全文获取类型
收费全文 | 931篇 |
免费 | 41篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 296篇 |
金属工艺 | 10篇 |
机械仪表 | 14篇 |
建筑科学 | 31篇 |
能源动力 | 29篇 |
轻工业 | 95篇 |
水利工程 | 3篇 |
石油天然气 | 5篇 |
无线电 | 69篇 |
一般工业技术 | 126篇 |
冶金工业 | 138篇 |
原子能技术 | 5篇 |
自动化技术 | 145篇 |
出版年
2023年 | 6篇 |
2022年 | 40篇 |
2021年 | 59篇 |
2020年 | 30篇 |
2019年 | 28篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 37篇 |
2015年 | 24篇 |
2014年 | 39篇 |
2013年 | 59篇 |
2012年 | 52篇 |
2011年 | 48篇 |
2010年 | 46篇 |
2009年 | 38篇 |
2008年 | 30篇 |
2007年 | 30篇 |
2006年 | 23篇 |
2005年 | 21篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 46篇 |
1997年 | 30篇 |
1996年 | 21篇 |
1995年 | 5篇 |
1994年 | 14篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有972条查询结果,搜索用时 15 毫秒
81.
Leena Maunula Agnieszka Kaupke Petra Vasickova Kirsi Söderberg Iwona Kozyra Sava Lazic Wim H.M. van der Poel Martijn Bouwknegt Saskia Rutjes Kris A. Willems Rita Moloney Martin D'Agostino Ana Maria de Roda Husman Carl-Henrik von Bonsdorff Artur Rzeżutka Ivo Pavlik Tamas Petrovic Nigel Cook 《International journal of food microbiology》2013
In recent years, numerous foodborne outbreaks due to consumption of berry fruit contaminated by human enteric viruses have been reported. This European multinational study investigated possible contamination routes by monitoring the entire food chain for a panel of human and animal enteric viruses. 相似文献
82.
The positive ion-molecule reactions in the mixtures of hydrogen sulfide and methane have been examined by means of quadrupole mass spectrometer with the high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. For each mixture major bimolecular ion-molecule reactions have been identified in the total pressure range from 0.7 to 33.3 Pa. The electron energy for all measurements was fixed at 300 eV and the repeller potential was maintained at 5 V. Relative intensities of ion currents for the observed ions C+, CH+, CH2+, CH3+, CH4+, CH5+, C2H3+, C2H4+, C2H5+, S+, HS+, H2S+, H3S+, H334S+, CHS+, CH3S+, S2+, HS2+ and H2S2+ were determined as a function of total gas pressure inside the ion source collision chamber, repeller potential and concentration of methane in the mixture. 相似文献
83.
Restriction enzyme fragmentation pattern (REFP) analysis was used to recognise Staphylococcus aureus strain variation in naturally occurring bovine subclinical mastitis. Multiple colony REFP analysis identified eight distinct strains of S. aureus in addition to the original strains A and B that were infused via the intramammary route, indicating that individual quarters of the udder may be colonised simultaneously by more than one strain of S. aureus. Examination of multiple colonies per milk sample may benefit bacterial strain recognition as an epidemiological tool in mastitis investigations. The dynamics of intramammary infection were determined using a novel double crossover experimental challenge. Quarters remained persistently infected for several weeks following challenge in all four cows, irrespective of the challenge strain. This indicated that no alteration of the original subclinical infection, including the possible induction of clearance of the quarters infected with S. aureus, or replacement of the original strain by the infused strain was induced by challenge. The persistent subclinical infection in all four animals supports previous reports on the chronicity of S. aureus intramammary infection in dairy cows. 相似文献
84.
Suyeon Kim Carla Silva Andrea Zille Carmen Lopez Dmitry V Evtuguin Artur Cavaco‐Paulo 《Polymer International》2009,58(8):863-868
BACKGROUND: The ‘double function’ of laccase, from the ascomycete Myceliophthora, to depolymerise/polymerise lignin was studied in this work. A lignosulfonate (LS) compound was oxidised by enzymatic action and several techniques were applied to measure the polymeric changes obtained. This study was focused on the attachment level of the oxidised LS at the flax surface. RESULTS: Modified solutions were studied in terms of surface charge. Zeta potential values obtained showed an increase of polymerisation after several days of incubation. The change in molecular weight after LS polymerisation was detected using gel permeation chromatography. An increase of 1700 Da was achieved. Fourier transform infrared and UV‐visible spectroscopy techniques were applied and the results showed an increase of the degree of polymerisation. The colour strength of flax fabrics incubated with oxidised LS solutions was also measured and an increase of K/S (K, absorption coefficient; S, scattering coefficient) after enzymatic oxidation was observed. CONCLUSION: The oxidised lignin products obtained show good potential for use in natural surface modification of textile materials containing flavonoids. These findings have important practical implications for lignocellulosic fibre coloration, where new polymers can replace harsh chemicals in the textile industry. Copyright © 2009 Society of Chemical Industry 相似文献
85.
OBJECTIVE: To evaluate the costs and outcomes associated with the Health Education Board for Scotland's general public anti-smoking campaign during the developmental stage and its first year of operation. DESIGN: Cost information collected retrospectively was combined with prospectively collected effectiveness data. SUBJECTS: A panel of 970 adults were recruited from a 1-in-10 random sample of adult callers to the telephone helpline (Smokeline). Those who smoked were subsequently interviewed at three weeks, six months, and one year follow up. Information on smoking status at one year and time spent as a non-smoker was available for 587 members of the panel. MAIN OUTCOME MEASURES: Intermediate outcomes in the follow-up sample included a point prevalence and period prevalence measure of smoking cessation. Long-term outcomes were measured in terms of predicted reductions in mortality as a consequence of smoking cessation. RESULTS: At the 12- month point, 9.88% of individuals in the follow-up sample reported themselves as non-smokers and as having given up for at least six months in the previous year. Estimates of the cost per life-year saved as a result of the campaign range from 304 pounds sterling to 656 pounds sterling. CONCLUSIONS: Provided that the benefits of smoking cessation are broadly accurate, and the assumed level of quitting can be directly attributed to Smokeline, then this mass media-led anti- smoking campaign appears to have been cost effective.
相似文献
相似文献
86.
The product of the REF2 gene is required for optimal levels of endonucleolytic cleavage at the 3' ends of yeast mRNA, prior to the addition of a poly(A) tail. To test the role of the previously demonstrated nonspecific affinity of REF2 for RNA in this process, we have identified RNA binding mutants in vitro and tested them for function within the cell. One REF2 variant, with an internal deletion of 82 amino acids (269-350), displays a 10-fold reduction in RNA binding, yet still retains full levels of processing activity in vivo. Conversely, a series of carboxyl-terminal deletions that maintain full RNA binding capability have progressively decreasing activity. These results rule out a major role for the central RNA binding domain of REF2 in mRNA 3' end processing and demonstrate the importance of the carboxyl-terminal region. To ask if the stimulatory role of REF2 depends on interactions with other proteins, we used a two-hybrid screen to identify a new protein termed FIR1 (Factor Interacting with REF) encoded on chromosome V. FIR1 interacts with two independent regions of REF2, one of which (amino acids 268-345) overlaps the RNA binding domain and is dispensible for REF2 function, whereas the other (amino acids 391-533) is located within the critical carboxyl-terminus. As with REF2, FIR1 has a small but detectable role in influencing the efficiency of poly(A) site use. Yeast strains containing a disrupted FIR1 gene are slightly less efficient in the use of cryptic poly(A) sites located within the lacZ portion of an ACT1-lacZ reporter construct. Likewise, a double delta ref2, delta fir1 mutant is more defective in processing of a reporter CYC1 poly(A) site than delta ref2 alone. This synergistic response provides additional support for the interaction of FIR1 with REF2 in vivo, and suggests that a number of gene products may be involved in regulating the cleavage reaction in yeast. 相似文献
87.
The effect of selected parameters of formation on properties of alginate/Ca2+/oligochitosan capsules
Artur Bartkowiak Sawomir Lisiecki Gorka Orive Jose Luis Pedraz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(4):511-518
Optimization of the technological parameters affecting the mechanical properties and permeability of capsules is essential to produce capsules with improved properties for cell immobilization. In the present paper, the effect of different parameters on the technological properties of alginate/Ca2+/oligochitosan capsules has been investigated. The correct adjustment of the alginate concentration in the polymer matrix and the oligochitosan molar mass, concentration and coating time, have been found to be key parameters in obtaining porous and mechanically stable alginate/Ca2+/oligochitosan capsules. Results showed that an increase in the coating time and concentration of the alginate generated more stable capsules with a reduced membrane cut‐off. Furthermore, we have established some correlations between capsule properties and the effectiveness of chitosan binding within the capsule's membrane. Data addressed herein could be a valid tool to fabricate optimized alginate/Ca2+/oligochitosan capsules with a potential for use in cell immobilization technology. Copyright © 2006 Society of Chemical Industry 相似文献
88.
89.
90.
Sabine Heublein Doris Mayr Klaus Friese Maria Cristina Jarrin-Franco Miriam Lenhard Artur Mayerhofer Udo Jeschke 《International journal of molecular sciences》2014,15(9):15161-15172
Ovarian granulosa cell tumors (GCTs) are thought to arise from cells of the ovarian follicle and comprise a rare entity of ovarian masses. We recently identified the G-protein-coupled estrogen receptor (GPER/GPR30) to be present in granulosa cells, to be regulated by gonadotropins in epithelial ovarian cancer and to be differentially expressed throughout folliculogenesis. Thus, supposing a possible role of GPER in GCTs, this study aimed to analyze GPER in GCTs. GPER immunoreactivity in GCTs (n = 26; n (primary diagnosis) = 15, n (recurrence) = 11) was studied and correlated with the main clinicopathological variables. Positive GPER staining was identified in 53.8% (14/26) of GCTs and there was no significant relation of GPER with tumor size or lymph node status. Those cases presenting with strong GPER intensity at primary diagnosis showed a significant reduced overall survival (p = 0.002). Due to the fact that GPER is regulated by estrogens, as well as gonadotropins, GPER may also be affected by endocrine therapies applied to GCT patients. Moreover, with our data supposing GPER to be associated with GCT prognosis, GPER might be considered as a possible confounder when assessing the efficacy of hormone-based therapeutic approaches in GCTs. 相似文献