全文获取类型
收费全文 | 10578篇 |
免费 | 373篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 151篇 |
综合类 | 5篇 |
化学工业 | 2487篇 |
金属工艺 | 222篇 |
机械仪表 | 185篇 |
建筑科学 | 532篇 |
矿业工程 | 11篇 |
能源动力 | 295篇 |
轻工业 | 835篇 |
水利工程 | 70篇 |
石油天然气 | 26篇 |
武器工业 | 3篇 |
无线电 | 925篇 |
一般工业技术 | 1739篇 |
冶金工业 | 1540篇 |
原子能技术 | 74篇 |
自动化技术 | 1867篇 |
出版年
2022年 | 118篇 |
2021年 | 165篇 |
2020年 | 148篇 |
2019年 | 173篇 |
2018年 | 194篇 |
2017年 | 172篇 |
2016年 | 220篇 |
2015年 | 206篇 |
2014年 | 291篇 |
2013年 | 626篇 |
2012年 | 463篇 |
2011年 | 627篇 |
2010年 | 491篇 |
2009年 | 426篇 |
2008年 | 544篇 |
2007年 | 479篇 |
2006年 | 437篇 |
2005年 | 349篇 |
2004年 | 324篇 |
2003年 | 293篇 |
2002年 | 314篇 |
2001年 | 159篇 |
2000年 | 159篇 |
1999年 | 164篇 |
1998年 | 164篇 |
1997年 | 179篇 |
1996年 | 170篇 |
1995年 | 171篇 |
1994年 | 169篇 |
1993年 | 139篇 |
1992年 | 137篇 |
1991年 | 105篇 |
1990年 | 125篇 |
1989年 | 135篇 |
1988年 | 88篇 |
1987年 | 85篇 |
1986年 | 105篇 |
1985年 | 136篇 |
1984年 | 118篇 |
1983年 | 131篇 |
1982年 | 128篇 |
1981年 | 120篇 |
1980年 | 90篇 |
1979年 | 104篇 |
1978年 | 75篇 |
1977年 | 83篇 |
1976年 | 77篇 |
1975年 | 74篇 |
1974年 | 62篇 |
1973年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Higher testosterone levels are related to assertiveness and dominance. Given the relevance of those behavioral correlates to spouses' daily transactions, links between testosterone levels and marital interaction were explored among 92 newlywed couples. Marital problem-solving and social support transactions were assessed, and saliva was collected and assayed for testosterone. Whether marital behavior was related to husbands' and wives' testosterone levels was examined. The link between spouses' testosterone and their behavior was contingent on the partner's testosterone levels. Husbands exhibited more adaptive problem-solving behaviors and social support provision when husbands and wives were concordant for lower testosterone levels. In contrast, wives exhibited more adaptive support provision when spouses had discordant testosterone levels such that wives had higher levels and husbands had lower levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
Swaminathan Sivasubramanian Guillaume Pierre Maarten van Steen Gustavo Alonso 《Internet Computing, IEEE》2007,11(1):60-66
Developers often use replication and caching mechanisms to enhance Web application performance. The authors present a qualitative and quantitative analysis of state-of-the art replication and caching techniques used to host Web applications. Their analysis shows that selecting the best mechanism depends heavily on data workload and requires a careful review of the application's characteristics. They also propose a technique for Web practitioners to compare different mechanisms' performance on their own 相似文献
13.
Alan Royce Jiwaji Suryawanshi Udayan Shah Krishna Vishnupad 《Drug development and industrial pharmacy》1996,22(9):917-924
A melt granulation process has been investigated (1, 2) which efficiently agglomerates pharmaceutical powders for use in both immediate- and sustained-release solid dosage forms. The process utilizes materials that are effective as granulating fluids when they are in the molten state. Cooling of the agglomerated powders and the resultant solidification of the molten materials completes the granulation process. Both the molten agglomeration and cooling solidification were accomplished in a high shear Collette Gral mixer equipped with a jacketed bowl. Hence, the melt granulation process replaces the conventional granulation and drying operations which use water or alcohol solutions. The melt granulation process has been investigated using immediate- and sustained-release TAVIST® (clemastine fumarate USP) tablet formulations. The TAVIST granulations have been characterized by power consumption monitoring, measurement of the granulation particle size distribution, bulk and tapped density determinations, and loss-on-drying measurements. Scale-up of the melt granulation process for the sustained release TAVIST tablet formulation was judged successful based on a comparison of the hardness, friability, weight uniformity during compression, disintegration time, and dissolution rate data obtained at different manufacturing scales. 相似文献
14.
15.
Lei Guo Lennart Ljung Pierre Priouret 《International Journal of Adaptive Control and Signal Processing》1993,7(6):525-537
An analysis is given of the performance of the standard forgetting factor recursive least squares (RLS) algorithm when used for tracking time-varying linear regression models. Three basic results are obtained: (1) the ‘P-matrix’ in the algorithm remains bounded if and only if the (time-varying) covariance matrix of the regressors is uniformly non-singular; (2) if so, the parameter tracking error covariance matrix is of the order O(μ + γ2/μ), where μ = 1 - λ, λ is the forgetting factor and γ is a quantity reflecting the speed of the parameter variations; (3) this covariance matrix can be arbitrarily well approximated (for small enough μ) by an expression that is easy to compute. 相似文献
16.
This paper surveys recent research in deliberative real-time artificial intelligence (AI). Major areas of study have beenanytime algorithms, approximate processing, and large system architectures. We describe several systems in each of these areas, focusing both on progress within the field, and the costs, benefits and interactions among different problem and algorithm complexity limitations used in the surveyed work. 相似文献
17.
Male rats were fed 100 nM dichlorodiphenyltrichloroethane-14C in oil by gastric tube. Recovery of dichlorodiphenyltrichloroethane-14C in thoracic duct lymph was 60% in 12 hr. Lymph dichlorodiphenyltrichloroethane-14C (97%) occurred in lipoproteins of d<1.006, designated chylomicrons. Mechanical separation of chylomicron triglyceride core
(labeled with triglyceride-3H) from chylomicron membrane (labeled with phospholipid-32P) showed that 97% dichlorodiphenyltrichloroethane-14C was present in triglyceride core. To investigate possible association of plasma clearance of the two core lipids, rats were
pulse injected with chylomicrons, doubly labeled with triglyceride-3H and dichlorodiphenyltrichloroethane-14C. The decay of dichlorodiphenyltrichloroethane-14C in sequential serum samples was rapid (T1/2=2 min) and was independent of triglyceride-3H decay. In tissues removed 14 min after injection of chylomicrons, 30% administered dichlorodiphenyltrichloroethane-14C was found in liver but only 1% in adipose tissue. In hepatectomized (eviscerated) rats, the decay of serum dichlorodiphenyltrichloroethane-14C (T1/2=10 min) was also independent of and more rapid than triglyceride-3H decay. With sucrose density gradients, it was shown that chylomicron dichlorodiphenyltrichloroethane-14C transferred to higher density serum proteins in vitro and in vivo and to bovine albumin in vitro. Thus, dichlorodiphenyltrichloroethane
was transported from intestine largely in the triglyderide phase of chylomicrons; disappearance of chylomicron-dichlorodiphenyltrichloroethane
from the systemic circulation was rapid and partly independent of the presence of the liver and of triglyceride hydrolysis;
some dichlorodiphenyltrichloroethane was transported from serum chylomicrons to albumin or other plasma proteins before tissue
uptake. 相似文献
18.
Theresa E. Gentle Alan R. Bassindale 《Journal of Inorganic and Organometallic Polymers》1995,5(3):281-294
We have recently reported the synthesis of octopus molecules of defined shape and size with molecular weights well into the thousands. These octopus molecules were made by placing eight pendant groups symmetrically about a central silsesquioxane core via the H2PtCl6 catalyzed hydrosilylation of 1-alkenes as well as vinyl- and allyl-siloxanes by T8 hydrogen silsesquioxane, (HSiO32)8. The chemistry of addition was studied and it was found that while the addition of the 1-alkenes to T8 was regioprecise with only -addition being observed, both - and -addition occurred with vinyl-siloxane. In addition, H-vinyl exchange on silicon was observed to occur with addition of vinyl-siloxane to T8. In the current studies, the effect of the hydrosilylation catalyst. homogeneous and heterogeneous, on the regioselectivity of addition and on the extent of exchange on silicon was evaluated. It was found that the heterogeneous catalysts Pt–C, sulfided Pt–C, and Rh–C required higher temperature and longer times to get complete reaction than the homogeneous catalysts. H2PtCl6 and the tetramethyldivinyldisiloxane complex of Pt. Pd supported catalysts were not effective catalysts for this hydrosilylation. The extent of exchange on silicon and the degree of the second mode of addition occurring were higher with the heterogenous catalysts and may be a result of the higher reaction temperatures. 相似文献
19.
In industrial situations, coals interact with solvents or additives to produce liquid fuels, solvent-refined coal, coal extract and metallurgical coke. In these processes there occurs a wide variation in effects or modifications of the coal by these additives. This paper describes the modifications which can occur, using a wide range of rank of coal, when these coals interact and are co-carbonized with a wide range of additives of different chemical properties. The optical texture of the resultant cokes is given special attention. The objective of the paper is to summarize the current state of knowledge of the mechanisms of these interactions. Possible mechanisms of interactions are summarized, kinetic and chemical structural aspects of reactions are outlined, the importance is mentioned of the formation of liquid phases enabling anisotropic optical textures in modified cokes to be created, and the industrial relevance of its possible development is discussed. 相似文献
20.
The paper gives a general survey of the factors contributing to the deactivation of metal catalysts employed in liquid phase reactions for the synthesis of fine or intermediate chemicals. The main causes of catalyst deactivation are particle sintering, metal and support leaching, deposition of inactive metal layers or polymeric species, and poisoning by strongly adsorbed species. Weakly adsorbed species, poisons at low surface coverage and solvents, may act as selectivity promoters or modifiers. Three examples of long term stability studies carried out in trickle-bed reactor (glucose to sorbitol hydrogenation on Ru/C catalysts, hydroxypropanal to 1,3-propanediol hydrogenation on Ru/TiO2 catalysts, and wet air oxidation of paper pulp effluents on Ru/TiO2) are discussed. 相似文献