全文获取类型
收费全文 | 7724篇 |
免费 | 398篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 158篇 |
综合类 | 20篇 |
化学工业 | 1466篇 |
金属工艺 | 218篇 |
机械仪表 | 407篇 |
建筑科学 | 170篇 |
矿业工程 | 5篇 |
能源动力 | 297篇 |
轻工业 | 602篇 |
水利工程 | 42篇 |
石油天然气 | 21篇 |
无线电 | 1459篇 |
一般工业技术 | 1357篇 |
冶金工业 | 720篇 |
原子能技术 | 89篇 |
自动化技术 | 1105篇 |
出版年
2023年 | 58篇 |
2022年 | 34篇 |
2021年 | 127篇 |
2020年 | 110篇 |
2019年 | 129篇 |
2018年 | 167篇 |
2017年 | 146篇 |
2016年 | 215篇 |
2015年 | 187篇 |
2014年 | 312篇 |
2013年 | 545篇 |
2012年 | 444篇 |
2011年 | 481篇 |
2010年 | 352篇 |
2009年 | 426篇 |
2008年 | 364篇 |
2007年 | 334篇 |
2006年 | 335篇 |
2005年 | 288篇 |
2004年 | 277篇 |
2003年 | 252篇 |
2002年 | 277篇 |
2001年 | 206篇 |
2000年 | 186篇 |
1999年 | 177篇 |
1998年 | 375篇 |
1997年 | 221篇 |
1996年 | 162篇 |
1995年 | 133篇 |
1994年 | 114篇 |
1993年 | 114篇 |
1992年 | 58篇 |
1991年 | 70篇 |
1990年 | 55篇 |
1989年 | 57篇 |
1988年 | 40篇 |
1987年 | 42篇 |
1986年 | 39篇 |
1985年 | 30篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 23篇 |
1980年 | 15篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 21篇 |
1974年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有8136条查询结果,搜索用时 46 毫秒
91.
Localization of putative tumor suppressor loci by genome-wide allelotyping in human pancreatic endocrine tumors 总被引:1,自引:0,他引:1
DC Chung SB Brown F Graeme-Cook LG Tillotson AL Warshaw RT Jensen A Arnold 《Canadian Metallurgical Quarterly》1998,58(16):3706-3711
Only two tumor suppressor gene loci, one on 3p25 and the MEN1 gene on 11q13, have thus far been implicated in the pathogenesis of sporadic human pancreatic endocrine tumors (PETs). A genome-wide allelotyping study of 28 human PETs was undertaken to identify other potential tumor suppressor gene loci. In addition to those on chromosomes 3p and 11q, frequent allelic deletions were identified on 3q (32%), 11p (36%), 16p (36%), and 22q (29%). Finer deletion mapping studies localized the smallest regions of common deletion to 3q27, 11p13, and 16p12.3-13.11. Potential candidate genes at these loci include WT1 (11p13), TSC2 (16p13), and NF2 (22q12), but no known tumor suppressor gene localizes to 3q27. The mean fractional allelic loss among these human PETs is 0.126, and no correlation was observed between allelic loss and clinical parameters, including age, sex, hormonal subtype, and disease stage. These findings highlight novel locations of tumor suppressor gene loci that contribute to the pathogenesis of human PETs, and several of these on 3p, 3q, and 22q are syntenic with loci on mouse chromosomes 9 and 16 that are implicated in a murine transgenic model of PETs. 相似文献
92.
AIM: To examine the association of Epstein-Barr virus (EBV) with carcinoma of the ear. METHODS: Five non-keratinising squamous cell carcinomas and two undifferentiated carcinomas of the ear were examined. In situ hybridisation was used to localised EBV-encoded RNAs (EBER). Immunohistochemical methods to detect LMP-1 and EBNA2 were performed in the EBER positive cases. RESULTS: Two cases were EBER positive, including one non-keratinising and one undifferentiated carcinoma. Both showed identical morphology to those arising from the nasopharynx, with abundant lymphoid stroma. They were both negative for LMP-1 and EBNA2. CONCLUSIONS: EBV associated carcinoma with the morphology of lymphoepithelioma can also arise from the middle ear. 相似文献
93.
This article studies the causes and treatment of benign nonpeptic esophageal strictures. The authors also discuss various therapeutic techniques for esophageal strictures, including esophageal dilatation with various dilators and balloons. Although the goals of stricture therapy are to relieve dysphagia and prevent stricture reoccurrence, only the first of these goals (effective dilatation with bougienage or balloon dilatation) has been achieved. The prevention of stricture reoccurrence remains to be achieved. 相似文献
94.
A G protein gamma subunit-like domain shared between RGS11 and other RGS proteins specifies binding to Gbeta5 subunits 总被引:1,自引:0,他引:1
BE Snow AM Krumins GM Brothers SF Lee MA Wall S Chung J Mangion S Arya AG Gilman DP Siderovski 《Canadian Metallurgical Quarterly》1998,95(22):13307-13312
Regulators of G protein signaling (RGS) proteins act as GTPase-activating proteins (GAPs) toward the alpha subunits of heterotrimeric, signal-transducing G proteins. RGS11 contains a G protein gamma subunit-like (GGL) domain between its Dishevelled/Egl-10/Pleckstrin and RGS domains. GGL domains are also found in RGS6, RGS7, RGS9, and the Caenorhabditis elegans protein EGL-10. Coexpression of RGS11 with different Gbeta subunits reveals specific interaction between RGS11 and Gbeta5. The expression of mRNA for RGS11 and Gbeta5 in human tissues overlaps. The Gbeta5/RGS11 heterodimer acts as a GAP on Galphao, apparently selectively. RGS proteins that contain GGL domains appear to act as GAPs for Galpha proteins and form complexes with specific Gbeta subunits, adding to the combinatorial complexity of G protein-mediated signaling pathways. 相似文献
95.
Tannic acid, propyl gallate and methyl gallate, but not gallic acid, were found to be inhibitory to the growth of intestinal bacteria Bacteroides fragilis ATCC 25285, Clostridium clostridiiforme ATCC 25537, C. perfringens ATCC 13124, C. paraputrificum ATCC 25780, Escherichia coli ATCC 25922, Enterobacter cloacae ATCC 13047, Salmonella typhimurium TA98 and S. typhimurium YG1041 at 100-1000 microg/ml in culture broth. Neither Bifidobacterium infantis ATCC 15697 nor Lactobacillus acidophilus ATCC 4356 was inhibited by any of the above compounds up to 500 microg/ml. Tannic acid has a much greater relative binding efficiency to iron than propyl gallate, methyl gallate or gallic acid. The inhibitory effect of tannic acid to the growth of intestinal bacteria may be due to the strong iron binding capacity of tannic acid; whereas the effect of propyl gallate and methyl gallate probably occurs by a different mechanism. The growth of E. coli was restored by the addition of iron to the medium after the precipitate caused by tannic acid was removed. Neither B. infantis nor L. acidophilus require iron for growth. This probably contributes to their resistance to tannic acid. Because tannins are abundant in the human diet, tannins may affect the growth of some intestinal bacteria and thus may have an impact on human health. 相似文献
96.
In the conventional sliding mode control, the relative degree of the chosen sliding surface is usually one. This paper addresses a general class of sliding surface whose relative degree is no longer restricted to one. We show that when the relative degree is more than two, it is inevitable that there will exist a limit cycle for the nonlinear sign function. And for the case of relative degree two the system possesses poor phase margin. However, these disadvantages can be remedied remarkably by smoothing out the control nonlinearity in a suitable boundary layer with a saturation function that ensures asymptotic stability of the overall system 相似文献
97.
WJ Cho EK Kim MJ Park SU Choi CO Lee SH Cheon BG Choi BH Chung 《Canadian Metallurgical Quarterly》1998,6(12):2449-2458
In this study a series of 3-arylisoquinoline derivatives were synthesized and cytotoxicity against human melanoma tumor cell evaluated, and a three dimensional quantitative structure-activity relationship was investigated using the comparative molecular field analysis (CoMFA). The results suggested that the electrostatic, steric and hydrophobic factors of 3-arylisoquinolines were strongly correlated with the antitumor activity. Considerable predictive ability (cross-validated r2 as high as 0.721) was obtained through CoMFA. 相似文献
98.
Hong-Chich Chou Chung-Ping Chung 《Parallel and Distributed Systems, IEEE Transactions on》1995,6(3):303-313
Performance in superscalar processing strongly depends on the compiler's ability to generate codes that can be executed by hardware in an optimal or near optimal order. Generating optimal code is an NP-complete problem. However, there is a need for highly optimized code, such as in superscalar or real-time systems. In this paper, an instruction scheduling scheme for optimizing a program trace is proposed. Optimized code can be arrived at without much redundant work, if some important features in code are well explored and utilized in scheduling. To formalize the task, two abstract models, one for a superscalar processor and the other for a program trace, are given. These two models reflect most of the characteristics of the scheduling problem. The interrelations between instructions and partial schedules are thoroughly studied, and dominance and equivalence relations on them are defined. These relations are then used to reduce the solution space and eventually help to produce optimal schedules. The results of experiments that show the promise of the proposed scheme are also presented 相似文献
99.
100.