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   1281篇
  免费   2篇
  国内免费   1篇
电工技术   4篇
化学工业   22篇
金属工艺   4篇
建筑科学   2篇
矿业工程   3篇
能源动力   2篇
轻工业   4篇
无线电   10篇
一般工业技术   8篇
冶金工业   1218篇
原子能技术   1篇
自动化技术   6篇
  2022年   4篇
  2018年   2篇
  2016年   2篇
  2015年   1篇
  2014年   3篇
  2013年   3篇
  2012年   1篇
  2010年   5篇
  2009年   2篇
  2008年   6篇
  2007年   3篇
  2006年   5篇
  2005年   5篇
  2004年   2篇
  2003年   5篇
  2001年   1篇
  2000年   5篇
  1999年   29篇
  1998年   326篇
  1997年   226篇
  1996年   158篇
  1995年   106篇
  1994年   61篇
  1993年   74篇
  1992年   7篇
  1991年   23篇
  1990年   8篇
  1989年   8篇
  1988年   5篇
  1987年   4篇
  1986年   3篇
  1985年   5篇
  1983年   3篇
  1982年   4篇
  1981年   11篇
  1980年   14篇
  1979年   1篇
  1978年   6篇
  1977年   47篇
  1976年   95篇
  1974年   1篇
  1972年   1篇
  1970年   1篇
  1968年   1篇
  1966年   1篇
排序方式: 共有1284条查询结果,搜索用时 15 毫秒
51.
Pulmonary diseases caused by dust occupy a leading place in occupational morbidity structure. Those diseases inspire much attention due to their high prevalence, especially in ecologically hazardous regions where the workers are under "double exposure". Upper respiratory tract diseases serve as a trigger for all respiratory disorders in workers exposed to dust. Early diagnosis of respiratory disorders includes history, clinical data, X-ray examination and assessment of pulmonary ventilation and together with concurrent cardiovascular diagnosis is necessary for well-justified prophylaxis.  相似文献   
52.
When initiating monotherapy for the treatment of essential hypertension, multiple determinants factor into the decision. The goal of treatment is to lower blood pressure and lessen the likelihood of progression to target organ failure. Physicians frequently prioritize these determinants and make decisions to initiate monotherapy based on the race of an individual. All too often, however, the black/white issue is overstated and given too much consideration. The overall goal of this review is to suggest the appropriate "role" for racial profiling in the initial selection of an antihypertensive agent.  相似文献   
53.
Chronic pelvic pain in the absence of organic pathology identifiable in medical terms is considered one of the most perplexing conditions that gynecologists confront. A critical analysis of the medical, psychiatric, and psychological literature on chronic pelvic pain without organic pathology reveals that the dichotomous construct of mind and body underpinning medical research and understanding is a barrier to the successful diagnosis and treatment of this condition, and indeed to the productive engagement of the health professional with the patient. The strict duality of the condition's etiology being understood in either physiological or psychogenic terms has been questioned at times over the last 40 years, but only recently has an "integrative model" been proposed. However, it is argued here that although the development of a multidisciplinary approach is important, only a radical deconstruction of the medical paradigm will truly address the problem and enable a real change in practice.  相似文献   
54.
The aim of the study was TPS diagnostic value determination in the serum of women with breast cancer as compared with MCA and CA 15-3. The relationship between the serum concentration of these antigens and patient age, clinical stage, histological grade, presence of metastases to lymph nodes and histological type of neoplasm was evaluated. Studies were conducted on the sera of 139 women before surgical procedure aged 28-81, treated in the Clinic of Oncology, at Karol Marcinkowski University of Medical Sciences in Poznań. The TPS concentration was determined using the "BEKI Diagnostics" immunoenzymatic method, MCA - by the "Roche" test and CA 15-3 concentration was determined by the "Abbott" immunofluorescent test. The study showed significantly higher levels of TPS, CA 15-3 and MCA in women with cancer, compared with values in healthy women and women with mastopathy. The highest median of concentration and frequency of occurrence was obtained for TPS. A correlation between enhancement of TPS and CA 15-3 concentration with clinical stage was observed. A similar connection was noted in women with metastases to the lymph nodes. Serum MCA concentration results did not demonstrate the above effects. The study suggests, that in estimating the clinical condition of women with breast cancer, the simultaneous determination of TPS with CA 15-3 seems to be a more useful prognostic factor than TPS or CA 15-3 with MCA.  相似文献   
55.
Personal clinical observations during the recent years allow the authors to confirm the indisputable value of surgical experience got during the Great Patriotic War (1941-1945) and in particular, the "fourfold" scheme proposed by V. I. Voiachek for the diagnosis and treatment of blind gunshot wounds to the skull base. Computed tomography considerably increases the probability of detection of the exact localization of foreign bodies in complex anatomical structures of the skull and thus facilitates choosing the most rational surgical management. The use of the electro-optical transducer for the extraction of foreign bodies from almost inaccessible areas of the skull base decreases the risk of operation.  相似文献   
56.
During a six-month period 2,221 haemocultures obtained from patients hospitalized in the Faculty Hospital Olomouc were examined. In all 304 isolated bacteria the sensitivity was assessed by the standard dilution micromethod and moreover all positive haemocultures were examined the "direct" disc method. Agreement between the results of the two methods was proved in 84% of pairs of tests and within a range from 67 to 100%, depending on the type of antimicrobial preparation. Based on these findings it may be stated that assessment of the sensitivity by the "direct" method agrees significantly with assessment of the sensitivity according to minimal inhibitory concentrations (MIC). In patients with septicaemia this procedure makes it possible to change empirical antibiotherapy by 24 hours sooner to aimed therapy.  相似文献   
57.
OBJECTIVES: To i) document the sensitivity and specificity of a combined scintigraphic/lactulose breath hydrogen test for small intestinal bacterial overgrowth and ii) investigate the validity of currently accepted definitions of an abnormal lactulose breath hydrogen test based on "double peaks" in breath hydrogen concentrations. METHODS: Twenty-eight subjects were investigated with culture of proximal small intestinal aspirate and a 10-g lactulose breath hydrogen test combined with scintigraphy. Gastroduodenal pH, the presence or absence of gastric bacterial overgrowth, and the in vitro capability of overgrowth flora to ferment lactulose were determined. RESULTS: Sensitivity (16.7%) and specificity (70.0%) of the lactulose breath hydrogen test alone for small intestinal bacterial overgrowth were poor. Combination with scintigraphy resulted in 100% specificity, because double peaks in serial breath hydrogen concentrations may occur as a result of lactulose fermentation by cecal bacteria. Sensitivity increased to 38.9% with scintigraphy, because a single rise in breath hydrogen concentrations, commencing before the test meal reaches the cecum, may occur in this disorder. Sensitivity remained suboptimal irrespective of the definition of small intestinal bacterial overgrowth used, the nature of the overgrowth flora, favorable luminal pH, the presence of concurrent gastric bacterial overgrowth, or the in vitro ability of the overgrowth flora to ferment lactulose. CONCLUSIONS: Definitions of an abnormal lactulose breath hydrogen test based on the occurrence of double peaks in breath hydrogen concentrations are inappropriate. Not even the addition of scintigraphy renders this test a clinically useful alternative to culture of aspirate for diagnosing small intestinal bacterial overgrowth.  相似文献   
58.
Angiotensin II (A II) and analogues were tested for their ability to restore electrical and mechanical activity to cardiac muscle preparations in which the fast Na+ channels had been inactivated by partial depolarization (22-27 mM K+) or by tetrodotoxin (TTX). The partially depolarized or TTX-blocked preparations were chosen because under these conditions electrical and mechanical responses are primarily Ca2+ -dependent. In depolarized rabbit right atria, A II restored spontaneous mechanical and electrical activity (measured by both intracellular and extracellular recording techniques). The frequency of action potential discharge was concentration-dependent; the threshold concentration of A II was 10(-10) M, the ED50 was 8 X 10(-9) M, and the maximum effect was observed at 5 X 10(-8) M. In contrast, depolarized guinea pig atria were insensitive to A II, Sar1-angiotensin II, and des-Asp1-angiotensin II, even at concentrations as high as 10(-5) M. Rabbit papillary muscle (TTX-blocked), embryonic (18-day) chick heart (partially depolarized) and chick heart reaggregates (TTX-blocked) responded similarly to rabbit atria in that A II (9.6 X 10(-7) M) restored both electrical and mechanical activity. We found that in these preparations the action of A II was unaffected by propranolol (5.0 X 10(-6) M to 5.0 X 10(-5) M) but was blocked by Mn2+ (10(-3) M), D-600 (1 X 10(-7) g/ml) and the specific A II antagonists Sar1-Ala8-angiotensin II (P-113) (5.0 X 10(-5) M) and Sar1-Ile8-angiotensin II (5.28 X 10(-5) M). We conclude that the positive inotropic effect of A II on the myocardium is due to its ability to increase transmembrane ion movements in or through the cell membrane. The ability of Mn2+ and D-600 to block this effect suggests that this ion movement is via the so-called "slow channels."  相似文献   
59.
Nutrient loads enter the lower Truckee River of western Nevada, affecting the growth of attached algae (periphyton) which causes depressed nighttime dissolved oxygen (DO) levels. The lower Truckee River is home to the endangered cui-ui and threatened Lahontan cut-throat trout, with DO standards being established to in part protect these species. Hydrodynamics, nutrient concentrations, periphyton biomass, and DO data spanning August 2000–December 2001 were used to calibrate and verify a modified version of the Water Quality Analysis Simulation Program Version 5 (WASP5). Under typical loading conditions the periphyton community is nitrogen limited, however nitrogen loading from an upstream wastewater treatment facility increased greatly during the analysis period due to approved site construction activities (discharge permit excursion) causing the periphyton community to temporarily become phosphorus limited. The developed modeling approach, with limited calibration, was able to accurately track dynamic system responses. Removing the impact of the noted discharge permit excursion resulted in a minimum computed DO value of 4.13?mg/L, occurring at the downstream end of the modeling domain on August 8, 2001. Additionally removing the impact of all nutrient loads from area agriculture resulted in a predicted minimum DO value of 4.54?mg/L, while also shifting its location significantly upstream and its timing to April 26, 2001. Meeting all prescribed DO standards required establishing a minimum in-stream flow value of 1.81?m3/s (64.0?ft3/s) downstream of Derby Dam.  相似文献   
60.
Pretreatment of mice with clofibrate (CFB) has been shown to protect against acetaminophen (APAP) hepatotoxicity. To determine if pretreatment with CFB prevents the toxicity of other model hepatotoxicants, male C57BL6J or CD-1 mice received 500 mg CFB/kg, i.p., daily for 10 days, and then were challenged with either 250 mg bromobenzene (BrB)/kg, 0.025 ml carbon tetrachloride (CCl4)/kg or 0.5 ml chloroform (CHCl3)/kg. Liver and kidney injury was assessed by plasma sorbitol dehydrogenase activity (SDH) and blood urea nitrogen (BUN), respectively and histopathology. Challenge with BrB significantly elevated plasma SDH activity in C57Bl6J mice. This was prevented in CFB pretreated mice receiving the same dose of BrB. Changes in BUN were not detected in either group of BrB treated mice. Similarly, pretreatment of male CD-1 mice with CFB significantly reduced CCl4-induced elevation in plasma SDH activity, with no BUN elevation detected in either group. CFB pretreatment also diminished elevation in plasma SDH activity produced by CHCl3 in CD-1 mice, while BUN was significantly elevated in both groups, indicating that CFB did not protect against CHCl3-induced nephrotoxicity. Histopathological examination of liver and kidney sections confirmed these results. This study shows that mice pretreated with CFB were protected from toxicity at 24 h after challenge with other model hepatotoxic agents besides APAP.  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