全文获取类型
收费全文 | 1997篇 |
免费 | 48篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 35篇 |
综合类 | 2篇 |
化学工业 | 438篇 |
金属工艺 | 53篇 |
机械仪表 | 37篇 |
建筑科学 | 36篇 |
矿业工程 | 6篇 |
能源动力 | 34篇 |
轻工业 | 158篇 |
水利工程 | 10篇 |
石油天然气 | 6篇 |
无线电 | 144篇 |
一般工业技术 | 414篇 |
冶金工业 | 461篇 |
原子能技术 | 16篇 |
自动化技术 | 204篇 |
出版年
2023年 | 13篇 |
2022年 | 52篇 |
2021年 | 64篇 |
2020年 | 24篇 |
2019年 | 38篇 |
2018年 | 51篇 |
2017年 | 53篇 |
2016年 | 62篇 |
2015年 | 55篇 |
2014年 | 60篇 |
2013年 | 95篇 |
2012年 | 65篇 |
2011年 | 83篇 |
2010年 | 82篇 |
2009年 | 75篇 |
2008年 | 73篇 |
2007年 | 36篇 |
2006年 | 51篇 |
2005年 | 28篇 |
2004年 | 43篇 |
2003年 | 44篇 |
2002年 | 31篇 |
2001年 | 23篇 |
2000年 | 28篇 |
1999年 | 20篇 |
1998年 | 107篇 |
1997年 | 93篇 |
1996年 | 57篇 |
1995年 | 48篇 |
1994年 | 35篇 |
1993年 | 39篇 |
1992年 | 29篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 40篇 |
1976年 | 69篇 |
1975年 | 8篇 |
1969年 | 7篇 |
排序方式: 共有2054条查询结果,搜索用时 15 毫秒
21.
22.
23.
In metastatic breast cancer the goal to reach must be the best possible palliation with minimum discomfort for the patient. We reviewed our experience with radiotherapy (20 or 30 Gy), systemic therapy and brace. Among 2200 breast cancer patients, we extracted 28 potential candidates for resection. All of them developed new metastases outside the treated field within one year. Local control was achieved in 68%, and 80% of them had stable or better performance status at 3 months. From our analysis, even patients with a so called "solitary lesion" do not seem to have a better prognosis than others. We conclude that radiotherapy (with systemic therapy and a brace) is still first-choice treatment for vertebral metastases; CT-guided percutaneous biopsy can avoid worthless major operations. The role of surgery should be limited to neurological compression, severe mechanical instability and to salvage the failures of conservative treatment. 相似文献
24.
II Wistuba C Behrens S Milchgrub AK Virmani J Jagirdar B Thomas HL Ioachim LA Litzky EM Brambilla JD Minna AF Gazdar 《Canadian Metallurgical Quarterly》1998,279(19):1554-1559
CONTEXT: Human immunodeficiency virus (HIV) infection has been associated with an increasing incidence of malignancy, and HIV-infected persons have an increased incidence of primary lung carcinoma compared with the general population. OBJECTIVE: To investigate the molecular changes present in HIV-associated lung tumors and compare them with those present in lung carcinomas arising in HIV-indeterminate subjects ("sporadic tumors"). DESIGN: Convenience sample. SUBJECTS: Archival tissues from 11 HIV-positive persons and from 35 persons of indeterminate HIV status. SETTING: University-based medical centers and affiliated hospitals. MAIN OUTCOME MEASURES: Analysis of frequency of loss of heterozygosity (LOH) and microsatellite alteration (MA) using polymerase chain reaction and 16 polymorphic microsatellite markers at 8 chromosomal regions frequently deleted in lung cancer. Presence of HIV and human papillomavirus (HPV) sequences. RESULTS: The overall frequency of LOH at all chromosomal regions tested and the frequencies at most of the individual regions were similar in the 2 groups. Frequency of MA present in the HIV-associated tumors (0.18) was 6-fold higher than in sporadic tumors (0.03) (P<.001). At least 1 MA was present in 10 (91%) of 11 HIV-associated tumors vs 17 (48%) of 35 sporadic tumors (P=.02). Molecular changes were independent of tumor stage and gender. HIV and HPV sequences were not detected in the HIV-associated lung carcinomas. CONCLUSIONS: Microsatellite alterations, which reflect widespread genomic instability, occur at greatly increased frequency in HIV-associated lung carcinomas. Although the mechanism underlying the development of increased MAs is unknown, it may play a crucial role in the development of many HIV-associated tumors. 相似文献
25.
26.
An Architecture for Human‐Guided Autonomy: Team TROOPER at the DARPA Robotics Challenge Finals 下载免费PDF全文
Steven Gray Robert Chevalier David Kotfis Benjamin Caimano Kenneth Chaney II Aron Rubin Kingsley Fregene Todd Danko 《野外机器人技术杂志》2017,34(5):852-873
Recent robotics efforts have automated simple, repetitive tasks to increase execution speed and lessen an operator's cognitive load, allowing them to focus on higher‐level objectives. However, an autonomous system will eventually encounter something unexpected, and if this exceeds the tolerance of automated solutions, there must be a way to fall back to teleoperation. Our solution is a largely autonomous system with the ability to determine when it is necessary to ask a human operator for guidance. We call this approach human‐guided autonomy. Our design emphasizes human‐on‐the‐loop control where an operator expresses a desired high‐level goal for which the reasoning component assembles an appropriate chain of subtasks. We introduce our work in the context of the DARPA Robotics Challenge (DRC) Finals. We describe the software architecture Team TROOPER developed and used to control an Atlas humanoid robot. We employ perception, planning, and control automation for execution of subtasks. If subtasks fail, or if changing environmental conditions invalidate the planned subtasks, the system automatically generates a new task chain. The operator is able to intervene at any stage of execution, to provide input and adjustment to any control layer, enabling operator involvement to increase as confidence in automation decreases. We present our performance at the DRC Finals and a discussion about lessons learned. 相似文献
27.
Generating quadrilateral meshes is a highly non-trivial task, as design decisions are frequently driven by specific application demands. Automatic techniques can optimize objective quality metrics, such as mesh regularity, orthogonality, alignment and adaptivity; however, they cannot make subjective design decisions. There are a few quad meshing approaches that offer some mechanisms to include the user in the mesh generation process; however, these techniques either require a large amount of user interaction or do not provide necessary or easy to use inputs. Here, we propose a template-based approach for generating quad-only meshes from triangle surfaces. Our approach offers a flexible mechanism to allow external input, through the definition of alignment features that are respected during the mesh generation process. While allowing user inputs to support subjective design decisions, our approach also takes into account objective quality metrics to produce semi-regular, quad-only meshes that align well to desired surface features. 相似文献
28.
Mario A. S. Lizi��r Marcelo F. Siqueira Joel Daniels II Claudio T. Silva L. Gustavo Nonato 《The Visual computer》2011,27(10):887-903
This paper describes a novel template-based meshing approach for generating good quality quadrilateral meshes from 2D digital
images. This approach builds upon an existing image-based mesh generation technique called Imeshp, which enables us to create a segmented triangle mesh from an image without the need for an image segmentation step. Our
approach generates a quadrilateral mesh using an indirect scheme, which converts the segmented triangle mesh created by the
initial steps of the Imesh technique into a quadrilateral one. The triangle-to-quadrilateral conversion makes use of template meshes of triangles. To
ensure good element quality, the conversion step is followed by a smoothing step, which is based on a new optimization-based
procedure. We show several examples of meshes generated by our approach, and present a thorough experimental evaluation of
the quality of the meshes given as examples. 相似文献
29.
A method which enables the Squid dc voltmeter to be operated with a sample exposed to a significant external magnetic field is presented. A special superconducting shield with a finite time constant has been used to suppress time-dependent components of the field. With the shield, the Squid voltmeter has been able to work in magnetic fields up to 0.7 T in the flux-locked loop mode. The total voltage noise per unit bandwidth Vrms (referred to input) does not exceed the value of
. To extend the range of performance to higher magnetic fields, simple low pass filters have been built into the input circuit to increase its time constant. With the signal coil of the Squid shunted by a resistor RB = 3 × 10−6ω, the Squid voltmeter could be operated in fields up to 3.2 T with
相似文献
Full-size image (<1K)
30.
Jiří BarnatAuthor Vitae Petr BauchAuthor VitaeLuboš BrimAuthor Vitae Milan Češka 《Journal of Parallel and Distributed Computing》2012
Recent technological developments made various many-core hardware platforms widely accessible. These massively parallel architectures have been used to significantly accelerate many computation demanding tasks. In this paper, we show how the algorithms for LTL model checking can be redesigned in order to accelerate LTL model checking on many-core GPU platforms. Our detailed experimental evaluation demonstrates that using the NVIDIA CUDA technology results in a significant speedup of the verification process. Together with state space generation based on shared hash-table and DFS exploration, our CUDA accelerated model checker is the fastest among state-of-the-art shared memory model checking tools. 相似文献