全文获取类型
收费全文 | 664731篇 |
免费 | 8669篇 |
国内免费 | 1909篇 |
专业分类
电工技术 | 11998篇 |
综合类 | 641篇 |
化学工业 | 99079篇 |
金属工艺 | 25455篇 |
机械仪表 | 19284篇 |
建筑科学 | 16060篇 |
矿业工程 | 3302篇 |
能源动力 | 18106篇 |
轻工业 | 58207篇 |
水利工程 | 6803篇 |
石油天然气 | 11919篇 |
武器工业 | 43篇 |
无线电 | 75553篇 |
一般工业技术 | 128779篇 |
冶金工业 | 130954篇 |
原子能技术 | 13764篇 |
自动化技术 | 55362篇 |
出版年
2021年 | 5954篇 |
2020年 | 4309篇 |
2019年 | 5545篇 |
2018年 | 9460篇 |
2017年 | 9288篇 |
2016年 | 9751篇 |
2015年 | 6751篇 |
2014年 | 11214篇 |
2013年 | 30396篇 |
2012年 | 17807篇 |
2011年 | 24613篇 |
2010年 | 19443篇 |
2009年 | 21905篇 |
2008年 | 22388篇 |
2007年 | 22050篇 |
2006年 | 19249篇 |
2005年 | 17662篇 |
2004年 | 16953篇 |
2003年 | 16743篇 |
2002年 | 15730篇 |
2001年 | 15956篇 |
2000年 | 14989篇 |
1999年 | 15882篇 |
1998年 | 40664篇 |
1997年 | 28629篇 |
1996年 | 21964篇 |
1995年 | 16342篇 |
1994年 | 14364篇 |
1993年 | 13952篇 |
1992年 | 10197篇 |
1991年 | 9622篇 |
1990年 | 9372篇 |
1989年 | 9145篇 |
1988年 | 8563篇 |
1987年 | 7586篇 |
1986年 | 7335篇 |
1985年 | 8291篇 |
1984年 | 7766篇 |
1983年 | 6963篇 |
1982年 | 6437篇 |
1981年 | 6621篇 |
1980年 | 6210篇 |
1979年 | 6185篇 |
1978年 | 6009篇 |
1977年 | 7104篇 |
1976年 | 9483篇 |
1975年 | 5167篇 |
1974年 | 4869篇 |
1973年 | 4948篇 |
1972年 | 4060篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
82.
83.
84.
Dissolved organic carbon (DOC) dynamics were investigated over a two year period in the Upper Rhǒne River to examine the role of side-arms in providing DOC to the main channel in relation to discharge fluctuations, especially floods. Concentrations of DOC are shown to remain low in space and in time (average 1.5 mg ?1) and to be more related to global hydrological events (precipitation) than to any local flushing for backwaters during floods. The results do not support the general assumption that side-arms are the providers of DOC to the main channel. 相似文献
85.
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
86.
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
87.
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
88.
89.
B Ljunggren 《Canadian Metallurgical Quarterly》1993,78(1):142-149
Herbert Olivecrona (1891-1980) singlehandedly founded Swedish neurosurgery. At the International Congress in Neurology in Bern in August, 1931, Harvey Cushing invited the cream of the world's medical society to a private banquet. Among the 28 specially invited guests was Herbert Olivecrona. At 40 years old, Olivecrona took his seat with pioneers such as Otfrid Foerster, Percival Bailey, Hugh Cairns, Geoffrey Jefferson, and Sir Charles Sherrington. This suggests that Cushing was impressed by the Swedish aristocrat's didactic deeds when he visited the Serafimer Hospital in Stockholm 2 years earlier. During the mid-1920's, the radiologist Erik Lysholm greatly improved the technique of ventriculography and, challenged by Olivecrona, his diagnostic neuroradiology became of superior quality. In the early 1930's, utilizing technical innovations of his own, Lysholm became a master at demonstrating and localizing posterior fossa tumors, which Olivecrona then operated on. Olivecrona's clinic became the mecca to which many scholars, thirsting for more knowledge, went on a pilgrimage. The international reputation of the clinic was founded, not on epoch-making discoveries, but by the resolute and practical application of methods already launched elsewhere and the exemplary organization that Olivecrona had established in collaboration with Lysholm. In spite of hardships and primitive working conditions, the clinic at the Serafimer Hospital gradually developed into the ideal prototype for a modern neurosurgical department. Olivecrona trained many colorful personalities who later were to lay the foundation for neurosurgery in their home countries; these included Wilhelm T?nnis of Germany, Edvard Busch of Denmark, and Aarno Snellman of Finland. Olivecrona was a true pioneer who made major contributions in practically all fields of conventional neurosurgery. 相似文献
90.