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   93127篇
  免费   10410篇
  国内免费   6520篇
电工技术   8046篇
综合类   9424篇
化学工业   10770篇
金属工艺   5956篇
机械仪表   5800篇
建筑科学   6042篇
矿业工程   3852篇
能源动力   2491篇
轻工业   10756篇
水利工程   3024篇
石油天然气   3053篇
武器工业   1568篇
无线电   8043篇
一般工业技术   6915篇
冶金工业   11095篇
原子能技术   1448篇
自动化技术   11774篇
  2024年   627篇
  2023年   1578篇
  2022年   3628篇
  2021年   4589篇
  2020年   3298篇
  2019年   2238篇
  2018年   2426篇
  2017年   2758篇
  2016年   2520篇
  2015年   4007篇
  2014年   4901篇
  2013年   5812篇
  2012年   7292篇
  2011年   7545篇
  2010年   7220篇
  2009年   6586篇
  2008年   6706篇
  2007年   6531篇
  2006年   5588篇
  2005年   4337篇
  2004年   3220篇
  2003年   2202篇
  2002年   1944篇
  2001年   1798篇
  2000年   1453篇
  1999年   771篇
  1998年   2737篇
  1997年   1566篇
  1996年   1019篇
  1995年   590篇
  1994年   505篇
  1993年   547篇
  1992年   124篇
  1991年   122篇
  1990年   124篇
  1989年   118篇
  1988年   94篇
  1987年   84篇
  1986年   78篇
  1985年   54篇
  1983年   17篇
  1982年   39篇
  1981年   41篇
  1980年   72篇
  1979年   17篇
  1977年   158篇
  1976年   283篇
  1975年   13篇
  1959年   36篇
  1951年   15篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
61.
马品仲 《半导体光电》1995,16(3):252-255
简述了人造参考星系统,并用该系统作为大型望远镜主动光学和自适应光学的Shack-Hartman波面探测系统的光源。  相似文献   
62.
The discovery of an organic component in kidney stones dates back to 1684. More than 150 years elapsed before the incrustation of this organic component, which is now called the matrix, was proposed as the mechanism of stone formation. The composition of the matrix remained largely unknown until the development of electron microscopy and the advances in biochemistry combined in the 1950's to usher in the modern era of renal stone matrix investigation. Composed mainly of selectively incorporated proteins generally characterized by high glutamic and aspartic acid content and the frequent occurrence of gamma-carboxyglutamic acid, the matrix displays a variable and complex composition and shares a few proteins in many stones. The embryonic stone may first appear in the renal tubules where it can acquire the blood and cell membrane proteins recently found by analysis of stone protein extracts. The combination of supersaturation, an appropriate environment, the availability of calcium binding proteins which may be abnormal, and the incorporation of proteins extracted from leukocytes and cell wall membranes may induce stone formation.  相似文献   
63.
64.
65.
This study defines the current modes of treatment of patients with uterine fibromas with a review of the literature. Progesterone treatments appear to be principally used in cases of minor functional symptomatology and we discuss recent studies of mifepristone. GnRH agonists are particularly effective in preoperative treatment for conservative surgery. The indications and results of hysteroscopic resection and laparoscopic myomectomy are compared to those of classic myomectomy and hysterectomy. The indications for myolysis are discussed.  相似文献   
66.
67.
68.
The measurement of bone mineral density (BMD) using dual energy X-ray absorptiometry (DXA) provides an indicator of subsequent risk of hip fracture, but because of the significant overlap of measurements obtained from osteoporotic and control groups its predictive power is limited. The radiographic technique of Singh grading for the assessment of femoral osteoporosis utilizes information about the distribution of trabecular bundles, but the morphological information available in the DXA image has not previously been analysed. In this study of DXA images from 64 individuals (32 controls and 32 classified as osteoporotic) a subjective grading technique analogous to Singh grading is proposed, and quantitative measurements are made of image features corresponding to two of the categories. Discrimination was assessed using receiver operating characteristic (ROC) curves: the best discrimination was by spinal BMD (Az = 0.85 +/- 0.05) a performance equalled by one of the new parameters; the subjective grading method (Az = 0.79 +/- 0.07) performed as well as measurements of BMD in the femur. These results suggest that although the alternative measures do not improve on the discrimination possible using spinal BMD, morphological information from the hip itself may in the future have a place in the assessment of bone quality.  相似文献   
69.
OBJECTIVE: To analyze the levels of free carnitine and carnitine esters in the muscles of patients with inflammatory myopathies. METHODS: Six men and 7 women with inflammatory myopathy and 25 age-matched healthy controls were studied. Free carnitine and carnitine esters in muscle homogenates were measured by a radiochemical procedure. Muscle histochemical staining and measurement of respiratory chain enzyme activity were also performed. RESULTS: Eleven patients had muscle carnitine insufficiency. Five of them had subsarcolemmal oxidative accumulations, 5 had lipid droplets, and 4 had defects of the respiratory chain enzyme complexes. CONCLUSION: Abnormal distribution of muscle carnitine is present in patients with inflammatory myopathies and could impair muscle function. Coexistent mitochondrial dysfunction may contribute to carnitine insufficiency.  相似文献   
70.
The autoantigen in adjuvant arthritis in Lewis rats is still unknown despite the knowledge that the 65 kDa mycobacterial heat-shock protein (hsp) is involved in the disease process. T cells and antibodies obtained from rats with adjuvant arthritis respond to chondrocyte membrane antigen(s). In Western blots a 65 kDa chondrocyte membrane protein (CH65) is stained by sera from arthritic rats. In addition, spleen cells from rats with adjuvant arthritis proliferate in vitro to chondrocyte membranes and CH65 as antigens. Furthermore, pretreatment of rats with CH65 or mycobacterial hsp65 but not human hsp60, induces a significant retardation of the onset of adjuvant arthritis in Lewis rats. The data suggest that CH65 is a potential autoantigen involved in the pathogenesis of adjuvant arthritis in Lewis rats.  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