全文获取类型
收费全文 | 91112篇 |
免费 | 7653篇 |
国内免费 | 4084篇 |
学科分类
工业技术 | 102849篇 |
出版年
2024年 | 370篇 |
2023年 | 1371篇 |
2022年 | 2575篇 |
2021年 | 3570篇 |
2020年 | 2503篇 |
2019年 | 2105篇 |
2018年 | 2359篇 |
2017年 | 2801篇 |
2016年 | 2455篇 |
2015年 | 3396篇 |
2014年 | 4445篇 |
2013年 | 5667篇 |
2012年 | 6040篇 |
2011年 | 6752篇 |
2010年 | 5858篇 |
2009年 | 5650篇 |
2008年 | 5585篇 |
2007年 | 5347篇 |
2006年 | 5124篇 |
2005年 | 4178篇 |
2004年 | 2845篇 |
2003年 | 2352篇 |
2002年 | 2370篇 |
2001年 | 2025篇 |
2000年 | 1912篇 |
1999年 | 1951篇 |
1998年 | 1963篇 |
1997年 | 1657篇 |
1996年 | 1463篇 |
1995年 | 1228篇 |
1994年 | 963篇 |
1993年 | 777篇 |
1992年 | 613篇 |
1991年 | 480篇 |
1990年 | 393篇 |
1989年 | 307篇 |
1988年 | 261篇 |
1987年 | 190篇 |
1986年 | 157篇 |
1985年 | 148篇 |
1984年 | 100篇 |
1983年 | 75篇 |
1982年 | 70篇 |
1981年 | 60篇 |
1980年 | 53篇 |
1979年 | 36篇 |
1978年 | 32篇 |
1977年 | 35篇 |
1976年 | 63篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
利用挤压铸造制备氧化铝/锌合金复合材料,在扫描电镜(SEM)上观察复合材料的界面。结果表明,在复合材料中纤维与基体间存在致密界面层,合金元素通过适当的化学反应可改善纤维与基体间的结合;在凝固过程中,纤维/基体界面上的硅在共晶体的共生生长过程中起了领先相作用,导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变两者组成。 相似文献
82.
ATM网络的可用比特率业务 总被引:2,自引:0,他引:2
本文介绍了可用比特率业务的业务特点,速率控制机制以及该业务存在的问题。 相似文献
83.
84.
We have studied lamp configuration design for rapid thermal processing (RTP) systems. We considered a configuration consisting of four concentric circular lamp zones, three of them above the wafer and one circumventing the wafer. We propose a method to determine the geometric parameters, the width, height and radius, of the lamp zones so that the configuration designed has the capacity to achieve a uniform temperature on the wafer. The method is based on a necessary and sufficient condition for uniform temperature tracking and analytic expressions of the view factors. A design example is given in which a least square open-loop control law yields good temperature uniformity 相似文献
85.
Amines such as dopamine, norepinephrine and epinephrine were analysed in the brain regions of O.mossambicus exposed to quinalphos, phenthoate and their combination for 96 hr. The three types of treatments significantly (P < 0.05) altered the amines level at various intervals in the brain regions. 相似文献
86.
高性能各向异性Sm2Fe17Nx磁粉的制备 总被引:5,自引:0,他引:5
本文研究了高性能各向异性Sm2Fe17Nx磁粉的制备工艺路线与工艺参数。优化了制备与工艺参数。已制备出磁性能达到:Br=1.39T,Hci=850KA/m和(BH)m=236KJ/m^3的各向异性Sm2Fe17N2.88磁粉,该磁粉的各向异性场HA达到20T。 相似文献
87.
Antigen receptor genes are assembled by site-specific DNA rearrangement. The recombination activator genes RAG-1 and RAG-2 are essential for this process, termed V(D)J rearrangement. The activity and stability of the RAG-2 protein have now been shown to be regulated by phosphorylation. In fibroblasts RAG-2 was phosphorylated predominantly at two serine residues, one of which affected RAG-2 activity in vivo. The threonine at residue 490 was phosphorylated by p34cdc2 kinase in vitro; phosphorylation at this site in vivo was associated with rapid degradation of RAG-2. Instability was transferred to chimeric proteins by a 90-residue portion of RAG-2. Mutation of the p34cdc2 phosphorylation site of the tumor suppressor protein p53 conferred a similar phenotype, suggesting that this association between phosphorylation and degradation is a general mechanism. 相似文献
88.
89.
A technique for SiO2 formation by liquid-phase deposition (LPD) at nearly room temperature for low-temperature processed (LTP) polysilicon thin-film transistor (poly-Si TFT) was developed. LPD SiO2 film with a lower P-etch rate shows a dense structure. LPD SiO2 also exhibits good electrical characteristics. LTP poly-Si thin-film transistors (TFTs) with LPD SiO 2 as the gate insulator have been fabricated and investigated. Their characteristics indicate performance adequate for their use as pixel transistors in liquid crystal displays (LCDs) 相似文献
90.
BH Shieh MY Zhu JK Lee IM Kelly F Bahiraei 《Canadian Metallurgical Quarterly》1997,94(23):12682-12687
Visual transduction in Drosophila is a G protein-coupled phospholipase C-mediated process that leads to depolarization via activation of the transient receptor potential (TRP) calcium channel. Inactivation-no-afterpotential D (INAD) is an adaptor protein containing PDZ domains known to interact with TRP. Immunoprecipitation studies indicate that INAD also binds to eye-specific protein kinase C and the phospholipase C, no-receptor-potential A (NORPA). By overlay assay and site-directed mutagenesis we have defined the essential elements of the NORPA-INAD association and identified three critical residues in the C-terminal tail of NORPA that are required for the interaction. These residues, Phe-Cys-Ala, constitute a novel binding motif distinct from the sequences recognized by the PDZ domain in INAD. To evaluate the functional significance of the INAD-NORPA association in vivo, we generated transgenic flies expressing a modified NORPA, NORPAC1094S, that lacks the INAD interaction. The transgenic animals display a unique electroretinogram phenotype characterized by slow activation and prolonged deactivation. Double mutant analysis suggests a possible inaccessibility of eye-specific protein kinase C to NORPAC1094S, undermining the observed defective deactivation, and that delayed activation may similarly result from NORPAC1094S being unable to localize in close proximity to the TRP channel. We conclude that INAD acts as a scaffold protein that facilitates NORPA-TRP interactions required for gating of the TRP channel in photoreceptor cells. 相似文献