全文获取类型
收费全文 | 3628篇 |
免费 | 3篇 |
专业分类
综合类 | 3篇 |
化学工业 | 9篇 |
机械仪表 | 1篇 |
建筑科学 | 2篇 |
轻工业 | 3篇 |
无线电 | 3篇 |
一般工业技术 | 4篇 |
冶金工业 | 3598篇 |
自动化技术 | 8篇 |
出版年
2017年 | 1篇 |
2015年 | 1篇 |
2010年 | 1篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2004年 | 1篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 125篇 |
1998年 | 1119篇 |
1997年 | 622篇 |
1996年 | 426篇 |
1995年 | 216篇 |
1994年 | 182篇 |
1993年 | 195篇 |
1992年 | 33篇 |
1991年 | 61篇 |
1990年 | 59篇 |
1989年 | 51篇 |
1988年 | 54篇 |
1987年 | 56篇 |
1986年 | 26篇 |
1985年 | 39篇 |
1983年 | 2篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 26篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 76篇 |
1976年 | 191篇 |
1975年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有3631条查询结果,搜索用时 8 毫秒
921.
Unilateral naris closure in young rodents leads to striking alterations in the development of the ipsilateral olfactory system. One of the most pronounced effects is a 25% reduction in the size of the experimental olfactory bulb, a change that stems in part from decreased cell survival. Since naris occlusion in rodents alters the system more during development than in adulthood, we investigated the consequences of olfactory deprivation in a species that is born in a very immature state, Monodelphis domestica. In this pouchless marsupial, offspring are born after a short 14-day gestation. In the present study, the thymidine analogue bromodeoxyuridine was used to examine early postnatal neurogenesis in the olfactory bulb. Unlike rats and mice, neurogenesis of the main output neurons (the mitral cells) continues into postnatal life. Unilateral naris closure was begun on postnatal day 4 (P4) or P5 in Monodelphis and continued for 30 or 60 days. Laminar volume measurements revealed a significant reduction in the size of the experimental bulb following 60, but not 30, days of early olfactory deprivation. Mitral cell number estimates indicated a significant reduction after both 30 and 60 days of naris closure. The immaturity of Monodelphis offspring may render the population of mitral cells susceptible to the effects of olfactory deprivation. These findings suggest that afferent activity plays a role in the survival of all bulb neurons, irrespective of cell class. 相似文献
922.
There is a very strong need for an effective and reliable method of contraception in the diabetic woman. An unplanned pregnancy that occurs when her diabetes is not under good control can have disastrous consequences, ranging from abortion to a congenitally malformed fetus. The most important factor in the contraceptive decision for the diabetic patient, especially the IDDM patient, is that the choice be made not by the clinician alone or the patient alone, but through a carefully through-out process that involves both patient and physician. 相似文献
923.
CY Chan DC Molrine JH Antin C Wheeler EC Guinan HJ Weinstein NR Phillips C McGarigle S Harvey C Schnipper DM Ambrosino 《Canadian Metallurgical Quarterly》1997,20(1):33-38
OBJECTIVE: Although there are many anecdotal reports that psychological intervention is effective in enhancing adjustment to spinal cord injury (SCI), there are little data to support this assertion. To date, reports of few longitudinal-based controlled trials that assessed psychological outcomes for SCI persons have been published. This study was conducted to determine long-term efficacy of cognitive behavior therapy during rehabilitation. DESIGN: The study employed a nonrandomized controlled trial, and measures were taken on three occasions: before, immediately after, and 12 months after treatment. SETTING, OUTCOME MEASURES, AND INTERVENTION: Anxiety, depressive mood, and self-esteem were assessed in 28 SCI persons consecutively selected on admission to hospital, who participated in specialized group cognitive behavior therapy (CBT) during rehabilitation. CONTROLS: The intervention group's responses on the measures were compared with a control group of 41 SCI persons who only received traditional rehabilitation services during their hospitalization. RESULTS: There were no overall group differences on anxiety, depressive mood, and self-esteem, although there was a trend for the treatment group to have greater levels of improvement in depression scores across time in comparison to the control group. However, those in the treatment group who reported high levels of depressive mood before the CBT treatment were significantly less depressed 1 year after injury, compared to similar persons in the control group. CONCLUSIONS: While it appears not everyone who experiences SCI needs CBT, at least in the hospital phase of their rehabilitation, those who report high levels of depressive mood benefited greatly from CBT. 相似文献
924.
Chiropractic is an important component of the US health care system and the largest alternative medical profession. In this overview of chiropractic, we examine its history, theory, and development; its scientific evidence; and its approach to the art of medicine. Chiropractic's position in society is contradictory, and we reveal a complex dynamic of conflict and diversity. Internally, chiropractic has a dramatic legacy of strife and factionalism. Externally, it has defended itself from vigorous opposition by conventional medicine. Despite such tensions, chiropractors have maintained a unified profession with an uninterrupted commitment to clinical care. While the core chiropractic belief that the correction of spinal abnormality is a critical health care intervention is open to debate, chiropractic's most important contribution may have to do with the patient-physician relationship. 相似文献
925.
926.
LA Auersvald DM Rothstein SC Oliveira CQ Khuong H Onodera AI Lazarovits GP Basadonna 《Canadian Metallurgical Quarterly》1997,63(9):1355-1358
BACKGROUND: Although islet cell transplantation is considered an ideal form of endocrine replacement for type I diabetes, clinical application in humans is still not feasible. New immunosuppressive strategies are clearly needed to control inexorable rejection. CD45 is a family of transmembrane protein tyrosine phosphatases critically involved in the regulation of lymphocyte activation signals. Anti-CD45RB monoclonal antibody can prevent rejection of murine renal allografts. METHODS: Here, we examine the consequences of targeting CD45 in murine islet cell transplantation. Diabetic mice recipients received islet allografts under the kidney capsule and were divided into seven groups. Recipients received no treatment (controls) or anti-CD45RB monoclonal antibody (mAb; MB23G2 or C363.16A) at different dosages and treatment intervals. RESULTS: All untreated control animals lost islet function, becoming hyperglycemic within 10-17 days after transplantation. Animals treated with either anti-CD45RB mAb showed a significant prolongation of islet allograft survival when compared with controls. Anti-CD45RB MB23G2 at 100 microg/day, given on days -1, 0, and 5 was particularly effective, inducing indefinite islet allograft survival in 60% of recipients. CONCLUSIONS: These results indicate that anti-CD45 mAbs are potent immunomodulatory agents, able to sustain indefinite islet allograft function after a short treatment course in the highly immunogenic model of islet transplantation. 相似文献
927.
928.
We assessed relationships of evoked electrical and light scattering changes from cat dorsal hippocampus following Schaeffer collateral stimulation. Under anesthesia, eight stimulating electrodes were placed in the left hippocampal CA field and an optic probe, coupled to a photodiode or a charge-coupled device camera to detect scattered light changes, was lowered to the contralateral dorsal hippocampal surface. Light at 660 +/- 10 (SE) nm illuminated the tissue through optic fibers surrounding the optic probe. An attached bipolar electrode recorded evoked right hippocampal commissural potentials. Electrode recordings and photodiode output were simultaneously acquired at 2.4 kHz during single biphasic pulse stimuli 0.5 ms in duration with 0.1-Hz intervals. Camera images were digitized at 100 Hz. An average of 150 responses was calculated for each of six stimulating current levels. Stimuli elicited a complex population synaptic potential that lasted 100-200 ms depending on stimulus intensity and electrode position. Light scattering changes peaked 20 ms after stimuli and occurred simultaneously with population spikes. A long-lasting light scattering component peaked 100-500 ms after the stimulus, concurrently with larger population postsynaptic potentials. Optical signals occurred over a time course similar to that for electrical signals and increased with larger stimulation amplitude to a maximum, then decreased with further increases in stimulation current. Camera images revealed a topographic response pattern that paralleled the photodiode measurements and depended on stimulation electrode position. Light scattering changes accompanied fast electrical responses, occurred too rapidly for perfusion, and showed a stimulus intensity relationship not consistent with glial changes. 相似文献
929.
Native porcine erythrocytes do not initiate blood coagulation, though even the weak association (Kd = 4,25 +/- 9,35 microM) of prothrombin with their surface which is limited to the projection of two phospholipid polar head groups onto the external cell membrane, exerts a slight but authentic influence on the acceleration of blood clotting. There are 11.9 x 10(7) sites for 125I-prothrombin on one erythrocytes. At physiological concentration of prothrombin the surface of erythrocytes is far from saturation. The binding of 125I-labelled prothrombin to erythrocytes after their surface was covered by lectin Glycine max by means of the accessible residues of N-acetyl-D-galactosamine and D-galactose, glycoproteins and dlycolipids can never become saturated with any used concentration of the ligand. In the presence of the suspension of erythrocytes treated lectin platelet free plasma coagulates at the same speed as the control plasma. 相似文献
930.
DM Allen LA Hey TR Heinz R Golal LS Levin 《Canadian Metallurgical Quarterly》1997,13(7):475-85; discussion 486-7
Rigorous clinical outcomes research requires accurate, complete, and standardized data. No such system is currently being used by reconstructive microsurgeons to evaluate free-tissue-transfer procedures. To facilitate collection of relevant and complete data, the authors propose a standardized format for data collection regarding these procedures. Data are collected via computer entry or scannable forms. The database includes sociodemographic, clinical, health/functional status, patient satisfaction, and resource utilization variables--the necessary components of a well-constructed clinical outcome study. Such studies will give rise to meaningful treatment algorithms for managing reconstructive problems. In addition, widespread use of a standardized databse will facilitate comparisons between practices and allow for meta-analyses. Resultant practice guidelines and microsurgery care maps will ultimately improve patient care and minimize unnecessary costs. 相似文献