全文获取类型
收费全文 | 3786篇 |
免费 | 221篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 68篇 |
综合类 | 15篇 |
化学工业 | 815篇 |
金属工艺 | 83篇 |
机械仪表 | 74篇 |
建筑科学 | 210篇 |
矿业工程 | 4篇 |
能源动力 | 95篇 |
轻工业 | 381篇 |
水利工程 | 33篇 |
石油天然气 | 23篇 |
无线电 | 293篇 |
一般工业技术 | 629篇 |
冶金工业 | 582篇 |
原子能技术 | 33篇 |
自动化技术 | 670篇 |
出版年
2023年 | 55篇 |
2022年 | 86篇 |
2021年 | 126篇 |
2020年 | 65篇 |
2019年 | 68篇 |
2018年 | 83篇 |
2017年 | 87篇 |
2016年 | 126篇 |
2015年 | 123篇 |
2014年 | 140篇 |
2013年 | 212篇 |
2012年 | 182篇 |
2011年 | 244篇 |
2010年 | 216篇 |
2009年 | 156篇 |
2008年 | 176篇 |
2007年 | 147篇 |
2006年 | 153篇 |
2005年 | 130篇 |
2004年 | 98篇 |
2003年 | 93篇 |
2002年 | 87篇 |
2001年 | 76篇 |
2000年 | 52篇 |
1999年 | 71篇 |
1998年 | 158篇 |
1997年 | 97篇 |
1996年 | 71篇 |
1995年 | 57篇 |
1994年 | 41篇 |
1993年 | 50篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 25篇 |
1989年 | 31篇 |
1988年 | 24篇 |
1987年 | 23篇 |
1986年 | 18篇 |
1985年 | 31篇 |
1984年 | 15篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 37篇 |
1970年 | 8篇 |
1969年 | 11篇 |
排序方式: 共有4008条查询结果,搜索用时 15 毫秒
31.
SA Kliewer JT Moore L Wade JL Staudinger MA Watson SA Jones DD McKee BB Oliver TM Willson RH Zetterstr?m T Perlmann JM Lehmann 《Canadian Metallurgical Quarterly》1998,92(1):73-82
PURPOSE: To determine the effects of 28 d of creatine supplementation during training on body composition, strength, sprint performance, and hematological profiles. METHODS: In a double-blind and randomized manner, 25 NCAA division IA football players were matched-paired and assigned to supplement their diet for 28 d during resistance/agility training (8 h x wk[-1]) with a Phosphagen HP (Experimental and Applied Sciences, Golden, CO) placebo (P) containing 99 g x d(-1) of glucose, 3 g x d(-1) of taurine, 1.1 g x d(-1) of disodium phosphate, and 1.2 g x d(-1) of potassium phosphate (P) or Phosphagen HP containing the P with 15.75 g x d(-1) of HPCE pure creatine monohydrate (HP). Before and after supplementation, fasting blood samples were obtained; total body weight, total body water, and body composition were determined; subjects performed a maximal repetition test on the isotonic bench press, squat, and power clean; and subjects performed a cycle ergometer sprint test (12 x 6-s sprints with 30-s rest recovery). RESULTS: Hematological parameters remained within normal clinical limits for active individuals with no side effects reported. Total body weight significantly increased (P < 0.05) in the HP group (P 0.85 +/- 2.2; HP 2.42 +/- 1.4 kg) while no differences were observed in the percentage of total body water. DEXA scanned body mass (P 0.77 +/- 1.8; HP 2.22 +/- 1.5 kg) and fat/bone-free mass (P 1.33 +/- 1.1; HP 2.43 +/- 1.4 kg) were significantly increased in the HP group. Gains in bench press lifting volume (P -5 +/- 134; HP 225 +/- 246 kg), the sum of bench press, squat, and power clean lifting volume (P 1,105 +/- 429; HP 1,558 +/- 645 kg), and total work performed during the first five 6-s sprints was significantly greater in the HP group. CONCLUSION: The addition of creatine to the glucose/taurine/electrolyte supplement promoted greater gains in fat/bone-free mass, isotonic lifting volume, and sprint performance during intense resistance/agility training. 相似文献
32.
Oliver W. W. Yang 《Performance Evaluation》1995,23(3):261-284
This paper analyzes and compares the slotted time operation and the non-slotted time operation of a singleserver system with deterministic service time. These two operations are commonly used to model discrete service time systems in computer or digital communications. But due to the similarity in their operations and performance, the two models may be mixed up with each other. This paper examines by means of queueing analysis the performance of a few classes of systems that differ in the service order of their customers. The means and variances of the queue lengths, waiting times and interdeparture times of FCFS systems using the slotted time operations are first obtained from their respective LST and generating function equations. These are then used for comparison with those in non-slotted time systems. The results show that although the slotted time operation in the FCFS systems can be approximated by the non-slotted time operations under heavy traffic condition, the performances under other regions and service disciplines (e.g., the LCFS and the priority systems) may deviate significantly. They must be properly adjusted if one wishes to use the simpler equations of the non-slotted time operations to approximate the slotted time operations. The comparison graphs provided in this paper supply adjustments guidelines for the careful designers. 相似文献
33.
AR Barker FN Schrick MJ Lewis HH Dowlen SP Oliver 《Canadian Metallurgical Quarterly》1998,81(5):1285-1290
In the common goby, Pomatoschistus microps (Pisces, Gobiidae), males build nests under mussel shells where they care for the eggs until hatching. To investigate why male common gobies cannibalize their own eggs (filial cannibalism), we conducted a feeding experiment. Males given little food ate from their eggs more often than males given food in excess. However, males given mussel meat in excess did not eat more of their eggs than males fed with both mussel meat in excess and goby eggs. This may suggest that male common gobies cannibalize their eggs to obtain energy rather than essential nutrients lacking in other diets. Moreover, males ate their whole clutch if it was exceptionally small regardless of food treatment, suggesting that males stop investing in their clutch if its reproductive value is less than the cost of guarding it. Thus, whole clutch cannibalism and partial clutch cannibalism seem to be governed by different factors. Furthermore, poorly built nests were associated with starved males, suggesting that nest concealing is costly. There was an association between how well the nest was built and partial clutch filial cannibalism, suggesting that the appearance of the nest may indicate the condition of the male, and thus the risk of filial cannibalism. Copyright 1998 The Association for the Study of Animal Behaviour. 相似文献
34.
RS Veazey DW Horohov JL Krahenbuhl HW Taylor JL Oliver TG Snider 《Canadian Metallurgical Quarterly》1995,47(1-2):79-87
Susceptibility of C57BL/6 (Bcgs) and C3H/HeN (Bcgr) mice to an intraperitoneal infection with Mycobacterium paratuberculosis strain 19698 was compared (by histopathology and the number of mycobacteria isolated from the spleen). Mycobacterial counts from the spleen of Bcgr mice progressively decreased over the course of infection but remained unchanged in Bcgs mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcgs mice, whereas lesions were transient or absent in Bcgr mice. These results indicate that Bcgr mice are inherently resistant to M. paratuberculosis, whereas Bcgs mice are inherently susceptible. These differences may prove useful in elucidating the mechanisms of resistance and susceptibility to paratuberculosis and other mycobacterial infections. 相似文献
35.
36.
Pouria Pirzadeh Junichi Tatemura Oliver Po Hakan Hac?gümü? 《Journal of Grid Computing》2012,10(1):109-132
Recently there has been a considerable increase in the number of different Key-Value stores, for supporting data storage and
applications on the cloud environment. While all these solutions try to offer highly available and scalable services on the
cloud, they are significantly different with each other in terms of the architecture and types of the applications, they try
to support. Considering three widely-used such systems: Cassandra, HBase and Voldemort; in this paper we compare them in terms
of their support for different types of query workloads. We are mainly focused on the range queries. Unlike HBase and Cassandra
that have built-in support for range queries, Voldemort does not support this type of queries via its available API. For this
matter, practical techniques are presented on top of Voldemort to support range queries. Our performance evaluation is based
on mixed query workloads, in the sense that they contain a combination of short and long range queries, beside other types
of typical queries on key-value stores such as lookup and update. We show that there are trade-offs in the performance of
the selected system and scheme, and the types of the query workloads that can be processed efficiently. 相似文献
37.
Oliver Schoett 《Acta Informatica》1992,29(6-7):595-621
Two kinds of finite specification of the behaviour of a counter data type are proved impossible.We consider the class of data types (many-sorted algebras) behaving like an encapsulated counter that can be observed only by a test for zero. It is shown that no nonempty subclass of this class can be finitely specified in observational first-order logic, which is a variant of first-order logic in which equality may not be used on encapsulated types. Secondly, it is shown that the class cannot be described exactly by a finite specification in first-order logic.An extended abstract of a part of this paper appeared as: Schoett, O.: An observational subset of first-order logic cannot speacify the behaviour of a counter, in: Choffrut, C., Jantzen, M. (eds) STACS 91. 8th Annual Symposium on Theoretical Aspects of Computer Science (Lect. Notes comput. Sci., vol. 480, pp. 499–510) Berlin Heidelberg New York: Springer 1991 相似文献
38.
Lisa Goedtke Heike Sprenger Ute Hofmann Felix F. Schmidt Helen S. Hammer Ulrich M. Zanger Oliver Poetz Albrecht Seidel Albert Braeuning Stefanie Hessel-Pras 《International journal of molecular sciences》2021,22(1)
Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants produced by incomplete combustion of organic matter. They induce their own metabolism by upregulating xenobiotic-metabolizing enzymes such as cytochrome P450 monooxygenase 1A1 (CYP1A1) by activating the aryl hydrocarbon receptor (AHR). However, previous studies showed that individual PAHs may also interact with the constitutive androstane receptor (CAR). Here, we studied ten PAHs, different in carcinogenicity classification, for their potential to activate AHR- and CAR-dependent luciferase reporter genes in human liver cells. The majority of investigated PAHs activated AHR, while non-carcinogenic PAHs tended to activate CAR. We further characterized gene expression, protein abundancies and activities of the AHR targets CYP1A1 and 1A2, and the CAR target CYP2B6 in human HepaRG hepatoma cells. Enzyme induction patterns strongly resembled the profiles obtained at the receptor level, with AHR-activating PAHs inducing CYP1A1/1A2 and CAR-activating PAHs inducing CYP2B6. In summary, this study provides evidence that beside well-known activation of AHR, some PAHs also activate CAR, followed by subsequent expression of respective target genes. Furthermore, we found that an increased PAH ring number is associated with AHR activation as well as the induction of DNA double-strand breaks, whereas smaller PAHs activated CAR but showed no DNA-damaging potential. 相似文献
39.
Oliver Schmutzler Sebastian Graf Nils Behm Wael Y. Mansour Florian Blumendorf Theresa Staufer Christian Krnig Dina Salah Yanan Kang Jan N. Peters Yang Liu Neus Feliu Wolfgang J. Parak Anja Burkhardt Elisabetta Gargioni Sabrina Gennis Sharah Chandralingam Finn Heg Wolfgang Maison Kai Rothkamm Florian Schulz Florian Grüner 《International journal of molecular sciences》2021,22(7)
Quantitative cellular in vitro nanoparticle uptake measurements are possible with a large number of different techniques, however, all have their respective restrictions. Here, we demonstrate the application of synchrotron-based X-ray fluorescence imaging (XFI) on prostate tumor cells, which have internalized differently functionalized gold nanoparticles. Total nanoparticle uptake on the order of a few hundred picograms could be conveniently observed with microsamples consisting of only a few hundreds of cells. A comparison with mass spectroscopy quantification is provided, experimental results are both supported and sensitivity limits of this XFI approach extrapolated by Monte-Carlo simulations, yielding a minimum detectable nanoparticle mass of just 5 pg. This study demonstrates the high sensitivity level of XFI, allowing non-destructive uptake measurements with very small microsamples within just seconds of irradiation time. 相似文献