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991.
目的研究3种不同方法对经皮肝脏穿刺诊疗所致肝内穿刺腔道出血的止血效果。方法根据诊疗方法及穿刺道大小对51例经皮肝穿刺诊疗患者采用3种不同方法行穿刺道止血,其中单纯以明胶海绵条栓塞止血15例(A组),明胶海绵栓塞加注射用血凝酶(巴曲酶)腔道内注射联合止血17例(B组),单纯以血凝酶针道注射止血19例(C组)。比较分析不同方法对穿刺道的闭塞效果及止血效果。结果A组栓塞后有6例未完全闭塞(6/15),术后有2例出现肝包膜下小血肿(2/15),未见腹腔内积血;B组与C组腔道完全闭塞率100%,术后无一例出血。术后穿刺道闭塞率及出血发生率三组比较,B、C两组明显优于A组。所有病例术后均未发生胆汁性腹膜炎。结论单纯血凝酶针道内注射对细小针道有良好而彻底的闭塞作用;明胶海绵栓塞加血凝酶注射对较大的穿刺道具有可靠而彻底的封闭作用,因此对于较大的穿刺道应以明胶海绵栓塞加血凝酶腔道内注射以彻底封闭穿刺道为最佳止血方法  相似文献   
992.
Abuse of market power by dominant generation firms is a growing concern in worldwide electricity markets. This paper argues that relying only on general competition rules—as is the case in most European countries—is insufficient and that complementary ex-ante regulation is needed. In particular, regulators should incentivize firms to sign contracts with retailers by regulating their risk exposure. In a simulation model we show that this type of regulation can significantly reduce the deadweight loss in the market, without imposing large costs on regulatees.  相似文献   
993.
We present an analysis of linear in-band crosstalk in high split long reach wavelength/time-division-multiplexing passive optical networks (WDM-TDM PONs). In this letter, a mathematical model is deducted for the first time to calculate optical signal-to-noise ratio penalties due to in-band crosstalk in multipoint-to-point networks. The network performance can be perturbed by in-band crosstalk caused by power leakages from burst-mode optical network units (ONUs) in off-state. Our study results show that the leaked powers in upstream ONU transmitters can have an impact on the achievable split factor of WDM-TDM PONs. Furthermore, the performance limitations caused by aggregated interburst residual power are discussed.  相似文献   
994.
It is shown that the high density of threading dislocations (TDs) and, more specifically, the high density of point defects associated with it and present in our strained Ge epitaxial layers on a Si0.2Ge0.8 relaxed buffer layer degrades the mobility and the leakage current of pMOSFETs and p+n junctions fabricated therein. Annealing in the range 550–650 °C prior to gate stack deposition improves the device performance, although there is no marked change in the TD density. From this, it is concluded that the annealing may reduce the density of point defects grown in during the epitaxial deposition.  相似文献   
995.
传输/反射法测量复介电常数的若干问题   总被引:3,自引:3,他引:3  
研究了传输/反射法测量线性材料复介电常数εr的厚度谐振、多值性等问题,得到了解决这些问题的有效方法。通过改进NRW传输/反射法,由散射参数直接得到了归一化特性阻抗与传播常数,从而可以把已有的三个确定复介电常数的方程用到NRW传输/反射法中。联合应用这三个方程解决了上述问题,这使得人们可以用传输/反射法对任意厚度的样品在任意频率上进行复介电常数的稳定测量。用波导取样器与同轴线取样器分别得到的实验结果证明了此方法的有效性与可实现性。  相似文献   
996.
Polyelectrolyte microcapsules are made by layer‐by‐layer (LbL) coating of a sacrificial template, followed by decomposition of the template, to produce hollow microcapsules. In this paper, we report on the in vivo cellular uptake, degradation and biocompatibility of polyelectrolyte microcapsules produced from alternating dextran sulphate and poly‐L‐arginine layers on a template of calcium carbonate microparticles. We show that a moderate tissue reaction is observed after subcutaneous injection of polyelectrolyte microcapsules in mice. Within sixteen days after subcutaneous injection, most of the microcapsules are internalized by the cells and start to get degraded. The number of polyelectrolyte layers determines the stability of the microcapsules after cellular uptake.  相似文献   
997.
Polymeric (PMMA) ultrahydrophobic surfaces with contact angles up to about 170° have been fabricated and used in the context of synchrotron radiation experiments on biological droplets. The different microfabrication processes included either an optical lithography phase followed by a plasma texturing one or a single step deep reactive ion etch attack.The drying of several biological solution droplets has been monitored. Room temperature evaporation experiments (lysozyme, lactalbumin, cytochrome C, doxorubicin and synthesized peptides) finally result in the formation of easily detachable hollow residuals because of the low interaction between the ultrahydrophobic substrate and the aqueous droplet while pilot experiments (bovine insulin) in a sitting-drop environment bring to the formation of well defined crystals. Recent results about in situ X-ray diffraction experiments by SAXS & WAXS (Small and Wide Angle X-ray Scattering) μ-beam techniques confirm that the presence of such surfaces influences the formation of crystal or fibril structures. These substrates represent indeed a suitable support to study biological and inorganic droplets in a near contact-free environment exploiting the homogeneous evaporation rate induced by the ultrahydrophobicity of the system.  相似文献   
998.
In this paper, novel CMOS pseudo‐exponential circuits operating in a class‐AB mode are presented. The pseudo‐exponential approximation employed is based on second order equations. Such terms are derived in a straightforward way from the inherent nonlinear currents of class‐AB transconductors. The cells are appropriate to be integrated in portable equipment due to their compactness and very low power consumption. Measurement results from a fabricated prototype in a 0.5 μm technology reveal a range of 45 dB with errors lower than ±0.5 dB, a power consumption of 100 μW, and an area of 0.01 mm2.  相似文献   
999.
燃煤飞灰的显微颗粒类型与显微结构特征   总被引:8,自引:1,他引:8  
利用光学显微镜和扫描电子显微镜对不同燃煤煤种和锅炉类型电厂飞灰进行观察研究,建立了燃煤飞灰微颗粒的系统分类方案,并揭示出各类颗粒的显微结构特征,首先根据物质成分将飞灰分出硅铝质,铁质,钙质和炭粒4个组,然后根据微观形貌和内部结构分出16种显微颗粒类型。研究发现空心微珠和子母珠是飞灰中普遍存在的显微颗粒类型,不仅广泛分布于不同粒级的硅铝质颗粒中,而且常见于钙质和铁质颗粒中,发现并命名了多孔微珠这一新的显微颗粒类型;在多种颗粒中广泛分布的次级细小灰球的发现,为飞灰显微结构的成因研究提供了科学依据。  相似文献   
1000.
We investigate Co silicide phase formation when extra Si is added within an as deposited 50 nm Co film. The addition of Si is investigated for both the Co/SiO2 and Co/Si(1 0 0) system. A series of 10 Co-Si mixed films with a Si content varying from 21 to 59 at.% was prepared and investigated during annealing with in situ X-ray diffraction. The oxide system is used as reference system to identify phases that initially crystallize in an amorphous mixture of a given composition. Multiple phases can nucleate, and the temperature of crystallization depends on the Co-Si atomic ratio. Upon heating of the Co(Si)/Si system, the first reaction is a similar crystallization reaction of the Co(Si) mixture. Once the first phase is formed, one has the normal system of a silicide phase in contact with an unlimited amount of Si from the substrate, and the sequential phase formation towards CoSi2 is established. For deposited layers of composition ranging from 48%Si to 52%Si, the CoSi is the first phase to form and increasing the amount of Si leads to a remarkable improvement of the thermal stability of CoSi on Si(1 0 0). CoSi2 nucleation was extensively delayed by 150 °C compared to the reaction observed from a pure Co film on Si(1 0 0). Electron backscatter diffraction measurements reveal that in this range, the gradual Si increase systematically leads to bigger CoSi grains (up to 20 μm). This shows that the grain size of the CoSi precursor strongly affects the nucleation of the following CoSi2 phase. Laser-light scattering measurements suggest that adding more than 42%Si reduces the roughness of the CoSi2 layer.  相似文献   
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