全文获取类型
收费全文 | 5018篇 |
免费 | 96篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 32篇 |
综合类 | 3篇 |
化学工业 | 447篇 |
金属工艺 | 103篇 |
机械仪表 | 50篇 |
建筑科学 | 136篇 |
矿业工程 | 12篇 |
能源动力 | 61篇 |
轻工业 | 374篇 |
水利工程 | 41篇 |
石油天然气 | 10篇 |
无线电 | 198篇 |
一般工业技术 | 431篇 |
冶金工业 | 2907篇 |
原子能技术 | 41篇 |
自动化技术 | 269篇 |
出版年
2022年 | 45篇 |
2021年 | 49篇 |
2020年 | 40篇 |
2019年 | 48篇 |
2018年 | 51篇 |
2017年 | 45篇 |
2016年 | 50篇 |
2015年 | 51篇 |
2014年 | 55篇 |
2013年 | 137篇 |
2012年 | 103篇 |
2011年 | 155篇 |
2010年 | 128篇 |
2009年 | 135篇 |
2008年 | 157篇 |
2007年 | 116篇 |
2006年 | 117篇 |
2005年 | 108篇 |
2004年 | 88篇 |
2003年 | 75篇 |
2002年 | 94篇 |
2001年 | 59篇 |
2000年 | 71篇 |
1999年 | 114篇 |
1998年 | 781篇 |
1997年 | 442篇 |
1996年 | 308篇 |
1995年 | 176篇 |
1994年 | 155篇 |
1993年 | 183篇 |
1992年 | 57篇 |
1991年 | 55篇 |
1990年 | 62篇 |
1989年 | 61篇 |
1988年 | 47篇 |
1987年 | 56篇 |
1986年 | 42篇 |
1985年 | 44篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 24篇 |
1981年 | 36篇 |
1980年 | 42篇 |
1979年 | 11篇 |
1978年 | 17篇 |
1977年 | 101篇 |
1976年 | 172篇 |
1975年 | 11篇 |
1973年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有5115条查询结果,搜索用时 18 毫秒
11.
Nietzel Michael T.; Russell Robert L.; Hemmings Kelly A.; Gretter Monica L. 《Canadian Metallurgical Quarterly》1987,55(2):156
[Correction Notice: An erratum for this article was reported in Vol 55(3) of Journal of Consulting and Clinical Psychology (see record 2008-10745-001). The data presented in Table 2 were incorrect because a row and a column were inadvertently omitted. The corrected Table 2 appears in the erratum.] This study used meta-analysis to study the clinical significance of psychotherapy for symptoms of unipolar depression. The following questions were addressed: How similar is the posttherapy adjustment of depressed adults to that of nondepressed adults? Is this adjustment maintained at follow-up? What dimensions of treatment, therapists, or design are associated with clinical significance? Using the Beck Depression Inventory (BDI), we calculated composite BDI norms from 28 published studies. Sixty effect sizes (from 31 outcome studies utilizing the BDI) were calculated. The results indicated that psychotherapy produces outcomes that have moderate clinical significance and that are well-maintained at follow-up, that individual therapy is associated with greater clinical significance than group treatment, and that type of therapy is not related to improvement. Alternative approaches for operationalizing clinical significance as the return of individuals to normal levels of functioning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
Negative thermal expansion of laminates 总被引:1,自引:0,他引:1
Measurements have been carried out on the in-plane and through the thickness thermal expansion coefficients of glass polypropylene fibre composites of 50% volume fraction between room temperature and 120°C. Only in the temperature range 20° to 75°C are reproducible results obtained. It is confirmed that in-plane negative values may be obtained in specific directions. The physical reason for this and its connection with the necessary appearance of a large Poisson ratio is pointed out. The expansivity of the matrix material depends strongly on temperature. Very good agreement between the experimental values and those predicted from the properties of the two constituents is found provided that the value for the expansivity of the polyoropylene is that within the temperature range considered. It is shown that the polypropylene matrix does not provide a matrix which is stable enough in its properties to enable the system to yield consistent negative values of expansivity. An alternative system is proposed and a single experiment confirms that a negative value of the thermal expansivity of as large as –50 × 10–6 K–1 may be obtained. 相似文献
13.
Wilcox Sara; Evenson Kelly R.; Aragaki Aaron; Wassertheil-Smoller Sylvia; Mouton Charles P.; Loevinger Barbara Lee 《Canadian Metallurgical Quarterly》2003,22(5):513
This study examined whether widowhood was associated with physical and mental health, health behaviors, and health outcomes using a cross-sectional (N=72,247) and prospective (N=55,724) design in women aged 50-79 years participating in the Women's Health Initiative observational study (85.4% White). At baseline, married women reported better physical and mental health and generally better health behaviors than widowed women. Whereas women who remained married over the 3-year period showed stability in mental health, recent widows experienced marked impairments and longer term widows showed stability or slight improvements. Both groups of widows reported more unintentional weight loss over the 3-year period. Changes in physical health and health behaviors were inconsistent, with generally small effect sizes. Findings underscore the resilience of older women and their capacity to reestablish connections, but point to the need for services that strengthen social support among women who have difficulty during this transition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
William E. Kelly 《Canadian Metallurgical Quarterly》2007,133(3):181-187
Certification has been common for technicians for many years but specialty certification is rapidly becoming important to engineering practitioners in addition to or as a substitute for licensure in some fields. Certification and accreditation are closely related but there are also important differences. International standards now exist for accreditation of certification programs and could provide the basis for mutual recognition of specialty certification worldwide. ASCE should seek international accreditation of its specialty certification programs and play an appropriate role in defining international standards related to specialty certification and assessment of conformity to those standards. 相似文献
15.
PJ Jenkins MA Satta M Simmgen WM Drake C Williamson DG Lowe K Britton SL Chew RV Thakker GM Besser 《Canadian Metallurgical Quarterly》1997,47(6):747-751
We report a patient with a metastatic parathyroid carcinoma and medullary carcinoma of the thyroid. This patient represents a variation of the multiple endocrine neoplasia syndrome (MEN) type 2A. There was no evidence of a phaeochromocytoma. The case illustrates the difficulties that may be encountered in localising the source of PTH secretion; the patient underwent four unsuccessful exploratory operations of the neck and mediastinum before further investigations revealed a single metastatic deposit of parathyroid carcinoma involving the first thoracic vertebra. PCR amplification and sequencing of the RET oncogene from the metastatic parathyroid carcinoma and genomic DNA revealed a heterozygous mutation (Cys634Tyr) in exon 11, as has previously been described to occur in MEN 2A. In addition, loss of tumour heterozygosity was demonstrated at loci from chromosomes 1, 2, 3p, 13q and 16p. This represents the first report of a parathyroid carcinoma in a MEN2A patient, in which the multiple allelic deletions are consistent with the generalised losses observed in aggressive tumours. 相似文献
16.
17.
The iron status of 22 children and adolescents with Crohn's disease (mean age: 13 years) was evaluated. Eleven patients were suffering from active disease with inflammation, identified by at least one abnormal value for serum orosomucoid, C-reactive protein or sedimentation rate (group I). Eleven patients were in clinical remission and showed no biological evidence of inflammation (group II). Hemoglobin and red cell indices, erythrocyte protoporphyrin, serum iron, transferrin, serum ferritin and basic red cell ferritin were determined in all patients. The usual indicators of iron status, particularly serum ferritin, were affected by the inflammatory processes, but basic red cell ferritin appeared to be independent of inflammation. Basic red cell ferritin can therefore be considered to be a reliable indicator of iron status in children and adolescents with Crohn's disease. 相似文献
18.
Integrating principles from a variety of theory has led to the development of a conceptual framework for reengineering in a clinical care delivery setting to improve the value of services provided to the customer. A conceptual framework involving the identification of three high level core processes to reengineer can provide clarity and focus for clinicians to begin directing reengineering efforts. Those core processes are: clinical management of the patient's medical needs, patient operational processes to support the clinical processes, and administrative decision-making processes to support the implementation of the clinical and operational processes. Improvement in any one of these areas has the potential to increase value, but the concurrent targeting of these core processes for reengineering has provided a synergy that has accelerated the achievement of the desired outcomes in the area of surgical services. 相似文献
19.
KC Kocis PJ Radell WI Sternberger JE Benson RJ Traystman DG Nichols 《Canadian Metallurgical Quarterly》1997,83(5):1654-1659
Clinically, a noninvasive measure of diaphragm function is needed. The purpose of this study is to determine whether ultrasonography can be used to 1) quantify diaphragm function and 2) identify fatigue in a piglet model. Five piglets were anesthetized with pentobarbital sodium and halothane and studied during the following conditions: 1) baseline (spontaneous breathing); 2) baseline + CO2 [inhaled CO2 to increase arterial PCO2 to 50-60 Torr (6.6-8 kPa)]; 3) fatigue + CO2 (fatigue induced with 30 min of phrenic nerve pacing); and 4) recovery + CO2 (recovery after 1 h of mechanical ventilation). Ultrasound measurements of the posterior diaphragm were made (inspiratory mean velocity) in the transverse plane. Images were obtained from the midline, just inferior to the xiphoid process, and perpendicular to the abdomen. M-mode measures were made of the right posterior hemidiaphragm in the plane just lateral to the inferior vena cava. Abdominal and esophageal pressures were measured and transdiaphragmatic pressure (Pdi) was calculated during spontaneous (Sp) and paced (Pace) breaths. Arterial blood gases were also measured. Pdi(Sp) and Pdi(Pace) during baseline + CO2 were 8 +/- 0.7 and 49 +/- 11 cmH2O, respectively, and decreased to 6 +/- 1.0 and 27 +/- 7 cmH2O, respectively, during fatigue + CO2. Mean inspiratory velocity also decreased from 13 +/- 2 to 8 +/- 1 cm/s during these conditions. All variables returned to baseline during recovery + CO2. Ultrasonography can be used to quantify diaphragm function and identify piglet diaphragm fatigue. 相似文献
20.
Kelly Jeffrey A.; Murphy Debra A.; Sikkema Kathleen J.; Kalichman Seth C. 《Canadian Metallurgical Quarterly》1993,48(10):1023
Behavior change remains the only means for primary prevention of HIV disease. Psychology should take a leading role in efforts to curtail the epidemic, but has not contributed to HIV prevention at a level proportionate to the urgency of the crisis. The authors propose an updated agenda for behavioral research on AIDS-HIV prevention implementing accelerated community trials of promising behavior change models, conducting trials of community-level interventions on a large scale and focused on populations most vulnerable to HIV infections, establishing partnerships between HIV research and community service organizations, integrating efforts from across psychology disciplines to advance and refine HIV prevention interventions, and mobilizing interdisciplinary HIV prevention resources and communication mechanisms to rapidly translate research findings to community and public policy arenas. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献