全文获取类型
收费全文 | 4797篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 50篇 |
综合类 | 2篇 |
化学工业 | 378篇 |
金属工艺 | 21篇 |
机械仪表 | 25篇 |
建筑科学 | 50篇 |
矿业工程 | 8篇 |
能源动力 | 25篇 |
轻工业 | 187篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 87篇 |
一般工业技术 | 222篇 |
冶金工业 | 3602篇 |
原子能技术 | 11篇 |
自动化技术 | 148篇 |
出版年
2022年 | 19篇 |
2021年 | 19篇 |
2019年 | 13篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 21篇 |
2014年 | 13篇 |
2013年 | 57篇 |
2012年 | 39篇 |
2011年 | 56篇 |
2010年 | 32篇 |
2009年 | 37篇 |
2008年 | 57篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 28篇 |
2004年 | 21篇 |
2003年 | 37篇 |
2002年 | 24篇 |
2001年 | 38篇 |
2000年 | 28篇 |
1999年 | 145篇 |
1998年 | 1211篇 |
1997年 | 638篇 |
1996年 | 450篇 |
1995年 | 225篇 |
1994年 | 220篇 |
1993年 | 197篇 |
1992年 | 66篇 |
1991年 | 50篇 |
1990年 | 54篇 |
1989年 | 60篇 |
1988年 | 61篇 |
1987年 | 48篇 |
1986年 | 49篇 |
1985年 | 55篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 34篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1977年 | 83篇 |
1976年 | 157篇 |
1974年 | 23篇 |
1973年 | 18篇 |
1972年 | 19篇 |
1971年 | 14篇 |
1967年 | 12篇 |
排序方式: 共有4825条查询结果,搜索用时 15 毫秒
71.
Daniel P. Otto Hermanus C. M. Vosloo Wilna Liebenberg Melgardt M. de Villiers 《应用聚合物科学杂志》2008,107(6):3950-3962
The concentration of the cosurfactant 1‐butanol (BuOH) determined the polymer weight and size for a series of poly(styrene‐co‐methyl methacrylate)s (P(St‐co‐MMA)) synthesized by the free‐radical (o/w) microemulsion technique. A factorial design established the levels of the experimental conditions for the polymerization i.e., concentration of the surfactant, sodium dodecyl sulfate (SDS); concentration of the cosurfactant, BuOH; temperature and ratio of the styrene (St) to methyl methacrylate (MMA). An increase in the weight‐average molecular weight (Mw) and number‐average molecular weight (Mn) was observed in the P(St‐co‐MMA) series with an increase in BuOH concentration from 1 to 5 wt %. These effects could arise from the micellar aggregation induced by interfacial BuOH. The unique micellar conditions could be exploited to synthesize copolymers of varying molecular weight and size. Additionally, the composition of the copolymers was virtually templates of the feed composition. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
72.
The temperature‐programmed O2 desorption (O2‐TPD), the N2‐ and Kr‐ sorption as well as the scanning‐electron microscope (SEM) are important analysis methods in catalysis chemistry. By the example of a corundum and of a calcium hexaaluminate substrate the methods are used and the potential regarding to the surface properties and the activity of the assigned catalysts thereby pointed. Which of the two catalyst systems for the Ag‐catalyzed epoxidation of 1,3‐butadiene to 3,4‐epoxy‐1‐butene is more favorable is tested in a tubular reactor. 相似文献
73.
José A. Souto Dr. Rosaria Benedetti Katharina Otto Marco Miceli Rosana Álvarez Prof. Dr. Lucia Altucci Prof. Dr. Angel R. de Lera Prof. Dr. 《ChemMedChem》2010,5(9):1530-1540
A series of N‐(4‐cyano‐3‐trifluoromethyl‐phenyl)‐2‐ethoxy‐6‐alkyl (and alkenyl) benzamides related to the anacardic acid derivative CTPB have been prepared from 2,6‐dihydroxybenzoic acid with a Suzuki coupling and addition of the anion of 4‐cyano‐3‐trifluoromethylphenylamine to a benzodioxinone as the key steps. In U937 cells, these analogues, in particular 7 c , 7 d , 7 f and 7 j , induced cell‐cycle arrest in the G1 phase, caused apoptosis in about 20 % of the cells, and increased the acetylation levels of H3. These activities correlate with the enzymatic activation of histone lysine acetyltransferases (KATs): CBP and PCAF. 相似文献
74.
Günther Huber Otto Machhammer Maren Lepple Claudia Weidlich Cord-Henrich Dustmann Akane Hartenbach 《化学,工程师,技术》2021,93(4):664-672
A photovoltaic system could supply a single-family house with electrical power, warm water, and room heat if the energy would be distributed over the year to suit the load profile. However, storage systems for this are not state of the art yet. A concrete example is used to estimate which parameters such a power storage system should have. A suitable electrochemical reaction system based on inorganic salt mixtures is proposed. The German Federal Ministry of Education and Research is currently funding the development of a world storage facility based on the same reaction system. 相似文献
75.
76.
Saul Arlosoroff Gerhard Tschannerl David Grey William Journey Andrew Karp Otto Langenegger 《国际水》2013,38(2):106-111
An estimated 1,800 million people need improved water supplies in the fifteen years to the end of the century, if developing countries are to reach the target of full coverage. The first half of the International Drinking Water Supply and Sanitation Decade (1981–1990) has seen increases in the percentages of the rural population with access to safe water supplies, but only in Asia has the pace been quick enough to envisage a target of essentiahy full coverage by the end of the century (ten years later than the original Decade goals). In Africa, present progress rates would leave half of the rural population still without safe water in the year 2000, while in Latin America, it may be ten years into the next century before full coverage is achieved unless progress improves dramatically. Accelerated progress is hampered by financial and technical resource constraints faced by many developing countries, and the problem is aggravated by the growing number of completed projects which are broken down and abandoned, or functioning much below capacity. Attempts to increase the pace of providing improved community water supplies have often been frustrated because the technology used has proved impossible to sustain in village conditions. To make a lasting impact on the urgent needs, community water supply (CWS) strategies must be based on sustainable and replicable programs, and must take account of the pace at which resource constraints can be overcome. Human resource development programs take time to produce results, and institutional changes can only be accomplished gradually. 相似文献
77.
According to the type of ancillary service provisioned, operation mode of a power plant may change to part load operation. In this contribution, part load operation is understood as delivering a lower power output than possible at given ambient temperature because of gas turbine power output control. If it is economically justified, a power plant may operate in the part load mode for longer time. Part load performance of a newly built 80 MW combined cycle in Slovakia was studied in order to assess the possibilities for fuel savings. Based on online monitoring data three possibilities were identified: condensate preheating by activation of the currently idle hot water section; change in steam condensing pressure regulation strategy; and the most important gas turbine inlet air preheating. It may seem to be in contradiction with the well proven concept of gas turbine inlet air cooling, which has however been developed for boosting the gas turbine cycles in full load operation. On the contrary, in a combined cycle in the part load operation mode, elevated inlet air temperature does not affect the part load operation of gas turbines but it causes more high pressure steam to be raised in HRSG, which leads to higher steam turbine power output. As a result, less fuel needs to be combusted in gas turbines in order to achieve the requested combined cycle’s power output. By simultaneous application of all three proposals, more than a 2% decrease in the power plant’s natural gas consumption can be achieved with only minor capital expenses needed. 相似文献
78.
Safren Steven A.; O'Cleirigh Conall; Tan Judy Y.; Raminani Sudha R.; Reilly Laura C.; Otto Michael W.; Mayer Kenneth H. 《Canadian Metallurgical Quarterly》2009,28(1):1
Objective: To evaluate cognitive-behavioral therapy to enhance medication adherence and reduce depression (CBT-AD) in individuals with HIV. Design: A two arm, randomized, controlled, cross-over trial comparing CBT-AD to enhanced treatment as usual only (ETAU). ETAU, which both groups received, included a single-session intervention for adherence and a letter to the patient's provider documenting her or his continued depression. The intervention group also received 10 to 12 sessions of CBT-AD. Main Outcome Measures: Adherence to antiretroviral therapy as assessed by Medication Event Monitoring Systems (MEMs) and depression as assessed by blinded structured evaluation. Results: At the acute outcome assessment (3-months), those who received CBT-AD evidenced significantly greater improvements in medication adherence and depression relative to the comparison group. Those who were originally assigned to the comparison group who chose to cross over to CBT-AD showed similar improvements in both depression and adherence outcomes. Treatment gains for those in the intervention group were generally maintained at 6- and 12-month follow-up assessments. By the end of the follow-up period, those originally assigned CBT-AD demonstrated improvements in plasma HIV RNA concentrations, though these differences did not emerge before the cross-over, and hence there were not between-groups differences. Conclusions: CBT-AD is a potentially efficacious approach for individuals with HIV struggling with depression and adherence. Replication and extension in larger efficacy trials are needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
79.
The perception of a visual target can be strongly influenced by flanking stimuli. In static displays, performance on the target improves when the distance to the flanking elements increases—presumably because feature pooling and integration vanishes with distance. Here, we studied feature integration with dynamic stimuli. We show that features of single elements presented within a continuous motion stream are integrated largely independent of spatial distance (and orientation). Hence, space-based models of feature integration cannot be extended to dynamic stimuli. We suggest that feature integration is guided by perceptual grouping operations that maintain the identity of perceptual objects over space and time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
Chiarello Christine; Welcome Suzanne E.; Halderman Laura K.; Towler Stephen; Julagay Janelle; Otto Ronald; Leonard Christiana M. 《Canadian Metallurgical Quarterly》2009,23(2):210
The authors report findings of a large-scale, multitask investigation of sex differences in both structural asymmetries and lateralization of word reading. Two hundred participants were tested in eight divided visual field lexical tasks, and each received a structural magnetic resonance imaging scan. The authors examined whether there was evidence for sex differences in overall measures of neuroanatomical and behavioral lateralization, in specific language tasks and brain regions, and in variation in asymmetry within and across tasks and brain regions. There was very little evidence for sex differences on any behavioral measure. The few indications of sex differences in the current report accounted for 2% or less of the individual variation in asymmetry and could not be replicated in independent subsamples. No sex differences were observed in the asymmetry of structures in Broca's and Wernicke's areas such as pars triangularis, pars opercularis, the planum temporale, planum parietale, or Heschl's gyrus. There were also no sex differences in the variability of neuroanatomical asymmetries within or between brain regions. However, a significant relationship between planum temporale and behavioral asymmetry was restricted to men. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献