全文获取类型
收费全文 | 6946篇 |
免费 | 91篇 |
专业分类
电工技术 | 71篇 |
综合类 | 1篇 |
化学工业 | 660篇 |
金属工艺 | 83篇 |
机械仪表 | 91篇 |
建筑科学 | 167篇 |
矿业工程 | 17篇 |
能源动力 | 84篇 |
轻工业 | 470篇 |
水利工程 | 53篇 |
石油天然气 | 16篇 |
无线电 | 608篇 |
一般工业技术 | 750篇 |
冶金工业 | 3268篇 |
原子能技术 | 39篇 |
自动化技术 | 659篇 |
出版年
2021年 | 43篇 |
2020年 | 30篇 |
2019年 | 65篇 |
2018年 | 68篇 |
2017年 | 50篇 |
2016年 | 52篇 |
2015年 | 41篇 |
2014年 | 69篇 |
2013年 | 211篇 |
2012年 | 119篇 |
2011年 | 172篇 |
2010年 | 126篇 |
2009年 | 123篇 |
2008年 | 178篇 |
2007年 | 178篇 |
2006年 | 160篇 |
2005年 | 142篇 |
2004年 | 119篇 |
2003年 | 109篇 |
2002年 | 112篇 |
2001年 | 117篇 |
2000年 | 97篇 |
1999年 | 162篇 |
1998年 | 830篇 |
1997年 | 532篇 |
1996年 | 345篇 |
1995年 | 252篇 |
1994年 | 251篇 |
1993年 | 248篇 |
1992年 | 106篇 |
1991年 | 97篇 |
1990年 | 120篇 |
1989年 | 120篇 |
1988年 | 111篇 |
1987年 | 101篇 |
1986年 | 80篇 |
1985年 | 105篇 |
1984年 | 75篇 |
1983年 | 65篇 |
1982年 | 59篇 |
1981年 | 56篇 |
1980年 | 61篇 |
1979年 | 61篇 |
1978年 | 57篇 |
1977年 | 128篇 |
1976年 | 248篇 |
1975年 | 54篇 |
1974年 | 37篇 |
1973年 | 37篇 |
1972年 | 36篇 |
排序方式: 共有7037条查询结果,搜索用时 15 毫秒
1.
2.
Ricardo Cambraia Parreira Diana Paola Gmez‐Mendoza Itamar Couto Guedes de Jesus Rafael Pereira Lemos Anderson Kennedy Santos Cristiana Perdigo Rezende Henrique Csar Pereira Figueiredo Mauro Cunha Xavier Pinto Frank Kjeldsen Silvia Guatimosim Rodrigo Ribeiro Resende Thiago Verano‐Braga 《Proteomics. Clinical applications》2020,14(4)
3.
4.
HSDPA的度理论上最高达4.4M bit/s,但额的流量对无线接网络和空载传输容量要求有巨大影响。“3G的势头已经成为一个始终如一的主题。不过,正如我们所指出的,对3G手机的深刻领会并不总是伴随着对3G服务的持续理解。看上去高速下行包接入(HSDPA)技术可能是一个例外。它在欧洲发布,并且已经引起了人们浓厚的兴趣。看看它在亚洲的发展,我们不禁要问:它就是最终真正的3G吗?回首2002~2003年,HSDPA的部署看上去是一条漫长的道路,并且3GPP方面没有什么紧迫感,它的成员忙于应付WCDMA部署方面的复杂性。两件事的发生加速了HSDPA的部署:… 相似文献
5.
Antisense oligonucleotide inhibition of hepatitis C virus gene expression in transformed hepatocytes
R Hanecak V Brown-Driver MC Fox RF Azad S Furusako C Nozaki C Ford H Sasmor KP Anderson 《Canadian Metallurgical Quarterly》1996,70(8):5203-5212
Genetic and biochemical studies have provided convincing evidence that the 5' noncoding region (5' NCR) of hepatitis C virus (HCV) is highly conserved among viral isolates worldwide and that translation of HCV is directed by an internal ribosome entry site (IRES) located within the 5' NCR. We have investigated inhibition of HCV gene expression using antisense oligonucleotides complementary to the 5' NCR, translation initiation codon, and core protein coding sequences. Oligonucleotides were evaluated for activity after treatment of a human hepatocyte cell line expressing the HCV 5' NCR, core protein coding sequences, and the majority of the envelope gene (E1). More than 50 oligonucleotides were evaluated for inhibition of HCV RNA and protein expression. Two oligonucleotides, ISIS 6095, targeted to a stem-loop structure within the 5' NCR known to be important for IRES function, and ISIS 6547, targeted to sequences spanning the AUG used for initiation of HCV polyprotein translation, were found to be the most effective at inhibiting HCV gene expression. ISIS 6095 and 6547 caused concentration-dependent reductions in HCV RNA and protein levels, with 50% inhibitory concentrations of 0.1 to 0.2 microM. Reduction of RNA levels, and subsequently protein levels, by these phosphorothioate oligonucleotides was consistent with RNase H cleavage of RNA at the site of oligonucleotide hybridization. Chemically modified HCV antisense phosphodiester oligonucleotides were designed and evaluated for inhibition of core protein expression to identify oligonucleotides and HCV target sequences that do not require RNase H activity to inhibit expression. A uniformly modified 2'-methoxyethoxy phosphodiester antisense oligonucleotide complementary to the initiator AUG reduced HCV core protein levels as effectively as phosphorothioate oligonucleotide ISIS 6095 but without reducing HCV RNA levels. Results of our studies show that HCV gene expression is reduced by antisense oligonucleotides and demonstrate that it is feasible to design antisense oligonucleotide inhibitors of translation that do not require RNase H activation. The data demonstrate that chemically modified antisense oligonucleotides can be used as tools to identify important regulatory sequences and/or structures important for efficient translation of HCV. 相似文献
6.
GW Pratt 《Canadian Metallurgical Quarterly》1997,(23):30-32
A discussion is presented of contributing factors to the injury to the foreleg of the Thoroughbred racehorse. The critical part of the step is taken to be the first 10-20 ms after ground contact as the hoof slides forward and stops. Large nonaxial loads associated with the deceleration of the hoof are shown to arise. Results of accelerometer measurements on the hoof of a horse running at racing speed are presented as well as mechanical properties of the racing surface. The mechanical properties of the track surface, the type of shoe, and the degree of fatigue of the horse all work together to determine the level of risk. 相似文献
7.
8.
C Diamond ML Huang DH Kedes C Speck GW Rankin D Ganem RW Coombs TM Rose JN Krieger L Corey 《Canadian Metallurgical Quarterly》1997,176(3):775-777
The prevalence of human herpesvirus 8 (HHV-8)/Kaposi's sarcoma (KS)-associated herpesvirus was investigated in the semen of 99 human immunodeficiency virus (HIV)-infected men (median CD4 cell count, 357/mm3) by use of a polymerase chain reaction (PCR) assay capable of detecting <10 copies of HHV-8 DNA. Of the subjects, 95 (96%) self-identified as men who have sex with men (MSM), and 3 had a history of clinical KS. Seminal cell specimens were negative for HHV-8 in 98 subjects. None of the 26 without KS (27.1% of 96 tested) who were seropositive for HHV-8 by IFA for latency-associated nuclear antigens had HHV-8 detected in their semen. The only subject with any evidence for seminal HHV-8 DNA was seropositive for HHV-8 and had active KS. HHV-8 was detected in 10 (10.4%) of 96 peripheral blood mononuclear cell specimens. The prevalence of HHV-8 DNA by PCR in semen of HIV-infected MSM without KS is low. 相似文献
9.
10.
SC Langley GW Rickett A Hunt FJ Kelly AD Postle DA York 《Canadian Metallurgical Quarterly》1993,45(3):543-551
The biochemical maturation of the lung in late gestation and in the young animal is regulated by glucocorticoids. The present study was aimed at dissociating the different glucocorticoid receptor sites involved in these regulatory functions. The obese Zucker rat was selected as a model for this study as it exhibits hypersensitivity to glucocorticoid hormone action by virtue of its elevated receptor numbers and activity. Two synthetic steroid analogues were administered to obese animals; RU28362, a specific type II receptor agonist, and the type II antagonist RU486. RU28362 promoted a strong catabolic effect, which was associated with reduced food intake and the abolition of growth in the rats. The agonist, RU28362, attenuated developmental increases in antioxidant enzyme activities, and altered the growth of the tissue. At the age studied, development of the lung phosphatidylcholine (PC) system was almost complete, but RU28362 increased disaturated PC 16:0/16:0 concentrations by almost 2-fold, and altered the molecular composition of total pulmonary PC. RU486 attenuated the growth of the rats and reduced their food intake. Treatment with the type II antagonist attenuated lung growth and increased the activities of pulmonary copper zinc (Cu/Zn) and manganese (Mn) superoxide dismutases. RU486 had no effect on lung PC concentrations and molecular composition. The data suggest a role for type I glucocorticoid receptors in the regulation of the antioxidant enzyme system in the lung, as type II antagonism will channel endogenous glucocorticoid binding to the type I site. Type II receptor binding would appear to play a role in regulating the lung PC content. 相似文献