首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   15914篇
  免费   958篇
  国内免费   18篇
电工技术   153篇
综合类   11篇
化学工业   3739篇
金属工艺   299篇
机械仪表   317篇
建筑科学   565篇
矿业工程   27篇
能源动力   541篇
轻工业   2785篇
水利工程   148篇
石油天然气   54篇
无线电   756篇
一般工业技术   2570篇
冶金工业   2124篇
原子能技术   95篇
自动化技术   2706篇
  2024年   30篇
  2023年   126篇
  2022年   217篇
  2021年   617篇
  2020年   398篇
  2019年   444篇
  2018年   677篇
  2017年   640篇
  2016年   693篇
  2015年   470篇
  2014年   663篇
  2013年   1106篇
  2012年   1002篇
  2011年   1125篇
  2010年   813篇
  2009年   808篇
  2008年   716篇
  2007年   668篇
  2006年   506篇
  2005年   456篇
  2004年   357篇
  2003年   329篇
  2002年   302篇
  2001年   214篇
  2000年   210篇
  1999年   197篇
  1998年   800篇
  1997年   490篇
  1996年   355篇
  1995年   210篇
  1994年   172篇
  1993年   172篇
  1992年   68篇
  1991年   72篇
  1990年   57篇
  1989年   56篇
  1988年   49篇
  1987年   46篇
  1986年   46篇
  1985年   48篇
  1984年   38篇
  1983年   36篇
  1982年   41篇
  1981年   51篇
  1980年   41篇
  1978年   19篇
  1977年   44篇
  1976年   75篇
  1975年   14篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
111.
This research summary discusses the application of neural networks, evolutionary strategies, and other artificial intelligence techniques in the modeling and optimization of the models used for temperature, rolling force, and torque calculation in heavy plate milling.  相似文献   
112.
113.
114.
115.
Immunoreactivity against peptides of the allatostatin family having a typical YXFGL-NH2 C-terminus has been localized in different areas of the central nervous system, stomatogastric nervous system and gut of the cockroach Blattella germanica. In the protocerebrum, the most characteristic immunoreactive perikarya are situated in the lateral and median neurosecretory cell groups. Immunoreactive median neurosecretory cells send their axons around the circumesophageal connectives to form arborizations in the anterior neuropil of the tritocerebrum. A group of cells in the lateral aspect of the tritocerebrum project to the antennal lobes in the deutocerebrum, where immunoreactive arborizations can be seen in the periphery of individual glomeruli. Nerve terminals were shown in the corpora allata. These terminals come from perikarya situated in the lateral neurosecretory cells in the pars lateralis and in the subesophageal ganglion. Immunoreactive axons from median neurosecretory cells and from cells positioned in the anteriormost part of the tritocerebrum enter together in the stomatogastric nervous system and innervate foregut and midgut, especially the crop and the valve between the crop and the midgut. The hindgut is innervated by neurons whose perikarya are located in the last abdominal ganglion. Besides immunoreactivity in neurons, allatostatin-immunoreactive material is present in endocrine cells distributed within the whole midgut epithelium. Possible functions for these peptides according to their localization are discussed.  相似文献   
116.
OBJECTIVE: To improve the specificity and sensitivity of the prostate-specific-antigen (PSA) assay for the distinction between prostate cancer and benign prostate hyperplasia (BPH). METHODS: Two sensitive immunoassays, one that measures free PSA and PSA complexed to alpha 1-antichymotrypsin (alpha 1-ACT) with the same efficiency (PSAag assay) and another that specifically measures the complex between PSA and alpha 1-ACT, have been designed to measure the PSA forms in the plasma of 84 patients with prostate disease and in the seminal plasma from 60 healthy individuals. RESULTS: The proportion of plasma PSA in complex with alpha 1-ACT was significantly higher in the 34 patients with prostate cancer (89 +/- 12%, mean +/- SD; median, 91%) than in the 50 patients with BPH (71 +/- 12%; 73%) and did not correlate with the total amount of PSA. Normal seminal plasma (n = 60) had 2.1 +/- 0.6 mg/ml PSA, 175 +/- 62 microns/ml alpha 1-ACT and 9.6 +/- 3.4 micrograms/ml PSA: alpha 1-ACT complex. CONCLUSION: These results confirm that PSA: alpha 1-ACT may be a good marker for a differential diagnosis of carcinoma of the prostate and BPH.  相似文献   
117.
A versatile potentiometer that works with electrode arrays in flow injection and/or monosegmented flow systems is described. The potentiometer is controlled by a microcomputer that allows individual, sequential multiplexed or random accesses to eight electrodes while employing only one reference electrode. The instrument was demonstrated by monitoring an array of seven flow-through ion-selective electrodes for Ag(+) and for three electrodes for Cl(-), Ca(2+) and K(+). The figures of merit of the individual and multiplexed (summed) readings of the electrode array were compared. The absolute standard deviation of the measurements made by summing the potential of two or more electrodes was maintained constant, thus improving the precision of the measurements. This result shows that an attempt to combine the signals of the electrodes to produce a more intense signal in the Hadamard strategy is feasible and accompanied by a proportional improvement in the precision of individual measurements. The preliminary tests suggest that the system can allow for 270 determinations per hour, with a linear range from 1.0 x 10(-2) to 1.0 x 10(-4) mol l(-1) for the three di inverted exclamation markerent analytes. Detection limits were estimated as 3.1 x 10(-5), 3.0 x 10(-6) and 1.0 x 10(-5) mol l(-1) for Cl(-), Ca(2+) and K(+), respectively.  相似文献   
118.
119.
This study examined the nature and impact of dyadic perfectionism over a 3-month interval within a sample of 116 college students who were currently involved in an intimate heterosexual relationship. Dyadic perfectionism scores were stable and correlated as expected with scores on concurrent measures of adult attachment orientations and relationship satisfaction. Logistic regression analyses revealed that, controlling for initial commitment status and adult attachment orientations, Time 1 dyadic perfectionism scores significantly and uniquely predicted relationship continuity 3 months later. Lastly, controlling for social desirability, relationship commitment status, and Time 1 adult attachment orientation scores, Time 1 dyadic perfectionism scores also uniquely predicted Time 2 relationship distress. Findings provide additional evidence that dyadic perfectionism is a risk factor for relationship dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
120.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号