全文获取类型
收费全文 | 18608篇 |
免费 | 1324篇 |
国内免费 | 58篇 |
专业分类
耳鼻咽喉 | 197篇 |
儿科学 | 477篇 |
妇产科学 | 457篇 |
基础医学 | 2437篇 |
口腔科学 | 426篇 |
临床医学 | 1946篇 |
内科学 | 3723篇 |
皮肤病学 | 201篇 |
神经病学 | 2096篇 |
特种医学 | 624篇 |
外国民族医学 | 5篇 |
外科学 | 3094篇 |
综合类 | 218篇 |
一般理论 | 16篇 |
预防医学 | 1478篇 |
眼科学 | 427篇 |
药学 | 993篇 |
1篇 | |
中国医学 | 39篇 |
肿瘤学 | 1135篇 |
出版年
2022年 | 160篇 |
2021年 | 329篇 |
2020年 | 204篇 |
2019年 | 315篇 |
2018年 | 401篇 |
2017年 | 321篇 |
2016年 | 343篇 |
2015年 | 341篇 |
2014年 | 488篇 |
2013年 | 780篇 |
2012年 | 1033篇 |
2011年 | 1163篇 |
2010年 | 749篇 |
2009年 | 631篇 |
2008年 | 1021篇 |
2007年 | 1162篇 |
2006年 | 1115篇 |
2005年 | 1078篇 |
2004年 | 1113篇 |
2003年 | 1020篇 |
2002年 | 995篇 |
2001年 | 235篇 |
2000年 | 182篇 |
1999年 | 232篇 |
1998年 | 191篇 |
1997年 | 188篇 |
1996年 | 156篇 |
1995年 | 157篇 |
1994年 | 127篇 |
1993年 | 116篇 |
1992年 | 161篇 |
1991年 | 161篇 |
1990年 | 137篇 |
1989年 | 129篇 |
1988年 | 112篇 |
1987年 | 129篇 |
1986年 | 121篇 |
1985年 | 135篇 |
1984年 | 149篇 |
1983年 | 132篇 |
1982年 | 143篇 |
1981年 | 133篇 |
1980年 | 138篇 |
1979年 | 109篇 |
1978年 | 98篇 |
1977年 | 90篇 |
1976年 | 104篇 |
1975年 | 81篇 |
1974年 | 84篇 |
1973年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
61.
Primm BJ Perez L Dennis GC Benjamin L Clark W Keough K Leak WD Payne R Smith D Sullivan LW;National Medical Association 《Journal of the National Medical Association》2004,96(9):1152-1161
ISSUE: Inadequate pain management is a serious public health problem that affects a wide cross-section of Americans. Patients are often denied sufficient medication, because physicians lack training and fear scrutiny from federal and state regulatory agencies. In addition, even the state-financed system of care, Medicaid, has been increasingly denying payment for the best treatment for pain management. These factors are complicated by physician bias about various subgroups and poor physician-patient communication. Comprehensive patient assessment plays a crucial role in determining appropriate treatment and identifying potential abuse problems. Physicians must routinely document medications analgesic effects and screen for potential ill effects and drug abuse. OBJECTIVE: To examine the prevalence of the undertreatment of pain, particularly among African Americans, and to recommend relevant proactive policy and practice changes to aid in eliminating this health problem. CONSENSUS PROCESS: In July 2002, the NMA convened the "Managing Pain: The Challenge in Underserved Populations: Appropriate Use versus Abuse and Diversion" Consensus Meeting in Washington, DC. The country's most renowned experts in the area of pain management and substance abuse reviewed substantial information regarding pain management and substance abuse including the following: --A draft summary paper on pain management and substance abuse that served as briefing material for consensus members; --Annotated bibliographies; --Articles on pain management and substance abuse; and --Key presentations on pain management and substance abuse. 相似文献
62.
63.
Influence of Malaria Infection on the Elaboration of Soluble Mediators by Adherent Mononuclear Cells 下载免费PDF全文
MALARIA RESULTS IN TWO SEEMINGLY PARADOXICAL PERTURBATIONS OF THE IMMUNE RESPONSE: polyclonal B-cell activation and immunosuppression. To determine what immunoregulatory role mediators secreted by adherent cells might play in these alterations, we cultured adherent cells from uninfected mice and from mice at different times during infection with Plasmodium berghei or P. yoelii. Culture supernatants obtained from these cells were tested for their ability to enhance the in vitro proliferative responses of thymocytes to suboptimal concentrations of concanavalin A or to inhibit the mitogen-stimulated proliferation of normal spleen cells. Supernatants obtained from adherent cells of mice early in infection (days 1 to 3) contained significantly elevated levels of enhancing activity which on Bio-Gel P-100 chromatography resembled lymphocyte-activating factor. Later in infection (days 4 and 5), these supernatants contained inhibitory activity. Normal adherent cells, when cocultivated in vitro with parasitized erythrocytes, ingested parasite debris and were stimulated to produce the enhancing factor. At high parasite/adherent-cell ratios, cells elaborated an inhibitory factor. These findings suggest that during malaria, adherent cells are converted from a nonspecific helper role to a nonspecific suppressor role. This modulation in function may be due to the direct interaction between adherent cells and parasitized erythrocytes. 相似文献
64.
The dependence of the latency relaxation on sarcomere length and other characteristics of isolated muscle fibres 总被引:3,自引:0,他引:3
Louis A. Mulieri 《The Journal of physiology》1972,223(2):333-354
1. The latency relaxation has been examined in single fibres from frog striated muscle with particular attention given to its possible relation to Ca(2+) release during excitation-contraction coupling.2. Latency relaxations were recorded at 19-23 degrees C from massively stimulated (0.2 msec pulses) single fibres using two selected RCA 5734 transducer tubes in a bridge circuit.3. The depth of the latency relaxation has its full value when stimulus strength is between 40 and 400% above twitch threshold. Stronger stimuli reversibly diminish the latency relaxation.4. The variation in depth of latency relaxation with sarcomere length was found similar to that reported previously for multifibre preparations but in single fibres the peak of the curve consists of a plateau between sarcomere lengths of 2.8 mu and 3.2 mu.5. Sucrose hypertonicity increases the depth of the latency relaxation at sarcomere lengths below 2.8 mu but above this length it has either no effect or a depressant effect depending on the degree of hypertonicity.6. The maximal depth of the latency relaxation (measured at 3 mu) averaged 0.23% of the maximal tetanus tension (measured at 2.2 mu) and was strongly correlated (r = 0.87) with the latter in forty-five single fibres.7. The maximal depth of the latency relaxation is not correlated with the number of sarcomeres in series in a fibre.8. The results of this study are shown to fully support and extend Sandow's (1966) hypothesis that the latency relaxation is caused by release of activator Ca(2+) from the sarcoplasmic reticulum. 相似文献
65.
66.
67.
Levi MH Bartell J Gandolfo L Smole SC Costa SF Weiss LM Johnson LK Osterhout G Herbst LH 《Journal of clinical microbiology》2003,41(5):2147-2152
The characterization of a novel Mycobacterium sp. isolated from granulomatous skin lesions of moray eels is reported. Analysis of the hsp65 gene, small-subunit rRNA gene, rRNA spacer region, and phenotypic characteristics demonstrate that this organism is distinct from its closest genetic match, Mycobacterium triplex, and it has been named M. montefiorense sp. nov. 相似文献
68.
Effects of Purified Staphylococcal Alpha Toxin on the Ultrastructure of Human and Rabbit Erythrocytes 总被引:2,自引:0,他引:2 下载免费PDF全文
Previous studies have suggested that the primary site of action of purified staphylococcal alpha toxin is the cell membrane. Scanning and transmission electron microscopy studies were undertaken, therefore, to define toxin-induced alterations in the surface morphology of rabbit and human red blood cells. During the prelytic lag phase, scanning electron microscopy revealed multiple discrete blisters on the surface of rabbit red blood cells; during hemolysis, cellular collapse and ghosts were seen, but most striking was the separation of large fragments of cell membrane from red blood cell surfaces. In contrast, alterations in less sensitive human red blood cells were limited to occasional fingerlike protrusions during the period of accelerated lysis. Transmission electron microscopy substantiated these changes. These studies have provided further evidence that the cell membrane is the primary site of action of staphylococcal alpha toxin. 相似文献
69.
Three classes of mutants resistant to the drug 6(p-hydroxyphenylazo)-uracil have been isolated from mutagenized cultures of CHO cells. One class of these mutants designated HPU R A exhibits a unique form of cross-resistance to bromodeoxyuridine in that it is resistant to this drug only in the presence of thymidine. The molecular basis of the BrdU resistance is unknown but does not appear to involve the known targets of the drug. An interesting feature of these mutants is that they give rise, at a high frequency, to a subpopulation of cells which are much more resistant to BrdU. 相似文献
70.
Two classes of CHO mutants resistant to the drug 6(p-hydroxyphenylazo)-uracil have been characterized. Both classes exhibited a nutritional requirement that could be satisfied by deoxypyrimidines and uridine but not other ribopyrimidines. A biochemical investigation of these mutants revealed a structural defect in ribonucleotide reductase resulting in a two- to fourfold increase in the Km for UDP and CDP. As a consequence of this lesion, the cells had imbalanced deoxypyrimidine pools and showed an increase in the rate of spontaneous mutation to 6-thioguanine resistance but not emetine resistance. 相似文献