全文获取类型
收费全文 | 6837篇 |
免费 | 30篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 30篇 |
化学工业 | 325篇 |
金属工艺 | 26篇 |
机械仪表 | 35篇 |
建筑科学 | 118篇 |
矿业工程 | 6篇 |
能源动力 | 48篇 |
轻工业 | 245篇 |
水利工程 | 42篇 |
石油天然气 | 12篇 |
无线电 | 177篇 |
一般工业技术 | 312篇 |
冶金工业 | 5122篇 |
原子能技术 | 25篇 |
自动化技术 | 345篇 |
出版年
2022年 | 16篇 |
2021年 | 17篇 |
2019年 | 22篇 |
2018年 | 22篇 |
2017年 | 19篇 |
2016年 | 28篇 |
2015年 | 22篇 |
2014年 | 40篇 |
2013年 | 107篇 |
2012年 | 71篇 |
2011年 | 84篇 |
2010年 | 64篇 |
2009年 | 91篇 |
2008年 | 84篇 |
2007年 | 86篇 |
2006年 | 81篇 |
2005年 | 60篇 |
2004年 | 75篇 |
2003年 | 81篇 |
2002年 | 58篇 |
2001年 | 63篇 |
2000年 | 53篇 |
1999年 | 180篇 |
1998年 | 1521篇 |
1997年 | 864篇 |
1996年 | 577篇 |
1995年 | 358篇 |
1994年 | 259篇 |
1993年 | 339篇 |
1992年 | 86篇 |
1991年 | 83篇 |
1990年 | 92篇 |
1989年 | 104篇 |
1988年 | 88篇 |
1987年 | 96篇 |
1986年 | 70篇 |
1985年 | 86篇 |
1984年 | 36篇 |
1983年 | 38篇 |
1982年 | 46篇 |
1981年 | 53篇 |
1980年 | 45篇 |
1979年 | 18篇 |
1978年 | 19篇 |
1977年 | 138篇 |
1976年 | 270篇 |
1975年 | 24篇 |
1974年 | 18篇 |
1973年 | 21篇 |
1972年 | 15篇 |
排序方式: 共有6868条查询结果,搜索用时 0 毫秒
151.
SJ Raphael JD Macaulay C Miller J Thomas SL Asa 《Canadian Metallurgical Quarterly》1993,24(9):1023-1025
"Hyperlipidemic crisis" is a term used to describe episodic abdominal pain in patients with hyperlipidemia. The morphologic correlates of this phenomenon have not been investigated and the etiology of the disorder is uncertain. We report a unique histologic finding in the pancreas of a 34-year-old woman with a 17-year history of episodic abdominal pain, sometimes accompanied by hyperamylasemia. At the age of 18 years, grossly elevated cholesterol and triglyceride levels were documented and type V hyperlipidemia was diagnosed. At the age of 34 years, subtotal pancreatectomy was performed for intractable abdominal pain. Histologic examination identified an increased number of enlarged pancreatic nerves that were infiltrated by foamy macrophages and encircled by fibrous tissue; endoneurial infiltration with macrophages occasionally split nerves into individual fascicles. Otherwise, the pancreas had only minimal fibrosis, nesidioblastosis, mucinous metaplasia of some pancreatic ducts, and scattered small collections of chronic inflammatory cells, subtle features suggesting very mild chronic pancreatitis. We propose that this novel xanthomatous neuropathy mimicked pancreatitis and was one of the underlying pathophysiologic mechanisms of abdominal pain in this patient. Further studies are necessary to document the prevalence of this new entity in patients with hyperlipidemia and to correlate its occurrence with "hyperlipidemic crisis" in those individuals. 相似文献
152.
FM Stewart 《Canadian Metallurgical Quarterly》1993,7(7):1091-1094
High dose chemotherapy with or without total body irradiation and autologous stem cell rescue has proven to be effective treatment to cure patients with relapsed intermediate grade and high grade non-Hodgkin's lymphoma. Important factors for selection of candidates most likely to do well with these approaches include patients whose disease is responsive to conventional therapy and those who have minimal disease volume at the time of transplant. The treatment-related mortality of autologous stem cell transplantation has diminished from 20% to less than 5% with improved supportive care and selection of patients with less advanced disease. Although the treatment-related mortality of allogeneic stem cell transplantation may be as high as 20-40%, a graft versus lymphoma effect may decrease relapse with the result that overall survival is not substantially different between autologous and allogeneic transplantation. The definitive indications for stem cell transplantation include patients who have relapsed with intermediate or high grade NHL. Relative indications include intermediate/high grade non-Hodgkin's lymphoma patients, "high risk" first complete remission (CR), resistant relapse; low grade non-Hodgkin's lymphoma in sensitive or resistant relapse, advanced disease (sensitive or resistant relapse, transformation), first CR (younger patients). Relative contraindications include specific patient profiles such as bulky high grade lymphoma which progresses on appropriate conventional therapy, poor performance status, active serious infection, serious cardiac, renal, pulmonary or liver dysfunction, active, central nervous system (CNS) disease unresponsive to cranial irradiation/intrathecal therapy. For patients with previous marrow involvement or active marrow involvement at the time of harvest or transplant, "purged" autografts, peripheral blood stem cell transplantation and allografts have been used successfully. 相似文献
153.
This paper describes the implementation and evaluation of a nonsanction seat belt law enforcement program in two experimental communities of contrasting size in a state with a mandatory belt law. The main ingredients of the program were seat belt "salutes," public information and education, and limited use of inexpensive economic incentives. Driver shoulder belt use data collected before, during, and after the experimental programs, compared to similar data collected in a comparison community, showed the approach to be effective. While standard seat belt enforcement activities without incentives have been shown to be effective, many police departments, especially in smaller communities, are reluctant to make wholesale increases in seat belt citations. Although requiring some additional level of manpower and resources, a nonsanction approach to seat belt law enforcement can provide an alternate way of increasing belt use in these communities. 相似文献
154.
Specific heat measurements on superconductingLu
2
Fe
3
Si
5
reveal a strong sample dependence of the residual specific heat contribution
s
, belowT
c
, effectively ruling out the possibility of a two-band model. Upper critical fieldH
c2
results for Lu2Fe3Si5, Sc2Fe3Si5, and LaFe4P12 show a very largeH
c2 with an unusual temperature dependence for Lu2Fe3Si5, in contrast to the latter two compounds, implying a strongly sample-dependentH
c2 as well. Intrinsic magnetic impurities arising from structural disorder and defects are possibly the origin of these anomalous superconducting state properties of Lu2Fe3Si5. 相似文献
155.
Eric R. Smith Richard J. Radke Charles V. Stewart 《International Journal of Computer Vision》2012,97(1):2-17
We present a new framework for detecting, describing, and matching keypoints in combined range-intensity data, resulting in
what we call physical scale keypoints. We first produce an image mesh by backprojecting associated 2D intensity images onto
the 3D range data. We detect and describe keypoints on the image mesh using an analogue of the SIFT algorithm for images with
two key modifications: the process is made insensitive to viewpoint and structural discontinuities using a novel bilinear
filter, and a physical scale space is constructed that exploits the reliable range measurements. Keypoints are matched between
scans only when their physical scales agree, avoiding many potential false matches. Finally, the matches are rank-ordered
using a new quality measure and supplied to a registration algorithm that refines each match into a rigid transformation for
the entire scan pair. We report experimental results on keypoint detection and matching and range scan registration and verification
in a set of difficult real-world scan pairs, showing that the new physical scale keypoints are demonstrably better than a
competing approach based on backprojected SIFT keypoints. 相似文献
156.
JA Frank RE Hoffman JM Mann JD Crowe AR Hinman 《Canadian Metallurgical Quarterly》1981,245(3):264-266
From Dec 23, 1978, through Jan 31, 1979, an outbreak of five laboratory-confirmed cases and four clinical cases of measles occurred in a Vietnamese refugee population living in a single housing complex in Albuquerque, NM. The index cases were in two refugee siblings in whom measles was incubating on arrival in the United States. Despite spread through three subsequent generations of disease transmission within the Vietnamese population, there was no additional spread into the general Albuquerque population. Responsible factors included the age distribution of susceptible persons, the social isolation of the refugee population, and the physical structure of the housing complex. There is a need to identify the problem of imported measles in "ethnic islands" in need of vaccination. 相似文献
157.
The validation of otological care in the previous quarter century has been based, by and large, on short-term follow-up information. The rapid variation in procedures introduced during this period indicates that there may be need for further consideration. Analyses based on relatively short duration have led the "acceptance" of a variety of diagnostic and treatment methods which have proven disappointing in some cases. To help avoid this invalid "acceptance," a review of patients with significant follow-up may result in a more critical evaluation of future procedural changes. This presentation will be in four parts: 1. History of the office structure. 2. Discussion of five long-term patients that illustrates and supports certain otological concepts. 3. A review of surgical care for chronic suppurative otitis media in 1968. 4. A review of patients treated for serous otitis media with myringotomy and tubal insertion in 1968. 相似文献
158.
Sodium nitroprusside is a potent, effective, and readily reversible direct vasodilating agent. It is broken down by hemoglobin into cyanide, which is in part detoxified by liver and kidney to thiocyanate. Some cyanide, especially in nitroprusside- "resistant" individuals who need large amounts of the drug, appears to remain free to cause cyanide poisoning. Patients requiring inordinate amounts probably should not continue to receive the drug, although maximum dosage limits for long-term therapy are not established. Blood thiocyanate levels do not indicate the extent to which free cyanide is limiting oxygen utilization in essential tissue, nor do blood cyanide levels. Metabolic acidosis, elevated lactate levels, elevated lactate/pyruvate ratios, and elevated mixed venous blood oxygen content are at present the best indications of the presence of cyanide poisoning during nitroprusside administration. Nitroprusside appears useful for induction of hypotension during surgery, and for treatment of hypertensive emergencies from all causes, although continuance for more than a few days is probably unwise. The reductions of cardiac afterload and ventricular filling pressure by nitroprusside appear useful in treatment of severe myocardial failure or infarction, but studies of myocardial cyanide toxicity are needed before complete acceptance of this therapy is warranted. Initial dose rates between 0.5 and 1.5 mug/kg/min are recommended only as starting points for very careful titration. Total projected intra-operative dosage should be calculated as quickly as possible and should not exceed 3-3.5 mg/kg. It is hoped that future studies will reveal the maximum dose of nitroprusside that can safely be metabolized in a 24-hour period, and may indicate that cofactors of rhodanase such as thiosulfate, or cobalamins such as hydroxocobalamin, can be administered with nitroprusside to prevent cyanide poisoning. 相似文献
159.
Gump Brooks B.; Reihman Jacki; Stewart Paul; Lonky Ed; Darvill Tom 《Canadian Metallurgical Quarterly》2005,24(6):594
A number of studies have considered whether background stress affects cardiovascular responses to acute stress tasks. The present study considers the effect of a potent background stressor with a clear onset, namely the terrorist attacks on September 11, 2001. Specifically, the authors investigated differences among 9.5-year-old children tested before (N = 30) and then following (N = 20) the 9/11 attacks. In addition, a majority of these children (N = 37) were retested approximately 1 year later (i.e., before and after 9/11/2002). Children tested directly following 9/11/2001 exhibited significantly greater stroke volume and cardiac output responses to acute stress tasks compared with their responses 1 year later, and this change in reactivity differed significantly from the change in reactivity exhibited by children tested before 9/11/2001 and again 1 year later. These results suggest that a potent background stressor can temporarily heighten some children's cardiovascular responses to subsequent acute stressors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
160.
Ferrer Emilio; Salthouse Timothy A.; McArdle John J.; Stewart Walter F.; Schwartz Brian S. 《Canadian Metallurgical Quarterly》2005,20(3):412
Longitudinal multivariate mixed models were used to examine the correlates of change between memory and processing speed and the contribution of age and retest to such change correlates. Various age- and occasion-mixed models were fitted to 2 longitudinal data sets of adult individuals (N > 1,200). For both data sets, the results indicated that the correlation between the age slopes of memory and processing speed decreased when retest effects were included in the model. If retest effects existed in the data but were not modeled, the correlation between the age slopes was positively biased. The authors suggest that although the changes in memory and processing speed may be correlated over time, age alone does not capture such a covariation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献