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   799篇
  免费   25篇
  国内免费   4篇
电工技术   11篇
化学工业   165篇
金属工艺   22篇
机械仪表   27篇
建筑科学   13篇
能源动力   24篇
轻工业   86篇
水利工程   2篇
无线电   135篇
一般工业技术   171篇
冶金工业   74篇
自动化技术   98篇
  2024年   1篇
  2023年   2篇
  2022年   14篇
  2021年   13篇
  2020年   4篇
  2019年   8篇
  2018年   9篇
  2017年   13篇
  2016年   8篇
  2015年   9篇
  2014年   15篇
  2013年   60篇
  2012年   35篇
  2011年   33篇
  2010年   33篇
  2009年   38篇
  2008年   46篇
  2007年   57篇
  2006年   38篇
  2005年   28篇
  2004年   21篇
  2003年   29篇
  2002年   27篇
  2001年   18篇
  2000年   19篇
  1999年   21篇
  1998年   36篇
  1997年   29篇
  1996年   29篇
  1995年   19篇
  1994年   18篇
  1993年   14篇
  1992年   7篇
  1991年   7篇
  1990年   7篇
  1989年   8篇
  1988年   9篇
  1987年   7篇
  1986年   7篇
  1985年   7篇
  1984年   6篇
  1983年   2篇
  1982年   3篇
  1981年   1篇
  1980年   3篇
  1979年   2篇
  1977年   5篇
  1976年   3篇
排序方式: 共有828条查询结果,搜索用时 31 毫秒
91.
A sensitive reversed-phase high-performance liquid chromatographic method with ultraviolet detection was developed for the analysis of a new angiotensin II receptor antagonist, DuP 532 (L-694,492), in human plasma and urine. The analyte and internal standard are extracted from plasma and urine at a pH between 3.3 to 3.6 by liquid-liquid extraction and analyzed on a C6 column with ultraviolet detection at 254 nm. The mobile phase is composed of acetonitrile and phosphate buffer at pH 2.5. The limits of quantification are 6 and 7.5 ng/ml for plasma and urine, respectively.  相似文献   
92.
The recently proposed complementary operators method (COM) is applied to the beam propagation method (BPM). The spurious reflection using the COM can be several orders lower than that using other boundary conditions  相似文献   
93.
This paper deals with the function modules demanded for production control in a distributed cellular manufacturing system. Cells are the distributed components of any manufacturing system. A proposed multipassing distributed simulating scheduling system (MPDSSS) deals with the production control functions regarding process planning (working-cell selection), scheduling, rescheduling, and real-time dispatching. The process planning function aims at selecting a good route for each job. The multipassing scheduling aims at providing a scheduling bidding strategy in a distributed fashion. The rescheduling aims at dealing with the large-effort change of the system with updating the precedence schedule to run in a new manufacturing period. The real-time scheduling deals with the small-effort change of the system with a real-time dispatching rule. All the production controlling functions have been implemented in distributed fashions. A simulation experiment demonstrates that the proposed MPDSSS leads to good results in the following criteria: minimum mean flow time, minimum waiting time, maximum machine utilisation, and minimum imbalance of cell utilisation.Nomenclature {A} grouping set ofA i - A i function-identical set of celli - BC i the weighted bidding cost for the operation in celli - {C} performance criteria set - C i ith element of {C} - CU f avg average cell utilisation inA f - CU f max maximum cell utilisation inA f - CU i average cell utilisation of celli - CUmax maximum CU i - CUmin minimum CU i - {D} dispatching rule base - D i ith rule in {D} - EFT earliest finishing time - EFTmax maximum EFT - ICU f the imbalance of cell utilisation inA f - P m previously actual system performance for criterionC m - RC i rescheduling cost when using ruleD i - SC i improvement rate for system cost using ruleD i - SP a actual system performance - SP m preceding simulation performance of theC m with ruleD i - SP p ideally predictable system performance - SPD a actual system performance deviation - TICU i total imbalance of cell utilisation using ruleD i - W weighting factor  相似文献   
94.
A K-band (20 GHz) monolithic amplifier was developed and fabricated by adopting a low-/spl kappa/ benzocyclobutene (BCB) coplanar waveguide (CPW) line and InGaP-InGaAs doped-channel HFETs (DCFETs). This monolithic microwave integrated circuit (MMIC) utilizes a high impedance BCB CPW microstrip line (Z/sub 0/=70 /spl Omega/) for the biasing circuits, and a Z/sub 0/=50 /spl Omega/ line for the RF signal transmission. The low dielectric constant characteristic of the BCB interlayer is beneficial for a common-ground bridge process, which reduces the parasitics. The calculated loss tan/spl delta/ is 0.036 for the BCB at 20 GHz. The one-stage MMIC amplifier achieves an S/sub 21/ of 5 dB at 20 GHz, which is the first demonstration of the K-band InGaP-InGaAs DCFET monolithic circuit.  相似文献   
95.
Nonstoichiometric BaTiO3 PTCR type materials are investigated with various amounts of MnO2, Sb2O3 and MgO dopants. Specimens fired with a nonisothermal rate-controlled sintering profile exhibit a rather fine and uniform microstructure as compared to those processed by conventional sintering techniques. The temperature at which the resistivity anomaly begins is observed to decrease with Sb2O3 and MgO contents. The Curie point of BaTiO3-based ceramics can be altered by addition of Sb2O3, and the dielectric peak is maintained by the presence of MgO additive. Magnesium ions act as acceptors in the BaTiO2 lattice, while antimony ions as donors. The presence of magnesium compensates some of the antimony, hence the doped-BaTiO3 seminonductive region is pushed to higher contents.  相似文献   
96.
97.
It is difficult to achieve controlled cutting of elastic, mechanically fragile, and rapidly resealing mammalian cell membranes. Here, we report a photothermal nanoblade that utilizes a metallic nanostructure to harvest short laser pulse energy and convert it into a highly localized explosive vapor bubble, which rapidly punctures a lightly contacting cell membrane via high-speed fluidic flows and induced transient shear stress. The cavitation bubble pattern is controlled by the metallic structure configuration and laser pulse duration and energy. Integration of the metallic nanostructure with a micropipet, the nanoblade generates a micrometer-sized membrane access port for delivering highly concentrated cargo (5 × 10(8) live bacteria/mL) with high efficiency (46%) and cell viability (>90%) into mammalian cells. Additional biologic and inanimate cargo over 3-orders of magnitude in size including DNA, RNA, 200 nm polystyrene beads, to 2 μm bacteria have also been delivered into multiple mammalian cell types. Overall, the photothermal nanoblade is a new approach for delivering difficult cargo into mammalian cells.  相似文献   
98.
Chromatographic and spectroscopic methods used for the detection and quantification of triacylglycerol (TAG) species present in less common edible vegetable oils (almond, hazelnut, pumpkin seed, safflower, sesame, walnut, and wheatgerm oils) are reviewed. For these oils, as well as for thistle oil and high-oleic sunflower oil, for which no data exist on their TAG composition, both high-performance liquid chromatography (HPLC) and gas chromatography (GC) chromatographic plus spectrometric techniques have also been performed. Triacylglycerol comparison of the data found in the literature is also presented. Five fatty acyl moieties (palmitoyl-, stearoyl-, oleoyl-, linoleoyl-, and linolenoyl-) are found to mainly contribute to the formation of TAG species of the aforementioned edible vegetable oils, whereas six more (palmitoleoyl-, arachidoyl-, gadoleoyl-, heptadecenoyl-, margaroyl-, and erucoyl-) are reported as minors. Only 19 to 33 TAG make up the mass of these oils. These TAG are also found in most common edible oils, thus indicating a “uniformity” in the minor and main TAG composition of edible vegetable oils. Trioleoyl-glycerol predominates in almond (13.3-48.6%), hazelnut (35.3-57.9%), and high oleic sunflower (44.2% and 52.9%) oils, trilinoleoyl-glycerol in safflower (40.1-49.7%), thistle (36.9% and 46.0%), walnut (25.9-38.1%), and wheatgerm (15.7-33.0%) oils. Sesame and pumpkin seed oils are rich in dioleoyl-linoleoyl-glycerol (5.9-17.5%, 9.5% and 18.6%, respectively) and oleoyl-dilinoleoyl-glycerol (8.0-18.7% and 12.8-21.1%, respectively).  相似文献   
99.
100.
Endoscopic treatment of chronic pancreatitis has drawn benefits from endoscopic procedures previously described for the main bile duct. Endotherapy is developing throughout the world. Cyst drainage procedures certainly represent the largest step forward in that non-surgical approach, whatever it is either direct (through the stomach or the duodenum) or indirect through the papilla in the duodenum. This procedure gives similar results to surgery with a lower morbidity. Pancreatic duct drainage associated with stone clearance is feasible and provides good results which have not yet been compared with those obtained thanks to surgery. Nonetheless, when the duct is not widely dilated it has been proven to be a satisfactory alternative to surgery. By contrast, chronic cholestasis does not appear to be a good indication of endotherapy.  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