全文获取类型
收费全文 | 5033篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 30篇 |
化学工业 | 316篇 |
金属工艺 | 27篇 |
机械仪表 | 35篇 |
建筑科学 | 116篇 |
矿业工程 | 7篇 |
能源动力 | 48篇 |
轻工业 | 243篇 |
水利工程 | 42篇 |
石油天然气 | 13篇 |
无线电 | 176篇 |
一般工业技术 | 311篇 |
冶金工业 | 3342篇 |
原子能技术 | 24篇 |
自动化技术 | 336篇 |
出版年
2022年 | 16篇 |
2021年 | 17篇 |
2019年 | 22篇 |
2018年 | 22篇 |
2017年 | 19篇 |
2016年 | 28篇 |
2015年 | 21篇 |
2014年 | 39篇 |
2013年 | 101篇 |
2012年 | 70篇 |
2011年 | 84篇 |
2010年 | 64篇 |
2009年 | 91篇 |
2008年 | 83篇 |
2007年 | 85篇 |
2006年 | 79篇 |
2005年 | 60篇 |
2004年 | 75篇 |
2003年 | 78篇 |
2002年 | 57篇 |
2001年 | 62篇 |
2000年 | 53篇 |
1999年 | 124篇 |
1998年 | 893篇 |
1997年 | 544篇 |
1996年 | 406篇 |
1995年 | 220篇 |
1994年 | 180篇 |
1993年 | 243篇 |
1992年 | 63篇 |
1991年 | 68篇 |
1990年 | 78篇 |
1989年 | 68篇 |
1988年 | 52篇 |
1987年 | 62篇 |
1986年 | 61篇 |
1985年 | 68篇 |
1984年 | 36篇 |
1983年 | 33篇 |
1982年 | 43篇 |
1981年 | 49篇 |
1980年 | 40篇 |
1979年 | 16篇 |
1978年 | 21篇 |
1977年 | 98篇 |
1976年 | 217篇 |
1975年 | 21篇 |
1974年 | 19篇 |
1973年 | 21篇 |
1972年 | 14篇 |
排序方式: 共有5066条查询结果,搜索用时 15 毫秒
51.
The recent demonstration that myocardial Ca(2+)-independent phospholipase A2 exists as a complex of catalytic and regulatory polypeptides that is modulated by ATP has suggested a novel mechanisms through which alterations in glycolytic flux can be coupled to the generation of eicosanoids which facilitate insulin secretion. To determine the potential relevance of this mechanism, we examined the kinetic characteristics, substrate specificities, and cellular locus of phospholipase A2 activity in pancreatic islets. Rat pancreatic islets contain a Ca(2+)-independent phospholipase A2 activity which is optimal at physiologic pH, preferentially hydrolyzes phospholipid substrates containing a vinyl ether linkage at the sn-1 position, and prefers arachidonic acid compared to oleic acid in the sn-2 position. Rat islet Ca(2+)-independent phospholipase A2 activity is inhibited by the mechanism-based inhibitor (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one and is stimulated by ATP. Purification of beta-cells from dispersed pancreatic islet cells by fluorescence-activated cell sorting demonstrated that beta-cells (but not non-beta-cells) contain Ca(2+)-independent, ATP-stimulated phospholipase A2 activity. Remarkably, clonal RIN-m5f insulinoma cells, which possess a defect in glucose-induced insulin secretion, contain a Ca(2+)-independent phospholipase A2 which is not modulated by alterations in ATP concentration. Collectively, these results and those of an accompanying paper [Ramanadham et al. (1993) Biochemistry (following paper in this issue)] implicate Ca(2+)-independent phospholipase A2 as a putative glucose sensor which can couple alterations in glycolytic metabolism to the generation of biologically active eicosanoids and thereby facilitate glucose-induced insulin secretion. 相似文献
52.
53.
We reviewed 187 depth recorded seizures in 33 patients with non-lesional temporal lobe complex partial seizures. All patients had a minimum of 1 year follow-up following temporal lobectomy. We classified seizure onset pattern as rhythmic activity, attenuation, or repetitive spikes or spike wave complexes. The most common pattern of seizure onset was rhythmic activity and the next most common pattern was repetitive spikes. Seventy-five seizures (49%) had only one seizure onset pattern, and 79 seizures (51%) had a combination of seizure onset patterns. The degree of hippocampal gliosis strongly predicted the type of seizure onset pattern (Chi square = 24.07, 2 d.f., P < 0.01). The rhythmic activity pattern was associated with mild gliosis, and the repetitive spike pattern was associated with severe gliosis. We classified seizure onset as focal or regional based on the number of electrode contacts that were involved by the ictal EEG. A focal seizure onset was associated with an excellent outcome following temporal lobectomy. 相似文献
54.
ME Hoatlin FE Ferro RW Geib MT Fox SL Kozak D Kabat 《Canadian Metallurgical Quarterly》1995,69(2):856-863
Although the Friend virus-encoded membrane glycoprotein (gp55) activates erythropoietin receptors (EpoR) to cause erythroblastosis only in certain inbred strains of mice but not in other species, mutant viruses can overcome aspects of mouse resistance. Thus, mice homozygous for the resistance allele of the Fv-2 gene are unaffected by gp55 but are susceptible to mutant glycoproteins that have partial deletions in their ecotropic domains. These and other results have suggested that proteins coded for by polymorphic Fv-2 alleles might directly or indirectly interact with EpoR and that changes in gp55 can overcome this defense. A new viral mutant with an exceptionally large deletion in its ecotropic domain is now also shown to overcome Fv-2rr resistance. In all cases, the glycoproteins that activate EpoR are processed to cell surfaces as disulfide-bonded dimers. To initiate analysis of nonmurine resistances, we expressed human EpoR and mouse EpoR in the interleukin 3-dependent mouse cell line BaF3 and compared the abilities of Friend virus-encoded glycoproteins to convert these cells to growth factor independence. Human EpoR was activated in these cells by erythropoietin but was resistant to gp55. However, human EpoR was efficiently activated in these cells by the same viral mutants that overcome Fv-2rr resistance in mice. By construction and analysis of human-mouse EpoR chimeras, we obtained evidence that the cytosolic domain of human EpoR contributes to its resistance to gp55 and that this resistance is mediated by accessory cellular factors. Aspects of host resistance in both murine and nonmurine species are targeted specifically against the ecotropic domain of gp55. 相似文献
55.
J Barrette R Bellwied P Braun-Munzinger WE Cleland T Cormier G Dadusc G David J Dee O Dietzsch M Fatyga SV Greene JV Germani JR Hall TK Hemmick N Herrmann RW Hogue B Hong K Jayananda D Kraus BS Kumar R Lacasse D Lissauer WJ Llope TW Ludlam R Majka SK Mark JT Mitchell M Muthuswamy E O'Brien C Pruneau FS Rotondo da Silva NC J Simon-Gillo U Sonnadara J Stachel H Takai EM Takagui TG Throwe L Waters C Winter D Wolfe CL Woody N Xu Y Zhang Z Zhang C Zou 《Canadian Metallurgical Quarterly》1995,52(5):2679-2683
56.
WJ Schnedl EC Reisinger RW Lipp M Uggowitzer HJ Mischinger P Fickert GJ Krejs 《Canadian Metallurgical Quarterly》1996,23(3):220-223
We reported an operative case of bilateral coronary artery fistulae to pulmonary artery associated with a giant saccular aneurysm, the largest of which measured 30 x 30 mm. The patient was a 75 year old female who had anginal pain due to coronary steal phenomenon. A continuous murmur was detected. After establishing total cardiopulmonary bypass, two distal orifices of the fistula connected to the main pulmonary artery were closed with 5-0 polypropylene plegeted sutures. Aneurysmorrhaphy was then performed for giant saccular aneurysm. Postoperative course was uneventful. 相似文献
57.
W.E. Stewart Jr. A.S. Burns 《International Communications in Heat and Mass Transfer》1992,19(6):859-868
The effects of a permeable inner boundary on the maximum temperature and the convective flows were investigated numerically for a two-dimensional horizontal annulus containing a uniformly heat generating porous media. The time-dependent governing equations were nondimensionalized and put into an explicit finite difference numerical form. The finite difference equations were obtained from truncated Taylor series expansions using a central differencing scheme. Nondimensional temperatures and streamlines were obtained for heat generation rates ranging from 20 to 1,500 W/m3 corresponding to a range of modified Rayleigh numbers of 324 to 24,340 and for several combinations of isothermally heated wall conditions for annuli of radius ratio of 2. It was found that multi-cellular flows occur at the highest Rayleigh numbers investigated. 相似文献
58.
Predicts the future of behavior therapy, focusing on theoretical development, therapeutic techniques, and empirical research. The importance of cognitive and affective processes in behavior change will attract increasing attention. Already one of the most widely adopted approaches, behavior therapy will be used to treat an expanded range of psychiatric disorders and health problems. Research will focus on comparative outcome studies and provide probes for investigating the nature of specific disorders and the mechanisms of therapeutic change. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
DE Stewart 《Canadian Metallurgical Quarterly》2003,191(9):561-562
60.
Quantitative RT-PCR for measuring gene expression 总被引:1,自引:0,他引:1