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   435篇
  免费   2篇
  国内免费   2篇
电工技术   3篇
综合类   3篇
化学工业   19篇
金属工艺   3篇
机械仪表   1篇
建筑科学   11篇
矿业工程   2篇
能源动力   5篇
轻工业   17篇
石油天然气   1篇
无线电   4篇
一般工业技术   17篇
冶金工业   343篇
自动化技术   10篇
  2019年   2篇
  2016年   2篇
  2015年   3篇
  2014年   3篇
  2013年   6篇
  2012年   2篇
  2011年   9篇
  2010年   5篇
  2008年   6篇
  2007年   9篇
  2006年   7篇
  2005年   4篇
  2004年   7篇
  2003年   3篇
  2002年   2篇
  2001年   2篇
  2000年   2篇
  1999年   12篇
  1998年   91篇
  1997年   49篇
  1996年   33篇
  1995年   19篇
  1994年   23篇
  1993年   23篇
  1992年   4篇
  1991年   5篇
  1990年   6篇
  1989年   6篇
  1988年   4篇
  1987年   5篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1982年   3篇
  1981年   1篇
  1980年   3篇
  1979年   4篇
  1978年   2篇
  1977年   8篇
  1976年   30篇
  1975年   2篇
  1974年   3篇
  1973年   1篇
  1972年   2篇
  1971年   3篇
  1969年   1篇
  1968年   3篇
  1967年   1篇
  1943年   1篇
  1928年   1篇
排序方式: 共有439条查询结果,搜索用时 15 毫秒
91.
92.
A client-oriented, team-based approach for teaching system integration to undergraduate students at the United States Military Academy's Department of Electrical Engineering and Computer Science has proved highly effective. The two-semester course gives them their first real research and development experience in a carefully monitored and guided environment that translates theory into product. This experience helps demonstrate how students can become what employers seek and how educational institutions can provide what society needs.  相似文献   
93.
Nonfamous names presented once in an experiment are mistakenly judged as famous 24 hr later. On an immediate test, no such false fame occurs. This phenomenon parallels the sleeper effect found in studies of persuasion. People may escape the unconscious effects of misleading information by recollecting its source, raising the criterion level of familiarity required for judgments of fame, or by changing from familiarity to a more analytic basis for judgment. These strategies place constraints on the likelihood of sleeper effects. We discuss these results as the unconscious use of the past as a tool vs its conscious use as an object of reflection. Conscious recollection of the source of information does not always occur spontaneously when information is used as a tool in judgment. Rather, conscious recollection is a separate act. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
94.
Two different approaches for treating response bias in the process-dissociation procedure were assessed: a multinomial approach proposed by A. Buchner et al (see record 1995-31816-001) and a dual-process, signal-detection approach proposed by A. P. Yonelinas et al (see record 1996-29360-001). The authors examined data presented by Buchner et al and found that, although the signal-detection-based model worked slightly better than the multinomial model, the data did not provide a strong test of either model. However, an examination of other recognition data showed that the multinomial model produced distorted estimates of recollection and familiarity, and it was unable to account for observed receiver operating characteristics (ROCs). In contrast, the dual-process, signal detection model produced unbiased estimates and was able to account for the observed ROCs. The authors also provide an overview of the general controversy surrounding the process-dissociation approach. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
95.
96.
Atypical expression of CD44 splice variants has been implicated in the progression of numerous tumors. This abnormal CD44 expression is presumed to result from gene alterations that cause tumorigenic transformation. Two tumor types that have been linked to specific gene alterations are schwannomas, which have mutations in the neurofibromatosis (NF) type 2 (NF2) gene, and neurofibromas, which characteristically possess NF type 1 (NF1) gene mutations. We examined CD44 expression in normal sciatic nerves, in schwannomas with confirmed NF2 mutations, and in neurofibromas and malignant peripheral nerve sheath tumor tissue and cell lines from NF1 patients. Compared to normal nerves, schwannomas express higher total levels of CD44 and additional splice variants, whereas CD44 expression in neurofibromas is unaltered. Malignant peripheral nerve sheath tumor tissue and cell lines express the CD44v6 epitope, which is not expressed by normal Schwann cells or by other Schwann cell tumors. These data indicate that altered CD44 expression correlates strictly with mutations in the NF2 but not NF1 gene and suggest that CD44v6 might be a marker for the malignant transformation of Schwann cells.  相似文献   
97.
BACKGROUND: It has previously been shown that a combination of erythromycin and benzoyl peroxide is superior to either ingredient when used alone in the treatment of acne. A clindamycin/benzoyl peroxide combination gel might have an advantage over erythromycin/benzoyl peroxide gel because the former does not require refrigeration after it is dispensed. OBJECTIVE: Our purpose was to determine the efficacy and safety of a combination clindamycin/benzoyl peroxide gel when compared with benzoyl peroxide, clindamycin, or vehicle gels. METHODS: In two double-blind, randomized, parallel, vehicle-controlled trials, patients were treated for 11 weeks with once-nightly application of one of the above preparations. Evaluations were performed at 2, 5, 8, and 11 weeks and included lesion counts and assessment of global responses and irritant effects. RESULTS: A total of 334 patients completed the study. All three active preparations were significantly superior to the vehicle in global improvement and in reducing inflammatory lesions and noninflammatory lesions. The combination gel was significantly superior to the two individual agents in global improvement and reduction of inflammatory lesions and also to the clindamycin gel in reducing noninflammatory lesions. There was no significant difference in tolerance to the active gels versus the vehicle gel. CONCLUSION: In the treatment of acne, topical clindamycin/benzoyl peroxide combination gel is well tolerated and superior to either individual ingredient.  相似文献   
98.
Two experiments investigated a dating bias in which people tend to estimate recent dates too remotely and remote dates too recently. Experiment 1 examined and upheld a prediction of the hypothesis that bias arises because events whose time of occurrence is unknown are dated through associated events for which some time information is available. Experiment 2 required some subjects to date prototype events while others dated specific events. Prototype events were dated more recently, and the errors in dating specific events were related to differences in the way the prototype events were dated. Both sets of results were predicted by the association hypothesis, according to which events whose dates are well known are dated with reference either to specific associated events or to prototype events.  相似文献   
99.
This study focuses on dioleoylphosphatidylcholine (DOPC) bilayers near full hydration. Volumetric data and high-resolution synchrotron x-ray data are used in a method that compares DOPC with well determined gel phase dipalmitoylphosphatidylcholine (DPPC). The key structural quantity obtained is fully hydrated area/lipid A0 = 72.2 +/- 1.1 A2 at 30 degrees C, from which other quantities such as thickness of the bilayer are obtained. Data for samples over osmotic pressures from 0 to 56 atmospheres give an estimate for the area compressibility of KA = 188 dyn/cm. Obtaining the continuous scattering transform and electron density profiles requires correction for liquid crystal fluctuations. Quantitation of these fluctuations opens an experimental window on the fluctuation pressure, the primary repulsive interaction near full hydration. The fluctuation pressure decays exponentially with water spacing, in agreement with analytical results for soft confinement. However, the ratio of decay length lambda(fl) = 5.8 A to hydration pressure decay length lambda = 2.2 A is significantly larger than the value of 2 predicted by analytical theory and close to the ratio obtained in recent simulations. We also obtain the traditional osmotic pressure versus water spacing data. Our analysis of these data shows that estimates of the Hamaker parameter H and the bending modulus Kc are strongly coupled.  相似文献   
100.
Morphological analysis of the brains from 100 cases of full blown AIDS patients observed in the course of 1987-1995 years was performed. The material comprised 96 males, 3 females and 1 infant, 11 months old. Early material consisted almost exclusively of homo- and bisexuals, while in the last years heterosexual drug addicts prevailed. Gross brain examination revealed focal changes in 25% of cases, most of them being connected either with opportunistic infections or primary proliferating malignancies. Brain atrophy with an evident regional differences was observed macroscopically in 35 cases. Microscopic examination allowed detection of pathological changes in the brains of 87 cases, although in the remaining 13 cases there occurred some slight abnormalities taking the form of non-specific neuronal degeneration and loss, considered as resulting from perimortal cardio-pulmonary insufficiency or bleeding. Specific HIV-related changes in the form of HIV-encephalitis, HIV-encephalopathy or coexistence of both and HIV-leptomeningitis as well as HIV-vasculitis were present in 35 cases. They were accompanied by HIV-associated changes (vacuolar myelopathy, vacuolar leukoencephalopathy and selective poliodystrophy). Very seldom they appeared as independent pathological features and were characterized by very low frequency. Opportunistic infections composed the largest group of 59 cases. Proliferative malignancies occurred altogether in eleven cases, 10 of which were primary and secondary brain lymphomas. One case of Kaposi sarcoma completed the neoplastic series. Sixteen cases revealed various types of brain pathology such as hepatogenic encephalopathy, traumatic cortical scars, central pontine myelinolysis etc. The 59 cases of opportunistic infections consisted of a wide spectrum of viral and bacterial as well as fungal and protozoan infections. Among viral infections cytomegalovirus encephalitis was the most common, way ahead the progressive multifocal leukoencephalopathy. The second in frequency among opportunistic infections was brain toxoplasmosis and some fungal infections such as cryptococcosis and aspergillosis. Bacterial infections were in fact limited to tuberculosis, taking the form of granulomatous leptomeningitis with severe vascular pathology and/or tuberculoma formation. Many pathological processes appearing in a single case was characteristic feature of our collection. There was coexistence of HIV-specific CNS pathology and opportunistic infections, malignant neoplastic growth and other types of pathology. Various opportunistic infections coexisted without HIV-specific changes as well as malignant proliferation with opportunistic infections. Similarities and differences of our series were compared with data characterizing other, earlier collections of NeuroAIDS.  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