Received: 19 December 1996/Revised: 27 January 1997/Accepted 29 January 1997 相似文献
49.
In this work, the effect of the introduction of modified solid surfaces into polymer blends on the phase‐separation process was investigated. Glass fibers with surfaces having different chemistries were introduced into polystyrene–poly(methyl methacrylate) blends. The glass fibers used either had fully hydrated surfaces or had surfaces covered with a random copolymer, poly(styrene‐co‐methyl methacrylate). The copolymer was synthesized by free‐radical polymerization of styrene and methyl methacrylate in the presence of previously vinyl silane‐treated glass fibers. The copolymerization and grafting procedures were investigated by FTIR and thermal analysis. Blends containing the fibers were studied using FTIR microscopy and optical microscopy. FTIR microscopy results showed that the composition of the phases in the blends was shifted by using fibers with different surface chemistries. Fibers with grafted copolymers were capable of narrowing the immiscibility region in the phase diagram, while fully hydrated fibers were able to expand the gap. It was proposed that interfacial interactions regulated by a hydrophilic–hydrophobic type of forces were responsible for guiding the described phase‐separation process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1619–1627, 2003 相似文献
50.
Ana Paula Vieira Soares Manuel Farinha Portela Alain Kiennemann 《Catalysis Reviews》2005,47(1):125-174
This review deals with the important industrial reaction of formaldehyde manufacture by methanol oxidation over iron molybdate catalysts. Detailed reference is made to the used catalyst, preparation techniques (coprecipitation, sol-gel like, mechanical mixing, etc.) including unsupported and supported catalysts, promoters and characterization methods. The controversial active phase assignment (stoichiometric versus Mo rich iron molybdate) is discussed. The proposed reaction mechanisms and kinetic laws for the main and side reactions are examined. The catalyst deactivation processes are reviewed and the role of Mo excess on these processes is underlined. Finally conclusions and perspectives are presented. 相似文献