全文获取类型
收费全文 | 3808篇 |
免费 | 10篇 |
专业分类
电工技术 | 10篇 |
综合类 | 1篇 |
化学工业 | 82篇 |
金属工艺 | 17篇 |
机械仪表 | 11篇 |
建筑科学 | 46篇 |
矿业工程 | 11篇 |
能源动力 | 21篇 |
轻工业 | 39篇 |
水利工程 | 9篇 |
石油天然气 | 3篇 |
无线电 | 124篇 |
一般工业技术 | 96篇 |
冶金工业 | 3279篇 |
原子能技术 | 1篇 |
自动化技术 | 68篇 |
出版年
2023年 | 4篇 |
2021年 | 10篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2015年 | 10篇 |
2014年 | 5篇 |
2013年 | 30篇 |
2012年 | 21篇 |
2011年 | 29篇 |
2010年 | 25篇 |
2009年 | 17篇 |
2008年 | 19篇 |
2007年 | 20篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 12篇 |
2003年 | 18篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 121篇 |
1998年 | 1019篇 |
1997年 | 598篇 |
1996年 | 364篇 |
1995年 | 226篇 |
1994年 | 179篇 |
1993年 | 194篇 |
1992年 | 30篇 |
1991年 | 55篇 |
1990年 | 41篇 |
1989年 | 55篇 |
1988年 | 72篇 |
1987年 | 58篇 |
1986年 | 37篇 |
1985年 | 37篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 23篇 |
1980年 | 38篇 |
1979年 | 10篇 |
1978年 | 18篇 |
1977年 | 82篇 |
1976年 | 170篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1970年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有3818条查询结果,搜索用时 15 毫秒
41.
42.
OBJECTIVE: To determine the relative influences of induction of withdrawal bleedings secretory transformation, and reduction of mitosis in glands on prevention of endometrial hyperplasia during long-term hormonal replacement therapy. DESIGN: Observational expanded clinical case report. SETTING: Reproductive Endocrine Department of Hospital Necker, Paris, France, and Pathology Department of Women's Hospital, Los Angeles County and University of Southern California Medical Center, Los Angeles, California. PATIENTS: Postmenopausal women seeking treatment for symptomatic menopause. INTERVENTIONS: Endometrial biopsy and/or ambulatory hysteroscopy. MAIN OUTCOME MEASURE: Endometrial histology including progestational maturation patterns and glandular epithelial mitosis rates. Macroscopic endometrial appearance. RESULTS: The use of larger doses of E2 and P induced more marked secretory changes and more frequent withdrawal bleeding than the lower doses. There was no evidence of endometrial hyperplasia after 5 years of E2/P replacement therapy independently of bleeding pattern or progestational maturation. Consistent reduction of mitosis rates in glandular epithelium was found after 9 or more days of P administration in each cycle. CONCLUSIONS: Control of endometrial growth is mainly related to control of mitosis in glands by a relatively low doses of P. Induction of withdrawal bleeding and endometrial secretory transformation, which require larger doses of Progesterone, do not provide additional benefit for prevention of hyperplasia. Induction of amenorrhea with a relatively low dose of P may be offered to women seeking hormone replacement therapy with similar levels of safety. 相似文献
43.
JF Cáceres T Misteli GR Screaton DL Spector AR Krainer 《Canadian Metallurgical Quarterly》1997,138(2):225-238
SR proteins are required for constitutive pre-mRNA splicing and also regulate alternative splice site selection in a concentration-dependent manner. They have a modular structure that consists of one or two RNA-recognition motifs (RRMs) and a COOH-terminal arginine/serine-rich domain (RS domain). We have analyzed the role of the individual domains of these closely related proteins in cellular distribution, subnuclear localization, and regulation of alternative splicing in vivo. We observed striking differences in the localization signals present in several human SR proteins. In contrast to earlier studies of RS domains in the Drosophila suppressor-of-white-apricot (SWAP) and Transformer (Tra) alternative splicing factors, we found that the RS domain of SF2/ASF is neither necessary nor sufficient for targeting to the nuclear speckles. Although this RS domain is a nuclear localization signal, subnuclear targeting to the speckles requires at least two of the three constituent domains of SF2/ASF, which contain additive and redundant signals. In contrast, in two SR proteins that have a single RRM (SC35 and SRp20), the RS domain is both necessary and sufficient as a targeting signal to the speckles. We also show that RRM2 of SF2/ASF plays an important role in alternative splicing specificity: deletion of this domain results in a protein that, although active in alternative splicing, has altered specificity in 5' splice site selection. These results demonstrate the modularity of SR proteins and the importance of individual domains for their cellular localization and alternative splicing function in vivo. 相似文献
44.
45.
We found that the total watery extracts obtained from roots of various plants such as Symphytum officinale, Phytolacca americana etc, precipitate human glycoproteins, agglutinate sheep red blood cells (SRBC) and stimulate lymphocyte adherence to nylon fibers. Five out of seven extracts precipitated human gammaglobulins and one of seven obviously agglutinate SRBC. If these cells were pretreated with rabbit antibodies against SRBC, all extracts agglutinated the cells at various degrees of intensity, the most active being Phytolacca americana. The adherence of mouse but not human lymphocytes to nylon fibers was stimulated by extracts of Symphytum officinale and Phytolacca americana. This process was neither stimulated nor inhibited by Mannose (Man), Galactose (Gal), Glucose (Glc), N-acethyl Galactose (GalNAc) and N-acethyl Glucose (Glc-NAc). These biological effects of the plant extracts could be the expression of a lectin-like ability to bind various sugars other than those mentioned. The results suggest the possibility of using different extracts as means to point out the presence in serum or at the cellular level of some carbohydrates influencing the cellular adhesion, phenomenon which plays an important role in the functions of hematopoietic cells. 相似文献
46.
47.
GV Naccarelli DL Wolbrette JT Dell'Orfano HM Patel JC Luck 《Canadian Metallurgical Quarterly》1998,9(8):864-891
Multiple trials using antiarrhythmic drugs, pharmacologic therapy, and implantable cardioverter defibrillators have been performed in an attempt to improve survival in patients: (1) postmyocardial infarction; (2) with congestive heart failure, with and without nonsustained ventricular tachycardia; and (3) with sustained ventricular tachycardia and those who have survived an out-of-hospital cardiac arrest. This article reviews some of the key findings and limitations of completed and ongoing trials. We also make recommendations for the current treatment of such patients based on the results of these trials. 相似文献
48.
49.
50.
RD Lane DM Allan CA Bennett-Clarke DL Howell RW Rhoades 《Canadian Metallurgical Quarterly》1997,14(2):277-286
Immunocytochemistry and retrograde labeling were used to define the thalamic projections of calbindin- and parvalbumin-containing cells in superficial layers of the rat's superior colliculus (SC). Quantitative analysis revealed that 90.8 +/- 2.2% (mean +/- standard deviation) of the calbindin-immunoreactive neurons in the stratum griseum superficiale (SGS) projected to the dorsal lateral geniculate nucleus (LGNd) and that 91.3 +/- 4.3% of calbindin-immunoreactive neurons in the stratum opticum (SO) projected to the lateral posterior nucleus (LP). In contrast, only 17.3 +/- 2.5% of parvalbumin-immunoreactive neurons in the SGS were found to project to the LGNd and 16.5 +/- 3.1% of the parvalbumin-immunoreactive SO cells were retrogradely labeled after LP injections. Few of the parvalbumin-immunoreactive neurons in either the SGS (7.2 +/- 2.5%) or the SO (9.2 +/- 2.5%) were GABA positive. The retrograde-labeling results suggest that parvalbumin-immunoreactive neurons in the rat's SO and SGS may either be primarily interneurons or have descending projections, while calbindin-containing cells are primarily thalamic projection neurons. These results are consistent with data from other rodents, but almost exactly the opposite of data that have been reported for the cat for these same populations of SC projection neurons. Such interspecies differences raise questions regarding the functional importance of expressing one calcium-binding protein versus another in a specific neuronal population. 相似文献