全文获取类型
收费全文 | 30325篇 |
免费 | 1432篇 |
国内免费 | 216篇 |
专业分类
电工技术 | 547篇 |
综合类 | 358篇 |
化学工业 | 4982篇 |
金属工艺 | 841篇 |
机械仪表 | 739篇 |
建筑科学 | 850篇 |
矿业工程 | 190篇 |
能源动力 | 490篇 |
轻工业 | 4100篇 |
水利工程 | 223篇 |
石油天然气 | 163篇 |
武器工业 | 17篇 |
无线电 | 1669篇 |
一般工业技术 | 5435篇 |
冶金工业 | 7566篇 |
原子能技术 | 182篇 |
自动化技术 | 3621篇 |
出版年
2023年 | 310篇 |
2022年 | 262篇 |
2021年 | 622篇 |
2020年 | 519篇 |
2019年 | 440篇 |
2018年 | 912篇 |
2017年 | 817篇 |
2016年 | 922篇 |
2015年 | 811篇 |
2014年 | 958篇 |
2013年 | 1781篇 |
2012年 | 1357篇 |
2011年 | 1346篇 |
2010年 | 1147篇 |
2009年 | 1102篇 |
2008年 | 1247篇 |
2007年 | 1198篇 |
2006年 | 866篇 |
2005年 | 690篇 |
2004年 | 547篇 |
2003年 | 601篇 |
2002年 | 621篇 |
2001年 | 509篇 |
2000年 | 387篇 |
1999年 | 491篇 |
1998年 | 2362篇 |
1997年 | 1416篇 |
1996年 | 983篇 |
1995年 | 603篇 |
1994年 | 492篇 |
1993年 | 435篇 |
1992年 | 178篇 |
1991年 | 186篇 |
1990年 | 156篇 |
1989年 | 166篇 |
1988年 | 153篇 |
1987年 | 163篇 |
1986年 | 146篇 |
1985年 | 227篇 |
1984年 | 189篇 |
1983年 | 169篇 |
1982年 | 129篇 |
1981年 | 179篇 |
1980年 | 177篇 |
1979年 | 125篇 |
1978年 | 106篇 |
1977年 | 226篇 |
1976年 | 489篇 |
1974年 | 88篇 |
1973年 | 113篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The stabilizing free energy of beta-trypsin was determined by hydrogen ion titration. In the pH range from 3.0 to 7.0, the change in free energy difference for the stabilization of the native protein relative to the unfolded one (delta delta G0 titration) was 9.51 +/- 0.06 kcal/mol. An isoelectric point of 10.0 was determined, allowing us to calculate the Tanford and Kirkwood electrostatic factor w. This factor presented a nonlinear behavior and indicated more than one type of titratable carboxyl groups in beta-trypsin. In fact, one class of carboxyl group with a pK = 3.91 +/- 0.01 and another one with a pK = 4.63 +/- 0.03 were also found by hydrogen ion titration of the protein in the folded state. 相似文献
92.
The paper describes a program of experiments for speed reduction on 28 through roads in Nordrhein-Westfalen. In the process, different measures of construction, design, and traffic control were examined to determine their usefulness to reduce speed and to improve road safety. The need for systematic evaluation of a catalogue of measures partly resulted in unsatisfactory design conceptions for the through roads. The evaluation of the effects of the program has been carried out by use of before-and-after-studies of large extent. The speed measurements show that a distinct speed reduction can be obtained only from selected physical improvements. Measures based on optical effects and traffic signs were found to have very little effect on vehicle speeds. Furthermore, in light of the relatively small number of accidents that occur on the selected facilities, it was not possible to establish the beneficial impact of each specific control measure with statistical certainty. However, the results of the experiment have had an influence on the current definition of new design standards for main urban streets in Germany. 相似文献
93.
94.
95.
96.
M Bachmann R Theus J Lüthy C Schlatter 《Zeitschrift für Lebensmittel-Untersuchung und -Forschung》1985,181(5):375-378
A total of six cows, divided into 3 groups, were fed various amounts of rape cake containing 6 g of goitrin/kg over a period of 7 days. The cows were milked twice a day and the goitrin content of the heated milk samples were determined by a HPLC-method within 2 h. When rape cake was fed at 0.39, 1.9 and 3.9% resp. of the total feed this resulted in medium goitrin values of 37, 163 and 707 micrograms/l milk. These values correspond to a transfer of about 0.1% of the original progoitrin content in the feed. 12 h after the last rape feeding the amount of goitrin in the milk was below the detection limit of 7 ppb. The toxicological significance of these findings are dicussed. 相似文献
97.
European Food Research and Technology - Bei Bestimmungen des Proteingehalts von Haselnüssen in verschiedenen Handelsprodukten wie Nuß-Nougatcremes and Nußmus mit der... 相似文献
98.
该文从设计、施工和运行管理等方面介绍了高喷板墙、减压井、充填灌浆以及开挖导渗等技术在飞来峡水利枢纽社岗防护堤中的应用情况,探讨了堤坝渗漏综合防治的技术措施和有关问题。 相似文献
99.
C. R. Hutchinson H. S. Zurob Y. Bréchet 《Metallurgical and Materials Transactions A》2006,37(6):1711-1720
The growth of allotriomorphic ferrite from austenite in Fe-C-X alloys is studied. Two systems have been selected: the Fe-C-Ni
system, in which the substitutional alloying element is expected to have a weak interaction with both the C and the moving
interface, and the Fe-C-Mo system, in which these interactions are expected to be non-negligible. The ferrite growth kinetics
was measured using two types of experiments: classical isothermal heat treatments and decarburization experiments. All of
the experimental observations can be quantitatively rationalized using a model that describes an evolution in interfacial
conditions from paraequilibrium (PE) to local equilibrium with negligible partitioning (LENP) during growth.
This article is based on a presentation made in the “Hillert Symposium on Thermodynamics & Kinetics of Migrating Interfaces
in Steels and Other Complex Alloys,” December 2–3, 2004, organized by the The Royal Institute of Technology in Stockholm,
Sweden. 相似文献
100.
Poor sanitation and insufficient disposal of sewage and faeces are primarily responsible for water associated health problems in developing countries. Domestic sewage and faeces are prevalently discharged into surface waters which are used by the inhabitants as a source for drinking water. This paper presents a decentralized anaerobic process technique for handling of such domestic organic waste. Such an efficient and compact system for treating faeces and food waste may be of great benefit for developing countries. Besides a stable biogas production for energy generation, the reduction of bacterial pathogens is of particular importance. In our research we investigated the removal capacity of the reactor concerning pathogens, which has been operated under thermophilic conditions. Faecal coliforms and intestinal enterococci have been detected as indicator organisms for bacterial pathogens. By the multiple regression analysis technique an empirical mathematical model has been developed. The model shows a high correlation between removal efficiency and both, hydraulic retention time (HRT) and temperature. By this model an optimized HRT for defined bacterial pathogens effluent standards can be easily calculated. Thus, hygiene potential can be evaluated along with economic aspects. In this paper not only results for describing the hygiene potential of a thermophilic anaerobic bioreactor are presented, but also an exemplary method to draw the right conclusions out of biological tests with the aid of mathematical tools. 相似文献