首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2172篇
  免费   0篇
  国内免费   1篇
电工技术   3篇
综合类   1篇
化学工业   10篇
金属工艺   1篇
机械仪表   38篇
建筑科学   5篇
能源动力   1篇
轻工业   87篇
水利工程   1篇
无线电   5篇
一般工业技术   4篇
冶金工业   2010篇
自动化技术   7篇
  2021年   2篇
  2019年   2篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2013年   3篇
  2012年   1篇
  2011年   2篇
  2010年   6篇
  2009年   9篇
  2008年   7篇
  2007年   8篇
  2006年   12篇
  2005年   9篇
  2004年   3篇
  2003年   12篇
  2002年   13篇
  2001年   7篇
  2000年   17篇
  1999年   75篇
  1998年   603篇
  1997年   355篇
  1996年   222篇
  1995年   139篇
  1994年   99篇
  1993年   121篇
  1992年   13篇
  1991年   20篇
  1990年   15篇
  1989年   17篇
  1988年   25篇
  1987年   15篇
  1986年   17篇
  1985年   17篇
  1984年   1篇
  1983年   8篇
  1982年   8篇
  1981年   19篇
  1980年   27篇
  1978年   6篇
  1977年   66篇
  1976年   160篇
  1975年   3篇
  1973年   1篇
  1970年   1篇
  1964年   1篇
  1955年   3篇
排序方式: 共有2173条查询结果,搜索用时 31 毫秒
31.
We report a case of typical chronic eosinophilic pneumonia (CEP), in a female of 27 years-old suffering bronchial asthma light. Although the initial answer to the treatment with steroids was satisfactory, the patient develop difficult to control asthma (DCA). DCA is a clinical situation which requires careful investigation of several potential factors which can be solved. We suggest a protocol of treatment for patients affected with DCA.  相似文献   
32.
BACKGROUND: X-linked severe combined immunodeficiency (SCIDXI) is an inherited immune defect which leads to death in infancy from severe infections. The defect is caused by mutations of the IL-2RG gene that encodes for the common gamma chain shared by several cytokine receptors. The disease is characterised by lack of T and NK cells with normal numbers of B cells. SCIDXI can be cured by bone marrow transplantation (BMT) or prevented by abortion after prenatal diagnosis. METHODS: A male fetus was diagnosed as having SCIDXI by molecular, immunophenotypic, and functional analyses. The fetus was injected intraperitoneally under ultrasound guidance with CD34 haematopoietic progenitor cells purified from paternal bone marrow and T-cell depleted by E rosetting. Chimerism analysis was by HLA-DQ alpha typing and gamma-chain staining on cord blood. FINDINGS: A healthy 3.6 kg boy was delivered by caesarean section at 38 weeks of gestation with no clinical or laboratory signs of graft-versus-host disease. Engraftment of donor-derived CD2 cells was found at birth. At 3.5 months of age the infant is well and his T-cell counts and function are normal. INTERPRETATION: In-utero transplantation of haematopoietic progenitor cells allowed immune reconstitution of a fetus with SCIDXI and may be an alternative to elective abortion. Our report should encourage applications of this method to other inherited disorders curable by BMT.  相似文献   
33.
Two forms of mitochondrial adrenodoxin reductase from bovine adrenals and recombinant bovine adrenodoxin and adrenodoxin reductase expressed in Escherichia coli were isolated, purified to homogeneity and biochemically characterized. Recombinant adrenodoxin reductase was expressed as a single polypeptide; its retention time on DEAE-Fractogel coincides with the second form (F2) of the mitochondrial reductase. Two enzyme forms have similar adrenodoxin reductase activities in two types of systems comprising either cytochrome c or cytochrome P-450 (11 beta) as the terminal electron acceptor. Adrenodoxin and each of two reductase forms were cross-linked using 1-ethyl-3-(dimethyl-amino-propyl)carbodiimide. An effective two-step method for the purification of the active heterologous cross-linked complexes is suggested that enables purification of the functional complexes to homogeneity. The cross-linked bimolecular complex of adrenodoxin and adrenodoxin reductase was crystallized for the first time.  相似文献   
34.
35.
36.
OBJECTIVE: To identify any clinical and pathologic features of treatment modalities that are predictive of outcome in patients with epithelioid sarcoma, a rare slow-growing soft tissue tumor most commonly occurring in the distal extremities of young adults. DESIGN: We reviewed the institutional files for cases of epithelioid sarcoma for the period 1956 to 1991 and analyzed the effect of various factors on survival. MATERIAL AND METHODS: Fifty-five cases of epithelioid sarcoma were found, and the relevant clinical, pathologic, treatment, follow-up, and outcome features were assessed. RESULTS: All tumors were treated initially by operative resection. The recurrence rate progressively decreased with increasing aggressiveness of the initial operation; however, no difference was noted in metastatic rate. Overall, the recurrence rate was 38% and the metastatic rate was 47%. At the end of a mean follow-up of 102 months, 69% of patients had no evidence of disease, 27% had died of the disease, and 4% were alive with disease. Increasing tumor size, necrosis of more than 30%, and vascular invasion correlated significantly with a worse prognosis. CONCLUSION: Epithelioid sarcoma should be considered a malignant neoplasm with a significant potential for aggressive behavior, and close follow-up of affected patients should be maintained for many years. Initial treatment should be aggressive in an attempt to prevent recurrence.  相似文献   
37.
A chromosomally encoded 66-kDa protein (P66) of Borrelia spp. that cause Lyme disease has previously been shown to be associated with the spirochetal outer membrane. A topological model of P66 predicts a surface-exposed fragment which links the N- and C-terminal intramembranous domains of the protein (J. Bunikis, L. Noppa, and S. Bergstr?m, FEMS Microbiol. Lett. 131:139-145, 1995). In the present study, an immunogenic determinant of P66 was identified by a comparison of the immunoreactivities of different fragments of P66 generated either by proteolytic treatment of intact spirochetes or as recombinant proteins expressed in Escherichia coli. The immune response to P66 during natural infection was found to be directed against the predicted surface domain which comprises amino acids at positions 454 through 491. A sequence comparison revealed considerable polymorphism of the surface domains of P66 proteins of different Lyme disease-causing Borrelia species. Five sequence patterns of this domain were observed in the B. garinii strains studied. In contrast, sequences of the relevant part of P66 of the B. afzelii and B. burgdorferi sensu stricto isolates studied were identical within the respective species. In immunoblotting, 5 of 17 (29.4%) sera from North American patients with early disseminated or persistent Lyme disease reacted against P66 of B. burgdorferi sensu stricto B31. These sera, however, failed to recognize P66 of B. afzelii and B. garinii, as well as an analog of P66 in the relapsing fever agent, B. hermsii. In conclusion, the topological model of P66 is supported by the demonstration of an apparent surface localization of an immunoreactive domain of this protein. Furthermore, analogous to the plasmid-encoded borrelial outer surface proteins, the predicted surface-exposed portion of chromosomally encoded P66 appears to be antigenically heterogenous.  相似文献   
38.
39.
beta-Glucosidase of indigo plant (Polygonum tinctorium) has a high substrate specificity for indican (indoxyl beta-D-glucoside). To examine the localization of this beta-glucosidase, we fractionated the cells of the leaves and analysed them immunocytochemically. Immunoelectron micrographs with specific antibodies against the beta-glucosidase clearly showed that the beta-glucosidase was localized in the stroma of the chloroplasts in mesophyll cells, but not in the thylakoid membrane. Chloroplasts were isolated from the crude homogenate of the fresh leaves by Percoll density gradient centrifugation and then subjected to suborganellar fractionation. beta-Glucosidase activity was specifically detected in the stromal fraction, but not in the thylakoid membrane. This was also supported by the result of an immunoblot of the fraction with anti-beta-glucosidase antibodies. The beta-glucosidase was immunocytochemically localized in the chloroplasts of mesophyll cells, but not in any chloroplasts in marginal cells of the vascular bundle or epidermal cells; ribulose 1,5-bisphosphate carboxylase (Rubisco), a typical stromal protein, was observed in all chloroplasts in these cells. These results suggest that beta-glucosidase is tissue specific in its expression in the leaves of the indigo plant.  相似文献   
40.
OBJECTIVES--(1) to evaluate regional cerebral blood flow (rCBF) with single photon emission computed tomography and 99mTc-hexamethylpropyleneamine oxime in patients with the idiopathic adult hydrocephalus syndrome (IAHS); (2) to examine regional cerebral blood flow (rCBF), gait, and psychometric functions before and after CSF removal (CSF tap test); (3) to assess abnormalities in subcortical white matter by MRI. METHODS--Thirty one patients fulfilling the criteria for IAHS (according to history and clinical and neuroradiological examination) were studied. Quantified gait measurements, psychometric testing, and rCBF before and after removal of CSF were obtained. Pressure of CSF and CSF outflow conductance were investigated with a constant pressure infusion method. Brain MRI was used to quantify the severity of white matter lesions and periventricular hyperintensities. In IAHS a widespread rCBF hypoperfusion pattern was depicted, with a caudal frontal and temporal grey matter and subcortical white matter reduction of rCBF as the dominant feature. Removal of CSF was not accompanied by a concomitant increase in rCBF. Significant white matter lesions were detected only in a minority of patients by MRI. An altered CSF hydrodynamic state with a higher CSF pressure and lower conductance was confirmed. IAHS is characterised by an abnormal CSF hydrodynamic state, associated with a widespread rCBF reduction with preference for subcortical white matter and frontal-temporal cortical regions. Furthermore in most patients MRI did not show white matter changes suggestive of a coexistent subcortical arteriosclerotic encephalopathy. At least in the idiopathic group of patients with AHS, measurements of rCBF before and after temporary relief of the CSF hydrodynamic disturbance will not provide additional information that would be helpful in the preoperative evaluation but is suggestive of a preserved autoregulation of rCBF.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号