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   249篇
  免费   2篇
  国内免费   1篇
化学工业   25篇
金属工艺   4篇
机械仪表   4篇
建筑科学   23篇
矿业工程   2篇
能源动力   2篇
轻工业   14篇
石油天然气   2篇
无线电   9篇
一般工业技术   29篇
冶金工业   96篇
原子能技术   1篇
自动化技术   41篇
  2023年   2篇
  2022年   4篇
  2021年   3篇
  2020年   2篇
  2019年   3篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2015年   3篇
  2014年   8篇
  2013年   8篇
  2012年   8篇
  2011年   8篇
  2010年   10篇
  2009年   9篇
  2008年   9篇
  2007年   12篇
  2006年   9篇
  2005年   9篇
  2004年   4篇
  2003年   6篇
  2002年   6篇
  2001年   7篇
  2000年   5篇
  1999年   6篇
  1998年   25篇
  1997年   9篇
  1996年   9篇
  1995年   6篇
  1994年   4篇
  1993年   9篇
  1992年   3篇
  1989年   3篇
  1988年   3篇
  1987年   3篇
  1985年   4篇
  1984年   5篇
  1981年   2篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1975年   4篇
  1974年   1篇
  1973年   1篇
  1968年   1篇
  1944年   1篇
  1932年   1篇
  1930年   1篇
  1927年   1篇
排序方式: 共有252条查询结果,搜索用时 15 毫秒
1.
We prepared polymers having a phospholipid polar group, poly [omega-methacryloyloxyalkyl phosphorylcholine (MAPC)-co-n-butyl methacrylate(BMA)], as new biomedical materials and evaluated their blood compatibility with attention to protein adsorption and platelet adhesion. The total amount of proteins adsorbed on the polymer surface from human plasma was determined, and the distribution of adsorbed proteins on the plasma-contacting surface was analyzed. The amount of proteins adsorbed on every poly (MAPC-co-BMA) was small compared with that observed on polymers without the phospholipid polar group. However, there was no significant difference in the amount of adsorbed proteins on the poly(MAPC-co-BMA) even when the methylene chain length between the phospholipid polar group and the backbone in the MAPC moiety was altered. Platelet adhesion on the polymer surface from a platelet suspension in a buffered solution was evaluated with and without plasma treatment on the surface. When a rabbit platelet suspension was brought into contact with the poly(BMA) surface after treatment with plasma, many platelets adhered and aggregated. However, a reduced amount of platelet adhered on the poly(BMA) was found in the case of direct contact with the platelet suspension. On the other hand, the poly(MAPC-co-BMA)s could inhibit platelet adhesion under both conditions. Based on these results, it can be concluded that the proteins adsorbed on the surface play an important role in determining the platelet adhesion and suppression of the protein adsorption on the surface, which is one of the most significant ways of inhibiting platelet adhesion.  相似文献   
2.
In this report, we demonstrate the utility of interleukin-2 (IL-2) stimulation of spleen cell cultures and bivariate flow cytometry in the analysis and purification of the C57BL/6J mouse Y Chromosome. We determined that the DNA content of the C57BL/6J Y Chromosome is approximately 94.7 Mb, making it similar in size to human Chromosome 16 and significantly larger than previous estimates. In addition, we describe the bulk isolation of mouse Y Chromosomes and demonstrate enrichment of the isolated material using a fluorescence in situ hybridization strategy. We detail the construction of two small insert Y Chromosome-specific libraries, ideal for sampling Y Chromosome sequences. From these libraries 1566 clones were analyzed. We provide a detailed characterization of 103 clones, generating nearly 50 kb of sequence. For 30 of these clones, we identify regions of homology to known Y chromosomal sequences, confirming the enrichment of the sorted DNA. From the remaining characterized clones, we describe the development of 15 male-specific PCR assays and 19 male-female PCR assays potentially originating from the pseudoautosomal region or other areas of X-Y or autosome-Y homology.  相似文献   
3.
In the course of their small angle x-ray scattering work, Winslow and Diamond also calculated the radius of gyration of the pores. Using its value for a paste, Diamond adopted two models for the average pore: a sphere and a cylinder of equal height and diameter. This model leads to absurd values for the surface area of the paste. Using a cylindrical model, and the radius of gyration plus the hydraulic radius, the present authors calculated for a similar paste the dimensions of the average pore and obtained the values: diameter = 47.2A?, length = 466A?. The number of pores per gram of paste was 2.26 × 1017. The paper also discusses the surface area of hardened paste, and points out the extremely important contributions of Winslow and Diamond to the subject.  相似文献   
4.
The mechanism(s) of insulin resistance in non-insulin-dependent diabetes mellitus remains ill defined. The current studies sought to determine whether non-insulin-dependent diabetes mellitus is associated with (a) a delay in the rate of onset of insulin action, (b) impaired hepatic and extrahepatic kinetic responses to insulin, and (c) an alteration in the contribution of gluconeogenesis to hepatic glucose release. To answer these questions, glucose disappearance, glucose release, and the rate of incorporation of 14CO2 into glucose were measured during 0.5 and 1.0 mU/kg-1 per min-1 insulin infusions while glucose was clamped at approximately 95 mg/dl in diabetic and nondiabetic subjects. The absolute rate of disappearance was lower (P < 0.05) and the rate of increase slower (P < 0.05) in diabetic than nondiabetic subjects during both insulin infusions. In contrast, the rate of suppression of glucose release in response to a change in insulin did not differ in the diabetic and nondiabetic subjects during either the low (slope 30-240 min:0.02 +/- 0.01 vs 0.02 +/- 0.01) or high (0.02 +/- 0.00 vs 0.02 +/- 0.00) insulin infusions. However, the hepatic response to insulin was not entirely normal in the diabetic subjects. Both glucose release and the proportion of systemic glucose being derived from 14CO2 (an index of gluconeogenesis) was inappropriately high for the prevailing insulin concentration in the diabetic subjects. Thus non-insulin-dependent diabetes mellitus slows the rate-limiting step in insulin action in muscle but not liver and alters the relative contribution of gluconeogenesis and glycogenolysis to hepatic glucose release.  相似文献   
5.
We introduce a new family of fungal protease inhibitors with β-trefoil fold from the mushroom Coprinopsis cinerea, named cocaprins, which inhibit both cysteine and aspartic proteases. Two cocaprin-encoding genes are differentially expressed in fungal tissues. One is highly transcribed in vegetative mycelium and the other in the stipes of mature fruiting bodies. Cocaprins are small proteins (15 kDa) with acidic isoelectric points that form dimers. The three-dimensional structure of cocaprin 1 showed similarity to fungal β-trefoil lectins. Cocaprins inhibit plant C1 family cysteine proteases with Ki in the micromolar range, but do not inhibit the C13 family protease legumain, which distinguishes them from mycocypins. Cocaprins also inhibit the aspartic protease pepsin with Ki in the low micromolar range. Mutagenesis revealed that the β2-β3 loop is involved in the inhibition of cysteine proteases and that the inhibitory reactive sites for aspartic and cysteine proteases are located at different positions on the protein. Their biological function is thought to be the regulation of endogenous proteolytic activities or in defense against fungal antagonists. Cocaprins are the first characterized aspartic protease inhibitors with β-trefoil fold from fungi, and demonstrate the incredible plasticity of loop functionalization in fungal proteins with β-trefoil fold.  相似文献   
6.
A method for capturing geometric features of real-world scenes relies on a simple capture setup modification. The system might conceivably be packaged into a portable self-contained device. The multiflash imaging method bypasses 3D geometry acquisition and directly acquires depth edges from images. In the place of expensive, elaborate equipment for geometry acquisition, we use a camera with multiple strategically positioned flashes. Instead of having to estimate the full 3D coordinates of points in the scene (using, for example, 3D cameras) and then look for depth discontinuities, our technique reduces the general 3D problem of depth edge recovery to one of 2D intensity edge detection. Our method could, in fact, help improve current 3D cameras, which tend to produce incorrect results near depth discontinuities. Exploiting the imaging geometry for rendering provides a simple and inexpensive solution for creating stylized images from real scenes. We believe that our camera will be a useful tool for professional artists and photographers, and we expect that it will also let the average user easily create stylized imagery. This article is available with a short video documentary on CD-ROM.  相似文献   
7.
Observations of tropical cyclone structure from WindSat   总被引:1,自引:0,他引:1  
Passive microwave (PMW) radiometric observations of clouds from multichannel imaging sensors onboard low Earth-orbiting environmental satellites are now a vital operational dataset. The first operational passive microwave sensor was the Special Sensor Microwave/Imager onboard the Defense Meteorological Satellite Program satellites, which has been gathering hydrological data records since 1987, and continued with the Tropical Rainfall Measuring Mission (TRMM) and the Advanced Microwave Scanning Radiometer onboard Aqua. These sensors view the underlying scene with an Earth incidence angle near 53/spl deg/ and with a variable azimuthal angle, depending upon the orbit direction and scan position. The WindSat sensor onboard the Coriolis satellite, launched in January 2003, is a five-channel polarimetric PMW radiometer designed to optimize ocean surface wind vector retrievals. While it does not have 85-GHz channels, an added feature is its unique fore-aft viewing capability across a portion of its fore scan swath. This provides a view of the underlying scene from two separate azimuthal directions, which provides added information on the three-dimensional (3-D) structure of clouds and their evolution. In this paper, we compare WindSat and TRMM Precipiation Radar observations of tropical cyclones (TCs) with Monte Carlo radiative transfer simulations performed on idealized 3-D convective cloud structures. The TC 3-D structure and possible tilt in the convective cloud structure are inferred from the difference between the 37-GHz equivalent blackbody brightness temperatures (T/sub B/) from the corresponding fore and aft view observations. The information gained from this analysis is important since asymmetries in the cloud vertical and horizontal structure may be an indication of upper level wind shear, which plays a major role in influencing changes of the TC intensity.  相似文献   
8.
This report evidences that the single polypeptide chain of cathepsin D undergoes in vitro autolysis resulting in heavy (Mr about 30000) and light (Mr about 15000) polypeptide chains. These two chains are held together through non-covalent interaction, thus constituting a stable active conformation. Fluorescence and circular dichroism measurements demonstrate the irreversible denaturation of cathepsin D. The existence of cathepsin D precursor, cathepsinogen D, of about 50000 molecular weight was proved. Cathepsinogen D is converted to the active enzyme by intramolecular activation, releasing activation-inhibitory peptide(s).  相似文献   
9.
A comprehensive review of the existing theories of microcontinuum fluid mechanics has been presented by the authors in a previous paper. In this paper the published applications of these microfluid theories to real and ideal flow problems have been reviewed briefly and these short reviews are presented in tabular form for easy reference.  相似文献   
10.
To study the influence of tetanus antitoxins on the outcome of human tatanus, we analyzed data on 545 cases reported to the Center for Disease Control from 1965 through 1971. Patients treated with antitoxin had a significantly lower case-fatality ratio than untreated patients, and the effect of serotherapy was not modified significantly by the age or race of the subjects. Antitoxin of equine origin and human tetanus immune globulin (TIG) were equally effective. The data on the effect of different doses of TIG suggest that 500 units may be as effective as the currently recommended therapeutic dose of 3,000 to 10,000 units. The importance of possible bias introduced by unmeasured factors such as quality of supportive therapy could not be determined, but confounding by 11 recorded potentially confounding factors was minimal.  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