全文获取类型
收费全文 | 9941篇 |
免费 | 69篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 62篇 |
综合类 | 2篇 |
化学工业 | 586篇 |
金属工艺 | 58篇 |
机械仪表 | 59篇 |
建筑科学 | 78篇 |
矿业工程 | 29篇 |
能源动力 | 44篇 |
轻工业 | 311篇 |
水利工程 | 20篇 |
石油天然气 | 11篇 |
无线电 | 537篇 |
一般工业技术 | 454篇 |
冶金工业 | 7328篇 |
原子能技术 | 35篇 |
自动化技术 | 397篇 |
出版年
2021年 | 27篇 |
2020年 | 21篇 |
2018年 | 39篇 |
2017年 | 29篇 |
2016年 | 20篇 |
2015年 | 25篇 |
2014年 | 43篇 |
2013年 | 207篇 |
2012年 | 76篇 |
2011年 | 105篇 |
2010年 | 73篇 |
2009年 | 102篇 |
2008年 | 110篇 |
2007年 | 127篇 |
2006年 | 113篇 |
2005年 | 96篇 |
2004年 | 89篇 |
2003年 | 100篇 |
2002年 | 68篇 |
2001年 | 78篇 |
2000年 | 66篇 |
1999年 | 273篇 |
1998年 | 2296篇 |
1997年 | 1318篇 |
1996年 | 852篇 |
1995年 | 478篇 |
1994年 | 423篇 |
1993年 | 479篇 |
1992年 | 101篇 |
1991年 | 156篇 |
1990年 | 123篇 |
1989年 | 119篇 |
1988年 | 127篇 |
1987年 | 111篇 |
1986年 | 104篇 |
1985年 | 100篇 |
1984年 | 36篇 |
1983年 | 54篇 |
1982年 | 76篇 |
1981年 | 86篇 |
1980年 | 76篇 |
1979年 | 36篇 |
1978年 | 43篇 |
1977年 | 212篇 |
1976年 | 364篇 |
1975年 | 53篇 |
1974年 | 18篇 |
1973年 | 23篇 |
1972年 | 29篇 |
1966年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Jeong-Soo Lee Yang-Kyu Choi Daewon Ha Balasubramanian S. Tsu-Jae King Bokor J. 《Electron Device Letters, IEEE》2003,24(3):186-188
The hydrogen annealing process has been used to improve surface roughness of the Si-fin in CMOS FinFETs for the first time. Hydrogen annealing was performed after Si-fin etch and before gate oxidation. As a result, increased saturation current with a lowered threshold voltage and a decreased low-frequency noise level over the entire range of drain current have been attained. The low-frequency noise characteristics indicate that the oxide trap density is reduced by a factor of 3 due to annealing. These results suggest that hydrogen annealing is very effective for improving device performance and for attaining a high-quality surface of the etched Si-fin. 相似文献
2.
S Schaefer H Hussein GR Gershony JC Rutledge CT Kappagoda 《Canadian Metallurgical Quarterly》1997,45(9):536-541
BACKGROUND: Intensive risk factor reduction in patients with dyslipidemias and coronary atherosclerosis has been shown to result in alterations in coronary artery morphology and reduced clinical events. However, the impact of such interventions in populations with relatively normal levels of low-density lipoproteins (LDL) is unclear. METHODS: To test the hypothesis that intensive risk factor reduction results in angiographic regression in patients with only mildly elevated levels of LDL, 14 patients with angiographically proven coronary atherosclerosis were entered into the University of California Davis Coronary Artery Disease Regression Program and intensively treated with pharmacologic and nonpharmacologic interventions for 2 years. Quantitative angiography was performed prior to and after 2 years of therapy to determine changes in coronary artery diameter. RESULTS: As a result of this program, dietary fat intake was reduced by 58% and LDL fell from 120 +/- 7 mg/dL to 104 +/- 6 mg/dL (p = 0.05). The average diameter of the measured arterial locations (including all 53 stenoses and 292 nondiscrete regions) on study entry was 2.74 +/- 0.05 mm. After 24 months, there was a net increase in arterial diameter (regression) of +0.05 +/- 0.04 mm to 2.81 +/- 0.05 mm (p = 0.01). While there was no significant change in the average diameter of discrete stenoses, all 8 lesions > or = 50% initial diameter narrowing regressed, with a mean diameter change of + 0.2 mm. Conversely, only 1 of 8 mild lesions < or = 20% regressed, while 4 progressed. Intermediate lesions (20% to 50%, n = 37) had balanced progression and regression. CONCLUSIONS: When examined as a continuous variable, there was a significant linear correlation between initial lesion severity (% stenosis) and the extent of regression (mm). Therefore, risk factor reduction (dietary therapy, exercise, psycho-social counseling, and lipid lowering therapy) in patients with only mild dyslipidemia results in angiographic regression of more severe lesions (> 50% initial stenosis), but does not prevent progression of mild lesions (< 20%). These findings demonstrate that intensive risk factor reduction in patients with only mild elevation of lipids beneficially influences the morphology of the most severe lesions. 相似文献
3.
B Amblard C Assaiante JC Fabre L Mouchnino J Massion 《Canadian Metallurgical Quarterly》1997,114(2):214-225
The ability voluntarily to stabilize the head in space during lateral rhythmic oscillations (0.59+/-0.09 Hz) of the trunk has been investigated during microgravity (microG) and normal gravity (nG) conditions (parabolic flights). Five healthy young subjects, who gave informed consent, were examined. The movements were performed with eyes open or eyes closed, during phases of either microG or nG. The main result was that head orientation with respect to vertical may be stabilized about the roll axis under microG with, as well as without vision, despite the reduction in vestibular afferent and muscle proprioceptive inputs. Moreover, the absence of head stabilization about the yaw axis confirms that the degrees of freedom of the neck can be independently controlled, as was previously reported. These results seem to indicate that voluntary head stabilization does not depend crucially upon static vestibular afferents. Head stabilization in space may in fact be organized on the basis of either dynamic vestibular afferents or a short-term memorized postural body schema. 相似文献
4.
5.
JC Métraux 《Canadian Metallurgical Quarterly》1997,117(5):419-423
The purpose of this study was to assess cortical and cancellous bone responses to unilateral limb immobilization and, subsequently, to remobilization with exercise, in a young adult canine model. Right forelimbs of 14 1-2-year old mongrel dogs were immobilized in a non-weight-bearing position by a bandage for 16 weeks. Six control dogs were untreated. At 16 weeks, seven immobilized and three control dogs were euthanized. The remaining seven immobilized dogs began a recovery protocol consisting of 16 weeks of kennel confinement (without the right forelimb bandaged) followed by 16 weeks of treadmill exercise conducted three times per week. These seven dogs and three control dogs were euthanized at 48 weeks. Bone mineral density of the proximal radii was determined with dual-energy X-ray absorptiometry and humeral middiaphyseal cross-sectional areas were determined with computed tomography. Humeri were tested in cranio-caudal three-point bending to failure. Cancellous bone cores from the lateral humeral condyles had wet apparent density determined and were tested to failure in compression. Mechanical properties, bone density, and cross-sectional areas were compared between immobilized (right forelimb), contralateral weight bearing (left forelimb), and control forelimbs with Kruskal-Wallis and post hoc tests. At 16 weeks, bone mineral density, cortical load, yield, and stiffness as well as cancellous bone failure stress, yield stress, and modulus were significantly lower (p < 0.02) for immobilized limbs than control limbs. Immobilized limb cancellous bone mechanical properties were 28%-74% of control values, and cortical bone mechanical properties were 71%-98% of control values. After 32 weeks of remobilization, cortical and cancellous bone mechanical properties were not different from control values except that cortical bone failure stress and modulus were significantly higher (p < 0.01) between remobilized and control limbs. In summary, 16 weeks of forelimb immobilization was associated with significantly lower mechanical properties, and with greater differences in cancellous than cortical bone properties. Mechanical properties were not different from control values after 32 weeks of recovery that included 16 weeks of treadmill exercise. 相似文献
6.
7.
A Gopal G Li Mandri DL King C Marboe S Homma 《Canadian Metallurgical Quarterly》1994,105(6):1885-1887
Cardiac papillary fibroelastomas are unusual, frond-like growths typically found on cardiac valves, diagnosed incidentally on autopsy or cardiac surgery, but rarely during life. We report a rare case of an aortic valve papillary fibroelastoma detected by transthoracic echocardiography and confirmed by histologic study. 相似文献
8.
9.
10.
D. M. Van Wie D. G. Drewry Jr. D. E. King C. M. Hudson 《Journal of Materials Science》2004,39(19):5915-5924
Hypersonic flight powered by airbreathing engines offers the potential for faster response time at long ranges, and reduced cost for access-to-space. In the present paper the operating environment of typical hypersonic vehicles are discussed, including results for the radiation equilibrium wall temperature of external vehicle surfaces and the flow properties through three sample engines spanning the range of hydrocarbon-fueled Mach 4-8 flight and hydrogen-fueled flight at speeds up to Mach 17. Flow conditions at several locations through the sample engines were calculated to provide indications of the required operating flow environment. Additional system consideration such a seals, joints, vehicle integration and in-service engineering are addressed. 相似文献