全文获取类型
收费全文 | 2219篇 |
免费 | 16篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 2236篇 |
出版年
2023年 | 8篇 |
2021年 | 10篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2016年 | 8篇 |
2014年 | 22篇 |
2013年 | 52篇 |
2012年 | 38篇 |
2011年 | 46篇 |
2010年 | 40篇 |
2009年 | 37篇 |
2008年 | 37篇 |
2007年 | 32篇 |
2006年 | 36篇 |
2005年 | 32篇 |
2004年 | 45篇 |
2003年 | 37篇 |
2002年 | 32篇 |
2001年 | 21篇 |
2000年 | 22篇 |
1999年 | 64篇 |
1998年 | 396篇 |
1997年 | 253篇 |
1996年 | 152篇 |
1995年 | 82篇 |
1994年 | 93篇 |
1993年 | 83篇 |
1992年 | 26篇 |
1991年 | 40篇 |
1990年 | 34篇 |
1989年 | 40篇 |
1988年 | 36篇 |
1987年 | 35篇 |
1986年 | 38篇 |
1985年 | 36篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 25篇 |
1976年 | 38篇 |
1975年 | 8篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1972年 | 9篇 |
1971年 | 7篇 |
1970年 | 7篇 |
1966年 | 8篇 |
排序方式: 共有2236条查询结果,搜索用时 31 毫秒
31.
M. Reischmann R. Merz L. Schultz L. E. Weiss 《e & i Elektrotechnik und Informationstechnik》2002,119(7-8):248-252
In the course of the research described in this paper a prototype assembly system for the automated fabrication of customized, biodegradable bone implants for tissue engineering applications has been developed. This work is part of a collaborative effort between the Handling Laboratory (hLab) of Fachhochschule Vorarlberg and the Bone Tissue Engineering Center (BETC) of Carnegie Mellon University. Bone implants are built up using thin layers of highly porous, biodegradable polymer scaffold materials. These layers can be seeded with cells prior to assembly. The main focus of this work is robotic handling of the prefabricated polymer layers. Additional components that are addressed include the cutting of contoured polymer layers from sheetstock and the assembly of the 21/2 dimensional layers to form 3D bone implants. Cutting tests have been performed to assess different cutting technologies. Assembly tests with mechanical connectors and fibrin adhesive have also been conducted. These components are integrated within a robot cell to demonstrate overall system feasibility. 相似文献
32.
The type I adenylyl cyclase is directly stimulated by Ca2+ and calmodulin in vitro, and the enzyme is also stimulated by increases in intracellular Ca2+ in vivo. Ca2+ stimulation of the enzyme in vivo may be due to direct interactions of the enzyme with Ca2+ and calmodulin or to an indirect mechanism involving stimulation of the enzyme by Ca(2+)-activated protein kinases. In this study, we have made several point mutations within the calmodulin binding domain to determine if the Ca2+ sensitivity of the enzyme can be modified by mutagenesis. The catalytic activities of the mutant enzymes were comparable to wild type type I adenylyl cyclase. Substitution of Cys-507 with Ser-507 did not have significant effects on the calmodulin or Ca2+ sensitivity of the enzyme. However, replacement of Lys-504 with Asp caused a 4-fold decrease in sensitivity to Ca2+. Ca2+ and calmodulin stimulation were abolished by substitution of Phe-503 with Arg-503. Stimulation of type I adenylyl cyclase activity in vivo by intracellular Ca2+ was also greatly diminished with the Arg-503 mutant indicating that Ca2+ stimulation of the enzyme in vivo is due primarily to direct interactions with calmodulin and Ca2+. These data demonstrate that the Ca2+ sensitivity of this enzyme can be modulated by point mutagenesis within the putative calmodulin binding domain and indicate that the enzyme can be directly regulated by Ca2+ and calmodulin in vivo. 相似文献
33.
34.
35.
Joo-Sik Yoo William W. Schultz 《International Journal of Heat and Mass Transfer》2003,46(24):4747-4750
This study considers a small Rayleigh number thermal convection in a fluid-saturated porous medium between two infinite-horizontal walls. The lower and upper walls have sinusoidal temperature distributions with a wave number and a phase difference, and the effect of the parameters on the flow and heat transfer characteristics is investigated. For a given wave number, an out-of-phase configuration yields minimum heat transfer at the walls. Maximum heat transfer occurs at the wave number of 2.286 with an in-phase configuration. 相似文献
36.
We have compared light chain immunohistochemistry in reactive lymphoid tissue and a series of paraffin-embedded B-cell lymphomas using standard trypsin digestion with a heat mediated epitope retrieval method. Fifty-seven B-cell lymphomas (18 high grade, 29 low grade and 10 cases of nodular lymphocyte predominance Hodgkin's disease), two reactive lymph nodes and eight tonsils fixed for known times between 12 h and 2 years were studied. Paraffin-embedded tissue was stained with polyclonal anti-kappa and anti-lambda antibodies. For each antibody staining was performed on two sections, one treated with trypsin digestion and one with microwave heating. Sections were scored from 0 to + + + with 0 representing poor staining and + + + excellent staining. A score of ++ was considered satisfactory. Light chain restriction was recorded if present. Satisfactory staining was obtained in 34/59 cases using trypsin digestion and 56/59 cases using heat retrieval. Light chain restriction was demonstrated in 32/57 (56%) B-cell lymphomas using trypsin digestion and 52/57 (91%) using heat retrieval. Satisfactory staining was obtained in tonsils fixed for up to 48 h using trypsin digestion and up to 2 years using heat retrieval. We have shown that for light chain immunostaining a heat mediated epitope retrieval method produces more consistent and satisfactory results and is effective over a greater range of fixation times than traditional trypsin digestion. 相似文献
37.
Renal scarring is considered a criterion of reflux nephropathy and the end stage of pyelonephritis. Prednisolone, a strong anti-inflammatory drug, at doses of 1 or 2 mg/kg prevented renal scarring in rats following infection with Serratia marcescens. Four or 8 mg/kg of prednisolone, however, did not inhibit renal scar formation. In a time course experiment, renal scarring was prevented when 4-day treatment with prednisolone was initiated 2, 5, or 13 days after infection. These results show that prednisolone is effective in preventing such scarring and suggest the clinical use of this drug for preventing renal scar formation after pyelonephritis and reflux nephropathy. 相似文献
38.
39.
This study was designed to evaluate factors that affect blood volumes transferred to skin during simulated needlestick injuries in an in vitro paper prefilter model and an ex vivo porcine tissue model. The effect of needle type and size, penetration depth, and glove use on the volume of radiolabeled blood transferred was determined in each model. Blood volumes ranged from 0.47 +/- 0.26 microL (30-gauge needle, 0.5-cm depth, in vitro model) to 5.88 +/- 1.45 microL (18-gauge needle, 2.0-cm depth, in vitro model). Needle size and penetration depth were significantly associated with transfer volume. Glove material reduced the transferred blood volume by 46%-86% in both models. Transfer volumes were within the same order of magnitude for all conditions. Hence, virus titer in the source blood may be a better predictor of needlestick infectivity than is exposure volume. Regardless, gloves may exert some protective effect and should be worn whenever needles are handled. 相似文献
40.
The final stage in the production of a radiotherapy treatment plan must always be an independent check that the linear accelerator settings given on the plan do in fact deliver the required dose distribution. A tool is described that enables rapid checking of diaphragm settings in relation to the patient. 相似文献