全文获取类型
收费全文 | 30183篇 |
免费 | 1323篇 |
国内免费 | 58篇 |
专业分类
电工技术 | 312篇 |
综合类 | 30篇 |
化学工业 | 4926篇 |
金属工艺 | 884篇 |
机械仪表 | 1298篇 |
建筑科学 | 429篇 |
矿业工程 | 6篇 |
能源动力 | 864篇 |
轻工业 | 1861篇 |
水利工程 | 92篇 |
石油天然气 | 19篇 |
武器工业 | 1篇 |
无线电 | 3663篇 |
一般工业技术 | 4637篇 |
冶金工业 | 9879篇 |
原子能技术 | 292篇 |
自动化技术 | 2371篇 |
出版年
2024年 | 22篇 |
2023年 | 275篇 |
2022年 | 399篇 |
2021年 | 683篇 |
2020年 | 473篇 |
2019年 | 497篇 |
2018年 | 699篇 |
2017年 | 661篇 |
2016年 | 769篇 |
2015年 | 602篇 |
2014年 | 942篇 |
2013年 | 1392篇 |
2012年 | 1459篇 |
2011年 | 1791篇 |
2010年 | 1302篇 |
2009年 | 1336篇 |
2008年 | 1215篇 |
2007年 | 945篇 |
2006年 | 820篇 |
2005年 | 715篇 |
2004年 | 649篇 |
2003年 | 598篇 |
2002年 | 593篇 |
2001年 | 520篇 |
2000年 | 443篇 |
1999年 | 700篇 |
1998年 | 3380篇 |
1997年 | 1897篇 |
1996年 | 1339篇 |
1995年 | 803篇 |
1994年 | 588篇 |
1993年 | 675篇 |
1992年 | 173篇 |
1991年 | 202篇 |
1990年 | 173篇 |
1989年 | 174篇 |
1988年 | 167篇 |
1987年 | 154篇 |
1986年 | 146篇 |
1985年 | 108篇 |
1984年 | 37篇 |
1983年 | 37篇 |
1982年 | 66篇 |
1981年 | 63篇 |
1980年 | 105篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 203篇 |
1976年 | 462篇 |
1975年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
MZ Kounnas EB Loukinova S Stefansson JA Harmony BH Brewer DK Strickland WS Argraves 《Canadian Metallurgical Quarterly》1995,270(22):13070-13075
Glycoprotein 330 (gp330) is a member of a family of endocytic receptors related to the low density lipoprotein receptor. gp330 has previously been shown to bind a number of ligands in common with its family member, the low density lipoprotein receptor-related protein (LRP). To identify ligands specific for gp330 and relevant to its localization on epithelia such as in the mammary gland, gp330-Sepharose affinity chromatography was performed. As a result, a 70-kDa protein was selected from human milk and identified by protein sequencing to be apolipoprotein J/clusterin (apoJ). Solid-phase binding assays confirmed that gp330 bound to apoJ with high affinity (Kd = 14.2 nM). Similarly, gp330 bound to apoJ transferred to nitrocellulose after SDS-polyacrylamide gel electrophoresis. LRP, however, showed no binding to apoJ in either type of assay. The binding of gp330 to apoJ could be competitively inhibited with excess apoJ as well as with the gp330 ligands apolipoprotein E, lipoprotein lipase, and the receptor-associated protein, a 39-kDa protein that acts to antagonize binding of all known ligands for gp330 and LRP. Several cultured cell lines that express gp330 and ones that do not express the receptor were examined for their ability to bind and internalize 125I-apoJ. Only cells that expressed gp330 endocytosed and degraded radiolabeled apoJ. Furthermore, F9 cells treated with retinoic acid and dibutyryl cyclic AMP to increase expression levels of gp330 displayed an increased capacity to internalize and degrade apoJ. Cellular internalization and degradation of radiolabeled apoJ could be inhibited with unlabeled apoJ, receptor-associated protein, and gp330 antibodies. The results indicate that gp330 but not LRP can bind to apoJ in vitro and that gp330 expressed by cells can mediate apoJ endocytosis leading to lysosomal degradation. 相似文献
52.
Young-Soo Lee Do-Hyeon Park Hee-Taik Kim Kyong-Ok Yoo 《Korean Journal of Chemical Engineering》1995,12(1):23-28
Much SO2, another perilous air pollutant, was emitted during the oxidative regeneration of sulfided sorbent by H2S. In order to prevent emission of SO2, we carried out oxidative regeneration with the physical mixture of CaO and sulfided sorbent and investigated the effect
of regeneration temperature and oxygen concentration on the reactivity of CaO with S02. The effluent gases were analyzed by G.C. and the properties of sorbent were characterized by XRD. SEM, TG/DTA and EPMA.
Deterioration of reactivity of CaO with S02 resulted in increment of emission of SO12 due to the structural changes of CaO above 750°C and that at 850°C was more severe. Furthermore EPMA and XRD analysis revealed
that product layer diffusion through the solid product, CaSO4, was the rate limiting step for CaO sulfidation. The reaction of CaO w:.th SO2 was first order approximately and that was accelerated by high O2 concentration. 相似文献
53.
Overview of ship-design expert systems 总被引:1,自引:0,他引:1
Expert systems constitute a branch of artificial intelligence, and their unique characteristics enable computer systems to perform at the level of a human expert by the use of algorithms that can capture domain-specific knowledge. Through an extensive survey of research about ship-design expert systems, we conclude that although development and implementation of expert systems for ship design offer substantial barriers, the shipbuilding industry needs them nonetheless. We examine the major reasons that use of expert systems in this industry has lagged behind. These include the problems of integration with existing computer-aided design systems, problems of knowledge representation and sizable development costs. We discuss in detail some key factors that can lead to the solution of these problems. 相似文献
54.
55.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
56.
57.
58.
T.J. ChungJ.H. Park C.K. Choi D.-Y. Yoon 《International Journal of Heat and Mass Transfer》2002,45(14):3061-3064
The onset of convective instability in a fluid-saturated porous layer between the two horizontal plates heated isothermally from below has been analyzed theoretically by using propagation theory. In the analysis the thermal dispersion coefficient is assumed to be proportional to the streamwise velocity. The results show that both inertia and thermal dispersion stabilize the system. 相似文献
59.
Propolis collected by bees has many components that possess antifungal, anticancer and antioxidant properties. Cured ground pork meat was treated separately with 0.4% w/w ethanol‐extracted propolis (EEP 0.4%), 0.6% w/w water‐extracted propolis (WEP 0.6%), 0.8% w/w dried residue of ethanol‐extracted propolis (DREEP 0.8%) and 0.1% w/w potassium sorbate (PS 0.1%) and made into sausages. Thiobarbituric acid‐reactive substances (TBARS) were measured in the sausages to assess the effects of storage at 5, 10 and 20 °C after 0, 2 and 4 weeks. After 4 weeks of storage at 5 °C the sausages treated with EEP 0.4%, DREEP 0.8%, WEP 0.6% and PS 0.1% yielded TBARS values which were 50, 59, 35 and 91% respectively of the control value. There was an increase of 0.33 mg MDA kg?1, the lowest of all treatments, in TBARS for the 0.4% w/w EEP‐treated sausages. The curing process will control microbiological spoilage, as will potassium sorbate. © 2002 Society of Chemical Industry 相似文献
60.
Jeong-Hyun Park 《Communications Magazine, IEEE》2002,40(4):38-49
With the advent of IP technologies and the tremendous growth in data traffic, the wireless industry is evolving its core networks toward IP technology. Enabling wireless Internet access is one of the upcoming challenges for mobile radio network operators. The General Packet Radio Service is the packet-switched extension of GSM and was developed to facilitate access to IP-based services better than existing circuit-switched services provided by GSM. We illustrate how a visited mobile subscriber on a GPRS/UMTS network can access his/her home network via the gateway GPRS support node (GGSN). We also propose some implementation ideas on wireless Internet access for a remote mobile subscriber based on a GPRS/UMTS network 相似文献