全文获取类型
收费全文 | 1354篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 35篇 |
建筑科学 | 19篇 |
矿业工程 | 2篇 |
能源动力 | 2篇 |
轻工业 | 21篇 |
水利工程 | 14篇 |
无线电 | 8篇 |
一般工业技术 | 19篇 |
冶金工业 | 1229篇 |
原子能技术 | 1篇 |
自动化技术 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 31篇 |
1998年 | 332篇 |
1997年 | 231篇 |
1996年 | 161篇 |
1995年 | 110篇 |
1994年 | 60篇 |
1993年 | 75篇 |
1992年 | 13篇 |
1991年 | 23篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 48篇 |
1976年 | 94篇 |
排序方式: 共有1361条查询结果,搜索用时 312 毫秒
941.
Amygdalae of patients with Alzheimer's disease (AD), Parkinson's disease, Down's syndrome, diffuse Lewy body disease or a combination of these diseases were probed with antibodies to neurofilament proteins as well as with Lewy body (LB)- and paired helical filament-specific antibodies. The results indicate that the amygdala is severely affected by the accumulation of both neurofibrillary tangles (NFTs) and LBs in most cases of the diseases mentioned above, and that amygdala LBs have a similar epitope composition to that of LBs in the brain stem and cerebral cortex. While large numbers of both LBs and NFTs were seen in different neurons within the amygdala, these two lesions frequently occurred together in the same neurons of the amygdala. These findings are in contrast to other sites that accumulate LBs and NFTs, but rarely both lesions in the same neuron. Thus, amygdala neurons may be selectively vulnerable to developing both LBs and NFTs, and these inclusions may play a role in the massive degeneration of these neurons in AD and LB disorders of the elderly. 相似文献
942.
G Christie A Barton B Bolognese DR Buckle RM Cook MJ Hansbury GP Harper LA Marshall ME McCord K Moulder PR Murdock SM Seal VM Spackman BJ Weston RJ Mayer 《Canadian Metallurgical Quarterly》1997,27(12):3228-3235
CD23, the low-affinity IgE receptor, is up-regulated on interleukin (IL)-4-stimulated B cells and monocytes, with a concomitant increase in the release of soluble fragments of CD23 (sCD23) into the medium by proteolytic processing of the surface-bound intact CD23. The effect of inhibition of the processing of CD23 on IgE production in human and mouse cells and in a mouse model in vivo was evaluated. CD23 processing to sCD23 from RPMI 8866 (a human Epstein-Barr virus-transformed B cell line) cell membranes was inhibited by a broad-spectrum matrix-metalloprotease inhibitor, batimastat, with an IC50 of 0.15 microM. Batimastat also inhibited CD23 processing in whole RPMI 8866 cells as well as in IL-4-stimulated purified human monocytes with similar IC50. Batimastat inhibited IgE production from IL-4/anti-CD40-stimulated human tonsil B cells as well as mouse splenic B cells in a manner consistent with inhibition of CD23 processing. Release of soluble fragments of CD23 in the cell supernatants of tonsil B cells was inhibited over the concentration range of 1-10 microM batimastat and intact cell surface CD23 was increased on mouse splenic B cells in the presence of these concentrations of batimastat. IgE production of IL-4-stimulated human peripheral blood mononuclear cells was also blocked by 1-10 microM batimastat, again with comparable inhibition of sCD23 release over the same concentration range. Finally, in a mouse model of IgE production, batimastat inhibited IgE production in response to ovalbumin challenge as determined by serum IgE levels. Taken together, the data support a role of CD23 in IgE production and point to CD23 processing to sCD23 as a therapeutically relevant control point in the regulation of IgE synthesis. 相似文献
943.
MF Zinkovskií RM Vitovskií VM Beshliaga PV Pavlov SM Zinkovskaia 《Canadian Metallurgical Quarterly》1997,19(2):3-7
The results of a study carried out on 90 subjects exposed to vibratory trauma of the hand-arm compared to a non-risk control group of 54 subjects are reported. All subjects underwent a medical and neurological examination and Doppler ultrasound of the upper limbs, plethysmography of the hands, electromyography of the bilateral median nerve area and T.T.T. (Thermal Threshold Tester) evaluation of the thermal threshold, were performed. Workers exposed to risks show a higher threshold for hot/cold sensitivity compared to those not exposed. This increase is earlier compared to the onset of vascular and neurophysiological changes detected by plethysmography, Doppler ultrasound and electromyography. Thermal threshold evaluation by T.T.T. would seem to be a useful test for monitoring workers exposed to vibrations. 相似文献
944.
Thresholds for the detection of a tone added in-phase to the carrier of a fully modulated SAM tone were measured. In some conditions the signal was added to a single SAM tone, and in other conditions the signal was added to the sum of three or more SAM tones. Level equalization ensured that the addition of the tonal signal did not lead to increases in energy. When multiple SAM tone maskers were used, a small number of reproducible maskers were tested, each masker being composed of SAM tones with a variety of relative modulator phases. The maskers were either fixed across intervals and trials, roved across trials but fixed across intervals, or randomly chosen across both intervals and trials. The frequency separation between the signal-centered and off-frequency SAM tones was also varied. For small signal-centered/off-frequency SAM tone frequency separations, a separation ratio of 1.3, thresholds in the fixed condition depend on the relative modulator phases, and a simple mixture model reasonably predicted thresholds in the roving condition based on thresholds in the fixed condition for two of the three observers. For signal-centered/off-frequency SAM tone frequency separation factor of 1.68, effects of relative modulator phases were not obtained. Thresholds in the target-alone condition were generally superior to thresholds measured with the comodulated masker. Comodulated thresholds were better than target-alone thresholds only when level equalization was not used, and so the addition of the signal led to increases in level. 相似文献
945.
946.
947.
AP Kuznetsov IP Shmelev AM Demidov BV Efimov VM Shubko 《Canadian Metallurgical Quarterly》1996,(4):467-471
Analysis of the content of radionuclides 137Cs and 90Sr in the benthofauna was carried out in the region of location of the nuclear submarine Komsomolets according to the materials of the 33rd voyage of RV Akademik Mstislav Keldysh (1994). No significant excess of the technogenic activity over the natural radioactivity was found in all ecological (trophic) groups of bottom animals. At the same time the content of 90Sr in the fauna of stations closer to the submarine was higher than at more remote stations. 相似文献
948.
Ten-year risk of false positive screening mammograms and clinical breast examinations 总被引:1,自引:0,他引:1
JG Elmore MB Barton VM Moceri S Polk PJ Arena SW Fletcher 《Canadian Metallurgical Quarterly》1998,338(16):1089-1096
BACKGROUND: The cumulative risk of a false positive result from a breast-cancer screening test is unknown. METHODS: We performed a 10-year retrospective cohort study of breast-cancer screening and diagnostic evaluations among 2400 women who were 40 to 69 years old at study entry. Mammograms or clinical breast examinations that were interpreted as indeterminate, aroused a suspicion of cancer, or prompted recommendations for additional workup in women in whom breast cancer was not diagnosed within the next year were considered to be false positive tests. RESULTS: A total of 9762 screening mammograms and 10,905 screening clinical breast examinations were performed, for a median of 4 mammograms and 5 clinical breast examinations per woman over the 10-year period. Of the women who were screened, 23.8 percent had at least one false positive mammogram, 13.4 percent had at least one false positive breast examination, and 31.7 percent had at least one false positive result for either test. The estimated cumulative risk of a false positive result was 49.1 percent (95 percent confidence interval, 40.3 to 64.1 percent) after 10 mammograms and 22.3 percent (95 percent confidence interval, 19.2 to 27.5 percent) after 10 clinical breast examinations. The false positive tests led to 870 outpatient appointments, 539 diagnostic mammograms, 186 ultrasound examinations, 188 biopsies, and 1 hospitalization. We estimate that among women who do not have breast cancer, 18.6 percent (95 percent confidence interval, 9.8 to 41.2 percent) will undergo a biopsy after 10 mammograms, and 6.2 percent (95 percent confidence interval, 3.7 to 11.2 percent) after 10 clinical breast examinations. For every 100 dollars spent for screening, an additional 33 dollars was spent to evaluate the false positive results. CONCLUSIONS: Over 10 years, one third of women screened had an abnormal test result that required additional evaluation, even though no breast cancer was present. Techniques are needed to decrease false positive results while maintaining high sensitivity. Physicians should educate women about the risk of a false positive result from a screening test for breast cancer. 相似文献
949.
VM Tishchenko 《Canadian Metallurgical Quarterly》1998,24(6):465-467
Thirty-two patients suffering from migraine without aura were assessed during in interictal period to evaluate the contribution of cytokines to the pathophysiology of migraine. To this end, plasma levels of IFN-gamma, IL-4, IL-5, and IL-10 were measured by enzyme-linked immunosorbent assay (ELISA) techniques. Plasma levels of both IFN-gamma and IL-10 were not increased in the patients and did not differ significantly from healthy controls. Of interest, we observed a strong increase of IL-5 levels in 84.3% as well as increased IL-4 levels in 37.5% of patients with migraine without aura. These results suggests a preferential enhancement of some Th2-type cytokines, and may support the growing arguments of an immunoallergic mechanism in the pathophysiology of migraine. 相似文献
950.