全文获取类型
收费全文 | 7167篇 |
免费 | 660篇 |
国内免费 | 315篇 |
专业分类
电工技术 | 383篇 |
综合类 | 445篇 |
化学工业 | 1111篇 |
金属工艺 | 497篇 |
机械仪表 | 497篇 |
建筑科学 | 576篇 |
矿业工程 | 132篇 |
能源动力 | 183篇 |
轻工业 | 504篇 |
水利工程 | 104篇 |
石油天然气 | 299篇 |
武器工业 | 76篇 |
无线电 | 959篇 |
一般工业技术 | 981篇 |
冶金工业 | 431篇 |
原子能技术 | 75篇 |
自动化技术 | 889篇 |
出版年
2024年 | 33篇 |
2023年 | 133篇 |
2022年 | 264篇 |
2021年 | 383篇 |
2020年 | 293篇 |
2019年 | 230篇 |
2018年 | 222篇 |
2017年 | 249篇 |
2016年 | 222篇 |
2015年 | 260篇 |
2014年 | 307篇 |
2013年 | 374篇 |
2012年 | 418篇 |
2011年 | 415篇 |
2010年 | 411篇 |
2009年 | 383篇 |
2008年 | 388篇 |
2007年 | 378篇 |
2006年 | 382篇 |
2005年 | 301篇 |
2004年 | 195篇 |
2003年 | 179篇 |
2002年 | 185篇 |
2001年 | 144篇 |
2000年 | 181篇 |
1999年 | 175篇 |
1998年 | 153篇 |
1997年 | 160篇 |
1996年 | 117篇 |
1995年 | 107篇 |
1994年 | 91篇 |
1993年 | 100篇 |
1992年 | 71篇 |
1991年 | 56篇 |
1990年 | 44篇 |
1989年 | 34篇 |
1988年 | 31篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 8篇 |
1951年 | 1篇 |
排序方式: 共有8142条查询结果,搜索用时 14 毫秒
11.
12.
Shock increases mortality from brain injuries, but the mechanism is poorly understood. We hypothesized that brain injury followed by shock and resuscitation leads to a secondary reperfusion injury mediated in part by polymorphonuclear leukocytes (PMNs). To validate this hypothesis, we studied cerebral perfusion pressure (CPP), intracranial pressure (ICP), cerebral blood flow (CBF), cortical water content (CWC), and hemodynamic variables in a porcine model of focal cryogenic brain injury and hemorrhagic shock. Cerebral PMN accumulation (CPMN) in the injured and uninjured hemispheres was determined histologically from the total PMNs in five high-power fields (400x). Twenty-nine mature swine were randomized to four groups. Group 1, the control group, was instrumented only. Group 2 animals had a brain injury alone and were studied for 24 hours. Group 3 animals had a brain injury and hemorrhagic shock. Group 4 animals had hemorrhagic shock alone. Brain injury followed by shock caused a significantly greater ICP and a significantly lower CBF than brain injury or shock alone. There was no significant difference in CPP between groups after resuscitation. The CWC of the lesioned area was similar in both brain-injured groups but was significantly increased when compared with the controls and the shock-only group. The CWC of the nonlesioned hemisphere was higher in group 3 than in group 2. The CPMN in both hemispheres in group 3 was significantly greater than in either group 2 or group 4. There was a significant positive correlation between CPMN and both ICP and CWC, and a significant negative correlation between CPMN and CBF. These data suggest an association between CPMN accumulation and secondary brain injury. 相似文献
13.
14.
Aerodynamic loads on a multi-bladed helicopter rotor in hovering flight were calculated by solving the three-dimensional incompressible Navier-Stokes equations. The rotor wake effects were accounted by the correction of local geometric angle of attack according to a free-wake modeling in addition to an empirical modification for the tip flow effect. The validity and efficiency of the present method were verified by the comparisons between numerical results and experimental data. 相似文献
15.
Huang Y. Palaniappan K. Zhuang X. Cavanaugh J.E. 《IEEE transactions on pattern analysis and machine intelligence》1995,17(12):1177-1190
Optic flow motion analysis represents an important family of visual information processing techniques in computer vision. Segmenting an optic flow field into coherent motion groups and estimating each underlying motion is a very challenging task when the optic flow field is projected from a scene of several independently moving objects. The problem is further complicated if the optic flow data are noisy and partially incorrect. In this paper, the authors present a novel framework for determining such optic flow fields by combining the conventional robust estimation with a modified genetic algorithm. The baseline model used in the development is a linear optic flow motion algorithm due to its computational simplicity. The statistical properties of the generalized linear regression (GLR) model are thoroughly explored and the sensitivity of the motion estimates toward data noise is quantitatively established. Conventional robust estimators are then incorporated into the linear regression model to suppress a small percentage of gross data errors or outliers. However, segmenting an optic flow field consisting of a large portion of incorrect data or multiple motion groups requires a very high robustness that is unattainable by the conventional robust estimators. To solve this problem, the authors propose a genetic partitioning algorithm that elegantly combines the robust estimation with the genetic algorithm by a bridging genetic operator called self-adaptation 相似文献
16.
F Fogt AO Vortmeyer M Stolte E Mueller J Mueller A Noffsinger C Poremba Z Zhuang 《Canadian Metallurgical Quarterly》1998,29(9):961-964
Carcinoma in ulcerative colitis (UC) develops from dysplastic precursor lesions, which include flat dysplasia (FD) and polypoid dysplasias (PD). PD may present as single or multiple polypoid structures or as plaque-like lesions that, independent of histological grade, are an indication for colectomy. PDs are histologically similar to adenomas and may not be readily distinguished by light microscopy. It is not known whether FD and PD are different entities, or whether they represent etiologically similar lesions with different morphological expression. We microdissected 25 cases of UC with PD and 19 samples of FD with surrounding chronic colitis (CC) in UC. Loss of heterozygosity (LOH) at the von Hippel Lindau (vHL) gene locus and the putative tumor suppressor genes APC, INK4A (9p16), and p53 was studied. LOH of the vHL gene, INK4A (9p16), and APC was also studied in 11 sporadic adenomas of the colon. LOH at the vHL locus was present in 50% of the samples of PD and in 12% of the samples of FD. LOH was seen in CC close to PD and FD in 26% and 12% of cases, respectively. No adenoma showed LOH of the vHL gene markers studied. LOH in p53 was seen in PD in 16% cases and in FD in 42% cases and in CC close to PD and FD in 0% and 14% cases, respectively. LOH patterns between PD and FD of the markers for APC and 9p16 were not different. LOH in APC was seen in two of five cases of adenoma. We conclude that PD and FD share genetic alterations in APC and 9p16 genes. More frequent involvement of the VHL gene in PD and surrounding CC and involvement of p53 in HGD and CC in FD may represent genetic differences between the development of PD and FD and may be the cause of the different morphology. The infrequency of LOH at the vHL locus in adenomas versus PD may serve as a discriminator between adenomas and PD in diagnostically problematic cases. 相似文献
17.
越来越多的企业正在或者即将用SAP作为ERP的应用载体。企业在得益于ERP精细化管理的同时,往往也为ERP与其他子系统整合集成所烦恼。介绍了几种应用于SAP的接口技术,其中包括RFC、ALE-IDOC、BAPI、SAP-DCOM以及Web Service接口技术。并且在此基础上,列举了企业内部的一个实例,展现了SAP通过接口技术与外部的PDA移动终端系统整合,从而解决了维修服务行业从接收工单、记录维修、备件管理等在移动环境下的应用需求。 相似文献
18.
Applied Intelligence - Pharmaceutical drug combinations can effectively treat various medical conditions. However, some combinations can cause serious adverse drug reactions (ADR). Therefore,... 相似文献
19.
随着计算机技术及多媒体技术的发展,多媒体在教学中的应用越来越广泛,多媒体有着传统教学媒体不具备的独特优势,但在实际教学中也有不足之处,在教学中必须根据实际情况灵活运用多媒体才能取得理想的教学效果。 相似文献
20.
Zhuang Xuezeng 《电子科学学刊(英文版)》1985,2(2):162-175
A technique of symmetry analysis for modal characteristics in uniform waveguides or resonators with ferrite rods is presented
here. Symmetry analysis can provide basic information concerning modal characteristics. After summarizing the basic principles
of symmetry analysis, some points concerning symmetry operations are discussed. Then the process of symmetry analysis is applied
to structures, i.e. uniform wave guides withC
n
symmetry or
symmetry and resonators withD
nh
symmetry in which exist longitudinally magnetized ferrite rods. Finally, results of the symmetry analysis are given in four
tables. 相似文献