全文获取类型
收费全文 | 2679篇 |
免费 | 6篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 3篇 |
综合类 | 7篇 |
化学工业 | 16篇 |
金属工艺 | 1篇 |
机械仪表 | 3篇 |
建筑科学 | 29篇 |
矿业工程 | 7篇 |
能源动力 | 2篇 |
轻工业 | 10篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 7篇 |
一般工业技术 | 15篇 |
冶金工业 | 2583篇 |
自动化技术 | 8篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 5篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 79篇 |
1998年 | 794篇 |
1997年 | 460篇 |
1996年 | 282篇 |
1995年 | 145篇 |
1994年 | 136篇 |
1993年 | 151篇 |
1992年 | 27篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 39篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 29篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1978年 | 8篇 |
1977年 | 58篇 |
1976年 | 176篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有2695条查询结果,搜索用时 46 毫秒
991.
992.
Transendoscopic pulsed dye laser lithotripsy was effective in the treatment of calcium carbonate urothlithiasis in 2 adult geldings. Perineal urethrotomy provided convenient access for standing transendoscopic lithotripsy and evacuation of a large cystic calculus in one gelding. In the second horse, an obstructive urethral calculus was fragmented and removed by a transurethroscopic approach. Pulsed dye laser lithotriptor is effective in fragmentation of the most common form (calcium carbonate) of uroliths in horses and may be performed in standing horses with reduced surgical invasiveness and trauma to the urinary tract, compared with conventional approaches. The principle disadvantages include cost of the procedure, which is comparable to laparocystotomy, and the time delay required to make arrangements for use of the pulsed dye laser lithotriptor. 相似文献
993.
大型洞室群收敛位移分析的集成智能研究 总被引:5,自引:1,他引:4
针对地下大型洞室群施工的反馈分析速度慢、难以跟上施工进度的问题,研究了把数据库、知识库、模型库和推理机集成为一体的收敛位移的智能分析系统,并开发了系统原型.介绍了系统功能、总体结构、各子系统的结构、推理方法和数据组织方式.通过该系统对富尔江引水遂洞桩号1+205断面的位移数据的分析,证明本系统的开发是成功的. 相似文献
994.
995.
STUDY OBJECTIVE: To describe the effectiveness of an emergency medical education program in a postwar developing country. METHODS: A prospective, nonrandomized interrupted time-series study was conducted in an emergency department at a national referral hospital in Rwanda immediately after the 1994 civil war. Participants included 11 medical personnel staffing the ED comprising physicians, nurses, and medical assistants. International medical relief workers in the ED identified deficiencies by directly observing routine clinical practices. On the basis of this assessment, formal training programs in trauma resuscitation, airway management, wound care, and blood/fluid precautions were conducted. Subjects were then observed 1 week and 2 months after the educational programs and scored on a standardized data-collection form. Scores before and after intervention were compared with the use of Fisher's exact test to determine program effectiveness. RESULTS: Educational interventions with statistically significantly longer term effects included wound management principles and blood/fluid precautions (before versus after intervention, P < .05). Interventions with the least sustained effect included advanced airway interventions and procedures related to trauma resuscitation. CONCLUSION: Educational seminars proved to have the greatest sustained effect on those behaviors requiring minimal equipment and noncomplex medical decisionmaking. 相似文献
996.
Thirty consecutive patients with amputation or devascularizing injuries of the thumb or two or more fingers proximal to the PIP joint were reviewed. Replantation or revascularization had been done in 27 patients, in 24 successfully. Three patients had primary amputation. The distribution of calculable costs was dominated by those for sick leave (49%), operation (26%) and ward costs (20%). Out-patient care, physiotherapy and travel together constituted only 6%. The cost of a successful replantation was equal to 1.6 times the mean annual salary of these patients and that of primary amputation about half as much. Mobility, power and performance of a standardized grip test were better for the successfully replanted or revascularized patients. Subjective evaluation of 23 parameters of function, cosmesis and quality of life did not disclose any differences. All patients except three had returned to their original work within 2 years. 相似文献
997.
BACKGROUND: Polyethylene glycol (PEG) has been shown to potentiate antigen-antibody reactions. STUDY DESIGN AND METHODS: To investigate the utility of PEG in pretransfusion testing, a blinded comparison study of PEG and a low-ionic-strength additive solution (LISS) was conducted. A total of 500 patient samples were tested in parallel with reagent antibody-detection cells using blind-coded PEG and LISS potentiators. RESULTS: In 34 (34%) of 100 samples with known antibodies in the Rh, Kell, Duffy, Kidd, and MNS systems, PEG antiglobulin reactions were stronger (total score, 382) than LISS antiglobulin reactions (total score, 216), and in 66 cases (66%), they were equal to those of LISS. Of 400 samples without detectable antibodies, 384 were negative with PEG and LISS, and 16 were positive in PEG tests and negative in LISS. Seven of the 16 were clinically important antibodies (D, 1; E, 3; Fya, 1; Jka; 1; Jkb, 1), and four were clinically benign antibodies (Le(a), 2; McCc, 1; Sda, 1). Five of the 16 demonstrated inconclusive PEG reactions, for a false-positive rate of 5 in 400 (1.3%). Of the 500 samples, none was negative in PEG tests and positive in LISS (0% false-negative rate). CONCLUSION: Although PEG demonstrates a relatively high false-positive rate, PEG is more sensitive than LISS in detecting clinically significant antibodies. 相似文献
998.
999.
H Krakauer MJ Lin EM Schone D Park RC Miller J Greenwald RC Bailey B Rogers G Bernstein DE Lilienfeld SM Stahl RS Crawford DC Schutt 《Canadian Metallurgical Quarterly》1998,4(1):11-29
The functioning of working memory in schizophrenic patients according to Baddeley's model was examined in two complementary experiments. Experiment 1 comprised 27 patients and their controls, matched in age and level of education. Of this pool, 20 pairs participated also in Experiment 2. Digit span, reading rate, and immediate serial recall assessed the functioning of the phonological loop. Corsi and pattern span tasks assessed the capacity of visuo-spatial memory. The central executive's ability to monitor two concurrent tasks was evaluated in a dual task paradigm, and its capacity to control action in a random generation task. A preliminary set of analyses showed that the patients' performances were reduced in all tasks explored, except in digit span. This initial pattern changed consistently after controlling for reading rate. While slow and fast reading patients were comparable in demographic and clinical criteria, slow reading patients showed impaired performance in all tasks, whereas fast reading patients exhibited reduced performance in visuo-spatial tasks and in the random generation task only. The state of functioning of working memory in schizophrenia appears, therefore, to vary consistently among the components of the model and is markedly impaired in slow reading patients. The implications of slowness are discussed. 相似文献
1000.
RS Larson MA Scott TL McCurley CL Vnencak-Jones 《Canadian Metallurgical Quarterly》1996,56(19):4378-4381
The genetic mechanisms that give rise to posttransplant lymphoproliferative disorders (PTLDs) are not well established, yet previous studies have focused or) the role of immunosuppression and EBV infection. We investigated whether microsatellite analysis could: (a) determine the recipient/donor origin of the tumor; and (b) document novel genetic alterations in PTLDs, i.e., microsatellite instability. We characterized seven cases of PTLD (five B-cell and two T-cell non-Hodgkin's lymphomas) in which donor allograft tissue, normal recipient tissue, and tissue from the PTLDs were available. In each case, six microsatellite loci were analyzed. Five cases were of host origin (three B-cell and two T-cell lymphomas). The two cases of donor origin were B-cell lymphomas. Multiple loci showed microsatellite instability in two cases of host-derived T-cell non-Hodgkin's lymphomas (28% of PTLDs). These findings show that microsatellite analysis may be used to determine the host or donor origin of PTLDs and suggest for the first time that defective DNA mismatch repair may be an underlying genetic mechanism of lymphomagenesis in some cases of PTLD. 相似文献