全文获取类型
收费全文 | 12360篇 |
免费 | 1300篇 |
国内免费 | 793篇 |
专业分类
电工技术 | 1029篇 |
综合类 | 1356篇 |
化学工业 | 1521篇 |
金属工艺 | 697篇 |
机械仪表 | 709篇 |
建筑科学 | 712篇 |
矿业工程 | 503篇 |
能源动力 | 364篇 |
轻工业 | 1262篇 |
水利工程 | 352篇 |
石油天然气 | 380篇 |
武器工业 | 239篇 |
无线电 | 1118篇 |
一般工业技术 | 965篇 |
冶金工业 | 1663篇 |
原子能技术 | 294篇 |
自动化技术 | 1289篇 |
出版年
2024年 | 81篇 |
2023年 | 212篇 |
2022年 | 467篇 |
2021年 | 557篇 |
2020年 | 463篇 |
2019年 | 288篇 |
2018年 | 321篇 |
2017年 | 343篇 |
2016年 | 298篇 |
2015年 | 498篇 |
2014年 | 620篇 |
2013年 | 780篇 |
2012年 | 923篇 |
2011年 | 944篇 |
2010年 | 947篇 |
2009年 | 827篇 |
2008年 | 860篇 |
2007年 | 890篇 |
2006年 | 654篇 |
2005年 | 589篇 |
2004年 | 455篇 |
2003年 | 281篇 |
2002年 | 256篇 |
2001年 | 221篇 |
2000年 | 206篇 |
1999年 | 101篇 |
1998年 | 360篇 |
1997年 | 242篇 |
1996年 | 154篇 |
1995年 | 83篇 |
1994年 | 75篇 |
1993年 | 77篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 11篇 |
1986年 | 16篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1977年 | 55篇 |
1976年 | 102篇 |
1961年 | 7篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
LG Westergaard PE Rasmussen S Maigaard HJ Ingerslev AN Andersen JF Larsen J Starup PJ Hornnes CY Andersen 《Canadian Metallurgical Quarterly》1993,155(33):2511-2514
Medical indications for in vitro fertilization and embryo transfer (IVF-ET) internationally and in Denmark are reviewed. Reports from large international centres document that tubal infertility, unexplained infertility, endometriosis and male infertility are equally good indications for IVF. Traditionally, tubal infertility has been the only medical indication qualifying for IVF treatment within the National Health Service in Denmark. Thus, in this country, couples with unexplained and male infertility and with endometriosis have to pay up to 25,000 D.Kr. per IVF-ET treatment in private fertility clinics. Since there is no scientific basis for this discrimination, it is urged that the present rules are changed, so that couples with unexplained and male infertility and endometriosis are also allowed IVF treatment free of charge in the public fertility clinics. 相似文献
22.
网格曲面中孔洞的光滑填充算法研究 总被引:14,自引:0,他引:14
三角网格模型是几何描述的一种重要形式,有着广泛的应用。但三角网络模型常常会存在孔洞缺陷。这些孔洞的存在一方面影响视觉效果,另一方面会影响许多后续的操作,如快速原型制造、有限元分析等,因此有必要对这些孔洞进行修补。目前绝大多数孔洞填充算法是将网格模型中的孔洞提取成空间多边形,并对孔洞多边形进行三角化。这种处理方法的主要缺陷是没有考虑网格曲面在孔洞附近的几何形态,因而填充部分不能与整个曲面光滑地融为一体。笔者提出了一种三角网格曲面中孔洞的光滑填充算法。该算法根据孔洞周围网格曲面的几何信息来增加孔洞内部的采样点,然后再对增加的采样点进行三角化,较好地解决了填充部分与整体曲面光滑连接的问题。 相似文献
23.
24.
25.
26.
AN Reshetilov DA Efremov PV Iliasov AM Boronin NI Kukushskin RV Greene TD Leathers 《Canadian Metallurgical Quarterly》1998,13(7-8):795-799
Amperometric biosensors register oxygen depletion in response to analyte catabolism, and thus are limited by the availability of dissolved oxygen. Microbial sensors containing immobilized cells of Gluconobacter oxydans were hyperoxygenated to 400% of control levels and the effects on sensor responses to glucose were determined. Oxygenated perfluorodecalin (a completely fluorinated organic substance) was as effective in hyperoxygenation as direct sparging with O2, increasing sensor base medium oxygen concentrations from 9.3 to 37 mg/l. Hyperoxygenation enhanced maximal biosensor response amplitudes, particularly at high cell loading densities. Maximal response rates were also improved, although less dramatically. Results suggest that hyperoxygenation may be a new general approach for modulating biosensor responses. 相似文献
27.
28.
EA.hy 926 cells, a human endothelial cell line, show characteristics of differentiated endothelial cells. The cells express saturable binding of apo E-free 125I-high density lipoprotein3 (HDL3). Bmax increased from 71 to 226 ng HDL3 bound/mg cell protein after cholesterol loading of the confluent endothelial cells with cationized low density lipoprotein (LDL). The affinity did not change after cholesterol enrichment (Kd was 37 micrograms HDL3 protein/ml for control cells and 31 micrograms/ml for loaded cells). Incubation of cholesterol-loaded EA.hy 926 cells with native HDL and LDL had different effects on cellular cholesterol levels. Incubation with HDL decreased both esterified and unesterified cellular cholesterol, but LDL did not change total cellular cholesterol. However, LDL tended to increase cellular cholesteryl esters, with a concomitant decrease of unesterified cellular cholesterol. Incubation of endothelial cells with both HDL and LDL also resulted in decreased total cellular cholesterol levels. These data show that cationized LDL-loaded human endothelial EA.hy 926 cells can be used to study the net transport of cellular cholesterol to HDL, the first step in reverse cholesterol transport. 相似文献
29.
JC Mohle-Boetani JE Koehler TG Berger PE LeBoit CA Kemper AL Reingold BD Plikaytis JD Wenger JW Tappero 《Canadian Metallurgical Quarterly》1996,22(5):794-800
Clinical characteristics associated with bacillary angiomatosis and bacillary peliosis (BAP) in patients with human immunodeficiency virus (HIV) infection were evaluated in a case-control study; 42 case-patients and 84 controls were matched by clinical care institution. Case-patients presented with fever (temperature, > 37.8 degrees C; 93%), a median CD4 lymphocyte count of 21/mm3, cutaneous or subcutaneous vascular lesions (55%), lymphadenopathy (21%), and/or abdominal symptoms (24%). Many case-patients experienced long delays between medical evaluation and diagnosis of BAP (median, 4 weeks; range, 1 day to 24 months). Case-patients were more likely than controls to have fever, lymphadenopathy, hepatomegaly, splenomegaly, a low CD4 lymphocyte count, anemia, or an elevated serum level of alkaline phosphatase (AP) (P < .001). In multivariate analysis, a CD4 lymphocyte count of < 200/mm3 (matched odds ratio [OR], 9.9; P < .09), anemia reflected by a hematocrit value of < 0.36 (OR, 19.7; P < .04), and an elevated AP level of > or = 2.6 mukat/L (OR, 23.9; P < .05) remained associated with disease after therapy with zidovudine was controlled for. BAP should be considered an AIDS-defining opportunistic infection and should be included in the differential diagnosis for febrile, HIV-infected patients with cutaneous or osteolytic lesions, lymphadenopathy, abdominal symptoms, anemia, or an elevated serum level of AP. 相似文献
30.