全文获取类型
收费全文 | 80351篇 |
免费 | 6706篇 |
国内免费 | 3096篇 |
专业分类
电工技术 | 4205篇 |
技术理论 | 4篇 |
综合类 | 4334篇 |
化学工业 | 14282篇 |
金属工艺 | 4213篇 |
机械仪表 | 5237篇 |
建筑科学 | 4923篇 |
矿业工程 | 1295篇 |
能源动力 | 2555篇 |
轻工业 | 6173篇 |
水利工程 | 1275篇 |
石油天然气 | 2610篇 |
武器工业 | 484篇 |
无线电 | 11131篇 |
一般工业技术 | 12125篇 |
冶金工业 | 3875篇 |
原子能技术 | 1046篇 |
自动化技术 | 10386篇 |
出版年
2024年 | 198篇 |
2023年 | 1071篇 |
2022年 | 1842篇 |
2021年 | 2976篇 |
2020年 | 2133篇 |
2019年 | 1944篇 |
2018年 | 2213篇 |
2017年 | 2408篇 |
2016年 | 2534篇 |
2015年 | 3008篇 |
2014年 | 3867篇 |
2013年 | 4960篇 |
2012年 | 5293篇 |
2011年 | 6016篇 |
2010年 | 5136篇 |
2009年 | 4836篇 |
2008年 | 4749篇 |
2007年 | 4233篇 |
2006年 | 4075篇 |
2005年 | 3511篇 |
2004年 | 2742篇 |
2003年 | 2592篇 |
2002年 | 2877篇 |
2001年 | 2406篇 |
2000年 | 1962篇 |
1999年 | 1737篇 |
1998年 | 1758篇 |
1997年 | 1303篇 |
1996年 | 1195篇 |
1995年 | 949篇 |
1994年 | 755篇 |
1993年 | 593篇 |
1992年 | 436篇 |
1991年 | 360篇 |
1990年 | 271篇 |
1989年 | 241篇 |
1988年 | 207篇 |
1987年 | 142篇 |
1986年 | 110篇 |
1985年 | 86篇 |
1984年 | 67篇 |
1983年 | 45篇 |
1982年 | 53篇 |
1981年 | 47篇 |
1980年 | 47篇 |
1979年 | 20篇 |
1977年 | 23篇 |
1976年 | 41篇 |
1975年 | 25篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
851.
852.
T. J. Shin H. K. Park S. W. Lee B. Lee W. Oh J.‐S. Kim S. Baek Y.‐T. Hwang H.‐C. Kim M. Ree 《Polymer Engineering and Science》2003,43(6):1232-1240
A series of aromatic polyimides composed of well‐defined conjugation units were synthesized form 5,5′‐bis(4‐aminophenyl)‐2,2′‐bifuryl (PFDA) and 2,2′‐bis(furyl) benzidine (FurylBZ) with various dianhydrides. The synthesized polyimides emit blue to green light with a quantum yield of 7.3–14.9%, depending on the polymer backbone. In particular, PFDA‐based polymers exhibit extremely narrow photo‐luminescence. The structure, thermal stability, refractive index and dielectric properties of the polymer films were also determined. 相似文献
853.
聚苯胺/涤纶导电织物再掺杂及洗涤性能的研究 总被引:6,自引:0,他引:6
采用现场吸附聚合法制备了聚苯胺 /涤纶导电织物 ,采用不同种类的酸对其进行再掺杂 ,研究了酸的种类对织物导电性能的影响 ,并对导电织物进行了洗涤实验及洗涤牢度实验。结果表明 :无机酸对导电织物的掺杂效果优于大多数有机酸。导电涤纶织物的导电性能受洗涤液酸碱度的影响 ,其中碱性洗涤液使导电性能降低 2个数量级 ,酸性洗涤液使导电性能下降 1个数量级 ,而且聚苯胺在涤纶织物表面具有良好的附着性 相似文献
854.
用8-AG(8-氮杂鸟嘌呤)驯化的HRP-MCAb(抗辣根过氧化物酶单克隆抗体)杂交瘤细胞HAT(次黄嘌呤氨基喋呤胸苷)敏感株与人IgG免疫的BALB/c小鼠脾细胞进行二次融合,获得5株能稳定分泌抗人IgG-抗HRP的BsMcAb(双特异性单克隆抗体)杂交-杂交癌细胞,用其混合腹水经HRP亲和层析纯化的BsMcAb制备BsMcAbPAP(双特异性单抗过氧化物酶-抗过氧化物酶复合物)试剂代替丙肝诊断试剂盒中酶标二抗,比较结果初步表明两者差异无显著意义,将为IgG的检测提供有用试剂。 相似文献
855.
856.
857.
塑料注射成型模具的排气方式和排气槽结构直接影响塑料制品质量。介绍了塑料注射成型模具的排气方式、排气槽设计经验以及切实可行的排气方案和排气槽结构。 相似文献
858.
859.
High surface area carbon-supported platinum-based catalysts, Pt/C, PtWO
x
/C, PtRu/C and PtRuWO
x
/C, were prepared via a chemical reduction route using single metal precursor salts. The catalyst particles were found to
be in the nanoscale range, and the addition of Ru clearly decreased the particle size. The Ru was found to be partially incorporated
into the face centered cubic lattice of Pt and to form a single Ru catalyst component. X-ray diffraction and X-ray photon
spectroscopy did not provide evidence for electronic interactions between WO
x
and Pt as well as WO
x
and Ru. However, the addition of tungsten to the PtRuWO
x
/C catalyst resulted in a high degree of catalyst particle agglomeration. Both Ru containing catalysts showed significantly
higher activities for the CH3OH oxidation reaction in terms of Pt + Ru mass as well as electroactive Pt + Ru surface area than the Pt/C and PtWO
x
/C catalysts. The addition of tungsten appeared to mainly result in some ‘physical’ modification of the catalytically active
Pt and Ru surface components such as differences in electroactive surface area rather than promotion of the CH3OH oxidation reaction via a true catalytic mechanism. 相似文献
860.
The farnesoid X receptor (FXR, NR1H4) has been recognized as an attractive therapeutic target because it is a nuclear hormone
receptor that controls the expression level of cholesterol-7α-hydroxylase, which in turn regulates bile acid production and
cholesterol excretion. To compare receptor activity between each domain and the full-length protein, human FXR cDNA was cloned
from a human liver cDNA library. Three human FXR cDNA, designated FXR20, FXR33, and FXR53 cDNA, were subcloned and ligated into a pET28a expression vector. Each protein was expressed in Escherichia coli (BL21) and purified by nickel-nitrilotriacetic acid column chromatography. Approximately 5 mg of FXR33 (1–182 amino acids deleted from FXR, 37 kDa) and 2 mg of FXR53 (the full-length protein of FXR, 59 kDa) was purified from 1 L of Luria-Bertani culture, achieving at least 90% purity. The
coactivator recruitment assay for FXR activation was carried out with the three variants of the FXR protein by using dissociation-enhanced
lanthanide fluoroimmunoassay-europium-N1-labeled anti-His antibody. From an optimized assay, a saturated hyperbolic fluorescence signal curve was produced when 250
nM of FXR33 and 100 nM of steroid receptor coactivator-1 peptide, a coactivator of FXR consisting of 26 amino acids, were used with a
concentration dependence on chenodeoxycholic acid (from 0 to 200 μM). The ligand-binding domain of FXR (FXR33) was the most suitable protein for studying the activation of FXR with a fluorescence-based assay, because it showed better
structural stability than either the full length of FXR (FXR53) or the DNA-binding domain of FXR (FXR20). 相似文献