全文获取类型
收费全文 | 4526篇 |
免费 | 190篇 |
国内免费 | 95篇 |
专业分类
电工技术 | 46篇 |
技术理论 | 1篇 |
综合类 | 1669篇 |
化学工业 | 125篇 |
金属工艺 | 63篇 |
机械仪表 | 100篇 |
建筑科学 | 998篇 |
矿业工程 | 45篇 |
能源动力 | 16篇 |
轻工业 | 81篇 |
水利工程 | 52篇 |
石油天然气 | 467篇 |
武器工业 | 6篇 |
无线电 | 136篇 |
一般工业技术 | 164篇 |
冶金工业 | 372篇 |
原子能技术 | 3篇 |
自动化技术 | 467篇 |
出版年
2024年 | 7篇 |
2023年 | 39篇 |
2022年 | 85篇 |
2021年 | 80篇 |
2020年 | 93篇 |
2019年 | 70篇 |
2018年 | 51篇 |
2017年 | 66篇 |
2016年 | 92篇 |
2015年 | 119篇 |
2014年 | 260篇 |
2013年 | 254篇 |
2012年 | 320篇 |
2011年 | 352篇 |
2010年 | 282篇 |
2009年 | 319篇 |
2008年 | 324篇 |
2007年 | 313篇 |
2006年 | 295篇 |
2005年 | 258篇 |
2004年 | 232篇 |
2003年 | 171篇 |
2002年 | 165篇 |
2001年 | 103篇 |
2000年 | 84篇 |
1999年 | 68篇 |
1998年 | 44篇 |
1997年 | 33篇 |
1996年 | 38篇 |
1995年 | 27篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1975年 | 3篇 |
1969年 | 4篇 |
1965年 | 5篇 |
1964年 | 7篇 |
1963年 | 5篇 |
1962年 | 2篇 |
1961年 | 3篇 |
1960年 | 2篇 |
1959年 | 6篇 |
1958年 | 3篇 |
1957年 | 9篇 |
1956年 | 6篇 |
1955年 | 4篇 |
1954年 | 6篇 |
排序方式: 共有4811条查询结果,搜索用时 15 毫秒
1.
Paola Leonor Quan Marina Sabat-Bresc Yanru Guo Margarita Martín Gabriel Gastaminza 《International journal of molecular sciences》2021,22(9)
Recent research on mast cell biology has turned its focus on MRGPRX2, a new member of the Mas-related G protein-coupled subfamily of receptors (Mrgprs), originally described in nociceptive neurons of the dorsal root ganglia. MRGPRX2, a member of this group, is present not only in neurons but also in mast cells (MCs), specifically, and potentially in other cells of the immune system, such as basophils and eosinophils. As emerging new functions for this receptor are studied, a variety of both natural and pharmacologic ligands are being uncovered, linked to the ability to induce receptor-mediated MC activation and degranulation. The diversity of these ligands, characterized in their human, mice, or rat homologues, seems to match that of the receptor’s interactions. Natural ligands include host defense peptides, basic molecules, and key neuropeptides such as substance P and vasointestinal peptide (known for their role in the transmission of pain and itch) as well as eosinophil granule-derived proteins. Exogenous ligands include MC secretagogues such as compound 48/80 and mastoparan, a component of bee wasp venom, and several peptidergic drugs, among which are members of the quinolone family, neuromuscular blocking agents, morphine, and vancomycin. These discoveries shed light on its capacity as a multifaceted participant in naturally occurring responses within immunity and neural stimulus perception, as in responses at the center of immune pathology. In host defense, the mice Mrgprb2 has been proven to aid mast cells in the detection of peptidic molecules from bacteria and in the release of peptides with antimicrobial activities and other immune mediators. There are several potential actions described for it in tissue homeostasis and repair. In the realm of pathologic response, there is evidence to suggest that this receptor is also involved in chronic inflammation. Furthermore, MRGPRX2 has been linked to the pathophysiology of non-IgE-mediated immediate hypersensitivity drug reactions. Different studies have shown its possible role in other allergic diseases as well, such as asthma, atopic dermatitis, contact dermatitis, and chronic spontaneous urticaria. In this review, we sought to cover its function in physiologic processes and responses, as well as in allergic and nonallergic immune disease. 相似文献
2.
3.
Georgios Tsaparlis 《Israel journal of chemistry》2019,59(6-7):478-492
Numerous conceptual difficulties and misconceptions have been reported in the science and chemistry education literature about electrochemistry concepts such as electrolytes, redox equations, and about electrochemical (galvanic and electrolytic) cells. Other studies have considered teaching approaches aimed at improving learning and at overcoming misconceptions. This paper reviews these studies and considers strategies and approaches for the effective teaching of electrochemistry. Then, the review focuses on problem solving in equilibrium electrochemistry, especially problems involving the Nernst equation. The main findings of four studies with Greek university chemistry students, dealing with: (i) algorithmic problem‐solving ability; (ii) practice on problem solving; (iii) the effect of the format of a problem; and (iv) the construction and evaluation of a website devoted to electrochemistry problem solving, are reported. 相似文献
4.
Lecture capture with real‐time rearrangement of visual elements: impact on student performance 下载免费PDF全文
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance. 相似文献
5.
李凯花 《石油化工管理干部学院学报》2003,(4):19-21
推进施工企业党组织的建设必须与时俱进,坚持一岗双责、两个融合、三个同步、四个同时,创新工作思路、工作机制、工作方法和工作方式。把贯彻落实“三个代表”重要思想,作为检验工作成效的根本标准。 相似文献
6.
Xueming Huang Gordon I. McCalla Jim E. Greer Eric Neufeld 《User Modeling and User-Adapted Interaction》1991,1(1):87-115
A user/student model must be revised when new information about the user/student is obtained. But a sophisticated user/student model is a complex structure that contains different types of knowledge. Different techniques may be needed for revising different types of knowledge. This paper presents a student model maintenance system (SMMS) which deals with revision of two important types of knowledge in student models: deductive knowledge and stereotypical knowledge. In the SMMS, deductive knowledge is represented by justified beliefs. Its revision is accomplished by a combination of techniques involving reason maintenance and formal diagnosis. Stereotypical knowledge is represented in the Default Package Network (DPN). The DPN is a knowledge partitioning hierarchy in which each node contains concepts in a sub-domain. Revision of stereotypical knowledge is realized by propagating new information through the DPN to change default packages (stereotypes) of the nodes in the DPN. A revision of deductive knowledge may trigger a revision of stereotypical knowledge, which results in a desirable student model in which the two types of knowledge exist harmoniously. 相似文献
7.
对称配筋小偏心受压构件的截面设计 总被引:4,自引:1,他引:3
对小偏心受压构件在对称配筋情况下的截面配筋计算,提出用最佳一次逼近多项式简化基本公式,直接按二次方程求解ξ的近似方法,具有精度高,相对误差小,计算方便等优点,可供工程设计人员参考。 相似文献
8.
9.
This study provides a meta-analysis of research on the associations between relationship conflict, task conflict, team performance, and team member satisfaction. Consistent with past theorizing, results revealed strong and negative correlations between relationship conflict, team performance, and team member satisfaction. In contrast to what has been suggested in both academic research and introductory textbooks, however, results also revealed strong and negative (instead of the predicted positive) correlations between task conflict, team performance, and team member satisfaction. As predicted, conflict had stronger negative relations with team performance in highly complex (decision making, project, mixed) than in less complex (production) tasks. Finally, task conflict was less negatively related to team performance when task conflict and relationship conflict were weakly, rather than strongly, correlated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
严陆光 《电气电子教学学报》2003,25(5):1-4
结合自身的学习、工作经历,与研究生畅谈如何学会“做人、做事、做学问”。 相似文献