全文获取类型
收费全文 | 31878篇 |
免费 | 1215篇 |
国内免费 | 113篇 |
专业分类
电工技术 | 411篇 |
综合类 | 231篇 |
化学工业 | 5613篇 |
金属工艺 | 677篇 |
机械仪表 | 663篇 |
建筑科学 | 1032篇 |
矿业工程 | 95篇 |
能源动力 | 1023篇 |
轻工业 | 4339篇 |
水利工程 | 258篇 |
石油天然气 | 162篇 |
武器工业 | 6篇 |
无线电 | 2324篇 |
一般工业技术 | 4438篇 |
冶金工业 | 7673篇 |
原子能技术 | 250篇 |
自动化技术 | 4011篇 |
出版年
2024年 | 57篇 |
2023年 | 166篇 |
2022年 | 551篇 |
2021年 | 854篇 |
2020年 | 577篇 |
2019年 | 670篇 |
2018年 | 769篇 |
2017年 | 842篇 |
2016年 | 813篇 |
2015年 | 615篇 |
2014年 | 937篇 |
2013年 | 1605篇 |
2012年 | 1416篇 |
2011年 | 1722篇 |
2010年 | 1283篇 |
2009年 | 1343篇 |
2008年 | 1209篇 |
2007年 | 1058篇 |
2006年 | 851篇 |
2005年 | 883篇 |
2004年 | 941篇 |
2003年 | 856篇 |
2002年 | 832篇 |
2001年 | 724篇 |
2000年 | 561篇 |
1999年 | 595篇 |
1998年 | 2521篇 |
1997年 | 1566篇 |
1996年 | 1107篇 |
1995年 | 709篇 |
1994年 | 555篇 |
1993年 | 623篇 |
1992年 | 239篇 |
1991年 | 294篇 |
1990年 | 243篇 |
1989年 | 217篇 |
1988年 | 221篇 |
1987年 | 183篇 |
1986年 | 179篇 |
1985年 | 193篇 |
1984年 | 133篇 |
1983年 | 97篇 |
1982年 | 121篇 |
1981年 | 127篇 |
1980年 | 130篇 |
1979年 | 92篇 |
1978年 | 78篇 |
1977年 | 172篇 |
1976年 | 290篇 |
1975年 | 88篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
91.
92.
93.
94.
95.
EM de Kleijn WJ Oyen RA Claessens FH Corstens JW van der Meer 《Canadian Metallurgical Quarterly》1995,155(18):1989-1994
BACKGROUND: We assessed the utility of scintigraphy with indium 111-labeled polyclonal human IgG scintigraphy in patients with fever of unknown origin that fulfilled the criteria of temperature of 38.3 degrees C or more for at least 3 weeks and no diagnosis during 1 week of hospital admission. We compared the utility of this technique with results of scintigraphic techniques reported in the literature. METHODS: Data for all patients seen at our university hospital in whom 111In-IgG scanning was performed were analyzed and checked for the criteria for fever of unknown origin. The literature on the utility of scintigraphic techniques in patients with fever of unknown origin was reviewed. RESULTS: We studied 24 patients with fever of unknown origin. In 13 patients, focal 111In-IgG accumulation was observed. In nine (38%) of those, the positive 111In-IgG scintigram led to the final diagnosis; in the other four patients (17%), the scintigraphic findings were not helpful. In the 11 patients with negative 111In-IgG scans, extensive diagnostic workup produced no infection as the final diagnosis in nine patients (38%), one had an abscess in a renal cyst that was detected several months later, and in the other the cause of fever was an infected intravenous line. The overall sensitivity and specificity of 111In-IgG scintigraphy were 81% and 69%, respectively. The positive predictive value was 69% and the negative predictive value was 82%. CONCLUSIONS: Our results show that 111In-IgG scintigraphy significantly contributed to the diagnostic process in patients with fever of unknown origin. A positive scan increased the likelihood of finding the cause of the fever, and a negative scan ruled out an inflammatory component with a high degree of certainty. These data compare favorably with data in the literature concerning other radiopharmaceuticals; a larger prospective evaluation of this technique is indicated. 相似文献
96.
97.
98.
J Barreto J Liljestrand C Palha de Sousa S Bergstr?m B B?ttiger G Biberfeld F De la Cruz 《Canadian Metallurgical Quarterly》1993,25(6):685-688
The seroprevalence of HIV-1 and HIV-2 among pregnant women in Maputo, the capital of Mozambique, was compared between the years 1982/83, 1988 and 1990. None of the 432 serum samples collected in 1982/83 was positive for HIV antibodies whereas in 1988 the HIV-1 and HIV-2 seroprevalence was 0.4% (2/500) and 0.6% (3/500), respectively, and in 1990 0.6% (12/2014) and 0.2% (4/2014), respectively. These results indicate that HIV infection has been introduced recently in Maputo and is spreading at a slow rate among women. 相似文献
99.
PURPOSE: To demonstrate a superselective intraarterial chemotherapy as a therapeutic alternative in the treatment of previously treated recurrent lymph node metastases in breast cancer. METHODS: 14 patients with recurrent lymph node metastases in cases of breast cancer were presented to be treated by intraarterial chemotherapy of 25 mg mitoxantrone/m2 over a period of 24 hours. In two patients with superclavicular lymph node involvement an intraarterial therapy could not be carried out because of a vascular connection to the anterior spinal artery. Involved lymph stations could be reached in superselective technique by side branches of the subclavian artery. Heparin coverage was given intravenously. Every patient had had surgery, radiation, systemic chemo- and hormonal therapy before and was now graded as inoperable. Therapy indication was given by local tumour-induced symptoms. RESULTS: In the 12 treated cases complete remission was seen in three, partial remission in 4, a steady state in two and a progressive disease in three. There were no complications or severe side effects. CONCLUSION: Intraarterial chemotherapy is an effective and well tolerated treatment in recurrent lymph node metastases in cases of breast cancer even if conventional therapies can no longer be used. 相似文献
100.