全文获取类型
收费全文 | 62733篇 |
免费 | 2786篇 |
国内免费 | 359篇 |
专业分类
电工技术 | 762篇 |
综合类 | 592篇 |
化学工业 | 11702篇 |
金属工艺 | 1265篇 |
机械仪表 | 1489篇 |
建筑科学 | 2223篇 |
矿业工程 | 261篇 |
能源动力 | 1384篇 |
轻工业 | 7358篇 |
水利工程 | 610篇 |
石油天然气 | 349篇 |
武器工业 | 31篇 |
无线电 | 4667篇 |
一般工业技术 | 10198篇 |
冶金工业 | 14192篇 |
原子能技术 | 387篇 |
自动化技术 | 8408篇 |
出版年
2023年 | 467篇 |
2022年 | 679篇 |
2021年 | 1346篇 |
2020年 | 1002篇 |
2019年 | 1014篇 |
2018年 | 1870篇 |
2017年 | 1853篇 |
2016年 | 1951篇 |
2015年 | 1472篇 |
2014年 | 1935篇 |
2013年 | 3753篇 |
2012年 | 3185篇 |
2011年 | 3178篇 |
2010年 | 2515篇 |
2009年 | 2383篇 |
2008年 | 2642篇 |
2007年 | 2417篇 |
2006年 | 1913篇 |
2005年 | 1606篇 |
2004年 | 1635篇 |
2003年 | 1725篇 |
2002年 | 1927篇 |
2001年 | 1515篇 |
2000年 | 1088篇 |
1999年 | 1182篇 |
1998年 | 4676篇 |
1997年 | 2848篇 |
1996年 | 1950篇 |
1995年 | 1206篇 |
1994年 | 988篇 |
1993年 | 1000篇 |
1992年 | 429篇 |
1991年 | 410篇 |
1990年 | 393篇 |
1989年 | 390篇 |
1988年 | 344篇 |
1987年 | 304篇 |
1986年 | 307篇 |
1985年 | 375篇 |
1984年 | 287篇 |
1983年 | 247篇 |
1982年 | 266篇 |
1981年 | 294篇 |
1980年 | 274篇 |
1979年 | 207篇 |
1978年 | 202篇 |
1977年 | 324篇 |
1976年 | 626篇 |
1975年 | 170篇 |
1973年 | 164篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
We managed four cases of lymphorrhea after extraperitoneal pelvic lymphadenectomy by means of minocycline instillation into the cavity around the drainage tube. Two patients had concomitantly undergone cystectomy and one prostatectomy via the extraperitoneal approach. In all four cases, the lymphorrhea markedly subsided, which dramatically shortened the duration of drainage. No side effects occurred. These findings indicate that minocycline instillation is an efficacious treatment for lymphorrhea. 相似文献
52.
53.
It is very difficult to have a clear and homogeneous idea of the embryo metabolism. In fact it may vary from one species to another and also according to the embryonic stage: i.e. before and after genomic activation. Basic compounds such as glucose may be toxic, but obviously, it is more the problem of the quantity introduced in the culture media and an unsuitable balance between the metabolites which may impair the embryonic development. At low concentration glucose is actively metabolised by embryos. High levels of amino acids are deleterious (due to release of ammonia), but they are necessary at low concentrations. Addition of serum or other biological fluids is generally useless. Further knowledge on embryo metabolism is necessary to avoid culture medium related delay or developmental blocks. Sequential media are at least partly the answer. 相似文献
54.
55.
An in situ NMR study of tert-butanol dehydration in 95 and 85% sulfuric acid did not indicate the formation of tert-butyl cations as active reaction intermediates. Instead, only NMR lines from oxonium ions under the condition of fast exchange with water and the acid were observed. It is most likely that, in the concentrated acid, the active intermediates of this reaction are represented by tert-butyl sulfuric ester which probably is a precursor of invisible tert-butyl carbenium ions representing short-lived excited or transition states. 相似文献
56.
57.
Biesemans S. Hendriks M. Kubicek S. De Meyer K. 《Electron Devices, IEEE Transactions on》1998,45(6):1310-1316
A method to analyze the accuracy of the extracted values for the channel length (Leff) and series resistance (Rs) of MOSFET devices is presented. The analysis is based on a statistical argument being the variance σ of the extracted results. This variance is found to be a good measure for the accuracy of the particular extraction method used. It is shown that, in the case of deep submicron technologies, errors as large as 200 nm for ΔL can be made for these extraction methods depending on the process design and the process control. The use of a single transistor method is suggested as a possible solution to the low accuracy of the L-array methods 相似文献
58.
59.
The influence of ointment formulation on the stability, the in-vitro release and the in-vivo absorption through the skin of rabbits was investigated. The choice of the selected ointments has no influence on the drug stability with the exception of an acidified emulsion base. A good correlation between in-vitro release and in-vivo absorption was found revealing that metronidazole was quickly released and effectively absorbed from a polyethylene glycol base. 相似文献
60.
The electrolytical methanogenic/methanotrophic coupling (eMaMoC) process was tested in a laboratory-scale single-stage reactor for the treatment of tetrachloroethene (PCE)-contaminated waters. A water electrolysis cell was placed directly in the effluent recirculation loop for the supply of both O2 and H2 to the system: H2 serving as the electron donor for both carbonate reduction into CH4 and reductive dechlorination. The concurrent presence of O2 and CH4 could be used by the methanotrophs for co-metabolically oxidising the chlorinated intermediates left over by the anaerobic transformation of PCE. At a PCE inlet of 33-52 microM and a hydraulic residence time (HRT) of 5.6 days, PCE reductive dechlorination to dichloroethene (DCE) was over 95% with a maximum DCE mineralisation of 83%. Fluorescence in situ hybridisation with 16S rRNA probes related to type I and type II methanotrophic bacteria were utilised to localise the methanotrophic communities in the anaerobic/aerobic granules. It evidenced that with operational time, along with increasing oxygenation rate, methanotrophic communities were specifically colonising onto the outermost layer of the anaerobic/aerobic granule. 相似文献