全文获取类型
收费全文 | 34843篇 |
免费 | 1219篇 |
国内免费 | 110篇 |
专业分类
电工技术 | 373篇 |
综合类 | 228篇 |
化学工业 | 4977篇 |
金属工艺 | 626篇 |
机械仪表 | 585篇 |
建筑科学 | 972篇 |
矿业工程 | 93篇 |
能源动力 | 941篇 |
轻工业 | 3892篇 |
水利工程 | 241篇 |
石油天然气 | 153篇 |
武器工业 | 6篇 |
无线电 | 2251篇 |
一般工业技术 | 4112篇 |
冶金工业 | 12728篇 |
原子能技术 | 242篇 |
自动化技术 | 3752篇 |
出版年
2023年 | 140篇 |
2022年 | 396篇 |
2021年 | 777篇 |
2020年 | 530篇 |
2019年 | 595篇 |
2018年 | 687篇 |
2017年 | 764篇 |
2016年 | 716篇 |
2015年 | 550篇 |
2014年 | 864篇 |
2013年 | 1419篇 |
2012年 | 1252篇 |
2011年 | 1579篇 |
2010年 | 1155篇 |
2009年 | 1206篇 |
2008年 | 1097篇 |
2007年 | 965篇 |
2006年 | 784篇 |
2005年 | 837篇 |
2004年 | 911篇 |
2003年 | 823篇 |
2002年 | 792篇 |
2001年 | 691篇 |
2000年 | 547篇 |
1999年 | 734篇 |
1998年 | 4253篇 |
1997年 | 2558篇 |
1996年 | 1709篇 |
1995年 | 1002篇 |
1994年 | 795篇 |
1993年 | 926篇 |
1992年 | 250篇 |
1991年 | 326篇 |
1990年 | 278篇 |
1989年 | 237篇 |
1988年 | 259篇 |
1987年 | 212篇 |
1986年 | 218篇 |
1985年 | 217篇 |
1984年 | 131篇 |
1983年 | 109篇 |
1982年 | 145篇 |
1981年 | 155篇 |
1980年 | 176篇 |
1979年 | 96篇 |
1978年 | 89篇 |
1977年 | 275篇 |
1976年 | 504篇 |
1975年 | 94篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Somatic hypermutation of the immunoglobulin variable genes during germinal reactions might permit the expansion of B-cell clones with unwanted (e.g. autoreactive) specificity. Here, Ernst Lindhout and colleagues propose three antigen-specific checkpoints that ensure the appropriate antigen specificity of activated B cells is maintained by regulating the activation, selection and further differentiation of B cells. 相似文献
62.
F Koumanov C Henry C Ghezzi JP Mathieu C Morin M Vidal J de Leiris M Comet D Fagret 《Canadian Metallurgical Quarterly》1997,24(6):519-525
Two anomeric analogues of glucose labelled with 123 iodine in position 6, proposed as tracers of glucose transport in vivo, have been synthesized: alpha- and beta-methyl-6-deoxy-6-iodo-D-glucopyranoside (alpha MDIG and beta MDIG). The aim of this study was to determine whether these molecules interact with the glucose transporter and whether they could be used as tracers of glucose transport in vivo. The biodistribution of alpha MDIG and beta MDIG was studied in the mouse in vivo. To determine if these two anomers enter the cell via the glucose transporter, their uptake was measured in isolated perfused rat hearts, in human erythrocytes in suspension, and in cardiomyocytes of neonatal rat in culture. Both alpha MDIG and beta MDIG had similar repartitions in the mouse: myocardial uptake averaged 7% of the injected dose/g of organ at 2 min postinjection and alpha MDIG competed with D-glucose to enter the cells. Insulin produced a 123% increase of its uptake in isolated perfused rat hearts and a 100% increase in cardiomyocytes of neonatal rat in culture. alpha MDIG uptake was lowered in the presence of glucose transport inhibitors in each experimental model. An interaction between beta MDIG and glucose transporters was observed only in human erythrocytes in suspension. Only alpha MDIG interacts with the glucose transporter, and thus could be used to estimate glucose transport in vivo. 相似文献
63.
A Newman-Tancredi V Audinot C Chaput L Verrièle MJ Millan 《Canadian Metallurgical Quarterly》1997,282(1):181-191
Great progress has been made in the last 10 years in the understanding of the various types of viral hepatitis, and new viruses, concepts, therapies, preventive measures, and control strategies have been recognized. Even more agents, vaccines, and drugs will be discovered or developed in the future, and pediatricians increasingly will be expected to provide guidance to patients and to the community on the importance and use of these new tools. 相似文献
64.
DJ Conway MJ Holland RL Bailey AE Campbell OS Mahdi R Jennings E Mbena DC Mabey 《Canadian Metallurgical Quarterly》1997,65(3):1003-1006
Tumor necrosis factor alpha (TNF-alpha) may play a central role in the disease pathogenesis which occurs as a consequence of chlamydial infection. To investigate the importance of TNF-alpha gene promoter polymorphisms and TNF-alpha levels in tear fluid in scarring trachoma, a large matched-pair case-control study was performed in The Gambia. The -308A allele was present in a higher proportion of patients (28.4%) than controls (18.4%), with an increasing association for homozygotes (chi2 for trend, P = 0.032; allele frequency, 0.163 in patients and 0.099 in controls; chi2, P = 0.025). For the -238A allele, the association was similar but not significant. The disease association was highly significant when the number of either -308A or -238A sites in an individual was considered (P = 0.003). TNF-alpha promoter alleles are tightly linked to some HLA class I and II alleles, but multivariate analysis confirmed that the disease associations were independent of HLA, although a class I allele, A*6802, is also associated with disease. TNF-alpha was more frequently detected in tear samples from patients (27.6%) than from controls (15.9%), increasingly so for higher levels of detectable TNF-alpha (P = 0.015). Among patients, detectable TNF-alpha in tears was highly associated with the presence of ocular chlamydial infection (P < 0.001). The results indicate that TNF-alpha plays a major role in the tissue damage and scarring which occurs as a consequence of Chlamydia trachomatis infection. 相似文献
65.
66.
67.
E La Hey J de Vries CT Langerhorst GS Baarsma A Kijlstra 《Canadian Metallurgical Quarterly》1993,116(3):327-340
After reviewing the records of 111 patients with Fuchs' heterochromic iridocyclitis, we studied the therapy and prognosis of secondary glaucoma in 30 of these 111 patients (27%) who had glaucoma or could be considered glaucoma suspects. Maximal medical therapy was unsuccessful in 22 of the 30 patients (73%). Surgical intervention (mostly trabeculectomies, half with 5-fluorouracil) successfully controlled intraocular pressure (< or = 21 mm Hg with or without medication) in 13 of the 18 operated-on patients (72%) after a mean follow-up of 26 months. All successfully operated-on patients retained a visual acuity of 20/80 or better. We had favorable results, possibly because of modern surgical techniques (use of 5-fluorouracil, sodium hyaluronate) or earlier surgical intervention, or both. 相似文献
68.
STRONG METAL-CERAMIC JOINTS 总被引:3,自引:0,他引:3
In this paper the technology for joining metals to ceramics is reviewed. The technologies of metal powder sintering, liquid phase joining with activated brazing alloys and with ceramic frit, solid-state joining, friction welding and mechanical fixation are described. In order to put some perspective on the mechanical data given in the literature, some evaluating remarks on mechanical testing are made. 相似文献
69.
70.
OBJECTIVES: To assess that neuromuscular relaxation onset of the adductor pollicis (AP) is related to neuromuscular stimulation rate. To assess that train-of-four (TOF) at 0.05 Hz is a more accurate indicator of optimal tracheal intubation time and conditions, than TOF at 0.08 Hz. STUDY DESIGN: Prospective, comparative, randomized double-blind study. PATIENTS: Forty adults, physical class ASA 1 or 2, undergoing general anaesthesia with tracheal intubation were allocated to two groups (n = 20) according to the sequence of stimulation of the AP: either TOF at 0.05 Hz (test group) or TOF at 0.08 Hz (control group). METHODS: Induction of anaesthesia was achieved with thiopentone, fentanyl and vecuronium (0.1 mg.kg-1). Neuromuscular monitoring was obtained with force displacement transducers attached to each AP. Tracheal intubation was performed once AP muscular response obtained with TOF at 0.05 Hz for test group and TOF at 0.08 Hz for control group was abolished. Results are expressed as mean +/- SEM. Fisher exact test was used for intubation conditions comparison. Curarization time between groups was compared with unpaired Student's t test (P < 0.05 accepted). RESULTS: TOF with 0.05 Hz stimulation significantly increased curarization time: 217 +/- 7 versus 162 +/- 6 s (P < 0.001). Intubation conditions were excellent in 95% and good in 5% of patients in the study group, compared to 15 and 40% in the control group, respectively (P < 0.01) in 45% of the control group patients coughing at intubation occurred. CONCLUSION: Low stimulation rate (TOF at 0.05 Hz) of AP is a reliable technique to determine the appropriate intubation time for patients paralyzed with vecuronium. 相似文献