全文获取类型
收费全文 | 4662篇 |
免费 | 163篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 26篇 |
综合类 | 1篇 |
化学工业 | 826篇 |
金属工艺 | 41篇 |
机械仪表 | 63篇 |
建筑科学 | 186篇 |
矿业工程 | 12篇 |
能源动力 | 79篇 |
轻工业 | 490篇 |
水利工程 | 35篇 |
石油天然气 | 8篇 |
无线电 | 331篇 |
一般工业技术 | 655篇 |
冶金工业 | 1602篇 |
原子能技术 | 16篇 |
自动化技术 | 457篇 |
出版年
2022年 | 72篇 |
2021年 | 84篇 |
2020年 | 44篇 |
2019年 | 58篇 |
2018年 | 83篇 |
2017年 | 77篇 |
2016年 | 64篇 |
2015年 | 68篇 |
2014年 | 93篇 |
2013年 | 223篇 |
2012年 | 161篇 |
2011年 | 214篇 |
2010年 | 161篇 |
2009年 | 181篇 |
2008年 | 184篇 |
2007年 | 185篇 |
2006年 | 165篇 |
2005年 | 163篇 |
2004年 | 132篇 |
2003年 | 120篇 |
2002年 | 147篇 |
2001年 | 91篇 |
2000年 | 95篇 |
1999年 | 114篇 |
1998年 | 242篇 |
1997年 | 184篇 |
1996年 | 139篇 |
1995年 | 101篇 |
1994年 | 94篇 |
1993年 | 96篇 |
1992年 | 71篇 |
1991年 | 29篇 |
1990年 | 58篇 |
1989年 | 63篇 |
1988年 | 57篇 |
1987年 | 56篇 |
1986年 | 47篇 |
1985年 | 54篇 |
1984年 | 55篇 |
1983年 | 34篇 |
1982年 | 38篇 |
1981年 | 38篇 |
1980年 | 36篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1977年 | 38篇 |
1976年 | 61篇 |
1975年 | 30篇 |
1974年 | 18篇 |
1973年 | 19篇 |
排序方式: 共有4828条查询结果,搜索用时 46 毫秒
991.
992.
A symposium was conducted at the 94th Annual Convention of the American Psychological Association (Cox, 1986) that depicted psychologists' innovative, nontraditional work with alcohol-dependent veterans. The articles in this special series represent expansions of a portion of the earlier convention presentations. Psychologists from other VA medical centers (and elsewhere) might wish to incorporate the approaches that are discussed into their own treatment programs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Widows Michelle R.; Jacobsen Paul B.; Booth-Jones Margaret; Fields Karen K. 《Canadian Metallurgical Quarterly》2005,24(3):266
There is growing recognition that the experience of cancer can have a positive as well as a negative psychological impact. This longitudinal study sought to identify predictors of posttraumatic growth among cancer patients (N=72) undergoing bone marrow transplantation. Greater posttraumatic growth in the posttransplant period was related to younger age; less education; greater use of positive reinterpretation, problem solving, and seeking alternative rewards as coping strategies in the pretransplant period; more stressful appraisal of aspects of the transplant experience; and more negatively biased recall of pretransplant levels of psychological distress. Findings partially support J. A. Schaefer and R. H. Moos's (1992) model of life crises and personal growth and also suggest that temporal self-comparisons contribute to the experience of posttraumatic growth. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
Cox R.V. Gay S.L. Shoham Y. Quackenbush S.R. Seshadri N. Jayant N.S. 《Selected Areas in Communications, IEEE Journal on》1988,6(2):391-409
Two very different subband coders are described. The first is a modified dynamic bit-allocation-subband coder (D-SBC) designed for variable rate coding situations and easily adaptable to noisy channel environments. It can operate at rates as low as 12 kb/s and still give good quality speech. The second coder is a 16-kb/s waveform coder, based on a combination of subband coding and vector quantization (VQ-SBC). The key feature of this coder is its short coding delay, which makes it suitable for real-time communication networks. The speech quality of both coders has been enhanced by adaptive postfiltering. The coders have been implemented on a single AT&T DSP32 signal processor 相似文献
995.
Keith P. Fruzzetti Ahmet Palazoglu Jose A. Romagnoli Karen A. McDonald 《Journal of Process Control》1991,1(4)
In process control, a significant number of problems are encountered where there are hard and soft constraints on the measured process variables and/or on the value and rate of change of the manipulated variables. On-line implementation of traditional control strategies becomes unfeasible since they cannot explicitly deal with process constraints. Model predictive control offers a viable alternative; however, a prominent issue is the behaviour of these algorithms when the prediction model does not match the actual plant. A possible solution is to formulate the problem in a linear/non-linear programming framework, using the cutting plane technique to locate the ‘worst’ plant/model mismatch at every time interval. This results in a very practical cautious predictive controller that computes the next controller action based on expected model/plant mismatch. Control of a stirred tank reactor illustrates the method, using a one-step ahead predictive controller. 相似文献
996.
What are entrepreneurial dietitians charging? The Consulting Dietitians Network National Fee Survey.
Karen Davison Anet Mor Helene Charlebois 《Revue canadienne de la pratique et de la recherche en diététique》2004,65(4):186-190
To respond to a need to develop a national fee guideline, the Consulting Dietitians Network conducted a membership fee survey. A questionnaire requesting fee information for various nutrition consulting services was distributed to members as an insert with the Consulting Dietitians Network quarterly newsletter and by electronic mail. The response rate was 38.4% (98 respondents) and most respondents (74.5%) had urban practices. The most frequently charged fees (mode) for individual counselling ($75/hour), industry and commercial firm consultations ($150/hour), group facilitation ($150/hour), and media consultations ($150/article) were highest in the region of Ontario, Quebec, and the Atlantic provinces. The most frequently charged fees (mode) for home visits ($100/hour), writing for newspapers ($250/hour), and menu reviews ($60/hour) were highest in the region of Saskatchewan and Manitoba. The minimum and maximum fees were significantly different for the three regions (Ontario, Quebec, and the Atlantic provinces; Manitoba and Saskatchewan; and Alberta, British Columbia, and Yukon Territory) studied for initial client consultations, industry and commercial firm consultations, and menu reviews (p<0.05). For home visits, teaching in an institution, seminar presentations, group facilitation, media consultations, and writing media articles, the differences in the minimum and maximum fees charged were highly significant (p<0.001). Entrepreneurial dietitians may use these data as a reference to establish and negotiate consultation fees. 相似文献
997.
M Pfisterer JL Cox CB Granger SJ Brener CD Naylor RM Califf F van de Werf AL Stebbins KL Lee EJ Topol PW Armstrong 《Canadian Metallurgical Quarterly》1998,32(3):634-640
OBJECTIVES: We assessed the use and effects of acute intravenous and later oral atenolol treatment in a prospectively planned post hoc analysis of the GUSTO-I dataset. BACKGROUND: Early intravenous beta blockade is generally recommended after myocardial infarction, especially for patients with tachycardia and/or hypertension and those without heart failure. METHODS: Besides one of four thrombolytic strategies, patients without hypotension, bradycardia or signs of heart failure were to receive atenolol 5 mg intravenously as soon as possible, another 5 mg intravenously 10 min later and 50 to 100 mg orally daily during hospitalization. We compared the 30-day mortality of patients given no atenolol (n=10,073), any atenolol (n=30,771), any intravenous atenolol (n=18,200), only oral atenolol (n=12,545) and both intravenous and oral drug (n=16,406), after controlling for baseline differences and for early deaths (before oral atenolol could be given). RESULTS: Patients given any atenolol had a lower baseline risk than those not given atenolol. Adjusted 30-day mortality was significantly lower in atenolol-treated patients, but patients treated with intravenous and oral atenolol treatment vs. oral treatment alone were more likely to die (odds ratio, 1.3; 95% confidence interval, 1.0 to 1.5; p=0.02). Subgroups had similar rates of stroke, intracranial hemorrhage and reinfarction, but intravenous atenolol use was associated with more heart failure, shock, recurrent ischemia and pacemaker use than oral atenolol use. CONCLUSIONS: Although atenolol appears to improve outcomes after thrombolysis for myocardial infarction, early intravenous atenolol seems of limited value. The best approach for most patients may be to begin oral atenolol once stable. 相似文献
998.
DN Cox AS Anderson J Reynolds S McKellar ME Lean DJ Mela 《Canadian Metallurgical Quarterly》1998,80(2):123-131
Employing clonal cell lines derived from rat embryonic hippocampal cells, we detected neuropeptide Y (NPY) mRNA in three progenitor subcloned cell lines. These cell lines upon differentiation express markers indicative of commitment to either neuronal (H19-7; NF +, GFAP -), glial (H19-5; GFAP +, NF -), or bipotential (H583-5; NF +, GFAP + ) lineages. Induction of differentiation was associated with the persistence of the NPY mRNA, however, in the differentiated H19-7 cells a 20-fold increase in NPY mRNA levels was observed (P<0.05). NPY immunoreactivity was observed only in cells with a differentiated neuronal phenotype. The cellular radioimmunoassayable NPY peptide levels increased twelve-fold without a change in extracellular NPY peptide levels by multi-factorially induced neuronal or glial cell differentiation. The differentiated H19-5 cells expressed lower levels of NPY that could not be immunocytochemically detected. The peripheral sympathetic PC-12 neuronal cells examined in the undifferentiated and nerve growth factor-driven differentiated states expressed NPY only upon differentiation. We conclude that NPY is expressed by the cultured undifferentiated and differentiated rat hippocampal clonal cell lines, while the peripheral sympathetic PC-12 neuronal cell line only expresses the NPY gene upon differentiation. These immortalized embryonic neural cell line(s) will provide a hippocampal cell line(s) to conduct future in-vitro investigations targeted at determining the cellular and molecular mechanisms governing NPY gene expression. 相似文献
999.
SJ Rosenthal LA Harrison KG Baxter LH Wetzel GG Cox S Batnitzky 《Canadian Metallurgical Quarterly》1995,15(5):1103-1111
In helical portal venous blood flow, the usual laminar flow in the portal vein is replaced by a spiral. This changes the color Doppler ultrasound (US) appearance to one of alternating or parallel red and blue bands. Duplex US may appear to show hepatopetal, hepatofugal, or simultaneous bidirectional flow depending on placement of the cursor within the helix. Helical portal venous flow is unusual in normal individuals (2.2% of 135 patients). Its presence should prompt further scrutiny for signs of liver disease, particularly portosystemic shunts, as in 20% of 41 patients who subsequently underwent liver transplantation. It is a normal finding immediately after liver transplantation (43% of 35 patients) and transjugular intrahepatic portosystemic shunt (TIPS) creation (28% of 36 patients). In both liver transplant and TIPS recipients, helical flow is usually transient. Its persistence long after transplantation in association with a prolonged increase in portal venous velocity is a useful sign of portal vein stenosis. Helical flow may also occur in cases of neoplastic invasion or displacement of the portal vein. 相似文献
1000.
DC Howlett AG Hatrick JM Jarosz JB Bingham TC Cox AT Irvine 《Canadian Metallurgical Quarterly》1997,52(11):821-829
Sickle cell disease is the most common inherited haemoglobinopathy described. Complications of sickle cell disease (SCD) are due to chronic haemolysis of fragile red cells or secondary to vascular occlusion by sickled red cells with subsequent tissue infarction. Traditionally plain film radiography has been the mainstay in the assessment of patients with SCD, but increasingly magnetic resonance (MR) imaging and computed tomography (CT) are being used. In this review the imaging features of a range of complications of SCD are demonstrated with particular emphasis on CT and MR. 相似文献