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   115篇
  免费   9篇
电工技术   4篇
化学工业   18篇
机械仪表   4篇
建筑科学   2篇
能源动力   3篇
轻工业   16篇
水利工程   3篇
石油天然气   1篇
无线电   15篇
一般工业技术   17篇
冶金工业   25篇
自动化技术   16篇
  2023年   1篇
  2022年   1篇
  2021年   6篇
  2020年   1篇
  2019年   2篇
  2018年   11篇
  2017年   2篇
  2016年   1篇
  2015年   2篇
  2014年   3篇
  2013年   4篇
  2012年   5篇
  2011年   10篇
  2010年   1篇
  2009年   4篇
  2008年   3篇
  2007年   3篇
  2006年   10篇
  2005年   5篇
  2004年   5篇
  2003年   7篇
  2002年   3篇
  2001年   6篇
  2000年   3篇
  1998年   8篇
  1997年   4篇
  1995年   2篇
  1993年   2篇
  1992年   1篇
  1989年   1篇
  1985年   1篇
  1983年   1篇
  1977年   1篇
  1974年   1篇
  1972年   1篇
  1970年   1篇
  1969年   1篇
排序方式: 共有124条查询结果,搜索用时 31 毫秒
41.
The antiproteinuric effect of angiotensin converting enzyme (ACE) inhibition in insulin-dependent diabetes mellitus (IDDM) patients with diabetic nephropathy varies considerably. Therefore, we tested the potential role of an insertion (I)/deletion (D) polymorphism of the ACE gene on this early antiproteinuric responsiveness in an observational follow-up study. Sixty (II, N = 13; ID, N = 26 and DD, N = 21) young hypertensive IDDM patients suffering from diabetic nephropathy were investigated during three months before and for the initial six month period during ACE inhibition [captopril 44 (SD 22) mg/24 hr, no differences in drug dose between groups]. Blood pressure (MABP) and albuminuria (ELISA) were measured three (1 to 6) times before and three (1 to 13) times during ACE inhibition. At baseline the groups (II/ID/DD) had comparable (1) mean arterial blood pressure (MABP mm Hg) of 113 +/- 10/108 +/- 9/114 +/- 8, (2) albuminuria (geometric mean with 95% CI) 1394 (747 to 2608)/1176 (844 to 1797) and 1261 (827 to 2017) mg/24 hr, and (3) serum creatinine (geometric mean with 95% CI), 80 (68 to 93)/85 (76 to 97)/103 (85 to 119) mumol/liter, respectively. Angiotensin converting enzyme inhibition induced a significant reduction in MABP, albuminuria and kidney function in all three groups (II/ID/DD; P < 0.05): (1) MABP (mean +/- SD) 12 +/- 7/5 +/- 7/8 +/- 9 mm Hg (ANOVA, P = 0.02); (2) albuminuria [mean (95% CI)] 61 (34 to 77)/22 (3 to 37)/31 (13 to 46) %, (ANOVA, P < 0.01); and (3) increasing serum creatinine [mean (95% CI)] 8 (4 to 12)/9 (3 to 16)/8 (0 to 16) % (ANOVA, NS), respectively. Adjusting for differences in reduction in MABP did not change the association between decrease in albuminuria and ACE/ID genotypes (P < 0.01). A multiple linear regression analysis revealed that the ACE/ID polymorphism, albuminuria and MABP at baseline independently influenced the decline in albuminuria after initiation of ACE inhibition (R2 = 0.21, P < 0.01). A significant association between changes in MABP and albuminuria was demonstrated (R2 = 0.16, P < 0.01). Our data show that hypertensive albuminuric IDDM patients with the II genotype are particularly susceptible to commonly advocated renoprotective treatment.  相似文献   
42.
Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1?:?1 combination of zinc(II) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(IV) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room temperature preparation of the nanosheets has provided the first X-ray crystal structure of a cooperative binary ionic (CBI) solid. The unit cell contains one and one-half molecules of aquo-ZnTPPS(4-) (an electron donor) and three half molecules of dihydroxy-SnTNMePyP(4+) (an electron acceptor). Charge balance in the solid is reached without any non-porphyrinic ions, as previously determined for other CBI nanomaterials by non-crystallographic means. The crystal structure reveals a complicated molecular arrangement with slipped π-π stacking only occurring in isolated dimers of one of the symmetrically unique zinc porphyrins. Consistent with the crystal structure, UV-visible J-aggregate bands indicative of exciton delocalization and extended π-π stacking are not observed. XRD measurements show that the structure of the Zn/Sn nanosheets is distinct from that of Zn/Sn four-leaf clover-like CBI solids reported previously. In contrast with the Zn/Sn clovers that do exhibit J-aggregate bands and are photoconductive, the nanosheets are not photoconductive. Even so, the nanosheets act as light-harvesting structures in an artificial photosynthesis system capable of reducing water to hydrogen but not as efficiently as the Zn/Sn clovers.  相似文献   
43.
Increasing die size and large coefficient of thermal expansion (CTE) mismatch in flip-chip plastic ball grid array (FC-PBGA) packages have made die fracture a major failure mode during reliability testing. Most die fracture observed before was die backside vertical cracking, which was caused by excessive package bending and backside defects. However, due to die edge defects induced by the singulation process and the choice of underfill material, an increasing number of die cracks were found to initiate from die edge and propagate horizontally across the die. In order to improve package reliability and performance, die edge cracking has to be eliminated. An extensive finite element analysis was completed to investigate die edge cracking and find its solutions. A fracture mechanics approach was used to evaluate the effect of various package parameters on die edge initiated fracture. Strain energy release rate was found to be an effective technique for evaluating die edge initiated fracture from singulation-induced flaws. The impact of initial flaw size and a variety of package parameters was investigated. Unlike in die backside cracking, the dominant parameters causing die edge horizontal fracture are more closely related to local effects.  相似文献   
44.
An 89-year-old woman with recurrent conjunctival mucoepidermoid carcinoma developed intraocular inflammation and an elevated fundus lesion that simulated choroidal detachment in her affected right eye. Intraocular invasion of squamous cell carcinoma was suspected and the eye was enucleated. Pathologic examination of the enucleated eye showed intraocular invasion by conjunctival mucoepidermoid carcinoma that formed a suprauveal cyst lined with malignant epithelial cells. The patient developed an orbital recurrence 1 year later and underwent orbital exenteration. She died 2 years later from an unrelated cause. Conjunctival mucoepidermoid carcinoma can exhibit intraocular invasion and produce an intraocular neoplastic cyst.  相似文献   
45.
The neuropeptide, galanin, has been implicated in the regulation of rat growth hormone (rGH) release. In the present study, adult male rats were implanted dually with cannulae to the lateral cerebral ventricle and the right atrium. After surgical recovery, rats were infused with M-15, a specific galanin antagonist, into the lateral ventricle. During the course of this brain infusion, rats were subjected to serial blood sampling with red cell and artificial plasma replacement under stress-free conditions. Plasma was saved for rGH assay. Treatment with M-15 reduced rGH pulse amplitude and pulse frequency when compared to vehicle-infused controls. These data suggest that brain galanin participates in the ongoing stimulation of pulsatile rGH release in the adult male rat.  相似文献   
46.
Data integrity is a primary concern for the users of any data storage medium. For optical data storage, the integrity is directly related to the performance and defect level of the storage media and to how they change as the media age. While media materials and thin-film stack designs are chosen with the goal of achieving high data integrity and reliability, variations in the media manufacturing processes themselves often can determine how the media will behave. These variations can be found through detailed and careful characterization testing. The authors describe some of the test methods used for characterizing rewritable media and discuss some results obtained while surveying commercially available media  相似文献   
47.
48.
The fourth‐order model of the reaction wheel pendulum is considered and a fourth‐order discontinuous integral algorithm is used for stabilization and tracking of the system, using a continuous control signal. The states reach the origin or a reference signal in finite‐time, even in presence of uncertain control coefficient and a kind of matched and unmatched uncertainties/disturbances. A homogeneous Lyapunov function is designed to ensure local finite‐time stability of the system, which can be used for designing the controller gains. Simulations and experimental results illustrate the performance and advantages of the presented algorithm.  相似文献   
49.
Mercado AE  He X  Xu W  Jabbari E 《Nanotechnology》2008,19(32):325609
Lactide-co-glycolide-based functionalized nanoparticles (NPs), because of their high surface areas for conjugation and biodegradability, are attractive as carriers for stabilization and sustained delivery of therapeutic agents and protein drugs. The objective of this work was to compare the release characteristics of model molecules encapsulated in NPs produced from poly(lactide-co-glycolide fumarate) (PLGF) macromer with those of model molecules conjugated to NPs produced from succinimide (NHS)-terminated PLGF-NHS macromer. Poly(lactide fumarate) (PLAF), PLGF and poly(lactide-co-ethylene oxide fumarate) (PLEOF) macromers were synthesized by condensation polymerization. The hydroxyl end-groups of PLAF and PLGF macromers were reacted with N,N(')-disuccinimidyl carbonate (DSC) to produce succinimide-terminated PLAF-NHS and PLGF-NHS macromers. The macromers were self-assembled by dialysis to form NPs. The amphiphilic PLEOF macromer was used as the surfactant to stabilize the NPs in the process of self-assembly. 1-(2-pyridylazo)-2-naphthol (PAN) was used as a model small molecule for encapsulation in PLAF or PLGF NPs and bovine serum albumin (BSA) was used as a model protein for conjugation to PLAF-NHS and PLGF-NHS NPs. The profile of release of the encapsulated PAN from PLAF and PLGF NPs was non-linear and consisted of a burst release followed by a period of sustained release. The release profile for BSA, conjugated to PLAF-NHS and PLGF-NHS NPs, was linear up to complete degradation of the NPs. PLGF and PLAF NPs degraded in 15 and 28 days, respectively, while PLGF-NHS and PLAF-NHS NPs degraded in 25 and 38 days, which demonstrated that the release was dominated by erosion of the matrix. PLAF-NHS and PLGF-NHS NPs are potentially useful as carriers for sustained in situ release of protein drugs.  相似文献   
50.
Fermentation of wine is a complex microbial reaction, which involves the sequential development of various species of yeasts and lactic acid bacteria. Of these, yeasts are the main group responsible for alcoholic fermentation. The aim of this work was to study, under industrial conditions, the evolution of yeast populations and to describe the individual evolution of the most important yeasts during three spontaneous fermentations of Malbec musts from Argentina. This work shows the significant participation of non-Saccharomyces yeasts during spontaneous fermentation of musts, with the ubiquitous presence of three main species: Kloeckera apiculata, Candida stellata and Metschnikowia pulcherrima.  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