全文获取类型
收费全文 | 7301篇 |
免费 | 436篇 |
国内免费 | 296篇 |
专业分类
电工技术 | 416篇 |
综合类 | 350篇 |
化学工业 | 759篇 |
金属工艺 | 407篇 |
机械仪表 | 341篇 |
建筑科学 | 307篇 |
矿业工程 | 153篇 |
能源动力 | 107篇 |
轻工业 | 671篇 |
水利工程 | 101篇 |
石油天然气 | 110篇 |
武器工业 | 83篇 |
无线电 | 491篇 |
一般工业技术 | 661篇 |
冶金工业 | 2283篇 |
原子能技术 | 100篇 |
自动化技术 | 693篇 |
出版年
2024年 | 32篇 |
2023年 | 60篇 |
2022年 | 138篇 |
2021年 | 197篇 |
2020年 | 140篇 |
2019年 | 116篇 |
2018年 | 109篇 |
2017年 | 126篇 |
2016年 | 117篇 |
2015年 | 154篇 |
2014年 | 205篇 |
2013年 | 341篇 |
2012年 | 397篇 |
2011年 | 430篇 |
2010年 | 365篇 |
2009年 | 327篇 |
2008年 | 376篇 |
2007年 | 373篇 |
2006年 | 297篇 |
2005年 | 229篇 |
2004年 | 188篇 |
2003年 | 138篇 |
2002年 | 109篇 |
2001年 | 111篇 |
2000年 | 96篇 |
1999年 | 124篇 |
1998年 | 627篇 |
1997年 | 393篇 |
1996年 | 285篇 |
1995年 | 164篇 |
1994年 | 163篇 |
1993年 | 127篇 |
1992年 | 45篇 |
1991年 | 49篇 |
1990年 | 46篇 |
1989年 | 60篇 |
1988年 | 45篇 |
1987年 | 36篇 |
1986年 | 26篇 |
1985年 | 55篇 |
1984年 | 38篇 |
1983年 | 25篇 |
1982年 | 27篇 |
1981年 | 31篇 |
1979年 | 35篇 |
1978年 | 37篇 |
1977年 | 78篇 |
1976年 | 137篇 |
1975年 | 26篇 |
1973年 | 25篇 |
排序方式: 共有8033条查询结果,搜索用时 31 毫秒
61.
鼠笼式搅拌磨的流体场建模及计算机仿真 总被引:2,自引:1,他引:1
搅拌磨机在工业与研究领域是一种效率高的超细粉磨设备。为了优化设计参数,提高鼠笼式搅拌磨机的粉碎效果,需要对磨机研磨室内的流体场作深入的研究。利用Ansys有限元软件对鼠 式搅拌磨机研磨室的圆截面内的流体场进行仿真分析。通过对仿真结果的分析可知,在该流体场内存在着2个速度梯度较高的区域。在这2个区域中,粉碎作用明显。为了得到最佳的粉碎效果,应该使磨球尽可能地通过这2个区域。 相似文献
62.
SJ Phillips 《Canadian Metallurgical Quarterly》1993,55(5):1281-1282
63.
Advances in neonatal care have resulted in an enlarging population of vulnerable premature newborns at risk for necrotizing enterocolitis (NEC). This article presents data supporting a unifying hypothesis for the initiation of NEC based on bacteria as the inciting agent(s), and the preterm baby as the vulnerable host. Facts and controversies concerning the pathology, microbiology, clinical presentation, management and outcome of infants afflicted with NEC are presented. 相似文献
64.
Salicylate-kodein is a widely used analgesic agent, particularly in outpatient practice. Salicylates have been incriminated in hepatic injury while kodein may induce biliary spasm. We report here a case of granulomatous hepatitis attributed to prolonged intake of this combination, which has never been reported previously to our knowledge. 相似文献
65.
66.
D. J. Benford T. R. Hunter T. G. Phillips 《Journal of Infrared, Millimeter and Terahertz Waves》1998,19(7):931-938
With the advent of large submillimeter telescopes at high, dry sites, the atmospheric background noise in a moderate bandwidth can be low enough to challenge the ability of instrument designers to produce sufficiently low noise bolometers to be background limited. We compare the predictions for the noise power of a bolometer observing through an emissive atmosphere, considering the effect of atmospheric absorption, telescope optical efficiency, and detector optical efficiency, with measurements through the atmosphere over Mauna Kea. 相似文献
67.
Pharmacologic profile of survivors of acute myocardial infarction at United States academic hospitals 总被引:1,自引:0,他引:1
BG Phillips JM Yim EJ Brown N Bittar TJ Hoon C Celestin PH Vlasses JL Bauman 《Canadian Metallurgical Quarterly》1996,131(5):872-878
Optimal drug therapy for patients with acute myocardial infarction (AMI) is well described in the medical literature. However, data on the actual pharmacologic management of patients surviving AMI at academic hospitals is unavailable. The purpose of this study was to document treatment profiles in 500 patients surviving AMI at 12 academic hospitals in the United States. These profiles were compared with established guidelines and were evaluated for trends. Overall, thrombolytics (streptokinase > or = tissue-type plasminogen activator) were administered in 29% of the patients, with a greater proportion of patients receiving beta-blockers than calcium channel antagonists in the initial 72 hours (61% vs 40%; p < 0.005) and at discharge (51% vs 35%; p < 0.005). Further, women were less likely than men to receive thrombolytic therapy (odds ratio [OR] = 0.61; confidence interval [CI], 0.54 to 0.69) or beta-blocker therapy within the first 72 hours (OR = 0.61; CI, 0.55 to 0.67) or at hospital discharge (OR = 0.53; CI, 0.48 to 0.58). Overall, improvements could still be made in the number of patients who receive thrombolytic and acute and chronic beta-blocker therapies after AMI, particularly in women. Changes in treatment profiles may be a reflection of the publication of large clinical trials. 相似文献
68.
69.
Fetal and maternal lipoprotein metabolism in human pregnancy complicated by type I diabetes mellitus
Serum lipid, apolipoprotein concentration, and lipoprotein composition were determined in maternal and umbilical venous cord blood at delivery by elective Cesarean section (CS) in 10 singleton, full-term pregnancies with maternal insulin-dependent diabetes mellitus (type I DM), which predated pregnancy, and in 22 nondiabetic pregnancies. The objectives of the study were to determine the influence of maternal type I DM, and hence potential fetal overnutrition on fetal lipid metabolism. There were no significant differences in gestational age, fetal weight, or fetal serum insulin concentration between the type I DM group and those with nondiabetic pregnancies, although fetal venous cord blood glucose was 3.4 mmol/L (3.0-4.5 mmol/L) (median and 25th-75th percentiles) and 2.9 mmol/L (2.0-3.4 mmol/L), respectively, and maternal Hemoglobin A1c [9.6% (8.2-10.7%) and 6.8% (6.3-7.8%), respectively], was significantly greater in the type I DM subjects (P < 0.02 and 0.002 respectively). Plasma nonesterified fatty acid (NEFA) concentrations were lower in the type I DM mothers [0.85 mmol/L (0.56-2.31 mmol/L) compared with 1.14 mmol/L (0.88-1.24 mmol/L] in nondiabetic pregnancies; P < 0.0001). Serum high-density lipoprotein phospholipids (HDL-PL) were increased in type I DM mothers because of elevated HDL2 phospholipid [0.39 mmol/L (0.27-0.48 mmol/L) compared with 0.12 mmol/L (0.06-0.21 mmol/L), respectively, P < 0.01). The maternal HDL cholesterol (C) concentration was not significantly different in the uncomplicated and type I DM pregnancies. However, in the umbilical venous cord blood, serum levels of NEFA [0.49 mmol/L (0.33-1.29 mmol/L) in type I DM compared with 0.13 mmol/L (0.06-0.33 mmol/L) in nondiabetics; P < 0.02)], total cholesterol (TC) [2.87 mmol/L (1.65-4.86 mmol/L) in type I DM compared with 1.65 mmol/L (1.46-1.87 mmol/L) in nondiabetics; P < 0.02]; free cholesterol (FC) [0.97 mmol/L (0.60-1.26 mmol/L) in type I DM compared with 0.62 mmol/L (0.37-0.75 mmol/L) in nondiabetics; P < 0.05), and cholesteryl ester (CE) [1.90 mmol/L (1.44-3.33 mmol/L) in type I DM compared with 1.01 mmol/L (0.83-1.24 mmol/L) in nondiabetics; P < 0.02), triglyceride (TG) (1.06 [0.50-1.91) mmol/L in type I DM compared with 0.29 [0.25-0.36] mmol/l in nondiabetics; P < 0.001), phospholipid (PL) (2.52 [1.73-3.03) mmol/L in type I DM compared with 1.34 [1.27-1.48] mmol/L in nondiabetics; P < 0.01], and the apolipoproteins A-I and B had significantly higher concentrations in type I DM. In umbilical venous cord blood, ratios of HDL-TC and HDL-PL to apo AI, reflecting the lipid content of HDL, were reduced when the mother had type I DM during pregnancy (P < 0.02 and P < 0.0001, respectively). These results indicate that maternal type I DM may lead to a fetal serum lipoprotein composition more closely resembling that seen in the adult. In type I DM, maternal TG and PL and fetal TC, TG, PL, CE, and FC were correlated to NEFA levels (P < 0.05), but not to glucose, insulin secretion, or maternal control of type I DM. These data suggest that the enhanced supply of NEFA to the fetus in type I DM pregnancies may drive the synthesis of cholesterol as well as TGs and PLs. 相似文献
70.
MI Sereno 《Canadian Metallurgical Quarterly》1998,8(2):188-194
The discovery of the Mothers against dpp (Mad) gene in Drosophila has opened a window on an entirely unique signalling pathway that functions to mediate responses to the tumour growth factor beta (TGF beta) superfamily. This pathway, which is comprised of a family of proteins related to Mad, acts to convey signals directly from TGF beta receptors to the nucleus and is implicated in the pathogenesis of human diseases. 相似文献