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   3558篇
  免费   24篇
  国内免费   13篇
电工技术   24篇
综合类   12篇
化学工业   109篇
金属工艺   30篇
机械仪表   17篇
建筑科学   21篇
矿业工程   1篇
能源动力   40篇
轻工业   118篇
水利工程   4篇
石油天然气   10篇
无线电   30篇
一般工业技术   82篇
冶金工业   3033篇
原子能技术   5篇
自动化技术   59篇
  2023年   3篇
  2022年   14篇
  2021年   16篇
  2020年   8篇
  2019年   8篇
  2018年   8篇
  2017年   9篇
  2016年   10篇
  2015年   16篇
  2014年   20篇
  2013年   64篇
  2012年   54篇
  2011年   35篇
  2010年   43篇
  2009年   39篇
  2008年   24篇
  2007年   26篇
  2006年   11篇
  2005年   15篇
  2004年   8篇
  2003年   20篇
  2002年   7篇
  2001年   7篇
  2000年   15篇
  1999年   104篇
  1998年   946篇
  1997年   584篇
  1996年   359篇
  1995年   176篇
  1994年   147篇
  1993年   213篇
  1992年   27篇
  1991年   15篇
  1990年   27篇
  1989年   19篇
  1988年   23篇
  1987年   20篇
  1986年   19篇
  1985年   20篇
  1983年   11篇
  1982年   15篇
  1981年   22篇
  1980年   27篇
  1979年   2篇
  1978年   11篇
  1977年   96篇
  1976年   212篇
  1975年   7篇
  1973年   2篇
  1955年   4篇
排序方式: 共有3595条查询结果,搜索用时 15 毫秒
61.
Multimedia analysis and reuse of raw un-edited audio visual content known as rushes is gaining acceptance by a large number of research labs and companies. A set of research projects are considering multimedia indexing, annotation, search and retrieval in the context of European funded research, but only the FP6 project RUSHES is focusing on automatic semantic annotation, indexing and retrieval of raw and un-edited audio-visual content. Even professional content creators and providers as well as home-users are dealing with this type of content and therefore novel technologies for semantic search and retrieval are required. In this paper, we present a summary of the most relevant achievements of the RUSHES project, focusing on specific approaches for automatic annotation as well as the main features of the final RUSHES search engine.  相似文献   
62.
The influence of the quality of care that patients receive during the course of their illness has been the subject of special scrutiny in the area of mental health. The concept of "expressed emotion" (EE) evolved in an effort to understand the impact of family and social environment on the vulnerability to relapse of schizophrenic patients. A semistructured interview, the Camberwell Family Interview, was developed to assess expressed emotion. This article examines the historical context, generalizability, methodological strengths and limitations of the construct of EE and the Camberwell Family Interview, as well as the nature and effects of treatment intervention programs designed to neutralize adverse effects of patient caretaker attitudes.  相似文献   
63.
64.
Motivated by the finding that the amino acid sequence of the Bence Jones protein BJP-DIA was identical to that of the main protein component of the amyloid fibrils obtained from the same patient with AL-amyloidosis, (Klafki, H.-W., Kratzin, H.-D., Pick, A.-I., Eckart, K., Karas, M. & Hilschmann, N. (1992) Biochemistry 31, 3265-3272.), we attempted to create "amyloid-like" fibrils from the Bence Jones protein in vitro, without addition of proteolytic enzymes. Reduction of BJP-DIA, solubilized in PBS, pH 7.4, overnight at 37 degrees C resulted in the formation of a precipitate which had affinity for the dye Congo red. Electron microscopy of negatively stained samples of the reduced protein revealed aggregates of linear unbranched fibrils. SDS-polyacrylamide gel electrophoresis demonstrated that the precipitate consisted almost exclusively of intact light chain molecules. This result makes it possible to deduce a molecular model of these amyloid fibrils generated in vitro.  相似文献   
65.
Translation of HeLa cell RNA containing poly(A) in a wheat germ cell-free system is markedly but incompletely inhibited by 7-methylguanosine 5'-monophosphate (m7G5'p). We have analyzed the translation products synthesized in the presence of different concentrations of m7G5'p and find that translation of all mRNAs is equally inhibited. To demonstrate the specificity of the inhibitor for RNAs with 5'-terminal m7G5' ppp... we show that specific translation products of satellite tobacco necrosis virus RNA, which does not have this 5' terminus, are synthesized in the presence of m7G5' p. Protein synthesis programmed by endogenous mRNA in a HeLa cell-free system is inhibited after a 10-min lag by m7G5' p. Other guanosine nucleotides without the 7-methyl group or with the phosphate in a different position are not inhibitor. We show that translation of all mRNAs is inhibited to a similar extent by m7G5'p in the HeLa cell-free system, by synthesizing 35S-labeled proteins in the presence of different inhibitory concentrations of this nucleotide and analyzing the translation products by electrophoresis and autoradiography. Translation of encephalomyocarditis virus RNA added to the HeLa cell-free system is not inhibited by m7"g5p; this viral RNA does not have this nucleotide at the 5' terminus. This indicates that m7G5'p specifically inhibits translation of mRNAs with the 5' terminus m7G5'ppp... and suggests that initiation of translation of picornavirus RNA may proceed via a mechanism different from that of cellular mRNAs.  相似文献   
66.
Relationship of passive cigarette-smoking to sudden infant death syndrome   总被引:1,自引:0,他引:1  
The smoking habits of 56 families who lost babies to the sudden infant death syndrome (SIDS) were compared to those of 86 control families. A higher proportion of SIDS mothers smoked both during pregnancy (61% vs. 42%) and after their babies were born (59% vs. 37%). SIDS mother also smoked a significantly greater number of cigarettes than controls. Exposure to cigarette smoke ("passive smoking") appears to enhance the risk of SIDS for reasons not known.  相似文献   
67.
Because of the unresolved controversy regarding the effect of epidural anesthesia upon uterine contractility, it was decided to study its effect on a small number of patients. Intrauterine and intra-arterial continuous pressure, continuous fetal heart rate, and maternal heart rate recordings were obtained from at least 20 minutes before administration of the epidural anesthic until complete dilatation in these patients. Nineteen patients were in spontaneous labor, and 18 had labor stimulated with oxytocin. Plain lidocaine, 1 or 1.5%, was used in 12 patients (30 observations), and lidocaine with epinephrine, 1:200,000 was used in 26 patients (51 observations). Uterine contractions were calculated in Montevideo units for 60 minutes following the epidural anesthetic. The changes, if any, were compared in both groups. There was a significant decrease in uterine activity when epinephrine was added to the anesthetic solution, mainly a lessening of intensity. There were comparable decreases in systolic/diastolic blood pressure in both groups and compensatory tachycardia. In one case, severe hypertension was observed following administration of lidocaine epinephrine. It was concluded that the addition of epinephrine to the anesthetic solution predictably produces diminution of uterine activity, and it does not give "cardiovascular support" to the laboring patient.  相似文献   
68.
A new diagnostic method to determine fibrinogen and fibrin splitting products is based on the fact that high-molecular fragments acting as specific inhibitors of fibrin self-assembly compose these products. Fibrinogen and fibrin splitting products are detected and determined quantitatively by prolongation of coagulation time in the test with the standard monomeric fibrin. The number of units of anticoagulating activity in the studied urine are the results of the determinations. Sensitivity of the method if necessary may be increased by adding of a certain amount of the fibrinogen and fibrin splitting products to the test that makes a favourable background for the action of the products. The method is rather sensitive, reliable and simple. It may be used in ordinary clinical laboratories. The method proved to be quite satisfactory when testing renal diseases at the clinic. It is of great significance for early detection of the transplanted kidney rejection. The new method is compared with the known immunological method which consist in determination of the inhibitory effect of the fibrinogen and fibrin splitting products on agglutination of erythrocytes of specific antibodies; the erythrocytes being subjected to "tanning" and "loading" with fibrinogen. A satisfactory correlation is found between the results of two methods.  相似文献   
69.
Efficient and accurate image based camera registration   总被引:2,自引:0,他引:2  
A technique for efficient and accurate camera registration based on stereo image analysis is presented. Initially, few correspondences are estimated with high accuracy using a probabilistic relaxation technique. Accuracy is achieved by considering the continuous approximations of selected image areas using second order polynomials and a relaxation rule defined according to the likelihood that estimates obey stereoscopic constraints. The extrinsic camera parameters are then obtained using a novel efficient and robust approach derived from the classic eight point algorithm. Efficiency is achieved by solving a parametric linear optimization problem rather than a nonlinear one as more conventional methods attempt to do. Robustness is obtained by applying two novel strategies: normalization of the initial data via a simple but efficient diagonal scaling approach, and regularization of the underlying linear parametric optimization problem using meaningful constraints. The performance of the presented methods is assessed in several computer experiments using natural video data.  相似文献   
70.
Rat adrenal cortex contains a protein(s) that binds pregnenolone with high affinity. This binding, demonstrated by gel filtration and by a dextran-coated charcoal method, was associated with the cytosol and with fractions solubilized by sonication from the mitochondria and microsomes. The binding of pregnenolone was saturable and was inhibited by mercurials and proteolytic enzymes. Pregnenolone-binding was not influenced by the presence of progesterone, deoxycorticosterone, corticosterone or aldosterone, but was inhibited by steroids with a 3beta-hydroxy-5-ene structure similar to pregnenolone, and by hydroxymethylene steroid and cyanoketone. We suggest that this protein is involved in the intracellular transport and retention of pregnenolone within adrenal cortical cells.  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