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   488篇
  免费   26篇
  国内免费   1篇
电工技术   3篇
综合类   1篇
化学工业   54篇
金属工艺   12篇
机械仪表   38篇
建筑科学   4篇
能源动力   20篇
轻工业   68篇
水利工程   1篇
石油天然气   1篇
武器工业   1篇
无线电   58篇
一般工业技术   91篇
冶金工业   69篇
原子能技术   7篇
自动化技术   87篇
  2023年   4篇
  2022年   9篇
  2021年   11篇
  2020年   3篇
  2019年   8篇
  2018年   14篇
  2017年   15篇
  2016年   16篇
  2015年   10篇
  2014年   18篇
  2013年   13篇
  2012年   26篇
  2011年   29篇
  2010年   18篇
  2009年   25篇
  2008年   19篇
  2007年   22篇
  2006年   12篇
  2005年   15篇
  2004年   14篇
  2003年   16篇
  2002年   13篇
  2001年   16篇
  2000年   15篇
  1999年   8篇
  1998年   24篇
  1997年   20篇
  1996年   9篇
  1995年   13篇
  1994年   6篇
  1993年   2篇
  1992年   2篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1980年   2篇
  1978年   4篇
  1977年   2篇
  1976年   2篇
  1974年   2篇
  1956年   2篇
  1954年   5篇
  1944年   7篇
  1943年   9篇
  1940年   3篇
  1939年   4篇
  1938年   2篇
  1937年   4篇
  1935年   1篇
  1934年   1篇
排序方式: 共有515条查询结果,搜索用时 15 毫秒
121.
Cortisol, a stress hormone, plays key roles in mediating stress and anti-inflammatory responses. As abnormal cortisol levels can induce various adverse effects, screening cortisol and cortisol analogues is important for monitoring stress levels and for identifying drug candidates. A novel cell-based sensing system was adopted for rapid screening of cortisol and its functional analogues under complex cellular regulation. We used glucocorticoid receptor (GR) fused to a split intein which reconstituted with the counterpart to trigger conditional protein splicing (CPS) in the presence of targets. CPS generates functional signal peptides which promptly translocate the fluorescent cargo. The sensor cells exhibited exceptional performance in discriminating between the functional and structural analogues of cortisol with improved sensitivity. Essential oil extracts with stress relief activity were screened using the sensor cells to identify GR effectors. The sensor cells responded to peppermint oil, and L-limonene and L-menthol were identified as potential GR effectors from the major components of peppermint oil. Further analysis indicated L-limonene as a selective GR agonist (SEGRA) which is a potential anti-inflammatory agent as it attenuates proinflammatory responses without causing notable adverse effects of GR agonists.  相似文献   
122.
123.
We have investigated the electrocaloric (EC) properties of the ceramic 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3. A variety of samples with different median grain sizes, i.e., 1.0, 2.2 and 4.0?μm, and relative densities of about 96% were prepared using atmospheric sintering at 1200oC for 2, 8 and 16?h. The ceramic material with a median grain size of 2.2?μm exhibited the highest value for the EC temperature change, i.e., 1.27?K at 60?kV?cm?1, measured with a high-resolution calorimeter. This value is 25 and 19% higher than the value for the ceramics with the finer and the coarser grains, respectively.  相似文献   
124.
125.
Polycrystalline silicon (poly-Si) films were deposited on glass by very high-frequency (100 MHz) plasma enhanced chemical vapor deposition from a gaseous mixture of SiF4 and H2 with small amounts of SiH4. (2 2 0) oriented films prepared at small SiF4/H2 ratios (<30/40 sccm) showed intrinsic transport properties of poly-Si. However, the room temperature dark conductivity (σd) of the (4 0 0) oriented film was very high for intrinsic poly-Si, 7.2×10−4S/cm. This conductivity exhibited a T−1/4 behavior, suggesting a high defect density at the grain boundaries. It was found that in situ hydrogen plasma treatment successfully produced (4 0 0) oriented poly-Si with a reasonably low σd of 4.5×10−7S/cm and a good photoconductivity of 1.3×10−4S/cm.  相似文献   
126.
The paper analyses, at nanoscale levels, the chemical composition and mechanical properties of the anodic oxide films formed on Ti-6Al-4V alloy by galvanostatic polarization at maximum final voltages of 12-100 V. For the investigations Auger Electron Spectroscopy, Photoelectron Spectroscopy and nanoindentation measurements have been used. The results have shown that anodizing the Ti-6Al-4V alloy produces an oxide film whose thickness depends on the final voltage. The chemical composition is not significantly dependent on the thickness, the film consists of TiO2 and Al2O3. However, the best insulating properties of the films, determined from the growth parameter nm/V, are achieved with a final voltage between 30 and 65 V. Nanohardness and Young's modulus measurements have shown that the anodic films formed by different voltages exhibit similar mechanical properties which is consistent with the results of the surface analysis.  相似文献   
127.
Collecting duct carcinoma (CDC) is a recently recognised histological variety of renal carcinoma (RC) considered to arise from the epithelium of the collecting ducts. Diagnosis of this entity depends on well defined gross and microscopic criteria and is supported by a characteristic immunostaining pattern. The clinical features of these patients, the natural course of the disease and its response to treatment have not been clearly established. Between 1980 and 1990 we treated 12 patients (median age 43 years, range 16-62) with collecting duct carcinoma of the kidney. In addition to being relatively young, each patient had a strong family history of associated malignancies. Survival was short (median 22 months) and 11 patients presented with locally advanced or metastatic disease.  相似文献   
128.
(1 0 3) Oriented AlN films is an attractive piezoelectric material for the applications on surface acoustic wave (SAW) and film bulk acoustic wave (FBAR) devices. As regards the SAW properties of the (1 0 3) oriented AlN films, the electromechanical coupling constant (K2) is larger than the (0 0 2) oriented AlN films. As regards the bulk acoustic wave (BAW) properties of (1 0 3) oriented AlN films, it can excite a quasi-shear mode (velocity = 5957 m/s, K2 = 3.8%) that can be used for FBAR liquid sensor. In this research, the (1 0 3) oriented AlN films were successfully prepared on the silicon substrate by rf magnetron sputtering. Different temperatures (100 °C, 200 °C, 300 °C, and 400 °C) were used in this experiment process. The crystalline structure of films was determined by X-ray diffraction (XRD) and the surface microstructure was investigated by the atomic force microscope (AFM). The result exhibited the optimal substrate temperature is 300 °C. The optimal (1 0 3) oriented AlN films have the strongest XRD intensity, the smallest full width at half maximum (FWHM) value (0.6°), the largest grain size (15.8 nm) and the smoothest surface (Ra = 3.259 nm).  相似文献   
129.
Immer mehr Hochschulen gehen dazu über, Lehrveranstaltungen aufzuzeichnen und den Studierenden oder der ?ffentlichkeit zeitgleich oder zeitversetzt zug?nglich zu machen. Der Beitrag untersucht am Beispiel der Rechtslage in Hessen die damit verbundenen Eingriffe in Grundrechte der Hochschullehrenden und Studierenden, deren Rechtfertigung durch die Aufgaben der Hochschulen, die Verpflichtungen der Hochschullehrenden, die datenschutz- und urheberrechtliche Bewertung sowie die M?glichkeiten, diese Fragen durch hochschuleigenes Recht zu regeln.  相似文献   
130.
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