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   6752篇
  免费   8篇
电工技术   4篇
化学工业   54篇
金属工艺   5篇
机械仪表   5篇
建筑科学   6篇
矿业工程   1篇
能源动力   11篇
轻工业   84篇
水利工程   3篇
石油天然气   1篇
无线电   14篇
一般工业技术   23篇
冶金工业   6532篇
自动化技术   17篇
  2023年   2篇
  2021年   4篇
  2019年   2篇
  2018年   3篇
  2017年   2篇
  2016年   2篇
  2015年   4篇
  2014年   5篇
  2013年   7篇
  2012年   6篇
  2011年   9篇
  2010年   8篇
  2009年   12篇
  2008年   12篇
  2007年   6篇
  2006年   13篇
  2005年   10篇
  2004年   9篇
  2003年   17篇
  2002年   13篇
  2001年   5篇
  2000年   10篇
  1999年   163篇
  1998年   1936篇
  1997年   1148篇
  1996年   766篇
  1995年   391篇
  1994年   352篇
  1993年   394篇
  1992年   52篇
  1991年   107篇
  1990年   110篇
  1989年   95篇
  1988年   104篇
  1987年   89篇
  1986年   77篇
  1985年   61篇
  1983年   12篇
  1982年   35篇
  1981年   48篇
  1980年   59篇
  1979年   3篇
  1978年   27篇
  1977年   185篇
  1976年   357篇
  1975年   11篇
  1973年   2篇
  1971年   3篇
  1955年   4篇
  1954年   3篇
排序方式: 共有6760条查询结果,搜索用时 11 毫秒
31.
Budd Chiari syndrome (liver vein thrombosis) may be a diagnostic and therapeutic problem. On the basis of four different cases we review the major diagnostic and therapeutic principles involved. Imaging techniques are necessary in order to establish the diagnosis. Ultrasound examination with Duplex doppler is usually sufficient, but MR angiography is also useful. Treatment options are thrombolysis, surgery or liver transplantation. What treatment is selected will depend on the clinical situation and the prognosis.  相似文献   
32.
33.
BU Sevin  JP Perras 《Canadian Metallurgical Quarterly》1997,176(4):759-66; discussion 766-8
OBJECTIVE: Our purpose was to study the heterogeneity of drug response in fresh human ovarian tumors to chemotherapeutic agents in an in vitro chemosensitivity assay. STUDY DESIGN: This assay evaluates total tumor cell kill by measuring the intracellular adenosine triphosphate levels of untreated controls and drug-exposed cells at various doses after culture for 6 days. The surviving fraction is calculated by dividing the treated values with the control values. One hundred tumors were tested against four single drugs (cisplatin, the active metabolite of cytoxan, 4-hydroxyperoxy-cyclophosphamide, Taxol, and carboplatin) and two drug combinations (cisplatin plus 4-hydroxyperoxy-cyclophosphamide; cisplatin plus Taxol). RESULTS: There is great variation in the degree of cell death for single drugs and drug combinations among the 100 tumors tested. CONCLUSION: More effective clinical response to chemotherapy may be achieved in patients with ovarian cancer by selecting the most active drugs for chemotherapy, on the basis of in vitro chemosensitivity test results for individual patients.  相似文献   
34.
35.
36.
37.
OBJECTIVE: To evaluate the diagnostic accuracy and clinical usefulness of high-resolution transvaginal duplex Doppler ultrasound in postpartum and post-abortion patients with excessive hemorrhage who are suspected of having residual trophoblast. METHODS: Forty-eight women with excessive hemorrhage referred for possible residual trophoblastic tissue were evaluated by transvaginal duplex Doppler ultrasonography. Based on two-dimensional imaging, the patients were divided prospectively into groups: women who had an empty uterus with a normal uterine cavity, those with a pure endometrial fluid collection and no echogenic foci, those who had a mixed endometrial fluid collection with foci of echogenicity, and those with intracavitary heterogeneous material with mixed echo patterns of fluid and solid components. In each group, Doppler studies were performed and the resistance index (RI) was calculated. The two-dimensional patterns and Doppler results were correlated with clinical and pathologic follow-up. RESULTS: Twenty-eight subjects had a normal uterine cavity and seven had a pure endometrial fluid collection; all were treated conservatively and none showed later clinical evidence of residual trophoblastic tissue. In 13 women, residual trophoblast was strongly suggested from the images of two-dimensional ultrasonography: Five showed an endometrial fluid collection with some echogenic foci, and eight exhibited intracavitary mixed echogenic material. All underwent curettage, and residual trophoblastic tissue was found in ten of the 13. The mean (+/- standard deviation) RI to flow in the myometrial arteries was 0.54 +/- 0.15 in women without residual trophoblast and 0.35 +/- 0.1 in those with residual trophoblastic tissue (P < .01). CONCLUSION: Our experience suggests that transvaginal duplex Doppler ultrasonography is an effective noninvasive method for evaluating patients with excessive postpartum and post-abortion hemorrhage who are suspected of having residual trophoblastic tissue. Its use enhances the positive preoperative diagnosis of residual trophoblastic tissue and may reduce unnecessary curettage procedures.  相似文献   
38.
The senior authors' initial experience with primary hybrid hip replacement in patients with osteoarthritis was studied to evaluate the efficacy of the procedure. Hybrid total hip arthroplasty (uncemented Harris-Galante acetabular component and cemented Iowa precoated femoral component) was performed in 131 consecutive, nonselected hips in 118 patients with the diagnosis of primary osteoarthritis. Followup was performed at 8 to 9 years after the procedure. The average age at the time of the procedure was 68 years (range, 45-87 years). There were 50 men (55 hips) and 68 women (76 hips). At final followup 19 patients (22 hips) had died. The femoral component had been revised for aseptic loosening in 8 hips (6.1%). One additional hip showed definite radiographic loosening. Hence, the prevalence of radiographic femoral failure was 6.9% (9 hips). No acetabular component had been revised for aseptic loosening and no acetabular component had migrated. The senior author continues to perform hybrid total hip arthroplasty in all patients with primary osteoarthritis. However, design modifications have been made in the femoral component that is used.  相似文献   
39.
40.
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