全文获取类型
收费全文 | 709532篇 |
免费 | 10306篇 |
国内免费 | 3024篇 |
专业分类
电工技术 | 13714篇 |
技术理论 | 5篇 |
综合类 | 1676篇 |
化学工业 | 108607篇 |
金属工艺 | 27552篇 |
机械仪表 | 20584篇 |
建筑科学 | 17650篇 |
矿业工程 | 3652篇 |
能源动力 | 18399篇 |
轻工业 | 63544篇 |
水利工程 | 7248篇 |
石油天然气 | 13455篇 |
武器工业 | 280篇 |
无线电 | 78985篇 |
一般工业技术 | 135409篇 |
冶金工业 | 138502篇 |
原子能技术 | 14071篇 |
自动化技术 | 59529篇 |
出版年
2021年 | 6688篇 |
2020年 | 4771篇 |
2019年 | 6003篇 |
2018年 | 9977篇 |
2017年 | 9767篇 |
2016年 | 10405篇 |
2015年 | 7585篇 |
2014年 | 12285篇 |
2013年 | 32460篇 |
2012年 | 19908篇 |
2011年 | 27231篇 |
2010年 | 21510篇 |
2009年 | 23603篇 |
2008年 | 24690篇 |
2007年 | 24458篇 |
2006年 | 21441篇 |
2005年 | 19252篇 |
2004年 | 18034篇 |
2003年 | 17528篇 |
2002年 | 16964篇 |
2001年 | 17053篇 |
2000年 | 15866篇 |
1999年 | 16607篇 |
1998年 | 41752篇 |
1997年 | 29610篇 |
1996年 | 22549篇 |
1995年 | 16890篇 |
1994年 | 14929篇 |
1993年 | 14571篇 |
1992年 | 10707篇 |
1991年 | 10057篇 |
1990年 | 9959篇 |
1989年 | 9738篇 |
1988年 | 9043篇 |
1987年 | 7962篇 |
1986年 | 7902篇 |
1985年 | 8790篇 |
1984年 | 8346篇 |
1983年 | 7446篇 |
1982年 | 6925篇 |
1981年 | 7151篇 |
1980年 | 6678篇 |
1979年 | 6709篇 |
1978年 | 6433篇 |
1977年 | 7456篇 |
1976年 | 9870篇 |
1975年 | 5681篇 |
1974年 | 5285篇 |
1973年 | 5440篇 |
1972年 | 4466篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal 相似文献
72.
73.
74.
75.
M Camilleri 《Canadian Metallurgical Quarterly》1996,25(2):361-378
Gastrointestinal symptoms are often encountered in patients with diabetes mellitus. Symptoms may arise in any region of the alimentary tract; common symptoms are heartburn, nausea, vomiting, diarrhea, constipation, fecal incontinence, and abdominal pain. This article reviews practical approaches to the identification of the pathophysiologic mechanisms involved in diabetic enteropathies and their complications and briefly outlines strategies to treat these symptoms. Particular emphasis is placed on applied physiologic tests and the choice of pharmacotherapy (e.g., cisapride, erythromycin, or octeotide). The current role of pancreatic transplantations also is briefly reviewed. 相似文献
76.
Laparoscopic retroperitoneal lymph node dissection is a new surgical procedure used to enhance staging in men with clinical stage I nonseminomatous germ cell tumors of the testis. The procedure has been performed in a limited number of patients at several centers with extensive laparoscopic experience. Laparoscopic retroperitoneal lymphadenectomy is a technically demanding procedure which can be successfully completed in the majority of patients. However, the risk of complications is greater than in patients who undergo standard open retroperitoneal lymph node dissection. The primary advantage of a laparoscopic approach is shortened hospitalization and rapid return to normal activity. The role of laparoscopy in the management of patients with testis malignancy has not been defined. The use of this staging procedure may help minimize the need for surveillance studies following surgery and may be best utilized in men with a lower likelihood of nodal metastases. Ultimately, prospective study in large groups of patients will be necessary to determine the role of laparoscopic retroperitoneal lymph node dissection in patients with testis cancer. 相似文献
77.
The present study has been divided into two sets. In the first set, the aim of the experiments was to investigate the dose-response effect of selective serotonin re-uptake inhibitor (SSRI) citalopram on rat exploratory behaviour in the elevated plus-maze. In the second set of experiments, the effect of cholecystokinin (CCK) CCKA and CCKB receptor antagonists, devazepide and L 365260, on citalopram-induced decrease of exploratory behaviour in the elevated plus-maze was studied. Citalopram (5 and 10 mg/kg) decreased the number of open and total arm entries, line crossings on open arms, and percentage of time spent exploring in open arm. Dose 15 mg/kg was without any effect on rat exploratory behaviour. Devazepide (0.01 and 1.0 mg/kg) failed to modify any of the citalopram-induced changes observed. L 365260 (1.0 mg/kg) reversed most of the effects of citalopram: the numbers of open and total arm entries, the number of line crossings, and the percentage of time spent exploring in open arms. L 365260 at dose level 0.01 mg/kg was ineffective. These results support the involvement of the CCKB receptor subtype in SSRI-induced anxiogenic-like effects in rodents. 相似文献
78.
The metabolism of the poly(A) tail is a process important for the translational regulation of maternal mRNAs in Xenopus laevis oocytes and early embryos. Two poly(A) nuclease (PAN) activities have been described in Xenopus embryo or activated egg extracts (Legagneux et al (1995) RNA 1, 1001-1008). These activities (default PAN and EgPAN) are distinguishable by their deadenylation kinetics and their substrate specificities. In this report, we show that these activities display different sensitivities to biochemical treatments. Urea and, to a lesser extent, spermidine, inhibit EgPAN at concentrations which have no effect on default PAN. Heparin activates default PAN but inhibits EgPAN. When extracts are fractionated by ultracentrifugation, the default activity is recovered in one unique fraction, whereas two fractions must be combined to reconstitute the EgPAN activity. Moreover, these two deadenylation activities are separable by size exclusion chromatography under native conditions. We conclude that these two deadenylation activities are mediated by two protein complexes. 相似文献
79.
Known examples of the positive influence of electrohydroimpulse treatment on the quality of weld joints of various steels, particularly including an increase in their long-term and cyclic strength and also corrosion resistance, are analyzed. It is shown that in this case there is a reduction in residual macro- and micro-stresses and also a change in the parameters of the dislocation structure of the joint metal in the direction of stabilization of it.Translated from Problemy Prochnosti, No. 4, pp. 119–123, April, 1996. 相似文献
80.
In a prospective study we found good results concerning postoperative complications (21%), perioperative lethality (3.2%) and lethality during hospital stay (6.5%) after implantation of dynamic hip screws (DHS) in patients with per- and subtrochanteric fractures of the femur. The ability to walk, as well as housing and social care postoperatively and follow-up for at least six months after dismissal demonstrates the importance of these fractures for the elderly. One of three patients needs professional care, 21% at home, 13% in nursing homes. Six months after operation the lethality is nearly 20%, i.e. three times higher than in hospital. These are the essential data for all techniques of osteosynthesis used in patients with these fractures, which could only be documented in prospective studies. 相似文献