全文获取类型
收费全文 | 24260篇 |
免费 | 1494篇 |
国内免费 | 67篇 |
专业分类
电工技术 | 298篇 |
综合类 | 23篇 |
化学工业 | 5312篇 |
金属工艺 | 884篇 |
机械仪表 | 1498篇 |
建筑科学 | 513篇 |
矿业工程 | 13篇 |
能源动力 | 866篇 |
轻工业 | 2221篇 |
水利工程 | 125篇 |
石油天然气 | 33篇 |
无线电 | 3938篇 |
一般工业技术 | 5046篇 |
冶金工业 | 2202篇 |
原子能技术 | 313篇 |
自动化技术 | 2536篇 |
出版年
2023年 | 252篇 |
2022年 | 386篇 |
2021年 | 687篇 |
2020年 | 485篇 |
2019年 | 577篇 |
2018年 | 657篇 |
2017年 | 732篇 |
2016年 | 833篇 |
2015年 | 721篇 |
2014年 | 1057篇 |
2013年 | 1593篇 |
2012年 | 1500篇 |
2011年 | 1832篇 |
2010年 | 1335篇 |
2009年 | 1340篇 |
2008年 | 1296篇 |
2007年 | 994篇 |
2006年 | 826篇 |
2005年 | 774篇 |
2004年 | 744篇 |
2003年 | 681篇 |
2002年 | 659篇 |
2001年 | 516篇 |
2000年 | 460篇 |
1999年 | 456篇 |
1998年 | 847篇 |
1997年 | 585篇 |
1996年 | 398篇 |
1995年 | 297篇 |
1994年 | 288篇 |
1993年 | 262篇 |
1992年 | 181篇 |
1991年 | 157篇 |
1990年 | 147篇 |
1989年 | 157篇 |
1988年 | 97篇 |
1987年 | 103篇 |
1986年 | 75篇 |
1985年 | 107篇 |
1984年 | 89篇 |
1983年 | 52篇 |
1982年 | 51篇 |
1981年 | 51篇 |
1980年 | 44篇 |
1979年 | 40篇 |
1978年 | 36篇 |
1977年 | 55篇 |
1976年 | 87篇 |
1975年 | 42篇 |
1973年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Robotic synthesis is making possible the synthesis of large, systematically designed sets of compounds. We analyze a 512-compound set that is a 2(9) full factorial experimental design using a recursive partitioning algorithm, FIRM, and a high-dimension visualization tool, TempleMVV. These techniques are used to quickly and easily identify the main trends in the data set and also identify unusual observations. We show that analytical and visualization methods can be used synergistically to analyze a large, complex, high-dimensional data set. We also show that a fractional factorial design of 128 compounds would give essentially the same information. 相似文献
32.
33.
The secondary effluent from municipal plants in Korea generally represents higher BOD with lower SS. Therefore, more soluble forms of organics and NH4-N need to be removed to improve its effluent for reuse. In this study reuse possibility of secondary effluent and CSO (combined sewer overflow) using BAF (biological aerated filter) was evaluated. The tertiary application with 1.2 h EBCT, SS, BOD and COD showed stable concentrations less than 1.3, 1.3 and 6.2 mg/L, respectively. Nitrogen could be nitrified even at 7 degrees suggesting BAF can be used for a water reuse method as well as an effective add-on facility in cold regions. However, BAF was not stable with CSO application at increased flow rates suggesting CSO must be equalised prior to application. Disinfection was necessary even during normal weather conditions. 相似文献
34.
35.
36.
37.
A new method to predict the critical heat flux (CHF) is proposed, based on the fuzzy clustering and artificial neural network. The fuzzy clustering classifies the experimental CHF data into a few data clusters (data groups) according to the data characteristics. After classification of the experimental data, the characteristics of the resulting clusters are discussed with emphasis on the distribution of the experimental conditions and physical mechanism. The CHF data in each group are trained in an artificial neural network to predict the CHF. The artificial neural network adjusts the weight so as to minimize the prediction error within the corresponding cluster. Application of the proposed method to the KAIST CHF data bank shows good prediction capability of the CHF, better than other existing methods. 相似文献
38.
We have previously observed that bovine papillomavirus type 1 (BPV-1) induces the appearance of five cellular proteins in C127 mouse fibroblasts, four of which appear to arise by altered processing of resident endoplasmic reticulum proteins. Studies of various cell lines revealed that expression of the 3' end of the BPV early region was sufficient for induction of these changes. To identify the BPV gene responsible, we have utilized the simian virus 40 (SV40)/BPV-1 recombinant virus Pava-1, which expresses the 3' end of the BPV early region behind an SV40 early promoter. C127 cells infected with Pava-1 for 48 h show the expected BPV-associated alterations, as do cells infected with Pava constructs mutated in the E5 or E2 genes. However, a mutation in the start codon of a previously ignored open reading frame extending from nucleotides 4013 to 4170 (E5B) eliminated the BPV-associated changes. Similar results were obtained with COS cells infected with the Pava mutants and C127 cells transformed by full-length mutated BPV. Despite its influence on the processing of cellular endoplasmic reticulum proteins, this mutation in E5B did not alter BPV-transforming efficiency or the ability of transformants to form colonies in soft agar. The E5B open reading frame encodes a hydrophobic 52-amino-acid polypeptide that shares structural similarities with HPV6 E5A and HPV16 E5. Speculations on a role for E5B in the viral life cycle are discussed. 相似文献
39.
A survey of heterosexually active college students gathered information about condom use, self-efficacy (SE), outcome expectancies, sexual attitudes, peer group influences, AIDS knowledge, and a perceived vulnerability to AIDS. On the basis of A. Bandura's (1986) social-cognitive theory, a structural model with SE as the central mediator was formulated and evaluated with LISREL. This model explained 46% of the variance in condom use from judgments of SE and effects attributable to peers and 53% of the variance in SE from outcome expectancies and peer group influences. Sexual attitudes, AIDS knowledge, and perceived vulnerability did not predict condom use. Most students were well-informed about HIV transmission but reported not feeling at risk, even though many engaged in risky sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.
In this paper, a mixed approach for probabilistic structural durability design of mechanical systems is proposed. In this approach, a deterministic design optimization that considers structural crack initiation and crack propagation lives at critical points of the structural component as design constraints is performed first. After an optimal design is obtained, a reliability analysis is performed to ascertain if the deterministic optimal design is reliable. If the probability of the failure of the deterministic optimal design is found to be acceptable, a reliability-based design approach that employs a set of interactive design steps, such as trade-off analysis and what-if study, is used to obtain a near-optimal design that is reliable with an affordable computational cost. A 3-D tracked vehicle roadarm is employed to demonstrate the feasibility of the proposed approach. 相似文献