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   249篇
  免费   0篇
化学工业   23篇
建筑科学   1篇
矿业工程   1篇
能源动力   2篇
轻工业   5篇
水利工程   1篇
无线电   15篇
一般工业技术   8篇
冶金工业   189篇
自动化技术   4篇
  2022年   5篇
  2020年   2篇
  2019年   2篇
  2018年   3篇
  2016年   2篇
  2013年   6篇
  2012年   4篇
  2011年   2篇
  2009年   3篇
  2008年   1篇
  2006年   2篇
  2005年   1篇
  2004年   2篇
  2003年   2篇
  2000年   1篇
  1999年   4篇
  1998年   53篇
  1997年   30篇
  1996年   26篇
  1995年   13篇
  1994年   7篇
  1993年   12篇
  1992年   2篇
  1991年   3篇
  1990年   3篇
  1989年   2篇
  1986年   1篇
  1985年   3篇
  1983年   1篇
  1982年   2篇
  1981年   3篇
  1980年   1篇
  1979年   4篇
  1978年   1篇
  1977年   8篇
  1976年   8篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1970年   2篇
  1968年   2篇
  1967年   1篇
  1964年   3篇
  1963年   1篇
  1962年   1篇
  1959年   2篇
  1957年   1篇
  1955年   1篇
  1944年   1篇
  1932年   2篇
排序方式: 共有249条查询结果,搜索用时 0 毫秒
141.
Publicity associated with recent reports of a greater frequency of adenocarcinoma of the endometrium among women who take exogenous estrogens has created confusion among physicians and fear among patients. An objective review of available data on estrogen effects and current epidemiologic evidence suggests that estrogen may play an indirect role in the development of endometrial carcinoma. Until definitive data are available, physicians should exercise caution in prescribing estrogens, monitoring the status of the endometrium at regular intervals by sampling and pathologic analysis.  相似文献   
142.
To reconcile past research based on reactance theory that found convergence of evaluations of alternatives prior to a choice, and research based on choice certainty theory that found divergence, it was proposed that convergence occurs in private evaluations. According to this interpretation, the freedom to choose a nonpreferred alternative is threatened by the overt expression of a preference that involves commitment but is not threatened by the private holding of a preference. Two experiments were conducted with 180 female undergraduates to test this interpretation. The studies used the procedure in which D. E. Linder and K. A. Crane (see record 1970-15980-001) and Linder et al (see record 1972-02217-001) found convergence of overtly expressed evaluations. The present experiments found divergence when evaluations were made privately; that is, supposedly without the experimenter being aware of the nature of the evaluations. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
143.
The concentration of alkaline phosphatase in cervical mucus was serially determined during a menstrual cycle in five normal ovulatory women and correlated with the time of ovulation as monitored by the basal body temperature and radioimmunoassay of serum lutenizing hormone (LH), progesterone, and estradiol. The activity of alkaline phosphatase decreased significantly at midcycle just prior to the LH surge and began to rise after ovulation. Self-detection of cervical mucus alkaline phosphatase may provide a practical method of ovulation prediction.  相似文献   
144.
Interpersonal attraction in exchange and communal relationships.   总被引:1,自引:0,他引:1  
Communal relationships, in which the giving of a benefit in response to a need for the benefit is appropriate, are distinguished from exchange relationships, in which the giving of a benefit in response to the receipt of a benefit is appropriate. Based on this distinction, it was hypothesized that the receipt of a benefit after the person has been benefited leads to greater attraction when an exchange relationship is preferred and decreases attraction when a communal relationship is desired. These hypotheses were supported in Exp I, which used 96 male undergraduates. Exp II, which used a different manipulation of exchange vs communal relationships with 80 female undergraduates, supported the hypotheses that (a) a request for a benefit after the S is aided by the other leads to greater attraction when an exchange relationship is expected and decreases attraction when a communal relationship is expected, and (b) a request for a benefit in the absence of prior aid from the other decreases attraction when an exchange relationship is expected. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
145.
The development of affordable, effective, and environmentally friendly barrier fabrics is a current goal in antimicrobial textile development. The discovery of new routes to achieve non-toxic naturally occurring molecules with antimicrobial activity is of interest in the development of materials that promote wound healing, improve hygiene, and offer protection against nosocomial infection. Highly cleaned and sterile unbleached cotton has constituents that produce hydrogen peroxide at levels commensurate with those that favor cell signaling in wound healing. Here, we show the antimicrobial and antiviral properties of spunlaced griege cotton-containing nonwovens treated with ascorbic acid formulations. The mechanism of action occurs through the promotion of enhanced hydrogen peroxide activity. The levels of hydrogen peroxide activity afford antimicrobial activity against Gram-negative and Gram-positive bacteria and antiviral activity against MS2 bacteriophages. Spun-bond nonwoven unbleached cotton was treated with ascorbic acid using traditional pad-dry-cure methods. An assessment of antibacterial and antiviral activity against Staphylococcus aureus, Klebsiella pneumoniae, and MS2 bacteriophages with the AATCC 100 test method showed a 99.99% inhibitory activity. An approach to the covalent attachment of ascorbic to cellulose through citric acid crosslinking chemistry is also discussed. Thus, a simple, low-cost approach to antimicrobial and antiviral cotton-based nonwovens applicable to dressings, nosocomial barrier fabrics, and face masks can be adopted by combining ascorbic acid with spunlace greige cotton nonwoven fabrics.  相似文献   
146.
147.
The ideal correlation properties of single user code division multiple access (CDMA) systems with complementary codes (CC) are lost by multiple access interference and near–far effects in downlink frequency selective fading channels. This severity in interference has motivated to develop ways to overcome the threats with suitable suboptimal interference cancellation schemes. In this paper, we propose successive interference cancellation (SIC) for downlink CDMA systems with CC to improve the system capacity and reduce error rate under near–far situations. Theoretical study and extensive simulations were conducted to verify the effectiveness of proposed SIC under frequency selective Rician fading channels in achieving frequency diversity gain, close to theoretical lower bound in complementary coded CDMA (CC-CDMA) systems.  相似文献   
148.
In mobile communication, the most exploratory technology of fifth generation is massive multiple input multiple output (MIMO). The minimum mean square error and zero forcing based linear detectors are used in multiuser detection for MIMO single-carrier frequency division multiple access (SC-FDMA). When the received signal is detected and regularization sequence is joined in the equalization of spectral null amplification, these schemes experience an error performance and the signal detection assesses an inversion of a matrix computation that grows into complexity. Ordered successive interference cancelation (OSIC) detection is considered for MIMO SC-FDMA, which uses a posteriori information to eradicate these problems in a realistic environment. To cancel the interference, sorting is preferred based on signal-to-noise ratio and log-likelihood ratio. The distinctiveness of the methodology is to predict the symbol with the lowest error probability. The proposed work is compared with the existing methods, and simulation results prove that the defined algorithm outperforms conventional detection methods and accomplishes better performance with lower complication.  相似文献   
149.
Peptide–cellulose conjugates designed for use as optical protease sensors have gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with chronic illnesses, necessitating optimal biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Here, we examine a tripeptide, fluorogenic elastase biosensor attached to TEMPO-oxidized nanofibrillated cellulose via a polyethylene glycol linker. The synthetic conjugate was found to be active in the presence of human neutrophil elastase at levels comparable to other cellulose-based biosensors. Computational models examined the relationship of the sensor molecule to the transducer surface. The results illustrate differences in two crystallite transducer surfaces ((110) vs. (1−10)) and reveal preferred orientations of the sensor. Finally, a determination of the relative (110) vs. (1−10) orientations of crystals extracted from cotton demonstrates a preference for the (1−10) conformer. This model study potentiates the HNE sensor results for enhanced sensor activity design.  相似文献   
150.
Patients with end-stage sarcoidosis have now undergone lung transplantation successfully with good short-term and intermediate-term results. Lung transplantation for sarcoidosis requires several considerations unique to this disease. Selection of pulmonary sarcoidosis patients for transplantation requires that medical therapy has been exhausted. This may involve the use of corticosteriods and alternative medications. Causes of pulmonary dysfunction other than pulmonary sarcoidosis, such as bronchiectasis and myocardial sarcoidosis, must be excluded before candidates are considered for transplantation. The extent and severity of extrapulmonary disease must also be assessed and may preclude lung transplantation. The presence of mycetomas is considered a relative contra-indication by some transplant centres and an absolute contra-indication by others. Relatively few patients with pulmonary sarcoidosis have undergone transplantation and, therefore, there are few data on outcome. Sarcoidosis frequently recurs in the allograft, but rarely causes symptoms or pulmonary dysfunction. More severe acute rejection episodes may occur in sarcoidosis transplant recipients, although at present there is no evidence of an increased risk of obliterative bronchiolitis or increased mortality.  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