全文获取类型
收费全文 | 1112篇 |
免费 | 50篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 9篇 |
综合类 | 4篇 |
化学工业 | 193篇 |
金属工艺 | 21篇 |
机械仪表 | 24篇 |
建筑科学 | 26篇 |
矿业工程 | 8篇 |
能源动力 | 55篇 |
轻工业 | 32篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 125篇 |
一般工业技术 | 147篇 |
冶金工业 | 403篇 |
原子能技术 | 8篇 |
自动化技术 | 109篇 |
出版年
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 13篇 |
2019年 | 20篇 |
2018年 | 31篇 |
2017年 | 19篇 |
2016年 | 26篇 |
2015年 | 22篇 |
2014年 | 24篇 |
2013年 | 78篇 |
2012年 | 37篇 |
2011年 | 46篇 |
2010年 | 24篇 |
2009年 | 28篇 |
2008年 | 36篇 |
2007年 | 25篇 |
2006年 | 12篇 |
2005年 | 19篇 |
2004年 | 22篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 16篇 |
1998年 | 97篇 |
1997年 | 60篇 |
1996年 | 47篇 |
1995年 | 27篇 |
1994年 | 32篇 |
1993年 | 33篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 16篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1978年 | 11篇 |
1977年 | 18篇 |
1976年 | 40篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 7篇 |
排序方式: 共有1167条查询结果,搜索用时 414 毫秒
121.
Experiments were conducted to study the deposition of particles from suspensions flowing through packed beds. The experimental data obtained include both the initial and transient state particle collection. The initial collection efficiencies were compared with predictions based on existing theories. Agreement between experiments and predictions was generally good except for the case when significant repulsive force barrier exists between filter grains and particles. The transient state data obtained under the presence of unfavorable surface interactions show a steady decline in collection efficiency with time, which cannot be reconciled with any existing theories. 相似文献
122.
Experimental investigations of thermal bulk polymerization of styrene in pilot plants of different sizes have been performed. Each pilot plant is composed of a tubular recycle reactor, connected in series with a tubular reactor, both completely filled with Sulzer motionless mixers. Kinetic, reactor and viscosity models have been verified in a wide range of styrene conversions (up to 96%) temperatures (up to 210 °C) and polystyrene molar masses (up to 360 000). Scale-up studies were carried out which confirmed that multitubular reactors of special design can be applied for industrial polymerization process. 相似文献
123.
Atomic mobility and self-diffusion was studied by NMR for nanostructured liquid gallium and indium embedded into nanoporous matrices—porous glasses and artificial opals. Drastic increase in the correlation time of atomic mobility was found compared to the relevant bulk melts that depends on pore size. Additional alterations were observed at temperatures when confined melts were partially frozen. 相似文献
124.
B Alvestad HN Jenssen L Larun J Palner A R?sberg U Saetre 《Canadian Metallurgical Quarterly》1998,118(11):1718-1721
The objective of the study was to ascertain whether physical activity at the workplace reduces the amount of sick leave. The databases Medline and Spri-line, reference lists, and professional expertise were consulted for information on the subject. We included random controlled trials, and controlled trials studying the effect on sick leave of physical activity at the worksite. Four trials were identified, including one carried out in Norway. The small number of trials limits the value of any conclusions and highlights the need for more research. The results of the four trials do not indicate that physical activity at the workplace reduces sick leave. 相似文献
125.
Ching-Cheng Tien Tzuang C.-K.C. Peng S.T. Chung-Chi Chang 《Microwave Theory and Techniques》1993,41(9):1616-1624
This paper presents theoretical and experimental results for a finite-width conductor-backed coplanar waveguide (FW-CBCPW). The guiding characteristics of FW-CBCPW are investigated first by the rigorous method of mode matching. An FW-CBCPW through line is then placed within a test fixture commonly used in laboratories, and the scattering parameters of the through line are obtained theoretically by approximating the FW-CBCPW as a simple system of coupled transmission lines. Experimental results are shown to agree very well with the theoretical ones. In particular, the anomalous behavior observed in the transmission characteristic of the through line is related to the resonant phenomenon of the terminated side planes which are short-circuited at both input and output ends due to the test fixture. Finally, a technique of mode suppression in the side-plane regions is suggested for the improvement of signal transmission over a broad band of frequency spectrum. The effects of extra higher order modes on the transmission characteristics at high frequencies are also discussed 相似文献
126.
JC Lindegaard OS Nielsen FA Lundbeck A Mamsen HN Studstrup H von der Maase 《Canadian Metallurgical Quarterly》1996,77(6):883-890
OBJECTIVE: To identify prognostic factors for penile cancer and to evaluate the treatment strategy for early-stage disease, proposed recently by the European Board of Urology (EBU). PATIENT AND METHODS: The records of 82 patients consecutively referred to the uro-oncological centre at Aarhus University Hospital between 1965 and 1993 were reviewed. The importance of tumour stage, differentiation, patient age, local control and regional lymph node control were assessed using univariate and multivariate analyses. RESULTS: Cox multivariate analysis identified differentiation (odds ratio [OR] = 6.04), UJCC-1978 T-stage (OR = 1.88) and age (OR = 1.04) as independent prognostic variables for survival. Penile amputation in tumours < 4 cm in diameter improved local control but not survival. Regional control and survival were not significantly improved by prophylactic adenectomy. CONCLUSION: Differentiation, T-stage and age were prognostic factors for survival. The results support the EBU treatment strategy involving penis-conserving therapy and watchful waiting for early-stage disease. 相似文献
127.
CS Cable WC Rebhun SL Fubini HN Erb NG Ducharme 《Canadian Metallurgical Quarterly》1998,212(9):1442-1445
OBJECTIVE: To evaluate the association of physical examination and clinicopathologic findings with surgical findings in cattle with concurrent abomasal displacement and perforating ulceration, to determine short- and long-term survival rates in these cattle, and to determine whether degree of peritonitis (focal vs diffuse) influences survival rates. DESIGN: Retrospective study. ANIMALS: 21 cattle with concurrent abomasal displacement and perforating ulceration and 42 cattle with uncomplicated abomasal displacement. PROCEDURE: Information on signalment, stage of lactation, physical examination findings, clinicopathologic data, surgical diagnosis, procedure(s) performed, and necropsy findings were retrieved from medical records of all cattle included in this study. Differences between physical examination findings of cattle with concurrent disease and those of cattle with uncomplicated displacements were evaluated, as were differences between survival rates in cattle with focal versus diffuse peritonitis. RESULTS: Cattle with concurrent disease had a greater probability of having pneumoperitoneum and signs of abdominal pain identified on physical examination than did cattle with uncomplicated diseases. There was no relationship between clinicopathologic data and survival time. Short-term survival rate was 38%, and degree of peritonitis significantly influenced survival time in cattle with concurrent abomasal displacement and perforating ulceration. Long-term survival rate in these cattle was 14%. CLINICAL IMPLICATIONS: Cattle with concurrent displaced abomasum and perforating ulceration have a poor chance for survival. In addition to detection of displaced abomasum, physical examination findings that can help lead to a presurgical diagnosis of this syndrome are pneumoperitoneum and signs of abdominal pain. 相似文献
128.
AY Tien WW Eaton TE Schlaepfer IK McGilchrist R Menon R Powers E Aylward P Barta ME Strauss GD Pearlson 《Canadian Metallurgical Quarterly》1996,19(2-3):93-101
Much of the literature shows various regional structural brain abnormalities in schizophrenia, but the complexity and variability of brain makes it difficult to determine how these regions are related. Statistical methods which estimate factors underlying patterns of covariance have not been widely used, but could be useful for analyzing such complex data. We applied exploratory and confirmatory factor analysis procedures to specific cortical and subcortical regional brain volume measures from MRI data in 60 normal and 44 schizophrenic subjects. Basal ganglia, heteromodal cortical gray, and medial temporal lobe factors were present in both the normal and the schizophrenia groups. The factor structure observed in the normal group showed a high degree of bilateral symmetry which is present but disrupted in the schizophrenia group. In the bilateral data, the disruption is most pronounced with medial and lateral temporal lobe structures including entorhinal cortex and anterior and posterior superior temporal gyri. There was a significant correlation between the basal ganglia factor and the heteromodal cortical gray factor in the normal group that was not present in the schizophrenia group. In the unilateral data, left posterior superior temporal gyrus did not load onto any factor in the schizophrenia group. Confirmatory factor analyses showed significant differences between the two groups in factor structure. A number of specific brain regions are affected in schizophrenia, and structural relationships between groups of regions also are abnormal. The results suggest that heteromodal dorsolateral prefrontal and superior temporal cortical gray regions are structurally related, whereas inferior parietal cortical gray is less so. These results should be viewed as preliminary as the ratio of parameters to subjects was relatively low, and replication is needed. However, the results demonstrate the potential utility of latent structure methods such as factor analysis in study of complex relationships in neuropsychiatric data. 相似文献
129.
Accurate estimates of body weight can be useful in the evaluations of feeding programs, nutritional status and general health, and in calculation of dose levels (such as for anesthesia)-thus providing a valuable tool for captive elephant management. We used body measurements of 75 Asian elephants (Elephas maximus) to predict body weight. Weight, heart girth, height at the withers, body length, and foot-pad circumference were measured. All possible linear regressions of weight on one, two, three, or four body measurements were calculated. The highest correlation with a single measurement was that between heart girth and weight (R2 = 0.90). The data were also divided into age groups (1-13, 18-28, 29-39, and 40-57 yr), and all possible linear regressions were calculated for each group (there were no elephants aged 14-17 yr). Adding body length or pad circumference to heart girth resulted in a slight increase in R2. We conclude that body weight in Asian elephants can be predicted from body measurements and that heart girth is the best predictor. A second body measurement might improve predictive accuracy for some age groups. 相似文献
130.
KA Bucher AM Patterson RC Elston CA Jones HN Kirkman 《Canadian Metallurgical Quarterly》1976,66(9):854-858
In this review of 7,464 consecutive infants born at North Carolina Memorial Hospital, hemolytic disease from ABO incompatibility was found to be two to three times as common in black infants as in white infants. The statistical significance of the difference remained high as more restrictive criteria for ABO hemolytic disease were applied. ABO disease, serious enough to cause an indirect serum bilirubin of 15 mg/100ml or higher, had an incidence in black newborns as great as the incidence of Rh hemolytic disease in whites. In contrast, the general prevalence and severity of hyperbilirubinemia was not found to be higher in black newborns than in white infants. The difference cannot be attributed to differences in the prevalence of ABO blood groups between the two races. Policies of early discharge of newborns could be affected by the finding that ABO erythroblastosis is two to three times as common in black infants as in white infants. 相似文献