首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3662篇
  免费   21篇
电工技术   24篇
化学工业   242篇
金属工艺   18篇
机械仪表   19篇
建筑科学   17篇
矿业工程   5篇
能源动力   38篇
轻工业   127篇
水利工程   7篇
石油天然气   3篇
无线电   92篇
一般工业技术   170篇
冶金工业   2798篇
原子能技术   5篇
自动化技术   118篇
  2021年   10篇
  2018年   8篇
  2017年   12篇
  2016年   13篇
  2014年   20篇
  2013年   41篇
  2012年   22篇
  2011年   62篇
  2010年   56篇
  2009年   34篇
  2008年   34篇
  2007年   38篇
  2006年   36篇
  2005年   26篇
  2004年   28篇
  2003年   31篇
  2002年   24篇
  2001年   24篇
  2000年   10篇
  1999年   92篇
  1998年   771篇
  1997年   451篇
  1996年   287篇
  1995年   178篇
  1994年   146篇
  1993年   190篇
  1992年   62篇
  1991年   39篇
  1990年   41篇
  1989年   54篇
  1988年   54篇
  1987年   60篇
  1986年   49篇
  1985年   57篇
  1984年   14篇
  1983年   18篇
  1982年   35篇
  1981年   34篇
  1980年   45篇
  1979年   12篇
  1978年   18篇
  1977年   84篇
  1976年   235篇
  1975年   30篇
  1974年   15篇
  1973年   9篇
  1972年   9篇
  1971年   9篇
  1970年   7篇
  1968年   6篇
排序方式: 共有3683条查询结果,搜索用时 15 毫秒
21.
22.
The clinical and cytogenetic data of the first patient proven to belong to the fifth Fanconi anemia complementation group are described. The Turkish boy presented with psychomotoric retardation, growth retardation, retarded bone age, brachycephaly, hypotelorism, epicanthus, syndactyly, brachydactyly, renal dystopia, and cryptorchism. In addition, an asymmetrical skeletal anomaly was seen with a double distal phalanx of the left thumb and hypoplasia of the right thumb. Typical hematological features of the disorder developed, at the age of 2.5 years, about 1 year after diagnosis. Cytogenetic studies confirmed the clinical diagnosis and revealed a spontaneous chromosomal instability and hypersensitivity to the cross-linking agents diepoxybutane and Trenimon. The findings in the patient, who is considered to be the standard for the fifth Fanconi anemia complementation group, are compared with data reported for other patients affected with Fanconi anemia.  相似文献   
23.
BACKGROUND: Arteriovenous malformations (AVMs) are an abnormal communication between arterial and venous structures. Pelvic AVMs have been infrequently described in the literature and represent an uncommon cause of a palpable pelvic mass. CASE: A case of pelvic AVM with ureteral obstruction occurred. The location and radiologic appearance of the AVM suggested a complex adnexal mass. During exploration and resection of the mass, significant bleeding was encountered. The diagnosis of AVM was made only retrospectively, with histologic examination of the specimen. CONCLUSION: AVMs are an uncommon and unique cause of pelvic pathology. Preoperative diagnosis will alert the surgeon as to the technically difficult resection that may be encountered and to the massive bleeding that can be associated with their removal.  相似文献   
24.
BACKGROUND: The presence of a genetic factor in the determination of leprosy has long been debated. This study tests whether the HLA-linked control of susceptibility to leprosy and/or for the types of leprosy could be confirmed. MATERIALS AND METHODS: In 15 multicase families, the method of DeVries et al., 1976, was used to detect nonrandom segregation of parental HLA haplotypes in their affected and healthy siblings. Linkage analyses, for two and three alleles were performed by the computer program LIPED: RESULTS: For the affected siblings, the segregations of the parental HLA haplotype were significantly nonrandom from the healthy parents and random from the affected parents, indicating that affected siblings were sharing their HLA haplotypes (segregated from the healthy parents) more than expected. The segregations to the healthy siblings from both the healthy and affected parents were random. Healthy siblings inherited the haplotypes shared among the leprosy siblings randomly as expected. There were excess DR2/DR2 homozygote individuals among tuberculoid siblings. The highest lod score was achieved when we considered our suggested three-alleles model for the susceptibility to the different types of leprosy. CONCLUSIONS: A closely HLA-linked gene on chromosome number 6 with multiple alleles (3 or more) in recombination fraction between 0.05 and 0.1 with 70 to 100% penetrance may be responsible for the susceptibility to the different types of leprosy, whereas the susceptibility to leprosy per se maybe the responsibility of non-HLA linked gene/s. DR2/DR2 homozygote individuals may be relatively at high risk of developing leprosy or tuberculoid leprosy.  相似文献   
25.
26.
27.
28.
Data from the Cancer Registry of Slovenia were used in a cohort study to determine whether the incidence of second primary cancers in patients with first primary breast cancer differs from the incidence expected in the general population. Special interest was given to long-term survivors. The expected numbers of second primary cancers were calculated by multiplying the number of appropriate person-years at risk by the corresponding age- and calendar-period-specific cancer incidence rates for women in Slovenia. The risk of a second primary cancer was expressed as the standardized incidence ratio (SIR). Of the 8,917 patients newly diagnosed in the period 1961-85 and followed-up to the end of 1994, 547 (6.2 percent) developed second primary cancers, whereas 410 (4.7 percent) were expected (SIR = 1.3, 95 percent confidence interval [CI] = 1.2-1.4). The risk was higher among younger patients. In long-term survivors, the risk was increased significantly for second primary cancer of the breast (SIR = 1.4, CI = 1.1-1.7), lung cancer (SIR = 1.6, CI = 1.1-2.3), melanoma (SIR = 2.7, CI = 1.5-4.4) and non-melanoma skin cancers(SIR = 2.0, CI = 1.6-2.4), corpus uteri cancer(SIR = 1.6, CI = 1.2-2.1), ovarian cancer(SIR = 2.3, CI = 1.7-3.0), and thyroid cancer (SIR = 2.5, CI = 1.2-4.6). Our results confirm the findings of several cohort studies carried out in Europe, the United States, and Japan, indicating that breast cancer patients should be monitored carefully for the occurrence of second primary cancers.  相似文献   
29.
General issues relating to the use of outcome and process data from the treatment of antisocial children to predict future childhood adjustment are examined. For outcome measures, it was assumed that variables based on direct observation of child behavior would provide a better predictor of long-term adjustment than would ratings by participant adults. Long-term adjustment measures consisted of police arrest and out-of-home placement data collected 2 years after treatment termination. Observation data collected at termination predicted future police arrest, but parent and teacher ratings did not. It was also hypothesized that measures of the processes thought to produce the changes in child antisocial behavior would serve as predictors of future adjustment. The data supported this hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
30.
Simple pseudo-steady state relations between the hydraulic and nozzle pressures of an injection molding machine were presented and verified experimentally. A simulation study was performed to evaluate the performance of simple controllers using dynamic models developed for the hydraulic and nozzle pressures. The controllers chosen were the discrete proportional, proportional-integral (PI), and proportional-integral-derivative (PID) types, tuned according to the ITAE criterion. The control of hydraulic pressure simulation showed that the PI controller had the best overall performance, whereas the result of nozzle pressure control loop simulation showed that the PID controller performance was better than that of the PI controller. All the controllers, in both loops, gave responses that were about an order of magnitude more rapid than the open loop response.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号