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   604篇
  免费   3篇
化学工业   10篇
金属工艺   3篇
机械仪表   1篇
建筑科学   3篇
轻工业   8篇
水利工程   2篇
石油天然气   2篇
一般工业技术   2篇
冶金工业   576篇
  2020年   1篇
  2018年   2篇
  2015年   2篇
  2014年   1篇
  2013年   3篇
  2012年   4篇
  2011年   2篇
  2009年   1篇
  2006年   1篇
  2005年   1篇
  2003年   1篇
  1999年   18篇
  1998年   181篇
  1997年   107篇
  1996年   71篇
  1995年   36篇
  1994年   28篇
  1993年   24篇
  1992年   3篇
  1991年   6篇
  1990年   4篇
  1989年   8篇
  1988年   9篇
  1987年   3篇
  1986年   2篇
  1985年   6篇
  1983年   3篇
  1982年   6篇
  1981年   1篇
  1980年   7篇
  1979年   1篇
  1978年   5篇
  1977年   15篇
  1976年   36篇
  1975年   2篇
  1971年   1篇
  1970年   1篇
  1967年   1篇
  1963年   2篇
  1940年   1篇
排序方式: 共有607条查询结果,搜索用时 15 毫秒
31.
The authors evaluate in the submitted paper the results of surgical treatment of embolization into the bifurcation of the abdominal artery at the Second Surgical Clinic in Brno during 1990-1996. A total of 5 patients was involved whereby in all a cardiac cause of the embolization was obvious. The authors deal also with the time which has elapsed between the development of complaints and surgery, the type of anaesthesia, average length of operation. The operation is implemented concurrently by two teams as antero- and retrograde simultaneous bi-transfemoral embolectomy. The authors emphasize the importance of the metabolic condition of the patient as well as cardiac and renal functions before, during and after surgery. They consider the application of peroperative haemodialysis essential. During the postoperative period it is important to find the objective cause of the cardiac deficiency and treat it. Their results--a 40% mortality are comparable with those of other specialized departments. By comparison with a similar group treated at the same department twenty years previously the authors find a decline in the incidence of this disease and explain this phenomenon by an increased number of cardiosurgical operations in this area.  相似文献   
32.
To evaluate chicken toxoplasmosis both as an economic and a public health subject, 84 broiler chicks of a commercial strain, 30 days old, were distributed into seven groups of 12 birds (three replications of four chicks) experimentally infected with three developing T. gondii stages of the P strain as follows: tachyzoites, intravenous (two groups: 5.0 x 10(5) and 5.0 x 10(6)), cysts, per os (two groups: 1.0 x 10(2) and 1.0 x 10(3)) and oocysts, per os (three groups: 5.0 x 10(2), 5.0 x 10(3) and 5.0 x 10(4)). Twelve chicks received only a placebo (control group). During the next 30 days the following parameters were estimated: productivity (weight gain and feed conversion), clinical signs, including rectal temperature and parasitemia (bioassay). No clinical signs suggesting toxoplasmosis were seen and no statistical differences on productivity standards were found in comparison between inoculated and control chicks. However, fowls inoculated with tachyzoites and oocysts occasionally showed hyperthermia. Some haematological changes were detected in fowls inoculated with T. gondii. Anatomo-histopathological changes were not observed. From 14 parasitemias detected, 35.7% appeared on the 5th day after inoculation and 57.1% of them resulted from oocysts inoculation. After 30-35 days all birds were slaughtered: fragments from 12 organs or tissues from each of them were subjected to artificial peptic digestion and after that injected into T. gondii antibody-free mice (IIFR). T. gondii was detected in brain (12), pancreas (five), spleen (five), retina (five), kidney (two), heart (four), proventriculus (three), liver (two), intestine (two), lung (one), and skeletal muscle (one). Similar to observations with parasitemia, from 42 T. gondii isolations, 59.5% came from chicks which had received oocysts. It can thus be inferred that the developing form, expelled by cats, is the most important for T. gondii chicken infection and that brain is the most infected organ in birds. Attention must be paid to the potential importance of chicken meat in public health, since T. gondii was isolated from skeletal and heart muscles.  相似文献   
33.
PURPOSE: To evaluate neutron irradiation alone and with chemotherapy to treat inoperable pancreatic cancer. MATERIALS AND METHODS: Between 1977 and 1994, 173 patients (60 men, 113 women, aged 43-77 years [mean, 59 years]) with unresectable adenocarcinoma of the exocrine pancreas were treated, 106 with neutron irradiation alone and 67 with concomitant chemotherapy (fluorouracil [5-FU]). At follow-up, which was performed at 2-month intervals until death (range, 4-64 months), clinical status was recorded, noting the presence of overt metastasis and the onset of any major complications. Actuarial (Kaplan-Meier) survival tables were computed for both groups. RESULTS: For neutron irradiation alone and neutron irradiation plus chemotherapy, median survival times were 6 months and 9 months, respectively; actuarial survival rates at 3 years were 0 and 7%, respectively; major reactions (grade 3 or higher [scale of the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer]) occurred in 19 (18%) and 17 (25%) patients, respectively; and severe complications (grade 4) occurred in five (5%) and four (6%) patients, respectively. Most deaths were due to metastatic disease rather than to failure of local control. CONCLUSIONS: Neutron irradiation obliterated pancreatic adenocarcinoma at the primary site but has no effect on long-term survival. With more effective concomitant chemotherapy to prevent metastasis, local control of pancreatic cancer with neutron irradiation could lead to increased long-term survival.  相似文献   
34.
35.
The mitogenic activities of low (LDL)- and high (HDL)-density lipoproteins have been examined in cultures of human vascular smooth muscle cells (VSMC). LDL and HDL3 dose-dependently (EC50 values approximately 50 micrograms/ml) stimulated DNA and protein synthesis ([3H]-thymidine and [3H]-leucine incorporation, respectively) in the absence of exogenously added mitogens. The synthetic responses of VSMC to combinations of LDL and HDL3 were additive, indicating that each lipoprotein mediates discrete effects. LDL or HDL3 promoted VSMC proliferation under strict mitogen-free conditions, but this growth response was not sustained. VSMC exposed to combinations of lipoproteins (either LDL or HDL3) and growth factors (either PDGF-BB, EGF, bFGF or IGF) exhibited synergistic DNA synthesis responses. In the combined presence of PDGF-BB and either LDL or HDL3, VSMC proliferation was sustained. Anionized lipoprotein preparations (oxidized, acetylated, carbamylated or malonimylated) also stimulated DNA and protein synthesis. Since the antioxidant beta-hydroxylated toluene did not block the effect of native LDL on DNA synthesis, and fucoidin, a specific competitor for the 'scavenger' receptor, did not inhibit oxidized LDL-induced DNA synthesis, activation of mitogenic signals by lipoproteins does not depend on lipid peroxidation. Rather, the apparent intrinsic mitogenic potential of lipoproteins may depend upon their direct activation of replication-coupled signal transduction systems.  相似文献   
36.
A major challenge for the toxicologist involved in safety evaluation of chemical mixtures is to test the hypothesis that as a rule exposure to mixtures of chemicals at (low) non-toxic doses of the individual chemicals is of no health concern. A series of repeated dose studies in rats with defined mixtures of chemicals with the same or different target organs revealed that exposure to a combination of chemicals compared with exposure to the individual compounds did not constitute an evidently increased hazard, provided each chemical was administered at a level similar to, or slightly lower than, its own 'No-Observed-Adverse-Effect-Level'. The results of subacute oral toxicity studies in rats with defined mixtures of nephrotoxicants with similar mode of action underlined the applicability of the additivity assumption for a mixture of chemicals with simple similar action. Safety evaluation of complex chemical mixtures is a challenge that can be tackled as follows: first, identify the (e.g. ten) most risky chemicals in the mixture, and, second, assess the hazard and the potential health risk of the mixture of the most risky chemicals, using procedures developed for defined mixtures. To identify interactions between individual compounds, a most promising testing strategy appeared to be a statistical approach using a fractional two-level factorial design. A challenge for today and the future is to gradually substitute mixture-oriented (real life-oriented) standard setting for (unrealistic) single chemical-oriented standard setting.  相似文献   
37.
The authors present an account on a gunshot wound which penetrated into the lateral side of the distal chest on the right. They describe acute treatment of severe haemorrhagic shock by suture of a lacerated with liver segment and resection of the upper pole of the right kidney. The projectile was not searched for because of the patients general serious condition. After 30 days the patient was discharged in a good condition. Shortly after discharge, i.e. cca one month after the injury, the patient developed signs of chronic ischaemia of the left lower extremity-finally claudications after 150 meters. Based on peripheral arteriography, which revealed the projectile in the area of the beginning of the superficial femoral artery and an ample collateral circulation, surgery was initiated. The bullet was extracted from the lumen of the superficial femoral artery from longitudinal arteriotomy. The artery was then treated by thrombectomy and a venous patch. Peroperative arteriography indicates satisfactory passage into the periphery. The authors try to reconstruct the pathway of the shot and in particular how the projectile penetrated into the artery. They emphasize the necessity to look for the projectice at the site of the shot wound. The objective of the paper is to make readers familiar with a case of uncommon embolization of a projectile into the superficial femoral artery and mistakes which may occur during treatment of a gunshot wound. The result is that the patient is quite free from complaints, as was confirmed by repeated out-patient check-ups.  相似文献   
38.
Rosai-Dorfman disease, or sinus histiocytosis with massive lymphadenopathy (SHML), is a benign, self-limited pseudolymphomatous entity with characteristic histologic features. The disease may be atypically present in the absence of detectable nodal involvement. This is a case of nasal septum involvement of Rosai-Dorfman disease without clinically apparent lymphadenopathy.  相似文献   
39.
The microinjection of carbachol into the nucleus pontis oralis produces a state which is polygraphically and behaviorally similar to active sleep (rapid eye movement sleep). In the present study, using double-labeling techniques for serotonin and the protein product of c-fos (Fos), we sought to examine whether immunocytochemically identified serotonergic neurons of the raphe nuclei of the cat were activated, as indicated by their expression of c-fos, during this pharmacologically-induced behavioral state (active sleep-carbachol). Compared with control cats, which were injected with saline, active sleep-carbachol cats exhibited a significantly greater number of c-fos-expressing neurons in the raphe dorsalis, magnus and pallidus. Whereas most of the c-fos-expressing neurons in the raphe dorsalis were small, those in the raphe magnus were medium-sized and in the raphe pallidus they were small and medium-sized. The mean number of serotonergic neurons that expressed c-fos (i.e. double-labeled cells) was similar in control and active sleep-carbachol cats. These data indicate that there is an increased number of non-serotonergic, c-fos-expressing neurons in the raphe dorsalis, magnus and pallidus during the carbachol-induced state.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
40.
To determine whether racial differences exist in psychosocial variables among patients with non-insulin-dependent diabetes mellitus (NIDDM), the authors administered a series of questionnaires to 211 Black and White patients of the Wake Forest Family Medicine ambulatory care unit and the Reynolds Health Center, a community health center. In general, Blacks in the study population had higher levels of external locus of control, higher levels of stress, and lower levels of family functioning compared with Whites. These differences may account partially for the disparity of diabetes control and the consequences of diabetes among Blacks. Health professionals may benefit from understanding and addressing these psychosocial variables and may be more successful in implementing intervention programs in this population by tailoring programs to the psychosocial orientation of their population.  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