全文获取类型
收费全文 | 302932篇 |
免费 | 16614篇 |
国内免费 | 8869篇 |
学科分类
工业技术 | 328415篇 |
出版年
2024年 | 933篇 |
2023年 | 3479篇 |
2022年 | 6257篇 |
2021年 | 8551篇 |
2020年 | 6278篇 |
2019年 | 5637篇 |
2018年 | 6445篇 |
2017年 | 7210篇 |
2016年 | 6762篇 |
2015年 | 8122篇 |
2014年 | 10865篇 |
2013年 | 16582篇 |
2012年 | 14560篇 |
2011年 | 17371篇 |
2010年 | 14436篇 |
2009年 | 14869篇 |
2008年 | 14443篇 |
2007年 | 14175篇 |
2006年 | 14264篇 |
2005年 | 12700篇 |
2004年 | 9512篇 |
2003年 | 8608篇 |
2002年 | 7757篇 |
2001年 | 7521篇 |
2000年 | 7441篇 |
1999年 | 8570篇 |
1998年 | 14481篇 |
1997年 | 10318篇 |
1996年 | 8522篇 |
1995年 | 6366篇 |
1994年 | 5436篇 |
1993年 | 4827篇 |
1992年 | 3263篇 |
1991年 | 2801篇 |
1990年 | 2465篇 |
1989年 | 2136篇 |
1988年 | 1808篇 |
1987年 | 1321篇 |
1986年 | 1261篇 |
1985年 | 1222篇 |
1984年 | 1007篇 |
1983年 | 881篇 |
1982年 | 847篇 |
1981年 | 816篇 |
1980年 | 688篇 |
1979年 | 562篇 |
1978年 | 469篇 |
1977年 | 586篇 |
1976年 | 1027篇 |
1975年 | 330篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
报导一种模糊逻辑控制系统的建模与优化方法。以此方法设计的模糊逻辑控制器,用于双波长稳频CO2激光器的控制得到令人满意的结果。 相似文献
102.
Storage performance-metrics and benchmarks 总被引:2,自引:0,他引:2
Chen P.M. Patterson D.A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1993,81(8):1151-1165
The metrics and benchmarks used in storage performance evaluation are discussed. The technology trends taking place in storage systems, such as disk and tape evolution, disk arrays, and solid-state disks, are highlighted. The current popular I/O benchmarks are then described, reviewed, and run on three systems: a DECstation 5000/200 running the Sprite Operating System, a SPARCstation 1+ running SunOS, and an HP Series 700 (Model 730) running HP-UX. Two approaches to storage benchmarks-LADDIS and a self-scaling benchmark with predicted performance-are also described 相似文献
103.
104.
The Frizzled genes encode receptors for WNTs, secreted glycoproteins implicated in development as well as in carcinogenesis. In this paper, we report molecular cloning of Hfz6, the human homologue of Mfz6. Nucleotide sequence analysis showed that the Hfz6 gene encodes the 706 amino-acid protein with seven transmembrane domains, a cystein-rich domain in the N-terminal extracellular region, two N-linked glycosylation sites, and two cystein residues in the second and third extracellular loops. Hfz6 mRNA 4.4-kb in size was detected in various normal adult and fetal tissues, and a larger amount of Hfz6 mRNA was detected in both fetal lung and fetal kidney. The Hfz6 gene has been mapped to human chromosome 8q22.3-q23.1. In conclusion, we have cloned Hfz6, which encodes a seven-transmembrane receptor with the cystein-rich domain in the N-terminal extracellular region, but without the Ser/Thr-X-Val motif in the C-terminus. 相似文献
105.
In this study, the effect and side-effect of epidural injection with lappaconitine compound for post-operative analgesia was observed. One hundred and twenty patients were randomly divided into 4 groups. Lappaconitine compound (LB) consisted of 12 mg of lappaconitine and 22.5 mg of bupivacaine, was given to group A (the group of observation), and lappaconitine 12 mg, bupivacaine 22.5 mg and morphine 2 mg to group B, C and D respectively for control. All were given by epidural injection with single blind method during post-operative pain of incision operation. Result showed that the initiating of analgesia was quicker in group A and C than that in group B and D, and the efficacy was group D > A > C > B. There was significant difference between group A and B in the above two parameters, P < 0.01 and P < 0.05. The analgisia maintenence time of single injection was D > A > B > C, that of group D was significantly longer than that of group A (P < 0.01). It indicated that the epidural injection with LB was more rapid and potent than that with lappaconitine alone in post-operative analgesia, and the former had no side-effect, it was safer than morphine. 相似文献
106.
本文概述了离子注入过程中污染产生的原因和防止污染的措施,特别强调了对微粒污染和金属污染的防护以满足ULSI加工对离子注入的要求。 相似文献
107.
108.
109.
110.
Zhengmao Ye Campbell J.C. Zhonghui Chen Eui-Tae Kim Madhukar A. 《Quantum Electronics, IEEE Journal of》2002,38(9):1234-1237
An InAs/AlGaAs quantum-dot infrared photodetector based on bound-to-bound intraband transitions in undoped InAs quantum dots is reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 /spl mu/m. At 77 K and -0.7 V bias, the responsivity was 14 mA/W and the detectivity, D*, was 10/sup 10/ cm/spl middot/Hz/sup 1/2//W. 相似文献