首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2945篇
  免费   125篇
  国内免费   2篇
电工技术   12篇
综合类   1篇
化学工业   578篇
金属工艺   39篇
机械仪表   37篇
建筑科学   151篇
矿业工程   5篇
能源动力   69篇
轻工业   341篇
水利工程   23篇
石油天然气   5篇
无线电   167篇
一般工业技术   413篇
冶金工业   937篇
原子能技术   4篇
自动化技术   290篇
  2023年   19篇
  2022年   68篇
  2021年   78篇
  2020年   39篇
  2019年   47篇
  2018年   68篇
  2017年   65篇
  2016年   50篇
  2015年   59篇
  2014年   66篇
  2013年   148篇
  2012年   131篇
  2011年   177篇
  2010年   125篇
  2009年   149篇
  2008年   136篇
  2007年   141篇
  2006年   131篇
  2005年   120篇
  2004年   99篇
  2003年   82篇
  2002年   104篇
  2001年   51篇
  2000年   61篇
  1999年   68篇
  1998年   56篇
  1997年   50篇
  1996年   73篇
  1995年   52篇
  1994年   52篇
  1993年   47篇
  1992年   46篇
  1991年   14篇
  1990年   34篇
  1989年   38篇
  1988年   31篇
  1987年   32篇
  1986年   32篇
  1985年   22篇
  1984年   32篇
  1983年   25篇
  1982年   27篇
  1981年   24篇
  1980年   15篇
  1979年   13篇
  1978年   10篇
  1977年   9篇
  1976年   13篇
  1975年   9篇
  1974年   8篇
排序方式: 共有3072条查询结果,搜索用时 0 毫秒
91.
Eighty clients enrolled in a managed care health plan who identified panic disorder as their primary presenting problem were randomly assigned to treatment by a therapist recently trained in a manual-based empirically supported psychotherapy (M. G. Craske, E. Meadows, & D. H. Barlow, 1994) or a therapist conducting treatment as usual (TAU). Participants in both conditions showed significant change from pre- to posttreatment on a number of measures. Those receiving panic control therapy (PCT) showed greater levels of change than those receiving TAU. Among treatment completers, an average of 42.9% of those in PCT and 18.8% in TAU achieved clinically significant change across measures. The results are discussed with reference to the dissemination of PCT and other evidence-based psychotherapies to clinical practice settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
92.
随着环保意识的不断提高和环保法规的逐步完善.涂料行业时VOC(挥发性有机化合物)和HMPs(有害物质)的控制进一步严格。我国现行的强制性国家标准中,内墙乳胶漆VOC含量要不超过200g/L,如果要获得绿色环保“十环标志”,则VOC的含量要低于100克g/L。2007年1月1日起.欧盟国家实施新的漆类标准中,要求每升水性漆VOC含量应低于100g.溶剂性漆的VOC含量应低于每升400g。涂料的水性化趋势越来越明显,水性涂料占据了越来越大的市场份额。 水性涂料以水为分散介质并富含各种可被微生物作为营养利用的添加剂.为微生物的生长繁殖提供了条件。当细菌、霉菌和酵母菌等微生物污染涂料后大量繁殖会导致涂料产生表面色变、pH值变化、使用性能变化、凝聚以及产生异味等一系列问题,从而使涂料产品失去价值造成巨大损失。随着水性涂料的广泛应用.控制微生物生长和繁殖从而避免涂料被污染.时于保证涂料产品的品质和使用效果是非常重要的。  相似文献   
93.
Aphids (Hemiptera: Aphidoidea) are among the most detrimental insects for agricultural plants, and their management is a great challenge in agronomical research. A new class of proteins, called Bacteriocyte-specific Cysteine-Rich (BCR) peptides, provides an alternative to chemical insecticides for pest control. BCRs were initially identified in the pea aphid Acyrthosiphon pisum. They are small disulfide bond-rich proteins expressed exclusively in aphid bacteriocytes, the insect cells that host intracellular symbiotic bacteria. Here, we show that one of the A. pisum BCRs, BCR4, displays prominent insecticidal activity against the pea aphid, impairing insect survival and nymphal growth, providing evidence for its potential use as a new biopesticide. Our comparative genomics and phylogenetic analyses indicate that BCRs are restricted to the aphid lineage. The 3D structure of BCR4 reveals that this peptide belongs to an as-yet-unknown structural class of peptides and defines a new superfamily of defensins.  相似文献   
94.
TBI induces splenic B and T cell expansion that contributes to neuroinflammation and neurodegeneration. The vagus nerve, the longest of the cranial nerves, is the predominant parasympathetic pathway allowing the central nervous system (CNS) control over peripheral organs, including regulation of inflammatory responses. One way this is accomplished is by vagus innervation of the celiac ganglion, from which the splenic nerve innervates the spleen. This splenic innervation enables modulation of the splenic immune response, including splenocyte selection, activation, and downstream signaling. Considering that the left and right vagus nerves have distinct courses, it is possible that they differentially influence the splenic immune response following a CNS injury. To test this possibility, immune cell subsets were profiled and quantified following either a left or a right unilateral vagotomy. Both unilateral vagotomies caused similar effects with respect to the percentage of B cells and in the decreased percentage of macrophages and T cells following vagotomy. We next tested the hypothesis that a left unilateral vagotomy would modulate the splenic immune response to a traumatic brain injury (TBI). Mice received a left cervical vagotomy or a sham vagotomy 3 days prior to a fluid percussion injury (FPI), a well-characterized mouse model of TBI that consistently elicits an immune and neuroimmune response. Flow cytometric analysis showed that vagotomy prior to FPI resulted in fewer CLIP+ B cells, and CD4+, CD25+, and CD8+ T cells. Vagotomy followed by FPI also resulted in an altered distribution of CD11bhigh and CD11blow macrophages. Thus, transduction of immune signals from the CNS to the periphery via the vagus nerve can be targeted to modulate the immune response following TBI.  相似文献   
95.
96.
Research suggests that presurgical personality attributes influence postsurgical well-being in both patients and their spouses in the context of coronary artery bypass grafting (CABG) surgery. The authors hypothesized that a spouse's characteristics would influence a partner's psychological well-being, regardless of whether he or she was the patient or the caregiver. In this study, 111 male patients and their caregiver spouses completed measures of neuroticism, optimism, perceived marital satisfaction, and depression prior to elective CABG. Follow-up was conducted at 18 months. As expected, higher caregiver presurgical neuroticism predicted higher patient depressive symptoms at follow-up, with caregiver's concurrent 18-month affect controlled for. Likewise, higher patient presurgical neuroticism predicted higher caregiver depressive symptoms at follow-up. Additionally, higher patient presurgical depressive symptoms and lower presurgical optimism contributed to greater caregiving burden. Relationship satisfaction moderated these effects. These results suggest that partners' personality traits are important determinants of both patients' and their caregiving spouses' well-being. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
97.
98.
Foodborne outbreaks are detected by recognition of similar illnesses among persons with a common exposure or by identification of case clusters through pathogen-specific surveillance. PulseNet USA has created a national framework for pathogen-specific surveillance, but no comparable effort has been made to improve surveillance of consumer complaints of suspected foodborne illness. The purpose of this study was to characterize the complaint surveillance system in Minnesota and to evaluate its use for detecting outbreaks. Minnesota Department of Health foodborne illness surveillance data from 2000 through 2006 were analyzed for this study. During this period, consumer complaint surveillance led to detection of 79% of confirmed foodborne outbreaks. Most norovirus infection outbreaks were detected through complaints. Complaint surveillance also directly led or contributed to detection of 25% of salmonellosis outbreaks. Eighty-one percent of complainants did not seek medical attention. The number of ill persons in a complainant's party was significantly associated with a complaint ultimately resulting in identification of a foodborne outbreak. Outbreak confirmation was related to a complainant's ability to identify a common exposure and was likely related to the process by which the Minnesota Department of Health chooses complaints to investigate. A significant difference (P < 0.001) was found in incubation periods between complaints that were outbreak associated (median, 27 h) and those that were not outbreak associated (median, 6 h). Complaint systems can be used to detect outbreaks caused by a variety of pathogens. Case detection for foodborne disease surveillance in Minnesota happens through a multitude of mechanisms. The ability to integrate these mechanisms and carry out rapid investigations leads to improved outbreak detection.  相似文献   
99.
The effect of 0, 50, 100 and 200 μg/ml of nitrite on the growth of isolated and reference strains of lactic acid bacteria associated with cured meat products was studied in broth cultures and the presence of an active nitrite reductase enzyme system in these strains was determined. Half of the 10 reference strains and 16 of 25 isolated strains were resistant to all levels of nitrite tested Strains which did not show a significant decrease in growth rate or cell yield in the presence of 200 μg/ml of nitrite under anaerobic conditions were homofermentative. All heterofermentative strains showed a decrease in growth rate or cell yield or both. Inhibition due to nitrite increased as the concentration increased and was greatest under anaerobic conditions. Enzymatic ability to reduce nitrite was detected in 5 homofermentative and 1 heterofermentative strains. The presence of an active nitrite reductase enzyme system in lactic acid bacteria was not related to their resistance to nitrite.  相似文献   
100.
Alport syndrome (AS) is a hereditary renal disorder with no etiological therapy. In the preclinical Col4a3-/- model of AS, disease progression and severity vary depending on mouse strain. The sodium-glucose cotransporter 2 (SGLT2) is emerging as an attractive therapeutic target in cardiac/renal pathologies, but its application to AS remains untested. This study investigates cardiorespiratory function and SGLT2 renal expression in Col4a3-/- mice from three different genetic backgrounds, 129x1/SvJ, C57Bl/6 and Balb/C. male Col4a3-/- 129x1/SvJ mice displayed alterations consistent with heart failure with preserved ejection fraction (HFpEF). Female, but not male, C57Bl/6 and Balb/C Col4a3-/- mice exhibited mild changes in systolic and diastolic function of the heart by echocardiography. Male C57Bl/6 Col4a3-/- mice presented systolic dysfunction by invasive hemodynamic analysis. All strains except Balb/C males demonstrated alterations in respiratory function. SGLT2 expression was significantly increased in AS compared to WT mice from all strains. However, cardiorespiratory abnormalities and SGLT2 over-expression were significantly less in AS Balb/C mice compared to the other two strains. Systolic blood pressure was significantly elevated only in mutant 129x1/SvJ mice. The results provide further evidence for strain-dependent cardiorespiratory and hypertensive phenotype variations in mouse AS models, corroborated by renal SGLT2 expression, and support ongoing initiatives to develop SGLT2 inhibitors for the treatment of AS.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号