全文获取类型
收费全文 | 1352篇 |
免费 | 62篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 260篇 |
金属工艺 | 25篇 |
机械仪表 | 34篇 |
建筑科学 | 53篇 |
矿业工程 | 2篇 |
能源动力 | 64篇 |
轻工业 | 70篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 124篇 |
一般工业技术 | 248篇 |
冶金工业 | 288篇 |
原子能技术 | 14篇 |
自动化技术 | 209篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 25篇 |
2017年 | 34篇 |
2016年 | 31篇 |
2015年 | 24篇 |
2014年 | 41篇 |
2013年 | 87篇 |
2012年 | 71篇 |
2011年 | 73篇 |
2010年 | 66篇 |
2009年 | 54篇 |
2008年 | 64篇 |
2007年 | 76篇 |
2006年 | 44篇 |
2005年 | 51篇 |
2004年 | 52篇 |
2003年 | 37篇 |
2002年 | 37篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1999年 | 21篇 |
1998年 | 94篇 |
1997年 | 54篇 |
1996年 | 43篇 |
1995年 | 32篇 |
1994年 | 30篇 |
1993年 | 29篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有1420条查询结果,搜索用时 15 毫秒
1.
2.
Defects are often present in rolled products, such as wire rod. The market demand for wire rod without any defects has increased. In the final wire rod products, defects originating from steel making, casting, pre‐rolling of billets and during wire rod rolling can appear. In this work, artificial V‐shaped longitudinal surface cracks have been analysed experimentally and by means of FEM. The results indicate that the experiments and FEM calculations show the same tendency except in two cases, where instability due to fairly “round” false round bars disturbed the experiment. FE studies in combination with practical experiments are necessary in order to understand the behaviour of the material flows in the groove and to explain whether the crack will open up as a V‐shape or if it will be closed as an I‐shape. 相似文献
3.
爱立信IMS weShare业务有20%的开发与用户视觉体验相关(用户界面、图标、标签以及进度条),其它的80%则主要致力于设备间的系统.与此相对比,用户的体验则完全(100%)有赖于其可接触的事物. 相似文献
4.
H Eriksson 《Canadian Metallurgical Quarterly》1996,2(3):163-168
This paper reviews recent changes in morbidity and mortality of respiratory syncytial virus (RSV) infection in infants with congenital heart disease. Mortality since the late 1970s has declined substantially, from approximately 37% to 3%. Although the frequency of admission to intensive care units has declined from approximately 60% to 30%, the frequency for mechanical ventilatory support has not changed significantly. Because mortality dropped prior to the widespread use of ribavirin, it is difficult to ascribe the improvement to this therapy. In infants with congenital heart disease (CHD), nosocomial infection remains a significant problem, accounting for approximately 33% of the RSV cases. Some authors report significant reductions in hospital-acquired RSV by use of gloves and gowns for contacts with infectious cases. Efforts at primary prevention have encountered problems with development of an RSV vaccine. Preliminary data from studies of passive immunization using immune globulins with high RSV antibody titers suggest that this therapy may reduce the severity of RSV infection in infants with serious heart disease. 相似文献
5.
6.
Estrogen treatment affects the hepatic synthesis and/or secretion of several proteins involved in clinically important pathological processes such as atherosclerosis, hypertension, and thrombosis. The endocrine regulation of the estrogen receptor (ER) concentration in primary cultures of rat hepatocytes was studied. Human growth hormone (hGH) and dexamethasone (DEX) in combination increased ER concentration 6-fold and ER mRNA levels 2.5-fold. These effects were not significantly different from those observed after treatment with the purely somatogenic bovine growth hormone (GH) in combination with DEX. Treatment with the lactogen ovine prolactin in the presence or absence of DEX did not significantly affect ER or ER mRNA concentrations. Triiodothyronine treatment at the most effective concentration (50 nM) increased ER and ER mRNA levels twofold. Medium supplementation with estradiol (0.1 nM) throughout the experiment did not affect the response to treatment with hGH and DEX. Treatment with high concentrations of ethinylestradiol in combination with hGH and DEX, however, increased the ER level twice as much as hGH and DEX without addition of estradiol or ethinylestradiol, whereas the ER mRNA concentration was the same in both the GH+DEX group and GH+ DEX+ (estradiol or ethinylestradiol) groups. These data indicate the importance of GH in combination with glucocorticoids for the maintenance of ER concentrations in the rat liver. Thyroid hormones may be of some, although minor importance, whereas the data suggest that prolactin is not directly involved in hepatic ER regulation. 相似文献
7.
C Held P Hjemdahl N Rehnqvist NH Wallén I Bj?rkander SV Eriksson L Forslund B Wiman 《Canadian Metallurgical Quarterly》1997,95(10):2380-2386
BACKGROUND: Disturbed fibrinolytic function may influence the progression of coronary atherosclerosis and contribute to thrombotic cardiovascular (CV) events. METHODS AND RESULTS: In the Angina Prognosis Study in Stockholm (APSIS), patients with stable angina pectoris were studied prospectively during double-blind treatment with metoprolol or verapamil. Various measures of fibrinolytic function were studied in 631 (of 809) patients. During a median follow-up time of 3.2 years (2132 patient-years), 32 patients suffered a CV death, 21 had a nonfatal myocardial infarction (MI), and 77 underwent revascularization. Plasma levels of tissue plasminogen activator (TPA) activity and antigen (ag), plasminogen activator inhibitor (PAI-1) activity at test, and TPA responses to exercise were determined at baseline and after 1 month's treatment and were related to subsequent fatal and nonfatal CV events. Univariate Cox regression analysis revealed that elevated levels of TPA-ag at rest (P < .05), high PAI-1 activity (P < .05), and low TPA-ag responses to exercise (P < .05) were associated with increased risk of subsequent CV death. After adjustment for baseline risk factors, TPA-ag independently predicted CV death or MI. In addition, PAI-1 activity independently predicted CV death or MI in male patients. Verapamil treatment was associated with a 10% decrease of TPA-ag levels and metoprolol treatment with a 2% increase (P < .001 for treatment difference). CONCLUSIONS: Plasma TPA-ag levels at rest, and among male patients PAI-1 activity as well, independently predict subsequent CV death or MI in patients with stable angina pectoris. 相似文献
8.
S Karacagil A Holmberg A Narbani I Eriksson D Bergqvist 《Canadian Metallurgical Quarterly》1996,12(3):337-341
Faecal samples from asymptomatic dairy cows and calves from a farm on the Island Falster, Denmark, were examined by a sucrose gradient flotation technique. Giardia cysts were found in 7.6% of the 92 samples, and estimated cyst excretion rates ranged from 50-200 cysts per gram faeces. Given that Giardia has the potential to cause clinical disease in cattle and to be transmitted to other animal species and humans, finding the parasite in cattle may be of major epidemiological significance. Future work should focus on elucidating the pathogenicity, transmission patterns and the genetic structure of Giardia populations in cattle in Denmark. 相似文献
9.
10.
New CAMAC based data acquisition and beam control system for Lund nuclear microprobe 总被引:1,自引:0,他引:1
Mikael Elfman Per Kristiansson Klas Malmqvist Jan Pallon Anders Sjland Rogerio Utui Changyi Yang 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1997,130(1-4):123-126
A new CAMAC based data acquisition system has been installed at the Lund Nuclear Microprobe facility. This paper reports on the development and present status of the data acquisition system. The system is a true multiparameter CAMAC based system with fast Fera bus readout and in crate memory buffer. The user interface is based on Sparrow Kmax software for a Power Macintosh platform. The system read out and tag the event data with position on-line, which make fast on-line monitoring of spectra or element maps possible.Simultaneously, all data can be saved event by event for off-line analysis. The beam scanning part is software controlled through a timed D/A converter, this allows fast scanning of the beam. With a CCD-camera and video card the area to be analysed could be defined directly from the image, and the sample position can be moved. Any kind of irregular scan patterns could be defined. 相似文献