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   387785篇
  免费   3578篇
  国内免费   774篇
电工技术   6596篇
综合类   332篇
化学工业   58221篇
金属工艺   22037篇
机械仪表   14520篇
建筑科学   7595篇
矿业工程   3940篇
能源动力   7487篇
轻工业   21395篇
水利工程   5810篇
石油天然气   13909篇
武器工业   31篇
无线电   37704篇
一般工业技术   87852篇
冶金工业   60489篇
原子能技术   11733篇
自动化技术   32486篇
  2021年   3173篇
  2019年   3095篇
  2018年   11724篇
  2017年   12105篇
  2016年   9915篇
  2015年   3836篇
  2014年   6016篇
  2013年   13779篇
  2012年   10763篇
  2011年   17290篇
  2010年   15061篇
  2009年   15035篇
  2008年   15316篇
  2007年   16664篇
  2006年   8901篇
  2005年   10386篇
  2004年   8966篇
  2003年   8655篇
  2002年   7617篇
  2001年   7263篇
  2000年   6979篇
  1999年   6829篇
  1998年   16202篇
  1997年   11574篇
  1996年   8734篇
  1995年   6618篇
  1994年   5826篇
  1993年   6094篇
  1992年   4756篇
  1991年   4716篇
  1990年   4662篇
  1989年   4539篇
  1988年   4556篇
  1987年   4095篇
  1986年   4191篇
  1985年   4491篇
  1984年   4276篇
  1983年   4090篇
  1982年   3724篇
  1981年   3896篇
  1980年   3813篇
  1979年   4007篇
  1978年   4114篇
  1977年   4268篇
  1976年   5248篇
  1975年   3769篇
  1974年   3722篇
  1973年   3820篇
  1972年   3468篇
  1971年   3126篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Business process redesign (BPR) has been widely touted as a means for leveraging the power of information technology to change business processes radically, resulting in substantial improvements in organizational effectiveness and efficiency. This study represents an early attempt at examining the strategic nature of the phenomenon. Because BPR is radical change and has the ability to alter both the competitive and operational nature of the corporation, it is critical that BPR be coordinated with corporate strategy. Through a survey of information system executives, the relationships between corporate competitive strategy and three types of BPR – intrafunctional, interfunctional and interorganizational – were examined. It was found that organizations following a cost strategy tended to do more BPR projects on interfunctional processes. Furthermore, the positive effect of a cost strategy on interfunctional BPR was found to be strengthened by the degree of integration of IS and business planning. It was also found that while interorganizational BPR was not related to a specific strategy, it was strongly related directly with IS–business planning integration.  相似文献   
992.
993.
Two more cases of late onset peripheral seronegative spondyloarthropathy (SpA) are reported. Like the patients reported by Dubost and Sauvezie, they had extensive pitting edema of the lower limbs, constitutional symptoms, elevated erythrocyte sedimentation rate and minimal involvement of the axial skeleton with marked signs of diffuse idiopathic skeletal hyperstosis.  相似文献   
994.
BACKGROUND: In several types of tumors, including hepatocellular carcinoma, prognosis could be correlated with DNA ploidy. Few studies have been performed on hepatoblastoma with contradictory results. METHODS: Twenty-nine cases of nonpretreated hepatoblastoma were studied with flow cytometry and image cytometry for DNA index and proliferation index using paraffin-embedded tissue. RESULTS: Twenty-three (79.9%) tumors were diploid, and 6 (20.7%) were aneuploid (hyperdiploid). Patients with diploid tumors were younger than those with aneuploid tumors. With regard to stage, diploid tumors were almost equally distributed among stages (tumor, lymph node metastases, distant metastases), whereas aneuploid tumors tended to occur in higher stages (tumor, lymph node metastases, distant metastases). Diploid tumors had clearly a better prognosis than aneuploid tumors, although the difference was not statistically significant (flow cytometry, P = 0.06; image cytometry, P = 0.16). A more favorable prognosis was also noted for hepatoblastomas with low-proliferation index (< or = 7%), but the difference from tumors with high-proliferation index (> 7%) again was not statistically significant (P = 0.16). CONCLUSIONS: Although no statistically significant differences in prognosis between hepatoblastomas with diploid and aneuploid DNA content, respectively, were found, there is a clear tendency that diploid hepatoblastomas behave more favorably. The same is true for hepatoblastomas with low-proliferation index.  相似文献   
995.
996.
997.
998.
We report 11 patients having revision of total hip arthroplasty using massive structural allografts for failure due to sepsis and associated bone loss. All patients had a two-stage reconstruction and the mean follow-up was 47.8 months (24 to 72). Positive cultures were obtained at the first stage in nine of the 11 patients, with Staphylococcus epidermidis being the most common organism. The other two patients had draining sinuses with negative cultures. There was no recurrence of infection in any patient. The mean increase in the modified Harris hip score was 45 and all the grafts appeared to have united to host bone. Two patients required additional procedures, but only one was related to the allograft. Complications included an incomplete sciatic nerve palsy and one case of graft resorption. Our results support the use of massive allografts in failed septic hip arthroplasty in which there is associated bone loss.  相似文献   
999.
1000.
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