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排序方式: 共有670条查询结果,搜索用时 15 毫秒
61.
Zah C.E. Lin P.S.D. Favire F. Pathak B. Bhat R. Caneau C. Gozdz A.S. Andreadakis N.C. Koza M.A. Lee T.P. Wu T.C. Lau K.Y. 《Electronics letters》1992,28(9):824-826
The wide gain spectrum of compressive-strained multiquantum-well active layers was used to fabricate 20-wavelength distributed-feedback laser arrays. A record wide-wavelength span of 131 nm in the 1.5 mu m wavelength region was demonstrated. The maximum intrinsic modulation response, measured by a parasitic-free optical modulation technique, reaches 16 GHz.<> 相似文献
62.
63.
S. K. Mishra L. C. Pathak S. K. Ray S. Kal D. Bhattacharya S. K. Lahiri K. L. Chopra 《Journal of Superconductivity》1992,5(5):445-449
Microbridges of YBa2Cu3O7 thin films have been fabricated by conventional photolithography and wet chemical etching using EDTA, and by the lift-off lithography technique. The variation of etch rate with etch time, etchant temperature, and post-deposition sintering temperature has been studied. It has been shown that both techniques are useful for film patterning. However, an additional sintering step is necessary for the chemically etched sample to regain the original film properties. An order of increase in critical current density is observed for the patterned film. 相似文献
64.
Bis(dipyridophenazine)(2‐(2′‐pyridyl)pyrimidine‐4‐carboxylic acid)ruthenium(II) Hexafluorophosphate: A Lesson in Stubbornness
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Dr. Tanmaya Joshi Vanessa Pierroz Priv.‐Doz. Dr. Stefano Ferrari Prof. Dr. Gilles Gasser 《ChemMedChem》2014,9(7):1419-1427
Ruthenium complexes are currently considered to be among the most promising alternatives to platinum anticancer drugs. In this work, thirteen structural analogues and organelle/receptor‐targeting peptide bioconjugates of a cytotoxic bis(dppz)‐RuII complex [Ru(dppz)2(CppH)](PF6)2 ( 1 ) were prepared, characterized, and assessed for their cytotoxicity and cellular localization (CppH=2‐(2′‐pyridyl)pyrimidine‐4‐carboxylic acid; dppz=dipyrido[3,2‐a:2′,3′‐c]phenazine). It was observed that structural modifications (lipophilicity, charge, and size‐based) result in the cytotoxic potency of 1 being compromised. Confocal microscopy studies revealed that unlike 1 , the screened complexes/bioconjugates do not have a preferential accumulation in mitochondria. The results of this important structure–activity relationship strongly support our initial hypothesis that accumulation in mitochondria is crucial for 1 to exert its cytotoxic action. 相似文献
65.
Greeshma V. Patel Vaibhav B. Patel Abhishek Pathak Sadhana J. Rajput 《Drug development and industrial pharmacy》2014,40(1):80-91
Context: Nanosuspensions (NSs) of poorly water-soluble drugs are known to increase the oral bioavailability.Objectives: The purpose of this study was to develop NS of efavirenz (EFV) and to investigate its potential in enhancing the oral bioavailability of EFV.Materials and methods: EFV NS was prepared using the media milling technique. The Box–Behnken design was used for optimization of the factors affecting EFV NS. Sodium lauryl sulfate and PVP K30 were used to stabilize the NS. Freeze-dried NS was completely re-dispersed with double-distilled filtered water.Results: Mean particle size and zeta potential of the optimized NS were found to be 320.4?±?3.62?nm and –32.8?±?0.4 mV, respectively. X-ray diffraction and differential scanning calorimetric analysis indicated no phase transitions. Rate and extent of drug dissolution in the dissolution medium for NS was significantly higher compared to marketed formulation. The parallel artificial membrane permeability assay revealed that NS successfully enhanced the permeation of EFV. Results of in situ absorption studies showed a significant difference in absorption parameters such as Ka, t1/2 and uptake percentages between lyophilized NS and marketed formulation of EFV. Oral bioavailability of EFV in rabbits resulting from NS was increased by 2.19-fold compared to the marketed formulation.Conclusion: Thus, it can be concluded that NS formulation of EFV can provide improved oral bioavailability due to enhanced solubility, dissolution velocity, permeability and hence absorption. 相似文献
66.
Chhabra G Chuttani K Mishra AK Pathak K 《Drug development and industrial pharmacy》2011,37(8):907-916
Nanoemulsion (NE) of amlodipine besilate (AB) was developed by spontaneous emulsification method with the aim to enhance the solubility and oral bioavailability of AB and to achieve localized delivery of drug at target site. Pseudoternary phase diagrams were constructed to identify the NE region. The selected formulations from NE region were subjected to droplet size analysis, partitioning study and in vitro drug release. The partition coefficient was calculated and correlated with percent dissolution efficiency as a tool to predict in vitro drug release from NEs. The release of drug from NEs was significantly higher (p < 0.01) than the marketed tablet formulation. The optimal formulation contained 15% Labrafil M, 35% [Tween 80: ethanol (2:1)], and 50% by weight aqueous phase (NE3) was characterized by transmission electron microscopy (TEM) and for thermodynamic stability. The pharmacokinetics and biodistribution studies of the optimized radiolabeled formulation (99mTc-labeled) in mice (p.o.) demonstrated a relative bioavailability of 475% against AB suspension. In almost all the tested organs, the uptake of AB from NE was significantly higher (p < 0.05) than AB suspension especially in heart with a drug targeting index of 44.1%, also confirming the efficacy of nanosized formulation at therapeutic site. A three times increase in the overall residence time of NE further signifies the advantage of NEs as drug carriers for enhancing bioavailability of AB. 相似文献
67.
V. Pathak Tayfun Babadagli N.R. Edmunds 《Journal of Petroleum Science and Engineering》2011,78(3-4):637-645
Thermal and miscible methods are commonly used for in situ recovery of heavy oil and bitumen. Both techniques have their own limitations and benefits. However, these methods can be combined by co-injecting solvent with steam or injecting solvent into a pre-heated reservoir. The current work was undertaken to study the performance of solvents at higher temperatures for heavy oil/bitumen recovery. Glass bead packs and Berea sandstone cores were used in the experiments to represent different types of pore structures, porosity and permeability. After saturating with heavy oil, the samples were exposed to the vapor of paraffinic solvents (propane and butane) at a temperature above the boiling point of the solvent, and a constant pressure of 1500 kPa. A mechanical convection oven was used to maintain constant temperature across the setup. The setup was designed in such a way that a reasonably long sample (up to 30 cm) can be tested to analyze the gravity effect. The oil recovered from each of these experiments was collected using a specifically designed collection system and analyzed for composition, viscosity and asphaltene content.The final amount of oil recovered in each case (recovery factor but not extraction rate) was also analyzed and the quantity and nature of asphaltene precipitated with each of the tested solvents under the prevailing temperature and pressure of the experiment was reported. Optimal conditions for each solvent type were identified for the highest ultimate recovery. It was observed that recovery decreased with increasing temperature and pressure of the system for both solvents, and that the best results were found when experimental temperature is only slightly higher than the saturation temperature of the solvent used. It was also noticed that butane diluted the oil more than propane which resulted in lower asphaltene content and viscosity of oil produced with butane as a solvent. 相似文献
68.
T. Saud D.P. SinghT.K. Mandal Ranu GadiH. Pathak M. SaxenaS.K. Sharma R. GautamA. Mukherjee R.P. Bhatnagar 《Biomass & bioenergy》2011,35(2):932-941
Biomass is widely used as energy source in rural households in India. Biomass samples and socio-economic data have been collected at district level in the rural areas of Indo-Gangetic plain (IGP), India to determine the emissions of trace gases and aerosols from domestic fuels. Dung cake, fuelwood and crop residue are main sources of energy in rural areas of the IGP. Dung cake is the major domestic fuel (80-90%) in the rural areas of Delhi, Punjab, Haryana, Uttar Pradesh, Bihar and West Bengal, whereas, 99% of rural households in Uttarakhand use wood as the main energy source. Using crop production data and usage of crop residues as energy, new consumption values have been estimated (21.13 Mt). Present information on the domestic fuel usage would be helpful in determining budgets estimates of trace gases and aerosols for India. 相似文献
69.
Kinetic modelling and microbial community assessment of anaerobic biphasic fixed film bioreactor treating distillery spent wash 总被引:1,自引:0,他引:1
Anaerobic digestion, microbial community structure and kinetics were studied in a biphasic continuously fed, upflow anaerobic fixed film reactor treating high strength distillery wastewater. Treatment efficiency of the bioreactor was investigated at different hydraulic retention times (HRT) and organic loading rates (OLR 5-20 kg COD m−3 d−1). Applying the modified Stover-Kincannon model to the reactor, the maximum removal rate constant (Umax) and saturation value constant (KB) were found to be 2 kg m−3 d−1 and 1.69 kg m−3 d−1 respectively. Bacterial community structures of acidogenic and methanogenic reactors were assessed using culture-independent analyses. Sequencing of 16S rRNA genes exhibited a total of 123 distinct operational taxonomic units (OTUs) comprising 49 from acidogenic reactor and 74 (28 of eubacteria and 46 of archaea) from methanogenic reactor. The findings reveal the role of Lactobacillus sp. (Firmicutes) as dominant acid producing organisms in acidogenic reactor and Methanoculleus sp. (Euryarchaeotes) as foremost methanogens in methanogenic reactor. 相似文献
70.
Pathak P Kapil U Yajnik CS Kapoor SK Dwivedi SN Singh R 《Food and nutrition bulletin》2007,28(4):435-438
BACKGROUND: Iron, folate, and vitamin B12 deficiencies have adverse effects on pregnancy outcome. In India, data on the concomitant prevalence of these deficiencies among pregnant women are meager. OBJECTIVE: We conducted a community-based study to assess the prevalence of deficiencies of iron, folate, and vitamin B12 among pregnant women in a rural block of Haryana State. METHODS: The study was approved by the ethics committee of the All India Institute of Medical Sciences, New Delhi. A total of 283 pregnant women were enrolled in the study. After oral informed consent had been obtained from the women, blood was drawn from the antecubital vein for estimation of the levels of serum ferritin by enzyme-linked immunosorbent assay (levels < 12 ng/ mL were considered as indicative of poor iron stores); serum folate was determined by radioimmunoassay (levels <3 ng/mL were considered as indicative of poor folate stores); and serum vitamin B12 was estimated by the microbiologic method (levels < 200 pg/mL were considered as indicative of poor vitamin B12 stores). RESULTS: The results indicated that 67.7%, 26.3%, and 74.1% of the women had poor iron, folate, and vitamin B12 stores, respectively. Concomitant deficiencies of iron, folate, and vitamin B12 occurred in 16.2% of the women. We found that 59.9% of the women were consuming less than 75% of the recommended daily caloric allowance (2175 kcal), indicating an overall poor food intake. This could be one of the predominant reasons for poor iron, folate, and vitamin B12 stores among the women. CONCLUSIONS: Our findings suggest that apart from iron and folate, vitamin B12 deficiencies may play an important role in causing anemia. 相似文献