全文获取类型
收费全文 | 2550篇 |
免费 | 22篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 5篇 |
综合类 | 3篇 |
化学工业 | 252篇 |
金属工艺 | 22篇 |
机械仪表 | 26篇 |
建筑科学 | 26篇 |
矿业工程 | 1篇 |
能源动力 | 17篇 |
轻工业 | 151篇 |
水利工程 | 8篇 |
无线电 | 68篇 |
一般工业技术 | 139篇 |
冶金工业 | 1742篇 |
原子能技术 | 14篇 |
自动化技术 | 101篇 |
出版年
2022年 | 8篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 8篇 |
2014年 | 20篇 |
2013年 | 30篇 |
2012年 | 33篇 |
2011年 | 51篇 |
2010年 | 29篇 |
2009年 | 36篇 |
2008年 | 48篇 |
2007年 | 34篇 |
2006年 | 49篇 |
2005年 | 35篇 |
2004年 | 21篇 |
2003年 | 29篇 |
2002年 | 20篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 68篇 |
1998年 | 572篇 |
1997年 | 313篇 |
1996年 | 211篇 |
1995年 | 113篇 |
1994年 | 97篇 |
1993年 | 103篇 |
1992年 | 25篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 38篇 |
1988年 | 26篇 |
1987年 | 33篇 |
1986年 | 30篇 |
1985年 | 32篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1978年 | 11篇 |
1977年 | 32篇 |
1976年 | 101篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1968年 | 8篇 |
排序方式: 共有2575条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND & AIMS: The molecular mechanisms underlying pancreatitis are largely unknown. The goal of this study was to identify an early genetic event that correlated with pancreatitis. METHODS: Differential display of messenger RNAs (mRNAs) was conducted on normal pancreas vs. those of animals with secretagogue-induced pancreatitis. Northern blots from normal animals and animals with experimental acute pancreatitis were probed with cloned complementary DNAs for chemokines. Pancreatitis was induced with cerulein and by retrograde injection of bile salts. Immunocytochemistry was used to identify the source of chemokine expression. Pyrrolidine dithiocarbamate was tested for effects on chemokine expression and pancreatitis. RESULTS: A differentially amplified band was consistently observed early after cerulein hyperstimulation. This band was identified as a portion of the mob-1 gene, an alpha-chemokine. Northern analysis indicated that mRNAs for mob-1 and another chemokine, mcp-1, were induced after cerulein hyperstimulation in vivo. mob-1 mRNA was also induced by retrograde injection of bile salts and by cerulein in acinar cells in vitro. mob-1 protein was localized to exocrine cells in pancreata of diseased animals. Pyrrolidine dithiocarbamate inhibited both chemokine gene expression and early inflammatory characteristics of pancreatitis. CONCLUSIONS: Chemokines are induced in acinar cells by treatments that induce pancreatitis and may play an important role in the early stages of the disease. 相似文献
3.
Axillary lymphadenectomy in breast conservation surgery is associated with substantial morbidity in either seroma formation or infection. Seroma formation in the axilla requiring aspiration occurs in up to 42 per cent of patients treated without drainage. Prolonged outpatient suction drainage reduces but does not eliminate the incidence of seroma formation, while increasing cost, discomfort, and possibly infection rates. We studied the efficacy of overnight closed suction drainage in patients undergoing breast conservation surgery. Fifty consecutive patients undergoing a standard axillary dissection for breast cancer were studied. The axilla was drained with a 7-French closed suction drain. All drains were removed within 23 hours of surgery and prior to discharge from the outpatient surgical center. Patients were examined by the operating surgeon 7 to 10 days after surgery. One patient (2%) experienced a seroma postoperatively. No infections were observed in all 50 patients, and the remaining 49 patients did not experience visible or symptomatic seromas. The number of lymph nodes removed ranged between 5 and 33 with a mean of 15.5 +/- 0.6. Nine out of 50 (18%) patients had metastatic breast cancer to the axillary lymph nodes. Patients undergoing breast conservation surgery benefit from overnight closed suction drainage of the axilla. This short-term method reduces the incidence and the inherent morbidity of axillary seroma formation. 相似文献
4.
5.
The purpose of this study is to examine the interface between financial strain, informal received economic support, informal anticipated financial support, and psychological distress in later life. Data provided by a large probability sample of older adults in the People's Republic of China reveal that the relationship between financial difficulty and psychological distress is stronger for older adults who receive more economic assistance. However, the results involving anticipated support are in the opposite direction. More specifically, the association between financial problems and psychological distress is lower for older adults who believe that others stand ready to help in the future should the need arise. A detailed theoretical rationale is developed to explain these results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
7.
8.
RobetKrause KhoiTran JohnConstantino 《世界电子元器件》2004,(4):31-32
电动汽车常被喻作“归来的孩子”,因为这项技术在多年前进入市场后便一直沉寂,直至最近才再次活跃起来。其实,电动汽车早于1835年首次于美国出现,到1899年,纽约市接近90%的出租车都是由电力驱动。然而,当电力启动器和内燃机变得完善时,电动汽车的使用就迅速衰退。随着如今对环境保护的关注,由燃烧碳氢化合物造成的污染,加之汽油成本高升的影响,再次 相似文献
9.
10.
CD Wroe 《Canadian Metallurgical Quarterly》1997,51(7):463-465
Cardiac dysrhythmias in septic patients often reflect hypovolaemia, hypokalaemia or endocarditis as cardiac manifestation of the infection, but may be indicative for underlying cardiac pathology previously undiagnosed. We report on the case of a patient with severe peritonitis, on whom transoesophageal echocardiography (TEE) had been performed intraoperatively due to progressive circulatory instability. TEE revealed first diagnosis of asymmetric hypertrophic cardiomyopathy, which complicated the features of septic syndrome. Further perioperative treatment to support the circulation was successfully adjusted on the grounds of this diagnosis. 相似文献