全文获取类型
收费全文 | 11447篇 |
免费 | 363篇 |
国内免费 | 106篇 |
专业分类
电工技术 | 232篇 |
综合类 | 194篇 |
化学工业 | 1872篇 |
金属工艺 | 350篇 |
机械仪表 | 360篇 |
建筑科学 | 348篇 |
矿业工程 | 103篇 |
能源动力 | 325篇 |
轻工业 | 598篇 |
水利工程 | 107篇 |
石油天然气 | 156篇 |
武器工业 | 16篇 |
无线电 | 1093篇 |
一般工业技术 | 2161篇 |
冶金工业 | 2964篇 |
原子能技术 | 108篇 |
自动化技术 | 929篇 |
出版年
2023年 | 91篇 |
2022年 | 170篇 |
2021年 | 221篇 |
2020年 | 187篇 |
2019年 | 147篇 |
2018年 | 248篇 |
2017年 | 198篇 |
2016年 | 214篇 |
2015年 | 201篇 |
2014年 | 264篇 |
2013年 | 569篇 |
2012年 | 377篇 |
2011年 | 447篇 |
2010年 | 383篇 |
2009年 | 367篇 |
2008年 | 360篇 |
2007年 | 334篇 |
2006年 | 306篇 |
2005年 | 259篇 |
2004年 | 236篇 |
2003年 | 223篇 |
2002年 | 200篇 |
2001年 | 171篇 |
2000年 | 217篇 |
1999年 | 279篇 |
1998年 | 929篇 |
1997年 | 574篇 |
1996年 | 445篇 |
1995年 | 296篇 |
1994年 | 293篇 |
1993年 | 279篇 |
1992年 | 161篇 |
1991年 | 168篇 |
1990年 | 125篇 |
1989年 | 133篇 |
1988年 | 138篇 |
1987年 | 129篇 |
1986年 | 105篇 |
1985年 | 141篇 |
1984年 | 121篇 |
1983年 | 138篇 |
1982年 | 104篇 |
1981年 | 105篇 |
1980年 | 102篇 |
1979年 | 89篇 |
1978年 | 77篇 |
1977年 | 104篇 |
1976年 | 155篇 |
1975年 | 57篇 |
1974年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
粉煤灰和木钙双掺用于胶结充填的正交组合试验 总被引:6,自引:0,他引:6
通过粉煤灰和木钙双掺用于尾砂胶结充填的交组合试验,提示了双掺的作用机理,建立了试验指标的二次回归程,得出了双掺时粉煤灰和木钙的最佳掺量。 相似文献
152.
153.
154.
Dung supplies are inadequate to provide enough farmyard manure (FYM) and cheap dung-cakes. Use of FYM necessitates supply of other fuels for cooking. Fertilizers consume only 5% of the thermal energy embodied in FYM. Replacement of the currently used amount of FYM by fertilizers will save fuels and costs. If all of the plant nutrients are to be supplied by FYM to a hectare of wheat crop, 2.9 tonnes of coal are needed to replace the dung-cakes lost; fertilizer use will save Rs. 1444/ha. It is suggested that FYM use be minimized and fertilizer use increased for fuel thrift. 相似文献
155.
The wide electrochemical window and ion exchange properties of a room-temperature ionic liquid (RTIL) have been exploited for the extraction of palladium from nitric acid medium into ionic liquid phase — followed by direct electrodeposition of the metal from the organic phase. Extraction of palladium by commercial Aliquat 336 ionic liquids, tri-n-octylmethylammonium chloride (TOMAC) and tri-n-octylmethylammonium nitrate (TOMAN), was studied as a function of [HNO3], [NO3−] and [TOMAN]. The distribution ratio (DPd(II)) of palladium in TOMAN increased with an increase in the concentration of nitric acid and passed through a maximum at 1.0 M nitric acid. In contrast, the DPd(II) value of palladium in TOMAC decreased continuously with an increase in the concentration of nitric acid. Substantial amounts of water and nitric acid were also co-extracted into the organic phase with palladium. 相似文献
156.
JK Tong CA Hassig GR Schnitzler RE Kingston SL Schreiber 《Canadian Metallurgical Quarterly》1998,395(6705):917-921
157.
158.
GW Mathern JK Pretorius HI Kornblum D Mendoza A Lozada JP Leite L Chimelli DE Born I Fried AC Sakamoto JA Assirati WJ Peacock GA Ojemann PD Adelson 《Canadian Metallurgical Quarterly》1998,5(3):151-176
This study determined whether hippocampal kainate (KA) receptor mRNA levels were increased or decreased in temporal lobe epilepsy patients compared with nonseizure autopsies. Hippocampal sclerosis (HS; n = 17), nonsclerosis (non-HS; n = 11), and autopsy hippocampi (n = 9) were studied for KA1-2 and GluR5-7 mRNA levels using semiquantitative in situ hybridization techniques, along with neuron densities. Compared with autopsy hippocampi, HS and non-HS cases showed decreased GluR5 and GluR6 hybridization densities per CA2 and/or CA3 pyramid. Furthermore, HS patients demonstrated increased KA2 and GluR5 hybridization densities per granule cell compared with autopsy hippocampi. These findings indicate that chronic temporal lobe seizures were associated with differential changes in hippocampal KA1-2 and GluR5-7 hybridization densities that vary by subfield and pathology group. In temporal lobe epilepsy patients, these results support the hypothesis that pyramidal cell GluR5 and GluR6 mRNA levels are decreased as a consequence of seizures, and in HS patients granule cell KA2 and GluR5 mRNA levels are increased in association with aberrant fascia dentata mossy fiber sprouting and/or hippocampal neuronal loss. 相似文献
159.
JK Kang SW Lee MW Baik BC Son YK Hong CK Jung KH Ryu 《Canadian Metallurgical Quarterly》1998,14(7):297-301
Accurate assessment and replacement of blood loss and fluid-electrolyte deficit during craniosynostosis repair is difficult owing to patient size and the diversity of surgical technique. Forty-three patients undergoing primary craniosynostosis repair over a 10-year period were studied retrospectively to determine blood loss and fluid deficit and to assess blood transfusion practices during both intraoperative and postoperative periods. Blood loss was calculated on the basis of estimated red cell mass (ERCM) and fluid-electrolyte imbalance was investigated with blood samplings. Blood transfusion was considered appropriate if the postoperative or posttransfusion ERCM was within 12% of the preoperative value. Estimated fluid requirement (EFR) was used in 4 ml kg(-1) h(-1) except for neonates. Intraoperatively, 80% of all patients were appropriately managed with respect to blood transfusion and EFR. Postoperatively only 20% of the patients receiving transfusions were transfused appropriately. In 23.3% of these patients (10/43) unexpected respiratory distress developed immediately after their recovery from the anesthesia. With the measurement of estimated blood volume and allowable blood loss, appropriate transfusion could be achieved for the successful treatment of the primary craniosynostosis. 相似文献
160.
RA Alvarez AJ Ghalayini P Xu A Hardcastle S Bhattacharya PN Rao MJ Pettenati RE Anderson W Baehr 《Canadian Metallurgical Quarterly》1995,29(1):53-61
Defects in the Drosophila norpA (no receptor potential A) gene encoding a phosphoinositide-specific phospholipase C (PLC) block invertebrate phototransduction and lead to retinal degeneration. The mammalian homolog, PLCB4, is expressed in rat brain, bovine cerebellum, and the bovine retina in several splice variants. To determine a possible role of PLCB4 gene defects in human disease, we isolated several overlapping cDNA clones from a human retina library. The composite cDNA sequence predicts a human PLC beta 4 polypeptide of 1022 amino acid residues (MW 117,000). This PLC beta 4 variant lacks a 165-amino-acid N-terminal domain characteristic for the rat brain isoforms, but has a distinct putative exon 1 unique for human and bovine retina isoforms. A PLC beta 4 monospecific antibody detected a major (130 kDa) and a minor (160 kDa) isoform in retina homogenates. Somatic cell hybrids and deletion panels were used to localize the PCLB4 gene to the short arm of chromosome 20. The gene was further sublocalized to 20p12 by fluorescence in situ hybridization. 相似文献