全文获取类型
收费全文 | 438073篇 |
免费 | 29864篇 |
国内免费 | 10442篇 |
专业分类
耳鼻咽喉 | 4356篇 |
儿科学 | 11723篇 |
妇产科学 | 7823篇 |
基础医学 | 36636篇 |
口腔科学 | 9131篇 |
临床医学 | 50607篇 |
内科学 | 56262篇 |
皮肤病学 | 5270篇 |
神经病学 | 23791篇 |
特种医学 | 11291篇 |
外国民族医学 | 37篇 |
外科学 | 43050篇 |
综合类 | 69323篇 |
现状与发展 | 19篇 |
一般理论 | 33篇 |
预防医学 | 42260篇 |
眼科学 | 6378篇 |
药学 | 43407篇 |
509篇 | |
中国医学 | 40389篇 |
肿瘤学 | 16084篇 |
出版年
2023年 | 6544篇 |
2022年 | 10168篇 |
2021年 | 16740篇 |
2020年 | 15577篇 |
2019年 | 20917篇 |
2018年 | 18554篇 |
2017年 | 15852篇 |
2016年 | 13484篇 |
2015年 | 12711篇 |
2014年 | 25740篇 |
2013年 | 27773篇 |
2012年 | 23603篇 |
2011年 | 26060篇 |
2010年 | 21255篇 |
2009年 | 18843篇 |
2008年 | 18478篇 |
2007年 | 19302篇 |
2006年 | 17080篇 |
2005年 | 14896篇 |
2004年 | 12358篇 |
2003年 | 10928篇 |
2002年 | 8832篇 |
2001年 | 7954篇 |
2000年 | 6610篇 |
1999年 | 5676篇 |
1998年 | 4776篇 |
1997年 | 4755篇 |
1996年 | 4028篇 |
1995年 | 3922篇 |
1994年 | 3766篇 |
1993年 | 2998篇 |
1992年 | 3020篇 |
1991年 | 2613篇 |
1990年 | 2307篇 |
1989年 | 2056篇 |
1988年 | 1981篇 |
1987年 | 1690篇 |
1986年 | 1547篇 |
1985年 | 4643篇 |
1984年 | 5516篇 |
1983年 | 3851篇 |
1982年 | 4439篇 |
1981年 | 4032篇 |
1980年 | 3579篇 |
1979年 | 3238篇 |
1978年 | 2807篇 |
1977年 | 2157篇 |
1976年 | 2362篇 |
1975年 | 1760篇 |
1974年 | 1523篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
伊克昭盟甘草群落调查报告 总被引:2,自引:0,他引:2
通过样地调查和采挖试验,内蒙古伊克昭盟的甘草群落可划分为12个类型,并对各类群落的利用作出评估。 相似文献
992.
C. L. R. BARRATT P. E. HARRISON A. ROBINSON I. D. COOKE 《International journal of andrology》1990,13(1):50-58
The significance of white blood cells in the ejaculate remains a matter of controversy. Several authors have suggested that such cells are important in the modulation of an antisperm antibody response, i.e. a predominance of suppressor/cytotoxic to helper/inducer T cells may prevent the development of antisperm antibodies. In order to examine this relationship further we have documented the white blood cell types, with emphasis on the T-lymphocyte populations, in the ejaculates of men from infertile couples with and without antisperm antibodies; the latter group was divided further into two groups--vasovasostomized men and idiopathic men. All seven of the men without antisperm antibodies had a predominance of suppressor/cytotoxic T cells to helper/inducer T cells in the ejaculate. However, only in some of the men with antibodies was there a predominance of T-helper/inducer cells. It is clear that the relationship between antisperm antibodies and seminal leucocytes is therefore not as straightforward as has been proposed. 相似文献
993.
本文研究眼镜蛇入蛰前、蛰眠期及出蛰后血清 T_3,T_4和皮质醇水平与体内能量物质的含量变化关系,探讨其与蛰眠行为的关系。结果表明入蛰前眼镜蛇大量摄食储能过冬,由于血清激素水平降低,控制了体内组织器官的氧化代谢系统,使新陈代谢逐渐下降。蛰眠期血糖血脂明显下降,耗氧量显著减少,呈节能低代谢状态。此期血清激素水平已升高,但低温抑制了体内代谢。出蛰后血清激素水平明显升高且在春暖升温季节使眼镜蛇代谢率升高。 相似文献
994.
Summary With the use of duplex Doppler ultrasound and color Doppler flow imaging(CDFI), the characteristics of blood supply in neoplasma
were studied in 51 cases of 60 liver tumors, and compared with the results of surgery, pathological examination and hepatic
anerial angiography. The result showed that: 1. Doppler blood flow signals could be detected in all hepatic carcinomas, and
in 10 cases of 18 hemangiomas, significant difference was observed (P<0.001); 2. Doppler blood flow spectra showed pulsatile pattern in 41 of 42 hepatic carcinomas, and in 6 of 10 hemangiomas
(P<0.01); and 3. the peak flow velocity was obviously lower in hemangioma group than in hepatic carcinoma group (20.34±23.93
vs 64.74±30.18 cm,P<0.001). The characteristics of CDFI show that hemangiomas and hepatocellular carcinomas are different. It can, therefore,
be concluded that the blood supply of hepatic carcinomas mainly comes from hepatic arterial system, and is of value in duplex
Doppler ultrasound and CDFI. 相似文献
995.
In rabbit platelet rich plasma (PRP), 5-hydroxytraptamine (5-HT,0.03~3μmol/L) induced decrease in light transmission (DLT) dose-de pendently with centralization, as revealed by electron microscopy. However, 5-HT did not induced platelet aggregation and release reaction. 5-HT-induced DLT was inhibited by methysergide (0.3~30μmol/L), indomethacin (0.3~10μmol/L) and PGE_1 (0.01~0.3μmol/L) in a dose-dependent manner, but not EGTA(0.3~3mmol/L). Collagen(Coll), arachidonic acid (AA), adenosine diphosphate (ADP) and a stable thromboxane A2 analoge(STA_2) also induced DLT before aggregation by themselves, which was also inhibited by PGE_1, but not inhibited by EGTA except for Coll However,Coll-, AA-, STA_2-and ADP-induced DLT were reduced by pretreatment of PRP with 5-HT dose-depen-dently. The duration of DLT by Coll and AA were decreased from 151.4±5.93 sec and 15(?)38±0.60sec to 45.44±4.04 sec and 9.00±1.25 sec respectively ((?)±s(?) P<0.01), but not by ADP and STA_2, 3μmol/L of ADP-and 0.3μmol/L of STA_2-induced aggregation which was not accompanied with release reaction were enhanced by 5-HT pretreatment, but in those (Coil 5μg/ml, AA 100~200μmol/L and STA_2 1~3 μmol/L) with release reaction, the amount of adenosine triphosphate(ATP)were suppressed significantly (P<0.001) by 5-HT pretreatment without the effect on the magnitude of aggregation, The mobilization of cytosolic free calcium concentration ([Ca~(2+)]i) was observed after 5-HT treatment in single washed platelet, the results indicated that the basic level of [Ca~(2+)] i was 64.78±3.24nmol/L and this level was increased dose-dependently and significantly at 30 sec after administration of 5-HT and the time of peak value of [Ca~(2+)] i was at 90~100 sec.The similar time courses of suppression of ATP released during aggregation, in cases of Coll(5μg/ml), AA (200μmol/L) and STA_2(3μmol/L), by 5-HT were also found in the present experiment. 相似文献
996.
MICHAL J. KANTOCH ROXANE McKAY MICHAEL J. TYRRELL 《Pacing and clinical electrophysiology : PACE》1993,16(9):1887-1891
An 11-year-old girl who underwent Mustard's operation for complete transposition of the great arteries in infancy, developed Mobitz type II second-degree AV block 81/2 years later. A transvenous, active fixation left ventricular lead was inserted and connected to a rate responsive pacemaker. Two years later the lead dislodged due to the child's growth. A new active fixation electrode was positioned in the left ventricle below the pulmonary valve, leaving an electrode loop in the ventricle. Such an approach may prevent lead dislodgement due to growth after intraatrial repair for transposition of the great arteries, but regular radiological or echocardiographic follow-up of lead position is recommended in these patients. 相似文献
997.
针药并用治疗男性不育297例疗效分析 总被引:2,自引:0,他引:2
本文采用针刺加鹿茸精注射液穴位注射及中药治疗男性不育297例,痊愈142例,占47.8%,显效81例,占27.3%,有效53例,占17.8%,无效21例,占7.1%,三者联合运用效果较满意。 相似文献
998.
本文参考X-衍射数据,采用MNDO程序计算了不同构型、构象PAM类的生成热,结合核磁共振数据讨论了PAM类构象等问题.结果表明,PAM类在水溶液中:顺式体肟基可以自由旋转,任何一种构象都可能成为药效构象;反式体肟基本不可能存在稳定的平面构象,其药效构象只能是优势构象.用MNDO程序中反应途径的计算法,还计算了顺、反式肟基构型相互转变的势垒,为探讨PAM类重活化机理提供了一定的参考. 相似文献
999.
本文根据Svennerholm和蒋谷人等的方法略加改良,测定了蚌埠地区113例正常人,71例恶性肿瘤患者和82例非肿瘤疾病患者血清脂质结合唾液酸(LSA)的含量。正常值为12.4mg/dl(SD=±3.6mg/dl),71例不同肿瘤患者的平均值为28.2mg/dl(SD=±9.7mg/dl),阳性率为88.7%,82例非肿瘤疾病患者的平均值为16.82mg/dl(SD=±5.4mg/dl),假阳性率为17%。方法的灵敏度,重复性(平均CV=3.6%)和回收率(平均回收率=101.4%)测定结果是满意的。本研究的初步结果表明,血清LSA测定对肺癌、白血病、胃癌和食管癌具有一定的临床诊断价值。 相似文献
1000.
R. F. WEST 《Medical education》1988,22(2):104-112
The purpose of this study was to assess the degree of consistency in student ratings of teacher effectiveness during the first year of medical school. Student ratings of teaching effectiveness represent a commonly used source of information that enters into the academic decision-making process. In medical school, student evaluations often represent a major source of information that is used in promotion and tenure decisions. It is essential that the precision of such ratings be ascertained so that decision-makers will know how much confidence to place in this source of information on teaching effectiveness. In this study, each member of a first-year medical school class was randomly assigned a two-digit identification number at the beginning of the spring semester, 1986. As the semester progressed students were asked to evaluate each full-time teacher in three major courses. Multiple instructors were utilized in each course (n = 10). Each teacher was evaluated immediately after lectures during the first (T1) and second (T2) halves of the course. Students evaluated the teacher a third time (T3) as part of the end-of-semester overall course evaluation. The teachers were evaluated on a short eight-item Likert-type scale that identified several key indicators of effective teaching. Students attached their anonymous identification numbers to individual ratings so that their responses could be matched in the analysis. The results indicate that medical students are only moderately consistent in the extent to which they evaluate teachers. This inconsistency varied by course and by instructors within courses.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献