全文获取类型
收费全文 | 317524篇 |
免费 | 5773篇 |
国内免费 | 2317篇 |
专业分类
电工技术 | 7040篇 |
技术理论 | 2篇 |
综合类 | 2241篇 |
化学工业 | 50215篇 |
金属工艺 | 13355篇 |
机械仪表 | 10586篇 |
建筑科学 | 9852篇 |
矿业工程 | 2647篇 |
能源动力 | 7546篇 |
轻工业 | 28355篇 |
水利工程 | 3723篇 |
石油天然气 | 8440篇 |
武器工业 | 248篇 |
无线电 | 35094篇 |
一般工业技术 | 60364篇 |
冶金工业 | 52508篇 |
原子能技术 | 7929篇 |
自动化技术 | 25469篇 |
出版年
2021年 | 3524篇 |
2020年 | 2634篇 |
2019年 | 2798篇 |
2018年 | 4581篇 |
2017年 | 4646篇 |
2016年 | 4851篇 |
2015年 | 3637篇 |
2014年 | 5780篇 |
2013年 | 13781篇 |
2012年 | 8825篇 |
2011年 | 11315篇 |
2010年 | 9547篇 |
2009年 | 10504篇 |
2008年 | 10642篇 |
2007年 | 10420篇 |
2006年 | 9386篇 |
2005年 | 8639篇 |
2004年 | 7682篇 |
2003年 | 7375篇 |
2002年 | 7439篇 |
2001年 | 7229篇 |
2000年 | 6830篇 |
1999年 | 6918篇 |
1998年 | 15223篇 |
1997年 | 11488篇 |
1996年 | 9023篇 |
1995年 | 6890篇 |
1994年 | 6222篇 |
1993年 | 5985篇 |
1992年 | 4634篇 |
1991年 | 4545篇 |
1990年 | 4365篇 |
1989年 | 4375篇 |
1988年 | 4316篇 |
1987年 | 3641篇 |
1986年 | 3631篇 |
1985年 | 4185篇 |
1984年 | 3976篇 |
1983年 | 3634篇 |
1982年 | 3433篇 |
1981年 | 3566篇 |
1980年 | 3429篇 |
1979年 | 3374篇 |
1978年 | 3446篇 |
1977年 | 3927篇 |
1976年 | 5037篇 |
1975年 | 3159篇 |
1974年 | 3007篇 |
1973年 | 3024篇 |
1972年 | 2651篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
P Cruz R Almeida M Gon?alves G Marote J Silva C Cavaleiro V Jacinto 《Canadian Metallurgical Quarterly》1994,7(5):277-280
Ocular paresis is a usual diagnosis in neuro-ophthalmologic consultation, and its aetiology is indeed a challenge. The authors studied 3400 records concerning this consultation, between 1982 and the third quarter of 1993. During this period 221 cases with ocular paresis were selected. During this retrospective study we point out the following items: the cranial nerve affected; the neuro-ophthalmologic semiology; the aetiology and clinical evolution, according to the age groups. From 221 cases selected, 111 were paresis from the VIth pair (50.2%), 88 from the IIIrd pair (39.8%), 14 multiple paresis (6.4%) and 8 paresis from the IVth pair (3.6%). The most frequent complaint was diplopia (> 90%). As far as the aetiological diagnosis is concerned, this was easier to establish in patients > 50 years of age. In this age group the most usual aetiology was vascular and traumatic pathologies. In younger patients the most frequent pathologies were traumatic and tumoral. The prognostic was better in the vascular group, the paresis recovery being > 50% in all other pathologies, except the tumoral one. 相似文献
992.
Carotid-cavernous fistulas are abnormal communications between the internal carotid artery and the cavernous sinus produced by a rupture of the wall of the carotid artery or one of its branches into the sinus. Extradural branches of the internal or external carotid arteries may communicate with the cavernous sinus, producing proptosis, progressive glaucoma, and ocular vascular engorgement. Various approaches to obliterate these fistulas have evolved, many of which carry high morbidity or are precluded by anatomical considerations. Analysis of the venous anatomy of the orbit and face, including human cadaver dissections, reveals a new and safe approach to the cavernous sinus, requiring microsurgical isolation and cannulation of the superior ophthalmic vein through an anterior orbital approach. Selective embolization of a carotid-cavernous fistula can be performed successfully through this route. We present pertinent anatomy and technical considerations and the successful clinical application of these principles. Surgeons familiar with craniofacial anatomy and microvascular techniques can apply these principles and play an active role in the treatment of these complex problems. 相似文献
993.
A Colli M Cocciolo C Riva L Marcassoli M Pirola P Di Gregorio G Buccino 《Canadian Metallurgical Quarterly》1993,72(3):677-682
BACKGROUND: Ascites in patients with hepatocellular carcinoma (HCC) is a poorly characterized subgroup of malignancy-related ascites. Not only the underlying liver disease, but also the tumor growth and spread contributes to the ascites formation. The authors differentiated ascites in HCC from other types of ascites. METHODS: The authors analyzed the ascitic fluid of 185 consecutive patients (89 liver cirrhosis, 33 HCC, 31 peritoneal carcinomatosis, 22 liver metastases, 10 spontaneous bacterial peritonitis). RESULTS: Each subgroup showed a typical pattern. Compared with the cirrhotic patients, those with HCC showed a higher frequency of positive cytologic findings (4 of 33 versus 0/89, P < 0.004), elevated fibronectin concentration (10/33 versus 8/89, P < 0.004), and elevated polymorphonuclear cell count (10/33 versus 5/89 P < 0.004). CONCLUSIONS: A significant number of patients with ascites and HCC patients showed signs of peritoneal infiltration with positive cytologic findings and increased concentration of fibronectin. Moreover, neutrocytic ascites without signs of superinfection is relatively common (30%). 相似文献
994.
G Bioque D Vargas O Bulbena J Roselló-Catafau Gelpi E 《Canadian Metallurgical Quarterly》1993,38(1-2):38-43
N-phenyllinoleamide (NPLA) has been detected as extraneous compound in adulterated cooking oils associated with a unique epidemic disease known as the Toxic Oil Syndrome (TOS). In this communication we report on the action of NPLA on the endogenous cyclooxygenase and lipoxygenase arachidonate metabolism. Results show that mouse peritoneal macrophages (MPM) exposed to 1 mM NPLA for 2 h undergo significant increases of 6-keto prostaglandin F1a, prostaglandin E2, leukotriene B4, 12- and 15-hydroxyeicosatetraenoic acids. MPM prelabelled with 3H-AA showed an enhanced release when exposed to NPLA. Thus, it is concluded that NPLA potentiates AA release from cell membrane phospholipids and the subsequent cyclooxygenase and lipoxygenase oxidative metabolism of this precursor to various eicosanoids. This is in agreement with the implication of peroxidative process mediated by fatty acids anilides in TOS. 相似文献
995.
996.
G Appel A Briese K von Holleben G von Mickwitz M von Wenzlawowicz 《Canadian Metallurgical Quarterly》1995,102(6):233-234
It is reported on the fatal accident of a horse due to a cross-beam too low above the door of the stable, in which the animal suffered several skull fractures and a tear of the musculus longus capitis from the base of the skull. The aim of this article is, to supply a contribution to the establishment of minimal requirements for the housing of horses, in this case for the request of the minimum height of stable doors and ceilings as well as for constructions on horse transporters. On the grounds of this example, the natural behaviour of horses is discussed at the hand of the literature and the efforts are shown to improve the existing inadequacies in the housing and transport of horses with regard to the judicial situation. In the light of section 2 of the animal protection law, as to the construction of horse stables the importance is especially emphasized to consider the panic behaviour in connection with abrupt flight reactions as physiologic in the prevention of accidents. 相似文献
997.
G Arepally C Reynolds A Tomaski J Amiral A Jawad M Poncz DB Cines 《Canadian Metallurgical Quarterly》1995,104(6):648-654
The diagnosis of heparin-induced thrombocytopenia (HIT) may be affirmed by demonstrating heparin-dependent anti-platelet antibodies using the 14C-serotonin release assay (SRA). In this study, results of the SRA was compared with the recently described platelet factor 4 (PF4)/heparin enzyme-linked immunosorbent assay (ELISA). Compared with the SRA, the sensitivity and specificity of a PF4/heparin ELISA was 87% and 92%, respectively, using an assay developed in our laboratory; and 90% and 98%, respectively, using a commercially developed kit (Diagnostica Stago, Asnieres, France). However, antibodies to PF4/heparin were also detected in up to 8% of patients whose plasma was negative by SRA, and 23% of patients receiving heparin who were not thrombocytopenic. These data indicate that results obtained with the PF4/heparin ELISA and the SRA are generally in accord in patients with a clinical diagnosis of HIT. However, discrepant results occur in approximately 20% of cases because of the greater sensitivity of ELISA and the possible involvement of other heparin-binding proteins. The fact that each assay contributes independent information in some cases must be considered in the sequence of test performance and in providing consultation to the practicing hematologist. 相似文献
998.
999.
1000.
G Bottino G Antognozzi R Degrandi C Augeri G Bogliolo P Zoccali 《Canadian Metallurgical Quarterly》1995,17(2-3):63-66
Blood concentration of endogenous beta-endorphines can change during the clinical evolution of chronic bronchopneumopathies. The authors assessed the beta-endorphine concentrations in the pulmonary arterial and systemic arterial blood in 8 asthmatic patients during a symptom-free period and after methacholine-induced bronchospasm. The beta-endorphine analysis was performed in duplicate dor each sample, by means of a RIA assay. There is not difference in the systemic arterial blood concentration of beta-endorphines between asthmatic patients and normal subjects. Furthermore, there is no change in the beta-endorphine blood concentration during the passage through the pulmonary tissue after methacoline-induced bronchospasm. 相似文献