全文获取类型
收费全文 | 34740篇 |
免费 | 2313篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 255篇 |
综合类 | 19篇 |
化学工业 | 7333篇 |
金属工艺 | 674篇 |
机械仪表 | 732篇 |
建筑科学 | 964篇 |
矿业工程 | 80篇 |
能源动力 | 607篇 |
轻工业 | 5802篇 |
水利工程 | 324篇 |
石油天然气 | 126篇 |
武器工业 | 5篇 |
无线电 | 1304篇 |
一般工业技术 | 5987篇 |
冶金工业 | 8026篇 |
原子能技术 | 124篇 |
自动化技术 | 4722篇 |
出版年
2024年 | 64篇 |
2023年 | 311篇 |
2022年 | 416篇 |
2021年 | 951篇 |
2020年 | 726篇 |
2019年 | 826篇 |
2018年 | 1444篇 |
2017年 | 1377篇 |
2016年 | 1444篇 |
2015年 | 1128篇 |
2014年 | 1340篇 |
2013年 | 2820篇 |
2012年 | 2025篇 |
2011年 | 1845篇 |
2010年 | 1544篇 |
2009年 | 1385篇 |
2008年 | 1345篇 |
2007年 | 1224篇 |
2006年 | 846篇 |
2005年 | 723篇 |
2004年 | 677篇 |
2003年 | 588篇 |
2002年 | 589篇 |
2001年 | 430篇 |
2000年 | 399篇 |
1999年 | 443篇 |
1998年 | 2378篇 |
1997年 | 1621篇 |
1996年 | 1045篇 |
1995年 | 624篇 |
1994年 | 472篇 |
1993年 | 567篇 |
1992年 | 210篇 |
1991年 | 214篇 |
1990年 | 155篇 |
1989年 | 161篇 |
1988年 | 165篇 |
1987年 | 140篇 |
1986年 | 127篇 |
1985年 | 146篇 |
1984年 | 132篇 |
1983年 | 107篇 |
1982年 | 134篇 |
1981年 | 157篇 |
1980年 | 159篇 |
1979年 | 83篇 |
1978年 | 85篇 |
1977年 | 281篇 |
1976年 | 626篇 |
1973年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
Flávio A. Pavan Sidinei A. Gobbi Celso C. Moro Tania M.H. Costa Edilson V. Benvenutti 《Journal of Porous Materials》2002,9(4):307-311
Anilinepropylsilica hybrid powder was synthesized by a sol-gel route in basic medium using HF as catalyst. The effect of the amount of HF catalyst on the morphologies and on organic content was studied. The xerogels were characterized using FTIR, SEM and N2 adsorption-desorption isotherms. The increase in the HF quantity results in an slight increase in organic content and changes in the particle size, surface area and pore structure. 相似文献
152.
M Pan J Suárez de Lezo A Medina M Romero E Hernández J Segura F Melian F Wangüemert M Landin F Benítez M Amat F Velasco A Torres 《Canadian Metallurgical Quarterly》1997,80(10):1336-1338
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation. 相似文献
153.
154.
H Sánchez T Fester S Kloska W Schr?der W Schuster 《Canadian Metallurgical Quarterly》1996,15(9):2138-2149
The discovery of disrupted rps19 genes in Arabidopsis mitochondria prompted speculation about the transfer to the nuclear compartment. We here describe the functional gene transfer of rps19 into the nucleus of Arabidopsis. Molecular cloning and sequence analysis of rps19 show that the nuclear gene encodes a long N-terminal extension. Import studies of the precursor protein indicate that only a small part of this extension is cleaved off during import. The larger part of the extension, which shows high similarity to conserved RNA-binding domains of the RNP-CS type, became part of the S19 protein. In the Escherichia coli ribosome S19 forms an RNA-binding complex as heterodimer with S13. By using immuno-analysis and import studies we show that a eubacterial-like S13 protein is absent from Arabidopsis mitochondria, and is not substituted by either a chloroplastic or a cytosolic homologue of this ribosomal protein. We therefore propose that either a highly diverged or missing RPS13 has been functionally replaced by an RNP domain that most likely derived from a glycine-rich RNA-binding protein. These results represent the first case of a functional replacement of a ribosomal protein by a common RNA-binding domain and offer a new view on the flexibility of biological systems in using well-adapted functional domains for different jobs. 相似文献
155.
Román Gómez Gonz ález Cosío 《International Planning Studies》1998,3(3):367-389
The concept of capacity building for environmental protection and management refers to the process by which the abilities of societies to identify and solve environmental problems are developed. This work assumes a social constructivist perspective to the process of capacity building for environmental governance and thus depicts it as critically dependent on broader processes of political and socioeconomic modernization. In an attempt to depict such a process, a heuristic device is put forward as a model of capacity analysis. A theoretical discourse and new institutionalist perspectives are used to test such a model on a theoretical plane. Some preliminary conclusions are drawn from this theoretical exercise. 相似文献
156.
1. 45 myopes (-3.0 to -6.0 D) were examined before and 1 and 6 months after photorefractive keratectomy (PRK). Visual acuity (VA) was tested using Snellen and logMAR charts. Contrast sensitivity (CS) was measured using a computerized system. 2. Preoperative best corrected VA (BCVA) in myopes was significantly lower in comparison with a control group using logMAR charts only. A reduction of BCVA by both methods at 1. month and its return after 6 months nearly to original values was noted. 3. Significantly lower values of CS were found in patients before PRK compared to the control group. After 1 and 6 months stayed the values on preoperative level. 相似文献
157.
158.
T Bakács Z Végh AH Merry RB Sim L Varga Z Kertész G Tusnády E Klein 《Canadian Metallurgical Quarterly》1993,35(3):219-228
The lysis of group AB erythrocytes by human complement was studied by different anti-A and anti-B IgM monoclonal antibodies (mabs) in a 51Cr-release assay. The concentration of membrane-bound immunoglobulin was detected by ELISA, and the amount of C1q and C3 bound to sensitized red cells was measured by using purified, 125I-labelled molecules. We have demonstrated that there is an exponential relationship between the concentration of the sensitizing IgM mabs and C1q binding to the sensitized AB cell. The efficiency of binding was related to the number of antibodies bound; thus, anti-A sensitized cells bound 3-6 times more C1q than anti-B sensitized cells did. AB cells, on the other hand, bound similar amounts of C3 whether anti-A or anti-B was present. The lytic efficiencies of the various IgM mabs during short incubation times were different, suggesting that the complement activation rates vary widely with different antibodies on the AB cell membrane. The binding of C1q to an antibody-sensitized target activates a cascade, whose components may migrate away from the sensitizing antibody; interactions between the activation processes generated by the anti-A and anti-B antibodies may thus occur. Choosing appropriate pairs of anti-A and anti-B mabs for the simultaneous sensitization of AB cells has indeed resulted in stimulation in some and inhibition in other combinations of mabs. It is suggested that stimulation is observed when the activated intermediates are produced in excess, whereas inhibition occurs when a shortage of activated intermediates prevents mutual utilization. 相似文献
159.
160.