全文获取类型
收费全文 | 46080篇 |
免费 | 634篇 |
国内免费 | 792篇 |
专业分类
电工技术 | 774篇 |
综合类 | 52篇 |
化学工业 | 6916篇 |
金属工艺 | 3163篇 |
机械仪表 | 1450篇 |
建筑科学 | 985篇 |
矿业工程 | 155篇 |
能源动力 | 1518篇 |
轻工业 | 2539篇 |
水利工程 | 377篇 |
石油天然气 | 1389篇 |
无线电 | 4329篇 |
一般工业技术 | 11274篇 |
冶金工业 | 8387篇 |
原子能技术 | 834篇 |
自动化技术 | 3364篇 |
出版年
2021年 | 367篇 |
2020年 | 297篇 |
2019年 | 406篇 |
2018年 | 709篇 |
2017年 | 705篇 |
2016年 | 776篇 |
2015年 | 576篇 |
2014年 | 880篇 |
2013年 | 2568篇 |
2012年 | 1479篇 |
2011年 | 2002篇 |
2010年 | 1590篇 |
2009年 | 1881篇 |
2008年 | 1734篇 |
2007年 | 1889篇 |
2006年 | 1490篇 |
2005年 | 1307篇 |
2004年 | 1260篇 |
2003年 | 1170篇 |
2002年 | 1152篇 |
2001年 | 1209篇 |
2000年 | 1049篇 |
1999年 | 1094篇 |
1998年 | 2441篇 |
1997年 | 1847篇 |
1996年 | 1597篇 |
1995年 | 1090篇 |
1994年 | 856篇 |
1993年 | 871篇 |
1992年 | 652篇 |
1991年 | 626篇 |
1990年 | 575篇 |
1989年 | 543篇 |
1988年 | 424篇 |
1987年 | 454篇 |
1986年 | 399篇 |
1985年 | 426篇 |
1984年 | 366篇 |
1983年 | 353篇 |
1982年 | 345篇 |
1981年 | 345篇 |
1980年 | 401篇 |
1979年 | 397篇 |
1978年 | 336篇 |
1977年 | 471篇 |
1976年 | 722篇 |
1975年 | 349篇 |
1974年 | 325篇 |
1973年 | 332篇 |
1972年 | 296篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
R Lewis 《Canadian Metallurgical Quarterly》1998,24(3):95-97
The management of pain in patients with burn wounds is complex and problematic. Burn-wound pain is severe, inconsistent and underestimated. Patients experience severe pain, especially during procedures, until wound healing has occurred. A multi-modality approach is needed for effective management of pain, which requires an understanding of the mechanisms of pain. Altered pharmacokinetics and pharmacodynamics in burn-wound patients makes drug actions unpredictable. Opioids alone are seldom sufficient for pain control. The multi-modality approach includes the use of opioids and non-steroidal anti-inflammatory, anxiolytic and alternative drugs. Ketamine has been found to be a useful agent for analgesia in burn-wound patients; a dose of 10 mg/kg qid per os was found to be an effective adjunct to pain therapy. 相似文献
92.
Network management in large heterogeneous communication environments requires the incorporation of more advanced tools than are currently available, especially in the area of fault management. By providing an informational infrastructure for documenting network behavior and maintenance activities, TTSs (trouble ticket systems) have provided some relief for the fault management problem. Researchers have recognized TTSs as a means for realizing more advanced functions in network management platforms to effect automatic trouble ticket generation, fault diagnostics, and the correlation of multiple views network problems and behavior. The authors describe current research trends towards understanding and implementing these advanced functions in a TTS framework 相似文献
93.
94.
The purpose of this study was to evaluate the changes in condylar position following bilateral sagittal split ramus osteotomy with 5- and 10-mm setback in 1 symmetric human cadaver mandibles. A Plexiglas device was constructed to determine the mandibular morphology and the movements of the condyle and the proximal segments before and after surgery. There was no statistically significant relationship between mandibular morphology or the magnitude of setback and changes in condylar position postsurgery. All condyles and rami tipped in a highly variable fashion in the coronal plane. In the axial plane, the lateral pole of the condyles rotated predominantly anteriorly; the left side rotated significantly more than did the right. In the sample studied, the position of the condylar and proximal segments was altered in a highly variable and unpredictable manner, regardless of the magnitude of setback or the morphology of the mandible. 相似文献
95.
The main maturation stages of Norway rat megakaryocytic series, megakaryoblasts and mature megakaryocytes, stained by silver for demonstration of argyrophil nucleolus organizer regions (AgNORs) were investigated to provide basic information on the number of nucleoli and interphasic AgNORs in these cells. The results showed that megakaryoblasts as well as mature megakaryocytes possess numerous nucleoli; their number and also the number of AgNORs is significantly higher in less mature than in more mature cells. The number of AgNORs in megakaryocytes of the Norway rat and man are virtually the same, although the numbers of nucleolar organizers per haploid chromosome set differ markedly. This fact leads to the conclusion that the number of interphasic AgNORs depends on the function and metabolic state of the cell rather than on the number of nucleolar organizers. 相似文献
96.
BMP is one of important factors in the pathophysiology of bone regeneration. Fifteen New Zealand rabbits were used in this experiment. We studied the distribution and effectiveness of endogenic BMP on a 10 mm bone defect of radius, by utilizing immunohistochemistry of BMP and quantitative computer imaging system. On the 3rd day, death of osteocytes and BMP positive blood clot were observed. The mesenchymal cells from periosteum and endoosteum, and osteoblast were also BMP positive. By quantitative study, we found there was a gradient distribution of BMP in bone defect, i.e, the value of BMP decreased gradually along the distance from the fracture ends. The maximal value of BMP was noted at the 1st week postoperation. In conclusion, two sources of endogenic BMP were found, one was from the absorption of necrotic tissue of fracture ends, the other was from the secretion of osteogenic mesenchymal cells during the process of bone regeneration. Nonunion of bone defect was caused in part by the gradient distribution of BMP. Accordingly, the concept of effective quantity of endogenic BMP was drawn rosen. It might be a new method in the treatment of bone defect by increasing the concentration of endogenic BMP and improving its distribution. 相似文献
97.
MS Harbuz Z Perveen-Gill SL Lightman DS Jessop 《Canadian Metallurgical Quarterly》1995,34(12):1117-1122
We have investigated the role of the gonadal steroids testosterone (T) and progesterone in modulating: (1) the onset and severity of adjuvant-induced arthritis (AA), (2) the response of the hypothalamo-pituitary-adrenal (HPA) axis, and (3) the levels of plasma prolactin and anterior pituitary prolactin messenger ribonucleic acid (mRNA) in the rat. Male rats were castrated (CSX) and received either no T, low T or high T delivered using silastic implants. In a second study experimental groups comprised CSX/AA, CSX/AA + progesterone or CSX/AA + progesterone + T. The time of onset was sooner and the severity of AA was greater in CSX rats. Inflammation was prevented by T replacement. Endogenous plasma T levels were decreased in AA rats. In control animals with AA there was an increase in pro-opiomelanocortin (POMC) mRNA in the anterior pituitary and of plasma corticosterone, and a decrease in corticotrophin-releasing factor (CRF) mRNA. These changes in the HPA axis of AA and CSX/AA rats were reversed by T replacement. These data suggest that T has an important protective effect on the progress and severity of AA. This was reflected by a reversal of the neuroendocrine changes of the HPA axis. Progesterone treatment alone had no effect on the severity of the disease. Prolactin mRNA in the anterior pituitary was decreased in the CSX and in the CSX/AA group but was not altered by AA. Plasma prolactin was raised in AA but T replacement did not reduce these elevated levels despite the absence of disease. Thus, prolactin provides a poor indicator of inflammation, suggesting that it may not be a potent pro-inflammatory compound in AA. 相似文献
98.
99.
100.
Of 1,666 patients who underwent fine needle aspiration for breast lumps, 4 developed pneumothorax as a complication. The incidence of this complication in our patients is 1:417. The clinical manifestations were immediate chest pain, shoulder pain and, occasionally, dyspnea that developed later. Observation is sufficient treatment in most patients, and rarely is drainage of the pneumothorax required. 相似文献