全文获取类型
收费全文 | 128篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
综合类 | 3篇 |
化学工业 | 22篇 |
金属工艺 | 2篇 |
机械仪表 | 2篇 |
建筑科学 | 6篇 |
能源动力 | 2篇 |
轻工业 | 6篇 |
水利工程 | 8篇 |
无线电 | 25篇 |
一般工业技术 | 6篇 |
冶金工业 | 33篇 |
原子能技术 | 1篇 |
自动化技术 | 12篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 5篇 |
2009年 | 2篇 |
2007年 | 1篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 2篇 |
1965年 | 1篇 |
1929年 | 1篇 |
排序方式: 共有129条查询结果,搜索用时 15 毫秒
41.
As companding elements, field-effect transistors have advantages over p?n diodes; they have suitably shaped i/v characteristics which are controllable by gate bias. Tests show that a departure from linearity of compressor and expander in cascade can be corrected to have an error of less than 1%. 相似文献
42.
Triazolophanes are ionophores, with preorganized cyclic cavities that have tunable selectivities for halides. The interaction with halides is based on hydrogen bonding between the eight CH hydrogen atoms of the cavity and the halide anion. The rigidity of the cavity in tetraphenylene triazolophane along with the hydrogen bonding favors planar 1:1 complexation of "snugly" encapsulated chloride and bromide. Manipulating the triazolophane's structure by introducing two pyridyl moieties into the cavity alters the receptor's binding mode. This change adds a dipole-promoted driving force that combines with hydrogen bonding to favor the formation of 2:1 sandwich complexes around halides. The potentiometric response of electrodes based on this new ionophore was evaluated for optimal halide selectivity. The new triazolophane-based electrode showed an anti-Hofmeister selectivity toward iodide with a submicromolar detection limit. The stoichiometry of complexation and the stability constants with different halides were evaluated using a segmented sandwich membranes method. The pyridyl-triazolophane demonstrated a response consistent with a 2:1 sandwich-type complex with iodide, in polyvinyl chloride (PVC) membranes. 相似文献
43.
44.
JE Morley F Kaiser WJ Raum HM Perry JF Flood J Jensen AJ Silver E Roberts 《Canadian Metallurgical Quarterly》1997,94(14):7537-7542
A cross-sectional survey was made in 56 exceptionally healthy males, ranging in age from 20 to 84 years. Measurements were made of selected steroidal components and peptidic hormones in blood serum, and cognitive and physical tests were performed. Of those blood serum variables that gave highly significant negative correlations with age (r > -0.6), bioavailable testosterone (BT), dehydroepiandrosterone sulfate (DHEAS), and the ratio of insulin-like growth factor 1 (IGF-1) to growth hormone (GH) showed a stepwise pattern of age-related changes most closely resembling those of the age steps themselves. Of these, BT correlated best with significantly age-correlated cognitive and physical measures. Because DHEAS correlated well with BT and considerably less well than BT with the cognitive and physical measures, it seems likely that BT and/or substances to which BT gives rise in tissues play a more direct role in whatever processes are rate-limiting in the functions measured and that DHEAS relates more indirectly to these functions. The high correlation of IGF-1/GH with age, its relatively low correlation with BT, and the patterns of correlations of IGF-1/GH and BT with significantly age-correlated cognitive and physical measures suggest that the GH-IGF-1 axis and BT play independent roles in affecting these functions. Serial determinations made after oral ingestion of pregnenolone and data from the literature suggest there is interdependence of steroid metabolic systems with those operational in control of interrelations in the GH-IGF-1 axis. Longitudinal concurrent measurements of serum levels of BT, DHEAS, and IGF-1/GH together with detailed studies of their correlations with age-correlated functional measures may be useful in detecting early age-related dysregulations and may be helpful in devising ameliorative approaches. 相似文献
45.
B Guldvog Y L?yning E Hauglie-Hanssen S Flood H Bj?rnaes 《Canadian Metallurgical Quarterly》1994,35(3):554-565
We conducted a retrospective longitudinal self-controlled study of 64 patients aged 4-19 years treated with resective surgery for partial epilepsy from 1952 to 1988. Approximately 60% of patients experienced > 95% reduction in seizure frequency, and 70% had worthwhile improvement of at least 75% reduction. Seizure relief was more frequent among patients who underwent operation after 1978, and significant differences by time period of operation were noted for those with temporal lobe excisions and patients with normal tissue histology. The region of resection and the age at treatment did not provide significant information with respect to seizure outcome. Postresection electrocorticography (ECoG) and EEG of the first postoperative year predicted later seizure outcome. Small neurologic deficits were more common among patients resected in the temporal lobe than in patients resected in the frontal lobe. Half of the patients with preoperative unilateral focal activity and a third of those with bilateral focal activity had normal EEG postoperatively. One fourth had discontinued antiepileptic drug (AED) therapy. As expected, long-term mortality was significantly higher than the mortality of the general population. Seven patients died during follow-up. Two male patients committed suicide. 相似文献
46.
Cortistatin-14, a neuropeptide, is present primarily in the cortex and hippocampus. In the hippocampus, cortistatin-14 inhibits pyramidal cell firing and co-exists with GABA. To determine if cortistatin-14 would impair retention, saline or cortistatin-14 were injected intracerebroventricularly after footshock avoidance training in CD-1 mice. After 1 week, training was resumed to determine the effect of cortistatin-14 on retention. Cortistatin-14 was found to impair retention relative to the control group at doses of 0.5-5.0 micrograms. 相似文献
47.
Programmable controllers (PC's), conceived in 1968 by a team of engineers at G. M.'s Hydramatics Division, have experienced a revolutionary development and gone through four generations of design in a decade. The exponential increase of functional capability was accompanied by a similar development trend in the I/O area from passive I/O modules to intelligent I/O and distributed I/O systems. As these programmable controllers became larger, their chip count increased substantially and, thus, their meantime between failures (MTBF) was lowered despite use of LSI and highly reliable components (?-values substantially above industrial grade) with elevated temperature ratings (85°C) and adherence to conservative component stress levels. 相似文献
48.
RD Oberst MP Hays LK Bohra RK Phebus CT Yamashiro C Paszko-Kolva SJ Flood JM Sargeant JR Gillespie 《Canadian Metallurgical Quarterly》1998,64(9):3389-3396
Presumptive identification of Escherichia coli O157:H7 is possible in an individual, nonmultiplexed PCR if the reaction targets the enterohemorrhagic E. coli (EHEC) eaeA gene. In this report, we describe the development and evaluation of the sensitivity and specificity of a PCR-based 5' nuclease assay for presumptively detecting E. coli O157:H7 DNA. The specificity of the eaeA-based 5' nuclease assay system was sufficient to correctly identify all E. coli O157:H7 strains evaluated, mirroring the previously described specificity of the PCR primers. The SZ-primed, eaeA-targeted 5' nuclease detection assay was capable of rapid, semiautomated, presumptive detection of E. coli O157:H7 when >/=10(3) CFU/ml was present in modified tryptic soy broth (mTSB) or modified E. coli broth and when >/=10(4) CFU/ml was present in ground beef-mTSB mixtures. Incorporating an immunomagnetic separation (IMS) step, followed by a secondary enrichment culturing step and DNA recovery with a QIAamp tissue kit (Qiagen), improved the detection threshold to >/=10(2) CFU/ml. Surprisingly, immediately after IMS, the sensitivity of culturing on sorbitol MacConkey agar containing cefeximine and tellurite (CT-SMAC) was such that identifiable colonies were demonstrated only when >/=10(4) CFU/ml was present in the sample. Several factors that might be involved in creating these false-negative CT-SMAC culture results are discussed. The SZ-primed, eaeA-targeted 5' nuclease detection system demonstrated that it can be integrated readily into standard culturing procedures and that the assay can be useful as a rapid, automatable process for the presumptive identification of E. coli O157:H7 in ground beef and potentially in other food and environmental samples. 相似文献
49.
50.