全文获取类型
收费全文 | 35405篇 |
免费 | 2519篇 |
国内免费 | 56篇 |
专业分类
电工技术 | 238篇 |
综合类 | 122篇 |
化学工业 | 8215篇 |
金属工艺 | 679篇 |
机械仪表 | 742篇 |
建筑科学 | 1121篇 |
矿业工程 | 85篇 |
能源动力 | 966篇 |
轻工业 | 7240篇 |
水利工程 | 360篇 |
石油天然气 | 238篇 |
武器工业 | 2篇 |
无线电 | 1517篇 |
一般工业技术 | 5483篇 |
冶金工业 | 5954篇 |
原子能技术 | 154篇 |
自动化技术 | 4864篇 |
出版年
2024年 | 44篇 |
2023年 | 321篇 |
2022年 | 360篇 |
2021年 | 1284篇 |
2020年 | 910篇 |
2019年 | 975篇 |
2018年 | 1456篇 |
2017年 | 1437篇 |
2016年 | 1517篇 |
2015年 | 1116篇 |
2014年 | 1500篇 |
2013年 | 2924篇 |
2012年 | 2401篇 |
2011年 | 2363篇 |
2010年 | 1866篇 |
2009年 | 1694篇 |
2008年 | 1599篇 |
2007年 | 1405篇 |
2006年 | 1044篇 |
2005年 | 861篇 |
2004年 | 777篇 |
2003年 | 774篇 |
2002年 | 601篇 |
2001年 | 491篇 |
2000年 | 408篇 |
1999年 | 452篇 |
1998年 | 2140篇 |
1997年 | 1385篇 |
1996年 | 857篇 |
1995年 | 486篇 |
1994年 | 392篇 |
1993年 | 378篇 |
1992年 | 142篇 |
1991年 | 105篇 |
1990年 | 83篇 |
1989年 | 92篇 |
1988年 | 110篇 |
1987年 | 103篇 |
1986年 | 76篇 |
1985年 | 94篇 |
1984年 | 81篇 |
1983年 | 53篇 |
1982年 | 50篇 |
1981年 | 72篇 |
1980年 | 77篇 |
1978年 | 38篇 |
1977年 | 116篇 |
1976年 | 227篇 |
1975年 | 38篇 |
1973年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
41.
D.R. Santos‐Peñate C.M. Campos‐Rodríguez J.A. Moreno‐Pérez 《International Transactions in Operational Research》2019,26(1):340-363
The ‐centroid problem or leader–follower problem is generalized considering different customer choice rules where a customer may use facilities belonging to different firms, if the difference in travel distance (or time) is small enough. Assuming essential goods, some particular customer choice rules are analyzed. Linear programming formulations for the generalized ‐medianoid and ‐centroid problems are presented and an exact solution approach is applied. Some computational examples are included. 相似文献
42.
Myriam Gonzlez María Ovejero-Snchez Alba Vicente-Blzquez Raquel lvarez Ana B. Herrero Manuel Medarde Rogelio Gonzlez-Sarmiento Rafael Pelez 《International journal of molecular sciences》2021,22(4)
Pan-Gyn cancers entail 1 in 5 cancer cases worldwide, breast cancer being the most commonly diagnosed and responsible for most cancer deaths in women. The high incidence and mortality of these malignancies, together with the handicaps of taxanes—first-line treatments—turn the development of alternative therapeutics into an urgency. Taxanes exhibit low water solubility that require formulations that involve side effects. These drugs are often associated with dose-limiting toxicities and with the appearance of multi-drug resistance (MDR). Here, we propose targeting tubulin with compounds directed to the colchicine site, as their smaller size offer pharmacokinetic advantages and make them less prone to MDR efflux. We have prepared 52 new Microtubule Destabilizing Sulfonamides (MDS) that mostly avoid MDR-mediated resistance and with improved aqueous solubility. The most potent compounds, N-methyl-N-(3,4,5-trimethoxyphenyl-4-methylaminobenzenesulfonamide 38, N-methyl-N-(3,4,5-trimethoxyphenyl-4-methoxy-3-aminobenzenesulfonamide 42, and N-benzyl-N-(3,4,5-trimethoxyphenyl-4-methoxy-3-aminobenzenesulfonamide 45 show nanomolar antiproliferative potencies against ovarian, breast, and cervix carcinoma cells, similar or even better than paclitaxel. Compounds behave as tubulin-binding agents, causing an evident disruption of the microtubule network, in vitro Tubulin Polymerization Inhibition (TPI), and mitotic catastrophe followed by apoptosis. Our results suggest that these novel MDS may be promising alternatives to taxane-based chemotherapy in chemoresistant Pan-Gyn cancers. 相似文献
43.
Lorena Rodríguez-López Myriam Rincón-Fontán Xanel Vecino Ana B. Moldes Jose M. Cruz 《Journal of surfactants and detergents》2020,23(1):79-90
Over the last few years, the global biosurfactant market has raised due to the increasing awareness among consumers, for the use of biological or bio-based products. Because of their composition, it can be speculated that these are more biocompatible and more biodegradable than their chemical homologous. However, at the moment, no studies exist in the literature about the biodegradability of biosurfactants. In this work, a biosurfactant contained in a crude extract, obtained from a corn wet-milling industry stream that ferments spontaneously in the presence of lactic acid bacteria, was subjected to a biodegradation study, without addition of external microbial biomass, under different conditions of temperature (5–45 °C), biodegradation time (15–55 days), and pH (5–7). For that, a Box–Behnken factorial design was applied, which allowed to predict the percentage of biodegradation for the biosurfactant contained in the crude extract, between the range of the independent variables selected in the study, obtaining biodegradation values between 3 and 80%. The percentage of biodegradation for the biosurfactant was calculated based on the increase in the surface tension of samples of the crude extract. Furthermore, it was also possible to predict the variation in t1/2 for the biosurfactant (time to achieve the 50% of biodegradation) under different conditions. 相似文献
44.
Andrés Aguirre Matías Cabruja Rodolfo Cabrera Florencia Eberhardt Salvador Peirú Hugo G. Menzella Rodolfo M. Rasia 《Journal of the American Oil Chemists' Society》2015,92(1):47-53
Steryl glucosides (SG) are common contaminants in biodiesel that form precipitates, which form and cause problems due to fouling during transport and storage. Therefore, their quantification is necessary to assess the quality of this fuel. The methods currently available for SG analysis require expensive instrumentation, need a previous concentration step by solid‐phase extraction (SPE) or are of limited use for the quantitative assessment. We developed an enzymatic method for SG quantification in biodiesel samples based on the hydrolysis of the glucoside catalyzed by a broadly specific beta glucosidase and the subsequent determination of the glucose released by the reaction. The method is non‐expensive, sensitive and was adapted to 96‐well format fluorescence plate reader, making it useful for the parallel assay of multiple samples. The enzymatic assay presented here represent a valuable tool for both quality control and the development of improved biodiesel production and purification procedures. 相似文献
45.
Bican Osman Bayça Salih Uğur Kuleyin Hamdi Gümrük Recep 《Metal Science and Heat Treatment》2021,63(3-4):156-162
Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied... 相似文献
46.
D. Solís-Cortés E. Navarrete-Astorga J.L. Costa-Krämer J. Salguero-Fernandez R. Schrebler D. Leinen E.A. Dalchiele J.R. Ramos-Barrado F. Martín 《Ceramics International》2019,45(5):5577-5587
C-axis textured thin films of gallium-doped indium zinc oxide (GIZO) with a 2% ratio of Ga/Zn, were obtained via RF-magnetron sputtering with high transparency and electrical conductivity. A Box-Behnken response surface design was used to evaluate the effects of the deposition parameters (In2O3 target power, deposition time, and substrate temperature) on the chemical composition, optical, electrical, and structural properties of the GIZO films. The optical constants and the electrical properties were obtained using optical models. The GIZO stoichiometry, and therefore the In/Zn atomic ratio, affected the crystallinity, crystalline parameters, band gap, and charge carrier mobility of the GIZO films. The charge carrier density was related to the change in the crystalline parameters of the hexagonal structure and the In/Zn atomic ratio. The best electrical conductivity values (1.75?×?103 Ω?1 cm?1) were obtained for GIZO films with In/Zn ratio ≥?1. Several figures of merit (FOM) defined for the visible and solar regions were comparatively used to select the optimal In/Zn atomic ratio that provided the best balance between the conductivity and the transparency. The optimal In/Zn ratio was in a range of 0.85–0.90 for the GIZO films. 相似文献
47.
48.
49.
50.