全文获取类型
收费全文 | 29405篇 |
免费 | 2387篇 |
国内免费 | 855篇 |
专业分类
电工技术 | 908篇 |
技术理论 | 1篇 |
综合类 | 890篇 |
化学工业 | 7565篇 |
金属工艺 | 1147篇 |
机械仪表 | 1168篇 |
建筑科学 | 1514篇 |
矿业工程 | 312篇 |
能源动力 | 822篇 |
轻工业 | 4814篇 |
水利工程 | 448篇 |
石油天然气 | 629篇 |
武器工业 | 106篇 |
无线电 | 2177篇 |
一般工业技术 | 3907篇 |
冶金工业 | 2431篇 |
原子能技术 | 205篇 |
自动化技术 | 3603篇 |
出版年
2024年 | 143篇 |
2023年 | 498篇 |
2022年 | 1613篇 |
2021年 | 1915篇 |
2020年 | 1047篇 |
2019年 | 911篇 |
2018年 | 1005篇 |
2017年 | 1135篇 |
2016年 | 1103篇 |
2015年 | 1148篇 |
2014年 | 1495篇 |
2013年 | 1908篇 |
2012年 | 1965篇 |
2011年 | 2160篇 |
2010年 | 1718篇 |
2009年 | 1639篇 |
2008年 | 1501篇 |
2007年 | 1391篇 |
2006年 | 1182篇 |
2005年 | 932篇 |
2004年 | 708篇 |
2003年 | 602篇 |
2002年 | 576篇 |
2001年 | 447篇 |
2000年 | 342篇 |
1999年 | 376篇 |
1998年 | 619篇 |
1997年 | 491篇 |
1996年 | 363篇 |
1995年 | 240篇 |
1994年 | 194篇 |
1993年 | 184篇 |
1992年 | 121篇 |
1991年 | 83篇 |
1990年 | 92篇 |
1989年 | 73篇 |
1988年 | 64篇 |
1987年 | 65篇 |
1986年 | 65篇 |
1985年 | 66篇 |
1984年 | 53篇 |
1983年 | 41篇 |
1982年 | 34篇 |
1981年 | 57篇 |
1980年 | 42篇 |
1979年 | 34篇 |
1978年 | 33篇 |
1977年 | 41篇 |
1976年 | 39篇 |
1975年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
Raquel Alves dos Santos Teresinha Rosa Cabral Isabel Rosa Cabral Lusania Maria Greggi Antunes Cristiane Pontes Andrade Plínio Cerqueira dos Santos Cardoso Marcelo de Oliveira Bahia Claudia Pessoa José Luis Martins do Nascimento Rommel Rodríguez Burbano Catarina Satie Takahashi 《Biocell》2008,32(2):195-200
Physalis angulata L (Solanaceae) is a medicinal plant from North of Brazil, whose different extracts and infusions are commonly used in the popular medicine for the treatment of malaria, asthma, hepatitis, dermatitis and rheumatism. However, the genotoxic effects of P. angulata on human cells is not well known. The main purpose of the present study was to evaluate the in vitro genotoxic effects of aqueous extract of P. angulata using the comet assay and the micronucleus assay in human lymphocytes provided from 6 healthy donors. Treatments with P. angulata extracts were performed in vitro in order to access the extent of DNA damage. The comet assay has shown that treatments with P. angulata at 0.5, 1.0, 2.0, 3.0 and 6.0 microg/mL in culture medium were genotoxic. Lymphocytes treated with P. angulata at the concentrations of 3.0 and 6.0 microg/mL in culture medium showed a statistically significant increase in the frequency of micronucleus (p<0.05), however, the cytokinesis blocked proliferation index (CBPI) was not decreased after P. angulata treatment. In conclusion, the present work demonstrated the genotoxic effects of P. angulata extract on human lymphocytes in vitro. 相似文献
83.
People have knowledge about relationships (i.e., relational schemas) that is based on their experiences. Because most people have experience with complementary behavior (interaction partners behaving similarly in terms of affiliation but oppositely in terms of control), they expect complementary behavior in their relationships. Like other beliefs about relationships, expectations of complementarity affect self-construal. The authors provide evidence for complementary self-construal; people assimilate to relevant relationship partners on the affiliation dimension and contrast on the control dimension. Consistent with the proposed role of relationship knowledge in these effects, complementary self-construal was moderated by the familiarity of the target, whether people focused on their relationship with or the appearance of the target, and whether the context was relevant for the interpersonal dimension. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
85.
A new approach to study ergodicity of filtering processes is presented. It is based on the vanishing discount approach to discounted functional of filtering process. We show that limit superior of the Cesaro averages of the functionals is the same for all initial conditions from which the uniqueness of invariant measures of filtering processes follows. The approach is based on certain assumption for which we provide a sufficient condition using concavity arguments. In addition we show the existence of solutions to the Poisson equation corresponding to filtering process with concave functional. The assumptions are then extended to the controlled case and using similar concave arguments we obtain the existence of solutions to the Bellman equation corresponding to partially observed average cost per unit time problem. 相似文献
86.
Camelia Betianu Florentina A Caliman Maria Gavrilescu Igor Cretescu Corneliu Cojocaru Ioannis Poulios 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(11):1454-1465
BACKGROUND: Heterogeneous photocatalysis is influenced by a number of parameters involving synergistic effects; hence, an experimental strategy design that considers interactions between the main variables is needed. The response surface methodology was applied for the investigation of photodegradation of 20 mg L?1 Orange II in aqueous solutions and for optimization of color removal efficiency. Preliminary studies were performed to identify the parameters to be selected for optimization. RESULTS: The input variables considered for experimental design were: solution initial pH, oxidizing agent (H2O2) initial concentration and UV‐A irradiation time. The multivariate experimental design allowed the development of a quadratic response surface model to be used for the prediction of color removal efficiency over the full range of the experimental region. Under the optimum conditions established in the region of experimentation (pH = 6.9, [H2O2]0 = 183 mg L?1 and t = 32 min), a 100% color removal efficiency was obtained in experiments. CONCLUSIONS: It was found that the variables considered have important effects on color removal efficiency. The results demonstrate that the use of experimental design strategy is indispensable for successful investigation and adequate modeling of the process because the interdependence of the reaction parameters cannot be neglected. Copyright © 2008 Society of Chemical Industry 相似文献
87.
88.
Gerardo Gabriel Acosta Miguel Angel Mayosky José Maria Catalfo 《Applied Intelligence》1994,4(1):53-66
This article proposes a scheme for the on-line adjustment of three mode controller settings based on experimental measurements of closed-loop performance. It uses a recently developed heuristic tuning procedure to identify estimated process parameters. This method may give rise to conflicting estimates. Fuzzy Set theory is applied to manage the situation in terms of a fuzzy conjunction to combine the various estimates. PID control was chosen because of its wide use in the industrial environment due to driving simplicity and robustness. The article shows design, development, and computer simulation aspects. 相似文献
89.
A Di Lieto G De Rosa G Albano F Gallo M Pontillo R Micalef A Colucci A Paladini 《Canadian Metallurgical Quarterly》1996,23(4):220-228
Clinical and pathological changes of the mammary gland have been studied in 64 women affected by symptomatic Benign Breast Disease (BBD) coexisting with endometriosis or uterine leiomyomata. These patients were rendered hypoestrogenic by subcutaneous administration of the LH-RH analogue Goserelin depot [D-ser (tBu)6 Aza-Gly10-GnRH (ICI118630)] performed every 28 days, for six months. They were evaluated clinically and ultrasonographically before and after treatment to find possible changes of BBD as well as of endometriosis or uterine leiomyomata. Mammary biopsies were performed before and after treatment in all the patients to study the changes of EGF-R expression. Results showed that clinical improvement is accompanied with a reduction of EGF-R expression. 相似文献
90.
关系数据库在专家系统中的应用 总被引:6,自引:0,他引:6
在传统的专家系统中,对推理机工作过程的控制是程序实现的。本文介绍了一个用数据库技术引导推理过程的专家系统-精神分裂症诊断专家系统(ESSD)的推理控制策略。在这个专家系统中,作者将有关推理过程的控制信息用关系数据库技术进行存储和管理,达到了将控制策略数据化的目的。将数据库技术引入到专家系统的推进控制机制中可以使控制策略比较容易调整,且而可以大大压缩程序篇幅,显著提高系统运行效率,为专家系统的结构设 相似文献