全文获取类型
收费全文 | 10581篇 |
免费 | 112篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 36篇 |
综合类 | 6篇 |
化学工业 | 302篇 |
金属工艺 | 22篇 |
机械仪表 | 40篇 |
建筑科学 | 73篇 |
矿业工程 | 3篇 |
能源动力 | 34篇 |
轻工业 | 139篇 |
水利工程 | 16篇 |
石油天然气 | 10篇 |
武器工业 | 1篇 |
无线电 | 315篇 |
一般工业技术 | 403篇 |
冶金工业 | 8977篇 |
原子能技术 | 24篇 |
自动化技术 | 297篇 |
出版年
2022年 | 13篇 |
2021年 | 21篇 |
2020年 | 29篇 |
2019年 | 28篇 |
2018年 | 36篇 |
2017年 | 27篇 |
2016年 | 29篇 |
2015年 | 46篇 |
2014年 | 41篇 |
2013年 | 122篇 |
2012年 | 52篇 |
2011年 | 79篇 |
2010年 | 59篇 |
2009年 | 47篇 |
2008年 | 76篇 |
2007年 | 65篇 |
2006年 | 63篇 |
2005年 | 62篇 |
2004年 | 69篇 |
2003年 | 61篇 |
2002年 | 50篇 |
2001年 | 38篇 |
2000年 | 53篇 |
1999年 | 332篇 |
1998年 | 2864篇 |
1997年 | 1593篇 |
1996年 | 1013篇 |
1995年 | 598篇 |
1994年 | 469篇 |
1993年 | 572篇 |
1992年 | 97篇 |
1991年 | 124篇 |
1990年 | 137篇 |
1989年 | 114篇 |
1988年 | 112篇 |
1987年 | 113篇 |
1986年 | 125篇 |
1985年 | 98篇 |
1984年 | 24篇 |
1983年 | 45篇 |
1982年 | 54篇 |
1981年 | 61篇 |
1980年 | 102篇 |
1978年 | 29篇 |
1977年 | 208篇 |
1976年 | 462篇 |
1975年 | 24篇 |
1974年 | 12篇 |
1972年 | 13篇 |
1970年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
131.
The mechanism of neurite penetration of three-dimensional fibrin matrices was investigated by culturing embryonic chick dorsal root ganglia (DRGs) within fibrin gels, upon fibrin gels, and upon laminin. The length of neurites within three-dimensional matrices of fibrin was decreased in a concentration-dependent manner by agents that inhibited plasmin, e.g. aprotinin, or that inhibited plasminogen activation, e.g., epsilon-aminocaproic acid (EACA), or plasminogen antiserum. In contrast, such agents increased the length of neurites growing out from DRGs cultured upon two-dimensional substrates of fibrin and had no effect on the length of neurites growing out from DRGs cultured upon laminin. Visualization of neurites within three-dimensional fibrin matrices demonstrated that the distance between fibrin strands was much smaller than the diameter of neurites. All these data were consistent with the hypothesis that fibrinolysis localized to the region of the neurite tip is an important mechanism for neurite penetration of a physical barrier of fibrin strands arranged in a three-dimensional matrix. 相似文献
132.
In the 1960s the promise of the Brantigan lung reduction surgery was shattered when it was shown that the improvement in airway conductance drifted back towards the preoperative value over a period of 12 to 18 months. Since then there has been a marked improvement in our understanding of emphysema, its pathology, and techniques for obtaining images of the lung. In addition, reliable automated cardiopulmonary and physiologic testing, advances in critical care medicine, and new pharmacologic agents have improved patient care. Surgical techniques now allow better control of air leaks and access to anatomic regions not previously accessible. The combination of all of the above makes lung reduction surgery worth re-examining as a palliative procedure for severely symptomatic patients. Clearly, it is not a panacea but can in some cases produce dramatic improvements in symptomatology and quality of life. This article presents the available data describing potential mechanisms of improvement and clinical outcomes following lung reduction surgery. It also outlines areas that need further work, such as patient selection and surgical techniques. 相似文献
133.
134.
PH Wooley C Schaefer JD Whalen JA Dutcher DF Counts 《Canadian Metallurgical Quarterly》1997,24(5):890-898
OBJECTIVE: Platelet factor 4 (PF-4) is a critical alpha chemokine in inflammation and injury responses, with multiple effects upon cellular activities. Discrete peptide sequences of the PF-4 molecule have been shown to retain biological activity. Our aim was to examine the influence of the PF-4 derived octapeptide (CT-112; TTSQVRPR) on type II collagen induced arthritis in mice, to determine if this peptide exhibited antiinflammatory properties. METHODS: DBA/1 mice were treated with CT-112 from either the time of immunization with type II collagen or from the initial onset of arthritis. RESULTS: CT-112 both prevented the development of arthritis in mice treated prophylactically and reduced progression of disease in animals treated therapeutically, and was active when delivered by either subcutaneous injection or oral gavage. No marked immunosuppressive effects were observed during CT-112 treatment, with only moderate decrease in antibody levels and mitogen responses. A significant reduction of the circulating levels of IL-1 was a consistent finding in mice treated therapeutically with CT-112. CONCLUSION: These data suggest PF-4 derived octapeptide exerts antiinflammatory effects of experimental arthritis in mice. 相似文献
135.
Oxygen mass transfer calculations in large arteries 总被引:1,自引:0,他引:1
Parkinsonism is characterised by overactive glutamatergic transmission in the cortico-striatal and subthalamo-medial pallidal pathways. Local blockade of glutamatergic transmission in these pathways can alleviate parkinsonian symptoms. The effectiveness of the treatment, however, is often limited by the simultaneous appearance of unwanted side-effects. These side-effects, including ataxia and dissociative anaesthesia, are particularly problematic when N-methyl-D-aspartate (NMDA) antagonists are used. In an attempt to overcome these problems we have attempted to manipulate excitatory amino acid (EAA)-mediated neurotransmission indirectly by targeting the NMDA receptor associated modulatory sites. We review evidence which demonstrates that antagonists for both the NMDA associated glycine and polyamine sites can reverse parkinsonian symptoms when injected intra-cerebrally in both MPTP-treated and bilateral 6-OHDA lesioned marmosets without eliciting unwanted side-effects. We further review preliminary data which suggest that ifenprodil, a polyamine site antagonist, has striking anti-parkinsonian actions in the marmoset. Potential mechanisms of action underlying these effects are discussed in terms of NMDA receptor subtypes and the neuroanatomical locus of action. The anti-parkinsonian efficacy of intra-striatally administered EAA antagonists leads us to question the view of dopamine acting in the striatum as a simple neuromodulator. 相似文献
136.
Detecting Deception in Children: Event Familiarity Affects Criterion-Based Content Analysis Ratings.
137.
138.
139.
140.
OBJECTIVE: The relationship between intentions to use alcohol and risk factors was examined among fifth and sixth graders. METHOD: Subjects completed a questionnaire that assessed intentions to use alcohol and eight risk factors. Risk factors included peer and parental use and attitudes toward use, sensation seeking, tolerance of deviance, rejection of parental authority, and family cohesion. RESULTS: Multivariate analyses showed that the risk factors were able to discriminate between those who intended to use alcohol and those who did not. Family factors showed stronger relationships to intentions among fifth graders, and peer factors were more strongly related to intentions among sixth graders. CONCLUSIONS: Risk factors can be used to target preadolescents who may be at risk for early alcohol use, and programs that attempt to prevent early initiation of alcohol use among adolescents can be designed. 相似文献