全文获取类型
收费全文 | 58385篇 |
免费 | 3047篇 |
国内免费 | 83篇 |
专业分类
电工技术 | 421篇 |
综合类 | 133篇 |
化学工业 | 12717篇 |
金属工艺 | 1092篇 |
机械仪表 | 1194篇 |
建筑科学 | 1745篇 |
矿业工程 | 135篇 |
能源动力 | 1315篇 |
轻工业 | 10239篇 |
水利工程 | 567篇 |
石油天然气 | 292篇 |
武器工业 | 7篇 |
无线电 | 2367篇 |
一般工业技术 | 9335篇 |
冶金工业 | 11617篇 |
原子能技术 | 248篇 |
自动化技术 | 8091篇 |
出版年
2024年 | 120篇 |
2023年 | 526篇 |
2022年 | 1027篇 |
2021年 | 1703篇 |
2020年 | 1248篇 |
2019年 | 1401篇 |
2018年 | 2235篇 |
2017年 | 2214篇 |
2016年 | 2340篇 |
2015年 | 1702篇 |
2014年 | 2222篇 |
2013年 | 4558篇 |
2012年 | 3541篇 |
2011年 | 3423篇 |
2010年 | 2777篇 |
2009年 | 2503篇 |
2008年 | 2405篇 |
2007年 | 2148篇 |
2006年 | 1589篇 |
2005年 | 1335篇 |
2004年 | 1189篇 |
2003年 | 1167篇 |
2002年 | 1009篇 |
2001年 | 793篇 |
2000年 | 716篇 |
1999年 | 777篇 |
1998年 | 3698篇 |
1997年 | 2453篇 |
1996年 | 1609篇 |
1995年 | 951篇 |
1994年 | 745篇 |
1993年 | 793篇 |
1992年 | 313篇 |
1991年 | 278篇 |
1990年 | 219篇 |
1989年 | 234篇 |
1988年 | 243篇 |
1987年 | 213篇 |
1986年 | 175篇 |
1985年 | 214篇 |
1984年 | 190篇 |
1983年 | 134篇 |
1982年 | 168篇 |
1981年 | 193篇 |
1980年 | 216篇 |
1979年 | 103篇 |
1978年 | 102篇 |
1977年 | 353篇 |
1976年 | 740篇 |
1973年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
11.
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
12.
ML Martínez-Frías E Bermejo Sánchez E Rodríguez Pinilla A Villa 《Canadian Metallurgical Quarterly》1997,46(6):593-596
INTRODUCTION: Even though there are few epidemiological studies evaluating the birth weights of different groups of malformed babies with chromosomal abnormalities, it is widely known that infants with trisomy 18, and to a lesser degree those with trisomy 13 and other chromosomal alterations, have low birth weights. PATIENTS AND METHODS: In this study we present the analysis of the birth weights and gestational ages of a large sample of babies (23,155 malformed and a similar number of nonmalformed babies), separating the different groups of chromosomal anomalies and comparing the weight in the clinical groups of malformed infants. RESULTS: Most of the groups with chromosomal abnormalities present lower birth weights in comparison to the other groups. CONCLUSIONS: The results of our study support the conclusion that the relationship between chromosomal alterations and low birth weight is sufficiently important that such a low birth weight in children with minor or major anomalies should be considered as one more indication to perform chromosomal analysis. 相似文献
13.
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
14.
SA Khotimchenko VM Kodentsova IA Alekseeva SG Vlaskina OA Vrzhesinskaia AA Sokol''nikov LA Kharitonchik IP Aleshko-Ozhevskií LV Sheviakova 《Canadian Metallurgical Quarterly》1997,43(3):158-164
Gamma delta T-Cells represent a minor subpopulation of T-lymphocytes in man and their role in normal and diseased human skin is unknown. This article is a comprehensive review of T-lymphocytes bearing the gamma delta T-cell receptor in normal and pathological human skin. Firstly, we have documented the occurrence of gamma delta T-cells in normal skin and in a range of reactive and malignant skin conditions. We have then discussed the experimental findings regarding the repertoire used by gamma delta T-cells in normal human skin and in cutaneous disorders with an increased percentage of gamma delta T-cells. 相似文献
15.
16.
17.
18.
19.
20.
R Herruzo-Cabrera L Malo-González ME Calle Purón MJ Vizcaíno-Alcaide J Del Rey-Calero 《Canadian Metallurgical Quarterly》1993,9(4):442-446
A cross-sectional study was performed to obtain risk factors for hepatitis B disease, HBsAg carriers and immunised personnel, among 2470 workers in a general hospital in Madrid, Spain. The data obtained were analyzed with multiple logistic regression to obtain beta coefficients for variables. The results of the analysis show that being a nurse or being regularly exposed to blood are the most important risk factors for hepatitis B acquisition. The length of time working at the same job activity was also a risk factor. The resulting beta coefficients allow the construction for a hepatitis non-immunised, HBsAg carrier and immunised HBV status, which can select subjects for a hepatitis B vaccination program. 相似文献