首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1368篇
  免费   17篇
  国内免费   2篇
电工技术   45篇
化学工业   265篇
金属工艺   23篇
机械仪表   19篇
建筑科学   17篇
能源动力   31篇
轻工业   98篇
水利工程   8篇
石油天然气   2篇
无线电   192篇
一般工业技术   219篇
冶金工业   377篇
原子能技术   31篇
自动化技术   60篇
  2022年   5篇
  2021年   14篇
  2020年   7篇
  2019年   13篇
  2018年   5篇
  2017年   12篇
  2016年   25篇
  2015年   12篇
  2014年   18篇
  2013年   37篇
  2012年   39篇
  2011年   45篇
  2010年   35篇
  2009年   24篇
  2008年   50篇
  2007年   40篇
  2006年   31篇
  2005年   34篇
  2004年   37篇
  2003年   24篇
  2002年   30篇
  2001年   24篇
  2000年   34篇
  1999年   39篇
  1998年   150篇
  1997年   97篇
  1996年   67篇
  1995年   51篇
  1994年   40篇
  1993年   35篇
  1992年   27篇
  1991年   21篇
  1990年   28篇
  1989年   24篇
  1988年   16篇
  1987年   12篇
  1986年   14篇
  1985年   19篇
  1984年   10篇
  1983年   12篇
  1982年   14篇
  1981年   18篇
  1980年   12篇
  1979年   12篇
  1978年   9篇
  1977年   9篇
  1976年   23篇
  1975年   8篇
  1974年   5篇
  1972年   5篇
排序方式: 共有1387条查询结果,搜索用时 15 毫秒
941.
This paper describes the evaluation method of the gait motion in walk rehabilitation. We assume that the evaluation consists of the classification of the measured data and the prediction of the feature of the gait motion. The method may enable a doctor and a physical therapist to recognize the condition of the patients more easily, and increase the motivation of patient further for rehabilitation. However, it is difficult to divide the gait motion into discrete categories, since the gait motion continuously changes and does not have the clear boundaries. Therefore, the self-organizing map (SOM) that is able to arrange the continuous data on the almost continuous map is employed in order to classify them. And, the feature of the gait motion is predicted by the classification. In this study, we adopt the gravity-center fluctuation (GCF) on the sole as the measured data. First, it is shown that the pattern of the GCF that is obtained by our developed measurement system includes the feature of the gait motion. Secondly, the relation between the pattern of the GCF and the feature of the gait motion that the doctor and the physical therapist evaluate by visual inspection is considered using the SOM. Next, we describe the prediction of following features measured by numerical values: the length of stride, the velocity of walk and the difference of steps that are important for the doctor and the physical therapist to make a diagnosis of the condition of the gait motion in walk rehabilitation. Finally, it is investigated that the position of a new test data that is arranged on the map accords with the prediction. As a consequence, we confirm that the method using the SOM is often useful to classify and predict the condition of the patient.  相似文献   
942.
International Journal on Document Analysis and Recognition (IJDAR) - We present a technique based on stroke order normalization for improving recognition of online handwritten mathematical...  相似文献   
943.
Tumor-associated macrophages (TAMs) and abnormalities in cancer cells affect cancer progression and response to therapy. TAMs are a major component of the tumor microenvironment (TME) in breast cancer, with their invasion affecting clinical outcomes. Programmed death-ligand 1 (PD-L1), a target of immune checkpoint inhibitors, acts as a suppressive signal for the surrounding immune system; however, its expression and effect on TAMs and the clinical outcome in breast cancer are unknown. In this study, we used high-throughput multiple immunohistochemistry to spatially and quantitatively analyze TAMs. We subjected 81 breast cancer specimens to immunostaining for CD68, CD163, PD-1, PD-L1, CD20, and pan-CK. In both stromal and intratumoral areas, the triple-negative subtype had significantly more CD68/CD163, CD68/PD-L1, and CD163/PD-L1 double-positive cells than the estrogen receptor (ER)/progesterone receptor (PR) subtype. Interestingly, a higher number of CD68+/PD-L1+/CK-/CD163- TAMs in the intratumoral area was correlated with a favorable recurrence rate (p = 0.048). These findings indicated that the specific subpopulation and localization of TAMs in the TME affect clinical outcomes in breast cancer.  相似文献   
944.
We present temperature, modulation, and free-space link characteristics of monolithically integrated vertical-cavity lasers (VCLs) and resonant photodetectors. The devices have been integrated using a novel structure that makes it possible to fabricate devices with through-the-substrate emission and detection. Taking advantage of the substrate emitting/detecting architecture, we monolithically integrate microlenses on the substrate side of the devices and flip-chip bond arrays without via processes or substrate removal. Low-threshold high-efficiency VCLs exhibit maximum small-signal modulation bandwidths, which are limited by parasitics, of ~9.5 GHz at 20°C and ~8.4 GHz at 70°C. The VCLs have the lowest reported bias currents required to reach bandwidths of up to ~8 GHz. A free-space optical link is demonstrated with flip-chip-bonded arrays of microlensed, monolithically integrated VCLs and detectors. The link is found to be tolerant to temperature differences of ±75°C between the VCL and detector, with error free (BER<10-12) data transmission demonstrated in each case  相似文献   
945.
We review the design, fabrication, and characterization of 1.55-μm lattice-matched vertical-cavity surface-emitting lasers, operating continuous wave up to 88°C. For one embodiment, the threshold current is 800 μA, the differential quantum efficiency is 23%, and the maximum output power is more than 1 mW at 20°C and 110 μW at 80°C. The basic structure consists of AlAsSb-AlGaAsSb mirrors, which provide both high reflectivity and an InP-lattice-matched structure. The quaternary mirrors have poor electrical and thermal conductivities, which can raise the device temperature. However, a double-intracavity-contacted structure along with thick n-type InP cladding layers circumvents these drawbacks and finally leads to an excellent performance. The measured voltage and thermal impedances are much lower for the intracavity-contacted device than an air-post structure in which current is injected through the Sb-based quaternary mirror. The structure utilizes an undercut aperture for current and optical confinement. The aperture reduces scattering loss at the etched mirror and contributes to high differential efficiency and low threshold current density  相似文献   
946.
The vehicle information and communication system (VICS) is starting to become practicable. The infrared system of a VICS detects vehicles on the road by using optical beacons to control traffic and to supply real-time traffic information. But it needs an enormous budget because the optical beacons must be located on every lane of the road throughout the country. We propose a traffic information system using existing LED traffic lights, and focus on its visible rays and power used for traffic control, the number and location of the traffic lights, and the movement toward LED traffic lights. We design the best service area not to interfere with other service areas and analyze its basic performance such as the suitable modulation, required SNR and the amount of receivable information  相似文献   
947.
Ga2O3 and Ga2O3/TiO2 catalysts were found to be effective agents for the dehydrogenation of ethane to ethene in the presence of carbon dioxide at 650 °C. The activity of the Ga2O3 and Ga2O3/TiO2 catalysts in the presence of CO2 was 2–4 times higher than that without CO2. Ethene yields reached ca. 20–25% and selectivity was ca. 70–90% at 650°C in the 17% ethane and 83% CO2 feed at an SV of 9,000 ml/(g‐cat h). The presence of CO2 markedly promoted dehydrogenation of ethane over Ga2O3 and Ga2O3/TiO2 catalysts. Furthermore, the promoting effect of CO2 on the aromatization of ethane and ethene over a Ga2O3+H/ZSM‐5 catalyst was also observed above 650 °C. Aromatics yields were higher than those without CO2. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
948.
Electron paramagnetic resonance (EPR) in conjunction with a slow-tumbling simulation was utilized for defining stratum corneum (SC) lipid structure. We found that ordering calculated from the simulation is an appropriate index for evaluating SC lipids structure. The SC from two sites (mid-volar forearm and lower-leg) of human volunteers was stripped consecutively from one to three times using a glass plate coated with a cyanoacrylate resin. Aliphatic spin probes, 5-doxylstearic acid (5-DSA) and 3β-doxyl-5α-cholestane (CHL), were used to monitor SC ordering. EPR spectrum of 5-DSA incorporated in the SC demonstrated a characteristic peak for the first strip. However, EPR spectra of CHL in the SC did not show a clear difference for each strip, except for the peak intensity. The results imply that CHL is not incorporated into the lipid phase as easily as 5-DSA is. A slow-tumbling simulation of the EPR spectrum was performed to analyze the detailed lipid structure. The simulation results for 5-DSA show differences in values of the SC ordering as a function of depth. Thus, these results along with the simulation analysis provide a detailed SC layer structure.  相似文献   
949.
Small bubbles of nitrogen, methane, or argon with an average radius of 50 nm, as measured by scanning electron microscopy, were prepared under atmospheric conditions. The lifetime of the nanobubbles extended to more than two weeks. The total amount of gases in the nanobubble solutions reached 600 cm3 per 1 dm3 of water, and the liquid density was about 0.988 g/cm3. The internal pressure of the nanobubbles was estimated to be 6 MPa. The number of nanobubbles was 1.9×1016 bubbles per 1 dm3 of water. These findings show that almost no gas samples are dissolved homogeneously in the aqueous solution and that the vast majority is present in the form of nanobubbles, that is, nanobubbles should be thermodynamically unstable. Attenuated total reflectance infrared spectroscopy showed that the surfaces of the nanobubbles contain hard hydrogen bonds that may reduce the diffusivity of gases through the interfacial film.  相似文献   
950.
The aim of this study was to verify the feasibility of drying pharmaceutical microcapsules in a spouted bed with the aid of inert particles. The morphological character and total recovery of the drug model, indomethacin, were compared for spray and spouted bed dried microcapsules. Clusters formed by microcapsules coalescence in the spouted bed showed to have their size dependent on bed height. The total recoveries for three different bed heights were 53.18%, 60.76%, 70.70%, as compared to 95.65% for the spray drying process. The results showed that spouted beds are promising for the preparation of slow‐release drug systems.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号