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   3854篇
  免费   0篇
化学工业   12篇
轻工业   9篇
水利工程   1篇
石油天然气   2篇
无线电   3篇
一般工业技术   1篇
冶金工业   3824篇
自动化技术   2篇
  2024年   1篇
  2023年   2篇
  2018年   1篇
  2016年   1篇
  2014年   1篇
  2013年   1篇
  2010年   1篇
  2007年   1篇
  2006年   2篇
  2005年   3篇
  2004年   4篇
  2003年   8篇
  2000年   1篇
  1999年   117篇
  1998年   1255篇
  1997年   729篇
  1996年   474篇
  1995年   241篇
  1994年   168篇
  1993年   220篇
  1992年   19篇
  1991年   45篇
  1990年   42篇
  1989年   41篇
  1988年   47篇
  1987年   31篇
  1986年   35篇
  1985年   31篇
  1983年   6篇
  1982年   11篇
  1981年   13篇
  1980年   29篇
  1979年   3篇
  1978年   6篇
  1977年   76篇
  1976年   179篇
  1975年   3篇
  1966年   1篇
  1964年   1篇
  1955年   4篇
排序方式: 共有3854条查询结果,搜索用时 0 毫秒
991.
A prospective study was designed to determine the impact of surgical timing on postoperative motion and stability following anterior cruciate ligament (ACL) reconstructive surgery. The study population was limited to acute ACL ruptures from downhill skiing undergoing arthroscopic ACL surgery without arthrotomy or surgical intervention for other ligamentous structures; 185 patients were entered into four separate groups based on the time interval from injury to surgery. Motion and stability were tested at multiple time points from the index surgery and adverse events were recorded. We found no statistical difference in restoration of extension or flexion in any group at any time point. KT-1000 data at 12 months showed a side-to-side difference of < or = 3 mm in 94%, with 6% showing a side-to-side difference of > 3 and < or = 5 mm. We conclude that, in this population, by using modern arthroscopic surgical techniques and an aggressive postoperative physical therapy protocol, motion and stability can be restored in a high percentage of patients and that surgical success is independent of the timing of surgery.  相似文献   
992.
993.
Experimental conditions (pH 6.5, 24 h reaction, peptide:biotin ratio 1:5) were defined for preferential incorporation of the biotin molecule in the N-terminal alpha-amino group of peptides. This strategy could be helpful in numerous applications when an entire peptide chain must remain accessible for antibody or receptor binding. We illustrate this advantage in a solid-phase enzyme immunoassay designed to detect antibodies specific for bovine beta-lactoglobulin present in rabbit or human sera. This test involves synthetic peptides biotinylated in different positions and immobilized on a solid phase. The use of biotin/streptavidin interactions permitted more efficient detection of specific anti-peptide antibodies than solid phases prepared using conventional passive-adsorption techniques. The highest levels of antibody binding were measured when biotinylation occurred at the N-terminal extremity of immobilized peptides.  相似文献   
994.
995.
Dermoid cysts of the ovary with malignant transformation: MR appearance   总被引:1,自引:0,他引:1  
OBJECTIVE: This study presents the MR appearances of five women with a total of six proven dermoid cysts of the ovary with malignant transformation. To our knowledge, the MR findings of this entity have not been reported. CONCLUSION: The lesions appeared to be fat-containing tumors with a solid component (4/6) that extended transmurally (4/6) and extensively invaded neighboring pelvic organs (3/6). The supervening malignancy was squamous cell carcinoma in four tumors, melanoma in one, and transitional cell carcinoma in one. The mode of spread differed from that of common ovarian tumors in that it included transmural extension and local invasion, reflecting squamous cell carcinoma.  相似文献   
996.
As the incidence of melanoma skin cancer continues to increase in this country, so does the need for early detection and treatment of these tumors. This article discusses a military skin cancer screening clinic that encourages patient participation and the criteria and statistics regarding the different treatment modalities we employ to treat these skin cancers.  相似文献   
997.
DoxA is a cytochrome P-450 monooxygenase involved in the late stages of daunorubicin and doxorubicin biosynthesis that has a broad substrate specificity for anthracycline glycone substrates. Recombinant DoxA was purified to homogeneity from Streptomyces lividans transformed with a plasmid containing the Streptomyces sp. strain C5 doxA gene under the control of the strong SnpR-activated snpA promoter. The purified enzyme was a monomeric, soluble protein with an apparent Mr of 47,000. Purified DoxA catalyzed the 13-hydroxylation of 13-deoxydaunorubicin, the 13-oxidation of 13-dihydrocarminomycin and 13-dihydrodaunorubicin, and the 14-hydroxylation of daunorubicin. The pH optimum for heme activation was pH 7.5, and the temperature optimum was 30 degreesC. The kcat/Km values for the oxidation of anthracycline substrates by purified DoxA, incubated with appropriate electron-donating components, were as follows: for 13-deoxydaunorubicin, 22,000 M-1 x s-1; for 13-dihydrodaunorubicin, 14,000 M-1 x s-1; for 13-dihydrocarminomycin, 280 M-1 x s-1; and for daunorubicin, 130 M-1 x s-1. Our results indicate that the conversion of daunorubicin to doxorubicin by this enzyme is not a favored reaction and that the main anthracycline flux through the late steps of the daunorubicin biosynthetic pathway catalyzed by DoxA is likely directed through the 4-O-methyl series of anthracyclines.  相似文献   
998.
Eighteen common serotypes representative of group E(1), E(2), E(3), and E(4)Salmonella were characterized using a single set of phages.  相似文献   
999.
1000.
X-linked non-specific mental retardation (MRX) is a heterogeneous condition in which mental retardation (MR) appears to be the only consistent manifestation. The genetic and phenotypic heterogeneity exclude any possibility of pooling families and, therefore, of fine-mapping the related disease genes. In order to identify genomic critical regions involved in the MRX condition assigned to Xp21.3-22.1 region, we have implemented the PCR screening of non fragile X MR patients for the presence of deletions in this region. The amplification by PCR of 12 markers located between POLA and DXS704 using genomic DNA from 192 MR males led to the identification, in a 9 year old mentally retarded boy, of a microdeletion which extends from DXS1202 to DXS1065. None of the known genes, POLA, MAGE genes cluster, DAX1, GK and DMD, that map in the Xp21.3-22.1 region is affected by this deletion. This approach, which could easily be applied to several other MRX loci, allowed not only a confirmation of the presence of a potential locus in Xp21.3-22.1 involved in non-specific mental retardation, but also a better definition of the genomic critical region corresponding to this locus.  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