全文获取类型
收费全文 | 38763篇 |
免费 | 2472篇 |
国内免费 | 1273篇 |
专业分类
电工技术 | 1726篇 |
技术理论 | 1篇 |
综合类 | 1937篇 |
化学工业 | 5594篇 |
金属工艺 | 1605篇 |
机械仪表 | 2116篇 |
建筑科学 | 2557篇 |
矿业工程 | 1009篇 |
能源动力 | 833篇 |
轻工业 | 1991篇 |
水利工程 | 549篇 |
石油天然气 | 2069篇 |
武器工业 | 212篇 |
无线电 | 3782篇 |
一般工业技术 | 3947篇 |
冶金工业 | 8048篇 |
原子能技术 | 379篇 |
自动化技术 | 4153篇 |
出版年
2024年 | 173篇 |
2023年 | 585篇 |
2022年 | 881篇 |
2021年 | 1261篇 |
2020年 | 930篇 |
2019年 | 842篇 |
2018年 | 924篇 |
2017年 | 989篇 |
2016年 | 866篇 |
2015年 | 1157篇 |
2014年 | 1539篇 |
2013年 | 1820篇 |
2012年 | 1946篇 |
2011年 | 2041篇 |
2010年 | 1793篇 |
2009年 | 1760篇 |
2008年 | 1615篇 |
2007年 | 1638篇 |
2006年 | 1779篇 |
2005年 | 1596篇 |
2004年 | 1020篇 |
2003年 | 939篇 |
2002年 | 893篇 |
2001年 | 782篇 |
2000年 | 894篇 |
1999年 | 1109篇 |
1998年 | 2703篇 |
1997年 | 1820篇 |
1996年 | 1418篇 |
1995年 | 913篇 |
1994年 | 778篇 |
1993年 | 709篇 |
1992年 | 305篇 |
1991年 | 302篇 |
1990年 | 254篇 |
1989年 | 206篇 |
1988年 | 196篇 |
1987年 | 137篇 |
1986年 | 111篇 |
1985年 | 87篇 |
1984年 | 17篇 |
1983年 | 29篇 |
1982年 | 54篇 |
1981年 | 60篇 |
1980年 | 60篇 |
1978年 | 26篇 |
1977年 | 180篇 |
1976年 | 350篇 |
1975年 | 10篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
K Bj?ro JP Blomhoff E Schrumpf F Brosstad A Bergan T Egge 《Canadian Metallurgical Quarterly》1997,117(9):1274-1276
Budd Chiari syndrome (liver vein thrombosis) may be a diagnostic and therapeutic problem. On the basis of four different cases we review the major diagnostic and therapeutic principles involved. Imaging techniques are necessary in order to establish the diagnosis. Ultrasound examination with Duplex doppler is usually sufficient, but MR angiography is also useful. Treatment options are thrombolysis, surgery or liver transplantation. What treatment is selected will depend on the clinical situation and the prognosis. 相似文献
43.
44.
OBJECTIVE: Our purpose was to study the heterogeneity of drug response in fresh human ovarian tumors to chemotherapeutic agents in an in vitro chemosensitivity assay. STUDY DESIGN: This assay evaluates total tumor cell kill by measuring the intracellular adenosine triphosphate levels of untreated controls and drug-exposed cells at various doses after culture for 6 days. The surviving fraction is calculated by dividing the treated values with the control values. One hundred tumors were tested against four single drugs (cisplatin, the active metabolite of cytoxan, 4-hydroxyperoxy-cyclophosphamide, Taxol, and carboplatin) and two drug combinations (cisplatin plus 4-hydroxyperoxy-cyclophosphamide; cisplatin plus Taxol). RESULTS: There is great variation in the degree of cell death for single drugs and drug combinations among the 100 tumors tested. CONCLUSION: More effective clinical response to chemotherapy may be achieved in patients with ovarian cancer by selecting the most active drugs for chemotherapy, on the basis of in vitro chemosensitivity test results for individual patients. 相似文献
45.
46.
热物理性质测试技术研究现状和发展趋势 总被引:3,自引:0,他引:3
本文在对热物理性质研究在热能工程、材料科学、信息科学、航天工程、环境工程、生物科学、微电子技术和计量学等众多科技领域中的重要性进行探讨的基础上,评述了热物理性质测试技术的研究现状和发展趋势。鉴于薄膜材料在微电子器件、集成电路和微电子机械系统等领域中日益广泛的应用,本文还综述了亚微米-纳米尺度薄膜材料热导率和热扩散率的测试新技术。 相似文献
47.
Mushroom-like ZnO microcrystals have been prepared via a solution calcination route, using Zn(NO3)2 as Zn source in the absence of any surfactants, templates or catalysts. This is the first example to prepare mushroom-like crystals as semiconductors, which are expected to show particular physical properties. The ZnO products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) spectrum measurements. A suitable concentration of Zn(NO3)2 solution was important for the growth of the mushroom-like products. The reported synthetic procedure is straightforward and inexpensive, and thus can be readily adopted to produce large quantities of mushroom-like ZnO microcrystals. 相似文献
48.
49.
50.
Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation. 相似文献