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   2852篇
  免费   8篇
  国内免费   1篇
电工技术   6篇
化学工业   53篇
金属工艺   57篇
机械仪表   6篇
建筑科学   23篇
矿业工程   2篇
能源动力   11篇
轻工业   20篇
水利工程   2篇
石油天然气   1篇
无线电   29篇
一般工业技术   66篇
冶金工业   2548篇
原子能技术   1篇
自动化技术   36篇
  2022年   4篇
  2019年   4篇
  2018年   6篇
  2017年   10篇
  2016年   5篇
  2015年   4篇
  2014年   9篇
  2013年   21篇
  2011年   13篇
  2010年   10篇
  2009年   17篇
  2008年   10篇
  2007年   11篇
  2006年   13篇
  2005年   10篇
  2004年   9篇
  2003年   10篇
  2002年   5篇
  2001年   6篇
  2000年   7篇
  1999年   91篇
  1998年   846篇
  1997年   497篇
  1996年   273篇
  1995年   171篇
  1994年   134篇
  1993年   148篇
  1992年   15篇
  1991年   22篇
  1990年   30篇
  1989年   39篇
  1988年   27篇
  1987年   37篇
  1986年   26篇
  1985年   23篇
  1984年   10篇
  1983年   9篇
  1982年   10篇
  1981年   21篇
  1980年   16篇
  1979年   4篇
  1978年   8篇
  1977年   53篇
  1976年   115篇
  1975年   10篇
  1973年   6篇
  1969年   4篇
  1968年   3篇
  1966年   3篇
  1955年   3篇
排序方式: 共有2861条查询结果,搜索用时 31 毫秒
151.
152.
153.
We report the 14th case of myelolipoma of the adrenal gland. Recommendations for appropriate diagnostic and therapeutic methods are made. Myelolipoma of the adrenal gland is a rare non-functioning tumor composed of lipoid and hematopoietic elements. The most consistent complaint is abdominal pain caused by hemorrhage within the tumor. We identified an association with obesity and hypertension. Ultrasound combined with computed tomography is useful in diagnosis. With expanded use of these studies, myelolipoma will be recognized more frequently. Definitive diagnosis and treatment are accomplished by simple excision; radical surgery is unnecessary.  相似文献   
154.
The clinical, surgical, and pathologic findings in a five year prospective study of 192 patients referred with a high probability of pancreatic cancer are reported. We have defined the requirements of any pancreatic imaging procedure as its ability to distinguish a normal pancreas from pancreatic cancer or chronic pancreatitis and the capability of detecting tumors less than 5 cm in diameter. There was a 47 percent incidence of pancreatic disease (27 percent pancreatic cancer and 20 percent chronic pancreatitis). Prospective radionuclide imaging as routinely performed was found to be of little clinical value in this patient population; it was neither specific nor sensitive to pancreatic cancer or chronic pancreatitis. Preliminary data with longitudinal multiplane emission tomography show an improved diagnostic accuracy and the ability to detect resectable tumors, but its efficacy needs to be prospectively compared with other screening tests on a carefully defined patient population.  相似文献   
155.
Twenty-four high-risk Ewing's sarcoma patients were treatedf on an intensive combined modality protocol including low-dose fractionated total body irradiation (TBI) and autologous bone marrow infusion (ABMI). Twenty patients (83%) achieved a complete clinical response to the primary and/or metastatic sites following induction therapy. The median disease-free interval was 18 months, and nine patients remain disease-free with a follow-up of 22 to 72 months. Local failure as a manifestation of initial relapse occurred in only three patients (15%), each having synchronous distant failure. Eight patients failed initially with only distant metastases, usually within 1-2 years following a complete clinical response. Two patients with a single metastasis were again rendered disease-free and remain free from second relapse with 18 and 30 months follow-up. No other relapsed patient was able to be rendered disease-free, and most died of progressive disease within 6 to 12 months of relapse. Two patterns of granulocyte recovery following consolidative therapy (include TBI) and ABMI were recognized. Seventeen patients reached a total granulocyte count of >500 cells/mm3 within 4 weeks of ABMI (early graulocyte recovery), while seven patients required >4 weeks from ABMI (late granulocyte recovery). The time of platelet recovery (>50,000/mm3) was different for the groups with early and late granulocyte recovery (25 days vs. 54 days, p <.001). Six of seven patients with late granulocyte recovery received locl high-dose irratiation to >1/2 pelvis prior to bone marrow storage. Patients with late recovery did not tolerate maintenance chemotherapy. However, there was no difference in disease-free and overall survival, when compaing the groups with early and late granulocyte recovery. We conclude that these high-risk Ewing's sarcoma patients remain a poor-prognosis group in spite of intensive combined modality therapy include low-dose TBI. The control of microscopic systemic disease remains the major challenge to improving the cure rate. A new combined modality protocol with high-dose 'therapeutic' TBI (800 rad/2 fractions) is being used and the protocol design is outlined.  相似文献   
156.
This paper discusses two cases of bilateral subcapital fracture of the proximal femur as a complication of myelography with Conray 60. The literature is reviewed.  相似文献   
157.
We experimentally examine the primary rainbow created by the illumination of a coated cylinder. We present a simple technique for varying the coating thickness over a wide range of values, and we see evidence for two different scattering regimes. In one, where the coating thickness is large, twin rainbows are produced. In the second, where the coating is thin enough to act as a thin film, a single rainbow is produced whose intensity varies periodically as the coating thickness varies. We find good agreement with previous theoretical predictions.  相似文献   
158.
There are a number of situations where the deformed configuration of a body is known and it is necessary to determine the reference state. Previous methods developed to calculate the reference state involve the formulation of the finite elasticity equations in terms of the deformed configuration. This paper demonstrates that the undeformed reference state can be accurately determined from a deformed configuration and the associated loading conditions, by using conventional finite elasticity balance equations together with a solution procedure that treats the reference configuration as the unknowns. The mathematical theory behind the solution method is described, validated with an analytical solution, and verified using experimental studies on gel phantoms. The practical utility of this method is then demonstrated in the field of breast biomechanics. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
159.
ABSTRACT

The kinetics of ligand exchange between bulk solution TBP and uranyl nitrate bound TBP in o-xylene has been investigated by 31P dynamic NMR spectroscopy. First order ligand exchange rate constant, k, and the activation energy for the uranyl nitrate-TBP system were determined from plots of transverse relaxation rates (In (l/τ)) versus reciprocal temperature (1/T). Using the Eyring equation, the average values of activation enthalpy, δH* (30.8±5.1 kJ-mole?1), and activation entropy, δS* (-109±19 J/mol-K) have been calculated. The negative entropy of activation value indicates an increase in order on proceeding from the reactants to the activated complex. Therefore, an associative mechanism may be proposed for the ligand exchange reaction between UO2(NO3)2 TBP2 and TBP. Equilibration of the extractant phase with 1.0 M HC1 did not change the ligand exchange rate constants or the activation parameters appreciably. These results are discussed in comparison with previous reports on TBP exchange rates for this system.  相似文献   
160.
The Al-Ni-Ti ternary system forms the basis of several alloy systems of practical importance. This study was undertaken to provide additional experimental thermodynamic data for the modeling of the Al-Ni-Ti system. High-temperature direct reaction calorimetry has been used to determine the standard enthalpy of formation of several Al-Ni-Ti alloys. The stability of the L21 structure over the B2 structure at the stoichiometric composition of Ni0.5Al0.25Ti0.25 was estimated from the enthalpy results to be 6.8 kJ/mol. The lattice parameters and melting temperatures of these compounds are also reported.  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