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   683篇
  免费   7篇
  国内免费   2篇
电工技术   1篇
综合类   1篇
化学工业   50篇
机械仪表   8篇
建筑科学   10篇
能源动力   2篇
轻工业   20篇
无线电   19篇
一般工业技术   81篇
冶金工业   472篇
自动化技术   28篇
  2021年   2篇
  2020年   4篇
  2019年   9篇
  2017年   5篇
  2016年   4篇
  2014年   5篇
  2013年   18篇
  2012年   10篇
  2011年   7篇
  2010年   6篇
  2009年   8篇
  2008年   8篇
  2007年   8篇
  2006年   7篇
  2005年   10篇
  2004年   10篇
  2003年   10篇
  2002年   12篇
  2001年   5篇
  2000年   7篇
  1999年   17篇
  1998年   145篇
  1997年   88篇
  1996年   55篇
  1995年   31篇
  1994年   29篇
  1993年   27篇
  1992年   2篇
  1991年   8篇
  1990年   8篇
  1989年   9篇
  1988年   10篇
  1987年   8篇
  1986年   11篇
  1985年   6篇
  1983年   3篇
  1982年   2篇
  1981年   7篇
  1980年   3篇
  1979年   1篇
  1977年   25篇
  1976年   30篇
  1975年   3篇
  1973年   1篇
  1968年   1篇
  1964年   1篇
  1957年   1篇
  1953年   1篇
  1946年   1篇
  1937年   1篇
排序方式: 共有692条查询结果,搜索用时 31 毫秒
61.
The paper is based on the analysis of 235 young and middle-age patients with non-traumatic cerebral hemorrhage. Tactics of treatment is determined for each group depending on bleeding localization in accordance with World Health Organization's classification (1981). Operative treatment is recommended for lateral site of hematomas of 25 cm3 and more signs of media structures dislocation of 5 mm and more. With the development of hypertension-hydrocephal syndrome surgical intervention is directed at its elimination and where possible at hematoma's ablation. The amount of operative interventions is limited in case of medial and mixed variants of hemorrhages especially when bleedings affect mesencephal structures. In conditions of a neurosurgical clinic a pharmacotherapy is used as an independent one, as a preparation for surgical treatment as well as during operation and in postoperative period.  相似文献   
62.
Ethinylestradiol (EE) has evident paradoxical effects on cancer risk for human breast and hepatic cancer which parallel in some respects its effects on estrogen-induced neoplasms in the hamster kidney and liver. EE has been shown to be only weakly carcinogenic in the hamster kidney, but the most potent carcinogenic estrogen in the hamster liver following prolonged treatment. Unexpectedly, when EE and potent carcinogenic estrogens, such as diethylstilbestrol (DES), 17beta-estradiol (E2) and Moxestrol (MOX), are administered concomitantly, estrogen-induced carcinogenesis in the kidney is completely prevented. In studying this novel finding, we found that, compared with E2 exposure alone, EE at 0.05 and 1.0 nM significantly (P < 0.001) inhibited the rise in proliferation of cultured primary hamster proximal renal tubular (PRT) cells in the presence of E2 (1.0 nM). Consistent with these findings, combined EE + DES treatment for 5.0 months reduced hamster kidney c-myc, c-fos and c-jun RNA expression to 43, 37 and 52%, respectively, compared with levels observed after DES treatment alone. Interestingly, TAM + DES treatment for the same period also resulted in the same low level of RNA expression of these proto-oncogenes. c-MYC, c-FOS and c-JUN protein products were comparably reduced after either EE + DES or TAM + DES treatment. It appears that c-fos expression and c-FOS protein levels in the hamster kidney were more responsive to TAM inhibition. These data demonstrate that EE possesses unique anti-tumorigenic properties in vivo in the hamster kidney. Additionally, the observed anti-estrogen-like effect of EE on cell proliferation of cultured PRT cells suggests that EE may interfere critically with estrogen receptor (ER)-mediated mitogenic pathway(s) affected by potent carcinogenic estrogens, thus preventing subsequent gene dysregulation and, hence, tumor development. Based on competition studies, the differential binding of EE to hamster kidney ER relative to that of the other estrogens (E2, DES, MOX) appears not to contribute to the prevention of estrogen carcinogenesis at this organ site by EE.  相似文献   
63.
Selective lesion of the serotoninergic system diminished the synaptic uptake of 3H-L-glutamic acid and 3H-DL-aspartic acid, as well as the Na+(-dependent) binding of 3H-L-glutamic acid in the cortex and the brain stem. The data obtained suggest an ability of the serotoninergic system to modify presynaptic processes in amino-acidergic neurons of the CNS.  相似文献   
64.
In 1984 the Dental Attitude Questionnaire (DAQ), an instrument for assessing various aspects of a person's attitude toward oral health care, was presented by STOCKWELL & BANTING. The DAQ consists of six content scales, Cynicism, Health Concern, Motivation, Oral Function, Social Aesthetic and Susceptibility, and two validity scales, Halo and Infrequency. A Dutch translation was presented in 1986 by HOOGSTRATEN & BROERS. In order to replicate the factor analysis on the original DAQ as reported by STOCKWELL & BANTING, the present study was undertaken. The results show a change in factor structure from a three factor solution to a two factor solution. A confirmatory factor analysis shows that the original three factor structure of the DAQ is not present in the data collected with the translated version. To account for this change, some possible reasons are discussed.  相似文献   
65.
Some epimeric 20-hydroxy, 20-oxime, 16 alpha, 17 alpha-, 17,20- and 20,21-aziridine derivatives of progesterone were synthesized and evaluated as inhibitors of human 17 alpha-hydroxylase/C17,20-lyase (P450(17) alpha) and 5 alpha-reductase (5 alpha-R). The reduction of 16-dehydropregenolone acetate (3a) was reinvestigated. NaBH4 in the presence of CeCl3 gave better stereo-selectivity for 20 beta-ol [20 alpha/20 beta-OH (4 alpha/4 beta) = 1/2.7] than LTBAH or the Meerwein-Pondroff method reported; reduction with Zn in HOAc formed exclusively 20 alpha-ol (4 alpha b). The 20 alpha- and 20 beta-hydroxy-4,16-pregnadien-3-one (9 alpha) and (9 beta) were synthesized from the alcohols 4 alpha b and 4 beta b. Several 20-oxime pregnadienes and 16 alpha, 17 alpha-, 17,20- and 20,21-aziridinyl-5-pregnene derivatives were also synthesized. LiAlH4 reduction of the 16-en-20-oxime (12b) yielded 20 (R)-(13a) and 20(S)-17 alpha,20-aziridine (13b) and 20(R)-17 beta,20-aziridine (14a). Several compounds inhibited the human P450(17) alpha with greater potency than ketoconzole. The 5 alpha-R enzyme assay showed that while (9 alpha) did not have any activity, (9 beta) and (3b) were potent 5 alpha-reductase (IC50 = 21 and 31 nM) inhibitors with activities similar to finasteride. The 20-oximes (17a) and (17b) were potent dual inhibitors for both 5 alpha-R (IC50 = 63 and 115 nM, compared to 33 nM for finasteride) and P450(17) alpha (IC50 = 43 and 25 nM, compared to 78 nM for ketoconazole).  相似文献   
66.
67.
This article describes the design of the trajectory generator for a robot programming system called Multi-RCCL, which is a package of “C” routines for doing real-time manipulator control in a UNIX environment. RCCL has been used successfully in developing robot control applications in numerous research and industry facilities over the last several years. One of its strongest features is the ability to integrate real-time sensor control into the manipulator task specification. RCCL primitives supply the trajectory generator with target points for motions in joint or Cartesian coordinates. Other primitives allow the code developer to specify on-line functions that can modify the target points, or possibly cancel motion requests, in response to various sensor or control inputs. The design requirements of the trajectory generator are that it be able to integrate these on-line modifications into the overall robot motion and provide a smooth path between adjacent motions even when sensor inputs make the future trajectory uncertain. © 1993 John Wiley & Sons, Inc.  相似文献   
68.
In simulating acute hypoxic hypoxia with the participation of male volunteers, the authors investigated the antihypoxic and antioxidative activity of metabolic drugs (jakton, amtizole succinate, nootropil, probucol, and a mixture which consists of jakton, amtizole succinate, and probucol). The pharmaceuticals were shown to have heterodirectional effects on lipid peroxidative processes. Drugs having a pronounced antioxidative activity (such as probucol and the mixture) promotes oxygen utilization during hypoxia and posthypoxic reoxygenation chiefly by the oxygenase pathway. This rearrangement of oxygen utilization processes caused an increase in human high-altitude resistance. The use of the above drugs is a promising trend in the development of an adaptative response to hypoxia in persons engaged in hazardous jobs.  相似文献   
69.
70.
Single state elastoplastic friction models   总被引:1,自引:0,他引:1  
For control applications involving small displacements and velocities, friction modeling and compensation can be very important. In particular, the modeling of presliding displacement (motion prior to fully developed slip) can play a pivotal role. In this paper, it is shown that existing single-state friction models exhibit a nonphysical drift phenomenon which results from modeling presliding as a combination of elastic and plastic displacement. A new class of single state models is defined in which presliding is elastoplastic: under loading, frictional displacement is first purely elastic and then transitions to plastic. The new model class is demonstrated to substantially reduce drift while preserving the favorable properties of existing models (e.g., dissipativity) and to provide a comparable match to experimental data  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