全文获取类型
收费全文 | 96655篇 |
免费 | 8270篇 |
国内免费 | 5017篇 |
专业分类
电工技术 | 5601篇 |
技术理论 | 2篇 |
综合类 | 8398篇 |
化学工业 | 15455篇 |
金属工艺 | 5364篇 |
机械仪表 | 5972篇 |
建筑科学 | 6989篇 |
矿业工程 | 2396篇 |
能源动力 | 2657篇 |
轻工业 | 8190篇 |
水利工程 | 1915篇 |
石油天然气 | 4045篇 |
武器工业 | 748篇 |
无线电 | 11394篇 |
一般工业技术 | 10813篇 |
冶金工业 | 4213篇 |
原子能技术 | 1324篇 |
自动化技术 | 14466篇 |
出版年
2024年 | 350篇 |
2023年 | 1271篇 |
2022年 | 2313篇 |
2021年 | 3244篇 |
2020年 | 2564篇 |
2019年 | 2195篇 |
2018年 | 2344篇 |
2017年 | 2769篇 |
2016年 | 2616篇 |
2015年 | 3539篇 |
2014年 | 4610篇 |
2013年 | 5600篇 |
2012年 | 6397篇 |
2011年 | 6907篇 |
2010年 | 6355篇 |
2009年 | 6212篇 |
2008年 | 6145篇 |
2007年 | 5865篇 |
2006年 | 5737篇 |
2005年 | 4980篇 |
2004年 | 3877篇 |
2003年 | 3480篇 |
2002年 | 3965篇 |
2001年 | 3442篇 |
2000年 | 2523篇 |
1999年 | 2066篇 |
1998年 | 1522篇 |
1997年 | 1243篇 |
1996年 | 1211篇 |
1995年 | 1025篇 |
1994年 | 790篇 |
1993年 | 593篇 |
1992年 | 469篇 |
1991年 | 378篇 |
1990年 | 296篇 |
1989年 | 209篇 |
1988年 | 204篇 |
1987年 | 144篇 |
1986年 | 76篇 |
1985年 | 85篇 |
1984年 | 72篇 |
1983年 | 46篇 |
1982年 | 31篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 23篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 20篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
煤气吹扫时惰性气体抑爆用量的优选 总被引:1,自引:0,他引:1
运用惰性气体消防抑爆理论,采用数学积分法计算出吹扫煤气设施时抑爆所需最少惰性气体需要量. 相似文献
52.
Hong Lin H. Nayeb-Hashemi R. M. Pelloux 《Fatigue & Fracture of Engineering Materials & Structures》1993,16(7):723-742
A new multiaxial fatigue damage model for orthotropic materials is proposed based on the strain vector. Six material constants are included in the model. These material constants represent the dependence of fatigue resistance on material orientation, and they can be obtained by conducting strain-controlled uniaxial fatigue tests along the three principal orthotropic directions of an orthotropic material. The model can also be transformed in new coordinate systems to predict the fatigue lives of new material orientations. Biaxial low-cycle fatigue tests are conducted to verify the model. The prediction of the model agrees with the experimental results reasonably well. 相似文献
53.
J. Hong E. S. Lambers C. R. Abernathy S. J. Pearton R. J. Shul W. S. Hobson 《Journal of Electronic Materials》1998,27(3):132-137
Dry etching of InGaP, AlInP, and AlGaP in inductively coupled plasmas (ICP) is reported as a function of plasma chemistry (BCl3 or Cl2, with additives of Ar, N2, or H2), source power, radio frequency chuck power, and pressure. Smooth anisotropic pattern transfer at peak etch rates of 1000–2000Å·min?1 is obtained at low DC self-biases (?100V dc) and pressures (2 mTorr). The etch mechanism is characterized by a trade-off between supplying sufficient active chloride species to the surface to produce a strong chemical enhancement of the etch rate, and the efficient removal of the chlorinated etch products before a thick selvedge layer is formed. Cl2 produces smooth surfaces over a wider range of conditions than does BCl3. 相似文献
54.
Unrecognized and untreated depression occurs frequently in Alzheimer's disease (AD) patients, adding to the agony already experienced by patient and caregiver. The authors screened AD patients living with a family caregiver for depression. Twelve patients with confirmed depression were treated in an open-label study with antidepressant medication, with dosage adjustment by a psychiatrist at Weeks 2, 4, 8, and 16. Data collection occurred at baseline, Week 4, and Week 16. Depression decreased significantly (p < .01). Contrary to expectations, patient functional capacity declined (p = .045). Cognition remained unchanged (p > .05). Caregiver burden, caregiver depressive symptomatology, and quality of life of patient and caregiver remained unchanged (p > .05). The authors conclude that depression in AD can be detected if a collateral source, such as the caregiver, is available. The depression can and should be treated. More research is needed to determine the impact on patient functioning, caregiver burden, caregiver depressive symptomatology, and quality of life of patient and caregiver. 相似文献
55.
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
56.
57.
研究了铁钴钒软磁合金的铁芯损耗,发现铁芯损耗谱具有分形结构。讨论了带材厚度和磁感应强度对分形维数Df的影响。 相似文献
58.
For pt.I see IEEE Trans. Neural Networks, vol.1, p.167-78 (1990). Parallel, self-organizing, hierarchical neural networks (PSHNNs) involve a number of stages with error detection at the end of each stage, i.e., rejection of error-causing vectors, which are then fed into the next stage after a nonlinear transformation. The stages operate in parallel during testing. Statistical properties and the mechanisms of vector rejection of the PSHNN are discussed in comparison to the maximum likelihood method and the backpropagation network. The PSHNN is highly fault tolerant and robust against errors in the weight values due to the adjustment of the error detection bounds to compensate errors in the weight values. These properties are exploited to develop architectures for programmable implementations in which the programmable parts are reduced to on-off or bipolar switching operations for bulk computations and attenuators for pointwise operations 相似文献
59.
Jun-Hee Hong Jong-Keun Park 《Power Systems, IEEE Transactions on》1995,10(4):1789-1797
This paper presents a method of obtaining transmission network equivalents from the network's response to a pulse excitation signal. The proposed method is based on modal decomposition representation for the large-scale interconnected system. In this framework we use Prony analysis to identify the network function of the system and to decompose the large system into a parallel combination of simple first-order systems. As a result the network function of the transmission network can be identified easily, and a Thevenin-type of discrete-time filter model can be generated. It can reproduce the driving-point impedance characteristic of the network. Furthermore, the proposed model can be implemented into the EMTP in a direct manner. The simulation results with the full system representation and the developed equivalent system showed a good agreement 相似文献
60.