全文获取类型
收费全文 | 21052篇 |
免费 | 2291篇 |
国内免费 | 1137篇 |
专业分类
电工技术 | 1338篇 |
技术理论 | 1篇 |
综合类 | 1441篇 |
化学工业 | 3286篇 |
金属工艺 | 1428篇 |
机械仪表 | 1492篇 |
建筑科学 | 1628篇 |
矿业工程 | 659篇 |
能源动力 | 553篇 |
轻工业 | 1418篇 |
水利工程 | 499篇 |
石油天然气 | 1267篇 |
武器工业 | 236篇 |
无线电 | 2396篇 |
一般工业技术 | 2508篇 |
冶金工业 | 1130篇 |
原子能技术 | 360篇 |
自动化技术 | 2840篇 |
出版年
2024年 | 141篇 |
2023年 | 446篇 |
2022年 | 794篇 |
2021年 | 1034篇 |
2020年 | 843篇 |
2019年 | 708篇 |
2018年 | 732篇 |
2017年 | 832篇 |
2016年 | 750篇 |
2015年 | 1108篇 |
2014年 | 1359篇 |
2013年 | 1505篇 |
2012年 | 1600篇 |
2011年 | 1478篇 |
2010年 | 1335篇 |
2009年 | 1209篇 |
2008年 | 1120篇 |
2007年 | 1101篇 |
2006年 | 1072篇 |
2005年 | 855篇 |
2004年 | 556篇 |
2003年 | 489篇 |
2002年 | 483篇 |
2001年 | 426篇 |
2000年 | 377篇 |
1999年 | 343篇 |
1998年 | 259篇 |
1997年 | 216篇 |
1996年 | 211篇 |
1995年 | 172篇 |
1994年 | 151篇 |
1993年 | 101篇 |
1992年 | 99篇 |
1991年 | 64篇 |
1990年 | 59篇 |
1989年 | 42篇 |
1988年 | 47篇 |
1987年 | 27篇 |
1986年 | 38篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1977年 | 11篇 |
1976年 | 23篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1970年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
响洪甸抽水蓄能电站水下岩塞爆破施工要求高,技术新,难度大.由于施工准备充分,并进行了一系列材料及施工试验,工程进展顺利,排孔造孔、导洞药室开挖、药管与起爆体加工、装药与堵塞、网络施工、充水补气等工程施工质量符合设计要求,岩塞爆破准时成功起爆. 相似文献
43.
44.
This study examined the efficacy of task analysis training for case managers helping seriously mentally ill patients find roommates and housing. Behavioral objectives and task analysis were used to develop the task-oriented behavioral training program. Case managers were trained to use a checklist for every session with patients, which included the goal of the session, tasks required to accomplish that goal and lists of all the sub-tasks. The results of this study suggest that this methodology: (1) reduced the time required for patients to find roommates and housing; (2) increased the percentage of patients finding housing; and (3) decreased hospitalization rates occurring during the process of looking for roommates and housing. 相似文献
45.
介绍了一种石方开挖新技术--露天石方深孔水压爆破技术。用试验的方法,通过和常规石方爆破进行类比,从而研究了此项新技术在中型孔径小梯段应用条件下的各种爆破参数,并进行了定性和定量分析,得到了一些初步的结论。 相似文献
46.
Yu Long Author Vitae Kefei Chen Author Vitae Shengli Liu Author Vitae 《Computers & Electrical Engineering》2007,33(3):166-176
This paper proposes an identity-based threshold decryption scheme IB-ThDec and reduces its security to the Bilinear Diffie-Hellman problem. Compared with previous work, this conceals two pairing computations in the ciphertext validity verification procedure. The formal proof of security of this scheme is provided in the random oracle model. Additionally, we show that IB-ThDec can be applied to the threshold key escrow and the mediated cryptosystems. 相似文献
47.
48.
Sulfur in coal causes problems in coal processing and utilization, therefore the chemical beneficiation of coal has gained widespread attention. Using three coal samples with high sulfur content the effect of desulfurization has been studied. For Nantong coal containing 4.25% total sulfur under the condition sulfur reduction increased from 38.8% upto 62.4% the released sulfur was generally sulfate and pyrite, but the organic sulfur almost remained constant. When alkali treatment was performed at 370°C, organic sulfur removal of Donglin and Yanzhou coal was to 50.6% and 57.3% respectively. 相似文献
49.
Increased use of titanium alloys as biomaterials is occurring due to their lower modulus, superior biocompatibility and enhanced corrosion resistance when compared to more conventional stainless steels and cobalt-based alloys. These attractive properties were a driving force for the early introduction of alpha (cpTi) and alpha + beta (Ti-6A1-4V) alloys as well as for the more recent development of new Ti-alloy compositions and orthopaedic metastable beta titanium alloys. The later possess enhanced biocompatibility, reduced elastic modulus, and superior strain-controlled and notch fatigue resistance. However, the poor shear strength and wear resistance of titanium alloys have nevertheless limited their biomedical use. Although the wear resistance of beta-Ti alloys has shown some improvement when compared to alpha + beta alloys, the ultimate utility of orthopaedic titanium alloys as wear components will require a more complete fundamental understanding of the wear mechanisms involved. This review examines current information on the physical and mechanical characteristics of titanium alloys used in artifical joint replacement prostheses, with a special focus on those issues associated with the long-term prosthetic requirements, e.g., fatigue and wear. 相似文献
50.
We examined the effects of different cytokine combinations and culture conditions on the expansion and modulation of cell surface antigens of CD34+ derived dendritic cells (DCs), the most efficient antigen-presenting cells capable of stimulating resting T cells in the primary immune response. Cells with a dendritic morphology and expressing HLA-DR, CD1a, S100 and CD83 were maximally expanded under serum-free conditions with the addition of SCF, GM-CSF, TNF-alpha, TGF-beta and Flt-3 ligand (fold increase of CD1a+ cells = 102 +/- 32 after 2 weeks of culture). CD34+ cells were also grown under continuous flow conditions in an artificial capillary system: after 14d of culture, the expansion in the total cell number was lower than that of the static cultures (3.3 +/- 2 v 18.9 +/- 4) but the percentage of CD1a+/CD83+/ CD80+ cells was considerably higher, whereas the CD14+ cells were significantly reduced (8.9 +/- 2 v 26 +/- 13). In continuous perfusion cultures, low levels of DC precursors and of LTC-IC were still present up to day 14. The DCs generated under flow conditions stimulated the mixed leucocyte reaction (MLR) more than the cells grown in static cultures. By electron microscopy, cells grown in the continuous flow system showed an increased number of large cells with numerous dendritic processes and abundant multilamellar complexes. The cells expanded under these conditions were sorted on the basis of their light-scatter properties into two fractions: one containing a predominance of CD1a+/S100+/ CD8 3+/CD80+/CD14- 'large cells' with great internal complexity (mature DCs); the second including 'small cells' either CD33+/CD14+, CD33+/CD15+ or CD33+/CD13-/CD14. The DCs generated and selected with this method are therefore particularly well suited for immunotherapeutic protocols. 相似文献