全文获取类型
收费全文 | 662篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 17篇 |
机械仪表 | 2篇 |
建筑科学 | 2篇 |
能源动力 | 8篇 |
轻工业 | 7篇 |
无线电 | 14篇 |
一般工业技术 | 17篇 |
冶金工业 | 577篇 |
原子能技术 | 1篇 |
自动化技术 | 17篇 |
出版年
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 18篇 |
1998年 | 153篇 |
1997年 | 121篇 |
1996年 | 61篇 |
1995年 | 46篇 |
1994年 | 34篇 |
1993年 | 29篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 31篇 |
1976年 | 36篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有663条查询结果,搜索用时 15 毫秒
51.
To determine how the patterns of inpatient hospital care for HIV-infected patients have evolved in recent years, we analyzed data obtained from a statewide hospital discharge database from Maryland for the years 1988, 1990, and 1992. For each of these years, we compared demography, diagnoses, lengths of stay, use of the intensive care unit, third-party payer, and hospital charges (inflation-adjusted to 1992 dollars). HIV-infected patients accounted for 0.42% of all Maryland's hospital admissions in 1988, 0.68% in 1990, and 1.1% in 1992, with progressively more women and African-Americans hospitalized. Average lengths of stay fell from 11.7 days (1988) to 10.7 days (1990) and 9.5 days (1992) (p < 0.0001). Average charges per admission fell from $11,634 (1988) to $9,938 (1990) and $8,618 (1992) (p < 0.0001). Medicare or Medicaid paid for 50.9% of hospital admissions in 1988, 56.8% in 1990, and 66.8% in 1992 (p < 0.001). In-hospital mortality rates (7.8% in 1988, 7.9% in 1990, and 7.7% in 1992; p = 0.783) were stable, as was severity of illness. P. carinii pneumonia (PCP) was the most common principal diagnosis, but it declined in prevalence from 13.6% in 1988 to 9.1% in 1992 (p < 0.0001). Principal diagnoses of other opportunistic infections remained stable (8.0% in 1988, 9.9% in 1990, 8.6% in 1992; p = 0.90), as did other nonopportunistic infections (32.8% in 1988, 27.2% in 1990, and 30.0% in 1992; p = 0.16). Non-PCP pneumonias increased from 7.6% (1988) to 10.2% (1992) (p < 0.0001). Substance abuse as a principal or secondary diagnosis increased from 30.9% (1988) to 34.3% (1992) (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
52.
AB Abdul-Karim AD Barnes IS Bevan AJ Howie D Adu HF Ross C Raykundalia D Catty 《Canadian Metallurgical Quarterly》1995,3(3):192-202
Several studies have addressed the possible importance of anti-epithelial cell antibodies in kidney transplantation using the A549 cell line as an in vitro model. In this paper we report our results using for the first time an enzyme-linked immunosorbent assay (ELISA) to detect the anti-A549 cell antibodies. Sera from 129 kidney transplant patients were tested for IgM anti-epithelial cell antibodies directed against the A549 cell line prior to transplantation; only three sera were positive (2.3%). 101 of these patients were then followed-up post-transplantation; sera were collected routinely at 2, 6 and 12 weeks and at the time of rejection episodes. All samples were also tested for cytomegalovirus (CMV) IgM antibodies. Sixteen patients developed anti-A549 IgM antibodies, and there was no correlation with acute graft rejection. Anti-epithelial antibodies showed no binding to sections of normal kidney or biopsies of rejected kidneys. Eleven patients were positive for anti-CMV IgM antibodies. In nine cases both IgM anti-A549 and IgM anti-CMV antibodies were found, which was a highly significant association (p < 0.001). Analysis of A549 cellular proteins by immunoblotting gave evidence for the presence of CMV polypeptides in the cell lysate. Electron-microscopic examination of A549 cell preparations revealed intracellular particles which were compatible in size with CMV. Polymerase chain reaction analysis confirmed the presence of a specific CMV DNA sequence in A549 cells of several batches from different sources. Our data strongly suggest that the A549 cell line used in several published reports is infected with CMV and that in the majority of cases the anti-A549 'anti-epithelial' antibodies found in renal transplant patients are anti-CMV antibodies. 相似文献
53.
Arylsulfate sulfotransferase purified from Eubacterium A-44 has higher specific activity than the enzymes from Klebsiella K-36 and Haemophilus K-12. Propylparaben and butylparaben were good substrates among several parabens. The antibacterial activity of parabens was reduced by the sulfation of the phenolic hydroxy group. Tyrosine-containing peptides, kyotorphin, enkephalin and cholecystokinin non-sulfate, were effective as acceptor substrates by A-44, K-36 and K-12 sulfotransferases. 相似文献
54.
The role of intramuscular botulinum toxin A in the treatment of 26 children with cerebral palsy was evaluated. The indication for injection was the presence of a dynamic contracture of lower-limb muscles interfering with positioning or walking. Spastic target muscles were identified by clinical examination and, in ambulant children, by gait analysis. Between 50 and 320 units of botulinum toxin were injected into each muscle group to a total dose of 100 to 400 units per child. The effects of injection were monitored by repeated clinical examination and gait analysis. There were no clinically detectable systemic side-effects, and all but one patient had a reduction in tone, which occurred within three days and persisted for two to four months. There were significant improvements in ambulatory status and in sagittal-plane kinematics. In some cases these gains persisted after the tone-reducing effects of the toxin had worn off. 相似文献
55.
SV Varha OH Reznikov IS Turchyn VM Demchenko OP Potikha PV Sinitsyn LV Tarasenko LV Cha?kovs'ka 《Canadian Metallurgical Quarterly》1994,40(5-6):105-109
The effect exerted by transplantation of the 5 day culture of testicles from newly born piglets on the hypogonadal state of mature X-ray irradiated (3 Gy) rats was studied. It has been found that a month after transplantation (two months after irradiation) the hypogonadal state disappeared for a while, which is confirmed by normalization of the weight of seminal vesicles, content of testosterone and biologically active lutropine, restoration of the reproductive function of rats. No significant changes in steroidogenesis activity have been found, which proves a substituent character of transplantation. The effect disappears three months later but certain restoration of the content of nucleic acids in the testicles is observed. 相似文献
56.
57.
IS Efimova A Salminen P Pohjanjoki J Lapinniemi NN Magretova BS Cooperman A Goldman R Lahti AA Baykov 《Canadian Metallurgical Quarterly》1999,274(6):3294-3299
Recent crystallographic studies on Escherichia coli inorganic pyrophosphatase (E-PPase) have identified three Mg2+ ions/enzyme hexamer in water-filled cavities formed by Asn24, Ala25, and Asp26 at the trimer-trimer interface (Kankare, J., Salminen, T., Lahti, R., Cooperman, B., Baykov, A. A., and Goldman, A. (1996) Biochemistry 35, 4670-4677). Here we show that D26S and D26N substitutions decrease the stoichiometry of tight Mg2+ binding to E-PPase by approximately 0.5 mol/mol monomer and increase hexamer stability in acidic medium. Mg2+ markedly decelerates the dissociation of enzyme hexamer into trimers at pH 5.0 and accelerates hexamer formation from trimers at pH 7.2 with wild type E-PPase and the N24D variant, in contrast to the D26S and D26N variants, when little or no effect is seen. The catalytic parameters describing the dependences of enzyme activity on substrate and Mg2+ concentrations are of the same magnitude for wild type E-PPase and the three variants. The affinity of the intertrimer site for Mg2+ at pH 7.2 is intermediate between those of two Mg2+ binding sites found in the E-PPase active site. It is concluded that the metal ion binding site found at the trimer-trimer interface of E-PPase is a high affinity site whose occupancy by Mg2+ greatly stabilizes the enzyme hexamer but has little effect on catalysis. 相似文献
58.
R Manfredini M Gallerani F Portaluppi R Salmi F Chierici A Tassi E Rizzioli P Notarstefano IS Risichella AM Mirizio C Fersini 《Canadian Metallurgical Quarterly》1996,37(6):829-836
Convincing evidence is now available suggesting that several unfavorable cardiovascular events respect a well-defined diurnal pattern in their occurrence. In particular, ischemic heart disease has been widely investigated, and many data indicate a constellation of underlying risk factors whose temporal coincidence might act as triggering factors in the occurrence of acute events. In this paper, the recent knowledge concerning both epidemiology of ischemic heart disease and potentially favoring factors are reviewed from a chronobiological point of view. 相似文献
59.
Multimodal evoked potentials in patients with trigeminal neuralgia are analyzed in the paper. The comprehensive studies of cortical trigeminal somatosensory evoked potentials, visual evoked potentials, and brainstem auditory evoked potentials have revealed their changes that are indicative of the impaired central mechanisms of afferentation in patients with trigeminal abnormality. The findings are discussed in the light of the theory of generator mechanisms of neuropathological pain syndromes. 相似文献
60.
p53 mutations, a tumor suppressor gene located on chromosome 17p, are the most common genetic alterations found in human cancers. Although the p53 expression or mutation has been investigated in a variety of cancers there have been very few studies in extrahepatic bile duct cancers. In this study, we investigated the immunohistochemical expression of p53 in formalin fixed paraffin embedded archival specimens of 36 extrahepatic bile duct cancers in which p53 expression was found in eighteen (50%) cases. There was no significant difference in age, gender, size of tumor, histologic grade, extent of tumor involvement, lymph node metastasis and tumor resectability according to p53 immunoreactivity. Comparison of survival duration according to p53 expression showed no significant difference. In conclusion, we reported 50 percent of p53 expression in extrahepatic bile duct cancers by immunohistochemical staining and we found no prognostic significance of p53 expression in dinicopathologic parameters. 相似文献