首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2182901篇
  免费   153710篇
  国内免费   3200篇
耳鼻咽喉   31240篇
儿科学   71680篇
妇产科学   62090篇
基础医学   314472篇
口腔科学   61555篇
临床医学   189706篇
内科学   419745篇
皮肤病学   47374篇
神经病学   168115篇
特种医学   86206篇
外国民族医学   564篇
外科学   335490篇
综合类   45289篇
现状与发展   2篇
一般理论   548篇
预防医学   156808篇
眼科学   49934篇
药学   170560篇
  8篇
中国医学   4910篇
肿瘤学   123515篇
  2018年   21452篇
  2016年   18628篇
  2015年   21166篇
  2014年   28953篇
  2013年   43447篇
  2012年   59521篇
  2011年   63505篇
  2010年   37556篇
  2009年   35244篇
  2008年   60446篇
  2007年   65219篇
  2006年   66193篇
  2005年   64115篇
  2004年   61600篇
  2003年   59631篇
  2002年   58213篇
  2001年   107273篇
  2000年   110129篇
  1999年   92640篇
  1998年   24809篇
  1997年   22046篇
  1996年   22160篇
  1995年   20942篇
  1994年   19456篇
  1993年   18174篇
  1992年   72494篇
  1991年   70538篇
  1990年   69557篇
  1989年   67261篇
  1988年   61851篇
  1987年   60475篇
  1986年   57433篇
  1985年   54405篇
  1984年   40081篇
  1983年   34417篇
  1982年   19757篇
  1981年   17454篇
  1979年   37093篇
  1978年   25558篇
  1977年   22442篇
  1976年   20439篇
  1975年   22782篇
  1974年   26689篇
  1973年   25793篇
  1972年   24641篇
  1971年   23012篇
  1970年   21259篇
  1969年   20604篇
  1968年   18875篇
  1967年   16726篇
排序方式: 共有10000条查询结果,搜索用时 439 毫秒
991.
To test the reported antipanic efficacy of clonazepam, the authors randomized 72 subjects with panic disorder to 6 weeks of treatment with either alprazolam, clonazepam, or placebo. Endpoint analysis demonstrated a significant beneficial effect of both active treatments, but not placebo treatment, on the frequency of panic attacks, overall phobia ratings, and the extent of disability. Comparison of the two active treatments revealed no significant differences and no consistent tendency for one agent to be favored over another, although power to detect small differences was limited. Sedation and ataxia were the most common side effects reported, but these effects were mild and transient and did not interfere with treatment outcome. The results of this double-blind, placebo-controlled trial are consistent with previous reports of clonazepam's antipanic efficacy.  相似文献   
992.
Lithium treatment of chronic hair pulling   总被引:3,自引:0,他引:3  
Ten patients with chronic hair pulling received trials of lithium carbonate of 2 to 14 months' duration. Eight patients demonstrated decreased hair pulling and mild to marked hair regrowth. Three responders experienced increased hair pulling subsequent to discontinuation of lithium treatment. Lithium's effect on hair pulling may be related to its observed benefits in treating aggressivity, impulsivity, and mood instability.  相似文献   
993.
994.
Transneuronal degeneration of thalamic neurons following partial deafferentation was studied using [3H]thymidine autoradiography. Timed-pregnant female Sprague-Dawley rats received systemic injections of [3H]thymidine on embryonic day (E) 13, 14 and/or 15. On the day of birth, pups were anesthetized by hypothermia and subjected to unilateral enucleation, unilateral removal of the inferior colliculus or sham lesion. Animals were sacrificed on postnatal day 10 or 30 and the brains processed for autoradiography. Material from sham-lesioned animals demonstrates that neurons destined for the dorsal lateral geniculate nucleus (LGd) undergo final mitoses on E13, 14 and 15. Neurons in the ventral medial geniculate nucleus (MGv) undergo final mitoses on E13 and 14. Thirty days following neonatal unilateral eye removal, the contralateral LGd displays a loss of approximately 30-35% of [3H]thymidine labeled neurons. Neonatal unilateral removal of the inferior colliculus results in a loss of approximately 30-40% of labeled neurons in MGv. For both LGd and MGv, shorter survival times reveal less severe cell loss. Late generated (E15) LGd neurons show less severe loss following enucleation than do earlier generated neurons. These results document the degree of cell loss in sensory thalamic nuclei following deafferentation and demonstrate that [3H]thymidine autoradiography provides a useful quantitative method for assessing anterograde transneuronal cell loss in targeted populations of neurons in the developing central nervous system.  相似文献   
995.
The experimental infection of immunocompetent and immunodeficient athymic mice with an avirulent encephalitogenic Toxoplasma strain (DX strain) was employed to study the ensuing encephalitic process by use of histological and immunocytochemical methods. In the acute phase of the infection Toxoplasma cysts and tachyzoites were accompanied by an infiltrate composed of macrophages, CD4+ and CD8+ T cells. In the chronic stage a granulomatous encephalitis developed. In contrast to immunocompetent NMRI mice, athymic nude NMRI mice died 3 weeks post-infection because of a generalized toxoplasmosis with predominant involvement of the brain. A salient feature of murine Toxoplasma encephalitis was up-regulation of class I and II major histocompatibility complex (MHC) gene products. Class I antigen was widely expressed on microglial cells and astrocytes. Class II antigen was only expressed on microglial cells despite a considerable astrogliosis. Our results indicate a differential expression of MHC-determined antigens on brain cells in acute and chronic murine Toxoplasma encephalitis.  相似文献   
996.
The plasma levels of several haemostatic and fibrinolytic parameters were measured before and after delivery in 61 hypertensive pregnant women of whom 22 developed preeclampsia, and compared to the results obtained in 42 normal pregnant women. In the two last weeks before delivery (D less than or equal to -15) tPA antigen, PAI-1 activity, vWF:Ag/FVIII:C ratio, ATIII activity and platelet count were found to be significantly different in the hypertensive pregnant women with and without preeclampsia. Combined all together, an association of three of these five parameters were found to be pathological (i.e.:tPA:Ag greater than or equal to 19 ng/ml, PAI-1 activity greater than or equal to 58 IU/ml, vWF:Ag/FVIII:C ratio greater than or equal to 2.6, ATIII activity less than or equal to 73%) in none of the hypertensive women without preeclampsia and in only 35% of the preeclamptic group. A positive correlation was demonstrated between vWF:Ag/FVIII:C ratio and tPA:antigen levels suggesting that both tPA and vWF:Ag could be considered as early indicators of a possible micro angiopathy occurring in preeclampsia. However, due to the high dispersion of the results, it appears that the investigated haemostatic and/or fibrinolytic criteria give only presumptive arguments before assigning risk for preeclampsia development among hypertensive pregnant women.  相似文献   
997.
The presence of cytochrome P-45011 beta in rat brain was studied by immunohistochemistry using polyclonal rabbit antibodies raised against purified bovine adrenocortical P-45011 beta, which is involved in the steroid 11 beta-hydroxylation and glucocorticoid formation. The results showed that cytochrome P-45011 beta immunoreactivity is selectively localized to the tracts of myelinated fibers throughout the brain. The specificity of immunohistochemical stainings with P-45011 beta antibodies was established by control tests including nonimmune rabbit immunoglobulin Gs and P-45011 beta antibodies absorbed with purified antigen. Western immunoblots of homogenates from different brain areas with P-45011 beta antibodies, together with biochemical enzymatic assays for cytochrome P-45011 beta monooxygenase activity in these homogenates, confirmed the selective localization of this enzyme observed with immunohistochemistry. Cytochrome P-45011 beta and 11 beta-hydroxylase activity were detected in a homogenate from the cortical white matter (brain area rich in myelinated fibers) as in that from the rat adrenal, but were not detectable in a homogenate from the cerebral cortex (brain area poor in myelinated fibers). Furthermore, quantitation of the P-45011 beta bands on the immunoblots by the areal density revealed that the cortical white matter contains approximately 1.4 pmol of cytochrome P-45011 beta/mg of tissue protein, the value of which was about one sixth of the corresponding value estimated in the rat adrenal. This relatively high content of cytochrome P-45011 beta was also reflected in a relatively high level of 11 beta-hydroxylase activity measured in a homogenate of this brain area by biochemical enzymatic assays using [4-14C]-11-deoxycorticosterone.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
998.
We developed a novel method which enables bloodless exposure of the levator veli palatini muscle in rat in order to investigate the physiological properties of this muscle. The levator veli palatini muscle which is innervated by a branch of the glossopharyngeal nerve showed rhythmic spontaneous movement in rats. Cutting the branch supplying LVP of the glossopharyngeal nerve caused cessation of the spontaneous movement of the levator veli palatini muscle. The spontaneous discharges of the glossopharyngeal nerve were synchronized with those of the phrenic nerve. A mixture of 95% oxygen and 5% room air influenced the efferent discharges from the branch of the glossopharyngeal nerve supplying the levator veli palatini muscle. These findings indicate that the motor nerve supply to the levator veli palatini muscle is the glossopharyngeal nerve, and the levator veli palatini muscle is related to the respiratory system, in particular with inspiration in rats.  相似文献   
999.
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号