全文获取类型
收费全文 | 6396篇 |
免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 29篇 |
建筑科学 | 3篇 |
能源动力 | 4篇 |
轻工业 | 5篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 3篇 |
一般工业技术 | 6篇 |
冶金工业 | 6332篇 |
自动化技术 | 8篇 |
出版年
2019年 | 1篇 |
2017年 | 1篇 |
2012年 | 1篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 3篇 |
1999年 | 179篇 |
1998年 | 2022篇 |
1997年 | 1130篇 |
1996年 | 726篇 |
1995年 | 370篇 |
1994年 | 327篇 |
1993年 | 385篇 |
1992年 | 41篇 |
1991年 | 93篇 |
1990年 | 68篇 |
1989年 | 77篇 |
1988年 | 76篇 |
1987年 | 84篇 |
1986年 | 72篇 |
1985年 | 69篇 |
1984年 | 3篇 |
1983年 | 12篇 |
1982年 | 34篇 |
1981年 | 44篇 |
1980年 | 38篇 |
1979年 | 2篇 |
1978年 | 17篇 |
1977年 | 158篇 |
1976年 | 317篇 |
1975年 | 13篇 |
1965年 | 1篇 |
1955年 | 7篇 |
排序方式: 共有6397条查询结果,搜索用时 15 毫秒
41.
Effects of growth hormone, insulin-like growth factor-I, and cortisol on periparturient antibody response profiles of dairy cattle 总被引:2,自引:0,他引:2
The objectives of this study were to determine hormone and antibody response profiles from the prepartum period to peak lactation, and evaluate potential immunomodulatory effects of the classic endocrine hormones, growth hormone (GH), insulin-like growth factor-I (IGF-I) and cortisol. Specifically, 33 Holstein cows were immunized with ovalbumin (OVA) and Escherichia coli J5 at weeks -8 and -3 prior to parturition. At parturition (week 0), cows received an additional immunization of OVA. Blood was collected at weeks -8, -3, 0, 3 and 6 relative to parturition and various samples were used to determine plasma hormone concentration, serum immunoglobulin (Ig), and specific antibody response to OVA and E. coli. Colostrum and milk samples were also collected post-parturition to monitor local immunoglobulin and antibody responses. Results indicated that not all periparturient cows exhibited depressed immune response, and that antibody response to OVA could be used to partition cows into 3 groups recognizing animals with sustained measurable antibody response before and after parturition (Group 1), animals which responded poorly to immunization at parturition (Group 2), and animals which did not respond to immunizations at week -3 or parturition (Group 3). Cows with the highest antibody response to OVA (Group 1) also tended (P < or = 0.10) to have the highest response to E. coli J5 at parturition and had the lowest incidence of disease, particularly mastitis. Antibody response to OVA measured in milk tended to be higher in Group 1 cows, particularly at week 0 (P < or = 0.06) compared to cows of Group 3. IGF-I was higher (P < or = 0.05) in cows of Group 1 than Group 3 at peak lactation (week 6). 相似文献
42.
JA Beatty JJ Callanan A Terry O Jarrett JC Neil 《Canadian Metallurgical Quarterly》1998,72(1):767-771
We describe the histopathological, immunohistochemical, and molecular characterization of a lymphoma arising in a 7-year-old cat following experimental infection with feline immunodeficiency virus (FIV). The tumor was high grade and of B-cell lineage. The transformed cell had an immature phenotype (CD79a+, CD79b-, CD21-, immunoglobulin heavy and light chain negative), confirmed by antigen receptor gene analysis, which showed germ line configuration. Single-copy, clonally integrated FIV provirus was detected in tumor genomic DNA. FIV p24 antigen was not detected in tumor cells by immunostaining. This study provides the first evidence that the feline lentivirus may play a direct role in cell transformation under certain circumstances. 相似文献
43.
BL Perlaza M Arévalo-Herrera K Brahimi G Quintero JC Palomino H Gras-Masse A Tartar P Druilhe S Herrera 《Canadian Metallurgical Quarterly》1998,66(7):3423-3428
Aotus lemurinus monkeys were immunized with pools of either lipid-tailed peptides injected in PBS or peptides in Montanide ISA-51, all derived from four Plasmodium falciparum pre-erythrocytic antigens, namely, LSA1, LSA3, SALSA, and STARP. These formulations were well tolerated. Their immunogenicity was demonstrated by the induction of both B- and T-cell responses to most of the peptides studied (of the 12, 10 induced antibody production, 9 induced T-cell proliferative responses, and all 12 induced gamma interferon secretion). Immune responses proved to be long lasting, since some were still detectable 210 days after immunization. Of particular importance is the fact that B- and T-cell responses elicited in this way by synthetic peptides were specific for native parasite proteins on P. falciparum sporozoites and liver stage parasites. 相似文献
44.
G Maya-Nu?ez JC Zenteno A Ulloa-Aguirre S Kofman-Alfaro JP Mendez 《Canadian Metallurgical Quarterly》1998,83(5):1650-1653
Kallmann's syndrome (KS) is defined by the association of hypogonadotropic hypogonadism and anosmia or hyposmia. Segregation analysis in familial cases has demonstrated diverse inheritance patterns, suggesting the existence of several genes regulating GnRH secretion. Genetic defects have been demonstrated in the KAL gene, located on the Xp22.3 region, explaining the X-linked form of the disease. We report molecular findings regarding the KAL gene in 12 unrelated males with X-linked KS. PCR of the 14 exons of the KAL gene was performed on genomic DNA. PCR products of all exons were purified and sequenced. Genetic defects in the KAL gene were found in 7 patients. One exhibits a deletion from exon 3 to exon 5. Six individuals present a previously unidentified missense mutation in exon 11, consisting of a G to A substitution at codon 514 (GAA to AAA). In the remaining 5 individuals, no mutations were observed. We also found three different polymorphic changes. The first one, in exon 2, had not been reported previously. The other two were located at exons 11 and 12. The deletion described, comprises only part (exon 5) of the coding region of the first fibronectin type III-like repeat of the KAL protein. The rest of the deletion comprises part of the conserved cysteine-rich N-terminal region that corresponds to the whey acidic protein motif. The same missense mutation was found in 6 of the 12 patients, indicating the possibility that it derived from a common ancestor or suggesting the presence of a hot spot in this region of the gene. 相似文献
45.
Estrogen withdrawal-induced human breast cancer tumour regression in nude mice is prevented by Bcl-2
MA Pratt S Krajewski M Menard M Krajewska H Macleod JC Reed 《Canadian Metallurgical Quarterly》1998,440(3):403-408
The purpose of this study was to assess the safety and efficacy of percutaneous transluminal cerebral balloon angioplasty (PTCBA) of extra- and intra-cranial arteries by investigating procedural outcome. Eighty haemodynamically significant extra- and intra-cranial lesions (% diameter stenosis > 70) in 74 clinically symptomatic patients were treated by elective and initial PTCBA between March 1991 and February 1996 and thereafter followed. Death, stroke, surgery, or repeated angioplasty of restenosis or new lesions were regarded as cerebral events after the initial PTCBA. The procedural and clinical success rates were 81 % (65 of 80) and 81 % (60 of 74), respectively. Progressively ischaemic symptoms disappeared completely after clinically successful dilatation. Angiographic restenosis rate at 3 months was 22 %(14 of 65). By life-table method, the death/stroke risk was 16 %, and any cerebral event risk was 49 % at 2 years following PTCBA, respectively. The most common of first cerebral events presented was repeated angioplasty of restenosis. In conclusion, PTCBA has great efficacy in decreasing recurrent neurological symptoms and produces a favourable short-term outcome, whereas restenosis limits long-term benefit. 相似文献
46.
Pitx2 participates in the late phase of the pathway controlling left-right asymmetry 总被引:1,自引:0,他引:1
ME Piedra JM Icardo M Albajar JC Rodriguez-Rey MA Ros 《Canadian Metallurgical Quarterly》1998,94(3):319-324
BACKGROUND: We have studied the role of the different MHC (RT1) subregions in acute natural killer (NK) cell-mediated bone marrow allograft rejection in lethally irradiated, bone marrow cell (BMC) reconstituted rats. METHODS: We employed a series of MHC congenic and intra-MHC recombinant rat strains so that effects of mismatches in defined RT1 subregions could be studied systematically. BMC allograft survival was measured as 125IUdR uptake in the spleen between day 5 and day 7 after irradiation and BMC reconstitution. RESULTS: We found that in certain RT1 haplotype combinations, nonclassical RT1.C disparities by themselves could determine graft rejection (i.e., in the u/av1 recombinant haplotypes), whereas in another combination (between the av1 and c haplotypes) a mismatch for an isolated classical RT1.A region was decisive for engraftment. Thus, PVG.R1 BMC failed to proliferate in PVG rats, differing in the RT1.A region only, whereas in PVG.1U rats rejection could be determined by isolated differences in the RT1.C region (LEW.1WR1). Also, RT1 homozygous rats (RT1.U) rejected semi-allogeneic F1 hybrid BMC. The acute rejection of BMC was mediated by NK cells, as athymic nude rats, lacking alloreactive T cells but with normal alloreactive NK cells, showed the same patterns of rejection as did normal rats. Nude rats also rejected allogeneic lymphocytes, a previously documented NK-mediated phenomenon, with identical requirements of MHC disparity. CONCLUSIONS: This investigation shows that rat effector NK cells are radioresistant, independent of the thymus, and capable of recognizing and rejecting MHC mismatched transplanted BMC on the basis of mismatches in both classical and nonclassical class I regions in vivo. The studies underline the importance also of NK cells in determining BMC allograft survival. 相似文献
47.
JC Hall 《Canadian Metallurgical Quarterly》1998,14(11-12):874-875
48.
M Martí-Herrero JC Cabrera-López L Toledo V Pérez-Candela D Bonnet 《Canadian Metallurgical Quarterly》1998,27(160):975-978
INTRODUCTION: Moebius's syndrome is an entity present at birth, characterized by oculofacial paralysis and external ophthalmoplegia. Other cranial nerves can also be affected and associated to skeletal abnormalities and neurologic symptoms. It appears sporadically, sometimes of familiar nature, presenting special facies with total absence of facial expression and severe strabismus. The pathogenesis of the syndrome still remains unknown, being the transitory situation of fetal hypoxia/ischemic the most accepted theory. In some cases chromosomal abnormalities have been detected. CLINICAL CASE: We reported three children with different symptoms, two of them are siblings whose father is affected, but he was not diagnosed until adult age. CONCLUSIONS: We conclude pointing out the different presentation of the disease, the appearance in several members of a family and its chronically evolution. 相似文献
49.
JC Post AC van Rossum MB Hofman J Valk CA Visser 《Canadian Metallurgical Quarterly》1996,166(6):1399-1404
OBJECTIVE: MR coronary angiography is most often performed using two-dimensional techniques. Although three-dimensional (3D) acquisitions do have important advantages, they take too long for a single breath-hold and are thus susceptible to respiratory motion artifacts. The purpose of this study was to investigate the accuracy of a unique respiratory-gated 3D MR angiographic technique in identifying the proximal coronary arteries in patients suspected of having coronary artery disease. In addition, we investigated the capability of this technique to detect proximal stenoses. SUBJECTS AND METHODS: We performed a prospective blinded study in 20 patients who were referred for conventional coronary angiography. A cardiac-gated 3D gradient-echo sequence with fat suppression was used. Retrospective respiratory gating was performed using navigator echoes of the diaphragm position. Using multiplanar reformatting, two independent readers blindly analyzed the data sets for visualization of major coronary arteries, lengths of imaged segments, and detection of significant stenoses (> 50% occlusion of the luminal diameter by conventional angiography). RESULTS: Seventy-seven of 80 (96%) coronary arteries were positively identified. In one patient, an anomalous coronary anatomy was readily identified and confirmed by conventional angiography. The average lengths of the imaged segments of the right, left main, left anterior descending, and left circumflex coronary arteries were 58 +/- 13 mm, 9 +/- 5 mm, 59 +/- 16 mm, and 24 +/- 10 mm, respectively. Overall sensitivity for the detection of stenoses was low (38%), with a specificity of 95%. Interobserver agreement was 0.92, with a kappa value of 0.65. CONCLUSION: Respiratory-gated 3D MR angiography allows accurate identification of proximal coronary arteries and may be valuable for 3D imaging of coronary anomalies. Further technical improvements are required to enhance the value of the technique in detecting stenoses. 相似文献
50.