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   3458篇
  免费   1篇
化学工业   9篇
轻工业   9篇
石油天然气   1篇
无线电   1篇
一般工业技术   2篇
冶金工业   3436篇
自动化技术   1篇
  2019年   1篇
  2017年   1篇
  2013年   2篇
  2011年   3篇
  2010年   1篇
  2008年   1篇
  2006年   1篇
  2005年   1篇
  2004年   1篇
  2003年   4篇
  1999年   98篇
  1998年   938篇
  1997年   572篇
  1996年   356篇
  1995年   200篇
  1994年   189篇
  1993年   211篇
  1992年   31篇
  1991年   50篇
  1990年   52篇
  1989年   63篇
  1988年   61篇
  1987年   63篇
  1986年   56篇
  1985年   53篇
  1983年   10篇
  1982年   20篇
  1981年   24篇
  1980年   36篇
  1979年   3篇
  1978年   13篇
  1977年   105篇
  1976年   225篇
  1975年   11篇
  1955年   3篇
排序方式: 共有3459条查询结果,搜索用时 15 毫秒
11.
12.
This review comprises 36 patients who were treated for Asherman's syndrome from 1968 to 1974 at the Sloane Hospital for Women. Of the 18 patients who later conceived only 6 had uncomplicated term deliveries. Four had premature deliveries resulting in neonatal death. Three had placenta accreta and postpartum hemorrhage, necessitating a cesarean hysterectomy in 1. Two patients required cesarean section for complications due to the syndrome, 2 had spontaneous abortion, and 1 had a cervical pregnancy requiring total hysterectomy. Only 10 babies survived. The incidence and severity of complications in conceptions following treatment for Asherman's syndrome is high, and the obstetrician must be prepared to manage them.  相似文献   
13.
A small but significant number of tritiated thymidine labelled cells were found, by autoradiography, in the glomeruli of rats with Masugi nephritis or chronic serum sickness nephritis. There were no labelled glomerular cells in sections of untreated animals. The findings favour the contention that in proliferative glomerulonephritis, glomerular hypercellularity is due to infiltration of monocytic cells into the tufts where they divide.  相似文献   
14.
Solid dispersions of naltrexone in natural glycerides were used to form injectable implants which continuously release narcotic antagonists in vivo. The dispersions were formed and tested either as small cylindrical pellets, e.g. l x 3.0 mm in size, or as particles with diameters in size ranges between 125-250 mu, that are suspended in an aqueous methyl cellulose solution. Both types of implants delivered naltrexone to mice at rates that were effective in blocking the antiociceptive action of morphine for at least one month. The rate of naltrexone release was controlled by altering its concentration in the dispersion and by varying the glyceride composition. Degradation and absorption of the implants were found to depend on their composition, dimensions and location in the body. No appreciable tissue incompatibility was seen in mice, rats, rabbits, monkeys and swine, even when long-lasting preparations were removed a year after treatment.  相似文献   
15.
The body's equilibrium is possible thanks to the integration of skeletal structure, vertebrae, ligaments and muscles to form one functional unity. The forces which determine posture are composed of two complementary systems, the ligamentary and the muscular systems, which together determine a dynamic act of balance. The ligaments operate mainly against the visco-hydraulic pressure of the nucleus pulposus and bind the vertebral bodies together, whereas the muscles exhibit an antigravity function and support spinal stability. A mathematical model based on a mixed theory of directed and oriented curves is proposed. Through this model it is possible to develop an exact theory governing the deformation of the ligamentous spine. This theory should be universal in the sense that it can be used to supply the spine in any of its environments.  相似文献   
16.
Blood-engorged Culex tarsalis (4,209) collected during 1960 to 1965 in Kern County, California and previously shown to have fed on passeriform birds by the precipitin test were further tested by the more sensitive passive hemagglutination inhibition test (PHI). It was shown that these mosquitoes fed principally on House Finches and House Sparrows, the most common passeriform birds found in the collection areas. These data demonstrate the usefulness of the PHI test for the identification of arthropod blood meals from closely related species.  相似文献   
17.
Isotropic material can be made to exhibit piezoelectric effects by the application of a constant electric field. For insulators, the piezoelectric strain constant is proportional to the applied electric field and for semiconductors, an additional out-of-phase component of piezoelectricity is proportional to the electric current density in the sample. The two induced coefficients are proportional to the strain-dependent dielectric constant (depsilon/dS + epsilon) and resistivity (drho/dS - rho), respectively. The latter is more important at frequencies such that rhoepsilonomega less than 1, often the case in biopolymers. Signals from induced piezoelectricity in nature may be larger than those from true piezoelectricity.  相似文献   
18.
A case of acute pyelonephritis associated with venous encasement and amputation is described. Although venous encasement and amputation have been considered previously as specific signs of malignancy, it is now clear that these signs are non-specific, occurring also in inflammatory diseases of the kidney.  相似文献   
19.
Sudden infant death syndrome. A prospective study   总被引:1,自引:0,他引:1  
One hundred twenty-five sudden infant death syndrome (SIDS) victims followed up since birth from a large prospective study were compared with matched controls. Some of the future SIDS victims showed evidences of neonatal brain dysfunction including abnormalities in respiration, feeding, temperature regulation, and specific neurologic tests. These abnormalities could not be ralated to events in labor or delivery. A greater proportion of the future victims were mildly underweight for gestational age. The gestations that produced the SIDS victims were characterized by a greater frequency of mothers who smoked cigarettes and had anemia. The demographic profile of SIDS families proved to be indentical to the profile for families with excessive perinatal mortality. Many of the SIDS victims showed a retardation in postnatal growth prior to death.  相似文献   
20.
As part of a multifactorial computer-assisted study of patients with asthma, the relationship between air pollution, animal dander and asthma symptoms was evaluated. No association was found between four major air pollutants (carbon monoxide, ozone, nitrogen oxides and sulfur dioxide) and asthma symptoms. Patients who owned cats and dogs reported more severe asthma symptoms (p less than .01) than patients who did not own cats and dogs. The evaluations completed to date indicate that daily exposure to cats and dogs accounts for more of the asthma symptoms differences between patients than daily exposure to air pollutants.  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