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81.
William D. Keat Michael C. Larson Melody Arthur Verges 《International Journal of Fracture》1998,92(3):253-286
A procedure is presented which is well suited for three-dimensional subsurface crack identification in a half-space through
the inversion of measured surface displacements. The investigation began with the linear, forward problem of generating contour
maps of surface deformation produced by a fracture of known geometry and loading which is embedded in a finite medium. The
fundamental solutions for tensile and shear multipoles in a half-space provided an efficient mathematical representation of
the three-dimensional fracture. The inverse problem of crack identification centers on the development of a hybrid of the
Marquardt–Levenberg algorithm. Initial guesses for the constrained set of search variables were determined heuristically from
the correspondences between crack geometry and loading and the resulting uplift at the free surface. Physical measurements
of surface deformation were taken for a cube of transparent acrylic polyester in which a fracture was hydraulically pressurized.
Displacements induced at the surface of the specimen, which were measured by laser interferometry, had a strong correlation
with predictions of the computational model (coupled with a finite element discretization). Numerical tests demonstrate the
robustness of the inverse methodology even in the presence of the random and systematic errors corresponding to the experimental
interferometric measurements.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
82.
The predominant early childhood education philosophy in the United States views formal academic instruction as inappropriate and harmful to the social development of young children. Chinese American immigrants to the United States, however, have been found to teach their young children in more formal ways, to be more directive, and to structure their children's use of time to a greater degree (C. S. Huntsinger, P. E. Jose, F.-R. Liaw, & W.-D. Ching, 1997). Forty European American (20 boys, 20 girls) and 36 2nd-generation Chinese American (18 boys, 18 girls) 1st- and 2nd-grade children and their mothers, fathers, and teachers participated in the Time 2 data collection of this longitudinal study to assess whether the formal academic environment provided by Chinese American parents is linked to poorer social adjustment in their children. Regressions showed that parents' work-oriented methods influenced academic performance but not social adjustment of their children. 相似文献
83.
RA Rosenblatt AJ Dawson EH Larson CJ Tressler A Jones LG Hart TS Nesbitt 《Canadian Metallurgical Quarterly》1995,11(3):571-584
The purpose of this study was to examine differences in the way Britain and the United States invest in and deploy a new medical technology. We used structured interviews to obtain information on the technical sophistication and approximate replacement value of all hospital-based obstetrical ultrasound machines in every maternity hospital in Washington state and Wales. The supply of hospital-based ultrasound machines--approximately two machines per 1,000 births--was similar in both countries. Wales had fewer advanced ultrasound machines than Washington state, and they were based exclusively in high-volume district general hospitals; there were no obstetric ultrasound machines in the private sector. In Washington state, the majority of advanced machines were in small and medium-sized hospitals, and many private offices had ultrasound machines. The approximate replacement value of hospital-based machines was three times as high per birth in Washington state as in Wales. In the case of obstetrical ultrasound, centralization of facilities, a relatively small private sector, and global budgeting lead to lower expenditures per patient within the National Health Service without compromising access to care. 相似文献
84.
Microelectromechanical wavelength tuning is demonstrated for the first time in a resonant-cavity light-emitting diode. The device utilizes a deformable-membrane top mirror suspended by an air gap above a diode-active region and bottom mirror. Applied membrane-substrate bias produces an electrostatic force which reduces the air-gap thickness, and therefore, the resonant wavelength. We report broad tunability of nearly 40 nm and spectral linewidths as narrow as 1.9 nm (2.6 meV) for operation near 950 nm 相似文献
85.
Fritze M. Chen C.L. Calawa S. Yost D. Wheeler B. Wyatt P. Keast C.L. Snyder J. Larson J. 《Electron Device Letters, IEEE》2004,25(4):220-222
High-speed results on sub-30-nm gate length pMOSFETs with platinum silicide Schottky-barrier source and drain are reported. With inherently low series resistance and high drive current, these deeply scaled transistors are promising for high-speed analog applications. The fabrication process simplicity is compelling with no implants required. A sub-30-nm gate length pMOSFET exhibited a cutoff frequency of 280 GHz, which is the highest reported to date for a silicon MOS transistor. Off-state leakage current can be easily controlled by augmenting the Schottky barrier height with an optional blanket As implant. Using this approach, good digital performance was also demonstrated. 相似文献
86.
Air-water counter-current flow limit experiments were conducted in thin rectangular channels at atmospheric pressure. The parameters were: narrow channel width, either 1.1 mm or 2.2 mm; inlet water temperature, ranging from 294 K to 330 K; channel surface condition, either clean aluminum, aluminum oxide, or acrylic; location and geometry of the air inlet; method of forcing air through the channel; and liquid head above the channel. Experimental results for each set of parameters can be linearly correlated using the square root of the non-dimensional superficial velocities. Channel surface wetting and location and geometry of the air injection had the greatest effect. Narrow channel width, water temperature, method used to force air through the channel, and liquid head above the channel had little effect on the flooding characteristics. 相似文献
87.
VoiceXML is a markup language for creating voice-user interfaces. It uses speech and telephone touchtone recognition for input and prerecorded audio and text-to-speech synthesis (TTS) for output. It's based on the World Wide Web Consortium's (W3C's) Extensible Markup Language (XML) and leverages the Web paradigm for application development and deployment. By having a common language, application developers, platform vendors, and tool providers all can benefit from code portability and reuse. The paper discusses VoiceXML and the W3C speech interface framework. 相似文献
88.
Paulter N.G. Smith A.J.A. Larson D.R. Souders T.M. Roddie A.G. 《IEEE transactions on instrumentation and measurement》2003,52(6):1825-1833
A comparison of the pulse parameter values obtained from the pulse measurement services of the National Institute of Standards and Technology, USA, and the National Physical Laboratory, U.K., was performed. The comparison was based on the pulse parameters of amplitude, transition duration, overshoot, and undershoot (preshoot). The parameter comparison was applied to raw (measured) waveforms, corrected waveforms (if applicable), and reconstructed waveforms. The results of the comparison show that the pulse parameter values for both national laboratories are within published uncertainties. 相似文献
89.
HK Shu PK Sneed CY Shiau MW McDermott KR Lamborn E Park M Ho PL Petti V Smith LJ Verhey WM Wara PH Gutin DA Larson 《Canadian Metallurgical Quarterly》1996,2(6):335-342
BACKGROUND: Significant changes are restructurng the U.S. health care delivery system. National health reform is now extending itself into the public sector. Increased health and medical costs by federal and state governments are forcing a reevaluation of major entitlement programs, especially Medicaid. METHODS/RESULTS: Because Medicaid is the single largest item in many state budgets, states are now enrolling Medicaid patients into managed and coordinated care arrangements as a means to control costs and increase access to care. HMOs are not only competing for private patients but also actively seeking the Medicaid population. Nationally, almost one-fourth of all Medicaid patients are now enrolled in managed care plans. Various models and approaches have been developed by individual states. CONCLUSIONS: Because managed care enrollment in the Medicaid program has increased substantially in recent years, selected services including vision care are no longer rendered by any practitioner willing to accept Medicaid fees. Freedom of choice is now restricted to pre-selected and panel practitioners participating with the managed care program. The rules, regulations, billing procedures, fees, and program requisites will differ under managed care programs. Private optometric practitioners must consider entering economic and organizational relationships and linkages that make them attractive to managed care organizations. 相似文献
90.
F Tayefeh MD Larson DI Sessler EI Eger T Bowland 《Canadian Metallurgical Quarterly》1997,85(6):1362-1366
To better characterize alterations in autonomic function associated with prolonged anesthesia, we tested the hypothesis that the time-dependent effects of sevoflurane and desflurane differ. We studied seven male volunteers, each anesthetized for 8 h with 1.25 minimum alveolar anesthetic concentration desflurane on one study day and with 8 h sevoflurane on another. These volunteers did not undergo surgery and were minimally stimulated during the study. Measurements included blood pressure, heart rate, pupillary size and light reactivity, concentrations of serum catecholamines, and carbon dioxide production. Over time, heart rate and pupil size increased significantly. During 6 of the 14 anesthetics (45%), heart rate at some point exceeded 95 bpm; similarly, pupil size at some time exceeded 5 mm during 8 anesthetics (57%). In contrast, plasma catecholamine concentrations and carbon dioxide production remained unchanged, and blood pressure remained nearly constant. There are thus substantial time-dependent changes in autonomic functions during prolonged anesthesia, even in unstimulated, nonsurgical volunteers, but we could not detect a difference in these changes during desflurane compared with sevoflurane anesthesia. Implications: Pupil size and heart rate changes are used to guide the delivery of anesthesia. In volunteers, pupil size and heart rate increased with increasing duration of constant desflurane or sevoflurane anesthesia. Thus, anesthetic duration alters heart rate and pupil size independent of surgery and changes in anesthetic delivery. 相似文献