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991.
In adipocytes, short and long term stimulation of β adrenergic receptors (βAR) induces the desensitization to catecholamines,
leading to a decrease in the intracellular accumulation of cAMP, but the roles played by this in lipolysis is not clear. In
this study, we assessed the catecholamine-induced desensitization of lipolysis and compared this in adipocytes isolated from
visceral and subcutaneous fat tissues of rats. When adipocytes were pretreated with isoproterenol (ISO), the norepinephrine
(NE)-induced lipolysis was significantly reduced dose- and time-dependently. A similar reduction of the lipolytic response
was also found in NE-, dobutamine-, terbutaline- or BRL37344-induced lipolysis. The ISO- and each βAR agonist-induced lipolysis
in the visceral fat was not only higher than in the subcutaneous fat, but also markedly reduced by ISO- or NE-pretreatment.
These results showed that short-term treatment of three subtypes of βAR by each agonist induces a rapid reduction in the lipolytic
response to βAR stimulation. This suggests some common mechanism for the rapid desensitization of βAR-agonist-induced lipolysis,
in contrast with previous reports on the characteristics of βAR subtypes. In addition, the regional difference of adipose
tissue not only in inducing lipolysis but also in rapid desensitization was also apparent. 相似文献
992.
Brown DJ Orelien J Gordon JD Chu AC Chu MD Nakamura M Handa H Kayama F Denison MS Clark GC 《Environmental science & technology》2007,41(12):4354-4360
Remediation of hazardous waste sites requires efficient and cost-effective methods to assess the extent of contamination by toxic substances including dioxin-like chemicals. Traditionally, dioxin-like contamination has been assessed by gas chromatography/high-resolution mass spectrometry (GC/MS) analysis for specific polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyl congeners. Toxic equivalency factors for these congeners are then used to estimate the overall dioxin toxic equivalency (TEQ) of complex mixtures found in samples. The XDS-CALUX bioassay estimates contamination by dioxin-like chemicals in a sample extract by measuring expression of a sensitive reporter gene in genetically engineered cells. The output of the XDS-CALUX assay is a CALUX-TEQ value, calibrated based on TCDD standards. Soil samples taken from a variety of hazardous waste sites were measured using the XDS-CALUX bioassay and GC/MS. TEQ and CALUX-TEQ from these methods were compared, and a mathematical model was developed describing the relationship between these two data sets: log(TEQ) = 0.654 x log(CALUX-TEQ) + 0.058-(log(CALUX-TEQ))2. Applying this equation to these samples showed that predicted and GC/MS measured TEQ values strongly correlate (R2 = 0.876) and that TEQ values predicted from CALUX-TEQ were on average nearly identical to the GC/MS-TEQ. The ability of XDS-CALUX bioassay data to predict GC/MS-derived TEQ data should make this procedure useful in risk assessment and management decisions. 相似文献
993.
Yamada K Kasai S Nakatani Y Kobayashi K Kohno H Thiaville A Ono T 《Nature materials》2007,6(4):269-263
A magnetic vortex is a curling magnetic structure realized in a ferromagnetic disk, which is a promising candidate for a memory cell for future non-volatile data-storage devices. Thus, an understanding of the stability and dynamical behaviour of the magnetic vortex is a major requirement for developing magnetic data-storage technology. Since the publication of experimental proof for the existence of a nanometre-scale core with out-of-plane magnetization in a magnetic vortex, the dynamics of vortices have been investigated intensively. However, a way to electrically control the core magnetization, which is a key for constructing a vortex-core memory, has been lacking. Here, we demonstrate the electrical switching of the core magnetization by using the current-driven resonant dynamics of the vortex; the core switching is triggered by a strong dynamic field that is produced locally by a rotational core motion at a high speed of several hundred metres per second. Efficient switching of the vortex core without magnetic-field application is achieved owing to resonance. This opens up the potentiality of a simple magnetic disk as a building block for spintronic devices such as a memory cell where the bit data is stored as the direction of the nanometre-scale core magnetization. 相似文献
994.
Takeda S Ozaki H Hattori S Ishii A Kida H Mukasa K 《Journal of nanoscience and nanotechnology》2007,7(3):752-756
Carbon nanotube sensors were capable of detecting hemagglutinin binding to anti-hemagglutinin antibody immobilized on the sensor. The carbon nanotube sensors were fabricated by chemical vapor deposition method and it showed field effect transistor property. Anti-hemagglutinin antibody was immobilized by cross-linking on the reverse surface of the carbon nanotube sensor. The current between the source and the drain was measured after incubation of various concentration of hemagglutinin antigen with immobilized anti-hemagglutinin antibody. I-Vgate curve was obtained by plotting the current as a function of the potential applied to the back gate. The I-Vgate curve showed a positive shift in a manner dependent on the hemagglutinin antigen concentration after immobilization of anti-hemagglutinin while no shift was observed without immobilization of anti-hemagglutinin antibody on the surface. The sensitivity of the CNT sensor was higher than that of the QCM method even without controlling the orientation of the anti-hemagglutinin antibody. This method constitutes a new tool to analyze interactions among biomolecules on a substrate. 相似文献
995.
We conducted the extraction experiments of single polymer incorporated into hydrogels with an atomic force microscope (AFM) as a model for investigating nonspecific intermolecular interactions between macromolecules in a semidilute region at the single molecule level. Small amount of poly(ethylene glycol) (PEG) terminated with a thiol group was inserted in poly(acrylamide) gels, and a part of PEG polymer segments on the gel surface was attempted to pull out of the gels with a gold-coated AFM tip. The observed force-distance curves were classified into two kinds of extraction force profiles: a plateau force, which is almost constant irrespective of the tip-surface distance and a nonlinear force, which nonlinearly increases with the extraction length. Characteristic interaction length, L, and force, F, of these extraction force profiles were measured with changing the crosslinker concentration of gels which strongly affects the network structures. As a result, L of these extraction profiles significantly decreased at crosslinker concentrations higher than a standard one at which most gels have been prepared for investigating their physical properties. On the other hand, F showed no obvious difference on the change in crosslinker concentrations both on the plateau and the nonlinear force profiles. The origin of the observed forces was discussed in terms of gel network structures. 相似文献
996.
While various mineralizing peptides have been applied to grow metal nanoparticles on bionanotube templates, the semiconductor nanoparticle growth on nanotubes has not extensively been explored yet. In this paper, various semiconductor nanocrystals were grown on the bionanotubes surfaces with controlled sizes. When three synthetic peptides, which recognize and selectively bind Ge, Ti, and Cu ions, respectively, were incorporated on template bionanotube surfaces, highly crystalline and monodisperse Ge, TiO2, and Cu2S nanocrystals were grown on the tube surfaces. The sizes of these nanocrystals could be tuned as a function of pH, and larger semiconductor nanocrystals were grown as the pH of growth solutions was increased. All of these nanocrystals from smaller sizes to larger sizes had the same crystallinity. This peptide-controlled nanocrystal growth technique will be very useful to prepare semiconductor nanowires as building blocks for future microelectronics, whose band gaps can be tuned by the sizes of coated semiconductor nanoparticles via their quantum confinement effect. The novelty of this approach in the electronic device fabrication is that the semiconductor nanocrystal size control can be achieved by controlling peptide configurations via pH change, and this control may tune electronic structures and band gaps of the resulting semiconductor nanowires. 相似文献
997.
S.C Sharma B.M Satish B.M Girish Rathnakar Kamath Hiroshi Asanuma 《Tribology International》1998,31(4):183-188
The present investigation aims to evaluate the wear rate of ZA-27 alloy composites reinforced with short glass fibres from 1 to 5% in steps of 2 wt%. The compocasting method was used to fabricate the composites. A pin-on-disc wear testing machine was used to evaluate the wear rate. The results indicated that the wear rate of the composites was less than that of the matrix alloy, but increased with the increase in load and the sliding distance. It was found that above a critical applied load, there exists a transition from mild to severe wear both in the unreinforced alloy and in the composites, but the transition loads for the composites are much higher than that of the unreinforced alloy, and increases with the increase in weight% of glass fibres. The observations have been explained using scanning electron micrography (SEM) analysis of the worn surfaces and the subsurface of the composites. 相似文献
998.
Nakano K. Olariu S. Schwing J.L. 《Parallel and Distributed Systems, IEEE Transactions on》1999,10(12):1276-1289
The main contribution of this work is to present elegant broadcast-efficient protocols for permutation routing, ranking, and sorting on single-hop Mobile Radio Networks with p stations and k radio channels, denoted by MRN(p,k). Clearly, any protocol performing these tasks on n items must perform n/k broadcast rounds because each item must be broadcast at least once. We begin by presenting an optimal off-line permutation routing protocol using n /k broadcast rounds for arbitrary k, p, and n. Further, we show that optimal on-line routing can be performed in n/ k broadcast rounds, provided that either k=1 or p=n. We then go on to develop an online routing protocol that takes 2n/ k+k-1 broadcast rounds on the MRN(p,k), whenever k⩽√p/2. Using these routing protocols as basic building blocks, we develop a ranking protocol that takes 2n /k+o(n/k) broadcast rounds as well as a sorting protocol that takes 3n/k+o(n/k) broadcast rounds, provided that k ϵ o(√n) and p=n. Finally, we develop a ranking protocol that takes 3n/k+o(n/ k) broadcast rounds, as well as a sorting protocol that takes 4n/k+o(n/k) broadcast rounds on the MRN(p,k), provided that k⩽√p/2 and p ϵ o(n). Featuring very low proportionality constants, our protocols offer a vast improvement over the state of the art 相似文献
999.
In the present study we attempt to induce a quadruped robot to walk dynamically on irregular terrain and run on flat terrain by using a nervous system model. For dynamic walking on irregular terrain, we employ a control system involving a neural oscillator network, a stretch reflex and a flexor reflex. Stable dynamic walking when obstructions to swinging legs are present is made possible by the flexor reflex and the crossed extension reflex. A modification of the single driving input to the neural oscillator network makes it possible for the robot to walk up a step. For running on flat terrain, we combine a spring mechanism and the neural oscillator network. It became clear in this study that the matching of two oscillations by the spring-mass system and the neural oscillator network is important in order to keep jumping in a pronk gait. The present study also shows that entrainment between neural oscillators causes the running gait to change from pronk to bound. This finding renders running fairly easy to attain in a bound gait. It must be noticed that the flexible and robust dynamic walking on irregular terrain and the transition of the running gait are realized by the modification of a few parameters in the neural oscillator network. 相似文献
1000.
THE PERSISTENCE OF AIRWAY INFLAMMATION is believed to cause the mechanical changes and symptoms of asthma. After decades of research, a new class of medication has emerged that focuses on leukotrienes, mediators of inflammation. These substances are potent inducers of bronchoconstriction, increased vascular permeability and mucus production, and they potentiate the influx of inflammatory cells in the airways of patients with asthma. In this article the author reviews the development, mechanism of action, and clinical and toxic effects of the leukotriene synthesis inhibitors and receptor antagonists that are entering the North American market. These agents can decrease airway response to antigen, airway hyperresponsiveness and exercise-induced asthma. They are also effective inhibitors of ASA-induced symptoms. Although few published studies are available, the antileukotrienes seem almost as effective in the management of chronic asthma as low-dose inhaled corticosteroids, and their use permits a decrease in the frequency of use or dose of corticosteroids. Further evaluation and clinical experience will determine the position of targeted inhibition of the leukotriene pathway in the treatment of asthma. 相似文献