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   1492篇
  免费   1篇
化学工业   4篇
轻工业   3篇
一般工业技术   5篇
冶金工业   1481篇
  2015年   1篇
  2013年   2篇
  2012年   1篇
  2010年   1篇
  2008年   1篇
  2007年   1篇
  2006年   1篇
  2003年   4篇
  2000年   1篇
  1999年   35篇
  1998年   468篇
  1997年   277篇
  1996年   179篇
  1995年   91篇
  1994年   72篇
  1993年   84篇
  1992年   7篇
  1991年   23篇
  1990年   18篇
  1989年   17篇
  1988年   16篇
  1987年   26篇
  1986年   16篇
  1985年   13篇
  1982年   7篇
  1981年   14篇
  1980年   11篇
  1979年   2篇
  1978年   3篇
  1977年   24篇
  1976年   75篇
  1975年   1篇
  1955年   1篇
排序方式: 共有1493条查询结果,搜索用时 125 毫秒
31.
A large number of substituted chalcones have been synthesized and tested for antileishmanial and lymphocyte-suppressing activities. A subset of the chalcones was designed by using statistical methods. 3D-QSAR analyses using 67 (antileishmanial activity) and 63 (lymphocyte-suppressing activity) of the compounds for the training sets and 9 compounds as an external validation set were performed by using the GRID/GOLPE methodology. The Smart Region Definition procedure with subsequent region selection as implemented in GOLPE reduced the number of variables to approximately 1300 yielding 3D-QSAR models of high quality (lymphocyte-suppressing model, R2 = 0. 90, Q2 = 0.80; antileishmanial model, R2 = 0.73, Q2 = 0.63). The coefficient plots indicate that steric interactions between the chalcones and the target are of major importance for the potencies of the compounds. A comparison of the coefficient plots for the antileishmanial effect and the lymphocyte-suppressing activity discloses significant differences which should make it possible to design chalcones having a high antileishmanial activity without suppressing the proliferation of lymphocytes.  相似文献   
32.
33.
34.
AM Steves  SB Dowd  D Durick 《Canadian Metallurgical Quarterly》1997,25(2):86-97; quiz 103, 105
This is the second article of a four-part series on gerontology and its applications to the care of elderly patients in nuclear medicine. This article reviews anatomic and physiologic changes and pathology associated with aging. It also discusses tailoring nuclear medicine procedures according to patients' needs and conditions, as well as adopting changes within the nuclear medicine department to better serve older patients. Upon completion of this article, the reader should be able to: (a) describe normal age-related anatomic and physiologic changes that are observed in older patients; (b) identify common age-related disorders; (c) discuss considerations in tailoring nuclear medicine procedures for older patients; and (d) identify changes in the nuclear medicine facility that would better accommodate older patients.  相似文献   
35.
36.
The NADYA Group, integrated in the Spanish Society of Parenteral and Enteral Nutrition (SENPE), and made up of professionals dedicated to Artificial Nutrition, and specifically, to Artificial Nutrition in the home, annually undertakes the task of collecting data on diagnosis, type of support, follow up characteristics, complications, and quality of life, of patients included in programs of at home artificial nutrition in Spain. In the Annual Register corresponding to 1994, 17 hospitality groups have participated, providing 369 patients with Home Enteral Nutrition, and 30 with Home Parenteral Nutrition. Home Enteral Nutrition is mainly applied in patients with neoplasias (36%) or neurological alterations (35%). The most commonly used access route in the nasogastric tube, although there is an observed increase in the application of Percutaneous Gastrostomies (21%) in relation to previous data of the Spanish population. There is an observed complications index of 0.07 episodes/patient-year, a mortality of 30% (neoplasias) and 20% (neurological alterations), and low rehabilitation indexes in this group. In Home Parenteral Nutrition, post-radiation enteritis, neoplasias, and mesenteric ischemia, are the main diagnostic groups. The majority of the patients have a tunneled tube (63%), with 37% using an implanted tube. With an index of hospitalizations of 0.83 hospitalizations/ patient-year, catheter septicemia justifies the majority of the re-hospitalizations derived from nutritional treatment (0.56 hospitalizations/patient-year), note the mortality of 37%. There are complete rehabilitations, continuing the previously normal activity in 80% of the cases.  相似文献   
37.
38.
Using high-performance liquid chromatography, gas-chromatography and chromato-mass spectrometry methods a novel endogenous cyclic dipeptide cyclo-prolylglycine was identified in rat brain. Its content according to gas chromatography is 2.8 +/- 0.3 nmol/g wet brain. Synthetic cyclo-prolylglycine has demonstrated antiamnesic activity in the passive avoidance test in rats at a dose of 0.1 mg/kg i.p. Cyclic dipeptide cyclo-prolylglycine seems to be a memory facilitating substance and its presence in rat brain suggests the existence of a new mechanism of memory regulation.  相似文献   
39.
Simultaneous communications combines both spoken and manual modes to produce each word of an utterance. This study investigated the potential influence of alterations in the temporal structure of speech produced by inexperienced signers during simultaneous communication on the perception of final consonant voicing. Inexperienced signers recorded words that differed only in the voicing characteristic of the final consonant under two conditions: (1) speech alone and (2) simultaneous communication. The words were subsequently digitally edited to remove the final consonant and played to 20 listeners who, in a forced-choice paradigm, circled the word they thought they heard. Results indicated that accurate perception of final consonant voicing was not impaired by changes in the temporal structure of speech that accompanied the inexperienced signers' simultaneous communication.  相似文献   
40.
The efficacy of ultrasound compared with ascending venography for the detection of deep venous thrombosis immediately after total knee arthroplasty was assessed after a 2-year interval. One hundred thirty-seven patients were eligible for the study; however, 31 patients received only one of the screening methods and a color Doppler examination was inconclusive in six patients. Therefore, 100 patients had a Doppler examination and a venogram. Overall, the sensitivity of ultrasound was 85%, the specificity 97%, the positive predictive value 85%, the negative predictive value 97%, and the accuracy 95%. The sensitivity in the calf was 83%, in the popliteal vein 86%, and in the femoral vein 100%. Two years ago, the initial assessment of ultrasound for the detection of deep venous thrombosis after surgery in patients who had total joint arthroplasty revealed a 75% sensitivity, 99% specificity, 91% positive predictive value, 97% negative predictive value, and 97% accuracy. The sensitivity in the calf was 83%; the sensitivity in the popliteal vein was 40%; and the sensitivity in the femoral vein was 50%. After 2 years of using this screening test with one technician and one radiologist, an improvement with this noninvasive technique was shown. However, it was found that Doppler imaging is not as sensitive as venography for detecting calf thrombi. Any imaging technique should be validated by each institution to determine the validity of the instrument and the learning curve of the technician administering the examination.  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