全文获取类型
收费全文 | 4730篇 |
免费 | 51篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 83篇 |
综合类 | 1篇 |
化学工业 | 403篇 |
金属工艺 | 20篇 |
机械仪表 | 37篇 |
建筑科学 | 45篇 |
矿业工程 | 2篇 |
能源动力 | 25篇 |
轻工业 | 107篇 |
水利工程 | 9篇 |
石油天然气 | 5篇 |
无线电 | 326篇 |
一般工业技术 | 389篇 |
冶金工业 | 2746篇 |
原子能技术 | 29篇 |
自动化技术 | 555篇 |
出版年
2021年 | 26篇 |
2020年 | 17篇 |
2019年 | 27篇 |
2018年 | 26篇 |
2017年 | 30篇 |
2016年 | 17篇 |
2015年 | 26篇 |
2014年 | 22篇 |
2013年 | 133篇 |
2012年 | 63篇 |
2011年 | 78篇 |
2010年 | 87篇 |
2009年 | 85篇 |
2008年 | 93篇 |
2007年 | 71篇 |
2006年 | 80篇 |
2005年 | 67篇 |
2004年 | 48篇 |
2003年 | 74篇 |
2002年 | 76篇 |
2001年 | 67篇 |
2000年 | 55篇 |
1999年 | 129篇 |
1998年 | 684篇 |
1997年 | 435篇 |
1996年 | 299篇 |
1995年 | 208篇 |
1994年 | 182篇 |
1993年 | 204篇 |
1992年 | 73篇 |
1991年 | 61篇 |
1990年 | 82篇 |
1989年 | 74篇 |
1988年 | 72篇 |
1987年 | 54篇 |
1986年 | 70篇 |
1985年 | 73篇 |
1984年 | 40篇 |
1983年 | 52篇 |
1982年 | 48篇 |
1981年 | 54篇 |
1980年 | 43篇 |
1979年 | 27篇 |
1978年 | 43篇 |
1977年 | 100篇 |
1976年 | 179篇 |
1975年 | 24篇 |
1974年 | 31篇 |
1972年 | 20篇 |
1970年 | 17篇 |
排序方式: 共有4782条查询结果,搜索用时 0 毫秒
1.
2.
F. Cioffi E. M. Cohen Richard Badick 《Drug development and industrial pharmacy》1993,19(14):1741-1746
Carstensen and Rhodes1 have suggested that when, in stability programs, assays cannot be performed immediately after the protocol-designated storage time, then freezing them until such a time when assays can be performed would be a reasonable manner to retain the protocol schedule. They caution, however, that such a procedure may not be valid for dissolution data. The article to follow deals with real-time data showing that such a process is feasible for Nalidixic Acid tablets (and presumably for other tablets as well), and that, furthermore, the dissolution pattern would seem to be “frozen” as well. 相似文献
3.
4.
A Voskova-Goldman A Peier CT Caskey CS Richards LG Shaffer 《Canadian Metallurgical Quarterly》1997,48(6):1633-1638
The challenge of Duchenne muscular dystrophy (DMD) carrier identification resides in the ability to identify the presence of a mutant gene over the background contributed by the normal allele. Current diagnosis of carrier status when a deletion has been identified in a proband is based on an analysis of a gene dosage. We present a diagnostic strategy that uses fluorescence in situ hybridization (FISH) to detect female carriers with major deletions in the dystrophin gene. We screened a human X-chromosome-derived genomic library with a full-length dystrophin cDNA and isolated 15 dystrophin-specific cosmids that contain DMD gene exons. Six cosmids were further tested as FISH probes in control individuals and subsequently applied on chromosomes from eight males with DMD and known deletions and on samples from three female carriers. As expected, X chromosomes in normal females displayed four signals, two for the DMD-specific probe and two for the X-chromosome centromeric probe. Hybridization on chromosomal spreads from carriers of deletions revealed only one signal from the DMD-specific probe and two from the control centromeric probe. Males carrying deletions showed no DMD-specific signal for the deleted exons tested. Our data indicate that FISH could represent an alternative method for the detection of female carriers with DMD gene deletions. 相似文献
5.
6.
This paper describes a fully integrated digital-spread spectrum transceiver chip fabricated through MOSIS in 1.2 μm CMOS. It includes a baseband spread spectrum transmitter and a coherent intermediate frequency (IF) receiver consisting of a Costas loop, an acquisition loop for the pseudo-noise (PN) sequence, and a clock recovery loop with a 406.4 MHz onchip numerically controlled oscillator (NCO). The transceiver is capable of operating at a maximum IF sampling rate of 50.8 MS/s and a maximum chip rate of 12.7 R Mchips/s (Mcps) with selectable data rates of 100, 200, 400, and 800 kbps. At the maximum operating speed of 50.8 R MS/s, it dissipates 1.1 W. In an additive white Gaussian noise channel the IF receiver achieves a receiver output SNR within 1 dB of theory and can acquire code with a wide range of input SNR from -17 dB to over 30 dB. The transceiver chip has been interfaced to an RF up/down converter to demonstrate a wireless voice/data/video link operating in the 902-928 MHz band 相似文献
7.
LG Westergaard PE Rasmussen S Maigaard HJ Ingerslev AN Andersen JF Larsen J Starup PJ Hornnes CY Andersen 《Canadian Metallurgical Quarterly》1993,155(33):2511-2514
Medical indications for in vitro fertilization and embryo transfer (IVF-ET) internationally and in Denmark are reviewed. Reports from large international centres document that tubal infertility, unexplained infertility, endometriosis and male infertility are equally good indications for IVF. Traditionally, tubal infertility has been the only medical indication qualifying for IVF treatment within the National Health Service in Denmark. Thus, in this country, couples with unexplained and male infertility and with endometriosis have to pay up to 25,000 D.Kr. per IVF-ET treatment in private fertility clinics. Since there is no scientific basis for this discrimination, it is urged that the present rules are changed, so that couples with unexplained and male infertility and endometriosis are also allowed IVF treatment free of charge in the public fertility clinics. 相似文献
8.
MD Cohen ST Auringer JL Grosfeld CA Galliani NA Heerema 《Canadian Metallurgical Quarterly》1993,23(6):463-466
The purpose of this study is to present three patients with multifocal primary neuroblastoma, to review the literature, and describe the radiographic findings. SUBJECTS AND METHODS: Three children with multifocal neuroblastoma have been identified. The case histories and imaging findings in these patients are reviewed. RESULTS: Two children had synchronous and one child had metachronous multifocal primary neuroblastoma. The primary tumors were both in the abdomen in one patient, both in the chest in another patient, and in the chest and abdomen in the third patient. Evidence for multifocal origin of these tumors, rather than metastatic spread, is presented. CONCLUSION: Multifocal primary neuroblastomas can occur. The tumors maybe synchronous or metachronous. Awareness of this disorder may prevent errors in diagnosis and staging. Although not identified in our patients there is a strong familial incidence of neuroblastomas in those patients with multifocal tumors. 相似文献
9.
A predictive analogy of turbulent mass transfer across wavy, sheared air-water interface, in deep water bodies is proposed. The theory is based on the formulation of a theoretical eddy diffusivity profile in the surface region, and it applies to the non-breaking wave regime. The predictions for a water-side friction velocity range of 0.5–6 cm/s are in excellent agreement with laboratory data from wind-wave facilities with an average error of 15.4%. 相似文献
10.