全文获取类型
收费全文 | 2885篇 |
免费 | 84篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 40篇 |
综合类 | 5篇 |
化学工业 | 398篇 |
金属工艺 | 57篇 |
机械仪表 | 53篇 |
建筑科学 | 117篇 |
矿业工程 | 10篇 |
能源动力 | 104篇 |
轻工业 | 338篇 |
水利工程 | 17篇 |
石油天然气 | 19篇 |
无线电 | 237篇 |
一般工业技术 | 360篇 |
冶金工业 | 791篇 |
原子能技术 | 24篇 |
自动化技术 | 411篇 |
出版年
2022年 | 28篇 |
2021年 | 35篇 |
2020年 | 27篇 |
2019年 | 20篇 |
2018年 | 43篇 |
2017年 | 35篇 |
2016年 | 44篇 |
2015年 | 44篇 |
2014年 | 79篇 |
2013年 | 128篇 |
2012年 | 93篇 |
2011年 | 113篇 |
2010年 | 93篇 |
2009年 | 83篇 |
2008年 | 102篇 |
2007年 | 113篇 |
2006年 | 100篇 |
2005年 | 63篇 |
2004年 | 69篇 |
2003年 | 80篇 |
2002年 | 60篇 |
2001年 | 62篇 |
2000年 | 60篇 |
1999年 | 62篇 |
1998年 | 266篇 |
1997年 | 164篇 |
1996年 | 108篇 |
1995年 | 67篇 |
1994年 | 82篇 |
1993年 | 83篇 |
1992年 | 38篇 |
1991年 | 37篇 |
1990年 | 32篇 |
1989年 | 36篇 |
1988年 | 30篇 |
1987年 | 31篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 22篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 29篇 |
1976年 | 47篇 |
1974年 | 14篇 |
1973年 | 18篇 |
1972年 | 13篇 |
排序方式: 共有2981条查询结果,搜索用时 15 毫秒
31.
This report describes a simple, rapid, automated microassay for measuring in vitro changes of oxidative burst of phagocytes following challenge with metals for orthopedic devices. The production of reactive oxygen species (ROS) by polymorphonuclear leukocytes (PMNs) was measured using 2',7'-dichlorofluorescin-diacetate (DCFH-DA) as fluorescent probe. DCFH-DA enters the cells and is oxidized by ROS to fluorescent DCF. The DCF generated was directly proportional to ROS produced intracellularly: The fluorescence intensity was read and converted to an index of ROS production by cells. In our experimental system, granulocytes (PMNs) were isolated from normal human blood and seeded in microplates. To verify if metals could influence ROS production, chromium, cobalt, nickel, molybdenum, titanium, aluminum, and vanadium prepared as aqueous extracts in phosphate-buffered saline were tested onto PMNs using phorbolmyristate acetate (PMA) as positive control. Molybdenum, aluminum, and vanadium increased ROS generation by PMNs, while signals not different from unstimulated PMNs were recorded for chromium, cobalt, nickel, and titanium. The DCFH-DA microplate-based assay provides an in vitro tool for the detection of oxygen-reactive species generated by PMNs as a response to metals. 相似文献
32.
AI Robles ML Rodriguez-Puebla AB Glick C Trempus L Hansen P Sicinski RW Tennant RA Weinberg SH Yuspa CJ Conti 《Canadian Metallurgical Quarterly》1998,12(16):2469-2474
Cyclin D1 is part of a cell cycle control node consistently deregulated in most human cancers. However, studies with cyclin D1-null mice indicate that it is dispensable for normal mouse development as well as cell growth in culture. Here, we provide evidence that ras-mediated tumorigenesis depends on signaling pathways that act preferentially through cyclin D1. Cyclin D1 expression and the activity of its associated kinase are up-regulated in keratinocytes in response to oncogenic ras. Furthermore, cyclin D1 deficiency results in up to an 80% decrease in the development of squamous tumors generated through either grafting of retroviral ras-transduced keratinocytes, phorbol ester treatment of ras transgenic mice, or two-stage carcinogenesis. 相似文献
33.
We have presented numerically useful expressions for calculating the derivative of the parabolic cylinder function Dp'(z) for the argument z=xe-iπ/4 and order p=-1/2+iy, with x and y real. This case is needed for calculating the currents excited on a perfectly conducting parabolic cylinder by a TE plane wave and for calculating the scattered far-field pattern 相似文献
34.
A dilatometer for measuring autogenous deformation in hardening portland cement paste 总被引:1,自引:1,他引:0
Different techniques for measuring autogenous deformation in cement paste are discussed, and a newly developed dilatometer designed specially for measuring this deformation is described. A particular characteristic of the dilatometer is the encapsulation of the cement paste in corrugated moulds. This restricts moisture loss and ensures that the hardening cement paste suffers insignificant restraint. In addition, the encapsulation permits measurements to commence shortly after casting. 相似文献
35.
Johan P. Hansen Henning Stichtenoth 《Applicable Algebra in Engineering, Communication and Computing》1990,1(1):67-77
We construct a series of algebraic geometric codes using a class of curves which have many rational points. We obtain codes of lengthq
2 over
q
, whereq = 2q
0
2
andq
0 = 2
n
, such that dimension + minimal distance q
2
+ 1 – q
0
(q – 1). The codes are ideals in the group algebra
q
[S], whereS is a Sylow-2-subgroup of orderq
2 of the Suzuki-group of orderq
2
(q
2
+ 1)(q – 1). The curves used for construction have in relation to their genera the maximal number of
GF
q
-rational points. This maximal number is determined by the explicit formulas of Weil and is effectively smaller than the Hasse—Weil bound.Supported by Deutsche Forschungsgemeinschaft while visiting Essen University 相似文献
36.
Juan Pablo Hourcade Natasha E. Bullock-Rest Thomas E. Hansen 《Personal and Ubiquitous Computing》2012,16(2):157-168
In spite of great improvements in early diagnosis and interventions, most children diagnosed with autism spectrum disorders
(ASD) are unlikely to live independently when they reach adulthood. We have been conducting research on novel computer-based
interventions with the goal of promoting social skills. Working with 26 children with ASD, their teachers, and other stakeholders,
we have iteratively developed a set of activities based on applications that run on multitouch tablets. Our observations suggest
these activities increased pro-social behaviors such as collaboration and coordination, augmented appreciation for social
activities, and provided children with novel forms of expression. 相似文献
37.
38.
39.
Davide Barbagallo Angela Caponnetto Cristina Barbagallo Rosalia Battaglia Federica Mirabella Duilia Brex Michele Stella Giuseppe Broggi Roberto Altieri Francesco Certo Rosario Caltabiano Giuseppe Maria Vincenzo Barbagallo Carmelina Daniela Anfuso Gabriella Lupo Marco Ragusa Cinzia Di Pietro Thomas Birkballe Hansen Michele Purrello 《International journal of molecular sciences》2021,22(4)
Circular RNAs (circRNAs) are a large class of RNAs with regulatory functions within cells. We recently showed that circSMARCA5 is a tumor suppressor in glioblastoma multiforme (GBM) and acts as a decoy for Serine and Arginine Rich Splicing Factor 1 (SRSF1) through six predicted binding sites (BSs). Here we characterized RNA motifs functionally involved in the interaction between circSMARCA5 and SRSF1. Three different circSMARCA5 molecules (Mut1, Mut2, Mut3), each mutated in two predicted SRSF1 BSs at once, were obtained through PCR-based replacement of wild-type (WT) BS sequences and cloned in three independent pcDNA3 vectors. Mut1 significantly decreased its capability to interact with SRSF1 as compared to WT, based on the RNA immunoprecipitation assay. In silico analysis through the “Find Individual Motif Occurrences” (FIMO) algorithm showed GAUGAA as an experimentally validated SRSF1 binding motif significantly overrepresented within both predicted SRSF1 BSs mutated in Mut1 (q-value = 0.0011). U87MG and CAS-1, transfected with Mut1, significantly increased their migration with respect to controls transfected with WT, as revealed by the cell exclusion zone assay. Immortalized human brain microvascular endothelial cells (IM-HBMEC) exposed to conditioned medium (CM) harvested from U87MG and CAS-1 transfected with Mut1 significantly sprouted more than those treated with CM harvested from U87MG and CAS-1 transfected with WT, as shown by the tube formation assay. qRT-PCR showed that the intracellular pro- to anti-angiogenic Vascular Endothelial Growth Factor A (VEGFA) mRNA isoform ratio and the amount of total VEGFA mRNA secreted in CM significantly increased in Mut1-transfected CAS-1 as compared to controls transfected with WT. Our data suggest that GAUGAA is the RNA motif responsible for the interaction between circSMARCA5 and SRSF1 as well as for the circSMARCA5-mediated control of GBM cell migration and angiogenic potential. 相似文献
40.
Simulation of nitrogen dynamics and biomass production in winter wheat using the Danish simulation model DAISY 总被引:14,自引:0,他引:14
S. Hansen H. E. Jensen N. E. Nielsen H. Svendsen 《Nutrient Cycling in Agroecosystems》1991,27(2-3):245-259
A dynamic simulation model for the soil plant system is described. The model includes a number of main modules, viz., a hydrological model including a submodel for soil water dynamics, a soil temperature model, a soil nitrogen model including a submodel for soil organic matter dynamics, and a crop model including a submodel for nitrogen uptake. The soil part of the model has a one-dimensional vertical structure. The soil profile is divided into layers on the basis of physical and chemical soil characteristics. The simulation model was used to simulate soil nitrogen dynamics and biomass production in winter wheat grown at two locations at various levels of nitrogen fertilization. The simulated results were compared to experimental data including concentration of inorganic nitrogen in soil, crop yield, and nitrogen accumulated in the aboveground part of the crop. Based on this validation it is concluded that the overall performance of the model is satisfactory although some minor adjustments of the model may prove to be necessary. 相似文献