全文获取类型
收费全文 | 9851篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 21篇 |
综合类 | 6篇 |
化学工业 | 281篇 |
金属工艺 | 31篇 |
机械仪表 | 13篇 |
建筑科学 | 36篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 79篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 113篇 |
一般工业技术 | 186篇 |
冶金工业 | 8901篇 |
原子能技术 | 9篇 |
自动化技术 | 169篇 |
出版年
2020年 | 14篇 |
2018年 | 15篇 |
2015年 | 13篇 |
2014年 | 16篇 |
2013年 | 48篇 |
2012年 | 37篇 |
2011年 | 50篇 |
2010年 | 30篇 |
2009年 | 32篇 |
2008年 | 37篇 |
2007年 | 55篇 |
2006年 | 35篇 |
2005年 | 34篇 |
2004年 | 30篇 |
2003年 | 42篇 |
2002年 | 26篇 |
2001年 | 31篇 |
2000年 | 32篇 |
1999年 | 311篇 |
1998年 | 2796篇 |
1997年 | 1582篇 |
1996年 | 1008篇 |
1995年 | 586篇 |
1994年 | 465篇 |
1993年 | 570篇 |
1992年 | 85篇 |
1991年 | 117篇 |
1990年 | 109篇 |
1989年 | 102篇 |
1988年 | 111篇 |
1987年 | 105篇 |
1986年 | 105篇 |
1985年 | 79篇 |
1984年 | 17篇 |
1983年 | 22篇 |
1982年 | 53篇 |
1981年 | 55篇 |
1980年 | 90篇 |
1979年 | 14篇 |
1978年 | 26篇 |
1977年 | 205篇 |
1976年 | 477篇 |
1975年 | 21篇 |
1974年 | 16篇 |
1973年 | 13篇 |
1972年 | 16篇 |
1971年 | 14篇 |
1970年 | 13篇 |
1969年 | 19篇 |
1968年 | 13篇 |
排序方式: 共有9878条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
E Tayama Y Niimi Y Takami Y Ohashi G Ohtsuka JA Glueck J Mueller Y Nosé 《Canadian Metallurgical Quarterly》1997,21(12):1284-1287
Centrifugal pumps are generally employed as nonpulsatile blood flow pumps; however, these pumps can produce pulsatile flow by periodically alternating the impeller rotation speed. This study investigates blood trauma due to the effect of pulse frequency and various ranges of pump speed. The hemolysis tests were conducted using the Gyro C1E3 pump. The study was divided into the following categories: Group 1 in a nonpulsatile mode; Group 2 operated at 40 bpm with 30% of speed variance; Group 3, 60 bpm with 30% of speed variance; Group 4, 40 bpm with 70% of speed variance; and Group 5, 60 bpm with 70% of speed variance. A flow rate of 3 L/min and a total pressure head of 200 mm Hg were employed in all groups to simulate a percutaneous cardiopulmonary support condition. There were no significant differences in the hemolysis levels among Groups 1, 2, and 3. However, Groups 4 and 5 exhibited a significantly higher hemolysis rate compared to the other groups. These results indicate that a high rate of speed variance increases hemolysis; however, a range of less than 30% does not affect hemolysis. The pulse rate has no significant effect on hemolysis. In conclusion, the higher speed variance increases the hemolysis level when a pulsatile mode is applied with a centrifugal pump at the given test conditions. However, a speed variance of less than 30% or a pulse rate of less than 60 bpm does not affect hemolysis. 相似文献
105.
U Simonsen D Prieto JA Delgado M Hernández L Resel I Saenz de Tejada A García-Sacristán 《Canadian Metallurgical Quarterly》1997,92(3):269-275
When rotating stripes or other periodic stimuli cross the retina at a critical rate, a reversal in the direction of motion of the stimuli is often seen. This illusion of motion perception was used to explore the roles of retinal and perceived motion in the generation of optokinetic nystagmus. Here we show that optokinetic nystagmus is disrupted during the perception of this illusion. Thus, when perceived and actual motion are in conflict, subjects fail to track the veridical movement. This observation suggests that the perception of motion can directly influence optokinetic nystagmus, even in the presence of a moving retinal image. A conflict in the neural representation of motion in different brain areas may explain these findings. 相似文献
106.
It is very likely that disagreements leading to opposing factions and conflict are universal, and part of the very nature of academic (intellectually and behaviorally expressive) institutions. Analytic "education" shares in this tradition. Internal conflict and splits within and between psychoanalytic training centers have continued to reappear throughout the history of the psychoanalytic movement. They were greatly magnified with the formation of "official, formal training." The authors propose highlighting the composite of personal and professional genealogies within the training analysis couple as opportunities to provide experiential, graphic consideration of the affiliative, disaffiliative, and identification processes, greatly enhanced when analysands, training analysts, and the Institute regard this as a valuable method to study the parallel phenomena evoked, experienced, and shared communally. These personal and group considerations are part of the shared genealogy and history of psychoanalytic Institute and Society life, their "parent" organizations, and "relatives" nationally and internationally. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
A method is described for searching protein sequence databases using tandem mass spectra of tryptic peptides. The approach uses a de novo sequencing algorithm to derive a short list of possible sequence candidates which serve as query sequences in a subsequent homology-based database search routine. The sequencing algorithm employs a graph theory approach similar to previously described sequencing programs. In addition, amino acid composition, peptide sequence tags and incomplete or ambiguous Edman sequence data can be used to aid in the sequence determinations. Although sequencing of peptides from tandem mass spectra is possible, one of the frequently encountered difficulties is that several alternative sequences can be deduced from one spectrum. Most of the alternative sequences, however, are sufficiently similar for a homology-based sequence database search to be possible. Unfortunately, the available protein sequence database search algorithms (e.g. Blast or FASTA) require a single unambiguous sequence as input. Here we describe how the publicly available FASTA computer program was modified in order to search protein databases more effectively in spite of the ambiguities intrinsic in de novo peptide sequencing algorithms. 相似文献
108.
Treatment and prognosis of urinary bladder cancer largely are determined by the tumor stage and presence of metastases. MR imaging and clinical staging complement each other. MR imaging is the most accurate technique for differentiating the various stages of deep tumor infiltration and detection of metastases, whereas clinical staging is the best technique for differentiating between postbiopsy effects and the various stages of superficial tumors. The role of MR imaging in staging of this disease and monitoring of therapy is reviewed and illustrated. Finally, the authors present an overview of current and future applications of this technique. 相似文献
109.
There complete 18S ribosomal RNA gene sequences from the rumen ciliates, Entodinium caudatum (1,639 bp), Epidinium caudatum (1,638 bp), and Polyplastron multivesiculatum (1,640 bp) were determined and confirmed in the opposite direction. Trees produced using maximum parsimony and distance-matrix methods (least squares and neighbour-joining), with strong bootstrap support, depict the rumen ciliates as a monophyletic group. Entodinium caudatum is the earliest branching rumen ciliate. However, Entodinium simplex does not pair with En. caudatum, but rather with Polyplastron multivesiculatum. Signature sequences for these rumen ciliates reveal that the published SSrRNA gene sequence from En. simplex is in fact a Polyplastron species. The free-living haptorian ciliates, The Loxophyllum, Homalozoon and Spathidium (Subclass Haptoria), are monophyletic and are the sister group to the rumen ciliates. The litostomes (Class Litostomatea), consisting of the haptorians and the rumen ciliates, are also a monophyletic group. 相似文献
110.