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排序方式: 共有9665条查询结果,搜索用时 15 毫秒
31.
Alexander Babich Konstantinos Mavrommatis Dieter Senk Heinrich Wilhelm Gudenau 《国际钢铁研究》2004,75(7):428-432
This contribution deals with advanced educational technologies needed to equip customers from higher education institutions, research and industry with efficient tools supporting their work and operating new skills‐training methods. The challenges are reducing the training costs, improving quality and increasing the number of graduates in engineering departments. The concept of a Virtual Lab based on the combination of various teaching methods and tools is presented. Principles of mathematisation in metallurgical education and training are discussed. An example of online course designed in the form of Virtual Lab is demonstrated. 相似文献
32.
A new high-order accurate continuous Galerkin method for linear elastodynamics problems 总被引:1,自引:1,他引:0
Alexander V. Idesman 《Computational Mechanics》2007,40(2):261-279
A new high-order accurate time-continuous Galerkin (TCG) method for elastodynamics is suggested. The accuracy of the new implicit
TCG method is increased by a factor of two in comparison to that of the standard TCG method and is one order higher than the
accuracy of the standard time-discontinuous Galerkin (TDG) method at the same number of degrees of freedom. The new method
is unconditionally stable and has controllable numerical dissipation at high frequencies. An iterative predictor/multi-corrector
solver that includes the factorization of the effective mass matrix of the same dimension as that of the mass matrix for the
second-order methods is developed for the new TCG method. A new strategy combining numerical methods with small and large
numerical dissipation is developed for elastodynamics. Simple numerical tests show a significant reduction in the computation
time (by 5–25 times) for the new TCG method in comparison to that for second-order methods, and the suppression of spurious
high-frequency oscillations. 相似文献
33.
34.
S.B. Burson D. Bradley J. Brockmann E. Copus D. Powers G. Greene C. Alexander 《Nuclear Engineering and Design》1989,115(2-3)
The NRC's Research Program on Core-Debris/Cavity Interactions comprises two principal elements: (1) an analytical effort focused primarily on development of computer codes needed to predict the potential consequences of risk-significant severe-accident scenarios; and (2) an experimental component to provide insights into the relevant phenomenological processes and to develop the experimental data base necessary for validation of the codes. The analytical activities at Sandia National Laboratories (SNL) focus primarily on refinement and validation of the CORCON and VANESA codes. Two major experimental activities are also based at SNL: (1) the large-scale SURC tests address the thermal-hydraulic phenomena in the cavity as well as aerosol release associated with prototypical core-melt materials in various types of concrete crucibles, while (2) the WITCH and GHOST experiments are concerned with aerosol generation and radionuclide release phenomena. A program of small-scale special-effects tests at Brookhaven National Laboratory (BNL) is coupled to a concomitant model-development and code-validation activity. In addition, measurements are being made at Battelle Columbus Laboratory (BCL) to augment the thermochemical data base needed in the VANESA code to permit refined radiological source-term predictions. The current scope and status of this research is reviewed. 相似文献
35.
OBJECTIVE: To determine whether neoadjuvant chemotherapy and radiotherapy for bony sarcomas extending into soft tissues would allow limb salvage yet maintain local disease control. DESIGN: A prospective cohort study. SETTING: A university-affiliated cancer centre in Alberta. PATIENTS: All patients with potentially curable, widely infiltrating bony sarcomas of the extremity without neurologic deficit, referred to the centre in the 6 years from January 1984 to December 1990. There were 11 patients; 1 did not complete the protocol. The mean follow-up was 24 months. INTERVENTIONS: Adriamycin (doxorubicin) was infused for 3 days at a rate of 30 mg/d. A few days later radiotherapy was given 5 days a week for 10 doses at a rate of 3.0 Gy per dose. Four to 5 weeks later the tumour was excised surgically, with placement of a bone allograft or prosthesis, allowing a 1-cm margin of healthy soft tissue and a 5-cm margin of healthy bone and marrow cavity whenever possible. MAIN OUTCOME MEASURES: Need for limb amputation, infectious complications, recurrence of local or regional disease. RESULTS: One patient underwent amputation after fracture through the tumour site. There were two postoperative infections, one acute and one chronic. All patients had full neurologic function of the distal limb. There was no local or regional recurrence of disease. CONCLUSION: Neoadjuvant chemotherapy followed by radiotherapy and tumour excision provides control of aggressive local bone sarcomas while maintaining limb integrity. 相似文献
36.
Steven B. Kuzyk Alexander O. Pritchard Jocelyn Plouffe John L. Sorensen Vladimir Yurkov 《Journal of Great Lakes research》2021,47(3):715-724
Violet and purple bacterial pigmentations are uncommon when considering strict aerobes. Here we report discovery of two novel isolates, P102 and P117 from the freshwater Lake Winnipeg, each with violet to deep purple colony colouration. The relationship between pigment production and growth was investigated under different conditions, including a variety of carbon sources, pH, and temperatures. The violet compounds were purified using polar organic solvents, and then structurally characterized via mass spectrometry and nuclear magnetic resonance to be violacein and deoxyviolacein. Strain P117 produced higher concentrations of the darker pigment deoxyviolacein, which resulted in a deeper hue of violet than in cultures of P102. Strain P102, synthesized violacein maximally in liquid rich organic medium at pH 8 and 20 °C, and had 99.3% sequence similarity to the 16S rDNA from Janthinobacterium lividum. Strain P117, related to Massilia violaceinigra sharing 99.2% 16S rDNA sequence similarity, also produced violacein at similar optimal conditions, but developed higher concentrations of pigment at 15 °C. Culture-based methods found that violacein producers composed 0.001% or 0.023% CFU of environmental heterotrophic populations using BG-11 and potato-based media, respectively. Culture-independent high-throughput ribosomal 16S V4 sequencing of environmental DNA was used to detect Gram-negative species known for their production of violacein. Of all bacterial and archaeal sequences present during the fall in littoral waters and sediment of Lake Winnipeg, 5.5% and 6.3%, respectively, belonged to species that have similar pigment, demonstrating the scarcity of violacein producers in this aquatic freshwater system. 相似文献
37.
Alexander Gatch Dimitry Gorsky Zy Biesinger Eric Bruestle Kelley Lee Curt Karboski Meredith L. Bartron Tyler Wagner 《Journal of Great Lakes research》2021,47(2):486-493
Restoration of a wild-produced lake trout Salvelinus namaycush population in Lake Ontario has not been successful despite the adult population often meeting or exceeding restoration targets. Lack of high-quality spawning habitat in Lake Ontario is suggested as one impediment to recruitment of wild lake trout, although the quantity and location of spawning habitat is poorly understood. If high-quality spawning habitat is limited in Lake Ontario, lake trout may be using uncommon spawning locations such as rivers. Anecdotal angler accounts point to the Niagara River as a lake trout spawning location. To better understand the potential of the Niagara River as a spawning location, egg and juvenile fish collections were conducted 12–14 river kilometers from the mouth of the Niagara River from 2010 to 2012; and mature female lake trout with surgically implanted acoustic tags were monitored from 2015 to 2019. Genetic analyses confirmed 60% of collected eggs and 93% of collected post-hatch juvenile fish in the Niagara River were lake trout. Tagged female lake trout returned to the Niagara River over consecutive years during the spawning season. The short duration of lake trout presence in the river (mean = 56 days/year) suggests female lake trout use the Niagara River primarily for spawning. Diversity in spawning locations may provide lake trout population’s resilience against environmental variability through a portfolio effect. Improved identification of riverine spawning locations, including their overall contribution to wild recruitment, may be a useful tool for managers to restore a wild-produced population of lake trout in Lake Ontario. 相似文献
38.
In this paper, a novel stochastic method is developed for despeckling transrectal ultrasound (TRUS) images of the prostate. By incorporating the circular probe acquisition particularities and speckle noise statistics of TRUS images of the prostate into a likelihood-weighted Monte Carlo estimation scheme, the proposed method can better remove speckle noise while preserving image structures and details that are relevant for image screening, allowing for a better delineation of the lesion contour. Our in silico and in vivo experimental results are promising, which was confirmed by a clinical evaluation of the in vivo test cases by experienced clinicians, and indicate that our method potentially can perform better than other previously proposed methods. 相似文献
39.
40.
In this paper we study small depth circuits that contain threshold gates (with or without weights) and parity gates. All circuits we consider are of polynomial size. We prove several results which complete the work on characterizing possible inclusions between many classes defined by small depth circuits. These results are the following:
相似文献
1. | A single threshold gate with weights cannot in general be replaced by a polynomial fan-in unweighted threshold gate of parity gates. |
2. | On the other hand it can be replaced by a depth 2 unweighted threshold circuit of polynomial size. An extension of this construction is used to prove that whatever can be computed by a depthd polynomial size threshold circuit with weights can be computed by a depthd+1 polynomial size unweighted threshold circuit, whered is an arbitrary fixed integer. |
3. | A polynomial fan-in threshold gate (with weights) of parity gates cannot in general be replaced by a depth 2 unweighted threshold circuit of polynomial size. |