全文获取类型
收费全文 | 2368篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 7篇 |
金属工艺 | 1篇 |
矿业工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 4篇 |
一般工业技术 | 8篇 |
冶金工业 | 2346篇 |
自动化技术 | 1篇 |
出版年
2013年 | 2篇 |
2012年 | 1篇 |
2010年 | 1篇 |
2006年 | 1篇 |
2003年 | 3篇 |
2000年 | 1篇 |
1999年 | 71篇 |
1998年 | 655篇 |
1997年 | 387篇 |
1996年 | 294篇 |
1995年 | 128篇 |
1994年 | 113篇 |
1993年 | 166篇 |
1992年 | 21篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 35篇 |
1988年 | 24篇 |
1987年 | 30篇 |
1986年 | 33篇 |
1985年 | 31篇 |
1983年 | 4篇 |
1982年 | 14篇 |
1981年 | 25篇 |
1980年 | 22篇 |
1978年 | 7篇 |
1977年 | 69篇 |
1976年 | 156篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有2369条查询结果,搜索用时 15 毫秒
991.
992.
OBJECTIVE: To search differentially expressed sequences correlated with pathogenesis of human nasopharyngeal carcinoma (NPC), including the candidates of tumor suppressor genes. METHODS: cDNA representational difference analysis (RDA) was performed to isolate differentially expressed sequences between cDNA from normal human primary cultures of nasopharyngeal epithelial cells and cDNA from NPC cell line HNE1. The sources of differentially expressed products were proved by Southern blot and Northern blot. The fragments were cloned with pGEM-T easy kit and sequenced by the chain termination reaction. RESULTS: Four differentially expressed cDNA fragments were isolated in the fourth subtractive hybridization using cDNA from normal human primary cultures of nasopharyngeal epithelial cells as tester amplicon and cDNA from NPC cell line HNE1 as driver amplicon by cDNA RDA. These differential cDNA fragments revealed that they really came from the tester amplicon and were not expressed or down-regulated in the NPC HNE1 cells. Of these obtained clones, some are the fragments of the human known genes including house-keeping genes, the others are novel genes. CONCLUSION: NPC involves alteration of multiple genes. Some of known genes matched with the differentially expressed sequences have an effective suppressive ability on the carcinoma. 相似文献
993.
LA Green FS Rhame RW Price DC Perlman LG Capps JH Sampson LR Deyton SM Schnittman EJ Fisher GE Bartsch EA Krum JD Neaton 《Canadian Metallurgical Quarterly》1998,12(15):1983-1990
OBJECTIVES: To describe the methods and results of a standardized system for clinical endpoint determination for defining and reviewing endpoints in clinical trials for HIV-infected individuals. DESIGN: A system was developed utilizing standard definitions for the 24 diagnoses or clinical events that serve as trial endpoints and together define the combined endpoint 'progression of HIV disease. A common set of case report forms were used for all trials. Thus, an event of Pneumocystis carinii pneumonia (PCP), for example, for a subject co-enrolled in an antiretroviral trial and a PCP prophylaxis trial was only reported once. METHODS: A central committee was established to define clinical events and review endpoints across all studies. Events were classified according to established criteria for confirmed, probable and possible levels of certainty. RESULTS: This report describes the methods used to ascertain and review endpoints, and summarized 2299 clinical events for 8097 subjects enrolled in one or more of nine clinical trials. Data on the diagnostic certainty of events and agreement between site clinicians and the endpoint committee are presented. CONCLUSIONS: Uniform classification of endpoints across AIDS clinical trials can be accomplished by multicenter, multitrial organizations with standardized definitions and review of endpoint documentation. Our experience suggests that nurse coordinators reviewing all submitted endpoints for every trial are warranted and the need for external review by a clinical events committee may depend on the type of trial conducted. 相似文献
994.
995.
A van der Ende ZJ Pan A Bart RW van der Hulst M Feller SD Xiao GN Tytgat J Dankert 《Canadian Metallurgical Quarterly》1998,66(5):1822-1826
The aim of this research was to study whether and to what extent Chinese cagA-positive Helicobacter pylori isolates differ from those in The Netherlands. Analysis of random amplified polymorphic DNA (RAPD)-PCR-assessed DNA fingerprints of chromosomal DNA of 24 cagA-positive H. pylori isolates from Dutch (n = 12) and Chinese (n = 10) patients yielded the absence of clustering. Based on comparison of the sequence of a 243-nucleotide part of cagA, the Dutch (group I) and Chinese (group II) H. pylori isolates formed two separate branches with high confidence limits in the phylogenetic tree. These two clusters were not observed when the sequence of a 240-bp part of glmM was used in the comparison. The number of nonsynonymous substitutions was much higher in cagA than in glmM, indicating positive selection. The average levels of divergence of cagA at the nucleotide and protein levels between group I and II isolates were found to be high, 13.3 and 17.9%, respectively. Possibly, the pathogenicity island (PAI) that has been integrated into the chromosome of the ancestor of H. pylori now circulating in China contained a different cagA than the PAI that has been integrated into the chromosome of the ancestor of H. pylori now circulating in The Netherlands. We conclude that in China and The Netherlands, two distinct cagA-positive H. pylori populations are circulating. 相似文献
996.
RW Schlosser DM Blischak PJ Belfiore C Bartley N Barnett 《Canadian Metallurgical Quarterly》1998,28(4):309-319
The number of telephone surveys conducted has increased in Japan, with the telephone directory often used for sampling respondents in telephone surveys. As some subscribers request that their numbers not be listed, they are excluded. The Random Digit Dialing (RDD) survey method, however, not only makes possible smooth data collection, but also random sampling of all subscribers in telephone surveys. The authors conducted a telephone survey in Tokyo using the RDD method to investigate any differences in behavior and demographic or social attributes between listed and unlisted subscribers. These attributes included gender, age, family size, job, and residential area. The findings were as follows: 1) The listing rate in telephone directories was 65.8% among respondents. 2) Old age, large family size and certain residential areas correlated with higher listing rates. 3) Nevertheless, the relationship between listing in the telephone directory and residential area remains somewhat unclear due to the confounding attributes of age and family size. 4) Using Hayashi's second method of quantification, age, family size and occupation correlated with listing frequency. 5) There were also significant differences between listed and unlisted subscribers on questions of health maintenance and lifestyle. 相似文献
997.
The recent discovery of glycine transporters in both the central nervous system and the periphery suggests that glycine transport may be critical to N-methyl-D-aspartate receptor (NMDAR) function by controlling glycine concentration at the NMDAR modulatory glycine site. Data obtained from whole-cell patch-clamp recordings of hippocampal pyramidal neurons, in vitro, demonstrated that exogenous glycine and glycine transporter type 1 (GLYT1) antagonist selectively enhanced the amplitude of the NMDA component of a glutamatergic excitatory postsynaptic current. The effect was blocked by 2-amino-5-phosphonovaleric acid and 7-chloro-kynurenic acid but not by strychnine. Thus, the glycine-binding site was not saturated under the control conditions. Furthermore, GLYT1 antagonist enhanced NMDAR function during perfusion with medium containing 10 microM glycine, a concentration similar to that in the cerebrospinal fluid in vivo, thereby supporting the hypothesis that the GLYT1 maintains subsaturating concentration of glycine at synaptically activated NMDAR. The enhancement of NMDAR function by specific GLYT1 antagonism may be a feasible target for therapeutic agents directed toward diseases related to hypofunction of NMDAR. 相似文献
998.
VV Halbach CF Dowd RT Higashida PA Balousek RW Urwin 《Canadian Metallurgical Quarterly》1998,19(4):773-777
We report our preliminary experience with a new embolic device, the electrolytically detachable fibered coil, in the treatment of four patients with high-flow arteriovenous shunting. 相似文献
999.
RW Gruessner DE Sutherland MB Drangstveit L Wrenshall A Humar AC Gruessner 《Canadian Metallurgical Quarterly》1998,66(3):318-323
We report the use of a bone graft harvested from the palmar and ulnar aspect of the distal radius and vascularized by the palmar carpal artery for the treatment of scaphoid nonunion in 17 patients, ten of whom had already had unsuccessful surgery. Union was obtained in all cases at an average of 60 days (range, 45-90 days). The average follow-up was 16 months (range, 12-36 months). There were no failures. 相似文献
1000.
RM Birn PA Bandettini RW Cox A Jesmanowicz R Shaker 《Canadian Metallurgical Quarterly》1998,40(1):55-60
Urologists enjoying the protection of the law owe a duty to participate in the legal system as expert witnesses. Forensic education has been neglected by clinical educators. Qualification of experts includes forensic as well as clinical competence. The forensic urologist must know legal concepts and language; the powers, duties, and role of courtroom experts. The expert witness' role is to factually enlighten the judges, not to persuade them. Practical measures to remedy the current state of affairs are described from over a decade of experience. These practical measures should be supplemented by the formal development of a subspecialty of Forensic Urology sponsored by our colleges and professional societies. 相似文献