全文获取类型
收费全文 | 2830篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 235篇 |
金属工艺 | 11篇 |
机械仪表 | 33篇 |
建筑科学 | 40篇 |
矿业工程 | 1篇 |
能源动力 | 22篇 |
轻工业 | 120篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 85篇 |
一般工业技术 | 144篇 |
冶金工业 | 2018篇 |
原子能技术 | 9篇 |
自动化技术 | 128篇 |
出版年
2023年 | 11篇 |
2022年 | 9篇 |
2021年 | 21篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 33篇 |
2017年 | 17篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 26篇 |
2013年 | 56篇 |
2012年 | 28篇 |
2011年 | 42篇 |
2010年 | 34篇 |
2009年 | 39篇 |
2008年 | 40篇 |
2007年 | 48篇 |
2006年 | 32篇 |
2005年 | 31篇 |
2004年 | 25篇 |
2003年 | 36篇 |
2002年 | 23篇 |
2001年 | 16篇 |
2000年 | 23篇 |
1999年 | 75篇 |
1998年 | 569篇 |
1997年 | 351篇 |
1996年 | 242篇 |
1995年 | 122篇 |
1994年 | 121篇 |
1993年 | 143篇 |
1992年 | 25篇 |
1991年 | 44篇 |
1990年 | 33篇 |
1989年 | 32篇 |
1988年 | 38篇 |
1987年 | 23篇 |
1986年 | 21篇 |
1985年 | 35篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 24篇 |
1980年 | 22篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 63篇 |
1976年 | 123篇 |
1973年 | 10篇 |
1971年 | 6篇 |
排序方式: 共有2865条查询结果,搜索用时 15 毫秒
81.
82.
Developing a green IT strategy for any organization, large or small, is critical to establishing a culture where the focus is on reducing cost and addressing both imminent regulatory pressure and increased scrutiny of carbon-neutral strategies. This paper discusses the "green practices" that can be used by organisations for energy efficiency improvements and also to avoid potential disruptions to existing infrastructure. 相似文献
83.
Leif?W.?Lundmark Chong?OhEmail author J.?Cameron?Verhaal 《Information Systems Frontiers》2017,19(6):1407-1422
Drawing on the organizational legitimacy literature, we propose and test a set of hypotheses arguing that social media, an artifact of information technology, serves as a mechanism for conferring legitimacy in the market for initial public offerings (IPOs). The extant literature identifies third-party authorities, such as traditional media outlets and industry analysts, as a valuable source of organizational legitimacy. Social media and micro-blogging, however, remain outside current classifications of the phenomenon. This study theoretically develops and empirically tests a new mechanism in the legitimation process: the direct interaction with potential investors and society-at-large via social media. Our findings indicate broad support that having a Twitter account, and the extent to which a firm utilizes Twitter, is associated with systematically higher levels of IPO underpricing. Moreover, we find support that social media variables external to the firm, including number of followers and retweets, also impact the level of underpricing in an IPO. In conclusion, we highlight the emerging role of social media in processes of legitimation and invite additional research at the intersection of IS and management. 相似文献
84.
Analysis of factors contributing to success in a program of micromanipulation-assisted fertilization
GJ Garrisi AJ Chin PM Dolan HM Nagler M Vasquez-Levin D Navot JW Gordon 《Canadian Metallurgical Quarterly》1993,59(2):366-374
OBJECTIVE: To determine factors important to clinical success in micromanipulation-assisted in vitro fertilization (IVF). DESIGN: Procedures invoked in two separate series of micromanipulation-assisted IVF cycles, one unsuccessful (series I) and the other successful (series II), were compared in an effort to identify changes that led to clinical success. SETTING: University-based IVF clinic. PATIENTS: In both IVF series involving micromanipulation, patients consisted of infertile couples who fit any of five categories of male-factor related infertility. The female patients underwent controlled hyperstimulation for oocyte retrieval and the oocytes were inseminated normally or were subjected either to partial zona dissection or subzonal sperm insertion to assist fertilization. Results in all groups were compared between the two patient series. RESULTS: In the successful series II, a noticeable improvement in fertilization rate and embryo quality was observed compared with series I. A significant increase in the percentage of patients reaching embryo transfer, the pregnancy rate per transfer, and the pregnancy rate per retrieval were noted in series II; a 25% ongoing pregnancy rate per retrieval was observed overall in this successful group, with "ongoing" defined as manifestation of at least a fetal sac on ultrasound with no detectable problems. Patients with a mixed transfer of embryos derived from manipulated and normally inseminated oocytes had a 75% rate of pregnancy per transfer in series II. Differences between the two series could not be attributed to patient selection or biases in selection of oocytes relegated to micromanipulation. However, oocyte handling, micromanipulation, and culture protocols differed significantly between the two series in that temperature and pH of oocytes was better controlled, and micromanipulation time was minimized in series II. CONCLUSION: Success in micromanipulation depends on maintenance of the oocyte in a stable and supportive environment throughout the micromanipulation procedure. It is also important to minimize trauma to the eggs by performing micromanipulation rapidly and with minimal distortion of the egg. Patients with a poor fertilization rate in standard IVF may experience a substantial increase in the likelihood of pregnancy when micromanipulation-assisted fertilization is performed on some eggs. 相似文献
85.
86.
R. F. Cameron S. McKee 《International journal for numerical methods in engineering》1983,19(10):1527-1536
In this paper we present orsder three, four and five backward product integration methods for the generalized Abel equation We illustrate their use by silving the small angle deflection problem, and show computationally that these methods are convergent for all ? ?(0,1). The coefficients of order three and four methods are given in Applenidx I. 相似文献
87.
In the intensive care unit patients benefit from being fed and from having well controlled glucose levels. Insulin and glucose infusion serves as manipulated inputs to regulate blood glucose, while glucose infusion serves as a sole nutritional input. In this paper, a model predictive control strategy, based on simultaneously manipulating glucose and insulin infusion, is developed to improve blood glucose regulation in intensive care unit patients. In the short term, glucose infusion is used for tighter glucose control, particularly for disturbance rejection, while, in the long-term (24 h period), glucose infusion is used to meet nutritional needs. The “habituating control” algorithm is proposed and tested against a model predictive control (MPC) strategy that only manipulates insulin. The simulation results indicate that the Habituating MPC strategy outperforms the single input–single output MPC by providing faster setpoint tracking and tighter glucose control for a patient population, and producing less glucose variability while rejecting disturbances in insulin infusion and insulin sensitivity. 相似文献
88.
MacDonald Angus W. III; Goghari Vina M.; Hicks Brian M.; Flory Janine D.; Carter Cameron S.; Manuck Stephen B. 《Canadian Metallurgical Quarterly》2005,19(6):814
Convergent and divergent validity are critically important in developing psychological measures that reveal interpretable deficits in disordered populations. This article reports on 2 studies that evaluated the validity of context processing measures. In Experiment 1, a confirmatory factor analysis of data from 481 healthy adults established the convergent validity of 2 context processing measures and showed that context processing accounted for significant amounts of variance in standard IQ and working memory measures. In Experiment 2, 20 schizophrenia patients, 16 of their healthy siblings, and 28 controls were evaluated using a novel, short context processing measure, the dot pattern expectancy (DPX) task. The DPX was sensitive to specific deficits in schizophrenia patients and their healthy siblings. These findings support the construct validity of context processing measures, suggest context processing is a component of intellectual functioning, and demonstrate that brief context processing measures remain sensitive to psychopathological deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
89.
Howard Bowman Helen Cameron Peter King Simon Thompson 《Formal Methods in System Design》2003,22(1):5-38
This paper explores a formalism for describing a wide class of multimedia document constraints, based on an interval temporal logic. We describe the requirements that arise from the multimedia documents application area, and we illustrate these requirements using several examples. Then we present the temporal logic formalism that we use. This logic extends existing interval temporal logic with a number of new features: actions, framing of actions, past operators, a projection-like operator called filter and a new handling of interval length. The notation is applied to the specification of the examples, and in particular a set of logical manipulations, providing feedback to an author, is presented. A model theory, logic and satisfaction relation are defined for the notation. 相似文献
90.
Conley R Liu C Qian J Kewish CM Macrander AT Yan H Kang HC Maser J Stephenson GB 《The Review of scientific instruments》2008,79(5):053104
A multilayer Laue lens (MLL) is an x-ray focusing optic fabricated from a multilayer structure consisting of thousands of layers of two different materials produced by thin-film deposition. The sequence of layer thicknesses is controlled to satisfy the Fresnel zone plate law and the multilayer is sectioned to form the optic. An improved MLL geometry can be created by growing each layer with an in-plane thickness gradient to form a wedge, so that every interface makes the correct angle with the incident beam for symmetric Bragg diffraction. The ultimate hard x-ray focusing performance of a wedged MLL has been predicted to be significantly better than that of a nonwedged MLL, giving subnanometer resolution with high efficiency. Here, we describe a method to deposit the multilayer structure needed for an ideal wedged MLL and report our initial deposition results to produce these structures. 相似文献