全文获取类型
收费全文 | 5254篇 |
免费 | 139篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 60篇 |
综合类 | 4篇 |
化学工业 | 683篇 |
金属工艺 | 89篇 |
机械仪表 | 80篇 |
建筑科学 | 166篇 |
矿业工程 | 6篇 |
能源动力 | 119篇 |
轻工业 | 403篇 |
水利工程 | 35篇 |
石油天然气 | 36篇 |
无线电 | 458篇 |
一般工业技术 | 781篇 |
冶金工业 | 1679篇 |
原子能技术 | 60篇 |
自动化技术 | 736篇 |
出版年
2022年 | 30篇 |
2021年 | 33篇 |
2019年 | 46篇 |
2018年 | 59篇 |
2017年 | 61篇 |
2016年 | 46篇 |
2015年 | 55篇 |
2014年 | 101篇 |
2013年 | 248篇 |
2012年 | 94篇 |
2011年 | 147篇 |
2010年 | 143篇 |
2009年 | 135篇 |
2008年 | 155篇 |
2007年 | 158篇 |
2006年 | 145篇 |
2005年 | 108篇 |
2004年 | 115篇 |
2003年 | 129篇 |
2002年 | 121篇 |
2001年 | 118篇 |
2000年 | 105篇 |
1999年 | 132篇 |
1998年 | 435篇 |
1997年 | 261篇 |
1996年 | 209篇 |
1995年 | 147篇 |
1994年 | 134篇 |
1993年 | 133篇 |
1992年 | 84篇 |
1991年 | 85篇 |
1990年 | 75篇 |
1989年 | 82篇 |
1988年 | 72篇 |
1987年 | 66篇 |
1986年 | 52篇 |
1985年 | 65篇 |
1984年 | 69篇 |
1983年 | 69篇 |
1982年 | 55篇 |
1981年 | 59篇 |
1980年 | 58篇 |
1979年 | 64篇 |
1978年 | 54篇 |
1977年 | 74篇 |
1976年 | 116篇 |
1975年 | 54篇 |
1974年 | 40篇 |
1973年 | 30篇 |
1972年 | 33篇 |
排序方式: 共有5395条查询结果,搜索用时 109 毫秒
81.
N Ben-Ami A Radko U Ben-Ami K Lieberman Z Rothman I Rabin A Lewis 《Canadian Metallurgical Quarterly》1998,71(1-4):321-325
Simultaneous near-field scanning optical and atomic force imaging of bacteria is presented. The bacteria imaged in these studies were unstained. The near-field optical images had excellent signal-to-noise and showed excellent contrast even in these unstained specimens. The images obtained were interpreted in terms of the images that have been obtained by transmission electron microscopy and X-ray imaging. The results show that bacterial near-field optical imaging is going to be a very important tool in the arsenal of the bacteriologist both in terms of understanding the fundamental processes in the life cycle of bacteria with and without cytochemical staining and in terms of clinical diagnostic applications. 相似文献
82.
There exists a movement within the field of psychology to incorporate religious material into the overall conceptualization and treatment of the client. This article questions the appropriateness of such incorporation and emphasizes instead the distinction the therapist needs to make between religious and psychological material in the psychotherapeutic setting. The therapist must also be aware of how religious material can intensify the transference, resistance, and countertransference, thereby complicating the therapeutic process. Client issues that relate to the religious identity of the therapist or invoke a sense of exclusive similarity in the therapeutic dyad can further complicate the therapy. Such complications suggest that the avoidance of both overt and covert messages that communicate the therapist's personal values and beliefs may be beneficial for therapy. Case examples with 4 clients (aged 18–56 yrs) are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
83.
Wang K. Bryant C. Carlson M. Elmer T. Harris A. Garcia M. Hui C.S. Leong C.K. Reynolds B. Tang R. Weber L. Wenzel J. Wilson G. Becker M. 《Micro, IEEE》1995,15(2):44-49
The MPC105 peripheral component interconnection bridge/memory controller provides a platform-specification-compliant bridge between Power PC microprocessors and the PCI bus. With it, designers can create systems using peripherals already designed for a variety of standard PC interfaces. This bridge chip also integrates a secondary cache controller and high-performance memory controller that supports DRAM or synchronous DRAM and ROM or flash ROM 相似文献
84.
85.
86.
During studies to develop serum tests of small intestinal permeability, we detected an unidentified disaccharide in HPLC traces of sera from untreated celiacs. This present study aimed to identify the disaccharide and determine whether the presence of the disaccharide in the serum after an oral challenge had potential as a simple screening test for celiac disease. The disaccharide was identified as sucrose by incubation studies of sera with disaccharidases. Twenty untreated celiacs, 15 treated celiacs, and 20 normal or dyspeptic controls were studied for the presence of sucrose in their serum after an oral load (8 g). The results in celiacs were compared with the presence of serum IgA endomysial antibodies. The 10 normal controls were also given a larger sucrose challenge (50 g). Ten of the untreated celiacs and 10 controls had their brush border disaccharidase activities measured. Sucrose eluted in the same position as the unidentified disaccharide in the HPLC trace and the latter could be removed by incubation with sucrase. All untreated celiacs but none of the treated celiacs had sucrose in their serum after the 8-g oral challenge. None of the controls had sucrose in their serum after the 8-g or 50-g challenges. Three untreated celiacs were IgA endomysial antibody negative as were all the treated cases. Brush border sucrase activity was low in untreated celiac disease. The presence of sucrose in the serum after an oral load shows promise as a noninvasive test for celiac disease. 相似文献
87.
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
88.
MJ O'Neill JA Lewis HM Noble S Holland C Mansat JE Farthing G Foster D Noble SJ Lane PJ Sidebottom SM Lynn MV Hayes CJ Dix 《Canadian Metallurgical Quarterly》1998,61(11):1328-1331
Methanolic extracts prepared from the leaves of Lantana camara have been found to inhibit human thrombin. An assay, in which thrombin activity is measured as a function of clot formation from fibrinogen, was used to guide the fractionation and purification of five principal active constituents (1-5), which were all characterized as 5,5-trans-fused cyclic lactone-containing euphane triterpenes. 相似文献
89.
NB Modi YS Lin T Reynolds A Shaheen BJ Christian 《Canadian Metallurgical Quarterly》1998,32(3):397-405
OBJECTIVE: The study aimed to determine the effectiveness of prophylactic medical intervention in reducing the incidence of cystoid macular edema (CME) and the effectiveness of medical treatment for chronic CME after cataract surgery. DESIGN: The study design was a systematic review and meta-analysis of published reports of randomized clinical trials (RCTs). PARTICIPANTS: Sixteen RCTs involving 2898 eyes examining the effectiveness of medical prophylaxis of CME and 4 RCTs involving 187 eyes testing the effectiveness of medical treatment of chronic CME were used in the study. INTERVENTIONS: Medical prophylaxis of treatment (cyclo-oxygenase inhibitors or corticosteroids) versus control (placebo or active treatment) was performed. MAIN OUTCOME MEASURES: Incidence of angiographically diagnosed CME, incidence of clinically significant CME, and vision were measured. RESULTS: Thirty-six articles reported testing a prophylactic medical intervention for CME after cataract surgery. The incidence of CME varied extensively across studies and was related to the study design used. Summary odds ratios (OR) indicated that prophylactic intervention was effective in reducing the incidence of both angiographic CME (OR = 0.36; 95% confidence interval [CI] = 0.28-0.45) and clinically relevant CME (OR = 0.49; 95% CI = 0.33-0.73). There also was a statistically significant positive effect on improving vision (OR = 1.97; 95% CI = 1.14-3.41). A combination of the results of the four RCTs testing medical therapy for chronic CME indicated a treatment benefit in terms of improving final visual acuity by two or more Snellen lines (OR = 2.67; 95% CI = 1.35-5.30). Assessment of the quality of the 20 RCTs included in the meta-analyses indicated problems in the design, execution, and reporting of a number of trials. CONCLUSION: A combination of the results from RCTs indicates that medical prophylaxis for aphakic and pseudophakic CME and medical treatment for chronic CME are beneficial. Because most of the RCTs performed to date have problems related to quality, a well-designed RCT is needed to confirm this result, using clinical CME and vision as outcomes. 相似文献
90.
High concentrations of Zn2+ are found in presynaptic terminals of excitatory neurons in the CNS. Zn2+ can be released during synaptic activity and modulate postsynaptic receptors, but little is known about the possibility that Zn2+ may enter postsynaptic cells and produce dynamic changes in the intracellular Zn2+ concentration ([Zn2+]i). We used fura-2 and magfura-2 to detect the consequences of Zn2+ influx in cultured neurons under conditions that restrict changes in intracellular Ca2+ and Mg2+ concentrations. The resulting ratio changes for both dyes were reversed completely by the Zn2+ chelator, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine, indicating that these dyes are measuring changes in [Zn2+]i. We found that fura-2 was useful in measuring small increases in [Zn2+]i associated with exposure to Zn2+ alone that may be mediated by a Na+/Ca2+ exchanger. Magfura-2, which has a lower affinity for Zn2+, was more useful in measuring larger agonist-stimulated increases in [Zn2+]i. The coapplication of 300 microM Zn2+ and 100 microM glutamate/10 microM glycine resulted in a [Zn2+]i increase that was approximately 40-100 nM in magnitude and could be inhibited by the NMDA receptor antagonist, MK-801 (30 microM), or extracellular Na+. This suggests that Zn2+ influx can occur through at least two different pathways, leading to varying increases in [Zn2+]i. These findings demonstrate the feasibility of measuring changes in [Zn2+]i in neurons. 相似文献