全文获取类型
收费全文 | 50277篇 |
免费 | 3209篇 |
国内免费 | 726篇 |
专业分类
电工技术 | 1132篇 |
综合类 | 1145篇 |
化学工业 | 9429篇 |
金属工艺 | 1293篇 |
机械仪表 | 1552篇 |
建筑科学 | 2026篇 |
矿业工程 | 446篇 |
能源动力 | 1309篇 |
轻工业 | 7147篇 |
水利工程 | 627篇 |
石油天然气 | 554篇 |
武器工业 | 68篇 |
无线电 | 4166篇 |
一般工业技术 | 7296篇 |
冶金工业 | 8918篇 |
原子能技术 | 403篇 |
自动化技术 | 6701篇 |
出版年
2024年 | 78篇 |
2023年 | 369篇 |
2022年 | 741篇 |
2021年 | 1412篇 |
2020年 | 1033篇 |
2019年 | 1188篇 |
2018年 | 1584篇 |
2017年 | 1581篇 |
2016年 | 1525篇 |
2015年 | 1368篇 |
2014年 | 1775篇 |
2013年 | 3216篇 |
2012年 | 2637篇 |
2011年 | 2690篇 |
2010年 | 2223篇 |
2009年 | 2142篇 |
2008年 | 2160篇 |
2007年 | 2095篇 |
2006年 | 1633篇 |
2005年 | 1286篇 |
2004年 | 1403篇 |
2003年 | 1710篇 |
2002年 | 2081篇 |
2001年 | 1746篇 |
2000年 | 1028篇 |
1999年 | 980篇 |
1998年 | 3030篇 |
1997年 | 1996篇 |
1996年 | 1353篇 |
1995年 | 839篇 |
1994年 | 637篇 |
1993年 | 714篇 |
1992年 | 328篇 |
1991年 | 257篇 |
1990年 | 273篇 |
1989年 | 245篇 |
1988年 | 237篇 |
1987年 | 192篇 |
1986年 | 195篇 |
1985年 | 248篇 |
1984年 | 140篇 |
1983年 | 137篇 |
1982年 | 145篇 |
1981年 | 173篇 |
1980年 | 164篇 |
1979年 | 90篇 |
1978年 | 83篇 |
1977年 | 205篇 |
1976年 | 404篇 |
1975年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The indications and results of single and double lung transplantation are described on the basis of 66 operations performed by the authors and on the background of the world literature. Lung transplantation is considered a new and promising therapeutic mode for treating patients with end-stage pulmonary failure related to fibrosis, emphysema, infective conditions, and pulmonary hypertension yielding satisfactory early results. The long-term prognosis of patients undergoing lung transplantation, like that of any other organ transfer, remains guarded. 相似文献
102.
103.
Data from the past few years have shown that as caffeine metabolizes solely in the liver, caffeine elimination can serve as a liver function test. We have collected data by monitoring 40 persons with liver diseases (11 chronic alcoholic hepatitis, 24 liver cirrhosis, 5 non-cirrhotic liver disease). Eight subjects served as controls. The patients with liver cirrhosis were classified according to the Child--Pugh scoring system. To determine caffeine elimination blood samples were collected before and at 3, 6, 9 and 12 hours after oral administration of 0.2 g caffeine. Fasting serum caffeine concentration and concentration 12 hours after administration, serum clearance, half life, peak concentration and volume of distribution have been compared. The respective values measured in patients with non-cirrhotic liver diseases did not differ significantly from the controls. The disappearance of caffeine was significantly decreased in cirrhotics. Our results demonstrated a good correlation between impairment of caffeine elimination and assessment of severity of liver disease by the Child--Pugh classification. Measuring serum levels in samples taken 12 hours after caffeine administration is a simple and useful method in the diagnosis of liver diseases at cirrhotic stage. 相似文献
104.
T P?usa P Górski H Frank-Piskorska M Kowalski J Kruszewski P Kuna M Kurek R Kurzawa W Silny E Zawisza 《Canadian Metallurgical Quarterly》1996,1(4):292-293
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre. 相似文献
105.
Rolandic discharge (RD), noted in the electroencephalography (EEG) of patients with benign epilepsy in childhood with centrotemporal spikes (BECCT) has several unique features. One feature is that the amount or frequency of RDs does not correlate well with the incidence of seizures in BECCT although it is a key finding in the diagnosis of this epileptic syndrome. In this study, we examined the efficacy of antiepileptic drugs focusing on the disappearance of RDs in relationship with seizure control. Forty patients with BECCT who were not medically treated prior to this study were randomly sorted into three groups. Twenty patients were assigned for clonazepam (CZP) treatment, 10 patients for valproate (VPA) and the remaining 10 patients for carbamazepine (CBZ). Each drug was administered for 4 consecutive weeks. EEGs were recorded twice during the study, before and 4 weeks after the medication trial. The effects of each treatment on RDs were assessed. RDs disappeared in 15 of the 20 cases treated with CZP (75%) within 4 weeks while the same was observed in only one of the 10 cases treated with VPA (10%). CBZ failed to demonstrate any effect on RD. In the group treated with CZP, there were no differences in seizure incidence, seizure type and blood concentration of CZP between the patients whose RDs disappeared and those whose RDs remained. 相似文献
106.
107.
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
108.
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
109.
110.
A Abeliovich C Chen Y Goda AJ Silva CF Stevens S Tonegawa 《Canadian Metallurgical Quarterly》1993,75(7):1253-1262
Calcium-phospholipid-dependent protein kinase (PKC) has long been suggested to play an important role in modulating synaptic efficacy. We have created a strain of mice that lacks the gamma subtype of PKC to evaluate the significance of this brain-specific PKC isozyme in synaptic plasticity. Mutant mice are viable, develop normally, and have synaptic transmission that is indistinguishable from wild-type mice. Long-term potentiation (LTP), however, is greatly diminished in mutant animals, while two other forms of synaptic plasticity, long-term depression and paired-pulse facilitation, are normal. Surprisingly, when tetanus to evoke LTP was preceded by a low frequency stimulation, mutant animals displayed apparently normal LTP. We propose that PKC gamma is not part of the molecular machinery that produces LTP but is a key regulatory component. 相似文献