全文获取类型
收费全文 | 2400篇 |
免费 | 14篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 56篇 |
金属工艺 | 3篇 |
机械仪表 | 1篇 |
建筑科学 | 13篇 |
能源动力 | 14篇 |
轻工业 | 36篇 |
水利工程 | 1篇 |
石油天然气 | 6篇 |
无线电 | 45篇 |
一般工业技术 | 41篇 |
冶金工业 | 2161篇 |
原子能技术 | 1篇 |
自动化技术 | 43篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 9篇 |
2013年 | 19篇 |
2012年 | 21篇 |
2011年 | 18篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 4篇 |
1999年 | 69篇 |
1998年 | 628篇 |
1997年 | 365篇 |
1996年 | 268篇 |
1995年 | 160篇 |
1994年 | 120篇 |
1993年 | 127篇 |
1992年 | 22篇 |
1991年 | 34篇 |
1990年 | 26篇 |
1989年 | 39篇 |
1988年 | 43篇 |
1987年 | 38篇 |
1986年 | 27篇 |
1985年 | 35篇 |
1983年 | 4篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 19篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 40篇 |
1976年 | 88篇 |
1975年 | 2篇 |
1969年 | 1篇 |
1966年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有2424条查询结果,搜索用时 15 毫秒
991.
992.
PW Hermans SK Saha WJ van Leeuwen HA Verbrugh A van Belkum WH Goessens 《Canadian Metallurgical Quarterly》1996,34(6):1373-1379
Seventy-eight Salmonella typhi strains isolated in 1994 and 1995 from patients living in Dhaka, Bangladesh, were subjected to phage typing, ribotyping, IS200 fingerprinting, and PCR fingerprinting. The collection displayed a high degree of genetic homogeneity, because restricted numbers of phage types and DNA fingerprints were observed. A significant number of the S. typhi strains (67%) were demonstrated to be multiple drug resistant (MDR). The vast majority of the MDR strains were resistant to chloramphenicol, ampicillin, trimethoprim, streptomycin, sulfamethoxazole, and tetracycline (R type CATmSSuT), a resistance phenotype that has also frequently been observed in India. Only two strains displayed a distinct MDR phenotype, R type AT-mSSuT. Pulsed-field gel electrophoresis demonstrated the presence of large plasmids exclusively in the MDR strains of both R types. The plasmids present in the S. typhi strains of R type CATmSSuT could be conjugated to Escherichia coli and resulted in the complete transfer of the MDR phenotype. PCR fingerprinting allowed discrimination of MDR and susceptible strains. The DNA fragments enabling discrimination of MDR and susceptible S. typhi strains by PCR were useful genetic markers for identifying MDR encoded by large plasmids of the H1 incompatibility group. 相似文献
993.
994.
SK Joseph SV Ryan S Pierson D Renard-Rooney AP Thomas 《Canadian Metallurgical Quarterly》1995,270(8):3588-3593
A number of thiol-reactive agents induce repetitive Ca2+ spiking in cells by a mechanism thought to involve sensitization of the inositol 1,4,5-trisphosphate receptor (IP3R). To further define the basis of this interaction, we have studied the effect of several thiol-reactive agents on [3H]IP3 binding, IP3-gated channel activity, and conformation of the IP3R in membranes from hepatocytes, cultured WB rat liver epithelial cells, and cerebellum microsomes. At 4 degrees C, the organomercurial thiol-reactive agent mersalyl markedly stimulates (3-4fold) [3H]IP3 binding to permeabilized hepatocytes. The closely related molecule, thimerosal, has only a small stimulatory effect under these conditions, and GSSG or N-ethylmaleimide are without effect. The stimulatory effect of mersalyl was associated with a decrease in Kd of the IP3R with no change in Bmax. Mersalyl was without effect on detergent-solubilized hepatocyte binding sites or on the [3H]IP3 binding activity of cerebellum microsomes. In contrast to thimerosal, which potentiates IP3-mediated Ca2+ release, mersalyl blocked IP3-gated Ca2+ channels. Mersalyl pretreatment of WB membranes altered the pattern of immunoreactive receptor fragments generated upon subsequent cleavage of the receptor with proteinase K. This effect was not reproduced by thimerosal and was also not observed in experiments on cerebellum microsomes. We conclude that the WB cell and brain IP3 receptors are differently regulated by modification of thiol groups. Reaction of the WB cell IP3 receptor with mersalyl alters its conformation and modifies the accessibility of sites on the protein that are cleaved by proteinase K. In the presence of mersalyl, the receptor has high affinity for IP3 but is inactive as a Ca2+ channel. This contrasts with the high affinity receptor/active Ca2+ channel induced by thimerosal, suggesting that even closely related thiol agents may interact at different thiol groups. 相似文献
995.
Open versus stereotactic breast biopsy 总被引:1,自引:0,他引:1
RC Frazee JW Roberts RE Symmonds SK Snyder JC Hendricks RW Smith JB Harrison 《Canadian Metallurgical Quarterly》1996,172(5):491-3; discussion 494-5
BACKGROUND: Stereotactic breast biopsy has been developed as a less invasive means of performing biopsy for mammographic abnormalities. METHODS: From July 1994 through June 1995, 103 women with mammographic abnormalities requiring biopsy were prospectively evaluated. RESULTS: Fifty-one women had open biopsy, and 52 women had stereotactic biopsy. The average age in both groups was 60 years. Pathology revealed malignancy in 12% of stereotactic biopsies and 13% of open biopsies. Complications occurred in 6% of the open biopsies and 4% of the stereotactic biopsies and were limited to hematomas or seromas. The average cost was $2400 for open biopsy and $650 for stereotactic biopsy (P < 0.01). One hundred and one patients returned for a follow-up mammogram within 6 months, and 1 patient in each group required a second biopsy, which revealed benign pathology. A Patient Satisfaction Survey revealed no significant differences in patient satisfaction between the two types of procedures. CONCLUSION: There were no differences between open and stereotactic biopsies in regards to diagnostic accuracy, complications, or patient satisfaction. A significant difference was noted in charges during the time frame of our study. 相似文献
996.
O Marino Alarcón H Concho Lugo T Silva Larralte E Tauil Bsereni P Solano Nava D Machado A Chacón Pati?o 《Canadian Metallurgical Quarterly》1996,47(3):172-177
In the present study we measured the activities of the following enzymes: LDH (lactic dehydrogenase), beta-glucuronidase, acid maltase, phosphohexoseisomerase (PHI) and acid proteases in the gastric juice of patients with gastric cancer (n = 50) (Case Group), in endoscopically normal subjects (n = 50) and in subjects with different non tumor-like digestive pathologies (n = 55) (Control Groups). In the patients with gastric carcinoma we found a significant increase in LDH, beta-glucuronidase, PHI and acid maltase activities and a decreased activity of acid proteases. The results agree with previous findings from other workers. The variations of enzyme activities in gastric juice can help to differentiate between malignant and benign processes of the gastric mucosa. 相似文献
997.
998.
999.
It has been found, the 1 or 2 days exposure of animals to hypoxic hypoxia (during 4 hours every day; 32 mm Hg) leads to the decrease of acetylcholine level in rat heart, liver and pancreas tissues and to activation of succinate oxidation in rat liver mitochondria. Beginning from the 7th day of hypoxia treatment the level of acetylcholine in the tissues was increasing and it was connected with the activation of NAD-dependent substrate alpha-ketoglutarate oxidation in the rat liver mitochondria and with the increase of the efficiency of oxidative phosphorylation. The effect increases to the 12-16-th day of animal adaptation. The important role of acetylcholine in formation of nonspecific adaptation reactions of organism to hypoxia has been shown. 相似文献
1000.