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   633篇
  免费   38篇
  国内免费   1篇
电工技术   7篇
综合类   1篇
化学工业   136篇
金属工艺   10篇
机械仪表   12篇
建筑科学   16篇
矿业工程   1篇
能源动力   24篇
轻工业   106篇
水利工程   3篇
石油天然气   2篇
无线电   47篇
一般工业技术   84篇
冶金工业   116篇
原子能技术   6篇
自动化技术   101篇
  2024年   4篇
  2023年   7篇
  2022年   18篇
  2021年   27篇
  2020年   14篇
  2019年   14篇
  2018年   21篇
  2017年   17篇
  2016年   20篇
  2015年   14篇
  2014年   27篇
  2013年   39篇
  2012年   30篇
  2011年   32篇
  2010年   27篇
  2009年   29篇
  2008年   26篇
  2007年   13篇
  2006年   21篇
  2005年   21篇
  2004年   12篇
  2003年   9篇
  2002年   12篇
  2001年   14篇
  2000年   5篇
  1999年   16篇
  1998年   26篇
  1997年   24篇
  1996年   13篇
  1995年   21篇
  1994年   20篇
  1993年   7篇
  1991年   4篇
  1990年   6篇
  1989年   7篇
  1988年   4篇
  1987年   2篇
  1986年   5篇
  1985年   6篇
  1984年   6篇
  1983年   4篇
  1982年   5篇
  1977年   2篇
  1976年   5篇
  1975年   3篇
  1973年   1篇
  1969年   4篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
排序方式: 共有672条查询结果,搜索用时 15 毫秒
81.
BACKGROUND: Although intrarenal dopamine is known to behave as an endogenous natriuretic hormone the role of the renal dopaminergic system in the sodium handling of nephrotic oedema remains unknown. STUDY DESIGN: We monitored the daily urinary excretion of free dopamine, L-DOPA-its precursor, and its metabolites, DOPAC and HVA, during sodium retention accompanying the nephrotic state and natriuresis leading to oedema mobilization in eight patients (mean age 8.0+/-2.4 years) with drug-induced remission of minimal-change nephrotic syndrome (MCNS). RESULTS: During natriuresis the urinary levels of dopamine did not increase in parallel with sodium excretion in any of the eight patients studied. Moreover, after remission of the nephrotic syndrome the urinary levels of dopamine were significantly lower than during the nephrotic state (1565.3+/-361.7 vs 2416.1+/-558.4, P= 0.02). In contrast, the urinary excretion of L-DOPA increased markedly during natriuresis resulting from remission of proteinuria (from 87.0+/-40.5 up to 296.9+/-86.3 nmol/24 h; P< 0.01). CONCLUSION: We conclude that the natriuretic response resulting from drug-induced remission of proteinuria in MCNS is accompanied by a decrease in the renal uptake/decarboxylation of L-DOPA to dopamine.  相似文献   
82.
A design for a drift collection calorimeter having a combined radiator and electric field shaping structure made of fused lead glass tubing is described. Reduction of a surface layer of lead oxide in a hydrogen oven is used to form a high resistance metallic layer on the interior of the tubes. This layer is used as a continuous voltage divider for drift field shaping. The EGS shower Monte Carlo code was used to model the performance of the proposed calorimeter. The effects of choice of the tube geometry, gas pressure and sampling scheme (digital vs. conventional) are discussed. The possibility of using this type of radiator/drift field structure in liquid argon is briefly considered.  相似文献   
83.
A study is presented on the protein composition of the Venezuelan corn cultivars Venezuela-1, Arichuna, Obregón and Venezuela-1 Opaque-2. The proteins were isolated and analyzed for their molecular weight and lysine and tryptophan content. Protein fractionation showed significant differences between normal corn cultivars and Opaque-2. The latter showed a low level of zein and a high content of alcohol-insoluble reduced glutelins (AIG), albumins and globulins in relation to the normal kernel. The relative increase of these protein fractions, rich in lysine and tryptophan, results in a higher concentration of these amino acids in the Opaque kernel, as revealed by the analysis of these compounds carried out in different cultivars. Electrophoretic analysis showed only small differences in the number and intensity of bands from the protein fractions of the maize cultivars under study.  相似文献   
84.
A seismic noise study has been carried out on the well-known Mt. Amiata geothermal area; the aim of this work is to understand the correlation between the geothermal system and seismic noise characteristics. The power spectra of the recorded noise show that in the whole geothermal area a low frequency noise (3 Hz) is predominant. The fitting of the results with a pressure variation source model shows contradictory results.  相似文献   
85.
Poly (L-lactide)-poly (oxyethylene)-poly (L-lactide) block copolymers obtained in bulk, by a ring opening mechanism, from poly (ethylene glycol)s (PEG)s and L-lactide (LA), at 120–140°C, in the absence of added catalysts are described. By using PEGs with different molecular masses, 3000 and 35000, respectively, and varying the initial molar ratio LA to PEG, two series of copolymers with different molecular masses, relative length of blocks and hydrophilicity were obtained. Physico-chemical characterization of the copolymers had been previously performed. The morphological characteristics of the copolymers were investigated by means of X-ray diffractometry, optical and scanning electron microscopy. The biological properties of the materials were determined by evaluating their cytotoxicity, cytocompatibility, hemocompatibility and degradability using different standard tests. The results obtained indicate that the block copolymers synthesized may be useful for biomedical applications, in particular as resorbable drug vehicles. The materials are brittle and their mechanical properties are not appropriate for implant devices.  相似文献   
86.
Syndiotactic poly(p-fluoro-styrene) (s-PPFS) has been prepared with a polymerization procedure which allows reaching high average molecular masses and satisfactory yields. The polymorphic behavior of the polymer has been mainly studied by X-ray diffraction, calorimetric and infrared analyses. The main crystalline phase of s-PPFS, obtained by melt processing or cold-crystallization, exhibits trans-planar chains, is orthorhombic (a = 9.5 Å, b = 28.7 Å, c = 5.1 Å) and melts at nearly 320 °C. The X-ray analysis shows a strict analogy of this orthorhombic phase with the β phase of s-PS, also as for the occurrence of two limit ordered (β″) and disordered (β′) modifications, which differ for the intensity of reflections characterized by h + k = 2n + 1. A metastable crystalline phase, also exhibiting trans-planar chains, has been observed for as-polymerized samples as well as for amorphous samples crystallized by sorption of toluene or 1,4-difluoro-benzene. Mainly on the basis of solvent sorption and desorption experiments, it is suggested that this metastable phase is a co-crystalline phase with the low-molecular-mass guest molecules.  相似文献   
87.
Lung cancer represents an extremely diffused neoplastic disorder with different histological/molecular features. Among the different lung tumors, non-small-cell lung cancer (NSCLC) is the most represented histotype, characterized by various molecular markers, including the expression/overexpression of the fibroblast growth factor receptor-1 (FGFR1). Thus, FGF/FGFR blockade by tyrosine kinase inhibitors (TKi) or FGF-ligand inhibitors may represent a promising therapeutic approach in lung cancers. In this study we demonstrate the potential therapeutic benefit of targeting the FGF/FGFR system in FGF-dependent lung tumor cells using FGF trapping (NSC12) or TKi (erdafitinib) approaches. The results show that inhibition of FGF/FGFR by NSC12 or erdafitinib induces apoptosis in FGF-dependent human squamous cell carcinoma NCI-H1581 and NCI-H520 cells. Induction of oxidative stress is the main mechanism responsible for the therapeutic/pro-apoptotic effect exerted by both NSC12 and erdafitinib, with apoptosis being abolished by antioxidant treatments. Finally, reduction of c-Myc protein levels appears to strictly determine the onset of oxidative stress and the therapeutic response to FGF/FGFR inhibition, indicating c-Myc as a key downstream effector of FGF/FGFR signaling in FGF-dependent lung cancers.  相似文献   
88.
89.
正多伦多大学丹尼尔斯建筑、景观和设计学院的设计采用了分期的方法,包括修复和扩建以前称为"知识学院"的标志性建筑,将现有建筑物改造成与教学和需求更相关的框架体系。这个十九世纪遗址的总体规划是通过对预期用途模式和场地生态的分析而制定的,目的是重新定位校园西南角与安大略湖的轴线,并为学院创造新的特性。丹尼尔斯建筑、景观和设计学院需要一个可持续发展的新型工  相似文献   
90.
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