全文获取类型
收费全文 | 3384篇 |
免费 | 53篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 23篇 |
综合类 | 2篇 |
化学工业 | 291篇 |
金属工艺 | 39篇 |
机械仪表 | 34篇 |
建筑科学 | 80篇 |
矿业工程 | 6篇 |
能源动力 | 61篇 |
轻工业 | 263篇 |
水利工程 | 20篇 |
石油天然气 | 3篇 |
无线电 | 233篇 |
一般工业技术 | 274篇 |
冶金工业 | 1884篇 |
原子能技术 | 23篇 |
自动化技术 | 203篇 |
出版年
2023年 | 12篇 |
2022年 | 16篇 |
2021年 | 21篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 25篇 |
2017年 | 25篇 |
2016年 | 37篇 |
2015年 | 29篇 |
2014年 | 23篇 |
2013年 | 80篇 |
2012年 | 52篇 |
2011年 | 101篇 |
2010年 | 64篇 |
2009年 | 68篇 |
2008年 | 90篇 |
2007年 | 92篇 |
2006年 | 97篇 |
2005年 | 76篇 |
2004年 | 55篇 |
2003年 | 56篇 |
2002年 | 68篇 |
2001年 | 60篇 |
2000年 | 36篇 |
1999年 | 86篇 |
1998年 | 500篇 |
1997年 | 325篇 |
1996年 | 204篇 |
1995年 | 129篇 |
1994年 | 115篇 |
1993年 | 119篇 |
1992年 | 41篇 |
1991年 | 57篇 |
1990年 | 42篇 |
1989年 | 55篇 |
1988年 | 37篇 |
1987年 | 38篇 |
1986年 | 31篇 |
1985年 | 38篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 27篇 |
1981年 | 18篇 |
1980年 | 31篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 57篇 |
1976年 | 127篇 |
1975年 | 14篇 |
1973年 | 10篇 |
排序方式: 共有3439条查询结果,搜索用时 0 毫秒
61.
WL Olszewski 《Canadian Metallurgical Quarterly》1996,29(3):126-131
Dermatolymphangioadenitis (DLA) is a common and serious complication of obstructive peripheral lymphedema. The clinical characteristics of acute DLA are local tenderness and erythema of the skin, sometimes red streaks along the distribution of the superficial lymphatics and enlarged inguinal lymph nodes. Systemic symptoms include malaise, fever and chills. In its subacute or latent form, only skin involvement is observed. Each episode of DLA is commonly followed by worsening of leg swelling. Numerous clinical studies suggest that administration of antibiotic drugs interrupt the acute episodes and prevent their recurrence. We investigated the clinical course of lymphedema with respect to the prevalence of DLA in patients receiving injections of long-acting penicillin (benzathine penicillin). Forty-five randomly selected patients with obstructive lymphedema of the lower limbs were included in an open clinical trial. The inclusion criteria was stage II-IV lymphedema of postsurgical, posttraumatic, and postdermatitis type with at least 3 previous episodes of DLA. Benzathine penicillin (PCN) was given after the last presenting episode of DLA in a dose of 1,200,000 u, intramuscularly at 3-week intervals, for at least one year. Each patient was reevaluated at 3-month intervals. They were instructed in early diagnosis of DLA and reported promptly to the responsible senior surgeon with prodrome symptoms of recurrent DLA. The duration of lymphedema before initiation of therapy was 7 months to 40 years and the frequency of DLA was 1-6 episodes per year. PCN administration lasted for at least one year but was extended in all patients because of the tendency for recurrence of DLA after cessation of PCN injections. In 26 of these patients, PCN administration extended to over 5 years and in 2 over 10 years. Recurrent episodes of DLA occurred in the PCN-treated group during one year follow-up in only 4 of the 45 patients (9%). The frequency episodes in 3 patients with recurrent DLA was 1-2/year; in one patient, no positive effect of PCN therapy was observed. There were no apparent side effects of long-term PCN therapy. These data, although evaluated without a placebo group, suggest that long-term PCN administration decreases the frequency of DLA attacks and furthermore provide justification for carrying out a double-blind randomly placebo-controlled clinical trial of the efficacy of prophylactic antibiotic drug treatment in forestalling DLA episodes. 相似文献
62.
The effective thermal conductivity eff has been measured for 1.6 K for mixtures with 10–6–2. Both eff and the derived impurity mass diffusion coefficient Diso show an unexpected dependence on the height h of the fluid layer. A scaled representation of Diso leads to a purely phenomenological model involving an effective length scale, proportional to X–1 and temperature independent. The relations so obtained are consistent with the observations as well as with the observed transition curve QC(X) to non-linear behavior. 相似文献
63.
Jan Haas Karen S. Frese Farbod Sedaghat-Hamedani Elham Kayvanpour Rewati Tappu Rouven Nietsch Oguz Firat Tugrul Michael Wisdom Carsten Dietrich Ali Amr Tanja Weis Torsten Niederdrnk Michael P. Murphy Thomas Krieg Marcus Drr Uwe Vlker Jens Fielitz Norbert Frey Stephan B. Felix Andreas Keller Hugo A. Katus Benjamin Meder 《International journal of molecular sciences》2021,22(4)
With more than 25 million people affected, heart failure (HF) is a global threat. As energy production pathways are known to play a pivotal role in HF, we sought here to identify key metabolic changes in ischemic- and non-ischemic HF by using a multi-OMICS approach. Serum metabolites and mRNAseq and epigenetic DNA methylation profiles were analyzed from blood and left ventricular heart biopsy specimens of the same individuals. In total we collected serum from n = 82 patients with Dilated Cardiomyopathy (DCM) and n = 51 controls in the screening stage. We identified several metabolites involved in glycolysis and citric acid cycle to be elevated up to 5.7-fold in DCM (p = 1.7 × 10−6). Interestingly, cardiac mRNA and epigenetic changes of genes encoding rate-limiting enzymes of these pathways could also be found and validated in our second stage of metabolite assessment in n = 52 DCM, n = 39 ischemic HF and n = 57 controls. In conclusion, we identified a new set of metabolomic biomarkers for HF. We were able to identify underlying biological cascades that potentially represent suitable intervention targets. 相似文献
64.
High resolution XPS analysis of chemical functionalised multi-wall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNT) was done with ESCA300 (overall instrument resolution of 0.35 eV). Information to the degree of functionalisation was ascertained by argon ion bombardment of the samples followed by XPS analysis to detect the functional groups, the percentage atomic concentration of various elements present and whether or not the detected functional groups imposed a chemical shift on the CNT atoms. The results show that true chemical functionalisation was achieved and by argon ion bombardment these functional groups can be altered relative to the C 1s carbon atoms of the CNT. The choice of chemicals used for functionalisation, the techniques employed and the types of nanotubes treated are important factors in chemical characterisation. The carbon atom on the nanotube ring to which the functional group (atom) is bonded, the chirality of the CNT, the electronegativity of the functional group, the bond type and whether the CNT is single-wall or multi-wall, or cut (short) could play a role in determining the chemical shift on the CNTs atoms. These investigations are relevant to chemical functionalisation of carbon nanotubes for various applications for example DNA sensors and other biomedical sensors. 相似文献
65.
T.I.T. Okpalugo P. Papakonstantinou H. Murphy J. Mclaughlin N.M.D Brown 《Carbon》2005,43(14):2951-2959
The surface compositional and any structural changes that occur on carbon nanotubes using air-atmospheric pressure dielectric barrier discharge (APDBD) for functionalization are investigated employing Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and neutron diffraction techniques. Atmospheric pressure plasmas (APP) are suggested to be particularly suitable for functionalization of aligned nanotubes, where wet chemical manipulation could damage or even destroy the highly desirable vertical alignment. In this work a detailed experimental study elucidating the effects of APDBD plasma treatment parameters (e.g. power density, discharge composition, inter-electrode gap and treatment time) on the electronic structure, physical, and chemical behaviour of carbon nanotubes has been conducted. In an atmospheric air we find an optimal oxidative functionalization of CNTs in our DBD system within few seconds (<5 s) at a discharge power of ∼0.5 kW. This investigation may find useful application as functionalization technique for CNT engineered devices and sensors. 相似文献
66.
R. B. Jones C. J. Murphy L. H. Sperling M. Farber S. P. Harris G. E. Manser 《应用聚合物科学杂志》1985,30(1):95-109
The thermal decomposition behavior of poly[3,3-bis(ethoxymethyl)oxetane] (polyBEMO) was examined and compared to the decomposition of poly(ethylene oxide) (PEO) and poly(tetramethylene oxide) (polyTHF). Differential scanning calorimetric (DSC) studies as a function of heating rates and at constant temperature as a function of time yielded activation energies of 45–50 kcal/mol, characteristic of polyether decomposition. First-order decomposition kinetics were found. The reaction is endothermic, with a heat of decomposition of 18.6 kcal/mol. Effusion mass spectroscopy on polyBEMO showed major peaks at 112, 140, 168, and 174 amu. A mechanism is proposed in which the thermal scission of the ether bonds in both the polymer chain and in the appendanges initiates the decomposition. The main decomposition reaction for polyBEMO can be written as where the appendages and main chain are cleaved in an unknown order. 相似文献
67.
68.
Flaking and extrusion as mechanical treatments for enzyme-assisted aqueous extraction of oil from soybeans 总被引:6,自引:7,他引:6
B. P. Lamsal P. A. Murphy L. A. Johnson 《Journal of the American Oil Chemists' Society》2006,83(11):973-979
Flaking and extruding dehulled soybeans were evaluated as a means of enhancing oil extraction efficiency during enzyme-assisted
aqueous processing of soybeans. Cellulase, protease, and their combination were evaluated for effectiveness in achieving high
oil extraction recovery from extruded flakes. Aqueous extraction of extruded full-fat soy flakes gave 68% recovery of the
total available oil without using enzymes. A 0.5% wt/wt protease treatment after flaking and extruding dehulled soybeans increased
oil extraction recovery to 88% of the total available oil. Flaking and extruding enhanced protease hydrolysis of proteins
freeing more oil. Treating extruded flakes with cellulase, however, did not enhance oil extraction either alone or in combination
with protease. Discrepancies in oil extraction recoveries were encountered when merely considering crude free fat because
some oil became bound to denatured protein during extrusion and/or sample drying. Bound fat was unavailable for determination
by using the hexane extraction method, but was accounted for by using the acid hydrolysis method for total oil determination.
Oil extraction recovery from extruded soybean flakes was affected by oil determination methods, which was not the case for
unextruded full-fat soy flour. 相似文献
69.
A range of powdered ethyl‐vinyl acetate (EVA) copolymers and poly(vinyl chloride) (PVC) formulations were compounded at PVC:EVA ratios of 100:0, 60:40, 50:50, 40:60, and 0:100. Two grades of EVA with 20% and 27% of vinyl acetate (VAc) (EVA I and EVA II) and two grades of PVC with K values of 56 and 71 (PVC I and PVC II) were used in the investigation. Mechanical analysis was performed on injection molded samples of these blends, and the results showed that the tensile and flexural moduli decreased significantly with increasing EVA concentration. Rheological analysis was performed by using dual capillary rheometry, and the results showed only slight changes in shear viscosity with increasing EVA content, even at lower shear rates. Dynamic mechanical thermal analysis showed partial miscib lity of the PVC and EVA over the range of concentrations studied. 相似文献
70.
Induced resistance in cotton (Gossypium hirsutum) foliage and squares to herbivory by Helicoverpa zea (Lepidoptera: Noctuidae) is reported in this study. Induced resistance was indicated by decreased larval growth when larvae fed on previously damaged foliage or squares compared to the controls. Herbivory caused a significant decline in host nutritional quality as shown by a reduction in protein and most amino acids in both foliage and squares. Peroxidase, ascorbate oxidase, and diamine oxidase activities increased in both damaged foliage and squares, whereas levels of the nutritional antioxidant, ascorbate, were depressed after larval feeding. Larval feeding also markedly enhanced lipoxygenase activity and lipid peroxides in square tissues. Moreover, feeding damage altered the quantitative levels of phenolic compounds in foliage and squares. These results indicate a significant shift in the oxidative status of cotton plants following herbivory as indicated by increased oxidative enzyme activity, decreased levels of the nutritional antioxidant ascorbate, and increased levels of phenolic prooxidants (i.e., chlorogenic acid) and lipid peroxides. 相似文献