全文获取类型
收费全文 | 2010篇 |
免费 | 115篇 |
国内免费 | 21篇 |
专业分类
耳鼻咽喉 | 7篇 |
儿科学 | 76篇 |
妇产科学 | 16篇 |
基础医学 | 244篇 |
口腔科学 | 26篇 |
临床医学 | 211篇 |
内科学 | 426篇 |
皮肤病学 | 42篇 |
神经病学 | 200篇 |
特种医学 | 357篇 |
外科学 | 176篇 |
综合类 | 38篇 |
一般理论 | 1篇 |
预防医学 | 121篇 |
眼科学 | 21篇 |
药学 | 86篇 |
中国医学 | 2篇 |
肿瘤学 | 96篇 |
出版年
2022年 | 15篇 |
2021年 | 28篇 |
2020年 | 24篇 |
2019年 | 22篇 |
2018年 | 24篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 29篇 |
2014年 | 55篇 |
2013年 | 50篇 |
2012年 | 57篇 |
2011年 | 100篇 |
2010年 | 61篇 |
2009年 | 70篇 |
2008年 | 59篇 |
2007年 | 82篇 |
2006年 | 69篇 |
2005年 | 63篇 |
2004年 | 64篇 |
2003年 | 60篇 |
2002年 | 46篇 |
2001年 | 33篇 |
2000年 | 43篇 |
1999年 | 65篇 |
1998年 | 58篇 |
1997年 | 60篇 |
1996年 | 52篇 |
1995年 | 35篇 |
1994年 | 46篇 |
1993年 | 33篇 |
1992年 | 37篇 |
1991年 | 41篇 |
1990年 | 30篇 |
1989年 | 49篇 |
1988年 | 34篇 |
1987年 | 38篇 |
1986年 | 52篇 |
1985年 | 35篇 |
1984年 | 40篇 |
1983年 | 39篇 |
1982年 | 24篇 |
1981年 | 38篇 |
1980年 | 22篇 |
1979年 | 23篇 |
1978年 | 34篇 |
1977年 | 23篇 |
1976年 | 27篇 |
1975年 | 19篇 |
1974年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有2146条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Driven by widespread concern about transfusion-transmitted disease, intraoperative blood salvage (IBS) and other forms of autologous transfusion are playing an increasing role in medical practice. A quality assurance (QA) program is one of the most important elements of a successful IBS program. A large and successful QA program is described, the key elements of which are: 1) direction by a physician dedicated to the program; 2) use of full-time IBS personnel; 3) use of procedure and training manuals; 4) development of detailed patient identification procedures; 5) quality control of identification procedures, hematocrit, washing efficiency, and sterility; 6) use of extensive patient records; and 7) preventive maintenance procedures. In the past 6 years, 14,522 procedures have been performed and 38,899 salvaged units of blood collected without significant complications. Much of this success is attributed to the comprehensive QA program used during this time. 相似文献
5.
6.
7.
Cat flea, Ctenocephalides felis felis (Bouché), feces are an essential part of larval nutrition under natural conditions. The mass values of adult flea feces can be measured by dissolving samples of flea feces in Drabkin's reagent, filtering, centrifuging, and measuring absorbance spectrophotometrically at 540 nm. Either flea feces or air-dried host blood can be used to generate the standard curve used to convert absorbance (optical density) values into mass values. Debris collected from flea-infested house cats averaged 23.02 mg debris per cat per h with an average of 10.41 mg flea feces per cat per h. Flea feces deposited in the environment serve as potential larval food. Adult flea feces comprised an average of 44.28% of the debris deposited from infested domestic house cats in this study. 相似文献
8.
9.
Intestinal schistosomiasis japonica: CT-pathologic correlation 总被引:1,自引:0,他引:1
Lee RC; Chiang JH; Chou YH; Rubesin SE; Wu HP; Jeng WC; Hsu CC; Tiu CM; Chang T 《Radiology》1994,193(2):539
10.
Synthetic and computer-assisted analyses of the pharmacophore for the benzodiazepine receptor inverse agonist site 总被引:2,自引:0,他引:2
M S Allen Y C Tan M L Trudell K Narayanan L R Schindler M J Martin C Schultz T J Hagen K F Koehler P W Codding 《Journal of medicinal chemistry》1990,33(9):2343-2357
The structural requirements for ligand binding to the benzodiazepine receptor (BzR) inverse agonist site were probed through the synthesis and in vitro evaluation of 3-substituted beta-carbolines 6, 7, 11, 12, gamma-carboline 13, and diindoles 18-21, 23-25, 27, 28, and 34. On the basis of the apparent binding affinities of these and other analogues, a hydrogen bond acceptor site (A2) on the receptor is proposed to interact with the N(9) hydrogen atom of the beta-carbolines or the N(7) hydrogen nuclei of the diindoles. Likewise, a proposed hydrogen bond donating site (H1) interacts with the N(2) nitrogen atom of the beta-carbolines or the N(5) nitrogen atom of the diindoles. It appears that interaction with both sites is a prerequisite for high affinity since analogues which have either one or both of these positions blocked exhibit substantial reduction in affinity. Moreover, H1 appears to be capable of engaging in a three-centered hydrogen bond with appropriately functionalized ligands, which explains the increase in potency observed in the following series of 3-substituted beta-carbolines: the n-butyl (12, IC50 = 245 nM), n-propoxy (9, IC50 = 11 nM), and propyl ketone (11, IC50 = 2.8 nM) congeners. In addition to H1 and A2, there appears to be a relatively narrow hydrophobic pocket in the binding cleft that can accommodate substituents at the 3-position of the beta-carbolines which have chain lengths less than or equal to C5. There is a 1 order of magnitude decrease in affinity between n-propoxy analogue 9 (IC50 = 11 nM, chain length = 4) and n-butoxy derivative 7 (IC50 = 98 nM, chain length = 5). Furthermore, alpha- and gamma-branching [e.g. ethoxycarbonyl (2), IC50 = 5 nM and tert-butoxycarbonyl (31) IC50 = 10 nM] but not beta- and delta-branching [e.g. isopropoxy (6), IC50 = 500 nM and (neopentyloxy) carbonyl (48), IC50 = 750 nM] at position 3 are tolerated. Occupation of this hydrophobic pocket is clearly important for high affinity as evidenced by the relatively low affinity of 30, a beta-carboline which possesses a hydrogen atom at the 3-position. This same hydrophobic pocket is partially filled by the D and E rings of the diindoles, which accounts for the high affinity of several members of this series. An excluded volume analysis using selected 3-substituted beta-carbolines and ring-E substituted pyridodiindoles is consistent with the presence of this hydrophobic pocket (see Figure 1).(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献