首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   336篇
  免费   4篇
  国内免费   1篇
电工技术   2篇
综合类   1篇
化学工业   63篇
金属工艺   16篇
机械仪表   8篇
建筑科学   5篇
能源动力   17篇
轻工业   27篇
无线电   18篇
一般工业技术   47篇
冶金工业   96篇
原子能技术   16篇
自动化技术   25篇
  2023年   1篇
  2022年   4篇
  2021年   8篇
  2020年   2篇
  2019年   2篇
  2018年   4篇
  2017年   3篇
  2016年   3篇
  2015年   1篇
  2014年   7篇
  2013年   12篇
  2012年   23篇
  2011年   15篇
  2010年   24篇
  2009年   16篇
  2008年   8篇
  2007年   9篇
  2006年   15篇
  2005年   10篇
  2004年   9篇
  2003年   6篇
  2002年   5篇
  2001年   13篇
  2000年   3篇
  1999年   11篇
  1998年   36篇
  1997年   19篇
  1996年   15篇
  1995年   13篇
  1994年   2篇
  1993年   6篇
  1992年   3篇
  1991年   4篇
  1990年   3篇
  1989年   1篇
  1988年   5篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1978年   2篇
  1977年   5篇
  1976年   2篇
  1975年   2篇
  1974年   1篇
  1968年   1篇
排序方式: 共有341条查询结果,搜索用时 0 毫秒
91.
ABSTRACT

Three electrical elements (i.e., resistance, capacitance, and relaxation frequency) of electrical double layer (EDL) formed around particles have been extracted by a measuring–fitting combination for a novel noninvasive online measurement technique of particle size and concentration in a liquid–particle mixture. The measuring–fitting combination means measuring the impedances with electrical-impedance spectroscopy (EIS) method, and fitting the equivalent circuit with Levenberg–Marquardt method. The liquid–particle mixture in the impedance measurement is made of sodium chloride solution and stainless particles; the equivalent circuit is established corresponding to the contents in the liquid–particle mixture. As a result, the influence of the particle size and concentration on the electrical elements in the EDL which are the resistance, capacitance, and relaxation frequency in the EDL are clarified and discussed. This method is useful for determination of the particle size and concentration in liquid–particle mixture.  相似文献   
92.
Dextromethorphan (DEM)-mediated N-methyl-D-aspartate receptor blockade may result from an action of unchanged DEM or its active metabolite, dextrorphan (DOR). In humans, DEM is metabolized into DOR by the polymorphic enzyme CYP2D6. We therefore investigated the impact of quinidine (Qd), a selective inhibitor of CYP2D6, on DEM disposition and the contribution of CYP2D6 phenotype on DEM antinociceptive and neuromodulatory effects. Using a randomized, double-blind, crossover, placebo-controlled design, healthy volunteers (n = 7) received Qd (50 mg Qd sulfate orally) or a placebo and, 12 h later, either DEM (50 mg DEM hydrobromide orally) or a placebo. DEM and DOR pharmacodynamics were assessed for their antinociceptive and neuromodulatory effects. Antinociceptive effects were assessed over 4 h by subjective pain threshold and RIII nociceptive reflex (RIII) monitoring. Neuromodulatory effects were studied using the primary and secondary hyperalgesia induced by the topical application of capsaicin. Two of seven subjects were genotypic CYP2D6 PM. Pretreatment of EM by Qd suppressed DOR formation and increased the plasma level of DEM to the levels of poor metabolizers. In poor metabolizers, DEM induced a significant increase in objective (+45%) and subjective (+35%) pain thresholds. In extensive metabolizers, only a slight and short-lasting increase in the subjective threshold was observed, whereas no effect was seen on the objective threshold. DEM modulates secondary hyperalgesia compared with DOR. The CYP2D6 phenotype affects the disposition of DEM and the production of the active metabolite DOR. The impact of the CYP2D6 phenotype is of major importance for the spinal antinociceptive and neuromodulatory effects of DEM.  相似文献   
93.
The effect of sodium citrate (Na-citrate) on myosin and actin denaturation in myofibrils was investigated. Na-citrate significantly suppressed the thermal inactivation of Ca2+-ATPase of carp myosin in a concentration-dependent manner. The effect was greater than that of sorbitol. A similar effect was observed with myofibrils in which myosin is stabilized by F-actin binding. Na-citrate dissolved myofibrils at lower concentration than NaCl. Nevertheless, Na-citrate at 1 M failed to denature F-actin in myofibrils, while 1 M NaCl denatured F-actin almost completely. Na-citrate suppressed the NaCl-induced F-actin denaturation. Sorbitol did not show such protective effect on F-actin denaturation. Moreover, Na-citrate suppressed the freeze denaturation of myofibrils at lower concentration than sorbitol. Thus, Na-citrate was proved to be superior to sorbitol. It was suggested that Na-citrate alone could substitute sorbitol as cryoprotectant in surimi and NaCl as dissolving reagent of myofibril in thermal gel production.  相似文献   
94.
Konno S  Kojima T  Fujikawa S  Yasui K 《Applied optics》2002,41(36):7569-7572
A novel configuration for a multirod solid-state laser system is proposed. We stabilize the thermal-lens-dependent variation in the output-beam parameters by extracting the laser beam from the collimating point of periodic beam propagation. The performance is confirmed with a 100-W class diode-pumped Nd:YAG laser-amplifier system to demonstrate tenfold stabilization of the output-beam diameter.  相似文献   
95.
This letter treats the quantum random walk on the line determined by a 2 × 2 unitary matrix U. A combinatorial expression for the mth moment of the quantum random walk is presented by using 4 matrices, P, Q, R and S given by U. The dependence of the mth moment on U and initial qubit state is clarified. A new type of limit theorems for the quantum walk is given. Furthermore necessary and sufficient conditions for symmetry of distribution for the quantum walk is presented. Our results show that the behavior of quantum random walk is striking different from that of the classical ramdom walk. PACS: 03.67.Lx; 05.40.Fb; 02.50.Cw  相似文献   
96.
采用液-液界面沉积法,以甲苯和丙胺为溶剂,合成C_(60)-C_(70)富勒烯针状晶体固溶体。使用聚焦离子束扫描电子显微镜来测试其力学性能,C_(60)-C_(70)富勒烯针状晶体的拉伸强度为58~71 MPa,断裂韧性为1.1~1.3 MPa m~(1/2)。C_(60)-C_(70)富勒烯针状晶体拉伸强度显著高于C_(60)富勒烯针状晶体,其比强度略大于铝。通过富勒烯分子溶剂化可能改变C_(60)-C_(70)富勒烯针状晶体的塑性和断裂韧性。C_(60)-C_(70)富勒烯针状晶体有望用作电极、锚杆及电动给料机线等材料。  相似文献   
97.
Abedin KS  Haidar S  Konno Y  Takyu C  Ito H 《Applied optics》1998,37(9):1642-1646
Mid-infrared radiation in the 5-18-mum range has been obtained by difference frequency generation in a AgGaSe(2) crystal by pumping with the output of a type I LiNbO(3) optical parametric oscillator (OPO). Here we suggest the use of a LiTaO(3) retarder to achieve an orthogonal state of polarization between OPO outputs that are necessary for efficient pumping of a AgGaSe(2) crystal. Several tens of kilowatts of peak power near 8 mum and continuously tunable operation in the above range have been obtained.  相似文献   
98.
In this paper, analytic singularity analysis of a 4-DOF parallel robot H4 is addressed. Since a parallel manipulator consisting of several serial chains has complex singularities in the workspace, the determination of singular configurations is very important in design, trajectory planning, and control. The classical method to determine singular configurations is to find the determinant of the Jacobian matrix. However, the Jacobian matrix of a parallel manipulator is complex in general and thus it is not easy to find the determinant of the Jacobian matrix. Therefore, we focus on the analytic singularity analysis of a 4-DOF parallel robot H4 using Jacobian deficiencies. A subset of the whole singularities and the intuitively predictable ones are only derived using Jacobian matrix deficiency. Three type singularities, i.e., overmobility, undermobility and combined singularities, have been presented.  相似文献   
99.
Febrile Infection-Related Epilepsy Syndrome (FIRES) is a unique catastrophic epilepsy syndrome, and the development of drug-resistant epilepsy (DRE) is inevitable. Recently, anakinra, an interleukin-1 receptor antagonist (IL-1RA), has been increasingly used to treat DRE due to its potent anticonvulsant activity. We here summarized its effects in 38 patients (32 patients with FIRES and six with DRE). Of the 22 patients with FIRES, 16 (73%) had at least short-term seizure control 1 week after starting anakinra, while the remaining six suspected anakinra-refractory cases were male and had poor prognoses. Due to the small sample size, an explanation for anakinra refractoriness was not evident. In all DRE patients, seizures disappeared or improved, and cognitive function improved in five of the six patients following treatment. Patients showed no serious side effects, although drug reactions with eosinophilia and systemic symptoms, cytopenia, and infections were observed. Thus, anakinra has led to a marked improvement in some cases, and functional deficiency of IL-1RA was indicated, supporting a direct mechanism for its therapeutic effect. This review first discusses the effectiveness of anakinra for intractable epileptic syndromes. Anakinra could become a new tool for intractable epilepsy treatment. However, it does not currently have a solid evidence base.  相似文献   
100.
Compact oxide films were formed on aluminium in a neutral borate solution (pH 7.4, 20°C) by applying a constant potential of 50 V (SCE), and then immersed in distilled water, a 0.001 mol dm?3 chromate solution (pH 7.0), or a 0.001 mol dm?3 phosphate solution (pH 7.0). Changes in the composition profile of the oxide caused by the immersion were examined by X-ray photo-electron spectroscopy (XPS) combined with a film sectioning technique. After a 72 h immersion in distilled water, the OH? content in the outer part of the film increased to about three times as that before immersion, and the film sustained only 30 V instead of the initial 50 V. As the profile of BO2? ions remained unchanged, the deterioration of the film is exclusively due to hydration of the oxide caused by the penetration of water molecules or OH? ions into the oxide lattice. It was found that the hydration is strongly inhibited by chromate and phosphate. XPS and chemical analysis showed that CrO42? and PO43? ions adsorb on the oxide surface to form a mono- or bi-layer, hindering the penetration of water molecules. The inhibiting behaviour, stabilizing oxide films, is important in explaining the function of these anions as corrosion inhibitors for metals in near neutral solutions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号