全文获取类型
收费全文 | 6129篇 |
免费 | 237篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 91篇 |
综合类 | 5篇 |
化学工业 | 1834篇 |
金属工艺 | 205篇 |
机械仪表 | 136篇 |
建筑科学 | 167篇 |
矿业工程 | 22篇 |
能源动力 | 221篇 |
轻工业 | 631篇 |
水利工程 | 14篇 |
石油天然气 | 11篇 |
武器工业 | 3篇 |
无线电 | 254篇 |
一般工业技术 | 892篇 |
冶金工业 | 1120篇 |
原子能技术 | 27篇 |
自动化技术 | 743篇 |
出版年
2023年 | 40篇 |
2022年 | 190篇 |
2021年 | 263篇 |
2020年 | 113篇 |
2019年 | 103篇 |
2018年 | 190篇 |
2017年 | 182篇 |
2016年 | 229篇 |
2015年 | 160篇 |
2014年 | 211篇 |
2013年 | 380篇 |
2012年 | 259篇 |
2011年 | 323篇 |
2010年 | 252篇 |
2009年 | 205篇 |
2008年 | 213篇 |
2007年 | 203篇 |
2006年 | 138篇 |
2005年 | 132篇 |
2004年 | 120篇 |
2003年 | 109篇 |
2002年 | 97篇 |
2001年 | 70篇 |
2000年 | 50篇 |
1999年 | 60篇 |
1998年 | 208篇 |
1997年 | 235篇 |
1996年 | 174篇 |
1995年 | 124篇 |
1994年 | 80篇 |
1993年 | 90篇 |
1992年 | 31篇 |
1991年 | 33篇 |
1990年 | 41篇 |
1989年 | 28篇 |
1988年 | 42篇 |
1987年 | 46篇 |
1986年 | 30篇 |
1985年 | 45篇 |
1984年 | 58篇 |
1983年 | 50篇 |
1982年 | 65篇 |
1981年 | 74篇 |
1980年 | 73篇 |
1979年 | 43篇 |
1978年 | 46篇 |
1977年 | 131篇 |
1976年 | 240篇 |
1975年 | 23篇 |
1973年 | 15篇 |
排序方式: 共有6376条查询结果,搜索用时 11 毫秒
991.
Dong Thi Thanh Thu A Lipińska L K?yszejko-Stefanowicz 《Canadian Metallurgical Quarterly》1981,28(2):175-181
1. SDS-polyacrylamide gel electrophoresis showed some slight quantitative species-dependent differences in total non-histone chromatin proteins and nuclear phosphoproteins (phenol-soluble fraction of non-histone chromatin proteins) but no differences in the DNA-binding non-histone proteins. 2. Comparative studies on DNA and RNA content, and amino acid composition of nuclear phosphoproteins and DNA-binding non-histone proteins of pancreas demonstrated a striking similarity between the two species studied. 相似文献
992.
The p-chlorophenyl glycidyl ether was polymerized in the presence of Al(OiPr)3, ZnCl2, SnCl4, BuOK, KOH and by the Al(OiPr)3ZnCl2 1:1 initiator system. Analysis of the 13C n.m.r. spectra of the poly(p-chlorophenyl glycidyl ethers) obtained has made it possible to determine their tacticity and the content of the head-to-tail and head-to-head linkages in the polymer chain. 相似文献
993.
Zbigniew Jedliński Andrej Stolarzewicz Pawel Szewczyk Ryszard Tymczyński 《Polymer Bulletin》1980,2(8):555-563
Summary Polymerization of p-chlorophenyl glycidyl ether initiated by potassium glycolates (ethylene, propylene and 2-methyl propylene glycolatea) in DMSO containing some 18-crown-6 ether or glycol was investigated. For the reaction system containing the propylene glycolate asymmetrically substituted with a methyl group, relatively high polymerization rates were obtained as compared with those found for the other systems studied, the resultant polymers also having higher molecular weights and comparatively low polydispersities. Aliphatic double bonds were found to be absent in the polymers synthesized, which would suggest that in the anionic polymerization process studied the growing chain is not transferred to the monomer.Dedicated to Prof. C.I. Simionescu on the occasion of the 60th anniversary of his birthday 相似文献
994.
The coincidence of neuronal stress induced by intoxication and an overexpression of amyloid precursor protein (APP) in the brains of children was examined. Brains of ten children accidentally intoxicated by poisonous mushroom were studied by means of immunohistochemical methods using monoclonal antibodies generated against different domains of APP and glial cell markers. Overexpression of APP was found in the brain neurons of all intoxicated children. Neurons were immunopositive with the antibodies generated against the middle (amyloid beta protein) domain of APP. No extracellular deposits were found in the tissue. Our results provided, for the first time, the evidence that overexpression of APP concomitant with the neuronal stress is age-independent phenomenon appearing not only in the brain of adults but in very young individuals as well. 相似文献
995.
M Szczepańska A Bia?ota-Szurkowska W Grzeszczak K Szprynger 《Canadian Metallurgical Quarterly》1995,52(11):552-557
Haemodynamic changes in children examined by reocardiography impedance method were compared for 15 sessions performed with new capillary cuprophan dialysers and 15 sessions performed with reused ones (fourth use). Subsequent parameters of cardiovascular system performance were assessed: CI-cardiac index, SI-stroke index, ACI-acceleration index, SVRI-systemic vascular resistance index, EF-ejection fraction, TFC-thoracic fluid conductivity, MAP-mean arterial pressure. Significant differences in MAP, EF, TFC, ACI values between the sessions with the first and the fourth use of cuprophan dialysers were noted. Marked increase of cardiac output during the acetate haemodialysis was observed as the result of afterload declining by lowering systemic vascular resistance during the session with new and reused cuprophan dialysers. Contractility of myocardium and ejection fraction significantly increased during the session performed on new dialysers. Ejection fraction remained unchanged and myocardial contractility slightly improved during the fourth use of cuprophan dialysers. 相似文献
996.
997.
K Zó?towska J Dziekońska-Rynko H Olender Z Jab?onowski 《Canadian Metallurgical Quarterly》1995,41(4):421-428
Hybrid chickens Astra S fed vitamin A deficiency diet containing 11 or 19% protein were infected with 500 invasive eggs of Ascaridia galli. One part of them received vitamin A in a dose corresponding to daily requirement, other part in double dose. After 7 weeks the extensity and intensity of ascaridiosis were determined. In pancreas and intestinal contents the activities of alpha-amylase, lipase and trypsin were measured. The invasion index was the highest in the group of chickens fed the protein and vitamin A deficiency diet. Vitamin A in a requirement dose lowered the parasite index. The results with double dose of vitamin A were worse in comparison with single dose. The activities of digestive enzymes were lower in infected animals than in the control groups. Vitamin A acted as moderator of the enzymatic changes during ascaridiosis. 相似文献
998.
In selected eye drops the value of surface tension coefficient delta 25 and critical micelle concentration (cmc) was determined. Calculation of the hydrophilic-lipophilic balance level (HLBcmc) and the solution of the surface state f.Am = K.T form of Gibbs equation enables the estimation of the type of action of micelle with lipid corneal epithelium. Particular attention has been paid to the forms of eye drops which contain benzalkonium chloride (BAC). 相似文献
999.
AK Ma?ek O Rowiński T Ostrowski L Hilgertner M Januszewicz M Szostek 《Canadian Metallurgical Quarterly》1995,50(40-44):19-22
Subclavian steal syndrome (SSS) appears when the origin of the subclavian artery (SA) is occluded or stenosed. Introduction of transcranial Doppler sonography (TCD) provided an opportunity to evaluate parameters of the blood flow in the vertebral (VA) and basilar artery (BA). Measurements of blood flow velocities performed at rest and after the brachial hyperemia test allow one to classify hemodynamic types of SSS. The aim of the study was to categorize types of steal and to compare the differences of flow patterns before and after percutaneous transluminal SA balloon angioplasty (SA-PTA). Fourty-eight patients with angiographically confirmed SSS (aged from 27 to 68 years, mean 53; 2/1 f/m ratio) were examined with 2 MHz range-gated, pulsed transcranial Doppler device (TC 2-64B EME). Both VA and BA were evaluated by the transoccipital approach at rest and during the brachial hyperemia. In 5 cases (10.4%) permanent reversal blood flow in the BA was observed (complete basilar steal). In flow in the BA blood flow was in the normal direction at rest and altered (reversed or decreased) when induced with brachial hyperemia test (transient basilar steal). In the next 14 patients (29.2%) permanently reversed VA blood flow was observed with only a slight or no alterations of the BA flow after the hyperemia test (complete vertebral steal). In the last 19 cases (39.6%) alterations of the VA blood flow without changes in BA flow were observed (latent vertebral steal). Between 1991 and 1994 twenty seven symptomatic patients with different hemodynamic types of SSS were treated with SA-PTA. TCD evaluation of VA's and BA using the hyperemia test was performed before, 3 to 7 days and 3 months after morphologically and hemodynamically successful subclavian artery balloon PTA. Normal results of vertebrobasilar examinations were obtained in 26 cases after this procedure. In one case the latent vertebral steal was detected. The 28 months mean follow-up revealed no significant changes in TCD flow patterns recorded from VA's and BA. After collecting data of about 60 patients with SSS we examined with TCD we conclude that: in patients with a hemodynamically significant SA stenosis the presence of reversed ipsilateral VA blood flow (a radiologic steal) its not a good determinant of either the presence or type of presenting symptoms and after successful PTA or recanalisation and PTA of SA in almost all cases we examined close to normal TCD recordings in BA and VA. 相似文献
1000.
K Domańska-Janik 《Canadian Metallurgical Quarterly》1996,56(2):579-585
Triptoquinone A (TQA), which is an anti-inflammatory constituent in plants, was studied for its suppressive effect on nitric oxide production by LPS. TQA significantly suppressed smooth muscle relaxation and increase in cyclic GMP levels by nitric oxide (NO) in an L-arginine-induced relaxation experiment. The mechanistic studies showed that TQA did not directly inhibit NO radicals and inducible nitric oxide synthase (iNOS) enzyme but suppressed IL-1 beta and iNOS mRNA expression by LPS. The suppression level of iNOS gene expression by TQA was comparable to that by dexamethasone. TQA may be a useful candidate for the development of a drug as a potent inhibitor of iNOS gene over-expression. 相似文献