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991.
992.
The influence of HAF carbon black and BaTiO3 ceramic powder contents in SBR vulcanizates on the dielectric constant (ε′) at different frequencies and at fixed temperature of 303 K is studied well in this article. The temperature dependence of the ac conductivity (σac) was also studied. ε′ appreciably decreases as frequency increased for both filled and unfilled SBR vulcanizates. At each frequency, ε′ gradually decreased with BaTiO3 loading, but its change at any fixed frequency with BaTiO3 filler loading is not uniform. For HAF group ε′ (at loading ≥ 40 phr), drops rapidly with frequency. Meanwhile, it increased appreciably beyond a certain HAF filler loading (≈ 20 phr). Experimental values of the dielectric constant of both BaTiO3 and HAF contents were compared with those calculated by using Tsangaris, Clausius and Bruggman models. Tsangaris model with simple modifications was applied and a fairly good agreement was obtained. The HAF particles or aggregates was found to take the shape of oblate ellipsoids with the minor axes parallel to the applied frequency as detected from the decreasing behavior of the depolarizing factor (Y) with HAF contents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2227–2234, 2007 相似文献
993.
3 取代苯基 5 羟基 5 三氟甲基异口恶唑啉是合成具有异口恶唑结构的原卟啉原氧化酶抑制剂类除草剂的重要中间体。通过以下途径制得4个具有不同取代基的异口恶唑啉中间体:首先,在回流状态,n(甲醇钠)∶n(取代苯乙酮)=2∶1的甲醇钠存在下,取代苯乙酮与三氟乙酸乙酯缩合得到取代苯基 4,4,4 三氟 1,3 丁二酮;后者可在室温下,于二氯甲烷溶剂中,用氯化硫酰氯化,在侧链上引入氯原子;最后,以乙酸作溶剂,回流下,具有不同取代基的苯基 1,3 丁二酮与盐酸羟胺闭环得到产物。反应总收率大于95%。产品结构经质谱、核磁共振氢谱、碳谱确认正确。 相似文献
994.
995.
Nanocomposites of iron oxide (Fe3O4) with a sulfonated polyaniline, poly(aniline‐co‐aminonaphthalenesulfonic acid) [SPAN(ANSA)], were synthesized through chemical oxidative copolymerization of aniline and 5‐amino‐2‐naphthalenesulfonic acid/1‐amino‐5‐naphthalenesulfonic acid in the presence of Fe3O4 nanoparticles. The nanocomposites [Fe3O4/SPAN(ANSA)‐NCs] were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, UV–visible spectroscopy, thermogravimetric analysis (TGA), superconductor quantum interference device (SQUID), and electrical conductivity measurements. The TEM images reveal that nanocrystalline Fe3O4 particles were homogeneously incorporated within the polymer matrix with the sizes in the range of 10–15 nm. XRD pattern reveals that pure Fe3O4 particles are having spinel structure, and nanocomposites are more crystalline in comparison to pristine polymers. Differential thermogravimetric (DTG) curves obtained through TGA informs that polymer chains in the composites have better thermal stability than that of the pristine copolymers. FTIR spectra provide information on the structure of the composites. The conductivity of the nanocomposites (~ 0.5 S cm?1) is higher than that of pristine PANI (~ 10?3 S cm?1). The charge transport behavior of the composites is explained through temperature difference of conductivity. The temperature dependence of conductivity fits with the quasi‐1D variable range hopping (quasi‐1D VRH) model. SQUID analysis reveals that the composites show ferromagnetic behavior at room temperature. The maximum saturation magnetization of the composite is 9.7 emu g?1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
996.
Composite polymer electrolyte based on a new class of filler added to a PEGDME/LiClO4 model system has been investigated. “Ceramic super acids” used consist of grafted SO42− groups on Al2O3 particles surface obtained by calcinations route. Conductivity, DSC and FT-IR measurements performed on such composite electrolytes, when compared to the model PEGDME/LiClO4 electrolyte, showed only slight improvement of their inner characteristics. In contrary, Li/Li symmetric cells study, by means of impedance spectroscopy, has presented a spectacular decrease of the interfacial resistance compare to the model electrolyte. This result opens a new pathway of investigation to master the lithium metal/polymer electrolyte interface. 相似文献
997.
Scott Camazine 《Journal of chemical ecology》1985,11(9):1289-1295
Visual and acoustic cues may serve as aposematic signals that warn predators of poisonous foods. Olfactory aposematism, the use of innocuous odors as warning signals for toxic foods, is another possible means of alerting an animal that a potential food item is unpalatable. Although it has been suggested that olfactory aposematism might be the principle mode of warning utilized by plants in their defense against herbivores, experimental evidence is lacking. This study demonstrates that the opossum,Didelphis virginiana, can utilize an innocuous volatile compound found naturally in a mushroom as a warning signal for a delayed illness caused by mushroom toxin. This supports the contention that characteristic odors of toxic plants may serve a warning function, protecting herbivores from being poisoned and plants from being consumed. 相似文献
998.
999.
A novel perforated bipole trickle-bed electrochemical reactor is investigated for the electro-synthesis of alkaline peroxide.
The process uses a relatively simple cell configuration in which a single electrolyte flows with oxygen gas in a flow-by graphite
felt cathode, sandwiched between a micro-porous diaphragm and a perforated bipolar electrode plate. The graphite felt cathodes
are 120 mm high by 25 mm wide and have a thickness of 3.2 mm. The reactor is operated at current densities in the range 1–5 kA m−2, ca. 800 kPa (abs) pressure and temperature (In/Out) 20–45 °C with one and two-cells. The reactor shows good performance
(current efficiency ∼78% at 2 kA m−2 and a specific energy of 5 kWh per kg of peroxide generated) with peroxide concentrations from 0.02 to 0.15 M in 1 M NaOH. 相似文献
1000.
《Advanced Engineering Informatics》2014,28(4):272-286
Building Information Models (BIM) are comprehensive digital representations of buildings, which provide a large set of information originating from the different disciplines involved in the design, construction and operation processes. Moreover, accessing the data needed for a specific downstream application scenario is a challenging task in large-scale BIM projects. Several researchers recently proposed using formal query languages for specifying the desired information in a concise, well-defined manner. One of the main limitations of the languages introduced so far, however, is the inadequate treatment of geometric information. This is a significant drawback, as buildings are inherently spatial objects and qualitative spatial relationships accordingly play an important role in the analysis and verification of building models. In addition, the filters needed in specific data exchange scenarios for selecting the information required can be built by spatial objects and their relations. The lack of spatial functionality in BIM query languages is filled by the Query Language for Building Information Models (QL4BIM) which provides metric, directional and topological operators for defining filter expressions with qualitative spatial semantics. This paper focuses on the topological operators provided by the language. In particular, it presents a new implementation method based on the boundary representation of the operands which outperforms the previously presented octree-based approaches. The paper discusses the developed algorithms in detail and presents extensive performance tests. 相似文献