全文获取类型
收费全文 | 7428篇 |
免费 | 22篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 161篇 |
金属工艺 | 16篇 |
机械仪表 | 27篇 |
建筑科学 | 34篇 |
能源动力 | 17篇 |
轻工业 | 98篇 |
水利工程 | 13篇 |
石油天然气 | 3篇 |
无线电 | 116篇 |
一般工业技术 | 154篇 |
冶金工业 | 6643篇 |
原子能技术 | 4篇 |
自动化技术 | 144篇 |
出版年
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 15篇 |
2013年 | 29篇 |
2012年 | 40篇 |
2011年 | 51篇 |
2010年 | 48篇 |
2009年 | 28篇 |
2008年 | 35篇 |
2007年 | 42篇 |
2006年 | 34篇 |
2005年 | 37篇 |
2004年 | 41篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 27篇 |
2000年 | 22篇 |
1999年 | 206篇 |
1998年 | 2118篇 |
1997年 | 1190篇 |
1996年 | 779篇 |
1995年 | 406篇 |
1994年 | 357篇 |
1993年 | 407篇 |
1992年 | 48篇 |
1991年 | 107篇 |
1990年 | 78篇 |
1989年 | 91篇 |
1988年 | 93篇 |
1987年 | 95篇 |
1986年 | 84篇 |
1985年 | 85篇 |
1984年 | 14篇 |
1983年 | 16篇 |
1982年 | 39篇 |
1981年 | 50篇 |
1980年 | 40篇 |
1978年 | 21篇 |
1977年 | 166篇 |
1976年 | 328篇 |
1975年 | 17篇 |
1974年 | 5篇 |
1970年 | 4篇 |
1955年 | 7篇 |
排序方式: 共有7450条查询结果,搜索用时 11 毫秒
1.
2.
3.
E Persson M Ljunggren J la Cour Jansen R Strube L J?nsson 《Water science and technology》2006,53(12):139-147
A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis. 相似文献
4.
JW DiFiore DO Fauza R Slavin CA Peters JC Fackler JM Wilson 《Canadian Metallurgical Quarterly》1994,29(2):248-56; discussion 256-7
Infants with congenital diaphragmatic hernia (DH) and profound pulmonary hypoplasia are currently unsalvageable. The authors previously demonstrated that tracheal ligation (TL) accelerates fetal lung growth and reverses the pulmonary hypoplasia of fetal nephrectomy. The purpose of this study was to determine if the pulmonary hypoplasia of experimental DH could be similarly reversed and, if so, whether the resulting lungs would show better function than those of their DH counterparts. Eighteen fetal lambs were divided into three experimental groups of six animals each. In group 1, DH was created at 90 days' gestation. In group 2, DH was created at 90 days' gestation and TL performed during the same operation. Group 3 consisted of sham-operated controls. These animals were delivered near full-term, and their lungs analyzed by standard morphometric techniques. Ten additional fetal lambs were divided into two experimental groups of five animals each. In group 4, DH was created at 90 days' gestation. In group 5, DH was created at 90 days' gestation and TL performed 20 days later, at 110 days' gestation. These animals were pressure-ventilated via tracheostomy over a 2-hour period in which PaO2, PaCO2, and compliance were measured. Intratracheal pressure (ITP) was measured at the time of delivery in all groups. Upon retrieval, DH animals had abdominal viscera in the chest and small lungs; in contrast, DH/TL animals had the herniated viscera reduced from the chest by enlarged lungs. DH/TL lungs showed markedly increased growth, with significant increases in lung volume:body weight ratio (LV:BW; P = .0001), alveolar surface area (ALV.SA; P = .0001), and alveolar number (ALV#) (P = .0001) when compared with those of the DH or control group. This growth was associated with a normal maturation pattern based on histological appearance, normal airspace fraction, and normal alveolar numerical density. ITP in the DH/TL group was increased when compared with that of DH and control animals (P = .0001). Total lung DNA and protein were both elevated in the DH/TL animals (P = .0001). However, the DNA:protein ratio remained normal, suggesting lung growth had occurred through cell proliferation, not by hypertrophy. When ventilated over a range of settings, DH/TL lungs were more compliant (P = .0001) and achieved higher PaO2s (P < .003) and lower PaCO2s (P = .0001) than their DH counterparts. From these data, the authors conclude: (1) Experimental fetal DH produces hypoplastic lungs that are not capable of adequate gas exchange with conventional ventilation.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
5.
RA Kilani P Hmiel MK Garver SK Srinathan KM Wickline JC Langer 《Canadian Metallurgical Quarterly》1996,31(10):1427-1429
Although jejunal atresia occasionally may occur with a familial pattern, an association with renal disease has not been described. The authors report on three family members treated over two generations, all of whom had both proximal jejunal atresia and renal dysplasia. This association was most likely inherited as an autosomal dominant trait. 相似文献
6.
L D''Hondt C Chatelain C Doyen JC Osselaer A Ferrant A Bosly 《Canadian Metallurgical Quarterly》1996,38(4):353-354
We report the case of a young patient with refractory acute lymphoblastic leukemia relapse, after allogeneic bone marrow transplantation, who was treated by donor leukocyte infusions. We observed potent adoptive immunotherapy which produced a cytologic complete remission and total chimeric state. This was of short duration and the patient died of severe graft-versus-host disease. We present a short summary of the literature concerning acute lymphoblastic leukemia and donor leukocyte infusions. 相似文献
7.
Three different fully implantable venous access devices were randomly inserted in 72 patients. Comparison both from the point of view of their ease of insertion and their later use failed to show any significant difference between the three systems. 相似文献
8.
RM Bionta G Blewitt CB Bratton D Casper A Ciocio R Claus M Crouch ST Dye S Errede GW Foster W Gajewski KS Ganezer M Goldhaber TJ Haines TW Jones D Kielczewska WR Kropp JG Learned JM LoSecco J Matthews HS Park LR Price F Reines J Schulz S Seidel E Shumard D Sinclair HW Sobel JL Stone L Sulak R Svoboda G Thornton van der Velde JC C Wuest 《Canadian Metallurgical Quarterly》1987,36(1):30-36
9.
10.
ZA Varga JF Thompson JC Locke-Edmunds RN Baird JR Farndon 《Canadian Metallurgical Quarterly》1995,82(6):765-769
The Haemocell S-350 device has recently been introduced for intraoperative autotransfusion. The system uses a novel membrane filter to process shed blood. In the first part of this study a 0.2-micron pore size filter was used in a randomized trial comparing the use of autotransfusion (n = 8) with bank blood controls (n = 9) during aortic reconstruction. This part of the trial was abandoned because of unexpected non-surgical bleeding. Bank blood requirements fell from a median of 3.0 (range 0.0-9.0) units to 1.5 (range 0.0-7.0) units when autotransfusion was used, but these patients had a greater perioperative blood loss (1791 (range 932-3104) versus 1140 (range 440-3840) ml). There was evidence of postoperative heparin excess with an activated partial thromboplastin time ratio of 1.3 (range 0.9-3.0) versus 1.0 (range 1.0-1.2) in controls and an activated clotting time of 206 (range 143-280) versus 137 (range 107-142) s. This was confirmed by raised plasma heparin levels and a prolonged thrombin time normalized by protamine. To improve performance a 0.6-micron pore size filter was studied in ten patients. Filtration efficiency doubled from 19 to 38 per cent. Electron micrographs demonstrated better filter clearance, but 44 per cent of the original concentration of heparin remained in the reinfusate. The S-350 device may be an attractive alternative to centrifugation for intraoperative autotransfusion but, until efficiency is improved, it should only be used for cardiovascular surgery when excess heparin can be reversed with protamine. 相似文献