全文获取类型
收费全文 | 2075篇 |
免费 | 106篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 36篇 |
综合类 | 1篇 |
化学工业 | 463篇 |
金属工艺 | 35篇 |
机械仪表 | 38篇 |
建筑科学 | 80篇 |
矿业工程 | 4篇 |
能源动力 | 52篇 |
轻工业 | 315篇 |
水利工程 | 13篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 182篇 |
一般工业技术 | 348篇 |
冶金工业 | 268篇 |
原子能技术 | 11篇 |
自动化技术 | 337篇 |
出版年
2023年 | 20篇 |
2022年 | 22篇 |
2021年 | 35篇 |
2020年 | 33篇 |
2019年 | 29篇 |
2018年 | 50篇 |
2017年 | 60篇 |
2016年 | 61篇 |
2015年 | 52篇 |
2014年 | 76篇 |
2013年 | 129篇 |
2012年 | 105篇 |
2011年 | 101篇 |
2010年 | 100篇 |
2009年 | 86篇 |
2008年 | 100篇 |
2007年 | 78篇 |
2006年 | 63篇 |
2005年 | 69篇 |
2004年 | 60篇 |
2003年 | 57篇 |
2002年 | 63篇 |
2001年 | 25篇 |
2000年 | 35篇 |
1999年 | 30篇 |
1998年 | 101篇 |
1997年 | 50篇 |
1996年 | 38篇 |
1995年 | 25篇 |
1994年 | 30篇 |
1993年 | 37篇 |
1992年 | 19篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 21篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1977年 | 8篇 |
1912年 | 12篇 |
1909年 | 11篇 |
1907年 | 8篇 |
1906年 | 12篇 |
1905年 | 15篇 |
1904年 | 12篇 |
1902年 | 8篇 |
排序方式: 共有2188条查询结果,搜索用时 0 毫秒
1.
Luc Rochette Loubna Mazini Gabriel Malka Marianne Zeller Yves Cottin Catherine Vergely 《International journal of molecular sciences》2020,21(23)
The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs is a major goal in repair medicine. Stem cells are classified by their potential to differentiate into functional cells. Compared with other sources, adipose-derived stem cells (ADSCs) have the advantage of being abundant and easy to obtain. ADSCs are considered to be tools for replacing, repairing, and regenerating dead or damaged cells. The capacity of ADSCs to maintain their properties depends on the balance of complex signals in their microenvironment. Their properties and the associated outcomes are in part regulated by reactive oxygen species, which mediate the oxidation-reduction state of cells as a secondary messenger. ADSC therapy has demonstrated beneficial effects, suggesting that secreted factors may provide protection. There is evidence that ADSCs secrete a number of cytokines, growth factors, and antioxidant factors into their microenvironment, thus regulating intracellular signaling pathways in neighboring cells. In this review, we introduce the roles of ADSCs in the protection of cells by modulating inflammation and immunity, and we develop their potential therapeutic properties. 相似文献
2.
G. F. Brand 《Journal of Infrared, Millimeter and Terahertz Waves》1996,17(7):1253-1262
The transmission of millimeter waves through a semiconductor changes according to the amount of light falling on it. In the experiments reported here, a pattern of light and shadow is projected onto a sheet of semiconductor and the regions of greater and lesser transmission serve as a diffracting object for a millimeter-wave beam. The light source is a quartz tungsten halogen lamp. A lock-in amplifier is employed to overcome difficulties due to the differences in transmitted power being small. 相似文献
3.
HE Vi?tor F Klumper RJ Meerman A Brand HH Kanhai 《Canadian Metallurgical Quarterly》1998,18(4):325-331
Histamine is an important mediator in allergic reactions, gastric acid secretions, and neurotransmission in the central nervous system. Basophils and mast cells are the main sources of histamine, which is formed from L-histidine by histidine decarboxylase (HDC). However, the regulatory mechanism of HDC in these cells remains unclear. We examined the regulation of HDC activity and gene expression using a unique human mast cell line, HMC-1, after stimulation with phorbol 12-myristate 13-acetate (PMA) or ionomycin. HDC activity was increased from 52.1+/-0.4 (mean+/-standard deviation) to 154+/-6.9, or 105.6+/-6.2 pmol/min/mg protein (n = 3), 4 hours after stimulation with PMA (10 ng/mL) or ionomycin (10[-6] M). Although actinomycin D had no effect on this increase, cycloheximide completely inhibited the increase caused by these stimuli. The population of HMC-1 cells containing HDC protein was increased after stimulation with either PMA or ionomycin as evaluated by immunocytochemical analysis with anti-HDC antibody as a marker. HMC-1 constitutively expressed HDC mRNA, and its level was not increased with these stimuli. These results suggest that the increase of HDC activity in HMC-1 induced by PMA or ionomycin is regulated at the translational level. 相似文献
4.
MJ van den Brand A van Miltenburg MJ de Boer LR van der Wieken PJ de Feyter ML Simoons 《Canadian Metallurgical Quarterly》1994,10(3):177-185
Patients with unstable angina, refractory to intensive medical therapy, are at high risk for developing thrombotic complications, such as recurrent ischemia, myocardial infarction and coronary occlusion during coronary angioplasty. As both platelet aggregation and/or thrombus formation play an important role in this ongoing ischemic process, a monoclonal platelet GPIIb/IIIa receptor antibody (c7E3) or thrombolytic therapy (alteplase) might be able to modify the clinical course and underlying coronary lesion morphology. To evaluate whether alteplase or c7E3 could influence the incidence of complications, we randomized 36 and 60 patients, respectively to alteplase or placebo, or c7E3 or placebo. All patients exhibited dynamic ECG changes and recurrent pain attacks, despite maximal tolerated medical therapy. Patients were randomized in both studies after initial angiography had demonstrated a culprit lesion amenable for angioplasty. After study drug infusion quantitative angiography was repeated and angioplasty performed. Recurrent ischemia during study drug infusion occurred in 5, 6, 9 and 16 patients from the alteplase, placebo, c7E3 and placebo group, respectively. Major events defined as death, myocardial infarction or urgent intervention occurred in 7, 3, 1 and 7 patients, respectively. Two patients died: one in the alteplase group and one in the placebo group from the c7E3 study. The first patient due to retroperitoneal hemorrhage, the second as a result of recurrent infarction. Qualitative angiography showed resolution of clots in the c7E3 group only, while the same group of patients showed in 20% an improvement in TIMI flow grade, without deterioration in any patient from this group.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
C Zwingmann A Brand C Richter-Landsberg D Leibfritz 《Canadian Metallurgical Quarterly》1998,20(4-5):417-426
Glutamine synthesis, the major pathway of ammonia detoxification, and the intracellular concentration of organic osmolytes in primary astrocytes and F98 glioma cells were investigated with multinuclear magnetic resonance spectroscopy. Acute exposure to ammonia (3 h incubation with NH4Cl) raised the concentration of glutamine and other amino acids, such as glutamate and aspartate, and decreased myo-inositol, hypotaurine, and taurine concentrations. The loss of these osmolytes was partially reversed by co-treatment with the glutamine synthetase inhibitor, methionine sulphoximine. Glutamate, the precursor of glutamine, is provided by stimulated anaplerotic flux via pyruvate carboxylase and glutamate dehydrogenase activity. Thus, the glutamine increase and myo-inositol decrease observed by in vivo magnetic resonance spectroscopy on patients with hepatic encephalopathy may be due to the disturbed osmoregulation in astrocytes caused by accumulation of glutamine and the subsequent loss of organic osmolytes. 相似文献
6.
The design, fabrication, and characterization of thermally excited silicon oxide beam and bridge resonators by a modern industrial CMOS process combined with one additional maskless etching step is reported. The resonant frequencies, vibration amplitudes, and mode shapes of the devices are measured using a laser heterodyne interferometer. The acoustic transmitting and receiving sensitivities of the resonant structures in air are investigated in order to test their possible application as ultrasound transducers for proximity sensing. The experimental results are compared with finite element simulations using ANSYS 相似文献
7.
We employed an anatomically realistic three-dimensional finite-element model to explore several biomechanical variables involved in coring or bone-grafting of a segmentally necrotic femoral head. The mechanical efficacy of several variants of these procedures was indexed in terms of their alteration of the stress:strength ratio in at-risk necrotic cancellous bone. For coring alone, the associated structural compromise was generally modest, provided that the tract did not extend near the subchondral plate. Cortical bone-grafting was potentially of great structural benefit for femoral heads in which the graft penetrated deeply into the superocentral or lateral aspect of the lesion, ideally with abutment against the subchondral plate. By contrast, central or lateral grafts that stopped well short of the subchondral plate were contraindicated biomechanically because they caused marked elevations in stress on the necrotic cancellous bone. Calculated levels of stress were relatively insensitive to variations in the diameter of the graft. 相似文献
8.
用声光晶体对氩离子激光作频率调制,获得了碘分子的差拍饱和吸收信号。将得到的斜率极陡的—阶微商形式的饱和吸收信号作为鉴频曲线把氩离子频率激光稳定到~(127)I_2分子的p(13)43—0的a_3超精细分量上。通过与一稳定到相同精细分量的稳频氩离子激光拍频,给出激光频率稳定性优于±6.5×10~(-12),重复性优于±3.4×10~(-11)。 相似文献
9.
10.