全文获取类型
收费全文 | 2471篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 156篇 |
金属工艺 | 21篇 |
机械仪表 | 16篇 |
建筑科学 | 44篇 |
矿业工程 | 5篇 |
能源动力 | 11篇 |
轻工业 | 75篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 176篇 |
一般工业技术 | 225篇 |
冶金工业 | 1612篇 |
原子能技术 | 7篇 |
自动化技术 | 124篇 |
出版年
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 29篇 |
2013年 | 42篇 |
2012年 | 24篇 |
2011年 | 38篇 |
2010年 | 37篇 |
2009年 | 40篇 |
2008年 | 45篇 |
2007年 | 43篇 |
2006年 | 32篇 |
2005年 | 32篇 |
2004年 | 41篇 |
2003年 | 22篇 |
2002年 | 21篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 69篇 |
1998年 | 455篇 |
1997年 | 299篇 |
1996年 | 210篇 |
1995年 | 153篇 |
1994年 | 89篇 |
1993年 | 104篇 |
1992年 | 29篇 |
1991年 | 38篇 |
1990年 | 16篇 |
1989年 | 28篇 |
1988年 | 29篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 22篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1977年 | 59篇 |
1976年 | 117篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1971年 | 6篇 |
1968年 | 7篇 |
排序方式: 共有2492条查询结果,搜索用时 484 毫秒
11.
TonyArmstrong 《世界电子元器件》2004,(7):38-39
许多微处理器和数字信号处理器(DSP)需要一个核心电源和一个在启动期间必须进行排序的输入/输出(I/O)电源。如果未经过适当的电源排序,可能发生闭锁或过流,从而损害微处理器的I/O端口或诸如存储器、逻辑电路、现场可编程门阵列(FPGA)或数据转换器之类支持设备的I/O端口。为了确保在主电源电压未被适当偏置之前I/O负载不被驱动,对核心电源电压和I/O电源电压进行跟踪是必要的。 相似文献
12.
SV Varha OH Reznikov IS Turchyn VM Demchenko OP Potikha PV Sinitsyn LV Tarasenko LV Cha?kovs'ka 《Canadian Metallurgical Quarterly》1994,40(5-6):105-109
The effect exerted by transplantation of the 5 day culture of testicles from newly born piglets on the hypogonadal state of mature X-ray irradiated (3 Gy) rats was studied. It has been found that a month after transplantation (two months after irradiation) the hypogonadal state disappeared for a while, which is confirmed by normalization of the weight of seminal vesicles, content of testosterone and biologically active lutropine, restoration of the reproductive function of rats. No significant changes in steroidogenesis activity have been found, which proves a substituent character of transplantation. The effect disappears three months later but certain restoration of the content of nucleic acids in the testicles is observed. 相似文献
13.
14.
We developed a new in vitro model of neuronal injury using NT2-N cells to examine the effects of hydrodynamic loading rate on intraneuronal calcium dynamics and lactate dehydrogenase (LDH) release. Our apparatus consisted of a parallel disk viscometer which induced fluid shear stress with well-defined magnitudes and loading rates to cultured cells. We found that the deformation response of the cells was dependent on the severity of the insult, with increased cellular strains generated for higher shear stresses at a constant loading rate. Peak intracellular free calcium concentration correlated with strain, suggesting that mechanical deformation may regulate calcium response. Slowly applied fluid shear stress elicited no response, whereas high loading rates resulted in peak calcium increases 2.9 to 3.6 times baseline values as injury severity was increased. LDH release measured within 5 min after the insult correlated with loading rate. In addition, LDH release continued to increase out to 24 h following high loading rate conditions, demonstrating that the application of fluid shear stress led to prolonged cell damage. The acute response in NT2-N cells subjected to an insult with the CSID is dependent on the loading rate, and these results suggest that initial membrane deformation may trigger subsequent events. 相似文献
15.
Hyperphosphorylated tau is the major component of paired helical filaments in neurofibrillary lesions associated with Alzheimer's disease. Hyperphosphorylation reduces the affinity of tau for microtubules and is thought to be a critical event in the pathogenesis of this disease. Recently, glycogen-synthase kinase-3 has been shown to phosphorylate tau in vitro and in non-neuronal cells transfected with tau. The activity of glycogen-synthase kinase-3 can be down-regulated in response to insulin or insulin-like growth factor-1 through the activation of the phosphatidylinositol 3-kinase pathway. We therefore hypothesize that insulin or insulin-like growth factor-1 may affect tau phosphorylation through the inhibition of glycogen-synthase kinase-3 in neurons. Using cultured human neuronal NT2N cells, we demonstrate that glycogen-synthase kinase-3 phosphorylates tau and reduces its affinity for microtubules and that insulin and insulin-like growth factor-1 stimulation reduces tau phosphorylation and promotes tau binding to microtubules. We further demonstrate that these effects of insulin and insulin-like growth factor-1 are mediated through the inhibition of glycogen-synthase kinase-3 via the phosphatidylinositol 3-kinase/protein kinase B signaling pathway. 相似文献
16.
17.
Controlling and diagnostic processes in the bioengineering artificial clearance systems despite of the procedures applied, their functional use and design seem to occur in the artificial organs, each of them consists of controlling and actuating processors ensuring their homogeneous (material, energy-producing, informational) or combined interaction with the patient's body. Centralized control over artificial clearance is proposed by using universal controlling processes which are informationally connected with the operator, the central computer and other controlling processes of the bioengineering system. 相似文献
18.
An extensive study of road traffic accident cases occurring within eastern suburban Calcutta during April 1992 to March 1993 was done. Of which 276 fatal cases having minimum medical aids were taken into consideration to avoid erroneous interpretation. Male pedestrians of age group of 50 years and above were mostly involved during the time period of 5 A.M. to 12 Noon. Fatal Accidents mostly occurred during winter and on the broader roads (Highways) and in majority of cases victims were at fault. 相似文献
19.
VM Coiro AL Segre A Di Nola M Paci A Grottesi G Veglia A Ballio 《Canadian Metallurgical Quarterly》1998,257(2):449-456
Pseudomycin A is a cyclic lipodepsinonapeptide phytotoxin produced by a strain of the plant pathogenic bacterium Pseudomonas syringae. Like other members of this family of bacterial metabolites, it is characterised by a fatty acylated cyclic peptide with mixed chirality and lactonic closure. Several biological activities of Pseudomycin A are lower than those found for some of its congeners, a difference which might depend on the diverse number and distribution of charged residues in the peptide moiety. Hence, it was of interest to investigate its conformation in solution. After the complete interpretation of the two-dimensional NMR spectra, NOE data were obtained and the structure was determined by computer simulations, applying distance geometry and molecular dynamics procedures. The conformation of the large ring of Pseudomycin A in solution includes three rigid structural regions interrupted by three short flexible regions that act as hinges. The overall three-dimensional structure of the cyclic moiety is similar to that of previously studied bioactive lipodepsinonapeptides produced by other pseudomonads. 相似文献
20.
VM Figueredo 《Canadian Metallurgical Quarterly》1996,99(4):207-214
The prognosis for a patient who has survived an acute myocardial infarction depends on three general prognostic factors: (1) residual left ventricular function, (2) remaining viable myocardium at risk (residual ischemia), and (3) presence of substrate for the development of malignant arrhythmias. Multiple clinical and historical factors predict the presence of one or more of these prognostic indicators. Electrocardiographic exercise treadmill testing needs to be done in all patients with uncomplicated infarctions. Guidelines of the American College of Cardiology/American Heart Association Task Force are recommended for risk stratification in most patients after acute myocardial infarction. 相似文献