全文获取类型
收费全文 | 4002篇 |
免费 | 128篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 36篇 |
综合类 | 14篇 |
化学工业 | 1070篇 |
金属工艺 | 61篇 |
机械仪表 | 41篇 |
建筑科学 | 184篇 |
矿业工程 | 4篇 |
能源动力 | 56篇 |
轻工业 | 322篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 178篇 |
一般工业技术 | 677篇 |
冶金工业 | 1021篇 |
原子能技术 | 25篇 |
自动化技术 | 438篇 |
出版年
2023年 | 39篇 |
2022年 | 57篇 |
2021年 | 73篇 |
2020年 | 43篇 |
2019年 | 61篇 |
2018年 | 50篇 |
2017年 | 51篇 |
2016年 | 85篇 |
2015年 | 88篇 |
2014年 | 101篇 |
2013年 | 165篇 |
2012年 | 171篇 |
2011年 | 209篇 |
2010年 | 152篇 |
2009年 | 165篇 |
2008年 | 170篇 |
2007年 | 155篇 |
2006年 | 138篇 |
2005年 | 129篇 |
2004年 | 102篇 |
2003年 | 74篇 |
2002年 | 70篇 |
2001年 | 61篇 |
2000年 | 61篇 |
1999年 | 102篇 |
1998年 | 317篇 |
1997年 | 179篇 |
1996年 | 142篇 |
1995年 | 92篇 |
1994年 | 87篇 |
1993年 | 74篇 |
1992年 | 47篇 |
1991年 | 49篇 |
1990年 | 31篇 |
1989年 | 36篇 |
1988年 | 40篇 |
1987年 | 41篇 |
1986年 | 32篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 18篇 |
1982年 | 13篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 17篇 |
1977年 | 35篇 |
1976年 | 69篇 |
1975年 | 20篇 |
1974年 | 16篇 |
排序方式: 共有4132条查询结果,搜索用时 0 毫秒
1.
2.
The reduction of nitric oxide with ammonia on an unsupported iron oxide catalyst has been studied in a continuous-flow recycle reactor using simulated flue gas. The responses of the employed reactor system to step and pulse inputs of tracer indicate that the system could be regarded as a continuous stirred tank reactor (CSTR). Preliminary tests were carried out to determine the effect of temperature and particle size on the measured reaction rates. Additional experiments were performed in order to study the influence of oxygen and water concentration on these rates. A gas chromatographic system has been developed to analyze the gas components NO, N2O, NO2, NH3, H2O, O2, CO2 and N2. In addition, the concentrations of NO and NO2 were measured with a nondisperse infrared (NDUV/NDIR) analyzer. 相似文献
3.
4.
Scale formation is a difficulty encountered with water containing ions of sparingly soluble salts that can readily precipitate on heat transfer surfaces in evaporative concentration operations. Scale formation, hindering the heat transfer process, increases specific energy consumption and operating costs and causes frequent shut down of the evaporator for cleaning. The effects of changes in composition of the solution due to evaporation and CO2 release on the formation of crystalline scales in seawater evaporators are studied. A model that predicts the CO2 release is presented. The carbonate system in the salt solution on its whole flow path through the evaporator and the scaling (crystallization) tendency are described. Simulation results for different process configurations are shown and the differences are discussed, particularly with regard to the incrustation tendency. 相似文献
5.
Summary The Polymer Section of the Santa Barbara Workshop on Modeling of Materials is briefly reviewed. Motivation and need for modeling in polymer-based materials are outlined and the recommendations resulting from the workshop reported. 相似文献
6.
Purification of solvents containing air – Alternative methods. Different processes are used for the purification of solvents containing air: condensation, absorption, adsorption, combustion, membrane permeation, and biofilters or bioscrubbers. The processes will be explained by examples. The specifications required by “TA Luft” often cannot be reached only by condensation and membrane permeation. The success of absorption depends on the scrubbing liquid. Glycol ethers are useful scrubbing liquids – especially for chlorinated hydrocarbons. The choice of the process depends on the volume flow rate, the solvent concentration, and the kind of solvent. Recycling of the solvents reduces the costs of the process. 相似文献
7.
8.
The reactions of trans-2,5-dimethoxy-4′-aminostilbene with poly(maleic anhydride-co-methylvinyl ether) and trans-2,5-dimethoxy-4′-isocyanatostilbene with poly(oxy-1,4-phenyleneisopropylidene:1,4-phenyleneoxy-2-hydroxytrimethylene) yield polymeric systems which undergo rapid crosslinking upon short exposure to ultraviolet light. The extent of photocrosslinking as a function of exposure time was determined by the decrease of the trans-stilbene ultraviolet absorption at 350 nm. 相似文献
9.
S Ewig A Glasmacher B Ulrich K Wilhelm H Sch?fer KH Nachtsheim 《Canadian Metallurgical Quarterly》1998,114(2):444-451
STUDY OBJECTIVE: To determine predictors of mortality from pulmonary infiltrates in neutropenic patients with acute leukemia during chemotherapy, and the significance of those factors related to the underlying malignancy and its therapy as well as of those related to the severity of the illness associated with pulmonary infiltrates. DESIGN: A historical cohort study. SETTING: A university teaching hospital and tertiary referral center. PATIENTS AND METHODS: Overall, 53 patients with neutropenia during chemotherapy and with first episodes of pulmonary infiltrates during a 4-year period were studied. Prognostic analysis included 38 variables. Multivariate analyses were performed by logistic regression. RESULTS: The survival rate from pneumonia was 57% (30/53). The following eight parameters were significantly associated with death in univariate analysis: comorbidity present; development of "late" pulmonary infiltrates (> or = 14 days after hospital admission); heart rate > or = 100 beats/min; a ratio heart rate/systolic blood pressure (HR/SBP) > or = 1.2; urea nitrogen > 7 mmol/L; radiographic score > or = 3; neutropenia < 1.0x10(9)/L at the treatment end point; and failed complete remission. In a multivariate model including only parameters available at diagnosis of pulmonary infiltrates, the presence of a ratio HR/SBP > or = 1.2 and of a radiographic score > or = 3 remained independently associated with death. In a second model also including the evolutionary parameter neutropenia < or = 1.0x10(9)/L at the treatment end point, both parameters remained significant together with neutropenia <1.0x 10(9)/L at the treatment end point. The presence of a ratio HR/SBP > or = 1.2 was a strong marker of early death. CONCLUSION: Both therapy- and malignancy-associated neutropenia as well as the severity of illness associated with pulmonary infiltrates are independent prognostic factors. Patients with a ratio HR/SBP > or = 1.2 at diagnosis of pulmonary infiltrates suffer from potentially reversible acute illness, are at risk for early death and, therefore, may be appropriate candidates for treatment in an ICU. 相似文献
10.
Ulrich Schmatz Catherine Dubourdieu Oleg Lebedev Gerard Delabouglise Francois Weiss Jean-Pierre Senateur 《Journal of Low Temperature Physics》1996,105(5-6):1301-1306
Thin and thick YBCO Films have been grown by Aerosol Assisted as well as by thermal MOCVD. The Aerosol Assisted MOCVD technique allows the growth of YBCO films from a single liquid source at deposition rates of up to 10m/h.Transport measurements (I-V) on etched microbridges using a single pulse technique have been performed. The angular magnetic field dependence Jc() of the critical current density from Tc down to 50 K has been measured. Transport properties are reported and discussed with respect to the microstructural features as determined by X-ray diffraction and electron microscopy. 相似文献