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排序方式: 共有831条查询结果,搜索用时 15 毫秒
31.
This investigation analyses the failure of left barrel used in engine of an aircraft. The barrel was subjected to detailed examination using standard non-destructive and destructive testing methods in order to identify the cause of failure of left barrel. The experimental results include fractography, chemical analysis, coating analysis and optical microstructure. The investigation concludes that failure is caused by the formation of corrosion pits which act as stress raiser and fatigue has assisted in propagation of the crack. 相似文献
32.
S. Narendra Babu A. Siddeshwar K. Srinivas S. V. Suryanarayana T. Bhimasankaram 《Journal of Materials Science》2009,44(15):3948-3951
A composite material when placed under the external magnetic/electric fields exhibits voltage/induced magnetization is known
as magnetoelectric (ME) composite. Such composite materials should have ferroelectric and ferro/ferri magnetic phases as constituents.
The magnetoelectric output is exhibited as a product property. Magnetoelectric composites are being used for variety of applications
including resonators, filters, phase shifters, optical isolators, actuators and magnetic field sensors. Metal/ferroelectric/metal
magnetoelectric composite using Ni and PZT as constituent phases has been fabricated in 2-2 composite pattern to study its
product property. The paper presents magnetoelectric studies of Ni/PZT/Ni composite using low dc magnetic field magnetoelectric
set-up. Using this ME set-up ME output of Ni/PZT/Ni composite is studied as a function of dc magnetic field. The results were
analyzed to identify the useful magnetic field (dc and ac) range in which Ni/PZT/Ni sensor can be utilized for applications. 相似文献
33.
Y. Kalyana Lakshmi K. Srinivas B. Sreedhar M. Manivel Raja M. Vithal P. Venugopal Reddy 《Materials Chemistry and Physics》2009,113(2-3):749-755
With a view to understand the influence of nano size on various properties of cobalt-doped ZnO-based diluted magnetic semiconductors, a series of materials were prepared by the citrate gel route. The phase and morphology studies have been carried out by X-ray diffraction and transmission electron microscopy, respectively. All the samples of the present investigation are found to have hexagonal wurtzite structure and crystallite sizes are found to vary from 25 nm to 65 nm. From the optical absorption measurements it has been observed that upon doping with cobalt, the energy band gap is found to shift towards lower energy side (red shift) while it shifts towards higher energy side (blue shift) when the crystallite size is increased continuously. It has been observed from the XPS results that oxidation state of Cobalt is +2 and that the difference in binding energies of Co 2p3/2 and Co 2p1/2 is found to increase continuously with increasing crystallite size. Finally, all the samples are found to exhibit room temperature ferromagnetism and the specific magnetization decreases with increasing crystallite size. 相似文献
34.
Claude J. RENAUD Xuling LIN Srinivas SUBRAMANIAN Dale A. FISHER 《Hemodialysis international. International Symposium on Home Hemodialysis》2011,15(1):63-68
Methicillin‐sensitive Staphylococcus aureus (MSSA) bacteremia is a leading cause of infection in hemodialysis (HD) patients. Cloxacillin, cefazolin, and vancomycin are the mainstay antimicrobials. Cloxacillin administration leads to frequent drug dosing, longer length of stay (LOS), and higher cost, while resistance and poorer outcomes are associated with vancomycin use. Dosing cefazolin during HD allows for prolonged blood therapeutic levels. We assessed the outcomes and safety of a strategy of treating MSSA bacteremia with 2–3 g cefazolin on HD only. All HD patients with MSSA bacteremia admitted in June–December 2009 at our center and receiving this regime were compared with historical controls who received cloxacillin. Demographic characteristics and outcome measures like mortality, LOS, cost, recrudescence, and adverse drug reactions were assessed. Of 27 consecutive episodes reviewed, 14 and 13 patients received cefazolin and cloxacillin, respectively. Baseline demographics were comparable between the 2 treatment groups. More than one‐third of the bacteremia was related to tunneled catheter infection. The 30‐day mortality of cloxacillin‐ and cefazolin‐treated patients was 15% and 7%, respectively (P=0.14). Two of the 11 survivors treated with cloxacillin (18%) had recrudescent bacteremia while none was observed in cefazolin‐treated survivors. Cefazolin was associated with shorter LOS (10 vs. 20 days, P<0.05) and lower cost (US$8262.00 vs. US$15,367.00, P<0.05). Cefazolin use resulted in 3 idiosyncratic adverse drug reactions. Cefazolin dosed on each HD in MSSA bacteremia leads to earlier discharge and less cost. Larger prospective studies are, however, warranted to fully assess its safety and efficacy. 相似文献
35.
Srinivas Peeta F. Sibel Salman Dilek Gunnec Kannan Viswanath 《Computers & Operations Research》2010,37(10):1708-1719
We address a pre-disaster planning problem that seeks to strengthen a highway network whose links are subject to random failures due to a disaster. Each link may be either operational or non-functional after the disaster. The link failure probabilities are assumed to be known a priori, and investment decreases the likelihood of failure. The planning problem seeks connectivity for first responders between various origin–destination (O–D) pairs and hence focuses on uncapacitated road conditions. The decision-maker's goal is to select the links to invest in under a limited budget with the objective of maximizing the post-disaster connectivity and minimizing traversal costs between the origin and destination nodes. The problem is modeled as a two-stage stochastic program in which the investment decisions in the first stage alter the survival probabilities of the corresponding links. We restructure the objective function into a monotonic non-increasing multilinear function and show that using the first order terms of this function leads to a knapsack problem whose solution is a local optimum to the original problem. Numerical experiments on real-world data related to strengthening Istanbul's urban highway system against earthquake risk illustrate the tractability of the method and provide practical insights for decision-makers. 相似文献
36.
Flow past a square cylinder at a Reynolds number of 21,400 has been studied numerically using the large-eddy simulation technique. A dynamic subgrid-scale stress model has been used for the small scales of turbulence. The time- and span-averaged axial and transverse velocities in the downstream of the cylinder are in good agreement with the experimental results. The distribution of turbulent normal and shear stresses is also well predicted. The coherent and incoherent components of turbulent fluctuations at some specified phases have been separated and their relative magnitudes downstream of the cylinder have been compared. The comparison shows more coherence in the near wake than the far wake, while the coherent and incoherent components are of comparable magnitude in the far wake. The far wake shows irregular phase-averaged structures. 相似文献
37.
38.
T. Srinivas 《Journal of the science of food and agriculture》1975,26(10):1479-1482
Stress cracks usually develop across the grain in rice, although longitudinal cracks also develop occasionally on one axis. On examination of sections of rice grain it was noticed that orientation of elongated cells provided cell wall continuation across the grain and also along the length in the dorsiventral axis. Cracks were found to develop easily along these cell wall lines. Crack formation was difficult in the lateral axis along the length since cell wall continuity was absent. However, when severely dried grains were suddenly wetted cracks developed even in this axis by disruption of cells along the cleavage path. 相似文献
39.
Experiments on enclosed laminar diffusion flames have revealed the existence of a critical relative velocity of air and fuel which is associated with the threshold of low frequency flame vibration. Starting from the hypothesis that these vibrations are triggered by a selectively amplified disturbance arising in the free shear layers near the base of the flame, the authors have obtained evidence of the nature of the disturbance. Further systematic experiments have enabled them to account for the observed behavior of low frequency vibrating diffusion flames in the light of their hypothesis and in relation to the acoustical properties of their combustion system. 相似文献
40.
Two-phase flow regimes in round, square and rectangular tubes during condensation of refrigerant R134a 总被引:1,自引:0,他引:1
An experimental investigation of two-phase flow mechanisms during condensation of refrigerant R134a in six small diameter round (4.91 mm), square (Dh=4 mm, α=1), and rectangular (4×6 and 6×4 mm: Dh=4.8 mm, α=0.67 and 1.5; 2×4 and 4×2 mm: Dh=2.67 mm, α =0.5 and 2) was conducted. Unique experimental techniques and test sections were developed to enable the documentation of the flow mechanisms during phase change. For each tube under consideration, flow mechanisms were recorded over the entire range of qualities for five different refrigerant mass fluxes between 150 and 750 kg m−2 s−1. The flow mechanisms were categorized into four different flow regimes: intermittent flow, wavy flow, annular flow, and dispersed flow. In addition, the large amount of data enabled the delineation of several different flow patterns within each flow regime, which provides a clearer understanding of the different modes of two-phase flow. Transition lines between the respective flow patterns and regimes on these maps were established based on the experimental data. It was found that for similar hydraulic diameters, flow regime transitions are not very strongly dependent on tube shape or aspect ratio. These maps and the transition lines can be used to predict the particular flow pattern or regime that will be established for a given mass flux, quality and tube geometry. 相似文献