全文获取类型
收费全文 | 4757篇 |
免费 | 126篇 |
专业分类
电工技术 | 48篇 |
综合类 | 2篇 |
化学工业 | 612篇 |
金属工艺 | 34篇 |
机械仪表 | 53篇 |
建筑科学 | 203篇 |
矿业工程 | 3篇 |
能源动力 | 69篇 |
轻工业 | 419篇 |
水利工程 | 66篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 323篇 |
一般工业技术 | 579篇 |
冶金工业 | 1978篇 |
原子能技术 | 15篇 |
自动化技术 | 470篇 |
出版年
2023年 | 28篇 |
2022年 | 53篇 |
2021年 | 77篇 |
2020年 | 61篇 |
2019年 | 57篇 |
2018年 | 56篇 |
2017年 | 48篇 |
2016年 | 86篇 |
2015年 | 49篇 |
2014年 | 96篇 |
2013年 | 189篇 |
2012年 | 161篇 |
2011年 | 244篇 |
2010年 | 191篇 |
2009年 | 193篇 |
2008年 | 221篇 |
2007年 | 232篇 |
2006年 | 194篇 |
2005年 | 147篇 |
2004年 | 129篇 |
2003年 | 122篇 |
2002年 | 127篇 |
2001年 | 77篇 |
2000年 | 84篇 |
1999年 | 99篇 |
1998年 | 341篇 |
1997年 | 200篇 |
1996年 | 125篇 |
1995年 | 115篇 |
1994年 | 98篇 |
1993年 | 102篇 |
1992年 | 63篇 |
1991年 | 33篇 |
1990年 | 56篇 |
1989年 | 50篇 |
1988年 | 45篇 |
1987年 | 47篇 |
1986年 | 46篇 |
1985年 | 61篇 |
1984年 | 40篇 |
1983年 | 29篇 |
1982年 | 31篇 |
1981年 | 43篇 |
1980年 | 26篇 |
1979年 | 32篇 |
1978年 | 25篇 |
1977年 | 31篇 |
1976年 | 74篇 |
1975年 | 24篇 |
1974年 | 18篇 |
排序方式: 共有4883条查询结果,搜索用时 265 毫秒
91.
This study investigated use and management of blogs in academic health sciences libraries. Quantitative and qualitative data were collected with a questionnaire distributed to bloggers and administrators representing 22 libraries self-identified as using blogs to publish library newsletters. Perceived barriers to use of blogs included lack of patron awareness and technical issues. Blogs were viewed as easy to use by librarians and blogs are used to promote licensed resources. Blogs do not replace other interactions with librarians, but in the future, could be used to develop a community, provide tools for learning, and increase visibility of the library. 相似文献
92.
Common characteristics of crisis situations are ambiguous and unplanned for events. The need for improvised roles can therefore be an imperative factor for the success of an operation. The aim of this study is to deepen the understanding of the processes taking place during improvised work “as it happens”. A case study of a crisis management team at work is presented and provides an in-depth analysis of the information and communication flow of persons acting in improvised roles, including contextual factors influencing the task at hand. The analysis suggests that three main factors lay behind decreased performance by the team when some of its members were forced to take on roles for which they lacked professional training; lack of language skills, lack of domain knowledge and insufficient organizational structure of the tasks. Based on the observations from this case study, we suggest three ways of improving a team’s performance and hence resilience when forced to improvise due to lack of personnel in one or more required competence areas. These are training to take on the responsibility for tasks or roles outside ones professional area of specialization, developing formal routines for changes in roles and tasks and developing and using tools and routines for information sharing. 相似文献
93.
Stephen J. Walsh Amy L. McCleary Carlos F. Mena Yang Shao Julie P. Tuttle Augusto Gonzlez Rachel Atkinson 《Remote sensing of environment》2008,112(5):291-1941
In the Galapagos Islands of Ecuador, one of the greatest threats to the terrestrial ecosystem is the increasing number and areal extent of invasive species. Increased human presence on the islands has hastened the introduction of plant and animal species that threaten the native and endemic flora and fauna. Considerable research on invasive species in the Galapagos Islands has been conducted by the Charles Darwin Foundation. We complement that work through a spatially- and spectrally-explicit satellite assessment of an important invasive plant species (Psidium guajava — guava) on Isabela Island that integrates diverse remote sensing systems, data types, spatial and spectral resolutions, and analytical and image processing approaches. QuickBird and Hyperion satellite data are processed to characterize the areal extent and spatial structure of guava through the following approaches: (1) QuickBird data are classified through a traditional pixel-based approach (i.e., an unsupervised classification approach using the ISODATA algorithm), as well as an Object-Based Image Analysis (OBIA) approach; (2) multiple approaches for spectral “unmixing” of the Hyperion hyper-spectral data are assessed to construct spectral end-members from QuickBird data using linear and non-linear mixture modeling approaches; and (3) landscape pattern metrics are calculated and compared for the pixel-based, object-based, and spectral unmixing approaches. The spectral–spatial characteristics of guava are interpreted relative to management strategies for the control of guava and the restoration of natural ecosystems in the Galapagos National Park. 相似文献
94.
The timestamp problem captures a fundamental aspect of asynchronous distributed computing. It allows processes to label events
throughout the system with timestamps that provide information about the real-time ordering of those events. We consider the
space complexity of wait-free implementations of timestamps from shared read-write registers in a system of n processes. We prove an lower bound on the number of registers required. If the timestamps are elements of a nowhere dense set, for example the integers,
we prove a stronger, and tight, lower bound of n. However, if timestamps are not from a nowhere dense set, this bound can be beaten: we give an implementation that uses n − 1 (single-writer) registers. We also consider the special case of anonymous implementations, where processes are programmed
identically and do not have unique identifiers. In contrast to the general case, we prove anonymous timestamp implementations
require n registers. We also give an implementation to prove that this lower bound is tight. This is the first anonymous timestamp
implementation that uses a finite number of registers. 相似文献
95.
96.
Primary focal segmental glomerulosclerosis (FSGS) is a lesion associated with a poor prognosis and results in end-stage renal disease after 5 to 10 years. Based on past experience, many nephrologists have considered primary FSGS a lesion that is steroid resistant and therefore are reluctant to offer steroids as treatment. Recent data, however, have demonstrated that patients with primary FSGS have a response to steroid therapy that is considerably better than had been described. Thus, it may be that nephrologists have been more "steroid reluctant" than the lesion is steroid resistant. To better understand this issue we review the clinical course and response to therapy in patients with primary FSGS. 相似文献
97.
98.
AIM: To investigate which of the routinely collected claims data from the German "Legal sickness funds" on hospital utilisation may be used, in addition to that prescribed by the legislator. DESIGN: We used claims data to study a cohort of sickness fund beneficiaries who were insured during the complete year 1992 (n = 81,309). Six utilisation parameters, using the number of cases and in hospital days overall as well as diseases specific (i.e. readmission rates, in-hospital days per person with [at least] one hospital stay) were calculated. RESULTS: There are 88 persons with (at least) one hospital stay, 116 hospital cases and a total of 1306 in-hospital days per 1000 insured persons in the study cohort. The average hospital days per person (14.8 days) are ca. 30% higher than the average length of stay (11.2 days). Hospital utilisation increases with age. Hospital stays associated with ICD-239 (neoplasms of unknown origin) resulted in a higher than average number of hospital days in total although the mean length of stay is not above the average. This is due to a high readmission rate. Hospital stays associated with elective surgical procedures have a high prevalence rate but a low readmission ratio and short length of stay. CONCLUSION: The parameters related to insured persons, cases and specifically personal parameters of hospital utilisation allow a detailed analysis of hospital care; different utilisation and user patterns can be investigated and possible determinants of utilisation can be identified. After technical transformation, routine data of the sickness funds can be used to obtain information relevant for health care planners as well as for quality management. 相似文献
99.
An 11-month-old male infant with recurrent supraventricular tachycardia (SVT) was treated with oral verapamil. Shortly thereafter he developed marked changes in behavior including lethargy, intensely increased thirst and urination, and irritability when denied fluids. "Primary" polydipsia was diagnosed following an evaluation which showed no evidence of adrenal insufficiency, diabetes insipidus, diabetes mellitus, hypercalcemia, hyperosmolality, or renal disease. The symptoms resolved 1 week after verapamil was discontinued. 相似文献
100.
Joshua M. Little Jiayue Sun Ali Kamali Amy Chen Asher C. Leff Yang Li Leah K. Borden Thilini U. Dissanayake Deborah Essumang Benita O. Oseleononmen Dongxia Liu Taylor J. Woehl Po-Yen Chen 《Advanced functional materials》2023,33(30):2215222
Assembling 2D-material (2DM) nanosheets into micro- and macro-architectures with augmented functionalities requires effective strategies to overcome nanosheet restacking. Conventional assembly approaches involve external binders and/or functionalization, which inevitably sacrifice 2DM's nanoscale properties. Noble metal ions (NMI) are promising ionic crosslinkers, which can simultaneously assemble 2DM nanosheets and induce synergistic properties. Herein, a collection of NMI–2DM complexes are screened and categorized into two sub-groups. Based on the zeta potentials, two assembly approaches are developed to obtain 1) NMI-crosslinked 2DM hydrogels/aerogels for heterostructured catalysts and 2) NMI–2DM inks for templated synthesis. First, tetraammineplatinum(II) nitrate (TPtN) serves as an efficient ionic crosslinker to agglomerate various 2DM dispersions. By utilizing micro-textured assembly platforms, various TPtN–2DM hydrogels are fabricated in a scalable fashion. Afterward, these hydrogels are lyophilized and thermally reduced to synthesize Pt-decorated 2DM aerogels (Pt@2DM). The Pt@2DM heterostructures demonstrate high, substrate-dependent catalytic activities and promote different reaction pathways in the hydrogenation of 3-nitrostyrene. Second, PtCl4 can be incorporated into 2DM dispersions at high NMI molarities to prepare a series of PtCl4–2DM inks with high colloidal stability. By adopting the PtCl4–graphene oxide ink, various Pt micro-structures with replicated topographies are synthesized with accurate control of grain sizes and porosities. 相似文献