全文获取类型
收费全文 | 46059篇 |
免费 | 2549篇 |
国内免费 | 47篇 |
专业分类
电工技术 | 352篇 |
综合类 | 39篇 |
化学工业 | 8286篇 |
金属工艺 | 921篇 |
机械仪表 | 926篇 |
建筑科学 | 1453篇 |
矿业工程 | 95篇 |
能源动力 | 888篇 |
轻工业 | 5874篇 |
水利工程 | 395篇 |
石油天然气 | 178篇 |
武器工业 | 4篇 |
无线电 | 2668篇 |
一般工业技术 | 8098篇 |
冶金工业 | 12209篇 |
原子能技术 | 250篇 |
自动化技术 | 6019篇 |
出版年
2023年 | 376篇 |
2022年 | 351篇 |
2021年 | 929篇 |
2020年 | 799篇 |
2019年 | 716篇 |
2018年 | 1619篇 |
2017年 | 1619篇 |
2016年 | 1680篇 |
2015年 | 1204篇 |
2014年 | 1506篇 |
2013年 | 3016篇 |
2012年 | 2584篇 |
2011年 | 2461篇 |
2010年 | 1926篇 |
2009年 | 1724篇 |
2008年 | 1992篇 |
2007年 | 1742篇 |
2006年 | 1298篇 |
2005年 | 1146篇 |
2004年 | 1072篇 |
2003年 | 973篇 |
2002年 | 844篇 |
2001年 | 570篇 |
2000年 | 590篇 |
1999年 | 718篇 |
1998年 | 3940篇 |
1997年 | 2360篇 |
1996年 | 1521篇 |
1995年 | 902篇 |
1994年 | 775篇 |
1993年 | 767篇 |
1992年 | 260篇 |
1991年 | 279篇 |
1990年 | 263篇 |
1989年 | 256篇 |
1988年 | 242篇 |
1987年 | 216篇 |
1986年 | 217篇 |
1985年 | 256篇 |
1984年 | 221篇 |
1983年 | 165篇 |
1982年 | 203篇 |
1981年 | 217篇 |
1980年 | 190篇 |
1979年 | 149篇 |
1978年 | 144篇 |
1977年 | 244篇 |
1976年 | 508篇 |
1975年 | 126篇 |
1973年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 221 毫秒
71.
J Valls-Solé A Cruz Martinez F Graus A Saiz J Arpa JM Grau 《Canadian Metallurgical Quarterly》1995,45(11):2024-2028
Two patients exhibited chronic, slightly asymmetric weakness and wasting with fasciculations of the upper limb and hand muscles. Motor nerve conduction studies showed features of multifocal conduction block in nerve segments other than those usually involved in entrapment syndromes. The F wave was markedly delayed in the median and ulnar nerves. Transcranial cortical and cervical root magnetic stimulation showed bilaterally delayed thenar responses with normal central conduction time. Needle electromyography demonstrated a chronic denervation pattern with large polyphasic motor units in several muscles of the upper limbs. Sensory symptoms were mild and limited to paresthesias in the fingertips. Sensory nerve conduction velocity and sensory nerve action potential amplitudes were normal in elbow-to-wrist and wrist-to-finger segments of the median and ulnar nerves, but there was a delayed cortical response and unrecognizable Erb's point and cervical responses in the somatosensory evoked potentials to median nerve electrical stimulation. Electrophysiologic examination was normal in most nerves of the lower limbs. These two patients, meeting clinical and electrophysiologic criteria of multifocal neuropathy with conduction block, demonstrate that sensory fibers may also be involved in this syndrome. 相似文献
72.
E Messou SV Sangaré R Josseran C Le Corre J Guélain 《Canadian Metallurgical Quarterly》1997,90(1):44-47
BACKGROUND: Gastric sucrose permeability is a noninvasive marker that reliably increases in association with gastrointestinal injury due to use of nonsteroidal antiinflammatory drugs. Despite the effect of Helicobacter pylori infection on the gastric mucosa, in a previous study we were unable to demonstrate that H. pylori infection was associated with abnormal gastric sucrose permeability. Our goal in this study was to explore further whether H. pylori infection changed gastric permeability; therefore, we evaluated the effect of treatment of H. pylori infection on gastric permeability to sucrose and the relation of sucrose permeability to density of polymorphonuclear leukocytes. MATERIALS AND METHODS: Five hundred milliliters of a solution containing 100 gm of sucrose was ingested by the subject at bedtime. Overnight urine was collected and assayed for sucrose by high-performance liquid chromatography. Sucrose permeability was assessed both before and approximately 4 weeks after anti-H. pylori therapy. RESULTS: Seventeen asymptomatic H. pylori-infected volunteers participated; 8 were cured. Sucrose permeability was in the range commonly found in normal controls both before and after anti-H. pylori therapy (mean excretion, 76.3 mg; range, 13-171 mg). Gastric sucrose permeability correlated with the density of polymorphonulcear cell infiltration of the mucosa. Cure of the H. pylori infection was associated with a small but significant decrease in sucrose permeability (98.8 +/- 18 mg to 51.7 +/- 9.8 mg (p = .01). Sucrose permeability was greater in those with a high density of mucosal polymorphonuclear cells compared to those with lower scores (119.5 +/- 4 vs 71.4 +/- 13 for those with scores > or = 5 compared to scores < or = 4; p = .023). Failed therapy resulted in an increase in the mucosal density of polymorphonuclear infiltration and sucrose permeability (56.4 +/- 13 mg-99.7 +/- 19 mg pretreatment vs posttreatment, respectively; p = .031). CONCLUSION: H. pylori gastritis causes a small but measurable increase in gastric permeability to sucrose that may reflect epithelial transmigration of neutrophils. 相似文献
73.
M Fern? PO Bendahl A Brisfors K Byman M Ekeberg L Ferraud K Grankvist B Hjalmers A Nilsson G Sellberg L Skoog O St?l I Wingmo 《Canadian Metallurgical Quarterly》1997,36(8):793-798
Estrogen and progesterone receptor analysis results were compared within and between six laboratories in Sweden using frozen breast cancer cytosol samples, and the same technique (enzyme immunoassay, Abbott Laboratories). The concordance in receptor status (positive vs. negative) was excellent (98.4% (571/580)). The discordant results were attributable to values near cut-off (n = 4) or outliers (n = 5), the latter probably being due to analytical errors. One laboratory reported significantly higher ER concentrations than the others; thus caution should be observed when comparing absolute values from different centers. For PgR there were similar differences between the laboratories. However, the intra- and inter-laboratory differences were small compared with the overall variability in ER and PgR content between different samples in a large database. The range of the median intra-laboratory coefficient of variation was 11-23% for ER and 12-19% for PgR, indicating that there is room for improvement in the quality of assay performance. 相似文献
74.
P de Lonlay JC Fournet J Rahier MS Gross-Morand F Poggi-Travert V Foussier JP Bonnefont MC Brusset F Brunelle JJ Robert C Nihoul-Fékété JM Saudubray C Junien 《Canadian Metallurgical Quarterly》1997,100(4):802-807
Sporadic persistent hyperinsulinemic hypoglycemia of infancy (PHHI) or nesidioblastosis is a heterogeneous disorder characterized by profound hypoglycemia due to inappropriate hypersecretion of insulin. An important diagnostic goal is to distinguish patients with a focal hyperplasia of islet cells of the pancreas (FoPHHI) from those with a diffuse abnormality of islets (DiPHHI) because management strategies differ significantly. 16 infants with sporadic PHHI resistant to diazoxide and who underwent pancreatectomy were investigated. Selective pancreatic venous sampling coupled with peroperative surgical examination and analysis of extemporaneous frozen sections allowed us to identify 10 cases with FoPHHI and 6 cases with DiPHHI. We show here that in cases of FoPHHI, but not those of DiPHHI, there was specific loss of maternal alleles of the imprinted chromosome region 11p15 in cells of the hyperplastic area of the pancreas but not in normal pancreatic cells. This somatic event is consistent with a proliferative monoclonal lesion. It involves disruption of the balance between monoallelic expression of several maternally and paternally expressed genes. Thus, we provide the first molecular explanation of the heterogeneity of sporadic forms of PHHI such that it is possible to perform only partial pancreatectomy, limited to the focal somatic lesion, so as to avoid iatrogenic diabetes in patients with focal adenomatous hyperplasia. 相似文献
75.
Carcinoma of the prostate, that is adenocarcinoma, is one of the most common malignancies in the male with an estimated incidence for 1991 of 122,000 new cases. On the other hand, squamous cell carcinoma of the prostate, with a median incidence of .5%-1% of all prostatic malignancies, has a similar clinical presentation but differs in treatment response and prognosis. We herein present one case of this histological pattern and review the literature pertaining to it. 相似文献
76.
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
77.
Nitrous oxide (N2O) effects were evaluated, as a behavioural model of inert gas narcosis, in rats performing a vigilance task in which they were required to respond to a slight luminous increment of the house-light. A dose-related decrease of correct responses was produced by the tested range of concentrations of N2O (from 30 to 70% N2O), with a parallel increase of anticipatory responses up to 60% N2O and a dramatic increase of omissions at 70% N2O. The influence of preparatory period duration on hits delays suggested a 'conditional probability effect' conserved under N2O. Pretreatment of animals with flumazenil (a central benzodiazepine receptor antagonist) did not improve performance under 40% N2O. Naltrexone, an opiate receptor antagonist, however, increased the N2O-induced deficits. These results suggest that benzodiazepine receptors are not involved in N2O-induced impairments in this attentional task, but opiate mechanisms may be implicated. 相似文献
78.
R Jover J Llach JM Bordas A Mas JM Salmerón S Navarro J Terés 《Canadian Metallurgical Quarterly》1997,20(7):344-346
There are evidence indicating that endoscopic retrograde cholangiopancreatography with sphincterotomy (ERCP+S) reduces the rate of complications in patients with severe acute biliary pancreatitis (ABP). The aim of this study was to analyze our experience in the treatment of severe ABP with ERCP+S and compare the evolution of the patients treated early (3 days or less following admission) with those treated late (after the 3rd day). A retrospective review of the clinical histories of the 16 patients with severe ABP treated with ERCP+S over the last two years is presented, analyzing their clinical features on admission and evolution. Biliary stones or biliary sludge was observed in 11 cases (69%). Nine patients had undergone early, and 7 late, ERCP+S. The patients of the latter group presented a greater number of complications during evolution than the former group (43% vs 0%; p = 0.025). The mortality of the patients of the late ERCP+S was also greater although without statistical significance (28.6% vs 0%; p = 0.15). No complication secondary to ERCP+S was detected. These findings confirm the fact that ERCP+S performed early in severe ABP significantly reduces the number of complications and is associated with a lower mortality. 相似文献
79.
A Azzi D Boscoboinik S Clément D Marilley NK Ozer R Ricciarelli A Tasinato 《Canadian Metallurgical Quarterly》1997,57(4-5):507-514
The effects of alpha-tocopherol and beta-tocopherol have been studied in rat and human aortic smooth muscle cells. Alpha-tocopherol, but not beta-tocopherol, inhibited smooth muscle cell proliferation and protein kinase C in a dose-dependent manner, at concentrations ranging from 10 to 50 microM. Beta-tocopherol added simultaneously with alpha-tocopherol prevented both proliferation and protein kinase C inhibition. Protein kinase C inhibition was cell cycle-dependent and it was prevented by okadaic acid, a protein phosphatase inhibitor. Protein kinase C activity measured from aortas of cholesterol-fed rabbits was also inhibited by alpha-tocopherol. By using protein kinase C (PKC) isoform-specific inhibitors and immunoprecipitation reactions it was found that PKC-alpha was selectively inhibited by alpha-tocopherol. Further, an activation of protein phosphatase 2A by alpha-tocopherol was found, which caused PKC-alpha dephosphorylation and inhibition. Ultimately, this cascade of events at the level of cell signal transduction leads to the inhibition of smooth muscle cell proliferation. 相似文献
80.
JA Calera S Paris M Monod AJ Hamilton JP Debeaupuis M Diaquin R López-Medrano F Leal JP Latgé 《Canadian Metallurgical Quarterly》1997,65(11):4718-4724
Aspergillus fumigatus possesses two catalases (described as fast and slow on the basis of their electrophoretic mobility). The slow catalase has been recognized as a diagnostic antigen for aspergillosis in immunocompetent patients. The antigenic catalase has been purified. The enzyme is a tetrameric protein composed of 90-kDa subunits. The corresponding cat1 gene was cloned, and sequencing data show that the cat1 gene codes for a 728-amino-acid polypeptide. A recombinant protein expressed in Pichia pastoris is enzymatically active and has biochemical and antigenic properties that are similar to those of the wild-type catalase. Molecular experiments reveal that CAT1 contains a signal peptide and a propeptide of 15 and 12 amino acid residues, respectively. cat1-disrupted mutants that were unable to produce the slow catalase were as sensitive to H2O2 and polymorphonuclear cells as the wild-type strain. In addition, there was no difference in pathogenicity between the cat1 mutant and its parental cat1+ strain in a murine model of aspergillosis. 相似文献