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281.
Tzu-Ming Liu Yin-Chieh Huang Gia-Wei Chern Kung-Hsuan Lin Yu-Chueh Hung Chih-Jie Lee Chi-Kuang Sun 《Quantum Electronics, IEEE Journal of》2002,38(11):1529-1535
We present a method to obtain complete information of femtosecond pulses. By measuring triple-optical autocorrelation directly with third-harmonic generation, without spectral information, a temporal pulse shape can be obtained by analytical calculation without direction-of-time ambiguity. Combining the resulting optical pulse shape with its corresponding optical spectrum, the exact phase and color variations in time can all be recovered with a Gerchberg-Saxton algorithm through an iterative calculation with an O(n) complexity. 相似文献
282.
283.
S. Abiraman H. K. Varma T. V. Kumari P. R. Umashankar Annie John 《Bulletin of Materials Science》2002,25(5):419-429
This study investigates quantitatively and qualitatively the sol-gel derived bioactive glass-ceramic system (BGS)—apatite-wollastonite
(AW) type granules in the size range of 0.5–1 mm, as an effective graft material for bone augmentation and restoration. Scanning
electron micrographs (SEM) of the sintered granules revealed the rough material surface with micropores in the range 10–30
μm. X-ray diffraction (XRD) pattern of the granules revealed the presence of crystalline phases of the hydroxyapatite and
wollastonite, and the functional groups of the silicate and phosphates were identified by Fourier transform infrared spectroscopy
(FT-IR). Thein vitro cell culture studies with L929 mouse fibroblast cell line showed very few cells adhered on the BGS disc after 24 h. This
could be due to the highly reactive surface of the disc concomitant with the crystallization but not due to the cytotoxicity
of the material, since the cellular viability (MTT assay) with the material was 80‰ Cytotoxicity and cytocompatibility studies
proved that the material was non-toxic and biocompatible. After 12 weeks of implantation of the BGS granules in the tibia
bone of New Zealand white rabbits, the granules were found to be well osteointegrated, as observed in the radiographs. Angiogram
with barium sulphate and Indian ink after 12 weeks showed the presence of microcapillaries in the vicinity of the implant
site implicating high vascularity. Gross observation of the implant site did not show any inflammation or necrosis. SEM of
the implanted site after 24 weeks revealed good osteointegration of the material with the newly formed bone and host bone.
New bone was also observed within the material, which was degrading. Histological evaluation of the bone healing with the
BGS granules in the tibial defect at all time intervals was without inflammation or fibrous tissue encapsulation. After 2
weeks the new bone was observed as a trabeculae network around the granules, and by 6 weeks the defect was completely closed
with immature woven bone. By 12 weeks mature woven bone was observed, and new immature woven bone was seen within the cracks
of the granules. After 24 weeks the defect was completely healed with lamellar bone and the size of the granules decreased.
Histomorphometrically the area percentage of new bone formed was 67.77% after 12 weeks and 63.37% after 24 weeks. Less bone
formation after 24 weeks was due to an increased implant surface area contributed by the material degradation and active bone
remodeling. The osteostimulative and osteoconductive potential of the BGS granules was established by tetracycline labelling
of the mineralizing areas by 2 and 6 weeks. This sol-gel derived BGS granules proved to be bioactive and resorbable which
in turn encouraged active bone formation. 相似文献
284.
Isothermal Gas Forming of Mg Alloy AZ31 Sheet 总被引:1,自引:0,他引:1
There have been reports on sheet forming of Mg alloy in industry via the punch and die method;this paper is probably the first formal one for studying the sheet formability of AZ31 employing pressurized gas to press the sheet into a female die cavity at various elevated temperatures.The results indicate it is feasible to form a rectangular box via pressurized gas from extruded sheets of 0.5 and 1.7 mm thick.The formed box has 1:2 depth over width ratio,which should be large enough when dealing with realistic industrial sheet forming parts.Presently,forming a sheet of 0.5 mm thick is considered a technical challenge by industry,and it is conquered as demonstrated in this paper.Gas forming technique applied to Mg alloy is unprecedented and shows potential for industrial utilization. 相似文献
285.
286.
Man-Seung Lee 《Metallurgical and Materials Transactions B》2006,37(2):173-179
The ionic equilibria in the mixed ferric and ferrous chloride solution were analyzed by considering the complex formation
reactions as well as the mass and charge balance equations. The activity coefficients of the ions were calculated using the
Bromley equation. The equilibrium constants for the formation of ferrous complexes were determined from the reported thermodynamic
data. The interaction parameters of the ferric species were estimated from the reported values of FeCl3 in an HCl solution. By applying the ionic equilibria, the speciation of the ferric and ferrous species with the composition
was obtained. The predicted pH values of the FeCl3-FeCl2-HCl-H2O system agreed well with the measured values at 25 °C in the ionic strength range of up to 9.34 m. 相似文献
287.
Naturally occurring UV active compounds, commonly present in almost all source waters, can be rapidly monitored by their ultraviolet absorbance at 260 nm (E260). Herein, the extent of correlation between the E260 and the removal efficiency of the hazardous contaminants, endocrine disrupters and dioxins, were investigated using various treatment and river source waters. The detection of various types of hazardous contaminants using sophisticated analytical methods, such as high resolution gas chromatography (HRGC)/high resolution mass spectrometry (HRMS) and high performance liquid chromatography (HPLC)/inductively coupled plasma (ICP)/mass spectrometry (MS), as well as various short-term bioassays, can require hours or even days for results to be obtained. The removal of the E260 correlated well with those of individual contaminants, such as endocrine disruptor chemicals and dioxins, with the various treatment processes employed. In the plots of the endocrine disrupters against the DOC/E260, a correlation was found with the endocrine activity of the Korean/Japanese river waters employed in this study. 相似文献
288.
Muhammad Nabeel Ghayur Anwarul Hassan Gilani 《European Food Research and Technology》2007,224(4):477-481
In this study, we describe the tracheal-relaxant and tocolytic activities of the methanol (ME) and aqueous (AQ) crude extracts
of ginger (rhizome of Zingiber officinale) in an attempt to rationalize its traditional use in disorders of airways and uterine hyperactivity. Both of the ginger extracts
dose-dependently relaxed K+ (80 mM) and carbachol (CCh, 1 μM)-induced contractions with more potency against K+, similar to that elicited by verapamil, a Ca2+ channel blocker. In isolated uterine preparations, the extracts suppressed the K+-induced contractions with respective EC50 values of 0.03 mg/ml (0.02–0.05, 95% CI) and 0.05 mg/ml (0.04–0.06). Activity-directed fractionation of AQ yielded an organic
and an aqueous fraction with the activities concentrated in the former. Both the crude extracts were found safe in mice up
to the oral dose of 5 g/kg when tested for acute toxicity for 24 h. The study shows that ginger possesses tracheal and uterine
smooth muscle relaxant activity, possibility mediated via Ca2+ channel blockade, justifying its use in disorders such as asthma, cough as well as in dysmenorrhoea and uterine and menstrual
spasms and congestion. 相似文献
289.
The deactivation characteristics of Pd/SiO2 in the selective hydrogenation of acetylene were correlated with changes in the amount of the C4 species produced. The amounts of butenes produced changed in parallel with the catalyst activity, indicating that the rate limiting step for butene production was the same as that for acetylene hydrogenation. On the other hand, the amount of 1,3-butadiene produced changed, showing a maximum with catalyst deactivation because 1,3-butadiene is an intermediate in the sequential reaction process which involves both the production and consumption of 1,3-butadiene. This was verified by a simultaneous TG/reaction experiment showing that 1,3-butadiene was a precursor of green oil. The catalyst showed a self-regenerative behavior in its activity and the amounts of C4 species produced during the early stage of deactivation because two opposite factors, which contributed to either the lowering or the promotion of activity, were involved in the process. A specific type of polymer species, produced during the initial period of deactivation, is proposed to be responsible for the promotion of catalyst activity. 相似文献
290.
Tunable blazed gratings 总被引:2,自引:0,他引:2
Xiang Li Antoine C. Daesung Lee Jen-Shiang Wang Solgaard O. 《Journal of microelectromechanical systems》2006,15(3):597-604
In this paper, we report on the design, fabrication, and characterization of blazed gratings made tunable by electrostatic actuation. We combine KOH etching and deep-reactive ion etching (DRIE) to fabricate tunable blazed gratings (TBGs) on silicon-on-insulator wafers with optical-quality mirror surfaces on {111} crystalline planes. The actuators that are used to position the individual grating elements are designed to reduce rotation to levels acceptable for spectroscopic applications. We characterize the fabricated devices mechanically, verify the rotation-reduction design, and demonstrate the functionality of TBGs as tunable filters. 相似文献