全文获取类型
收费全文 | 12049篇 |
免费 | 191篇 |
国内免费 | 86篇 |
专业分类
电工技术 | 144篇 |
综合类 | 55篇 |
化学工业 | 1062篇 |
金属工艺 | 117篇 |
机械仪表 | 186篇 |
建筑科学 | 314篇 |
矿业工程 | 29篇 |
能源动力 | 124篇 |
轻工业 | 582篇 |
水利工程 | 71篇 |
石油天然气 | 56篇 |
武器工业 | 7篇 |
无线电 | 768篇 |
一般工业技术 | 991篇 |
冶金工业 | 6950篇 |
原子能技术 | 71篇 |
自动化技术 | 799篇 |
出版年
2022年 | 47篇 |
2021年 | 65篇 |
2020年 | 44篇 |
2019年 | 52篇 |
2018年 | 101篇 |
2017年 | 76篇 |
2016年 | 85篇 |
2015年 | 98篇 |
2014年 | 125篇 |
2013年 | 292篇 |
2012年 | 205篇 |
2011年 | 248篇 |
2010年 | 188篇 |
2009年 | 204篇 |
2008年 | 245篇 |
2007年 | 242篇 |
2006年 | 245篇 |
2005年 | 238篇 |
2004年 | 200篇 |
2003年 | 179篇 |
2002年 | 159篇 |
2001年 | 157篇 |
2000年 | 162篇 |
1999年 | 307篇 |
1998年 | 2116篇 |
1997年 | 1140篇 |
1996年 | 782篇 |
1995年 | 465篇 |
1994年 | 424篇 |
1993年 | 446篇 |
1992年 | 169篇 |
1991年 | 160篇 |
1990年 | 165篇 |
1989年 | 156篇 |
1988年 | 166篇 |
1987年 | 168篇 |
1986年 | 155篇 |
1985年 | 179篇 |
1984年 | 105篇 |
1983年 | 83篇 |
1982年 | 104篇 |
1981年 | 109篇 |
1980年 | 100篇 |
1979年 | 73篇 |
1978年 | 77篇 |
1977年 | 179篇 |
1976年 | 348篇 |
1975年 | 44篇 |
1973年 | 52篇 |
1972年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Sera from 82 cases of leptospirosis (confirmed by micro-agglutination tests or IFAT) and 108 patients with other diseases were investigated using the microcapsule agglutination test (MCAT) for leptospirosis. The overall sensitivity (90.2%), specificity (96.3%), positive predictive value (94.9%), negative predictive value (92.9%), and accuracy of the MCAT (93.7%) were encouraging. MCAT is simple, can be performed by unskilled personnel with minimum laboratory facilities, and produces results in 3 h. MCAT would be a reliable serodiagnostic test for rapidly screening individuals for leptospirosis, in various geographical areas of Thailand. 相似文献
92.
M Brown M Webb E Phillips E Skidmore P McIntyre 《Canadian Metallurgical Quarterly》1995,73(7):780-786
We describe the results of functional studies on DNA clones encoding functional bradykinin receptors derived from human, rat, and mouse sources and including both genomic and complementary DNA clones. In both the Xenopus oocyte and the COS cell expression systems, the receptors from human and rat showed the pharmacological properties of B2 receptors, but receptors from mouse displayed both B1- and B2-like pharmacological properties. We further investigated the molecular relationship between the B1 and B2 receptor subtypes expressed by a human fibroblast cell line, and we demonstrate that these two receptor subtypes are encoded by distinct mRNA species. 相似文献
93.
94.
OBJECTIVE: To know the variability in the interpretation (normal/pathological) of posteroanterior view chest radiograph and the associated factors between a medical primary care community and a Gold Standard (GS) from 3 reference radiologists. DESIGN: Crossover study. SETTING: Primary care. Teaching health centers of Elche. METHODS: Interobserver percentage agreement (IPA) and Kappa statistic (K) were used to analyse the interobserver agreement (IA) between the GS and every of the participants in interpretation of 100 radiographs. Intraobserver variability was assessed with a second review. Using uni and multivariant analysis some possibly associated factors were studied. RESULTS: Overall IPA and K were 71.3% (CI 95%: 69.2-73.3) and 0.41 (CI 95%: 0.36-0.46) respectively. Time employed in radiographs reading and time passed after medicine studies finished were independently and significantly associated to higher and lower interobserver agreement results respectively, whereas recent professional experience, permanent job and age were not associated. Professional training is the variable that most explain the inter and intraobserver variability. CONCLUSIONS: Overall IA is acceptable. The IA showed by the participants trained under the MIR system is good but the IA achieved by the rest of participants is not acceptable. It is necessary a training which increase the clinical competence, as it does MIR training. 相似文献
95.
Perchloric acid (70%) was used to create simulated periapical lesions in tooth sockets of 15 dentate cadaver jaw specimens. Using the Trophy USA direct digital radiographic system, linear images were captured at selected time intervals after initial acid application and altered by contrast reversal, pseudocolor enhancement, and two forms of histogram equalization. The 525 total images were randomized for display on a computer monitor for evaluation by five endodontists. Images were evaluated twice by each rater, with viewings 1 to 2 wk apart. Statistical analysis determined interrater variability, intrarater reproducibility, and the relative merits of each enhancement technique. At 8, 12, 16, and 24 h after acid application, both techniques of histogram equalization yielded a statistically significant improvement over reverse contrast in perception of periapical patholais. Linear and pseudocolor-enhanced images were also significantly more diagnostic than reverse contrast at 12, 16, and 24 h. Intrarater reproducibility showed moderate agreement, but analysis showed only a fair level of interrater agreement. 相似文献
96.
CD Holyoak M Stratford Z McMullin MB Cole K Crimmins AJ Brown PJ Coote 《Canadian Metallurgical Quarterly》1996,62(9):3158-3164
The weak acid sorbic acid transiently inhibited the growth of Saccharomyces cerevisiae in media at low pH. During a lag period, the length of which depended on the severity of this weak-acid stress, yeast cells appeared to adapt to this stress, eventually recovering and growing normally. This adaptation to weak-acid stress was not due to metabolism and removal of the sorbic acid. A pma1-205 mutant, with about half the normal membrane H+-ATPase activity, was shown to be more sensitive to sorbic acid than its parent. Sorbic acid appeared to stimulate plasma membrane H+-ATPase activity in both PMA1 and pma1-205. Consistent with this, cellular ATP levels showed drastic reductions, the extent of which depended on the severity of weak-acid stress. The weak acid did not appear to affect the synthesis of ATP because CO2 production and O2 consumption were not affected significantly in PMA1 and pma1-205 cells. However, a glycolytic mutant, with about one-third the normal pyruvate kinase and phosphofructokinase activity and hence a reduced capacity to generate ATP, was more sensitive to sorbic acid than its isogenic parent. These data are consistent with the idea that adaptation by yeast cells to sorbic acid is dependent on (i) the restoration of internal pH via the export of protons by the membrane H+-ATPase in an energy-demanding process and (ii) the generation of sufficient ATP to drive this process and still allow growth. 相似文献
97.
Estimation is influenced by a variety of processes: application of heuristics, domain-specific reasoning, and intuitive statistical induction among them. In this article, the authors propose the metrics and mapping framework to account for how these processes are integrated to generate estimates. This framework identifies 2 types of information as critical: knowledge of distributional properties (metric knowledge) and knowledge of relative status of individual entities within the distribution (mapping knowledge). Heuristics and domain-specific knowledge are both viewed as cues that contribute to mapping knowledge; intuitive statistical induction is viewed as providing cues to metric properties. Results of 4 experiments illustrate the framework's usefulness for integrating these types of information and for predicting when people emphasize heuristics and when they emphasize domain-specific knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
99.
ML Israel DA Connolly RE von Heyn JM Rock PW Smith 《Canadian Metallurgical Quarterly》1993,24(4):343-355
Fifty-two case-hardened, severely self-abusive and aggressive autistic and retarded students, living in six different community residences, were trained to exit their residences, without the presence or assistance of staff, when a fire alarm sounded at night. On a pretest, prior to an 11-week period of intensive environmental and behavioral interventions, only 25% of the students exited within 2 1/2 minutes and independent of staff assistance. At posttest, 100% exited successfully, in a mean evacuation time of 60 seconds. The study was conducted at the Behavior Research Institute (BRI). 相似文献
100.