全文获取类型
收费全文 | 24100篇 |
免费 | 2231篇 |
国内免费 | 946篇 |
专业分类
电工技术 | 1184篇 |
综合类 | 1607篇 |
化学工业 | 4816篇 |
金属工艺 | 1028篇 |
机械仪表 | 1087篇 |
建筑科学 | 1418篇 |
矿业工程 | 436篇 |
能源动力 | 607篇 |
轻工业 | 3757篇 |
水利工程 | 510篇 |
石油天然气 | 732篇 |
武器工业 | 136篇 |
无线电 | 2033篇 |
一般工业技术 | 2694篇 |
冶金工业 | 838篇 |
原子能技术 | 204篇 |
自动化技术 | 4190篇 |
出版年
2024年 | 105篇 |
2023年 | 342篇 |
2022年 | 916篇 |
2021年 | 1115篇 |
2020年 | 878篇 |
2019年 | 712篇 |
2018年 | 799篇 |
2017年 | 888篇 |
2016年 | 808篇 |
2015年 | 1146篇 |
2014年 | 1490篇 |
2013年 | 1834篇 |
2012年 | 2106篇 |
2011年 | 2238篇 |
2010年 | 1908篇 |
2009年 | 1838篇 |
2008年 | 1663篇 |
2007年 | 1558篇 |
2006年 | 1236篇 |
2005年 | 906篇 |
2004年 | 604篇 |
2003年 | 449篇 |
2002年 | 364篇 |
2001年 | 250篇 |
2000年 | 192篇 |
1999年 | 156篇 |
1998年 | 141篇 |
1997年 | 117篇 |
1996年 | 84篇 |
1995年 | 68篇 |
1994年 | 55篇 |
1993年 | 42篇 |
1992年 | 37篇 |
1991年 | 26篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1966年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
以TDT、TMP、N-220、3010、为主要原料合成聚醚型聚氨酯预聚物,达到塑胶漆的性能要求。本文探讨了不同的合成条件对预聚物的影响。 相似文献
93.
94.
通过细乳液聚合方法制备自交联型有机硅乳液 总被引:3,自引:0,他引:3
苯乙烯与甲基丙烯酸-3-三甲氧基硅丙酯(M PS)经细乳液聚合,制得了稳定的自交联型的水分散涂料,用透射电子显微镜(TEM)、动态光散射仪(DLS)和红外光谱(IR)表征了乳胶粒的形态和结构。发现与传统乳液聚合相比,细乳液聚合法可显著提高乳液的稳定性,且M PS加入量的增加会导致乳液稳定性降低。 相似文献
95.
The electrochemical reduction of nitrate ion was studied by cyclic voltammetry on Pt(1 1 1) and [n(1 1 1) × (1 1 1)] stepped Pt surfaces, where n (=14, 10, 7, 6, 5, 4, 3, 2) is the number of terrace atoms, in 0.1 M HClO4 + 10 mM KNO3. The electrocatalytic nitrate reduction was found to hardly proceed on Pt(1 1 1) in the hydrogen adsorption region, while the electrocatalytic activity was improved with the increase in the step density. Inactivation was observed in the presence of adsorbed hydrogen or nitrate-derived reduced adsorbate, i.e. adsorbed NO, on (1 1 1) step sites. It was, therefore, concluded that the electrocatalytically active NO3− species does not adsorb on the (1 1 1) terraces but on the (1 1 1) monoatomic steps. The nitrate reduction current increased with the step density in a non-linear relationship. The overall current density at 0.21 V (RHE) corresponding to the peak potential of the main electrocatalytic nitrate reduction wave which was maximum at n = 2, abruptly increased with short terraces, i.e. n < 5, where the current wave of adsorbed hydrogen on the Pt stepped surface with comparatively narrow (1 1 1) terraces, denoted as Hnt, also appeared unmodified for n < 5 on voltammograms recorded in 0.1 M HClO4 in the absence of nitrate. 相似文献
96.
Jorge González-Domínguez Osni A. Marques María J. Martín Juan Touriño 《The Journal of supercomputing》2014,70(2):816-829
This paper examines four different strategies, each one with its own data distribution, for implementing the parallel conjugate gradient (CG) method and how they impact communication and overall performance. Firstly, typical 1D and 2D distributions of the matrix involved in CG computations are considered. Then, a new 2D version of the CG method with asymmetric workload, based on leaving some threads idle during part of the computation to reduce communication, is proposed. The four strategies are independent of sparse storage schemes and are implemented using Unified Parallel C (UPC), a Partitioned Global Address Space (PGAS) language. The strategies are evaluated on two different platforms through a set of matrices that exhibit distinct sparse patterns, demonstrating that our asymmetric proposal outperforms the others except for one matrix on one platform. 相似文献
97.
以Fe(NO3)3、煤矸石和NaOH为原料,采用沸腾回流法制得了一系列不同质量比的α-Fe2O3/煤矸石复合光催化剂。采用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)及紫外-可见漫反射光谱(UV-Vis DRS)等多种手段对产物做了表征。以五氯酚为目标降解物,考察了模拟太阳光照下样品的光催化效果。结果表明,将球形α-Fe2O3负载于改性煤矸石表面可有效提高其光催化活性,且α-Fe2O3/煤矸石复合光催化剂的性能与α-Fe2O3的含量有关,当α-Fe2O3与煤矸石的质量比为30∶100时,样品的光催化效果最佳,180 min内即可将五氯酚降解完全。此外,α-Fe2O3/煤矸石复合光催化剂还具有可重复使用的特点。 相似文献
98.
A series of pH‐sensitive and thermosensitive polymer networks were first obtained by copolymerization of telechelic poly(1,3‐dioxolane) (PDXL) with acrylic acid (AA), acrylamide (AM), and N‐isopropylacrylamide (NIPAM), respectively. The copolymerization of PDXL diacrylate (PDXLDA) with AA, AM, or NIPAM is expected to lead to polymer networks in which homopolymeric segments of the monomer are connected by polyacetal segments. As a combination of these two parts, these polymer networks can have some interesting physical properties. For example, the copolymer networks of poly(AA‐b‐DXL) showed pH sensitivity, and both the copolymer networks of poly(AM‐b‐DXL) and poly(NIPAM‐b‐DXL) showed temperature sensitivity. Moreover, because of the low ceiling temperature of polyDXL, the networks containing polyacetal segments (PDXL) can degrade by treatment with a trace of appropriate cationic initiator. The polymer networks prepared were characterized by Fourier transform infrared, differential scanning calorimetry, and swelling data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3002–3006, 2002; DOI 10.1002/app.2329 相似文献
99.
100.
Cristina López‐Dehesa José A. González‐Marcos Juan R. González‐Velasco 《应用聚合物科学杂志》2007,103(5):2843-2848
Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) membranes have been used to separate ethanol–water mixtures by pervaporation. This polyacetylene is known to present high affinity toward ethanol, showing high selectivity and ethanol permeation flux. The performance of this polymer in the separation of alcohol–water solutions has been evaluated over long periods (572 h) at a high temperature (75°C) to examine the deterioration of the transport properties in the separation of 50 wt % ethanol–water solutions. Although PTMSP membranes present good characteristics for the separation of gases and liquid mixtures, their organic selectivity decrease with the operating time because of the relaxation processes of the polymeric chains, which affect the free volume of the polymer, the deterioration being more evident for concentrated solutions. The effects of the operation temperature on the characteristic parameters of pervaporation have also been studied to establish how this variable affects the performance of PTMSP membranes. The selectivity increases slightly with the operation temperature, but the effect of the temperature on the separation factor decreases as membranes are degraded with the operation time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2843–2848, 2007 相似文献