全文获取类型
收费全文 | 5152篇 |
免费 | 258篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 70篇 |
综合类 | 18篇 |
化学工业 | 1064篇 |
金属工艺 | 108篇 |
机械仪表 | 98篇 |
建筑科学 | 253篇 |
矿业工程 | 9篇 |
能源动力 | 140篇 |
轻工业 | 452篇 |
水利工程 | 49篇 |
石油天然气 | 31篇 |
无线电 | 438篇 |
一般工业技术 | 808篇 |
冶金工业 | 1035篇 |
原子能技术 | 31篇 |
自动化技术 | 808篇 |
出版年
2023年 | 52篇 |
2022年 | 79篇 |
2021年 | 126篇 |
2020年 | 74篇 |
2019年 | 76篇 |
2018年 | 104篇 |
2017年 | 102篇 |
2016年 | 148篇 |
2015年 | 134篇 |
2014年 | 157篇 |
2013年 | 273篇 |
2012年 | 209篇 |
2011年 | 289篇 |
2010年 | 238篇 |
2009年 | 200篇 |
2008年 | 205篇 |
2007年 | 204篇 |
2006年 | 176篇 |
2005年 | 151篇 |
2004年 | 125篇 |
2003年 | 101篇 |
2002年 | 109篇 |
2001年 | 102篇 |
2000年 | 73篇 |
1999年 | 105篇 |
1998年 | 317篇 |
1997年 | 207篇 |
1996年 | 136篇 |
1995年 | 113篇 |
1994年 | 71篇 |
1993年 | 81篇 |
1992年 | 47篇 |
1991年 | 28篇 |
1990年 | 39篇 |
1989年 | 44篇 |
1988年 | 53篇 |
1987年 | 67篇 |
1986年 | 36篇 |
1985年 | 47篇 |
1984年 | 40篇 |
1983年 | 42篇 |
1982年 | 45篇 |
1981年 | 33篇 |
1980年 | 34篇 |
1979年 | 28篇 |
1978年 | 22篇 |
1977年 | 26篇 |
1976年 | 61篇 |
1974年 | 19篇 |
1973年 | 21篇 |
排序方式: 共有5412条查询结果,搜索用时 281 毫秒
111.
Quality of life development during initial hemodialysis therapy and association with loss of residual renal function 下载免费PDF全文
Christina G. Poulsen Krista D. Kjaergaard Christian D. Peters Bente Jespersen Jens D. Jensen 《Hemodialysis international. International Symposium on Home Hemodialysis》2017,21(3):409-421
Introduction: Health related quality of life (HRQOL) is markedly reduced in hemodialysis patients compared to the general population. We investigated the course of self‐reported HRQOL over time and the association with selected factors, focusing on changes in glomerular filtration rate (GFR). Methods: Eighty‐two newly started hemodialysis patients from the SAFIR cohort filled out the Kidney Disease Quality of Life Short Form Version 1.3 (KDQOL‐SFTM) questionnaire at baseline, 6 and 12 months. The SAFIR study was a randomized, placebo‐controlled, double‐blind intervention study, examining the effects of the angiotensin II receptor blocker irbesartan. HRQOL was a secondary outcome measure. Main inclusion criteria: Dialysis vintage <1 year, left ventricular ejection fraction >30% and urinary output >300 mL/day. GFR was measured with mean creatinine and urea clearance from 24‐hour urine collections at baseline, 6 and 12 months. Findings: Irbesartan treatment did not affect HRQOL. Patients were pooled into one group for further analyses. Decline in GFR correlated significantly with decreasing HRQOL over time. HRQOL was stable over time, with a slight nonsignificant tendency toward improved HRQOL. The largest HRQOL‐differences (positive values equal improved HRQOL) observed during the 12 month study period were (mean[95% confidence interval]): Burden of kidney disease:6.4[?2.2;15.0], Role limitations‐physical:12.7[?2.1;27.5], and Role limitations‐emotional:9.7[?5.2;24.6]. Comorbidity, especially diabetes, hospital admissions, female gender, and age were strongly associated with lower HRQOL in cross sectional analysis. Discussion: Preservation of residual renal function seems to be important for HRQOL. In newly started HD patients, HRQOL showed little change after 12 months. HRQOL was negatively affected by comorbidity, especially diabetes, hospital admissions, female gender, and age. 相似文献
112.
113.
114.
115.
Giuseppe Antonio Elia Krystan Marquardt Katrin Hoeppner Sebastien Fantini Rongying Lin Etienne Knipping Willi Peters Jean‐Francois Drillet Stefano Passerini Robert Hahn 《Advanced materials (Deerfield Beach, Fla.)》2016,28(35):7564-7579
A critical overview of the latest developments in the aluminum battery technologies is reported. The substitution of lithium with alternative metal anodes characterized by lower cost and higher abundance is nowadays one of the most widely explored paths to reduce the cost of electrochemical storage systems and enable long‐term sustainability. Aluminum based secondary batteries could be a viable alternative to the present Li‐ion technology because of their high volumetric capacity (8040 mAh cm?3 for Al vs 2046 mAh cm?3 for Li). Additionally, the low cost aluminum makes these batteries appealing for large‐scale electrical energy storage. Here, we describe the evolution of the various aluminum systems, starting from those based on aqueous electrolytes to, in more details, those based on non‐aqueous electrolytes. Particular attention has been dedicated to the latest development of electrolytic media characterized by low reactivity towards other cell components. The attention is then focused on electrode materials enabling the reversible aluminum intercalation‐deintercalation process. Finally, we touch on the topic of high‐capacity aluminum‐sulfur batteries, attempting to forecast their chances to reach the status of practical energy storage systems. 相似文献
116.
117.
Olivier Guillon Christian Elsässer Oliver Gutfleisch Jürgen Janek Sandra Korte-Kerzel Dierk Raabe Cynthia A. Volkert 《Materials Today》2018,21(5):527-536
The use of external electric and magnetic fields for the synthesis and processing of inorganic materials such as metals and ceramics has seen renewed interest in recent years. Electromagnetic energy can be utilized in different ways to improve or accelerate phase formation and stabilization, chemical ordering, densification and coarsening of particle-based materials (pore elimination and grain growth), and mechanical deformation (plasticity and creep). In these new synthesis and processing routes, the resulting microstructures and macroscopic material behavior are determined by the interaction of the applied fields with defects such as single or clustered point defects, dislocation networks, and interfaces. Multiscale experimental investigations and modeling are necessary to unveil the mechanisms underlying this field-assisted manipulation of matter. 相似文献
118.
We present a robust optimization framework that is applicable to general nonlinear programs (NLP) with uncertain parameters. We focus on design problems with partial differential equations (PDE), which involve high computational cost. Our framework addresses the uncertainty with a deterministic worst-case approach. Since the resulting min–max problem is computationally intractable, we propose an approximate robust formulation that employs quadratic models of the involved functions that can be handled efficiently with standard NLP solvers. We outline numerical methods to build the quadratic models, compute their derivatives, and deal with high-dimensional uncertainties. We apply the presented approach to the parametrized shape optimization of systems that are governed by different kinds of PDE and present numerical results. 相似文献
119.
Fernando Maccari Tarini Prasad Mishra Monica Keszler Tobias Braun Esmaeil Adabifiroozjaei Iliya Radulov Tianshu Jiang Enrico Bruder Olivier Guillon Leopoldo Molina-Luna Martin Bram Oliver Gutfleisch 《Advanced Engineering Materials》2023,25(18):2300252
Flash spark plasma sintering (flash SPS) is an attractive method to obtain Nd–Fe–B magnets with anisotropic magnetic properties when starting from melt-spun powders. Compared to the benchmark processing route via hot pressing with subsequent die upsetting, flash SPS promises electroplasticity as an additional deformation mechanism and reduced tool wear, while maximizing magnetic properties by tailoring the microstructure—fully dense and high texture. A detailed parameter study is conducted to understand the influence of Flash SPS parameters on the densification and magnetic properties of commercial MQU-F powder. It is revealed that the presintering conditions and preheating temperature before applying the power pulse play a major role for tailoring grain size and texture in the case of hot deformation via Flash SPS. Detailed microstructure and magnetic domain evaluation disclose the texture enhancement with increasing flash SPS temperature at the expense of coercivity. The best compromise between remanence and coercivity (1.37 T and 1195 kA m−1, respectively) is achieved through a combination of presintering at 500 °C for 120 s and preheating temperature of 600 °C, resulting in a magnet with energy product (BH)max of 350 kJm−3. These findings show the potential of flash SPS to obtain fully dense anisotropic nanocrystalline magnets with high magnetic performance. 相似文献
120.
C van Campen HJ Sixma JJ Kerssens L Peters JJ Rasker 《Canadian Metallurgical Quarterly》1998,37(4):362-368
BACKGROUND: Stress can exacerbate a number of psychiatric disorders, many of which are associated with prefrontal cortical (PFC) cognitive deficits. Biochemical studies demonstrate that mild stress preferentially increases dopamine turnover in the PFC. Our study examined the effects of acute, mild stress exposure on higher cognitive function in monkeys and the role of dopaminergic mechanisms in the stress response. METHODS: The effects of loud (105-dB) noise stress were examined on a spatial working memory task (delayed response) dependent on the PFC, and on a reference memory task with similar motor and motivational demands (visual pattern discrimination) dependent on the inferior temporal cortex. The role of dopamine mechanisms was tested by challenging the stress response with agents that decrease dopamine receptor stimulation. RESULTS: Exposure to noise stress significantly impaired delayed-response performance. Stress did not impair performance on "0-second" delay control trials and did not alter visual pattern discrimination performance, which is consistent with impaired PFC cognitive function rather than nonspecific changes in performance. Stress-induced deficits in delayed-response performance were ameliorated by pretreatment with drugs that block dopamine receptors (haloperidol, SCH 23390) or reduce stress-induced PFC dopamine turnover in rodents (clonidine, naloxone hydrochloride). CONCLUSIONS: These results indicate that stress impairs PFC cognitive function through a hyperdopaminergic mechanism. Stress may take the PFC "off-line" to allow more habitual responses mediated by posterior cortical and subcortical structures to regulate behavior. This mechanism may have survival value, but may often be maladaptive in human society, contributing to the vulnerability of the PFC in many neuropsychiatric disorders. 相似文献