全文获取类型
收费全文 | 36919篇 |
免费 | 1956篇 |
国内免费 | 30篇 |
专业分类
电工技术 | 247篇 |
综合类 | 17篇 |
化学工业 | 7216篇 |
金属工艺 | 674篇 |
机械仪表 | 732篇 |
建筑科学 | 970篇 |
矿业工程 | 74篇 |
能源动力 | 728篇 |
轻工业 | 5821篇 |
水利工程 | 319篇 |
石油天然气 | 127篇 |
武器工业 | 5篇 |
无线电 | 1297篇 |
一般工业技术 | 5838篇 |
冶金工业 | 9998篇 |
原子能技术 | 139篇 |
自动化技术 | 4703篇 |
出版年
2024年 | 76篇 |
2023年 | 300篇 |
2022年 | 410篇 |
2021年 | 843篇 |
2020年 | 703篇 |
2019年 | 818篇 |
2018年 | 1348篇 |
2017年 | 1316篇 |
2016年 | 1377篇 |
2015年 | 1058篇 |
2014年 | 1276篇 |
2013年 | 2681篇 |
2012年 | 2016篇 |
2011年 | 1925篇 |
2010年 | 1549篇 |
2009年 | 1411篇 |
2008年 | 1373篇 |
2007年 | 1249篇 |
2006年 | 878篇 |
2005年 | 768篇 |
2004年 | 703篇 |
2003年 | 632篇 |
2002年 | 613篇 |
2001年 | 467篇 |
2000年 | 426篇 |
1999年 | 547篇 |
1998年 | 3070篇 |
1997年 | 2022篇 |
1996年 | 1312篇 |
1995年 | 775篇 |
1994年 | 579篇 |
1993年 | 683篇 |
1992年 | 220篇 |
1991年 | 221篇 |
1990年 | 190篇 |
1989年 | 190篇 |
1988年 | 180篇 |
1987年 | 153篇 |
1986年 | 132篇 |
1985年 | 156篇 |
1984年 | 130篇 |
1983年 | 103篇 |
1982年 | 144篇 |
1981年 | 163篇 |
1980年 | 168篇 |
1979年 | 80篇 |
1978年 | 86篇 |
1977年 | 316篇 |
1976年 | 701篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Rolandic discharge (RD), noted in the electroencephalography (EEG) of patients with benign epilepsy in childhood with centrotemporal spikes (BECCT) has several unique features. One feature is that the amount or frequency of RDs does not correlate well with the incidence of seizures in BECCT although it is a key finding in the diagnosis of this epileptic syndrome. In this study, we examined the efficacy of antiepileptic drugs focusing on the disappearance of RDs in relationship with seizure control. Forty patients with BECCT who were not medically treated prior to this study were randomly sorted into three groups. Twenty patients were assigned for clonazepam (CZP) treatment, 10 patients for valproate (VPA) and the remaining 10 patients for carbamazepine (CBZ). Each drug was administered for 4 consecutive weeks. EEGs were recorded twice during the study, before and 4 weeks after the medication trial. The effects of each treatment on RDs were assessed. RDs disappeared in 15 of the 20 cases treated with CZP (75%) within 4 weeks while the same was observed in only one of the 10 cases treated with VPA (10%). CBZ failed to demonstrate any effect on RD. In the group treated with CZP, there were no differences in seizure incidence, seizure type and blood concentration of CZP between the patients whose RDs disappeared and those whose RDs remained. 相似文献
32.
MF Fey 《Canadian Metallurgical Quarterly》1997,28(1-2):11-22
Microsatellites are unique highly polymorphic and informative genetic markers dispersed in the human genome. Their detection by PCR is rapid and a wide variety of DNA sources including archival material are available for diagnostic purposes. Microsatellite typing of haematological neoplasms may be applied to the search for loss of heterozygosity at loci possibly harbouring tumour suppressor genes, for example in acute lymphoblastic leukaemia. The technique may detect submicroscopical chromosomal deletions which are not visible in the leukaemic karyotype. RER+ tumours exhibiting microsatellite instability appear to be rare among haematological cancers with the possible exception of lymphoid tumours in immunosuppressed patients and lymphomas derived from mucosa-associated lymphoid tissue. An X-chromosomal microsatellite near the human androgen receptor gene (HUMARA) may be used for clonal X-inactivation analysis. Microsatellites therefore represent a collection of powerful genetic markers suitable to tackle questions relevant to basic research and clinical problems in leukaemia and lymphoma. 相似文献
33.
34.
BM Chen LY Chan SM Wang MF Wu JW Chern SR Roffler 《Canadian Metallurgical Quarterly》1997,73(3):392-402
We examined the in vivo efficacy of targeting beta-glucuronidase (betaG) to activate a glucuronide prodrug (BHAMG) of p-hydroxyaniline mustard (pHAM) at hepatoma ascites in Sprague-Dawley rats. Injection i.p. of 500 microg RH1-betaG, a conjugate formed between recombinant betaG and monoclonal antibody RH1 with specificity for an antigen expressed on AS-30D rat hepatoma cells, into rats bearing AS-30D ascites resulted in the accumulation of 54 microg conjugate per 10(9) tumor cells after 2 hr. Ascites fluid and serum contained 0.53 and 0 microg/ml, respectively, RH1-betaG 2 hr after injection of the conjugate. Conjugate binding to AS-30D cells was heterogeneous and non-saturated, as determined by flow cytometry. BHAMG was less toxic than pHAM to SD rats based on measures of animal mortality, weight loss and hematological toxicity. Treatment of rats bearing established hepatoma ascites with 500 microg RH1-betaG followed 2 hr later with a single i.p. injection of 30 mg/kg BHAMG or 3 i.p. injections of 10 mg/kg BHAMG 2, 3 and 4 hr later resulted in the cure of 6/8 and 8/8 animals, respectively. Treatment with BHAMG or pHAM alone did not produce cures, whereas treatment with a control antibody-betaG conjugate and BHAMG produced significantly greater hematological toxicity compared to treatment with RH1-betaG and BHAMG. All cured rats were completely protected from rechallenge with 2 x 10(7) AS-30D cells, indicating that successful treatment of animals induced protective immunity. 相似文献
35.
36.
R Herruzo-Cabrera L Malo-González ME Calle Purón MJ Vizcaíno-Alcaide J Del Rey-Calero 《Canadian Metallurgical Quarterly》1993,9(4):442-446
A cross-sectional study was performed to obtain risk factors for hepatitis B disease, HBsAg carriers and immunised personnel, among 2470 workers in a general hospital in Madrid, Spain. The data obtained were analyzed with multiple logistic regression to obtain beta coefficients for variables. The results of the analysis show that being a nurse or being regularly exposed to blood are the most important risk factors for hepatitis B acquisition. The length of time working at the same job activity was also a risk factor. The resulting beta coefficients allow the construction for a hepatitis non-immunised, HBsAg carrier and immunised HBV status, which can select subjects for a hepatitis B vaccination program. 相似文献
37.
Generation of Technology-Independent Retargetable Analog Blocks 总被引:1,自引:0,他引:1
R. Castro-López F. V. Fernández F. Medeiro A. Rodríguez-Vázquez 《Analog Integrated Circuits and Signal Processing》2002,33(2):157-170
This paper introduces a complete methodology for retargeting of analog cells to different sets of specifications. This methodology is technology-independent, thus allowing the migration, from one technology to another, of the circuit under retargeting. Careful integration of the device sizing and layout generation tasks via the incorporation of layout constraints during the sizing process allows to generate fully functional designs in a few minutes. The methodology is illustrated via the retargeting of a fully-differential Miller-compensated two-stage operational amplifier for a new set of specifications and two different technological processes.An erratum to this article can be found at 相似文献
38.
39.
We determine the exact power of two-prover interactive proof systems introduced by Ben-Or, Goldwasser, Kilian, and Wigderson (1988). In this system, two all-powerful noncommunicating provers convince a randomizing polynomial time verifier in polynomial time that the inputx belongs to the languageL. We show that the class of languages having tow-prover interactive proof systems is nondeterministic exponential time.We also show that to prove membership in languages inEXP, the honest provers need the power ofEXP only.The first part of the proof of the main result extends recent techniques of polynomial extrapolation used in the single prover case by Lund, Fortnow, Karloff, Nisan, and Shamir.The second part is averification scheme for multilinearity of a function in several variables held by an oracle and can be viewed as an independent result onprogram verification. Its proof rests on combinatorial techniques employing a simple isoperimetric inequality for certain graphs: 相似文献
40.