全文获取类型
收费全文 | 2067篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 197篇 |
金属工艺 | 14篇 |
机械仪表 | 14篇 |
建筑科学 | 54篇 |
矿业工程 | 1篇 |
能源动力 | 18篇 |
轻工业 | 163篇 |
水利工程 | 7篇 |
石油天然气 | 4篇 |
无线电 | 67篇 |
一般工业技术 | 143篇 |
冶金工业 | 1280篇 |
原子能技术 | 17篇 |
自动化技术 | 108篇 |
出版年
2022年 | 13篇 |
2020年 | 12篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 17篇 |
2016年 | 17篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 72篇 |
2012年 | 37篇 |
2011年 | 66篇 |
2010年 | 42篇 |
2009年 | 44篇 |
2008年 | 57篇 |
2007年 | 56篇 |
2006年 | 57篇 |
2005年 | 52篇 |
2004年 | 24篇 |
2003年 | 41篇 |
2002年 | 36篇 |
2001年 | 23篇 |
2000年 | 30篇 |
1999年 | 46篇 |
1998年 | 278篇 |
1997年 | 153篇 |
1996年 | 123篇 |
1995年 | 69篇 |
1994年 | 68篇 |
1993年 | 80篇 |
1992年 | 21篇 |
1991年 | 30篇 |
1990年 | 36篇 |
1989年 | 36篇 |
1988年 | 29篇 |
1987年 | 36篇 |
1986年 | 26篇 |
1985年 | 32篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 46篇 |
1976年 | 55篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有2090条查询结果,搜索用时 15 毫秒
1.
Alkali-metal carbonate salts meet the requirements for high-temperature solar central receiver systems, but because of their corrosiveness they present special problems in the design of storage tanks. In order to reduce corrosion and temperature sufficiently to retain strength in the storage containing wall, internal and thermal insulation is required. We present design options and operation criteria for sensible-heat, molten-salt storage with internal insulation. 相似文献
2.
Claudia Stewart Nicole Lum Robert Hill Robert Stephens Paul Rudnick Lynn Rassmussen 《Journal of The Association for Laboratory Automation》2003,8(2):64-65
Primer walking of cloned DNA is a standard research tool. It has been used in the past to determine the sequence of individual clones of interest. With the expansion of DNA sequencing capacity the need to be able to walk larger numbers of clones has become necessary. Our laboratory is a mid-sized genomics facility. In conjunction with the Advanced Biomedical Computing Center (ABCC) we have developed methods for automating the primer selection, DNA sequencing, contig assembly and sequence analysis for clones arrayed in microtiter format. This approach has allowed us to walk 475 clones (five microtiter plates) selected from a cDNA library. 相似文献
3.
Free and bound hydrosoluble protein extracts were prepared from four anatomical areas of a multiple sclerosis (MS) cerebrum and from corresponding anatomical areas of a normal (non-MS) control. Increased levels of IgG and anti-myelin basic protein antibodies (anti-MBP) were detected in all MS samples and they were undetectable in the controls. IgG and anti-MBP from free (unbound) hydrosoluble protein extracts are defined as free IgG and free anti-MBP while IgG and anti-MBP from tissue bound protein extracts are defined as bound IgG and bound anti-MBP. IgG was purified from free protein extracts by protein G Sepharose affinity chromatography and anti-MBP was further isolated from purified IgG by antigen specific (MBP) Sepharose affinity chromatography. Free and bound anti-MBP were reacted with 20 synthetic peptides of human MBP prepared by the Fmoc method. Free anti-MBP, whether in the context of whole protein extracts, or as purified IgG or as purified antibody was completely neutralized by peptides #12, #15, #56 and #56* containing overall residues 75-106, partially neutralized by peptides #27, #16 and #21 containing overall residues 61-83 and did not react with the remaining 13 peptides. Tissue bound anti-MBP was completely neutralized only by peptides #12, #15, #56 and #56* (overall residues 75-106) and showed no reactivity towards the remaining 16 peptides including peptides #27, #16 and #21. Synthetic peptide specificity of free anti-MBP purified from MS cerebrum was identical to previously reported specificity of free anti-MBP from MS cerebrospinal fluid (CSF), while tissue bound anti-MBP, as well as bound anti-MBP from CSF had a more restricted synthetic peptide specificity than free anti-MBP. This suggests that the most likely epitope of anti-MBP is located between residues 84 and 95 of human MBP just proximal to the tri-proline sequence (99-101). 相似文献
4.
Resurgence has been shown in human and nonhuman operant behavior, but not in derived relational responses. The present study examined this issue. Twenty-three undergraduates were trained to make conditional discriminations in a three-choice matching-to-sample paradigm. The training resulted in three equivalence classes, each consisting of four arbitrarily configured visual stimuli. The same 12 stimuli were then reorganized, and the conditional discrimination training was repeated such that three new classes were possible. In a subsequent test of derived relations, most subjects showed response patterns that were consistent with the altered conditional discriminations. Subjects were then exposed to conditional discrimination trials under extinction. Most subjects continued to respond consistently with the most recently reinforced conditional discrimination trials. During the next phase, subjects were exposed to symmetry and equivalence trials. Responses consistent with the most recent training produced feedback saying that the responses were incorrect, whereas other responses produced no feedback. Most subjects showed a resurgence of responding that was consistent with their earlier training. Finally, subjects were exposed to conditional discrimination trials carried out in extinction. Most subjects continued to show a resurgence of responding that was consistent with their early training. 相似文献
5.
6.
Assessed the retention of memory units for word-like strings of letters using the perceptions of 120 undergraduates in 2 experiments in determining how frequently various letters appeared. A series of strings was presented at 1 of 3 exposure durations. Within the series, the frequencies of occurrence of different strings and of the letters composing the strings were varied orthogonally. Results indicate that, at relatively long exposure durations, Ss could discriminate the frequency of occurrence for both strings and their constituent letters. The formation of global-level (string) memory units was indicated by judgments of string frequency being unaffected by either the frequencies of their component letters or experimental conditions (brief exposures) that prohibited accurate judgment of letter frequency. Although judgments of letter frequency were sometimes biased by the frequency of the strings containing the letters, the success with which the judgments discriminated different levels of letter frequency did not depend on the activation of string-level memory units. Furthermore, Ss' frequency judgments for letters were not predictable from their recall of the strings containing the letters. Results provide evidence for the formation of element-level (letter) memory units. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Self-disclosure plays a central role in the development and maintenance of relationships. One way that researchers have explored these processes is by studying the links between self-disclosure and liking. Using meta-analytic procedures, the present work sought to clarify and review this literature by evaluating the evidence for 3 distinct disclosure-liking effects. Significant disclosure-liking relations were found for each effect: (1) People who engage in intimate disclosures tend to be liked more than people who disclose at lower levels, (2) people disclose more to those whom they initially like, and (3) people like others as a result of having disclosed to them. In addition, the relation between disclosure and liking was moderated by a number of variables, including study paradigm, type of disclosure, and gender of the discloser. Taken together, these results suggest that various disclosure-liking effects can be integrated and viewed as operating together within a dynamic interpersonal system. Implications for theory development are discussed, and avenues for future research are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
During the early development of skeletal muscle, cardiac isotypes of several contractile proteins are known to be transiently expressed. We report here that skeletal muscle developing in vivo, as well as primary cultures derived from skeletal muscle, express mRNA encoding the cardiac dihydropyridine-sensitive calcium channel. The mRNA is detectable at high concentration at the earliest stage tested in vivo and diminishes rapidly in concentration as myofibers mature. The concentration of the cardiac calcium channel mRNA also diminishes during the in vivo development of skeletal muscle in a genetically paralyzed mouse (mdg), indicating that muscle contractile activity is not necessary for the down-regulation. In contrast, mRNA for the skeletal muscle-specific calcium channel accumulates gradually in developing skeletal muscle. A similar temporal pattern of expression is also seen in primary cultures of skeletal myotubes. These results raise the question of whether the cardiac calcium channel may be functionally important during the early development of skeletal myofibers. 相似文献
9.
Devenport Jill A.; Patterson Megan R.; Devenport Lynn D. 《Canadian Metallurgical Quarterly》2005,119(3):352
The variability of most environments taxes foraging decisions by increasing the uncertainty of the information available. One solution to the problem is to use dynamic averaging, as do some granivores and carnivores. Arguably, the same strategy could be useful for grazing herbivores, even though their food renews and is more homogeneously distributed. Horses (Equus callabus) were given choices between variable patches after short or long delays. When patch information was current, horses returned to the patch that was recently best, whereas those without current information matched choices to the long-term average values of the patches. These results demonstrate that a grazing species uses dynamic averaging and indicate that, like granivores and carnivores, they can use temporal weighting to optimize foraging decisions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.