全文获取类型
收费全文 | 24205篇 |
免费 | 820篇 |
国内免费 | 318篇 |
专业分类
电工技术 | 465篇 |
综合类 | 543篇 |
化学工业 | 3800篇 |
金属工艺 | 528篇 |
机械仪表 | 733篇 |
建筑科学 | 864篇 |
矿业工程 | 183篇 |
能源动力 | 571篇 |
轻工业 | 2128篇 |
水利工程 | 248篇 |
石油天然气 | 182篇 |
武器工业 | 27篇 |
无线电 | 2376篇 |
一般工业技术 | 2815篇 |
冶金工业 | 6842篇 |
原子能技术 | 170篇 |
自动化技术 | 2868篇 |
出版年
2023年 | 110篇 |
2022年 | 343篇 |
2021年 | 473篇 |
2020年 | 276篇 |
2019年 | 342篇 |
2018年 | 389篇 |
2017年 | 369篇 |
2016年 | 406篇 |
2015年 | 352篇 |
2014年 | 530篇 |
2013年 | 1028篇 |
2012年 | 808篇 |
2011年 | 996篇 |
2010年 | 762篇 |
2009年 | 826篇 |
2008年 | 811篇 |
2007年 | 830篇 |
2006年 | 717篇 |
2005年 | 614篇 |
2004年 | 690篇 |
2003年 | 904篇 |
2002年 | 1194篇 |
2001年 | 1020篇 |
2000年 | 592篇 |
1999年 | 603篇 |
1998年 | 2254篇 |
1997年 | 1393篇 |
1996年 | 1025篇 |
1995年 | 661篇 |
1994年 | 476篇 |
1993年 | 533篇 |
1992年 | 214篇 |
1991年 | 190篇 |
1990年 | 172篇 |
1989年 | 163篇 |
1988年 | 154篇 |
1987年 | 128篇 |
1986年 | 132篇 |
1985年 | 169篇 |
1984年 | 86篇 |
1983年 | 95篇 |
1982年 | 101篇 |
1981年 | 127篇 |
1980年 | 131篇 |
1979年 | 64篇 |
1978年 | 58篇 |
1977年 | 231篇 |
1976年 | 446篇 |
1975年 | 60篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
JA Koutcher AA Alfieri RL Stolfi ML Devitt JR Colofiore LD Nord DS Martin 《Canadian Metallurgical Quarterly》1993,53(15):3518-3523
The combination of N-(phosphonacetyl)-L-aspartate, 6-methylmercaptopurine, and 6-aminonicotinamide has been shown to be an effective antineoplastic regimen and also to enhance the effects of other chemotherapeutic agents. The mechanism of action of this combination of drugs is not known definitively, but one possible mechanism is biochemical modulation of energy metabolism and inhibition of production of tumor ATP. Tumor-bearing mice were treated with N-(phosphonacetyl)-L-aspartate, followed 17 h later by 6-methylmercaptopurine and 6-aminonicotinamide. 31P nuclear magnetic resonance spectroscopic studies demonstrated a significant depletion of high energy phosphates at 10 h post-6-methylmercaptopurine and 6-aminonicotinamide. The addition of radiation at this time was shown to induce a significantly longer tumor growth delay and a greater number of regressions (including durable complete regressions) than either chemotherapy or radiation alone. The combination of chemotherapy and radiation was found to be supra-additive compared to the antineoplastic effects of either modality administered separately, without a measurable increase in host toxicity. 相似文献
42.
43.
AM De Mattos MA Head J Everett J Hosenpud R Hershberger A Cobanoglu G Ott R Ratkovec DJ Norman 《Canadian Metallurgical Quarterly》1994,57(4):626-630
To determine if cardiac allograft outcome is improved among patients with fewer HLA-DR mismatches with their donors, we studied 132 recipients of a primary cardiac allograft who were transplanted between December 1985 and December 1991. These recipients and their donors all had high-confidence-level serological HLA-DR typing, previously shown to correlate highly with DNA DR typing. Patients were divided in two groups based on the HLA-DR mismatch with their donors. Group I consisted of 78 patients with 1 or zero DR mismatch and group II of 54 patients with 2 DR mismatches. Allograft outcome measurements included incidence of moderate rejection, incidence of allograft vasculopathy at 12 months, cardiac function measured as left ventricular ejection fraction (LVEF) and cardiac index (CI), and actuarial graft survival up to 7 years. Groups I and group II were not different with regard to recipient age, donor age, ischemia time, pulmonary vascular resistance, sex, or PRA greater than 0%. Group II had a higher incidence of moderate rejection on the first-week biopsy (47% vs. 25%, P = 0.019), and during the first month (84% vs. 58%, P = 0.006), but no difference was found in frequency of rejection from months 2 to 12. LVEF was not different in the groups at any point. CI was better in group I at 12 months (2.76 vs. 2.5, P = 0.03). No statistically significant difference was found in incidence of allograft vasculopathy (17% vs. 26%, P = 0.204). Actual graft survival at 1 year was better for group I (91% vs. 74%, P = 0.008), and actuarial graft survival at 6 years also favored group I (76% vs. 56%, P = 0.04). Using high-confidence-level serological HLA-DR typing assignments we demonstrated that HLA-DR mismatching correlates highly with cardiac allograft outcome. Implications are that heart transplant survival could be improved if prospective matching were feasible and prioritized or if immunosuppression were tailored to the HLA-DR match. 相似文献
44.
45.
46.
Aard J. Groen Petra C. De WeerdNederhof Inge C. Kerssensvan Drongelen Rob A.J. Badoux Gerard P.H. Olthuis 《Creativity & Innovation Management》2002,11(1):2-16
In this paper we describe a framework for analysing the creation and justification of Research & Development. The 4S framework is developed for analysing the scope, scale, skills and social network aspects of Research & Development value. The framework is based on social system theory, a process contingency model, and recent Research & Development metrics. We present a first empirical assessment based on a workshop using the 4S framework for leveraging Research & Development. Results that assist in the assessment of value creation utilising R & D within networks are very relevant in high tech industries. The multi–dimensional process approach of this framework seems promising for understanding and managing R&D value creation, but needs further operationalisation. Case studies are described and a Dutch network on leveraging R&D has been initiated. 相似文献
47.
Orthopedists being more engaged in surgery are often asked about problems concerning exercise science. This article will summarize the existing basic knowledge, very close to practice, and put down the leading steps of how to build up a (therapeutical) training programme. A lab block is recommended acting on a preventive as well as on a sportive medical base. 相似文献
48.
AA Skolnick 《Canadian Metallurgical Quarterly》1993,270(11):1283-1284
49.
During the day, there are considerable variations in the climatic factors prevailing in these regions. This is especially so during the 24-hour daily cycle of the long, hot and dry summer (mid-May to midOctober). Such climatic conditions have had a considerable impact on the daily living pattern of family life in the same season, particularly in the urban areas. During the same 24-hour cycle, they have compelled the inhabitants to shift their living activities both vertically in section and horizontally in plan; they do this in pursuit of more acceptable, if not, desirable internal thermal environmental ambience. 相似文献
50.
R Santinelli C Tolone R Toraldo G Canino A De Simone M D'Avanzo 《Canadian Metallurgical Quarterly》1998,55(6):854-856
OBJECTIVE: To describe a mother and her 2 sons affected by idiopathic intracranial hypertension (IIH), associated in the sons with root irritation symptom. Unlike the other 4 families reported previously, obesity was not present in our patients. DESIGN: Case reports. SETTING: Department of pediatrics in a university school of Medicine, Naples, Italy. PATIENTS: A mother (aged 36 years) and her 2 sons (aged 14 and 9 years) developed IIH at different times. Neuroimaging showed an empty sella in the mother, while IIH was associated with spinal and radicular pain in her 2 sons. The mother and the younger son developed permanent visual loss. CONCLUSIONS: Ophthalmologic follow-up in our patients indicates that IIH is a chronic disease. Surgical treatment should be considered an option. 相似文献