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   2404篇
  免费   24篇
  国内免费   1篇
电工技术   22篇
综合类   2篇
化学工业   108篇
金属工艺   7篇
机械仪表   15篇
建筑科学   24篇
能源动力   25篇
轻工业   81篇
水利工程   5篇
石油天然气   3篇
无线电   211篇
一般工业技术   93篇
冶金工业   1752篇
原子能技术   3篇
自动化技术   78篇
  2020年   8篇
  2019年   5篇
  2018年   5篇
  2017年   9篇
  2016年   7篇
  2015年   7篇
  2014年   9篇
  2013年   28篇
  2012年   14篇
  2011年   25篇
  2010年   28篇
  2009年   28篇
  2008年   24篇
  2007年   37篇
  2006年   18篇
  2005年   21篇
  2004年   16篇
  2003年   19篇
  2002年   23篇
  2001年   15篇
  2000年   12篇
  1999年   58篇
  1998年   502篇
  1997年   300篇
  1996年   194篇
  1995年   116篇
  1994年   120篇
  1993年   132篇
  1992年   27篇
  1991年   36篇
  1990年   49篇
  1989年   41篇
  1988年   45篇
  1987年   37篇
  1986年   25篇
  1985年   18篇
  1984年   14篇
  1983年   17篇
  1982年   13篇
  1981年   23篇
  1980年   29篇
  1979年   8篇
  1978年   13篇
  1977年   55篇
  1976年   112篇
  1975年   16篇
  1974年   9篇
  1973年   8篇
  1972年   7篇
  1969年   6篇
排序方式: 共有2429条查询结果,搜索用时 437 毫秒
91.
Myelotoxicity is the dose-limiting factor in radioimmunotherapy. Traditional methods most commonly used to estimate the radiation adsorbed dose to the bone marrow of patients consider contributions from radionuclide in the blood and/or total body. Targeted therapies, such as radioimmunotherapy, add a third potential source for radiation to the bone marrow because the radiolabeled targeting molecules can accumulate specifically on malignant target cells infiltrating the bone marrow. A non-invasive method for estimating the radiation absorbed dose to the red marrow of patients who have received radiolabeled monoclonal antibodies (MoAb) has been developed and explored. The method depends on determining the cumulated activity in three contributing sources: 1) marrow; 2) blood; and 3) total body. The novel aspect of this method for estimating marrow radiation dose is derivation of the radiation dose for the entire red marrow from radiation dose estimates obtained by detection of cumulated activity in three lumbar vertebrae using a gamma camera. Contributions to the marrow radiation dose from marrow, blood, and total body cumulated activity were determined for patients who received an I-131 labeled MoAb, Lym-1, that reacts with malignant B-lymphocytes of chronic lymphocytic leukemia and nonHodgkin's lymphoma. Six patients were selected for illustrative purposes because their vertebrae were readily visualized on lumbar images. The radiation doses to the marrow contributed by nonpenetrating emissions in the marrow blood and penetrating emissions in the total body were similar in these patients with a mean of 0.2 and 0.3 rads per administered mCi from the blood and total body, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
92.
The records of 60 patients with gallbladder carcinoma (GBC) operatively treated between 1966 and 1993 at Belen Hospital, Trujillo, Perú, were retrospectively reviewed. The ratio of men to women was 1:7.5 and the average of age was 61 years. The accuracy of ultrasonography and oral cholecystograms for the specific diagnosis was 21% and 0% respectively. The surgical procedures employed were simple cholecystectomy (n = 56), right hepatectomy (n = 2). Whipple operation (n = 1) and extended cholecystectomy (n = 1), and our resectability rate for GBC is currently 50%. Simple cholecystectomy was a potentially curative surgical procedure in patients with in situ cancer (stage O) and early GBC (stage 1). In hospital mortality was 11.6% and 5-year survival rate for the total series was 15%. Gallstones were present in 95% of patients and most tumors (58%) had grown by diffuse infiltration or were associated with empyema (38%). Tumor stage, depth of invasion, tumor grade histologic type were all predictive of patient outcome. This report reinforces the difficulty in diagnosis and the poor prognosis for patients with GBC. We hold the view that more radical approaches for invasive cancers will enhance the operative results.  相似文献   
93.
Ten families living in Shenyang city with multiple cases of essential hypertension were studied by HLA haplotype analysis. They were selected strictly in accordance with the methods of sibling pair analysis and lods analysis. The obtained ratio of HLA haplotype sharing among affected siblings were 28.6%(2): 52.4%(1): 19.0%(0), P > 0.9. It is indicated that the haplotype shared randomly among affected siblings. The results of Lods analysis were Q = 0.40, Lods = 0.046, Pr = 1.112. These results showed that there is no evidence of patients with essential hypertension susceptible to gene linked with HLA.  相似文献   
94.
A cephalometric study was conducted on 50 male and 54 female Sotho-Tswana children 11-16 years of age. The subjects were selected for excellence of occlusion and balance of facial proportions. Various analyses, including Steiner, Wits, and McNamara, were used for the evaluations. The mean measurements were compared with those of other Southern African Black groups and Caucasoids. Our study shows that cephalometric analyses for other groups cannot be used with confidence for the Sotho-Tswana people and our data provides norms for them.  相似文献   
95.
This study was undertaken to investigate the possible association between thrombosis and infection using an in vitro test model in which fresh bovine blood was recirculated through test conduits (3.5 mm inner diameter) containing stent-like devices. Anticoagulation was adjusted so that the recirculating blood deposited thrombi on the stent to cause gradual occlusion, thus impeding the flow. Four stent-like devices were placed in separate conduits in each experiment, and blood was recirculated with the help of pneumatically driven ventricles. Flow through these conduits was monitored by ultrasonic flow detection. To quantitate bacterial interaction with thrombi, Staphylococcus epidermidis (15E10(9)) was labeled with 111Indium-oxine and added to the blood. Experiments lasted until the flow in the test conduits dropped to 10% of the starting flow. During this recirculation, as flow gradually decreased, one stent was taken out when flow was still at 100%, the second at 75%, the third at 50%, and the fourth at 10% of the starting flow. The number of bacteria associated with the thrombus was measured by gamma counting. The following observations were made: 1) the amount of thrombus increased with time in all experiments (this was confirmed in separate experiments by using autologous 111Indium labeled platelets); 2) bacterial adhesion showed a concomitant increase as thrombus size increased (this was confirmed by using 111Indium labeled bacteria), and 3) bacterial incorporation into the thrombus occurred regardless of whether they were viable or pretreated with the antibiotic rifampin. These observations suggest that as thrombi develop, they may preferentially attract micro-organisms. This suggests that devices with adherent thrombi may have greater susceptibility for infection.  相似文献   
96.
The influence of the bolus injection rate of propofol on its cardiovascular effects has not been extensively studied. We therefore examined the influence of the injection rate of i.v. bolus doses of propofol on its acute cardiovascular effects and peak blood concentrations in seven chronically instrumented sheep. Each received i.v. propofol (200 mg) over 2 min (slow injection) and 0.5 min (rapid injection) on separate occasions in random order. The rapid injection was associated with more profound decreases in mean arterial blood pressure than slow injection (35.7% vs 23.7% maximal reductions from baseline, respectively; P = 0.02). There were no significant differences between the injection rates for peak reductions in myocardial contractility, increases in heart rate, or degree of respiratory depression. Concurrently, the rapid injections were associated with significantly higher arterial (26.9 vs 11.9 mg/L) propofol concentrations in a manner consistent with indicator dilution principles. There were no differences in the peak coronary sinus concentrations between the injection rates. We conclude that the rapid injection of propofol in the context of the induction of anesthesia produced significantly higher peak arterial propofol concentrations and suggest that it is these higher concentrations that produced relatively greater reductions in arterial blood pressure from rapid injections. Implications: Propofol is injected into a vein to initiate anesthesia. It can cause a rapid decrease in blood pressure, which may be dangerous to the patient. We examined the effect of rapid and slow injection rates of propofol in sheep and found that rapid injection caused a greater decrease in blood pressure. This was because rapid injection caused higher concentrations of propofol in the blood immediately after the injection. We believe that if the same processes occur in humans, there may be little advantage in injecting propofol rapidly.  相似文献   
97.
An experience is reported with solitary necrotic nodules of the liver, rare benign lesions described for the first time in 1983. Two patients were referred to our department because of the presence of hepatic lesions that radiology showed to be suspected secondary liver tumors. At laparotomy, both patients underwent liver resections because the lesions appeared to be malignant. Subsequent histological examination of the surgical specimens revealed that both were solitary necrotic nodules of the liver. These were the only solitary necrotic nodules found in a total of 840 operations carried out in our department since October 1981. Although they are completely benign, solitary necrotic nodules have a similar ultrasound pattern and radiological features to metastases and have been described in the literature during the follow-up of patients with other tumors. Uncertainty remains as to the etiology of these lesions, which still represent an occasional finding in liver surgery.  相似文献   
98.
Reports an error in the article "Choice Processing in Emotionally Difficult Decisions' by Mary Frances Luce, James R. Bettman, and John W. Payne (Journal of Experimental Psychology: Learning, Memory, and Cognition, 1997, Vol. 23, No. 2, pp. 384–405; see record 1997-03378-007). In Table 7 on page 396, the high conflict/low trade-off difficulty mean for the PATTERN variable was printed as -0.13, but the actual mean is 0.13. A portion of the original abstract follows: Extends the standard effort-accuracy approach to explaining task influences on decision processing by arguing that coping goals will interact with effort-minimization goals for negatively emotion-laden decision tasks. These coping goals may involve both a desire to process in a thorough, accurate manner and a desire to avoid particularly distressing aspects of processing. The authors hypothesized and found in 3 experiments that decision processing under increasing negative emotion both becomes more extensive and proceeds more by focusing on one attribute at a time. In particular, increased negative emotion leads to more attribute-based processing at the beginning of the decision process. The results are inconsistent with views that negative emotion acts only as an incentive or only as a source of decision complexity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
99.
Pelizaeus-Merzbacher disease (PMD) is a dysmyelinating disease resulting from mutations, deletions, or duplications of the proteolipid protein (PLP) gene. Distinguishing features of PMD include pleiotropy and a range of disease severities among patients. Previously, we demonstrated that, when expressed in transfected fibroblasts, many naturally occurring mutant PLP alleles encode proteins that accumulate in the endoplasmic reticulum and are not transported to the cell surface. In the present communication, we show that oligodendrocytes in an animal model of PMD, the msd mouse, accumulate Plp gene products in the perinuclear region and are unable to transport them to the cell surface. Another important aspect of disease in msd mice is oligodendrocyte cell death, which is increased by two- to threefold. We demonstrate in msd mice that this death occurs by apoptosis and show that at the time oligodendrocytes die, they have differentiated, extended processes that frequently contact axons and are expressing myelin structural proteins. Finally, we define a hypothesis that accounts for pathogenesis in most PMD patients and animal models of this disease and, moreover, can be used to develop potential therapeutic strategies for ameliorating the disease phenotype.  相似文献   
100.
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