全文获取类型
收费全文 | 9395篇 |
免费 | 108篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 138篇 |
综合类 | 3篇 |
化学工业 | 836篇 |
金属工艺 | 109篇 |
机械仪表 | 139篇 |
建筑科学 | 164篇 |
矿业工程 | 32篇 |
能源动力 | 104篇 |
轻工业 | 689篇 |
水利工程 | 42篇 |
石油天然气 | 21篇 |
无线电 | 794篇 |
一般工业技术 | 983篇 |
冶金工业 | 4626篇 |
原子能技术 | 109篇 |
自动化技术 | 715篇 |
出版年
2021年 | 47篇 |
2019年 | 45篇 |
2018年 | 51篇 |
2017年 | 56篇 |
2016年 | 73篇 |
2015年 | 51篇 |
2014年 | 82篇 |
2013年 | 184篇 |
2012年 | 164篇 |
2011年 | 228篇 |
2010年 | 194篇 |
2009年 | 206篇 |
2008年 | 227篇 |
2007年 | 232篇 |
2006年 | 199篇 |
2005年 | 202篇 |
2004年 | 185篇 |
2003年 | 163篇 |
2002年 | 142篇 |
2001年 | 148篇 |
2000年 | 163篇 |
1999年 | 243篇 |
1998年 | 1193篇 |
1997年 | 731篇 |
1996年 | 545篇 |
1995年 | 331篇 |
1994年 | 284篇 |
1993年 | 371篇 |
1992年 | 157篇 |
1991年 | 156篇 |
1990年 | 149篇 |
1989年 | 177篇 |
1988年 | 166篇 |
1987年 | 136篇 |
1986年 | 163篇 |
1985年 | 139篇 |
1984年 | 85篇 |
1983年 | 90篇 |
1982年 | 87篇 |
1981年 | 73篇 |
1980年 | 78篇 |
1979年 | 78篇 |
1978年 | 81篇 |
1977年 | 147篇 |
1976年 | 260篇 |
1975年 | 60篇 |
1974年 | 56篇 |
1973年 | 53篇 |
1972年 | 37篇 |
1971年 | 36篇 |
排序方式: 共有9504条查询结果,搜索用时 26 毫秒
991.
992.
RS Miller DA Weatherford D Stein MM Crane M Stein 《Canadian Metallurgical Quarterly》1994,37(3):442-445
Using capillary videomicroscopy of the nail fold, the frequency of cold-induced vasospasm and capillary hemodynamic parameters were studied after application of cold in 50 patients with primary fibromyalgia, 50 patients with chronic low back pain, and 50 healthy controls. Cold-induced vasospasm was detected in 38% of the patients with fibromyalgia. In this group it was significantly more frequent than in the patients with chronic low back pain (20%, p < 0.05) and healthy subjects (8%, p < 0.001). In the fibromyalgia group, the magnitude of vasospasm as measured by the capillary blood flow deceleration after cold application correlated negatively with the pain intensity as measured by pain score (r = -0.3839, p < 0.01). No differences in clinical appearance were found between patients with and without cold-induced vasospasm in both the fibromyalgia and low back pain group. 相似文献
993.
J Petraitis BR Flay TQ Miller EJ Torpy B Greiner 《Canadian Metallurgical Quarterly》1998,33(13):2561-2604
This paper reviews findings from 58 prospective studies of illicit substance use (ISU) among adolescents. It arranges 384 findings according to three types of influence (viz., social, attitudinal, and intrapersonal) and four levels of influence (viz., ultimate, distal, proximal, and immediate). The bulk of evidence reconfirms the importance of several predictors of ISU (e.g., intentions and prior substance-related behavior, friendship patterns and peer behaviors, absence of supportive parents, psychological temperament), reveals that a few variables thought to be well-established predictors may not be (e.g., parental behaviors, parental permissiveness, depression, low self-esteem), and uncovers several variables where findings were either sparse or inconsistent (e.g., the role of public policies concerning ISU, mass media depictions of ISU, certain parenting styles, affective states, perceptions of parental disapproval for ISU, and substance-specific refusal skills). Directions for future research are discussed. 相似文献
994.
DP Pope AJ Silman NM Cherry C Pritchard GJ Macfarlane 《Canadian Metallurgical Quarterly》1998,24(5):376-385
The aim of this study was to compare the results of open retropubic (OC) and laparoscopic (LC) colposuspension to the Cooper's ligament (Burch operation). We matched retrospectively 72 LC and OC according to their ages, the type of associated operations and the clinical stages of their urinary incontinence. We excluded associated prolapsus, previous surgical procedure for urinary incontinence, maximal urethral closure pressure lower than 30 cms of water and instability of the detrusor. We estimated the comparability of our two series about the other criteria which have an effect upon the post operative results in literature. The mean follow up was 17 months for LC and 46 months for OC. LC operative time was longer than (Mean: LC: 89 minutes, OC: 42 minutes), women considered LC less aching than OC. They needed less postoperative analgesia, mostly given only just the day of the procedure. LC length of hospitalization and return to normal activity was shorter than OC (Mean: LC: 3 days--OC: 6, 7 days; LC: 15 days--OC: 21 days). The graphs of the subjective cure and improvement rates made according to the Kaplan-Meier method could be compared with the log rank test. (Cure after one year: LC 79%, OC 69%--Improvement after one year: LC 85%, OC 82%--Cure after two years: LC 68%--OC 64%--Improvement after two years: LC 80%--OC 75%). 相似文献
995.
C Brown L Wiklund G Bar-Joseph B Miller N Bircher N Paradis J Menegazzi M von Planta GC Kramer SE Gisvold 《Canadian Metallurgical Quarterly》1996,33(2):163-177
The topics discussed in this session include a partial review of laboratory and clinical studies examining the effects of adrenergic agonists on restoration of spontaneous circulation after cardiac arrest, the effects of varying doses of epinephrine, and the effects of novel vasopressors, buffer agents (NaHCO3, THAM, 'Carbicarb') and anti-arrhythmics (lidocaine, bretylium, amiodarone) in refractory ventricular fibrillation. Novel therapeutic approaches include titrating electric countershocks against electrocardiographic power spectra and of preceding the first countershocks with single or multiple drug treatments. These approaches need to be investigated further in controlled animal and patient studies. Epidemiologic data from randomized clinical outcome studies can give clues, but cannot document pharmacologic mechanisms in the dynamically changing events during attempts to achieve restoration of spontaneous circulation from prolonged cardiac arrest. Also, rapid drug administration by the intraosseous route was compared with intratracheal and intravenous (i.v.) drug administration. Many studies on the above treatments have yielded conflicting results because of differences between healthy hearts of animals and sick hearts of patients, differences in arrest (no-flow) times and cardiopulmonary resuscitation (CPR) (low-flow) times, different pharmacokinetics, different dose/response requirements, and different timing of drug administration during low-flow CPR versus during spontaneous circulation. The need to stabilize normotension and prevent rearrest by titrated novel drug administration, once spontaneous circulation has been restored, requires research. Most of the above topics require some re-evaluation in clinically realistic animal models and in cardiac arrest patients, especially by titration of old and new drug treatments against variables that can be monitored continuously during resuscitation. 相似文献
996.
In today's clinical and social climate, psychotherapy in general, and trauma therapy in particular, can often be a tough, demanding, and even dangerous profession. This article examines some of the stresses and perils of doing crisis intervention and trauma therapy and offers recommendations on how psychotherapists can recognize warning signs, handle emergencies, get their own administrative and clinical support, and forestall the burnout that might keep them from performing the dedicated service on which a civilized society depends. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
998.
TC Kennedy SP Proudfoot WA Franklin TA Merrick G Saccomanno ME Corkill DL Mumma KE Sirgi YE Miller PG Archer A Prochazka 《Canadian Metallurgical Quarterly》1996,56(20):4673-4678
Advances in the understanding of lung cancer biology have led to observations that specific genetic changes occur in premalignant dysplasia. These observations have occurred predominantly in molecular studies of resected lung tumors and consequently, they may not be fully representative of those biological abnormalities characterizing premalignant lesions in individuals without overt lung cancer. Studies of premalignant epithelial cell biology and chemoprevention are needed in this patient subgroup. Such an initiative is now underway through the lung cancer Specialized Program of Research Excellence (SPORE) grant awarded to the University of Colorado Cancer Center (and affiliated institutions) by the National Cancer Institute. To identify participants for the early detection and chemoprevention trials of the Colorado SPORE, we initiated a sputum cytology screening program targeting persons with chronic obstructive pulmonary disease and smoking histories of 40 or more pack-years. During the first 26 months after activation of the screening program, sputum samples from 632 participants were evaluated. Of these, 533 (84%) of the subjects submitted specimens deemed adequate for cytopathological interpretation; 99 (16%) provided sputum samples unsuitable for cytodiagnosis. Of those participants who submitted adequate samples, 48% had cytodiagnoses of mild dysplasia, 26 % had moderate to severe dysplasia, and 2% presented with carcinoma in situ or invasive carcinoma. Logistic regression modeling was pursued to determine whether selected demographic and/or clinical status variables could be identified as statistically significant predictors of the specific cytological outcome to be expected (mild dysplasia, moderate dysplasia, and so forth). The only apparent associations found from both univariate and multivariate analyses were that the total number of pack-years of smoking history decreased with severity of cytodiagnosis and that those individuals with mild or moderate dysplasia were more likely to be ex-smokers than those with grades of regular metaplasia or lower. Based on the initial results of the Colorado SPORE sputum cytology screening program, we conclude that persons with chronic obstructive pulmonary disease and 40 or more pack-years of smoking history have a high prevalence of premalignant dysplasia detectable through sputum cytology and should be targeted for research programs focusing on lung cancer prevention, early detection, and exploratory biomarker studies. 相似文献
999.
MS Weintraub I Grosskopf T Rassin H Miller G Charach HH Rotmensch M Liron A Rubinstein A Iaina 《Canadian Metallurgical Quarterly》1996,312(7036):935-939
OBJECTIVE: To test the hypothesis that subjects who clear chylomicron remnants slowly from plasma may be at higher risk of coronary artery disease than indicated by their fasting plasma lipid concentrations. DESIGN: Case control study over three years. SETTING: An 800 bed general municipal hospital. SUBJECTS: 85 normolipidaemic patients with coronary artery disease selected prospectively and matched with 85 normolipidaemic subjects with normal coronary arteries on angiography. INTERVENTIONS: All subjects were given a vitamin A fat loading test which specifically labels intestinal lipoproteins with retinyl palmitate. MAIN OUTCOME MEASURE: Postprandial lipoprotein metabolism. RESULTS: The area below the chylomicron remnant retinyl palmitate curve was significantly increased in the coronary artery disease group as compared with the controls (mean 23.4 (SD 15.0) v 15.3 (8.9) mumol/l.h; 95% confidence interval of difference 4.37 to 11.82). CONCLUSION: Normolipidaemic patients with coronary artery disease had significantly higher concentrations of chylomicron remnants in plasma than normolipidaemic subjects with normal coronary vessels. This may explain the mechanism underlying the susceptibility to atherosclerosis of coronary artery disease patients with normal fasting lipid values. As diet and drugs can ameliorate the accumulation of postprandial lipoproteins in plasma, the concentration of chylomicron remnants should be measured in patients at high risk of coronary artery disease. 相似文献
1000.
W Junger WG Junger K Miller S Bahrami H Redl G Schlag E Moritz 《Canadian Metallurgical Quarterly》1996,43(12):1523-1529
BACKGROUND/AIMS: Early detection of anastomotic leaks after colorectal anastomosis is essential for adequate intervention to prevent peritonitis. We investigated whether the measurement of endotoxin (LPS) concentrations in the drainage has any value for the early detection of anastomotic leaks. MATERIALS AND METHODS: Twenty two patients with colorectal anastomosis were enrolled in this study, 3 developed clinically established signs of anastomotic leaks and 19 recovered without complications. LPS concentrations in the drainage, the total daily excreted LPS amounts, leukocyte and thrombocyte counts, plasma urea and creatinine, and body temperature were measured for up to 8 days after surgery and tested for their value to detect anastomotic leaks. RESULTS: LPS concentrations in the drainage fluid and daily excreted LPS amounts of patients with anastomotic leaks were significantly higher compared to the group without anastomotic leaks. On the third postoperative day, LPS concentrations ranged from 5270 to 6750 pg/ml in patients with anastomotic leaks and from 1 to 1848 pg/ml in patients without complications. Total daily excreted LPS amounts were 270-675 ng/day in patients with anastomotic leak and 0-92 ng/day in patients without anastomotic leaks. Both LPS-related parameters allowed reliable detection of anastomotic leaks on day 3 after surgery (Student's t-Test, p < 0.0005), while leukocyte and thrombocyte counts, plasma urea and creatinine, and body temperatures of both patient groups were not significantly different at any time (p > 0.05). CONCLUSION: We found that the measurement of LPS concentrations in the drainage and the daily excreted LPS amount could be valuable parameters for the early detection of anastomotic leaks as early as on the third post-operative day. 相似文献