全文获取类型
收费全文 | 5742篇 |
免费 | 203篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 60篇 |
综合类 | 67篇 |
化学工业 | 834篇 |
金属工艺 | 165篇 |
机械仪表 | 151篇 |
建筑科学 | 201篇 |
矿业工程 | 42篇 |
能源动力 | 247篇 |
轻工业 | 524篇 |
水利工程 | 23篇 |
石油天然气 | 38篇 |
武器工业 | 2篇 |
无线电 | 206篇 |
一般工业技术 | 576篇 |
冶金工业 | 2272篇 |
原子能技术 | 48篇 |
自动化技术 | 524篇 |
出版年
2024年 | 20篇 |
2023年 | 41篇 |
2022年 | 76篇 |
2021年 | 109篇 |
2020年 | 136篇 |
2019年 | 119篇 |
2018年 | 164篇 |
2017年 | 146篇 |
2016年 | 175篇 |
2015年 | 101篇 |
2014年 | 168篇 |
2013年 | 388篇 |
2012年 | 202篇 |
2011年 | 206篇 |
2010年 | 175篇 |
2009年 | 220篇 |
2008年 | 174篇 |
2007年 | 160篇 |
2006年 | 126篇 |
2005年 | 82篇 |
2004年 | 94篇 |
2003年 | 118篇 |
2002年 | 161篇 |
2001年 | 125篇 |
2000年 | 64篇 |
1999年 | 119篇 |
1998年 | 699篇 |
1997年 | 425篇 |
1996年 | 290篇 |
1995年 | 148篇 |
1994年 | 122篇 |
1993年 | 136篇 |
1992年 | 22篇 |
1991年 | 39篇 |
1990年 | 22篇 |
1989年 | 28篇 |
1988年 | 26篇 |
1987年 | 20篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 7篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 63篇 |
1976年 | 129篇 |
1975年 | 7篇 |
排序方式: 共有5980条查询结果,搜索用时 15 毫秒
1.
AE Speckens AM Van Hemert JH Bolk HG Rooijmans MW Hengeveld 《Canadian Metallurgical Quarterly》1996,26(4):745-752
BACKGROUND: Measurement of intracardiac hemodynamic parameters has been limited to brief periods in the acute care setting. We developed and evaluated an implantable hemodynamic monitor that is capable of measuring chronic right ventricular oxygen saturation and pulmonary artery pressure. METHODS AND RESULTS: The device consists of an electronic controller placed subcutaneously and two transvenous leads placed in the right ventricle (reflectance oximeter) and pulmonary artery (variable capacitance pressure sensor). Implantation was performed in 10 patients with severe left ventricular dysfunction. Average implant pulmonary artery pressures were systolic, 52 +/- 16 mm Hg; diastolic, 29 +/- 11 mm Hg; and mean, 40 +/- 12 mm Hg. The mean right ventricular oxygen saturation at implant was 51%. Provocative maneuvers, including postural changes, sublingual nitroglycerin, and bicycle exercise, demonstrated expected changes in measured oxygen saturation and pulmonary artery pressures over time. At follow-up of 0.5 to 15.5 months, there were no significant differences between pulmonary artery pressures or oxygen saturation values transmitted from the device and simultaneous measurement with balloon flotation catheters. Four of the pulmonary artery leads dislodged and three demonstrated sensor drift, whereas two of the oxygen saturation sensors failed. Four patients died and four received transplants. Pathological study did not demonstrate injury to the right ventricular outflow tract or pulmonic valve. CONCLUSIONS: Chronic measurement of hemodynamic parameters in the outpatient setting with implantable sensor technology appears to be feasible. The devices are well tolerated without significant untoward effects, and the sensors generally function well over time, providing reliable information. Clinical usefulness remains to be established. 相似文献
2.
3.
A questionnaire to evaluate the needs of dialytic patients and the burden that these have on the health service and staff, was formulated by the nurses. The results showed how the patient's case history indicate, significantly, not only personal and subjective aspects (e.g. interpersonal relationships), but also how they construct their relationships with the hospital and its service (including the hospital staff). This opens up certain reflections on what role communication and information play within the hospital structure. 相似文献
4.
5.
6.
7.
AE Segelman 《Canadian Metallurgical Quarterly》1997,45(4):16, 20-16, 22
8.
E Gürdal-Yüksel M Karada? N Ozyardimci AE Kunt-Uzaslan T Yarkin 《Canadian Metallurgical Quarterly》1996,15(2-4):161-167
The purpose of our study was to evaluate the effects of cigarette smoking and serum lipids, folate, and vitamin B12 on the development of lung cancer in the Turkish population. The study group consisted of patients with histologically proven lung cancer and the control group comprised healthy smokers being followed in our smoking cessation outpatient department. Smoking history was obtained from all subjects and serum total cholesterol, HDL cholesterol, triglycerides, vitamin B12, and folate levels were measured. Pack/years of cigarettes smoked were significantly higher in the subjects with lung cancer than in the control group (p < 0.01). Serum total cholesterol, HDL cholesterol, triglyceride, serum folate, and vitamin B12 levels were within normal limits in both groups (p < 0.05), but serum vitamin B12 levels were statistically significantly higher (p < 0.01) in the cancer group than in the controls. In our study, we did not observe low levels of serum cholesterol, vitamin B12, or folate in the lung cancer patients. 相似文献
9.
Graft copolymers of sodium alginate (NaAlg) with N‐vinyl‐2‐pyrrolidone were prepared using azobisisobutyronitrile as initiator. The graft copolymers (NaAlg‐g‐PVP) were characterized with Fourier transform infrared spectroscopy, elemental analysis, and differential scanning calorimetry. Polymeric hydrogel beads of NaAlg and NaAlg‐g‐PVP were prepared by crosslinking method using glutaraldehyde (GA) as a crosslinker in the hydrochloric acid catalyst (HCl) and these beads were used to deliver anti‐inflammatory drug, indomethacin (IM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. Preparation conditions of the NaAlg‐g‐PVP beads were optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) for 4 h. Effects of GA concentration, exposure time to GA, drug/polymer (d/p) ratio, and concentration of HCl on the release of IM were discussed. It was observed that IM release from the beads decreased with increasing GA concentration and exposure time. IM release also decreases with increasing d/p ratio and HCl concentration. The highest IM release was obtained to be 77% for beads crosslinked with 0.027M GA. Swelling experiments were also performed to compute molecular mass between crosslinks of the beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
10.