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991.
Allen?M.?TesdallEmail author Richard?Sanders Nedyu?Popivanov 《Journal of scientific computing》2015,64(3):721-744
Recent numerical solutions and shock tube experiments have shown the existence of a complex reflection pattern, known as Guderley Mach reflection, which provides a resolution of the von Neumann paradox of weak shock reflection. In this pattern, there is a sequence of tiny supersonic patches, reflected shocks and expansion waves behind the triple point, with a discontinuous transition from supersonic to subsonic flow across a shock at the rear of each supersonic patch. In some experiments, however, and in some numerical computations, a distinctly different structure which has been termed Guderley reflection has been found. In this structure, there appears to be a single expansion fan at the triple point, a single supersonic patch, and a smooth transition from supersonic to subsonic flow at the rear of the patch. In this work, we present numerical solutions of the compressible Euler equations written in self-similar coordinates at a set of parameter values that were used in previous computations which found the simple single patch structure described above. Our solutions are more finely resolved than these previous solutions, and they show that Guderley Mach reflection occurs at this set of parameter values. These solutions lead one to conjecture that the two patterns are not distinct: rather, Guderley reflection is actually underresolved Guderley Mach reflection. 相似文献
992.
Teng Su Ke Huang Hong Ma Hongxia Liang Phuong‐Uyen Dinh Justin Chen Deliang Shen Tyler A. Allen Li Qiao Zhenhua Li Shiqi Hu Jhon Cores Brianna N. Frame Ashlyn T. Young Qi Yin Jiandong Liu Li Qian Thomas G. Caranasos Yevgeny Brudno Frances S. Ligler Ke Cheng 《Advanced functional materials》2019,29(4)
Cardiovascular disease is the leading cause of mortality worldwide. While reperfusion therapy is vital for patient survival post‐heart attack, it also causes further tissue injury, known as myocardial ischemia/reperfusion (I/R) injury in clinical practice. Exploring ways to attenuate I/R injury is of clinical interest for improving post‐ischemic recovery. A platelet‐inspired nanocell (PINC) that incorporates both prostaglandin E2 (PGE2)‐modified platelet membrane and cardiac stromal cell‐secreted factors to target the heart after I/R injury is introduced. By taking advantage of the natural infarct‐homing ability of platelet membrane and the overexpression of PGE2 receptors (EPs) in the pathological cardiac microenvironment after I/R injury, the PINCs can achieve targeted delivery of therapeutic payload to the injured heart. Furthermore, a synergistic treatment efficacy can be achieved by PINC, which combines the paracrine mechanism of cell therapy with the PGE2/EP receptor signaling that is involved in the repair and regeneration of multiple tissues. In a mouse model of myocardial I/R injury, intravenous injection of PINCs results in augmented cardiac function and mitigated heart remodeling, which is accompanied by the increase in cycling cardiomyocytes, activation of endogenous stem/progenitor cells, and promotion of angiogenesis. This approach represents a promising therapeutic delivery platform for treating I/R injury. 相似文献
993.
Howard A. Blair Allen L. Brown Jr. 《Annals of Mathematics and Artificial Intelligence》1990,1(1-4):1-19
For each first-order languageL with a nonempty Herbrand universe, we construct an algebraC interpreting the function symbols ofL that is a model of the Clark equality theory with languageL and is canonical in the sense that for every definite clause programP in the languageL,T
P
C
is the greatest fixed point ofT
P
C
. The universe of individuals inC is a quotient of the set of terms ofL and is, a fortiori, countable ifL is countable. If contains at least one function symbol of arity at least 2, then the graphs of partial recursive functions onC, suitably defined, are representable in a natural way as individuals inC.Research sponsored in part by U.S. Air Force Contract F30602-85-C-0008. 相似文献
994.
NASA multipurpose airborne DIAL system and measurements of ozone and aerosol profiles 总被引:1,自引:0,他引:1
Browell EV Carter AF Shipley ST Allen RJ Butler CF Mayo MN Siviter JH Hall WM 《Applied optics》1983,22(4):522-534
An airborne differential absorption lidar (DIAL) system has been developed for the remote measurement of gas and aerosol profiles in the troposphere and lower stratosphere. The multipurpose DIAL system can operate from 280 to 1064 nm for measurements of ozone, sulfur dioxide, nitrogen dioxide, water vapor, temperature,pressure, and aerosol backscattering. The laser transmitter consists of two narrow linewidth Nd: YAG pumped dye lasers with automatic wavelength control. The DIAL wavelengths are transmitted with a 00-,usec temporal separation to reduce receiver system complexity. A coaxial receiver system is used to collect and optically separate the DIAL and aerosol lidar returns. Photomultiplier tubes detect the backscattered laser returns after optical filtering, and the analog signals from three tubes are digitized and stored on high-speed magnetic tape. Real-time gas concentration profiles or aerosol backscatter distributions are calculated and displayed for experiment control. Operational parameters for the airborne DIAL system are presented for measurements of ozone, water vapor, and aerosols in the 290-, 720-, and 600-nm wavelength regions, respectively. The first ozone profile measurements from an aircraft using the DIAL technique are discussed in this paper. Comparisons between DIAL and in situ ozone measurements show agreement to within +/-5 ppbv in the lower troposphere. Lidar aerosol data obtained simultaneously with DIAL ozone measurements are presented for a flight over Virginia and the Chesapeake Bay. DIAL system performance for profiling ozone in a tropopause folding experiment is evaluated, and the applications of the DIAL system to regional and global-scale tropospheric investigations are discussed. 相似文献
995.
996.
JM Canale DJ Sahn HD Allen SJ Goldberg LM Valdes-Cruz TW Ovitt 《Canadian Metallurgical Quarterly》1981,63(3):689-697
Recent studies suggest good prospective accuracy for two-dimensional echocardiographic imaging of ventricular septal defects (VSD). We obtained two-dimensional images with high-frequency, high-resolution scanners from 36 patients proved by cardiac catheterization to have perimembranous VSD. In 20 patients, the VSD was an isolated lesion and in 16 it was associated with other forms of heart disease. VSDs were imaged in long-axis, apical four-chamber and subcostal echocardiographic views. The smallest VSD imaged was 2 mm in diameter on echo; the largest, 23 mm. The imaged size of VSDs was larger at end-diastole than at end-systole by paired t test on all views (all p less than 0.005). VSD size also varied between views, with no predictive relationship except between apical and subcostal four-chamber views in diastole (r = 0.71, p less than 0.005). This agreed with qualitative direct observations of an ellipsoid or irregularly shaped VSD in operated patients. Echocardiographically measured VSD size normalized for either aortic root size or for patient weight could be used to separate isolated VSDs with large shunts (Qp/Qs greater than 2:1) from those with small shunts. Review of 250 two-dimensional echocardiographic studies from patients proved not to have a VSD revealed 28 planes of imaging with false-positive VSD. None of the false-positive VSDs was imaged consistently on all views. Additionally, a "T" artifact (broadening of septal edges around a VSD) has been found to be a reliable marker of true VSD imaging. To best quantify VSD size and to avoid false-positive diagnoses, it is necessary to use multiple views and to consider the marked changes in VSD size that occur between diastole and systole. 相似文献
997.
998.
A high performance liquid chromatography (HPLC) method for the determination of intact and partially degraded linear alkyl-benzene
sulfonate (LAS) was developed. The LAS degradation products resulting from a semicontinuous activated sludge (SCAS), a die-away
CO2 and a simulated river die-away study were quanti-tatively determined by HPLC equipped with a reversed-phase column using
a tetrahydrofuran/water/Pic A solution as the mobile phase. The column effluent was monitored with a fluorescence spectrophotometer
that was operated at an excitation wavelength of 232 nm and an emission wavelength of 290. Compounds investi-gated included
both single-and mixed-carbon-range materials. The HPLC method shows good correlations with MBAS for intact LAS material. The
most significant advantage of this method over MBAS is it ability to quantitatively determine partially degraded intermediates
and the disappearance of those intermediates. This method, when using the fluorescence detection system, is selective for
sulfonated ring structures with more than one alkyl carbon. The sensitivity of the method is in the 0.05-ppm range. It can
be used not only for samples from laboratory experiments but also for sewage plant influents, effluents and river waters. 相似文献
999.
Allen J. St. Angelo Charles James Jr. 《Journal of the American Oil Chemists' Society》1993,70(12):1245-1250
Lipids were extracted from cooked ground beef with methylene chloride/methanol (2:1). The lipids were separated on a silicic
acid column, into neutral and polar fractions by elution with methylene chloride, followed by methanol. These fractions were
analyzed by Iatroscan thin-layer chromatography with flame-ionization detection instrumentation on Chromarods S-III (silica
gelcoated quartz rods). Comparison of cooked beef stored for 0, 4 and 7 d at 4°C indicated that storage caused a decrease
in total lipids, an increase in neutral lipids and a decrease in polar lipids, specifically in phosphatidylcholine. These
changes in the lipid fraction were associated with meat flavor deterioration and an increase in lipid oxidation. 相似文献
1000.
Anand A. Kulkarni Allen Goland Herbert Herman rew J. Allen Jan Ilavsky Gabrielle G. Long Curtis A. Johnson Jim A. Ruud 《Journal of the American Ceramic Society》2004,87(7):1294-1300
This paper describes the results from multidisciplinary characterization/scattering techniques used for the quantitative characterization of industrial thermal barrier coating (TBC) systems used in advanced gas turbines. While past requirements for TBCs primarily addressed the function of insulation/life extension of the metallic components, new demands necessitate a requirement for spallation resistance/strain tolerance, i.e., prime reliance, on the part of the TBC. In an extensive effort to incorporate these TBCs, a design-of-experiment approach was undertaken to develop tailored coating properties by processing under varied conditions. Efforts focusing on achieving durable/high-performance coatings led to dense vertically cracked (DVC) TBCs, exhibiting quasi-columnar microstructures approximating electron-beam physical-vapor-deposited (EB-PVD) coatings. Quantitative representation of the microstructural features in these vastly different coatings is obtained, in terms of porosity, opening dimensions, orientation, morphologies, and pore size distribution, by means of small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS) studies. Such comprehensive characterization, coupled with elastic modulus and thermal conductivity measurements of the coatings, help establish relationships between microstructure and properties in a systematic manner. 相似文献