全文获取类型
收费全文 | 14811篇 |
免费 | 1877篇 |
国内免费 | 803篇 |
专业分类
电工技术 | 103篇 |
技术理论 | 1篇 |
综合类 | 811篇 |
化学工业 | 7334篇 |
金属工艺 | 374篇 |
机械仪表 | 375篇 |
建筑科学 | 172篇 |
矿业工程 | 245篇 |
能源动力 | 167篇 |
轻工业 | 1982篇 |
水利工程 | 26篇 |
石油天然气 | 1491篇 |
武器工业 | 139篇 |
无线电 | 1077篇 |
一般工业技术 | 2263篇 |
冶金工业 | 183篇 |
原子能技术 | 177篇 |
自动化技术 | 571篇 |
出版年
2024年 | 69篇 |
2023年 | 377篇 |
2022年 | 420篇 |
2021年 | 855篇 |
2020年 | 631篇 |
2019年 | 607篇 |
2018年 | 517篇 |
2017年 | 507篇 |
2016年 | 602篇 |
2015年 | 585篇 |
2014年 | 879篇 |
2013年 | 1021篇 |
2012年 | 1051篇 |
2011年 | 1004篇 |
2010年 | 707篇 |
2009年 | 748篇 |
2008年 | 616篇 |
2007年 | 814篇 |
2006年 | 800篇 |
2005年 | 698篇 |
2004年 | 578篇 |
2003年 | 481篇 |
2002年 | 402篇 |
2001年 | 407篇 |
2000年 | 319篇 |
1999年 | 256篇 |
1998年 | 227篇 |
1997年 | 189篇 |
1996年 | 197篇 |
1995年 | 170篇 |
1994年 | 124篇 |
1993年 | 114篇 |
1992年 | 95篇 |
1991年 | 83篇 |
1990年 | 64篇 |
1989年 | 35篇 |
1988年 | 31篇 |
1987年 | 27篇 |
1986年 | 22篇 |
1985年 | 37篇 |
1984年 | 34篇 |
1983年 | 25篇 |
1982年 | 34篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 5篇 |
1959年 | 1篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
A novel unsaturated poly(ester‐amide) network (UPEAN) that contains isolated C? C double bonds, monomeric lactate sequences, rigid benzyl side‐groups, amide groups and crosslinking points has been designed and synthesized. The structure of the intermediate and UPEAN was verified with Fourier transform infrared spectroscopy. Pores in UPEAN generated in situ were examined with scanning electron microscopy. Differential scanning calorimetry analysis shows that UPEAN is amorphous and its glass transition temperature is around 34 °C. It is found that UPEAN exhibits thermosensitive shape‐recovery characteristics. The maximum percentage weight loss of UPEAN is 10 and 42% after immersing the samples in active sludge at ambient temperature for 146 days and in 0.1 mol L?1 phosphate‐buffer saline at 37 °C for 103 days, respectively, which suggests that UPEAN is degradable. Copyright © 2007 Society of Chemical Industry 相似文献
992.
993.
干壳莲子分级是实现莲子机械化剥壳的前道工序,依据干壳莲子的物理特性,干壳莲子分级宜采用分级杆筛。本文分别从干壳莲子分级要求、分级杆筛设计方案、分级杆筛及筛杆结构、分级杆筛制造技术和分级杆筛试验等方面对莲子分级杆筛进行了分析与设计。 相似文献
994.
乙二胺改性聚乳酸溶液的性质 总被引:1,自引:0,他引:1
乙二胺改性聚乳酸(EMPLA)是一种具有支化结构的新型生物材料。文中采用GPC-MALLS技术对其在四氢呋喃(THF)中的分子量、分子量分布、半径、支化及其这些量之间的相互关系进行了分析与研究,结果表明:乙二胺改性聚乳酸在四氢呋喃中的折光指数增量dn/dc值为0.052 mL/g,第二维利系数A2为3.905e-3 mol mL/g2,重均分子量-Mw为5.753e 4,重均均方根旋转半径Rw为4.5 nm,-Mw与Rw的关系式为:Rw=0.608×-Mw0.316,通过与线性聚乳酸(PDLLA)的比较,能够得到具有与PDLLA相同分子量的EMPLA有较小的均方根旋转半径的结论,并能够推出EMPLA在四氢呋喃溶液中的分子构象为球形。 相似文献
995.
Edyta Janik Marcin Niemcewicz Marcin Podogrocki Joanna Saluk-Bijak Michal Bijak 《International journal of molecular sciences》2021,22(11)
COVID-19 is a respiratory disease caused by newly discovered severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease at first was identified in the city of Wuhan, China in December 2019. Being a human infectious disease, it causes high fever, cough, breathing problems. In some cases it can be fatal, especially in people with comorbidities like heart or kidney problems and diabetes. The current COVID-19 treatment is based on symptomatic therapy, so finding an appropriate drug against COVID-19 remains an immediate and crucial target for the global scientific community. Two main processes are thought to be responsible for the COVID-19 pathogenesis. In the early stages of infection, disease is determined mainly by virus replication. In the later stages of infection, by an excessive immune/inflammatory response, leading to tissue damage. Therefore, the main treatment options are antiviral and immunomodulatory/anti-inflammatory agents. Many clinical trials have been conducted concerning the use of various drugs in COVID-19 therapy, and many are still ongoing. The majority of trials examine drug reposition (repurposing), which seems to be a good and effective option. Many drugs have been repurposed in COVID-19 therapy including remdesivir, favipiravir, tocilizumab and baricitinib. The aim of this review is to highlight (based on existing and accessible clinical evidence on ongoing trials) the current and available promising drugs for COVID-19 and outline their characteristics. 相似文献
996.
998.
K. Petritsch J. J. Dittmer E. A. Marseglia R. H. Friend A. Lux G. G. Rozenberg S. C. Moratti A. B. Holmes 《Solar Energy Materials & Solar Cells》2000,61(1)
We have fabricated organic donor/acceptor solar cells with three different architectures using soluble derivatives (dyes) of the molecular semiconductors phthalocyanine as electron donor (D), i.e. hole transport material and perylene as electron acceptor (A), i.e. electron transport material. These architectures comprise a blend and a double layer structure as well as the only recently reported laminated-device structure. The organic semiconducting films were deposited at room temperature via spin coating from solution. Current–voltage (I/V) characteristics and external quantum efficiency spectra will be discussed. The measured quantum efficiencies reach values between 0.3% and 1.1% with a photoresponse covering the entire spectrum of visible light. Our results show that together with insoluble small molecules (pigments) and conjugated polymers, dye molecules represent a new class of organic semiconducting materials that can be used to manufacture D/A solar cells. 相似文献
999.
Currentlytheincidenceandlethalityofthrombusillnessareveryhigh ,anditseriouslythreatenspublichealth .Thrombolysisisoneoftherelativelyeffectivemethodstotreatthedis ease .Single chainurokinase typeplasminogenactivator (scu PA 3 2k )oflowmolecularweight(3 2kD)wasdi… 相似文献
1000.