全文获取类型
收费全文 | 254881篇 |
免费 | 3566篇 |
国内免费 | 1684篇 |
专业分类
电工技术 | 5002篇 |
综合类 | 337篇 |
化学工业 | 35602篇 |
金属工艺 | 10485篇 |
机械仪表 | 7868篇 |
建筑科学 | 6632篇 |
矿业工程 | 546篇 |
能源动力 | 6839篇 |
轻工业 | 23421篇 |
水利工程 | 1814篇 |
石油天然气 | 1221篇 |
武器工业 | 29篇 |
无线电 | 36018篇 |
一般工业技术 | 49279篇 |
冶金工业 | 49699篇 |
原子能技术 | 3608篇 |
自动化技术 | 21731篇 |
出版年
2021年 | 1605篇 |
2019年 | 1585篇 |
2018年 | 2290篇 |
2017年 | 2303篇 |
2016年 | 2607篇 |
2015年 | 2087篇 |
2014年 | 3396篇 |
2013年 | 11442篇 |
2012年 | 5944篇 |
2011年 | 8544篇 |
2010年 | 6695篇 |
2009年 | 7846篇 |
2008年 | 8560篇 |
2007年 | 8846篇 |
2006年 | 7996篇 |
2005年 | 7379篇 |
2004年 | 7112篇 |
2003年 | 6830篇 |
2002年 | 6466篇 |
2001年 | 6773篇 |
2000年 | 6306篇 |
1999年 | 6695篇 |
1998年 | 16116篇 |
1997年 | 11366篇 |
1996年 | 9176篇 |
1995年 | 6864篇 |
1994年 | 6115篇 |
1993年 | 5872篇 |
1992年 | 4334篇 |
1991年 | 4202篇 |
1990年 | 4088篇 |
1989年 | 3903篇 |
1988年 | 3624篇 |
1987年 | 3008篇 |
1986年 | 2996篇 |
1985年 | 3469篇 |
1984年 | 3116篇 |
1983年 | 2885篇 |
1982年 | 2761篇 |
1981年 | 2686篇 |
1980年 | 2423篇 |
1979年 | 2351篇 |
1978年 | 2174篇 |
1977年 | 2619篇 |
1976年 | 3527篇 |
1975年 | 1880篇 |
1974年 | 1709篇 |
1973年 | 1722篇 |
1972年 | 1388篇 |
1971年 | 1255篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Ion beam assisted deposition (IBAD) of thin films is still a new technology with respect to the number of applications. A broader industrial application depends on the availability and versatility of facilities which are able to process various kinds of workpieces under appropriate conditions. Recently, IBAD facilities of the second generation were described in literature and are partially commercially available. In the present report such IBAD machines with their special features such as number and kind of ion sources and evaporators are described. Particularly, the set-up of the ALLIGATOR, a versatile IBAD device for coating complex workpieces under ion bombardment with a broad range of ion energies, is described. As an application example, recent results on the treatment of medical implants are discussed. In -vivo tests of coated cardiovascular stents showed that the deposited noble metal films were effective in influencing the corrosivity and thromboresistance of the implant 相似文献
92.
In a prospective study we found good results concerning postoperative complications (21%), perioperative lethality (3.2%) and lethality during hospital stay (6.5%) after implantation of dynamic hip screws (DHS) in patients with per- and subtrochanteric fractures of the femur. The ability to walk, as well as housing and social care postoperatively and follow-up for at least six months after dismissal demonstrates the importance of these fractures for the elderly. One of three patients needs professional care, 21% at home, 13% in nursing homes. Six months after operation the lethality is nearly 20%, i.e. three times higher than in hospital. These are the essential data for all techniques of osteosynthesis used in patients with these fractures, which could only be documented in prospective studies. 相似文献
93.
94.
95.
M.E.W. Eggenkamp V. A. Shvarts R. Blaauwgeers A. Storm R. Jochemsen G. Frossati 《Journal of Low Temperature Physics》1998,110(1-2):299-304
This paper focuses on the hydrodynamics of third sound on a superfluid
3
He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range. 相似文献
96.
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
97.
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
98.
99.
T P?usa P Górski H Frank-Piskorska M Kowalski J Kruszewski P Kuna M Kurek R Kurzawa W Silny E Zawisza 《Canadian Metallurgical Quarterly》1996,1(4):292-293
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre. 相似文献
100.